®

Transmission and Substation Foundations

Technical Design Manual
TRANSMISSION AND SUBSTATION FOUNDATIONS
TECHNICAL DESIGN MANUAL

CONTENTS

INTRODUCTION.................................................................................SECTION 1
SOIL MECHANICS............................................................................SECTION 2
PRODUCT FEASABILITY..............................................................SECTION 3
DESIGN METHODOLOGY............................................................SECTION 4
INSTALLATION METHODOLOGY.............................................SECTION 5
DRAWINGS AND RATINGS.........................................................SECTION 6
DESIGN EXAMPLES........................................................................SECTION 7

APPENDIX A - CORROSION
APPENDIX B - LOAD TESTS
APPENDIX C - HELICAL PILES AND ANCHORS
APPENDIX D - FORMS

GLOSSARY
 INTRODUCTION

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 INTRODUCTION
SECTION 1

CONTENTS

DEFINITION of HELICAL PILES/ANCHORS ................................................ 1-4

HISTORY & SCIENCE OF CHANCE® HELICAL PILES/ANCHORS..... 1-4

SYMBOLS USED IN THIS SECTION

PISA..................................................................Power Installed Screw Anchor 1-5

RR..............................................................................................................Round Rod 1-5
SS........................................................................................................... Square Shaft 1-5
HS........................................................................................................High Strength 1-6
INTRODUCTION

PIF.......................................................................... Power Installed Foundation 1-6

SLF.................................................................................Street Light Foundation 1-6
ICC-ES................................................................... ICC Evaluation Service, Inc. 1-9
kips............................................................................................................. Kilopound 1-10

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 INTRODUCTION
DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to
point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted
prior to any installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption,
revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in
its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of
CHANCE® Civil Construction foundation support products.

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 DEFINITION OF HELICAL PILES/ANCHORS
The helical pile/anchor is a deep foundation system used to support or
resist any load or application. Installed by mobile equipment ranging
in size from lightweight units to heavier units depending on the load
requirements, it can be loaded immediately. The helical pile/anchor’s
elegant simplicity is its greatest asset. Its mechanical design balances
the capacities of its three basic parts and maximizes the efficient use of
their materials.

ESSENTIAL ELEMENTS:
1. At least one bearing plate (helix)
Dies form each steel bearing plate into a true helix. The plates are
formed in a true helical shape to minimize soil disturbance during
installation (as opposed to the inclined plane of an auger which mixes
soil as it excavates). Properly formed helical plates do not measurably
disturb the soil. The helical bearing plates transfer the load to the soil
bearing stratum deep below the ground surface. Hubbell Power Sytems,
Inc. defines “deep” as five helix diameters vertically below the surface
INTRODUCTION

where the helical plate can develop full capacity of the plate-to-soil
interaction.

2. A central shaft
During installation, the central steel shaft transmits torque to the helical
plate(s). The shaft transfers the axial load to the helical plate(s) and on
to the soil bearing stratum. Theoretically, the shaft needs to be larger
than the shaft material’s allowable stress. Realistically, the shaft also
needs to be strong enough to resist the torque required for installation
and large enough in section for the soil to resist buckling, if used in a
compression application.

3. A termination
The termination connects the structure to the top of the helical pile/
anchor transferring the load down the shaft to the helical plate(s) to
the bearing soil. To evenly distribute the structure load to the helical
piles/anchors, the termination may be a manufactured bracket or an
attachment produced on site as designed by the structural engineer.
Such aspects dictate the termination’s configuration as a function of
its application and may range from a simple threaded bar to a complex
weldment, as is appropriate to interface with the structure.

HISTORY AND SCIENCE OF CHANCE® HELICAL PILES/ANCHORS

In 1833, the helical pile was originally patented as a “screw pile” by English inventor, Alexander Mitchell.
Soon after, he installed screw piles to support lighthouses in tidal basins of England. The concept also was
used for lighthouses off the coasts of Maryland, Delaware and Florida.

Innovations of the helical pile/anchor have been advanced by both its academic and commercial
advocates. Considerable research has been performed by public and private organizations to further
advance the design and analysis of helical piles and anchors. A partial list of publications related to helical
pile research is included at the end of this chapter. Much of the research was partially funded or assisted
by Hubbell Power Systems, Inc. Contributions of financial, material and engineering support for research
ventures related to helical piles is continued today by Hubbell Power Systems, Inc.

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Today, readily available hydraulic equipment, either small or large, can install helical pile/anchors almost
anywhere. Backhoes, skid-steer loaders and mini-excavators are easily fitted with hydraulically driven
torque motors to install helical pile/anchors in construction sites inaccessible by the larger equipment
required for other deep foundation methods. According to site conditions, installation equipment can
include guided-head and articulated-head torque-head machinery, self-propelled, carrier-mounted,
tracked, wheeled or floating.

The following summarizes a short list of Hubbell Power Systems, Inc. contributions to the helical pile/
anchor industry. In 1940, the A.B. Chance Company sold the first commercially offered helical anchor
tension application. It was installed by hand using a small tubular wrench. Other early developments
include soil classifying measurement devices.

• PISA® (Power Installed Screw Anchors)

In the late 1950’s, the A.B. Chance Company introduced the patented PISA® system. This coincided with the
invention of truck-mounted hole-digging equipment following World War II. The PISA® system has become
the worldwide method of choice for guying pole lines of electric and telephone utilities.

The PISA® system’s all-steel components include one or two helix plates welded to a square hub, a rod
threaded on both ends, a forged guy wire eye nut, and a special installing wrench. The square-tube anchor
wrench attaches to the kelly bar of a digger truck, fits over the rod, engages the helical hub and typically

INTRODUCTION
installs a PISA® anchor in 8 to 10 minutes. Rod and wrench extensions may be added to reach soil layers
which develop enough resistance to achieve capacity. PISA® rods come in 5/8”, 3/4” and 1” diameters.

Through A.B. Chance Company testing and close contact with utilities, the PISA® anchor family soon
expanded to develop higher strengths capable of penetrating harder soils including glacial till. This
quickly gave rise to the development of CHANCE® helical piles/anchors with higher capacities and larger
dimensions.

More recent developments include the Square One® (1980) and the Tough One® (1989) patented guy
anchor families with 10,000 and 15,000 ft-lbs installing torque capacities. Unlike previous PISA® designs,
these anchor designs are driven by a wrench that engages inside, rather than over, their welded socket
hubs. Both use the PISA® extension rods with threaded couplings.

• Round Rod (RR) Anchors

In 1961, the A.B. Chance Company developed extendable Type RR multi-helix anchors, originally for use as
tiedowns for underground pipelines in poor soil conditions on the Gulf of Mexico coast. These anchors are
not driven by a wrench; instead, installing torque is applied directly to their 1-1/4” diameter shafts. Type RR
anchors worked well in weak surficial soils, but their shaft (although extendable by plain shafts with bolted
upset couplings) did not provide enough torque strength to penetrate very far into firm bearing soils.

• Square Shaft (SS) Anchors

Development of a high-torque, shaft-driven, multi-helix anchor began in 1963, culminating in the
introduction of CHANCE® type SS 1½” square shaft multi-helix anchors in 1964-65. The SS anchor family
since has expanded to include higher-strength 1-3/4”, 2” and 2-1/4” square shafts. With the acquisition of
Atlas Systems, Inc., in 2005, the type SS product line has been expanded to include 1-1/4” square shafts.
Extension shafts with upset sockets for the 1-1/4”, 1-1/2”, 1-3/4”, 2” and 2-1/4” square shafts also lengthen
these anchors to penetrate most soils at significant depths for many civil construction applications
including guying, foundations, tiebacks and more recently, soil nails (the CHANCE Soil Screw® retention
wall system, 1997).

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 • High Strength (HS) Anchors/Piles [now called Round Shaft (RS) Piles]
Later in the 1960’s, type HS anchors developed first for high-torque guying requirements later were
applied as foundation helical piles for utility substations and transmission towers. The HS anchor family
has 3-1/2” pipe shafts which may be lengthened by extensions with swaged couplings. HS anchors now
are used for a wide array of foundation applications. The type HS Piles/Anchors are now referred to as
type RS piles/anchors. Hubbell Power Systems, Inc. now offers 2-7/8” (RS2875.203, RS2875.276), 4-1/2”
(RS4500.337), 6” (RS6625.280) and 8” (RS8625.250) pipe shafts in addition to the 3-1/2” (RS3500.300).

• Power Installed Foundation (PIF) Anchors/Piles

Also launched in the 1960’s were non-extendable anchors termed power installed foundations (PIF). PIF
sizes and load capacities support requirements for foundations that support a broad range of equipment,
platforms and field enclosures. Most versatile are the 5-ft to 10-ft-long PIFs with pipe shafts of 3-1/2”, 4”,
6-5/8”, 8-5/8” and 10-3/4” diameters, each with a single helix of 10”, 12”, 14” or 16” diameter. Integral base
plates permit direct bolt-up connections on either fixed or variable bolt-circle patterns.

Bumper post anchors are similar to the 3½”-shaft PIF, but with fence-type caps instead of base plates,
to serve as traffic barriers around booths, cabinets, doorways, etc. One with a 2-3/8” pipe shaft 69” long
is called a square drive foundation for its 2”- square drive head. The solid head is internally threaded for
adding a straight stud or adjustable leveling pad after installation.
INTRODUCTION

• Street Light Foundation (SLF) Anchors/Piles

In 1972, CHANCE® street light foundations (SLF) were introduced. Anchors with pipe shaft diameters of
6-5/8”, 8-5/8” and 10-3/4” in fixed lengths of 5, 8 and 10 feet. Complete with an internal cableway, these
foundations with bolt-up base plates deliver the quick solution their name implies and now are used to
support similar loads for a variety of applications.

• CHANCE HELICAL PULLDOWN® Micropiles

Developed in 1997, for sites with especially weak
surface soils, this patented innovative application of
the helical pile integrates portland-cement-based
grout to stiffen the shaft. By “pulling down” a special
flowable grout as the foundation is screwed into the
soil, the result is a pile with both a friction-bearing
central shaft and end-bearing helical plates in
competent substrata. Where needed for poor surface
conditions, this performance combination converts
sites previously deemed as “non-buildable” to usable
sites suited for not only building construction but
also telecom tower foundations in areas inaccessible
by equipment utilized for other deep foundation
methods. It employs SS, RS and combinations of
these two types of helical piles.

• Large Diameter Pipe Piles (LDPP)

To meet an industry need for helical piles with higher
tension/compression capacities and larger bending
resistance, the large diameter pipe pile research
project was initiated in 2007. The research culminated
in product offerings including extendable large
diameter piles with a box coupling system capable
of installation torques as high as 60,000 ft-lbs and
compression capacities of 300 kips.

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APPLIED RESEARCH AND DEVELOPMENT
In addition to products developed for specific applications, significant contributions to the applied science
of helical piles and anchors by Hubbell Power Systems, Inc. have been achieved. Among the various subjects
which have expanded the body of knowledge are:

• CHANCE® Civil Construction Soil Classification

In 1945, A.B. Chance Company listed the first earth anchoring manual, which classified soils according to
holding capacities as related to proper anchor selection. At sites where soil data was available, either by
sample excavation or some rudimentary means of probing subsurface strata, this chart imparted a valuable
basis for recommending the proper helical pile or anchor for a given load.

• Torque-to-Capacity Relationships
Installation torque-to-load capacity relationship is an empirical method that the A.B. Chance Company
originally developed in the 1960’s. The idea was that the installation energy (torque) required to install a
helical pile/anchor can be correlated to its ultimate load capacity in soil. The analogy is similar to screwing a
wood screw into a piece of wood. It takes more torsional energy to screw into dense wood, such as oak, than
it does to screw into a soft wood, such as pine. Likewise, a wood screw in oak will require more effort to pull
out than the same wood screw in pine. The same is true for helical piles/anchors in soil. Dense soil requires
more torque (more energy) to install compared to a soft soil; and likewise dense soil will generate higher load

INTRODUCTION
capacity compared to a soft soil.

CHANCE® CIVIL CONSTRUCTION SOIL CLASSIFICATION , TABLE 1-1

Typical Blow
Probe Values Count
Class Common Soil-Type Description Geological Soil Classification
in/lbs (nm) N per ASTM
D1586
0 Sound hard rock, unweathered Granite, Basalt, Massive Limestone N.A N.A
Very dense and/or cemented sands; coarse Caliche, (Nitrate-bearing gravel/ 750-1600
1 60-100+
gravel and cobbles rock) (85-181)
Dense fine sands; very hard silts and clays (may Basal till; boulder clay, caliche; 600-750
2 45-60
be preloaded) weathered laminated rock (68-85)
Glacial till; weathered shales, schist, 500-600
3 Dense sands and gravel; hard silts and clays 35-50
gniess and siltstone (56-68)
Medium dense sand and gravel; very stiff to hard 400-500
4 Glacial till; hardpan; marls 24-40
silts and clays (45-56)
Medium dense coarse sands and sandy gravels; 300-400
5 Saprolites, residual soils 14-25
stiff to very stiff silts and clays (34-45)
Loose to medium dense fine to coarse sands to Dense hydraulic fill; compacted fill; 200-300
6 7-14
stiff clays and silts residual soils (23-34)
Loose fine sands; Alluvium; loess; medium-stiff Flood plain soils; lake clays; adobe; 100-200
**7 4-8
and varied clays; fill gumbo, fill (11-23)
Peat, organic silts; inundated silts, fly ash very Flood plain soils; lake clays; adobe; less than 100
**8 0-5
loose sands, very soft to soft clays gumbo, fill (0-11)

Class 1 soils are difficult to probe consistently and the ASTM blow count may be of questionable value.

* Probe values are based on using CHANCE® Soil Test Probe, catalog number C309-0032
** It is advisable to install anchors deep enough, by the use of extensions, to penetrate a Class 5 or 6,
underlying the Class 7 or 8 Soils.

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 For the torque correlation method to work, torque must be measured.
Hubbell Power Systems, Inc. engineers have developed both
mechanical and electronic indicators over the years, many of which
are commercially available for torque measurement in the field. The
most recent addition to the product line is the C3031578 digital
torque indicator, which features a continuous reading digital readout
of installation torque up to 30,000 ft-lb. The digital torque indicator
is also available with a wireless remote display and a data logger. The
data logger records torque and other installation data that is used as a
permanent record.

• Soil Mechanics Principles

In the 1970s and early 1980s, changes in design philosophy led Hubbell
Power Systems, Inc. engineers to recognize that a deep buried plate
(i.e., pile/anchor helix) transferred load to the soil in end-bearing.
Theoretical capacity could then be calculated based on Terzaghi’s
general bearing capacity equation. The individual bearing method,
discussed in detail in Section 5, calculates the unit bearing capacity of
the soil and multiplies it by the projected area of the helix plate. The
capacity of individual helix plate(s) is then summed to obtain the total
INTRODUCTION

ultimate capacity of a helical pile/anchor. Today, the individual bearing

method is commonly used in theoretical capacity calculations and is
recognized as one method to determine helical pile capacity in the
International Building Code (IBC).

• 100+ Years of Field Test Data

Hubbell Power Systems, Inc. engineers continuously prove theory by conducting literally thousands of load
tests in the field. It has been said that soil occurs in infinite variety of engineering properties can vary widely
from place to place. This variability makes in-situ testing a vital part of sound geotechnical engineering
judgment. Test results are available from Hubbell Power Systems, Inc. for typical capacity of helical piles/
anchors in soil.

• HeliCAP® Helical Capacity Design

SoftwareHubbell Power Systems, Inc. engineers
developed HeliCAP® Helical Capacity Design
Software to assist the designer to select the
correct helical lead configuration and overall
pile/anchor length. It also estimates the
installation torque. This program makes the
selection of helical piles/anchors easier and
quicker than hand calculations. To obtain a
copy of the software, please contact your
local Hubbell Power Systems, Inc. distributor.
Contact information for each distributor can be
found at www.abchance.com.

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 • SELECT-A BASE™ Lighting Base Program
The SELECT-A BASE™ lighting base program is an on-line program
developed in 2009 by Hubbell Power Systems, Inc. engineers for
preliminary foundation selection for roadway, area and site lighting
poles and luminaires. The program incorporates a database of
CHANCE® Lighting Bases designed using more than 100 years of
research, development and testing of earth anchor systems. The
program inputs include loading conditions (wind, moment and/or
lateral), pole/pole arm details and soil data. The software is free and
easy to use on-line at www.abchance.com.

• Inter-Helix Spacing
Load transfer either above or below the helix plate results in a stress
zone within a defined soil volume. For individual bearing to work
properly, the helix plates must be spaced far enough apart to avoid
overlapping their stress zones. The key is to space the helix plates
just far enough apart to maximize the bearing capacity of a given
soil. This works to reduce the overall length of the helical pile/
anchor and increases the likelihood for all helix plates to be located
in the same soil layer; which in turn leads to more predictable torque-

INTRODUCTION
to-capacity relationships and better load/deflection characteristics.
Through years of research, the Hubbell Power Systems, Inc.
engineers determined that the optimal spacing for helix plates is
three diameters. More specifically, the optimum space between any
two helical plates on a helical pile/anchor is three times the diameter
of the lower helix. Today, all CHANCE® helical piles/anchors are
manufactured using the industry standard of three diameter spacing.

• Industry Standard: Helical Pile/Anchor Form Fits Function

The helical pile/anchor is not a complex product, but it continues to serve ever-expanding roles in utility
applications. However, you will probably not find helical piles/anchors mentioned in most foundation
engineering textbooks, and as such, familiarity with helical piles/anchors is still lacking among most civil and
structural engineers with a foundation background. This trend is slowly changing. Since the first edition of
this technical manual, helical piles are now listed as a deep foundation system in the 2009 and 2012 editions
of the International Building Code. In addition, ICC-ES Acceptance Criteria AC358 for helical systems and
devices was published in 2007 and is now on its third revision. Hubbell Power Systems, Inc. was the first
manufacturer of helical piles and anchors to obtain evaluation reports from all three model building code
agencies – ICBO, BOCA, and SBCCI. Today Hubbell Power Systems, Inc. has evaluation reports for helical
products both in the US and Canada. ESR-2794 is an ICC-ES evaluation report that demonstrates code
compliance with the IBC, and CCMC Report 13193-R is an NRC evaluation report that demonstrates Code
compliance with the Canadian Building Code. Copies of ICC-ES ESR-2794 and CCMC 13193-R evaluation
reports are available on www.abchance.com.

• Instructor’s Curriculum for Foundation Engineering Courses

In 2012, Hubbell Power Systems, Inc. contracted with Dr. Alan Lutenegger to develop an instructor’s
curriculum on helical piles and anchors to be used for foundation engineering courses for undergraduates.
The curriculum includes all the information needed for two lectures, design examples and homework. Also
included is a student guide, which serves as the “textbook” for students.

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 APPLICATIONS
In its simplest form, the helical pile/anchor is a deep
foundation element (i.e., it transfers a structure’s dead
and live loads to competent soil strata deep below grade).
This is the same for any deep foundation element such as
driven piles, drilled shafts, grouted tendons, auger-cast
piles, belled piers, etc. Therefore, helical piles/anchors
can be used as an alternative method to drilled shafts
and driven piles. Practical constraints, primarily related to
installation, currently limit the maximum design load per
helical pile/anchor to 100 kips in tension and 200 kips
in compression, which means helical piles/anchors can
resist relatively light to medium loads on a per pile/anchor
basis and much heavier loading when used in pile groups.
But as is the case with virtually all engineering problems,
more than one solution exists. It is the responsibility of the
engineer to evaluate all possible alternatives, and to select
the most cost-effective solution.
INTRODUCTION

Today, helical piles/anchors are commonly used for

residential and commercial construction. The product’s
versatility allows for application in limited and remote
access. Helical piles/anchors are a great solution for
telecommunicat and transmission towers as well as for tie
downs in windy or seismic areas. In expansive soil areas,
helical piles can save money and time when compared
to expensive over-excavation and fill options. Helical
piles/anchors do have several advantages (see following
section) that make them the foundation of choice for
many applications including these general categories:

• Machinery/Equipment Foundations

• Limited Access Sites

• Wind and Seismic Loading

• Replacement for Drilled/Driven Piles

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CHANCE® HELICAL PILE/ANCHOR ADVANTAGES TABLE 1-2
Advantages of CHANCE® Helical Pile/Anchors

• No need for concrete to cure • Install in inclement weather

• Quick, easy turnkey installation • Solution for:
• Immediate loading - Restricted access sites
• Small installation equipment - High water table
• Pre-engineered system - Weak surface soils
• Easily field modified • Environmentally friendly
• Torque-to-capacity relationship for • No vibration
production control • No spoils to remove

ADVANTAGES OF CHANCE® HELICAL PILES/ANCHORS

Each project has unique factors that determine the most acceptable foundation system. The following

INTRODUCTION
summarizes situations where helical piles/anchors present sensible solutions.

• Projects Requiring Deep Foundations due to Weak Surface Soil

Helical piles/anchors are designed as end-bearing piles which transfer loads to competent, load-bearing
strata. Helical piles/anchors eliminate high mobilization costs associated with driven piles, drilled shafts
or auger-cast piles. They also don’t require spoils to be removed and for flowable sands, soft clays and
organic soils, no casings are required, unlike drilled shafts or caissons. When using the CHANCE® HELICAL
PULLDOWN® micropiles, you have not only end-bearing capacity, but also the additional capacity from the
friction developed along the grout/soil interface.

• Flooded and/or Poor Surface Conditions

When surface conditions make spread footings impossible and equipment mobilization difficult, helical piles/
anchors are a good alternative since installation requires only a mini-excavator, a rubber-tired backhoe or
small tracked machine.

• Limited Access
In confined areas with low overhead, helical piles/anchors can be installed with portable equipment. This is
particularly useful for rehabilitation work.

• Expansive Soils
The depth of expansive soils from the surface varies, but a typical depth is approximately 10 feet. The bearing
plates of a helical pile/anchor are usually placed well below this depth. This means that only the small-cross-
section shaft of the helical pile/anchor is affected by the expansive soils. The swell force on the shaft is
directly proportional to the surface area between the soil and the shaft, and the swell adhesion value. Since
helical piles have much smaller shafts than driven piles or auger-cast piles, uplift forces on helical piles are
much smaller. Research by R.L. Hargrave and R.E. Thorsten in the Dallas area (1993) demonstrated helical
piles’ effectiveness in expansive soils.

• Inclement weather installation

Because helical piles/anchors can be installed in inclement weather, work does not need to be interrupted.

• Contaminated soils
Helical piles/anchors are ideal for contaminated soils because no spoils need to be removed.

Page 1-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 • Temporary structures
Helical piles/anchors can easily be removed by reversing the installation process. This makes removal of
temporary structures simple.

• Remedial applications
Helical piles can supplement or replace existing foundations distressed from differential settlement, cracking,
heaving, or general foundation failure. Patented products such as the CHANCE® helical pile foundation system
provide a complete solution. Hubbell Power Systems, Inc. uses patented products to attach the helical piles to
existing foundations and either stabilize the structure against further settlement or lift it back to near original
condition. This system is installed only by trained, authorized and installers.

Helical piles are ideal for remedial work since they can be installed by portable equipment in confined, interior
spaces. Additionally, there is no need to worry about heavy equipment near existing foundations. And, unlike
driven piles, helical piles are vibration-free. The building can continue to operate with little inconvenience to
its occupants. Other deep foundation systems such as auger-cast piles disturb the soil, thereby undermining
existing foundations.

BIBLIOGRAPHY OF HELICAL PILE/ANCHOR TECHNICAL LITERATURE

INTRODUCTION

Adams, J.I. and Hayes, D.C., 1967. The Uplift Capacity of Shallow Foundations. Ontario Hydro Research Quarterly, Vol. 19, No. 1, pp. 1-13.

Adams, J.I. and Klym, T.W., 1972. A Study of Anchors for Transmission Tower Foundations. Canadian Geotechnical Journal, Vol. 9, No. 1, pp. 89-104.

Black, D.R. and Pack, J.S., 2002. Design and Performance of Helical Screw Piles in Collapsible and Expansive Soils in Arid Regions of the United States.
Proceedings of the 9th International Conference on Piling and Deep Foundations, pp. 469-476.

Bobbitt, D.W., and Clemence, S.P., 1987. Helical Anchors: Application and Design Criteria. Proceedings of the 9th Southeast Asian Geotechnical Conference,
Vol. 2, pp. 6-105 - 6-120.

Bobbitt, D.E. and Thorsten, R., 1989. The Use of Helical Tieback Anchors for a Permanent Retaining

Wall. Foundation Congress, ASCE.

Bradka, T.D., 1997. Vertical Capacity of Helical Screw Anchor Piles. M.S. Report, Geotechnical Group, Department of Civil Engineering, University of Alberta.

Bustamante, M. and Gianeselli, L., 1998. Installation Parameters and Capacity of Screwed Piles. Proceedings of the 3rd International Geotechnical Seminar on
Deep Foundations on Bored and Auger Piles: BAP III, pp. 95-108.

Carville, C.A. and Walton, R.W., 1994. Design Guidelines for Screw Anchors. Proceedings of the International Conference on Design and Construction of Deep
Foundations, Vol. 2, pp. 646-655.

Carville, C.A. and Walton, R.W., 1995. Foundation Repair Using Helical Screw Anchors. Foundation Upgrading and Repair for Infrastructure Improvement,
ASCE, pp. 56-75.

Clemence, S.P., 1984. The Uplift and Bearing Capacity of Helix Anchors in Soil. Vols. 1,2 & 3, Contract Report TT112-1 Niagra Mohawk Power Corporation,
Syracuse, N.Y.

Clemence, S.P., 1994. Uplift Capacity of Helical Anchors in Soils. Proceedings of the 2nd Geotechnical Engineering Conference, Cairo, Vol. 1, pp. 332-343.

Clemence, S.P. and Pepe, F.D. Jr., 1984. Measurement of Lateral Stress Around Multi-Helix Anchors in Sand. Geotechnical Testing Journal, Vol. 7, No. 3, pp.
145-152.

Clemence, S.P. and Smithling, A.P., 1984. Dynamic Uplift Capacity of Helical Anchors in Sand. Proceedings of the 4th Australia-New Zealand Conference on
Geomechanics, Vol. 1, pp. 88-93.

Clemence, S.P., Thorsten, T.E., and Edwards, B., 1990. Helical Anchors: Overview of Application and Design. Foundation Drilling, Jan., pp. 8-12.

Clemence, S.P., Crouch, L.K., and Stephenson, R.W., 1994. Prediction of Uplift Capacity for Helical Anchors in Sand. Proceedings of the 2nd Geotechnical
Engineering Conference, Cairo.

Cox, R., 1995. Alexander Mitchell and the Screw-Pile. Centre for Civil Engineering Heritage, Trinity College, Dublin, 14 pp.

Curle, R., 1995. Screw Anchors Economically Control Pipeline Bouyancy in Muskeg. Oil and Gas Journal, Vol. 93, No. 17.

Das, B.M., 1990. Earth Anchors. Elsevier Science Publishers, Amsterdam, 241 p.

Deardorff, D. A., 2007. Torque Correlation Factors for Round Shaft Helical Piles. Deep Foundations Institute Symposium on Helical Pile Foundations, Nov.,
2007, 20 pp.

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Deardorff, D. and Luna, R, 2009. LRFD for Helical Piles: An Overview. ASCE Geotechnical Special Publication No. 185, Contemporary Topics in Deep
Foundations IFCEE09, March 2009, p. 480.

Downey, S., 2003. Helical Piles with Grouted Shafts – a Case History. Proceedings of 28th Annual Conference on Deep Foundations, Deep Foundations
Institute, pp. 291-298.

Engineering News, 1903. The Pennsylvania Railroad Tunnel Under the North River, at New York City. Oct. 15, pp. 336-341.

Engineering News, 1915. A Submerged Pump Crib Pinned Down with Screw Piles. March 18, p. 529.

Engineering News Record, 1948. Screw Piles Support Turkish Pier. Jan. 8, p. 99.

The Engineering Record, 1906. The Cienfuegos Screw Pile Pier. Jan. 20, p. 80.

Engineering Record, 1912. Steel Screw Piles, Feb. 17, p. 181.

Fabre, R., 2005. Behavior of Helical Screw Piles in Clay and Sand, M.S. Thesis, University of Massachusetts, Amherst, Ma.

Feld, J., 1953. A Historical Chapter: British Royal Engineers’ Papers on Soil Mechanics and Foundation Engineering, 1937-1974. Geotechnique, Vol.3, pp. 242-
247.

Ghaly, A.M., 1995. Drivability and Pullout Resistance of Helical Units in Saturated Sands. Soils and Foundations, Vol. 35, No. 2, pp. 61-66.

Ghaly, A.M., 1996. closure to Drivability and Pullout Resistance of Helical Units in Saturated Sands. Soils and Foundations, Vol. 36, No. 2, pp.139-141.

Ghaly, A.M. and Clemence, S.P., 1998. Pullout Performance of Inclined Helical Screw Anchors in Sand. Journal of Geotechnical and Geoenvironmental
Engineering, ASCE, Vol. 124, No. 7, pp. 617-627.

INTRODUCTION
Ghaly, A.M. and Clemence, S.P., 1999. closure to Pullout Performance of Inclined Helical Screw Anchors in Sand. Journal of Geotechnical and
Geoenvironmental Engineering, ASCE, Vol. 125, No. 12, pp. 1102-1104.

Ghaly, A.M. and Hanna, A.M., 1991. Experimental and Theoretical Studies on Installation Torque of Screw Anchors. Canadian Geotechnical Journal, Vol. 28, No.
3, pp. 353-364.

Ghaly, A.M. and Hanna, A.M., 1991. Stress Development in Sand Due To Installation and Uplifting of Screw Anchors. Proceedings of the 4th International
Conference on Piling and Deep Foundations, Vol. 1, pp. 565-570.

Ghaly, A.M. and Hanna, A.M, 1992. Stress and Strains Around Helical Screw Anchors in Sand. Soils and Foundations, Vol. 32, No. 4, pp. 27-42.

Ghaly, A.M. and Hanna, A.M., 1994. Model Investigation of the Performance of Single Anchors and Groups of Anchors. Canadian Geotechnical Journal, Vol. 31,
No. 2, pp. 273-284.

Ghaly, A.M. and Hanna, A., 1994. Ultimate Pullout Resistance of Single Vertical Anchors. Canadian Geotechnical Journal, Vol. 31, No. 5, pp. 661-672.

Ghaly, A.M. and Hanna, A., 1994. Ultimate Pullout Resistance of Groups of Vertical Anchors. Canadian Geotechnical Journal, Vol. 31, No. 5, pp. 673-682.

Ghaly, A.M. and Hanna, A., 1995. closure to Ultimate Pullout Resistance of Single Vertical Anchors. Canadian Geotechnical Journal, Vol. 32, No. 6, pp. 1093-
1094.

Ghaly, A.M. and Hanna, A., 2003. Response of Anchors to Variations in Displacement-Based Loading. Canadian Geotechnical Journal, Vol. 40, No. ?, pp. 694-
701.

Ghaly, A.M., Hanna, A.M. and Hanna, M.S., 1991. Uplift Behavior of Screw Anchors in Sand - I: Dry Sand. Journal of Geotechnical Engineering, ASCE, Vol. 117,
No. 5, pp. 773-793.

Ghaly, A.M., Hanna, A.M. and Hanna, M.S., 1991. Uplift Behavior of Screw Anchors in Sand - II: Hydrostatic and Flow Conditions. Journal of Geotechnical
Engineering, ASCE, Vol. 117, No. 5, pp. 794-808.

Ghaly, A., Hanna, A., and Hanna, M., 1991. Installation Torque of Screw Anchors in Dry Sand. Soils and Foundations, Vol. 31, No. 2, pp. 77-92.

Ghaly, A.M., Hanna, A.M. and Hanna, M.S., 1991. Uplift Behavior of Screw Anchors in Sand - I: Dry Sand. Journal of Geotechnical Engineering, ASCE, Vol. 117,
No. 5, pp. 773-793.

Ghaly, A., Hanna, A., Ranjan, G. and Hanna, M., 1991. Helical Anchors in Dry and Submerged Sand Subjected to Surcharge. Journal of Geotechnical
Engineering, ASCE, Vol. 117, No. 10, pp. 1463-1470.

Ghaly, A., Hanna, A., Ranjan, G. and Hanna, M., 1993. closure to Helical Anchors in Dry and Submerged Sand Subjected to Surcharge. Journal of Geotechnical
Engineering, ASCE, Vol. 119, No. 2, pp. 392-394.

Gunnink, Brett; Gammon, Scott; Barker, Michael; Berry, Ron, 1995. A Finite Element Approach to the Buckling Behavior of Helical Soil Piers. Journal of
Engineering Mechanics, ASCE.

Hanna, A. and Ghaly, A., 1992. Effects of Ko and Overconsolidation on Uplift Capacity. Journal of Geotechnical Engineering, ASCE, Vol. 118, No. 9, pp. 1449-
1469.

Hanna, A. and Ghaly, A., 1994. Ultimate Pullout Resistance of Groups of Vertical Anchors. Canadian Geotechnical Journal, Vol. 31, No. 5, pp. 673-682.

Hargrave, R.L. and Thorsten, R.E., 1992. Helical Piers in Expansive Soils of Dallas, Texas. Proceedings of the 7th International Conference on Expansive Soils.

Page 1-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Haskew, B.B., 1930. The Rebuilding of the Bassein Bridges on the Bombay, Baroda and Central India Railway. Minutes of the Proceedings of the Institution of Civil
Engineers, Vol. 230, pp. 204-233.

Hawkins, K. and Thorsten, R. 2009. Load Test Results-Large Diameter Helical Pipe Piles. ASCE Geotechnical Special Publication No. 185, Contemporary Topics in
Deep Foundations, IFCEE09, March 2009, p. 488.

Herrod, H., 1930. Screw-Piling, with Particular Reference to Screw-Piles Sewage Sea Outfall Works. Selected Engineering Paper No. 94, The Institution of Civil
Engineers, 23 pp.

Hovland, H.J., 1993. discussion of Helical Anchors in Dry and Submerged Sand Subjected to Surcharge. Journal of Geotechnical Engineering, ASCE, Vol. 119, No. 2,
pp. 391-392.

Hoyt, R.M. and Clemence, S.P., 1989. Uplift Capacity of Helical Anchors in Soil. Proceedings of the 12th International Conference on Soil Mechanics and Foundation
Engineering, Vol. 2, pp. 1019-1022.

Hoyt, R.M., Seider, G., Reese, L.C., and Wang, S.T., 1995. Buckling of Helical Anchors Used for Underpinning. Foundation Upgrading and Repair for Infrastructure
Improvement, ASCE, pp. 89-108.

Huang, F.C., Mohmood, I., Joolazadeh, M., and Axten, G.W., 1995. Design Considerations and Field Load Tests of a Helical Anchoring System for Foundation
Renovation. Foundation Upgrading and Repair for Infrastructure Improvement, ASCE, pp. 76-88.

Jacobs, C.M., 1910. The New York Tunnel Extension of the Pennsylvania Railroad. Transactions of the American Society of Civil Engineers, Vol. 68, pp. 40-56.

Jennings, R. and Bobbitt, D., 2003. Helical Pulldown Micropiles Support Museum Celebrating the Bicentennial of the Lewis and Clark Expedition. Proceedings of
28th Annual Conference on Deep Foundations, DFI, pp. 285-290.

Johnston, G. H. and Ladanyi, B., 1974. Field Tests of Deep Power-Installed Screw Anchors in Permafrost. Canadian Geotechnical Journal, Vol. 11, No. 3, pp. 348-358.
INTRODUCTION

Johnston, R.J., Swanston, D.N. Baxandall, F.W., 1999. Helical Piling Foundations in Juneau, Alaska. Cold Regions Engineering: Putting Research into Practice 1999.

Khatri, D. and Stringer, S., 2003. Helical Pile Foundation Anchors as a Practical Alternative. Proceedings of 28th Annual Conference on Deep Foundations, DFI, pp.
299-308.

Klosky, J.L., Sture, S., Hon-Yim Ko, H.Y. and Barnes, F., 1998. Helical Anchors for Combined Anchoring and Soil Testing in Lunar Operations. Space 98 ASCE.

Kennedy, D., 1930. Construction of Screw-Pile Jetty at Bhavnagar. Selected Engineering Paper No. 95, The Institution of Civil Engineers, 13 pp.

Khatri, D. and Stringer, S., 2003. Helical Pile Foundation Anchors as a Practical Alternative. Proceedings of 28th Annual Conference on Deep Foundations, DFI, pp.
299-308.

Klym, T.W., Radhakrishna, H.S., and Howard, K., 19??. Helical Plate Anchors for Tower Foundations. Proceedings of the 25th Canadian Geotechnical Conference, pp.
141-159.

Kraft, D.C., Davis, J. And Raaf, D.B., 2003. Use of Helical Piles Set into Soft Rock for 1500-Ton Screw Press Foundation. Proceedings of 28th Annual Conference on
Deep Foundations, DFI, pp. 209-218.

Kumar, J., 1995. discussion of Ultimate Pullout Resistance of Single Vertical Anchors. Canadian Geotechnical Journal, Vol. 32, No. 6, p. 1093.

Levesque, C.L., Wheaton, D.E. and Valsangkar, A.J., 2003. Centrifuge Modeling of Helical Anchors in Sand. Proceedings of the 12th Panamerican Conference on Soil
Mechanics and Foundation Engineering, Vol. 2, pp. 1859-1863.

Liu, H., Zubeck, H., and Baginski, S., 1999. Evaluation of Helical Piers in Frozen Ground. Cold Regions Engineering: Putting Research into Practice 1999.

Livneh, B. and El Naggar, M.H., 2007. Axial Load Testing and Numerical Modeling of Square Shaft Helical Piles. Canadian Geotechnical Journal.

Lutenegger, A.J., Smith, B.L. and Kabir, M.G., 1988. Use of In Situ Tests to Predict Uplift Performance of Multi-Helix Anchors. Special Topics in Foundations, ASCE,
pp. 93-110.

Lutenegger, A.J. and Kempker, J.H., 2008. Preservation of Historic Structures Using Screw-Pile Foundations. Proceedings of the 6th International Conference on
Structural Analysis of Historic Constructions, Vol. 2, pp 1079-1086.

Lutenegger, A.J. and Kempker, J.H., April 2009. History Repeats, Screw Piles Come of Age – Again, Structural Engineer Magazine.

Lutenegger, A.J., 2008. Tension Tests on Single-Helix Screw-Piles in Clay. Proceedings of the 2nd British Geotechnical Association International Conference on
Foundations, Dundee, Scotland.

Lutenegger, A.J., 2009. Cylindrical Shear of Plate bearing? – Uplift Behavior of Multi-Helix Screw Anchors in Clay.

Lutenegger, A.J., 2010. Using Helical Screw-Piles for Upgrading Existing Foundations for Urban Regeneration.

Lutenegger, A.J., September 2010. Shaft Resistance of Grouted Helical Micropiles in Clay. Proceedings of the International Workshop on Micropiles, Washington,
D.C.

Lutenegger, A.J., January 2011. Historical Development of Iron Screw-Pile Foundations: 1836-1900. International Journal for the History of Eng. & Tech., Vol. 81, No.
1, pp. 108-128.

Lutenegger, A.J., June 2011. Behavior of Grouted Shaft Helical Anchors in Clay. DFI Journal, Vol. 5, No. 5.

Page 1-14 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Lutenegger, A.J., November 2012. Discussion of “Ultimate Uplift Capacity of Multiplate Helical Type Anchors in Clay” by R.S. Merifield, Journal of
Geotechnical and Geoenvironmental Engineering, ASCE.

McDonald, J.K., 1999. discussion of Pullout Performance of Inclined Helical Screw Anchors in Sand. Journal of Geotechnical and Geoenvironmental
Engineering, ASCE, Vol. 125, No. 12, p. 1102.

Mitsch, M.P. and Clemence, S.P., 1985. The Uplift Capacity of Helix Anchors and Sand. Uplift Behavior of Anchor Foundations in Soil, ASCE, pp. 26-47.

Mooney, J.S., Adamczak, S.Jr., and Clemence, S.P., 1985. Uplift Capacity of Helix Anchors in Clay and Silt. Uplift Behavior of Anchor Foundations in Soil,
ASCE, pp. 48-72.

Morgan, H.D., 1944. The Design of Wharves on Soft Ground. Journal of the Institution of Civil Engineers, Vol. 22, pp. 5-25.

(discussions by F.E. Wentworth-Shields, C.W. Knight, F.M.G. Du-Plat-Taylor, J.S. Wilson, L.F. Cooling, S. Packshaw, A.W. Skempton, G.P. Manning, J. Bickley,
J.E.G. Palmer, and L.Turner, pp. 25-45.)

Muiden, M.A., 1926. Screw-Pile Mooring-Berths. Selected Engineering Papers No. 37, The Institution of Civil Engineers, 14 pp.

Narasimha Rao, .S., Prasad, Y.V.S.N., Shetty, M.D. and Joshi, V.V., 1989. Uplift Capacity of Screw Pile Anchors. Geotechnical Engineering, Vol. 20, No. 2, pp.
139-159.

Narasimha Rao, S., Prasad, Y.V.S.N., and Prasad, C.V., 1990. Experimental Studies on Model Screw Pile Anchors. Proceedings of the Indian Geotechnical
Conference, Bombay, pp. 465-468.

Narasimha Rao, S., Prasad, Y.V.S.N. and Shetty, M.D., 1991. The Behavior of Model Screw Piles in Cohesive Soils. Soil and Foundations, Vol. 31, No. 2, pp. 35-50.

Narasimha Rao, S. and Prasad, Y.V.S.N., 1993. Estimation of Uplift Capacity of Helical Anchors in Clays. Journal of Geotechnical Engineering, ASCE, Vol. 119,
No. 2, pp. 352-357.

INTRODUCTION
Narasimha Rao, S., Prasad, Y.V.S.N. and Veeresh, C., 1993. Behavior of Embedded Model Screw Anchors in Soft Clays. Geotechnique, Vol. 43, No. 4, pp. 605-
614.

Narasimha Rao, S. and Prasad, Y.V.S.N., 1992. discussion of Uplift Behavior of Screw Anchors in Sand. I: Dry Sand. Journal of Geotechnical Engineering, ASCE,
Vol. 118, No. 9, pp. 1474-1476.

Nasr. M.H., 2004. Large Capacity Screw Piles. Proceedings of the International Conference on Future Vision and Challenges for Urban Development, Cairo,
Egypt,.

Pack, J.S., 2000. Design of Helical Piles for Heavily Loaded Structures. New Technological and Design Developments in Deep Foundations, ASCE, pp. 353-
367.

Pack, J.S., 2003. Helical Foundation and Tiebacks: Quality Control, Inspection and Performance Monitoring. Proceedings of 28th Annual Conference on Deep
Foundations, DFI, pp. 269 - 284.

Pack, J.S. and McNeill, K.M., 2003. Square Shaft Helical Screw Piles in Expansive Clay Areas. Proceedings of the 12th Panamerican Conference on Soil
Mechanics and Foundation Engineering, Vol. 2, pp. 1825-1832.

Perko, H.A., 2000. Energy Method for Predicting the Installation Torque of Helical Foundations and Anchors. New Technological and Design Developments
in Deep Foundations, ASCE, pp. 342-352.

Perko, H.A., 2003. Lateral Capacity and Buckling Resistance of Helix Foundations. Foundations Technology Seminar, DFI, University of Cincinnati.

Perko, H.A., 2004. Introduction to Corrosion and Galvanizing of Helix Foundations. Deep Foundations Institute Specialty Seminar on Helical Foundations and
Tiebacks, Tampa, Florida, 7 pp.

Prasad, Y.V.S.N. and Narasimha Rao, S., 1994. Pullout Behavior of Model Piles and Helical Pile Anchors Subjected to Lateral Cyclic Loading. Canadian
Geotechnical Journal, Vol. 31, No. 1, pp. 110-119.

Prasad, Y.V.S.N. and Narasimha Rao, S., 1996. Lateral Capacity of Helical Piles in Clays. Journal of Geotechnical Engineering, ASCE, Vol. 122, No. 11, pp. 938-941.

Prasad, Y.V.S.N., 1996. discussion of Drivability and Pullout Resistance of Helical Units in Saturated Sands. Soils and Foundations, Vol. 36, No. 2, p. 139.

Puri, V.K., Stephenson, R.W., Dziedzic, E. and Goen, L., 1984. Helical Anchor Piles Under Lateral Loading. ASTM STP 835, pp. 194-213.

Rabeler, R.C., 1989. Soil Corrosion Evaluation of Screw Anchors. ASTM STP 1013, pp.

Radhakrishna, H.S., 1975. Helix Anchor Tests in Stiff Fissured Clay. Ontario Hydro Research Division Research Report.

Radhakrishna, H.S., 1976. Helix Anchor Tests in Sand. Ontario Hydro Research Division Research Report 76-130-K, pp. 1-33.

Robinson, K.E. and Taylor, H., 1969. Selection and Performance of Anchors for Guyed Transmission Towers. Canadian Geotechnical Journal, Vol. 6, pp. 119-135.

Rodgers, T.E. Jr., 1987. High Capacity Multi-Helix Screw Anchors for Transmission Line Foundations. Foundation for Transmission Line Towers, ASCE, pp. 81-
95.

Rupiper, S. and Edwards, W.G., 1989. Helical Bearing Plate Foundations for Underpinning. Foundation Engineering: Current Principles and Practices, ASCE,
Vol. 1, pp. 221-230.

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 Rupiper, S., 1994. Helical Plate Bearing Members, A Practical Solution to Deep Foundations. Proceedings of the International Conference on the Design and
Construction of Deep Foundations, Vol. 2, pp. 980-991.

Scientific American, 1904. Driving a Test Pile for the Hudson River Tunnel. April 23, p. 324.

Schmidt, R. and Nasr, M., 2004. Screw Piles: Uses and Considerations. Structure Magazine, June, pp. 29-

Seider, G.L., 1993. Eccentric Loading of Helical Piers for Underpinning. Proceedings of the 3rd International Conference on Case Histories in Geotechnical
Engineering, Vol. 1, pp. 139-145.

Seider, G. L., 2000. Versatile Steel Screw Anchors. Structural Engineer, March.

Seider, G. L., 2004. Helical Foundations: What the Engineer Needs to Know. Structure Magazine, June, pp. 27-28.

Seider, G.L. and Smith, W.P., 1995. Helical Tieback Anchors Help Reconstruct Failed Sheet Pile Wall. Proceedings of the 45th Highway Geology Symposium,
Charleston, W,V.

Seider. G.L., Thorsten, R. E., and Clemence, S.P., 2003. Helical Piles with Grouted Shafts – A Practical Overview. Proceedings of 28th Annual Conference on
Deep Foundations, DFI, pp. 219-232.

Shaheen, W.A., 1985. The Behavior of Helical Anchors in Soil. M.S. Thesis, Department of Civil Engineering, University of Massachusetts, Amherst, Ma.

Shaheen, W.A. and Demars, K.R., 1995. Interaction of Multiple Helical Earth Anchors Embedded in Granular Soil. Marine Georesources and Geotechnology,
Vol. 13, pp. 357-374. Tench, R., 1944. Cast Iron Piles Screw-Driven to Rock. Engineering News-Record, December 28, pp. 60-61.

Trofimenkov, J.G. and Maruipolshii, L.G., 1964. Screw Piles as Foundations of Supports and Towers of Transmission Lines. Soil Mechanics and Foundation
Engineering, (Osnovaniya Fundamenty I Mekhanika Gruntov), Vol. 1, No. 4, pp. 232-239.
INTRODUCTION

Trofimenkov, J.G. and Maruipolshii, L.G., 1965. Screw Piles Used for Mast and Tower Foundations. Proceedings of the 6th International Conference on Soil
Mechanics and Foundation Engineering, Vol. 2, pp. 328-332.

Udwari, J.J, Rodgers, T.E., and Singh, H., 1979. A Rational Approach to the Design of High Capacity Multi-Helix Screw Anchors. Proceedings of the 7th Annual
IEEE/PES, Transmission and Distribution Exposition, pp. 606-610.

Vickars, R.A. and Clemence, S.P., 2000. Performance of Helical Piles with Grouted Shafts. New Technological and Design Developments in Deep Foundations,
ASCE, pp. 327-341.

Weech, C.N., 2002. Installation and Testing of Helical Piles in a Sensitive Fine-Grained Soil. M.S. Thesis, Dept. Of Civil Engineering, University of British
Columbia.

Weikart, A.M. and Clemence, S.P., 1987. Helix Anchor Foundations - Two Case Histories. Foundations for Transmission Line Towers, ASCE, pp. 72-80.

White, B.G., 1949. The Construction of Military Ports in Gareloch and Loch Ryan. Civil Engineering and Public Works Review, Vol. 44, No. 514, pp. 212-216.

Wilson, G., 1950. The Bearing Capacity of Screw Piles and Screwcrete Cylinders. Journal of the Institution of Civil Engineers – London, Vol. 34, No. 5, pp. 4-73.

(discussions by H.D. Morgan, A.W. Skempton, J. Bickley, C.C. Marshall, G.G. Meyerhof, P.A. Scott, D.H. Little, N.S. Boulton, and G. Wood, pp. 74-93. also
discussions by A.S.E. Ackermann, F.L. Cassel, W.T. Marshall, P.W. Rowe, G.P. Tschebotarioff, R.J.C. Tweed, R. Pavry, R.E. Gibson, and A.A. Yassin, Journal of the
Institution of Civil Engineers-London, Vol. 34, pp. 374-386.)

Yokel, F.Y., Chung, R.M., and Yancey, C.W.C., 1981. NBS Studies of Mobil Home Foundations. U.S. National Bureau of Standards Report NBSIR 81-2238.

Zhang, D. J. Y., 1999. Predicting Capacity of Helical Screw Piles in Alberta Soils. M.S. Thesis University of Alberta, Edmonton, Canada.

Zubeck, H. and Liu, H. 2000. Helical Piers in Frozen Ground. Proceedings of the 3rd International Workshop on Micropiles, Turku Finland, Tampre University
of Technology, Geotechnical Laboratory Publication No. 4

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 SOIL MECHANICS

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 REVIEW OF SOIL MECHANICS, SOIL BEHAVIOR
& GEOTECHNICAL SITE INVESTIGATIONS
SECTION 2

CONTENTS
INTRODUCTION............................................................................................. 2-4
SOIL MECHANICS.......................................................................................... 2-4
SITE INVESTIGATIONS................................................................................ 2-13

SYMBOLS USED IN THIS SECTION

wn......................................................................................Moisture Content 2-6

M.................................................................................................................Mass 2-5
SOIL MECHANICS

V........................................................................................................... Volume 2-6

S................................................................................. Degree of Saturation 2-6
e.......................................................................................................Void Ratio 2-6
n...........................................................................................................Porosity 2-6
γd............................................................ Dry Unit Weight (Dry Density) 2-6
γt.............................................Wet (Total) Unit Weight (Wet Density) 2-6
USCS................................................Unified Soil Classification System 2-6
γs.................................... Saturated Unit Weight (Saturated Density) 2-6
SL......................................................................................... Shrinkage Limit 2-7
PL................................................................................................ Plastic Limit 2-7
LL.................................................................................................Liquid Limit 2-7
PI............................................................................................ Plasticity Index 2-7
L.I. ..........................................................................................Liquidity Index 2-7
St............................................................................................. Soil Sensitivity 2-8
Kt..................................... Torque Multiplier for Helical Piles/Anchors 2-8
σ`........................................................................................... Effective Stress 2-11
σ.................................................................................................... Total Stress 2-11
u.................................................................................. Pore Water Pressure 2-11
c.........................................................................................................Cohesion 2-11

Page 2-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 su...................................................................... Undrained Shear Strength 2-11
τf............................................................................................. Shear Strength 2-12
φ...............................................................................................Friction Angle 2-12
GWT........................................................................... Ground Water Table 2-13
CFA ................................................................... Continuous Flight Auger 2-15
HSA.............................................................................. Hollow Stem Auger 2-15
SPT.................................................................. Standard Penetration Test 2-16
ST................................................................................................Shelby Tube 2-16
SS................................................................................................. Split Spoon 2-17
N.............Field Blowcount Value from Standard Penetration Test 2-17
DMT................................................................................... Dilatometer Test 2-18
CPT......................................................................... Cone Penetration Test 2-18

SOIL MECHANICS
CPTU............................................................Piezocone Penetration Test 2-18
FVT....................................................................................... Field Vane Test 2-19
VST..................................................................................... Vane Shear Test 2-19
RQD................................................................ Rock Quality Desigination 2-20
qu.................................................... Unconfined Compressive Strength 2-22
UC........................................................... Unconfined Compression Test 2-22

DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to
point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted
prior to any installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption,
revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in
its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of
CHANCE® Civil Construction foundation support products.

Page 2-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 INTRODUCTION
The use of manufactured steel foundation products generally requires a prior geotechnical investigation of the
subsurface condition of the foundation soils at the site of a proposed project. In addition to the geotechnical
investigation, it is necessary to define the structural load requirements and required Factor of Safety (FS) for
use in the overall design approach.
• CHANCE® helical piles are utilized for communication towers, transmission and distribution power lines,
signs and light standards and commercial buildings subject to wind and earthquake load.

SOIL MECHANICS
Terzaghi stated in his book Theoretical Soil Mechanics (1943): “the theories of soil mechanics provide us
only with a working hypothesis, because our knowledge of the average physical properties of the subsoil
and of the orientation of the boundaries between the individual strata is always incomplete and often utterly
inadequate. Nevertheless, from a practical point of view, the working hypothesis furnished by soil mechanics
is as useful as the theory of structures in other branches of civil engineering.”
Advance planning and careful observation by the engineer during the construction process can help fill the
gaps between working hypothesis and fact. The intent of this section of the design manual is to provide a
basic background or review of soil mechanics so the engineer can develop a useful “working hypothesis” for
SOIL MECHANICS

the design and use of CHANCE® helical piles.

THE SOIL PROFILE

Rock or soil material, derived by geologic processes, are subject to physical and chemical changes brought
about by the climate and other factors prevalent at the location of the rock or soil material. Vegetation,
rainfall, freeze/thaw cycles, drought, erosion, leaching and other natural processes result in gradual but
profound changes in the character of the soil over the passage of time. These processes bring about the soil
profile.
The soil profile is a natural succession of zones or strata below the ground surface. It may extend to various
depths, and each stratum may have various thicknesses. The upper layer of the profile is typically rich in
organic plant and animal residues mixed with a given mineral-based soil. Soil layers below the topsoil can
usually be distinguished by a contrast in color and degree of weathering. The physical properties of each layer
usually differ from each other. Topsoil is seldom used for construction. Figure 2-1 shows a typical generalized
soil profile.
Deeper layers will have varying suitability depending on their properties and location. It is important to relate
engineering properties to individual soil layers in order for the data to be meaningful. If data from several
layers of varying strength are averaged, the result can be misleading and meaningless. Equally misleading is
the practice of factoring a given soil’s engineering properties for design. This can lead to overly conservative
foundation design.

DEFINITION OF SOIL
Soil is defined as sediments or other accumulation of mineral particles produced by the physical or chemical
disintegration of rock, plus the air, water, organic matter, and other substances that may be included. Soil is
typically a non-homogeneous, porous, earthen material whose engineering behavior is influenced by changes
in composition, moisture content, degree of saturation, density, and stress history.

The origin of soil can be broken down to two basic types: residual and transported. Residual soil is produced
by the in-place weathering (decomposition) of rock by chemical or physical action. Residual soils may be very
thick in areas of intense weathering such as the tropics, or they may be thin or absent in areas of rapid erosion
such as steep slopes. Residual soils are usually clayey or silty, and their properties are related to climate and
other factors prevalent at the location of the soil. Residual soils are usually preferred to support foundations,
as they tend to have better and more predictable engineering properties.

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Transported or deposited soils are derived
by the movement of soil from one location to
another location by natural means. The means
are generally wind, water, ice and gravity. The
character of the resulting deposit often reflects
the modes of transportation and deposition and
the source material. Deposits by water include
alluvial floodplains, coastal plains and beaches.
Deposits by wind include sand dunes and loess.
Deposits by melting ice include glacial till and
outwash. Each of these materials has behavioral
characteristics dependent on geological origin and
the geological name, such as loess, conveys much
useful information. Transported soils – particularly
by wind or water – can be of poor quality in terms
of engineering properties.

A soil mass is a porous material containing solid

particles interspersed with pores or voids. These
voids may be filled with air, water, or both. Figure
2-2 shows a conceptual block diagram of relative

SOIL MECHANICS
volumes of air, water, and soil solids in a given
volume of soil. Pertinent volumes are indicated
by symbols to the left while weights of these
material volumes are indicated by symbols to
the right. Figure 2-2 also provides several terms
used to define the relative amounts of soil, air, and
water in a soil mass. Density is the mass of a unit
volume of soil. It is more correctly termed the unit
weight. Density may be expressed either as a wet
density (including both soil and water) or as a dry
density (soil only). Moisture content is the ratio
of the weight of water to the weight of soil solids
expressed at a percent. Porosity is the ratio of the
volume of voids to the total volume of the soil mass Generalized Soil Profile
regardless of the amount of air or water contained Figure 2-1
in the voids. Void ratio is the ratio of the volume of
voids to the volume of solids.

The porosity and void ratio of a soil depend upon the degree of compaction or consolidation. For a particular
soil in different conditions, the porosity and void ratio will vary and can be used to judge relative stability and
load-carrying capacity – i.e., stability and load capacity increase as porosity and void ratio decrease. If water
fills all the voids in a soil mass, the soil is said to be saturated, i.e., S = 100%.

Permeability or hydraulic conductivity is the property of soil that allows it to transmit water. Its value depends
largely on the size and number of the void spaces, which in turn depends on the size, shape, and state of
packing of the soil grains. A clay soil can have the same void ratio and unit weight as a sand soil, but the clay
will have a lower permeability because of the much smaller pores or flow channels in the soil structure. Water
drains slowly from fine-grained soils like clays. As the pore water drains, clays creep, or consolidate slowly
over time. Sands have high permeability, thus pore water will drain quickly. As a result, sands will creep, or
consolidate quickly when loaded until the water drains. After drainage, the creep reduces significantly.

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 BASIC SOIL TYPES
As stated above, soil is typically
a non-homogeneous material.
The solid mineral particles in
soils vary widely in size, shape,
mineralogical composition, and
surface-chemical characteristics.
This solid portion of the soil
mass is often referred to as the
soil skeleton, and the pattern of
arrangement of the individual
particles is called the soil
structure.

The sizes of soil particles and the

distribution of sizes throughout
the soil mass are important
factors which influence soil
properties and performance.
SOIL MECHANICS

There are two basic soil types

that are defined by particle size.
The first type is coarse-grained
soils. Coarse-grained soils are
defined as soil that have 50% or
more particles retained by the
Soil Phases and Index Properties #200 sieve (0.074 mm). The
Figure 2-2 #200 sieve has 200 openings per
inch.

Coarse-grained soils consist of cobbles, gravels, and sands. Coarse-grained soils are sometimes referred to
as granular or cohesionless soils. The particles of cohesionless soils typically do not stick together
except in the presence of moisture, whose surface tension tends to hold particles together. This is
commonly referred to as apparent cohesion.

The second type of soil is fine-grained soil. Fine-grained soils consist of soils in which 50% or more of the
particles are small enough to pass through the #200 sieve. Typical Fine-Grained soils are silts and clays.
Silt particles typically range from 0.074 to 0.002 mm. Clay particles are less than 0.002 mm. It is not
uncommon for clay particles to be less than 0.001 mm (colloidal size). Fine-grained soils are sometimes
referred to as cohesive soils. The particles of cohesive soils tend to stick together due to molecular
attraction.

For convenience in expressing the size characteristics of the various soil fractions, a number of particle-
size classifications have been proposed by different agencies. Table 2-1 shows the category of various soil
particles as proposed by the Unified Soil Classification System (USCS), which has gained wide recognition.

An effective way to present particle size data is to use grain-size distribution curves such as shown in
Figure 2-3. Such curves are drawn on a semi-logarithmic scale, with the percentages finer than the grain
size shown as the ordinate on the arithmetic scale. The shape of such curves shows at a glance the general
grading characteristics of soil. For example, the dark line on Figure 2-3 represents a “well-graded” soil –
with particles in a wide range. Well-graded soils consist of particles that fall into a broad range of sizes
class, i.e., gravel, sand, silt-size, clay-size, and colloidal-size.

Page 2-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
SOIL PARTICLE SIZES, TABLE 2-1
FAMILIAR
PARTICLE SIZE TERM FRACTION SIEVE SIZE DIAMETER
REFERENCE

Boulders --- 12” Plus 300 mm Plus Volleyball

Cobbles --- 3”-12” 75 - 300 mm Baseball

Coarse 0.75”- 3” 19 - 75 mm
Gravels Marbles & Peas
Fine No. 4 - 0.75” 4.76 - 19 mm
Coarse No. 10 - No. 4 2 - 4.76 mm Rock Salt, Table
Sand Medium No. 40 - No. 10 0.42 - 2 mm Salt,
Fine No. 200 - No. 40 0.074 - .042 mm Sugar
Fines (silts and clays) --- Passing No. 200 0.074 mm Flour

SOIL CONSISTENCY STATES AND INDEX PROPERTIES

The consistency of fine-grained soils can range from a dry solid condition to a liquid form with successive
addition of water and mixing as necessary to expand pore space for acceptance of water. The consistency
passes from solid to semi-solid to plastic solid to viscous liquid as shown in Figure 2-4. In 1911, Atterberg, a

SOIL MECHANICS
Swedish soil scientist, defined moisture contents representing limits dividing the various states of consistency.
These limits are known as Atterberg Limits. The shrinkage limit (SL) separates solid from semisolid behavior,
the plastic limit (PL) separates semisolid from plastic behavior, and the liquid limit (LL) separates plastic from
liquid state. Soils with water content above the liquid limit behave as a viscous liquid.

The width of the plastic state (LL-PL), in terms of moisture content, is defined as the plasticity index (PI). The
PI is an important indicator of the plastic behavior a soil will exhibit. The Casagrande Plasticity Chart, shown
in Figure 2-5, is a good indicator of the differences in plasticity that different fine-grained soils can have.
The softness of saturated clay can be expressed numerically by the liquidity index (L.I.) defined as L.I. = (wn
–P.L.)/(L.L.-P.L). Liquidity Index is a very useful parameter to evaluate the state of natural fine-grained soils
and only requires measurement
of the natural water content, the
Liquid Limit and the Plastic Limit.
Atterberg limits can be used as
an approximate indicator of stress
history of a given soil. Values of L.I.
greater than or equal to one are
indicative of very soft sensitive soils.
In other words, the soil structure
may be converted into a viscous
fluid when disturbed or remolded
by pile driving, caisson drilling, or
the installation of CHANCE® helical
piles/anchors.

If the moisture content (wn) of

saturated clay is approximately
the same as the L.L. (L.I. = 1.0),
the soil is probably near normally
consolidated. This typically results
in an empirical torque multiplier
for helical piles/anchors (Kt) = 10. If
Typical Grain Size Distribution Curves the wn of saturated clay is greater
Figure 2-3 than the L.L. (L.I. > 1.0), the soil is on
the verge of being a viscous liquid

Page 2-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 and Kt will be less than 10. If the wn of
saturated clay is close to the P.L. (L.I. = 0),
the soil is dry and overconsolidated and
Kt typically ranges between 12 and 14. If
the wn of a saturated clay is intermediate
(between the PL and LL), the soil is
probably over consolidated and Kt will be
above 10. Many natural fine-grained soils
are over consolidated, or have a history
of having been loaded to a pressure
higher than exists today. Some common
causes are desiccation, the removal of
overburden through geological erosion, or
melting of overriding glacial ice.

Clays lying at shallow depth and

above the water table often exhibit
overconsolidated behavior known
Plasticity and Atterberg Limits as desiccation. They behave as
Figure 2-4 overconsolidated, but the overburden
SOIL MECHANICS

pressure required has never existed in the

soil. Desiccated clays are caused by an
equivalent internal tension resulting from
moisture evaporation. This is sometimes
referred to as negative pore pressure. The
problems with desiccated or partly dry
expansive clay are predicting the amount
of potential expansion and the expansion
or swell pressure so that preventive
measures can be taken.

Sensitivity of fine grained soils is

defined as the ratio of the undrained
shear strength of a saturated soil in
the undisturbed state to that of the
soil in the remolded state St = suund/
surem. Most clays are sensitive to some
degree, but highly sensitive soils cannot
be counted on for shear strength after
a CHANCE® helical pile, drilled shaft,
Figure 2-5 driven pile, etc. has passed through it.
Some soils are “insensitive”, that is, the
remolded strength is about the same as
the undisturbed strength. Highly sensitive soils include marine deposited in a salt water environment and
subsequently subjected to flushing by fresh water. Typical values of soil sensitivity are shown in Table 2-2.

ENGINEERING SOIL CLASSIFICATION

The engineering soil classification commonly used by geotechnical engineers is the Unified Soil Classification
System (USCS). The unified system incorporates the textural characteristics of the soil into engineering
classification and utilizes results of laboratory grain-size data and Atterberg Limits shown in Table 2-1.
The basics of the system are shown in Table 2-4. All soils are classified into 15 groups, each group being
designated by two letters. These letters are abbreviations of certain soil characteristics as shown in Table 2-3.

Page 2-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
SENSITIVITY OF SOILS, TABLE 2-2
Soil TYPE Description Sensitivity
Overconsolidated, Low to Medium
Insensitive 1-3
Plastic Clays & Silty Clays
Normally Consolidated, Medium Plastic Clays Medium Sensitivity 4-8
Marine Clays Highly Sensitive 10-80

USCS SOIL GROUP SYMBOL CHARACTERISTICS, TABLE 2-3

1st Symbol 2nd Symbol
G Gravel O Organic
S Sand W Well Graded
M Non-plastic or Low Plasticity Fines P Poorly Graded
C Plastic Fines L Low Liquid Limit
Pt Peat, Humus, Swamp Soils H High Liquid Limit

SOIL MECHANICS
COARSE-GRAINED SOILS (G & S)
GW and SW groups comprise well-graded gravely and sandy soils that contain less than 5% of non-plastic
fines passing the #200 sieve. GP and SP groups comprise poorly graded gravels and sands containing less
than 5% of non-plastic fines. GM and SM groups generally include gravels or sands that contain more than
12% of fines having little or no plasticity. GC and SC groups comprise gravelly or sandy soils with more than
12% of fines, which exhibit either low or high plasticity.

FINE-GRAINED SOILS (M & C)

ML and MH groups include the predominately silty materials and micaceous or diatomaceous soils. An
arbitrary division between the two groups is where the liquid limit is 50. CL and CH groups comprise clays
with low (L.L. < 50)and high (L.L. > 50) liquid limits, respectively. They are primarily inorganic clays. Low
plasticity clays are classified as CL and are usually lean clays, sandy clays, or silty clays. Medium-plasticity
and high plasticity clays are classified as CH.

ORGANIC SOILS (O & Pt)

OL and OH groups are characterized by the presence of organic matter, including organic silts and clays. The
Pt group is highly organic soils that are very compressible and have undesirable construction characteristics.
Peat, humus, and swamp soils with a highly organic texture are typical.

Classification of a soil in the United Soil Classification System will require laboratory tests to determine the
critical properties, but a tentative field classification is often made by drillers, geologists, or engineers; but
considerable skill and experience are required. Soil boring logs often include the engineering classification of
soils as described by the USCS.

Page 2-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 SPECIFICS OF THE UNIFIED SOIL CLASSIFICATION SYSTEM
Major Divisions Group Symbols Typical Descriptions
Well-graded gravels and gravel-sand
GW
mixtures. Little or no fines.
Clean Gravels
Gravels - 50% or more Poorly graded gravels and gravel-sand
GP
of coarse fraction mixtures. Little or no fines.
retained on #4 sieve. GM Silty gravels. Gravel-sand-silt mixtures.
Gravels with
Coarse Grained Fines.
GC Clayey gravels. Gravel-sand-clay mixtures.
Soils- more than
50% retained on Well-graded sands and gravelly sands. Little
SW
#200 sieve.* or no fines.
Clean Sands.
Poorly graded sands and gravelly sands. Little
Sands - 50% or more SP
or no fines.
of coarse fraction
passes #4 sieve. SM Silty sands. Sand-silt mixtures.
Sand with Fines
SC Clayey sands. Sand-clay mixtures.
SOIL MECHANICS

Inorganic silts, very fine sands, rock flour, silty

ML
or clayey find sands.
Inorganic clays of low to medium plasticity,
Silts and Clays - Liquid limit less than
CL gravelly clays, sandy clays, silty clays, lean
50.
clays.
Fine-Grained Soils Organic silts and organic silty clays of low
OL
- 50% or more plasticity.
passes #200 sieve.*
Inorganic silts, micaceous or diatomaceous
MH
fine sands or silts, elastic silts.

Silts and Clays - Liquid limit 50 or more CH Inorganic clays of high plasticity, fat clays.

OH Organic clays of medium to high plasticity.

Highly Organic Soils. PT Peat, muck and other highly organic soils.

*Based on the material passing the 3” (76 mm) sieve.

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EFFECTIVE STRESS AND PORE WATER PRESSURE
The total stress within a mass of soil at any point below a water table is equal to the sum of two
components, which are known as effective stress and pore water pressure. Effective stress is defined as
the total force on a cross section of a soil mass which is transmitted from grain to grain of the soil, divided
by the area of the cross section, including both solid particles and void spaces. It sometimes is referred
to as inter-granular stress. Pore water pressure is defined as the unit stress carried by the water in the soil
pores in a cross section. Effective stress governs soil behavior and can be expressed as:
σ` = s - u Equation 2-1
where: σ` = the effective stress in the soil
σ = total (or applied) stress
u = pore water pressure

SOIL STRENGTH
One of the most important engineering properties of soil is its shearing strength, or its ability to resist
sliding along internal surfaces within a given mass. Shear strength is the property that materially
influences the bearing capacity of a foundation soil and the design of CHANCE® helical piles/anchors. The

SOIL MECHANICS
basic principle is similar in many respects to an object that resists sliding when resting on a table.

The shear strength is the maximum shear resistance that the materials are capable of developing. Shear
strength of soil consists of two parts. The first part is the friction between particles (physical property).
The second part is called cohesion, or no-load shear strength due to a chemical bond between particles.

DRAINED SHEAR STRENGTH

Most unsaturated coarse-grained soils and some mixed grain soils, have sufficiently high permeability
that applied loads do not generate pore water pressures or any pore water pressures can dissipate during
shear. This is also true if the load is applied very slowly and water is allowed to drain. The shear strength
of these soils generally consists of both a “cohesive” component and a “frictional” component so that the
shear strength may be reasonably described by the Mohr-Coulomb equation as shown in Equation 2-3.

UNDRAINED SHEAR STRENGTH

Saturated fine-grained soils, such as clays and silty clays subjected to rapid loading have a low enough
permeability that excess pore water pressures cannot dissipate during shear. The behavior of these soils
is controlled by undrained shear strength. The strength is composed of only a “cohesive” component and
not a “frictional” component. The strength of these soils, is sometimes called “cohesion” (c), but a better
term is simply undrained shear strength, su. The undrained shear strength is controlled by stress history,
stress path, loading rate and vertical effective stress.

ANGLE of INTERNAL FRICTION

The shear strength of coarse-grained soils, such as sands, gravels and some silts, is closely analogous to
the frictional resistance of solids in contact. The relationship between the normal stress acting on a plane
in the soil and its shearing strength can be expressed by the following equation, in terms of stress:

Page 2-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 τ = σ tan φ Equation 2-2

where:

τ =the shearing stress at failure, or the

shear stress

angle of
internal friction - ø
shear strength
σ =normal stress acting on the failure
plane
shear strength φ =friction angle
cohesion

The internal friction of a given soil mass

lower confining stress
is related to the sliding friction between
normal stress

higher confining stress

individual soil grains and the interlocking
of soil particles. Shear strength
maximum stress
attributable to friction requires a normal
maximum verticle stress force (s), and the soil material must
exhibit friction characteristics, such as
Mohr’s Diagram for Moderately Plastic Soil multiple contact areas. In dense soils, the
Portland Cement Association (1996)
Figure 2-6 individual soil grains can interlock, much
like the teeth of two highly irregular gears.
SOIL MECHANICS

For sliding to occur, the individual grains

must be lifted over one another against the normal stress (σ). Therefore, the force required to overcome
particle interlock is proportional to the normal stress, just the same as sliding friction is proportional to
normal stress. In soil mechanics, Φ is designated the angle of internal friction, because it represents the sum
of sliding friction plus interlocking. The angle of internal friction (Φ) is a function of density, roundness or
angularity, and particle size.

COHESION
When saturated clay is consolidated, that is, when the volume of voids decreases as a result of water being
squeezed out of the pores, the shear strength increases with normal stress. If the shear strength of clays
which have a previous history of consolidation (i.e., pre-consolidated) is measured, the relationship between
shear strength and normal stress is no longer a line intersecting the ordinate at zero. The clays exhibit a
memory, or cohesive shear strength. In other words, the clays remember the pre-consolidation pressure
they were previously subjected to. This means considerable shear strength is retained by the soil. Figure 2-6
is an example of the relationship between shear strength and normal stress for a pre-consolidated plastic
clay as derived from a triaxial shear test. The intersection of the line at the ordinate is called the cohesion.

Cohesion is analogous to two sheets of flypaper with their sticky sides in contact. Considerable force is
required to slide one over the other, even though no normal stress is applied. Cohesion is the molecular
bonding or attraction between soil particles. It is a function of clay mineralogy, moisture content, particle
orientation (soil structure), and density. Cohesion is associated with fine grain materials such as clays and
some silts.

COULOMB EQUATION FOR SHEAR STRENGTH

The equation for shear strength as a linear function of total stress is called the Coulomb equation because it

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was first proposed by Coulomb in 1773.

τf = c + σ tan φ Equation 2-3

In terms of effective stress:

τf = c’ + (σ - u) tan φ’ Equation 2- 4
where:
τf=shear strength at failure
c’=cohesion
σ=total stress acting on the failure plane
φ’=friction angle
u=pore water pressure
Equations 2-3 and 2-4 are two of the most widely used equations in geotechnical engineering, since they ap-
proximately describe the shear strength of any soil under drained conditions. They are the basis for bearing
capacity Equations 5-6 and 5-31 presented in Section 5.

SITE INVESTIGATIONS
To this point, various definitions, identification properties, limit states, engineering classifications, and soil

SOIL MECHANICS
strength properties have been discussed. This section details some of the more common soil exploration
methods used to determine these various soil parameters.

The primary purpose of a geotechnical site investigation is to identify the subsurface stratification, and the
key soil properties for design of the steel foundation elements. Such studies are useful for the following
reasons:

CHANCE® Helical Piles/Anchors, Tiebacks and SOIL SCREW® Anchors:

• To locate the depth and thickness of the soil stratum suitable for seating the helical plates of the pile and to
determine the necessary soil strength parameters of that stratum.

• To establish the location of weak zones, such as peat type soils, or potentially liquefiable soils in which
column stability of the pile for compression loading situations may require investigation.

• To locate the depth of the groundwater table (GWT).

• To determine if there are any barriers to installing the piles to the required depth such as fill, boulders or
zones of cemented soils, or other conditions, which might require pre-drilling.

• To do a preliminary evaluation of the corrosion potential of the foundation soils as related to the
performance life of the steel pile.

The extent to which a soil exploration program should reach depends on the magnitude of the project. If
the proposed construction program involves only a small expenditure, the designer cannot afford to include
more in the investigation than a small number of exploratory borings, test pits or helical trial probe piles and
a few classification tests on representative soil samples. The lack of information about subsoil conditions
must be compensated for by using a liberal factor of safety. However, if a large-scale construction operation
is to be carried out under similar soil conditions, the cost of a thorough and elaborate subsoil investigation is
usually small compared to the savings that can be realized by utilizing the results in design and construction,
or compared to the expense that would arise from a failure due to erroneous design assumptions. The
designer must be familiar with the tools and processes available for exploring the soil, and with the methods
for analyzing the results of laboratory and field tests.

A geotechnical site investigation generally consists of four phases: (1) Reconnaissance and Planning, (2) Test
Boring and Sampling Program, (3) Laboratory Testing and (4) a Geotechnical Report. A brief description of
the requirements and procedures, along with the required soil parameters used in designing manufactured

Page 2-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 steel foundation products, is given in the following sections.

INITIAL RECONNAISSANCE AND PLANNING

The first step in any subsoil exploration program should be an investigation of the general geological
character of the site. The more clearly the site geology is understood, the more efficiently the soil exploration
can be performed.

Reconnaissance and Planning includes: (1) review of the proposed project and structural load requirements
and size of the structure and whether the project is new construction or structure repair, (2) a review of the
general soil and geologic conditions in the proximity of the site, and (3) a site visit to observe topography
and drainage conditions, rock outcrops if present, placement of borings, evidence of soil fill, including
rubble and debris and evidence of landslide conditions. The planning portion includes making a preliminary
determination of the number and depth of each boring as well as determining the frequency of soil
sampling for laboratory testing and requesting the marking of all utilities in the zone in which borings will be
conducted. Indicated below are recommended guidelines for determining the number of borings and the
depth to which the boring should be taken based on the project type.

Minimum Number of Test Boring(s)

Whether the project involves underpinning/repair of an existing structure or new construction, borings
SOIL MECHANICS

should be made at each site where helical piles or resistance piers are to be installed. The recommended
minimum number of borings necessary to establish a foundation soil profile is given below:

• Communication Towers - One (1) boring for each location of a cluster of piles or anchors, and one (1) boring
at the tower center foundation footing.

• If the project is small or when the project has a restricted budget, helical trial probe piles installed at the
site can provide information regarding the depth to the bearing strata and pile capacity.

• Or, boring number can be based on the overall project area, or based on minimum requirements per
applicable building codes.

Depth of Test Boring(s)

The depth of each boring will vary depending on the project type, magnitude of foundation loads and area
extent of the project structure. Some general guidelines for use in estimating required boring depths are
given below:

• Communication Towers - Minimum of 35 feet for towers over 100 feet tall and at least 20 feet into a
suitable bearing stratum (typically medium dense to dense for sands and stiff to very stiff for clays) for helical
anchors/piles. The suitable bearing stratum should have a minimum “N” value of 12 for sands and a minimum
of 10 for cohesive soils.

• Active Seismic Areas - Depth per local codes.

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TEST BORING and SAMPLING PROGRAM
In some cases, especially for small projects and shallow conditions, test borings may be conducted using
hand augers or other portable equipment. In most cases, however, the site investigation will typicallyrequire
drilling using a truck mounted drill rig.

The second step of the site investigation is to make exploratory boreholes or test pits that furnish more
specific information regarding the general character and thickness of the individual soil strata. This step and
an investigation of the general geological character of the site are recommended minimums. Other steps
depend on the size of the project and the character of the soil profile.

Method of Boring and Frequency of Sampling

Drilling is typically the most economical and
most expedient procedure for making borings
although test pits can be an alternative for
some projects. Three common types of borings
obtained using truck or track mounted drill rigs
are 1) wash borings (mud rotary), and 2) solid-
stem continuous flight (CFA) auger drilling and 3)
hollow stem flight auger (HSA) drilling. Any one

SOIL MECHANICS
of the three can be used, but CFA auger drilling
is the most common – particularly for shallow
borings. Wash borings or mud rotary drilling use
casings to hold the borehole open and a drilling
fluid to bring solid cuttings to the surface. The
casing is either driven with a hammer or rotated
mechanically while the hole is being advanced.
The cutting bit and drill rods are inserted inside the
casing and are rotated manually or mechanically.
The cuttings allow the driller to visually classify
the soil as to its type and condition and record the
data on a log sheet at the depth of the cutting bit.
Wash borings typically use water or drilling mud
such as bentonite slurry depending on the soil. In
some soil profiles, drilling mud prevents caving,
making full-length casing unnecessary. While
drilling proceeds, the driller observes the color and
appearance of the mixture of soil and water/mud.
This enables the driller to establish the vertical
sequence of the soil profile. At 5 ft (1.5 m) intervals,
or when a change in strata is noticed, the cutting Auger Drilling Operation
bit is removed and a spoon sample is taken. Figure 2-7

Auger drilling typically uses a continuous solid-stem flight auger rotated mechanically while the hole is
being advanced. The continuous flight auger (CFA) often includes a hollow stem, which acts as a casing to
hold the borehole open. Water or drilling mud is typically not used. Cuttings are carried to the surface by
the auger flights, which allow visual classification of the soil. The advantage of the hollow stem auger is to
permit the sampler and rod to be inserted down through the auger without removing the auger sections
each time a sampler is inserted. The auger acts as a temporary casing. Samplers are inserted inside the
auger casing to retrieve disturbed and undisturbed soil samples typically at 5 ft (1.5 m) intervals. Figure 2-7
demonstrates an auger drilling operation. Solid-stem augers are designated by the outside diameter of the
auger flights. Common sizes are 3 inch, 4 inch, and 6 inch. Hollow-stem augers are designated by the inside
diameter of the pipe. 3-1/4 inch and 4-1/4 inch are common sizes.

Page 2-15 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Drop Hammer

Drill Stem

6” (150 mm)
Increment Marks

Hollow
Stem
Auger

Figure 2-8
SOIL MECHANICS

Solid-stem continuous flight augers consist of a solid steel central shaft with a continuous auger, typically
available in 5 foot sections. The borehole is advanced by rotating the auger, which brings soil cuttings to the
ground surface. Disturbed samples of soil may be taken from the augers, but in order to obtain undisturbed
samples, the augers must be removed and a sampling tool placed in the bottom of the borehole. Continuous
flight augers work well in stiff to very stiff fine-grained soils that maintain an open borehole, but do not work
in very soft clays or sands and loose silts below the water table. These conditions require either wash boring or
the use of hollow stem augers (HSA).

The groundwater table (GWT), or phreatic surface is defined as the elevation at which the pressure in the
water is equal to that of the atmosphere. Information regarding the location of the groundwater table is
very important to the design and construction of deep foundations – especially in granular soils. Careful
observations should always be made and recorded, if circumstances permit, during exploratory drilling. It is
customary to note the water level on completion of the hole and after allowing the hole to stand overnight or
for 24 hours before backfilling. The use of drilling mud to stabilize the walls of the hole may preclude obtaining
this information.

Soil Sampling
Geotechnical site investigations almost always include the collection of soil samples for identification and
description, laboratory testing for soil classification and laboratory testing for soil strength and stiffness. There
are two broad types of soil samples that are often collected; 1) disturbed samples, and 2) undisturbed samples.
In general, disturbed samples may either be obtained from augers as previously discussed or more commonly
they are obtained using the standard penetration test (SPT). Undisturbed samples are typically obtained with
thin-walled push tubes called Shelby Tubes (ST).

Standard Penetration Test and Sampling

The cuttings from exploratory drill holes are inadequate to furnish a satisfactory conception of the engineering
characteristics of the soils encountered, or even the thickness and depths of the various strata. To obtain soil
samples from test borings, a sampling spoon is attached to the drill rod and lowered to the bottom of the hole.
The spoon is driven into the soil to obtain a sample and is then removed from the hole. The spoon is opened
up and the recovery (soil sample length inside the spoon) is recorded. The soil is extracted from the spoon
and inspected and described by the driller. A portion of the sample is placed in a glass jar and sealed for later
visual inspection and laboratory determination of index properties.

Page 2-16 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
The most common method of obtaining some information concerning relative density or the stiffness of in-
situ soil consists of counting the number of blows of a drop weight required to drive the sampling spoon a
specified distance into the ground. This dynamic sounding procedure is called the standard penetration test
(SPT). The essential features include a drop hammer weighing 140 lb (63.5 kg) falling through a height of 30”
(0.76 m) onto an anvil at the top of the drill rods, and a split spoon (SS) sampler having an external diameter
of 2” (50.8 mm) and a length of 30” (0.76 m). The spoon is attached to the drill rods and lowered to the
bottom of the drill hole. After the spoon reaches the bottom, the number of blows of the hammer is counted
to achieve three successive penetrations of 6” (0.15 m). The number of blows for the first 6” is disregarded
because of the disturbance that exists at the bottom of the drill hole. The number of blows for the second
and third 6” increments are added and designated the standard penetration test (SPT), “N” value, or blow
count. The data obtained from SPT tests are commonly recorded on soil boring logs relative to the sounding

Split Barrel
  Tube

SOIL MECHANICS
Recovered soil
sample
A = 1.0 to 2.0 in (25 to 50 mm)
B = 18.0 to 30.0 in (0.457 to 0.762 m) Open Shoe
C = 1.375 ± 0.005 in (34.93 ± 0.13 mm)
D = 1.50 + 0.05 - 0.00 in (38.1 + 1.3 = 0.0 mm)
E = 0.10 ± 0.02 in (2.54 ± 0.25 mm)
F = 2.00 + 0.05 - 0.00 in (50.8 + 1.3 - 0.0 mm)
G = 16.0º to 23.0º

Split Spoon Sample

The 1½ in (38 mm) inside diameter split barrel may be used
Geometry of Standard Penetration Test with a 16-gauge wall thickness split liner. The penetrating end
Split-Barrel Sampler (ASTM D 1586) of the drive shoe may be slightly rounded. Metal or plastic
Figure 2-9 retainers may be used to retain soil samples.

depth where the sample was taken. SPT values are widely used to correlate the shearing strength of soil for
the design of shallow and deep foundations – including CHANCE® Helical Piles. Values of soil friction angle
“φ” and cohesion “c” can be selected through correlation with the SPT “N” values. Details of the equipment
and standardized procedures are specified in ASTM D 1586. Figure 2-8 illustrates a drill crew conducting a
Standard Penetration Test. The split spoon sampler is shown in Figure 2-9.

Undisturbed Samples
In general, soil samples taken from split spoon samplers are always
considered disturbed to some degree for two reasons: 1) the sampler is
driven into the soil, and 2) the split spoon is very thick. For soil samples to
be used for laboratory analysis, the degree of disturbance of the samples
must be reduced to a minimum. Reasonably satisfactory samples can be
obtained in 50 and 76 mm samplers made of steel tubing about 1.5 mm
thick. The lower ends are beveled to a cutting edge to give a slight inside
clearance. This type of sampler is commonly referred to as a “Shelby
Tube”. The Shelby Tube is attached to the end of the drill rod and pushed
vertically down into the soil to obtain an undisturbed sample. Hand
samples or grab samples are sometimes taken from cuttings or test pits
CPT/CPTU and are useful for soil classification and determining index properties.
Details of the equipment and proper procedures for obtaining thin-walled
Shelby Tube samples are specified in ASTM D1587.

Page 2-17 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Figure 2-12 IN-SITU TESTING METHODS
Cone Penetration Test (CPT) / Piezocone (CPTU)
The cone penetration test consists of a cylindrical
probe with a cone tip having an apex angle of 60°
Nitrogen that is pushed slowly into the ground. The standard
size cone has a diameter of 1.405 inch, which gives a
projected end area of 10 cm2. Most cones also have a
short section behind
Control Console
the tip that is called the sleeve. The force on the tip
Coaxial Cable and the sleeve are measured independently during
penetration to give the cone tip resistance, qc, and the
Ground Line
sleeve resistance, fs. These values may then be used to
evaluate changes
in soil layering at a site and to estimate individual soil
properties, such as shear strength and stress history.
Rods Some cones are also equipped with a porewater
pressure sensor to measure the excess porewater
pressure as the cone advances. This is called a
SOIL MECHANICS

piezocone. The cone tip resistance obtained from a

piezocone is defined as qt,
the “effective” or corrected cone tip resistance since it
Blade is corrected for porewater pressure. A figure of a CPT
and CPTU are shown in Figure 2-10.

Cone penetrometers cannot penetrate more than a

few meters in dense sand, but they have been used to
depths up to 60 m or more in soft soils. The friction
ratio, defined as the friction resistance divided as
the tip resistance can be correlated with the type
Figure 2-12
of soil encountered by the penetrometer. Since no
samples are obtained by use of cone penetrometers,
borings and sampling are usually needed for definitive
information about the type of soil being investigated.

Dilatometer Test (DMT)

The dilatometer test consists of a flat stainless steel blade with a circular, flexible membrane mounted on
one side of the blade, as shown on Figure 2-11. The blade is pushed into the ground, much like a CPT or
CPTU, but instead of providing continuous data, pushing is stopped every 1 foot. Immediately after pushing
is stopped, the flexible membrane is expanded into the soil using nitrogen gas and a control console at the
ground surface. Two pressure readings are taken; 1) the A-Reading, which is the pressure required to just
initiate movement of the membrane into the soil, and 2) the B-Reading, which is the pressure required to
expand the center of the membrane
1 mm into the soil. The two Readings
are corrected for the stiffness of
the membrane to give two pressure
readings, P0 and P1. P0 and P1 are then
used along with the soil effective stress
at each test depth to obtain estimates
of specific soil properties such as
shear strength, modulus, stress history
and in-situ lateral stress. The specific
    requirements of the test are given in
Figure 2-13 Figure 2-11
ASTM D6635.

Page 2-18 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Field Vane Test (FVT)
The field vane test (FVT) or vane shear test (VST) is used to measure the undrained shear strength and
Sensitivity of medium stiff to very soft saturated fine-grained soils. It is considered one of the most reliable
and direct in-situ test methods for determining undrained shear strength and the only in-situ test that may be
used to determine Sensitivity. The test consists of inserting a thin four-bladed vane into the soil and rotating
slowly to create a shear failure in the soil. The vane is usually rectangular with a height to diameter ratio (H/D)
of 2, as shown in Figure 2-13. Initially, the maximum torque is measured to obtain the peak or undisturbed
undrained shear strength. Then, the vane is rotated 10 times and the test is repeated to obtain the remolded
undrained shear strength. The ratio of undisturbed to remolded strength is defined as Sensitivity, as
previously described. The specific requirements of the test are given in ASTM D2573.

The maximum torque (T) is measured during rotation and for a vane with H/D = 2 the undrained shear strength
is determined from:

su = (0.273T)/D3 Equation 2- 5

Vanes are available is different sizes to suit the soil at a particular site. The Field Vane Test may be especially
useful in evaluating sites for helical piles/anchors as it may give some insight to the engineer into the degree of
disturbance and strength reduction that the soil may experience during installation, depending on the Sensitivity.
It is important that the exact geometry of the vane (e.g., H, D, thickness of blades) and test procedures used

SOIL MECHANICS
be described in a Geotechnical Report so that the engineer may make any adjustments to the test results for
the equipment used.

MECHANICAL PROPERTIES OF VARIOUS ROCKS, TABLE 2-5

YOUNG’S MODULUS COMPRESSIVE TENSILE
BULK DENSITY POROSITY
ROCK AT ZERO LOAD STRENGTH STRENGTH
(g/cm3) (percent)
(105 kg/cm2) (kg/cm2) (kg/cm2)

Granite 2-6 2.6 - 2.7 0.5 - 1.5 1,000 - 2,500 70 - 250

Microgranite 3-8
Syenite 6-8
Diorite 7 - 10 1,800 - 3,000 150 - 300
Dolerite 8 - 11 3.0 - 3.05 0.1 - 0.5 2,000 - 3,500 150 - 350
Gabbro 7 - 11 3.0 - 3.1 0.1 - 0.2 1,000 - 3,000 150 - 300
Basalt 6 - 10 2.8 - 2.9 0.1 - 1.0 1,500 - 3,000 100 - 300
Sandstone 0.5 - 8 2.0 - 2.6 5 - 25 200 - 1,700 40 - 250
Shale 1 - 3.5 2.0 - 2.4 10 - 30 100 - 1,000 20 - 100
Mudstone 2-5
Limestone 1-8 2.2 - 2.6 5 - 20 300 - 3,500 50 - 250
Dolomite 4 - 8.4 2.5 - 2.6 1-5 800 - 2,500 150 - 250
Coal 1-2 50 - 500 20 - 50
Quartzite 2.65 0.1 - .05 1,500 - 3,000 100 - 300
Gneiss 2.9 - 3.0 0.5 - 1.5 500 - 2,000 50 - 200
Marble 2.6 - 2.7 0.5 - 2 1,000 - 2,500 70 - 200
Slate 2.6 - 2.7 0.1 - 0.5 1,000 - 2,000 70 - 200
Notes:
1) For the igneous rocks listed above, Poisson’s ratio is approximately 0.25
2) For a certain rock type, the strength normally increases with an increase in density and increase in Young’s Modulus (after Farmer, 1968)
3) Taken from Foundation Engineering Handbook , Winterkom and Fong, Van Nostrand Reinhold, page 72

Page 2-19 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Helical Probe
Shear strength also can be estimated by installing a helical pile “probe” and logging installation torque vs.
depth. The torque values can be used to infer shear strength based on the torque-to-capacity relationship
discussed in Section 6.

Rock Coring and Quality of Rock Measurement

When bedrock is encountered, and rock anchors are a design consideration, a continuous rock core must
be recovered to the depth or length specified. Typical rock anchors may be seated 20 ft. or 30 ft. into the
rock formation.

In addition to conducting compressive tests on the recovered rock core samples (See Table 2-5), the rock
core is examined and measured to determine the rock competency (soundness or quality). The rock quality
designation (RQD) is the most commonly used measure of rock quality and is defined as:

RQD = Σ Length of intact pieces of core (>100 mm)

Length of core run

The values of RQD range between 0 and 1.0 where an RQD of 0.90 or higher is considered excellent quality
rock.
SOIL MECHANICS

Helical piles/anchors rotated or torqued into the ground cannot be installed into hard, competent bedrock.
However, in upper bedrock surfaces comprised of weathered bedrock material such as weathered shale or
sandstone, the helix plates can often be advanced if the RQD is 0.30 or less.

LABORATORY TESTING OF RECOVERED SOIL SAMPLES

Laboratory testing is typically part of a subsurface investigation and may vary in scope depending upon
project requirements or variability in soil conditions. Some of the more typical laboratory tests are described
below:

Classification / Characterization Tests

• Visual Classification
Samples collected during the drilling operations should be visually classified. Every recovered sample
from the field boring and sampling program is inspected visually and given a visual description as to its
collection depth, percent recovery, moisture conditions, soil color, inclusion type and quantity, approximate
strength, odor and composition (See Table 2-4). In addition to this visual classification, a representative
number of samples are selected to conduct the following tests:

• Water Content
measures the amount of moisture in the soil. Moisture or water content is measured by weighing a soil
sample taken from the field on a laboratory scale. The soil sample is then placed in a standard oven for a
sufficient time to allow all the moisture to evaporate. After being removed from the oven, the soil sample
is weighed again. The dried weight is subtracted from the original weight to determine the water weight of
the sample. These methods are also used to determine the total (wet) unit weight and the dry unit weight.

• Particle Size Analysis

measures the distribution of particle sizes within the soil sample.

• Atterberg Limits
Liquid limit (LL), plastic limit (PL), shrinkage limit (SL), and plastic index (PI) – applies to cohesive types of
soil and is a measure of the relative stiffness of the soil and potential for expansion. Index properties (LL,
PL, SL, and PI) are determined using specially developed apparatus and procedures for performing these
tests. The equipment, specifications and procedures are closely followed in ASTM D 4318 classification
tests. The liquidlimit and the plastic limit are particularly important since they may be used along with the
natural water content to determine the liquidity Index.

Page 2-20 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
SAMPLE BORING LOG IN COARSE-GRAINED SOIL, TABLE 2-6

SOIL MECHANICS

Page 2-21 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Strength Characteristics
In some instances undisturbed soil samples are recovered in the field using a thin wall Shelby Tube. These
recovered samples are tested either in triaxial or direct shear tests to determine directly the friction
angle “φ” and the cohesion “c” of the soil. For cohesive (clay) soil samples, an unconfined compression
test “UC” is often conducted. The unconfined compression test is used to determine the unconfined
compression strength “qu” of the clay soil. The cohesion of the clay sample is then taken to be one-half of
“qu”. The unconfined compression test is commonly performed due to its low cost; however the results
tend to be conservative and simulate only total stress conditions with no confining pressure which may
not be appropriate for the project. For granular soils, the direct shear test is a relatively inexpensive test
to determine the soil friction angle and may also be used for undrained testing of cohesive samples. More
refined laboratory testing may be appropriate for large projects and may offer a cost saving potential by
justifying higher soil strength than using less sophisticated test methods. Some of the more complex strength
tests include, consolidated drained (CD), consolidated undrained (CU) and unconsolidated undrained (UU)
triaxial tests for total and effective stress paths at project specific confining stresses.

The Geotechnical Report

The geotechnical report provides a summary of the findings of the subsurface investigation, and the results
of the laboratory testing. Geotechnical reports usually include an introduction detailing the scope of work
performed, site history including geology, subsurface conditions, soil profile, groundwater location, potential
SOIL MECHANICS

design constraints such as seismic parameters and corrosion potential, foundation options, allowable load
capacities, and an appendix which includes soil boring logs. Soil boring logs provide a wealth of information
that is useful in the design of CHANCE® helical piles. Boring logs come in variety of designs since there is no
standard form, but they contain basically the same type of information – most of which has been discussed
in this section. Items to expect on a soil boring are: total boring depth, soil profile, description of soil samples,
sample number and type, Standard penetration test N-values, moisture content, Atterberg limits, unconfined
compression strength or undrained shear strength (cohesion), groundwater table location, type of drilling
used, type of SPT hammer used, and sample recovery. An example boring log is shown in Table 2-6 & 2-7.
Table 2-6 is a soil boring taken in a coarse-grained sand soil. Table 2-7 is a soil boring taken in a fine-grained
clay soil.

Page 2-22 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
SAMPLE BORING LOG IN FINE-GRAINED SOIL, TABLE 2-7

SOIL MECHANICS

Page 2-23 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 PROBLEM SOIL CONDITIONS
All natural materials, such as soil, will exhibit conditions of variability that may make a single solution inadequate
for inevitable problems that arise. It is wise to remember Dr. Terzaghi’s emphasis to have a secondary solution
ready when dealing with the variability of soils.

Deep Fill, Organic and Collapsible Soils

The existence of deep fills, organic and collapsible soils on a given project site are typically known before
the start of the project. This is usually determined during the subsurface investigation by means of drilling
or sounding. However, on large projects like an underground pipeline or transmission line that covers many
miles, these soils may occur in undetected pockets and hence present a potential problem. The best solution
is to be aware of the possibility of their existence and be prepared to install CHANCE® helical piles deeper to
penetrate through this material into better bearing soil. It is not recommended to locate the helical bearing
plates.

Loose Liquefiable Soils

Some deposits of saturated sand and silty sand are naturally loose and may be prone to lose strength or
liquefy during an earthquake or other dynamic loading. These soils are typically identified by very low SPT
N-values (typically less than about 6) and should be viewed with caution.
SOIL MECHANICS

Sensitive Clays
Some marine clay deposits are also very sensitive and can lose most of their shear strength when disturbed
and when loaded dynamically. These deposits are typically indentified with Liquidity Index greater than
about 1.2.

Expansive Soils
Expansive soils exist all over the earth’s surface, in nearly every region. These soils are often described as
having high shrink-swell behavior since they can also shrink if dried out. The natural in-place weathering of
rock produces sand, then silt, and finally clay particles – hence the fact that clay is a common soil type. Most
clay soils exhibit volume change potential depending on moisture content, mineralogy, and soil structure.
The upward forces (swell pressure) of expansive clay may far exceed the adfreeze forces generated by
seasonally frozen ground, yet foundations continue to be founded routinely in expansive soil with no
allowance for the potential expansion. Foundations should be designed to penetrate below the expansive
soil’s active zone, or be designed to withstand the forces applied the foundation.” The active zone is defined
as the depth of expansive soil that is affected by seasonal moisture variation. Another method used to design
foundations on expansive soil is to prevent the soil’s moisture content from changing. Theoretically, if the
moisture content does not change, the volume of the clay soil will not change. This is typically difficult to
control.

The tensile strength of deep foundations must be sufficient to resist the high tensile forces applied to the
foundation by expansive soil via skin friction within the active zone. As an expansive soil swells or heaves,
the adhesion force between the soil and the side of the foundation can be of sufficient magnitude to “jack” a
foundation out of the ground. CHANCE® helical piles are a good choice in expansive soils due to their relatively
small shaft size – which results in less surface area subjected to swell pressures and jacking forces.

A plasticity index (PI) greater than 25 to 30 is a red flag to the geotechnical engineer. A PI ≥ 25 to 30 indicates
the soil has significant volume change potential and should be investigated further. There are fairly simple tests
(Atterberg, soil suction test, swell potential) that can be conducted but should be practiced by the informed
designer.

Page 2-24 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Seasonally Frozen Ground
The most obvious soil in this category is the frost susceptible soils (typically, silt) as illustrated by the
growth of frost needles and ice lenses in freezing weather. This leads to a commonly observed expansion
phenomenon known as frost heave. Frost heave is typically observed on roadbeds, under concrete slabs, and
along freshly exposed cuts. Capillary breaks and vapor barriers in conjunction with proper drainage will do
much to control this problem, before CHANCE® Helical Piles or ATLAS RESISTANCE® Piers are installed.

A subcategory of this condition is seasonal permafrost. If possible, these ice lenses should be penetrated and
not relied on for end bearing.

REFERENCES
Bowles, Joseph E., Foundation Analysis and Design, Fourth Edition, McGraw Hill, 1988.

Chapel, Thomas A. (1998), Field Investigation of Helical and Concrete Piers in Expansive Soil, Proceedings of the Second International Conference on
Unsaturated Soils (UNSAT 1998) Beijing, China.

Hough, B.K., Basic Soils Engineering, Second Edition, Ronald Press Co., NY, 1969.

Portland Cement Association, PCA Soil Primer, 1992.

SOIL MECHANICS
Spangler, Merlin G. and R.L. Handy, Soil Engineering, Fourth Edition, Harper and Row Publishers, NY, 1982.

Terzaghi, Karl., Theoretical Soil Mechanics, John Wiley and Sons, NY, 1943.

Terzaghi, Karl, R.B. Peck and G. Mesri, Soil Mechanics in Engineering Practice, Third Edition, John Wiley and Sons, NY, 1996.

Weech, C. N., Installation and Load Testing of Helical Piles in a Sensitive Fine-Grained Soil, Thesis in Partial Fulfillment for Masters Degree, University of British
Columbia, Vancouver, B.C., 2002.

Page 2-25 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 PRODUCT FEASABILITY
SECTION 3

CONTENTS
FEASIBILITY OF USING CHANCE®HELICAL PRODUCTS.............. 3-3
SHAFT SIZE SELECTION BASED ON SOIL PARAMETERS........... 3-5
PRELIMINARY CHANCE HELICAL PILE/ ANCHOR.......................... 3-7

SYMBOLS USED IN THIS SECTION

N................................................................................................... Blow Count 3-3

PRODUCT FEASABILITY

SPT.................................................................. Standard Penetration Test 3-3

ASTM............................ American Society for Testing and Materials 3-3
FS........................................................................................ Factor of Safety 3-3
kip...................................................................................................Kilopound 3-3
SS...............................................................................................Square Shaft 3-5
RS............................................................................................... Round Shaft 3-5

DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to
point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted
prior to any installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption,
revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in
its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of
CHANCE® Civil Construction foundation support products.

Page 3-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
FEASIBILITY of USING CHANCE® HELICAL PRODUCTS
Hubbell Power Systems, Inc. manufactures steel foundation products that can be designed for a wide
range of soil conditions. In order to assist the designer/user in selecting the proper product for the
application, Figure 3-1 shows the product type suitable for various soils and rock conditions. When
reviewing Figure 3-1, the designer/user should note the following items:
• The most common selection of soil parameters for design is from field testing using the ASTM D
1586 Standard Penetration Test (SPT) and field or laboratory testing of shear strength (cohesion “c”
and friction angle "φ”). Refer to Section 2 in this manual for a detailed discussion of geotechnical
investigation requirements.
• A range is indicated for use of the helical piles (compression) and helical anchors (tension). As noted
on the chart, there are certain conditions for weathered rock and cemented sands where an initial
predrilling will permit the installation of helical plates under relatively high installing torque (generally
above 10,000 ft-lbs). Helical piles/anchors have been successfully installed on projects where the target
depth is not homogenous or consists of hard clays, cemented sands or weathered rock. These factors
must be considered and evaluated before a design can be finalized. Modifications may have to be made
to the design to be able to accomplish embedment into the target stratum such as:
• Cutting a “sea shell” shape into the leading edge of one or more of the helical plates.

PRODUCT FEASABILITY
• Predrilling prior to the installation of a helical pile/anchor.
• Using a shaft configuration that provides adequate torques and resistance to “spikes” during
installation.
The product selection chart shown in Figure 3-1 is intended for use on a preliminary basis. Hubbell
Power Systems, Inc. assumes no responsibility for the accuracy of design when based solely on Figure
3-1. A Preliminary Design Request Form is provided at the end of this section. This form can be copied
and then completed with the required information to request a preliminary design (application) by
the Hubbell Power Systems, Inc. engineering department. The completed form can be sent to Hubbell
Power Systems, Inc. or directly to your local CHANCE® Distributor.

All foundation systems should be designed under the direct supervision of a Registered Professional
Engineer knowledgeable in product selection and application.

Hubbell Power Systems, Inc. steel foundation products offer simplicity in design and flexibility in
adapting to the project. The design for ultimate and allowable bearing capacities or anchor loads for
helical products, is established using classical geotechnical theory and analysis, and supplemented by
empirical relationships developed from field load tests. In order to conduct the design, geotechnical
information is required at the site. The design and data shown in this manual are not intended for use
in actual design situations. Each project and application is different as to soils, structure, and all other
related factors.

Page 3-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 FACTORS of SAFETY
To recognize the variability of soil conditions that may exist at a site, as well as the varied nature
of loading on structures and how these loads are transferred through foundations, Hubbell Power
Systems, Inc. recommends an appropriate Factor of Safety (FS) when using CHANCE® helical foundation
products. Generally, the minimum FS is 2 on all permanent loading conditions and 1.5 for any temporary
load situation. Certain applications may require more stringent Factors of Safety on certain projects.

SITE ACCESS
The proximity to other structures, rights-of-way and obstructions are some of the first considerations
for any construction or improvement. Equipment access may be restricted due to overhead limits and
safety issues. The designer needs to consider all the possible limitations when selecting a foundation
system. CHANCE® Helical Piles/Anchors can generally be used anywhere a soil boring can be taken and
are virtually the most access-problem-free foundation systems available today. Restricted access and
similar concerns should be shown on the bid documents with the usual notes concerning site conditions.
Vibration and noise can be another limitation to conventional deep foundations (i.e., driven piles, drilled
piers). CHANCE helical piles/anchors have been installed inside office buildings, restaurants, retail shops
PRODUCT FEASABILITY

and hospitals without interrupting their normal routines. CHANCE helical pile certified installers can
assist the designer in determining the best type of product for the application.

WORKING LOADS
Helical piles have been used in the compressive mode to working (design) loads of 200 kip, in the form of
the CHANCE Helical Pulldown® micropile which is detailed later in this manual. In a “normal consolidated”
soil, the working load per foundation is typically less than 100 kip, but special cases may apply.

Working tension loads are typically 100 kip or less. The soil is generally the limiting factor as the number and
size of helical piles/anchors can be varied to suit the application. The designer should determine the shaft
series of products to use from the information provided in Section 7 – Product Drawings and Ratings.

SOILS
Soil may be defined for engineering purposes as the unconsolidated material in the upper mantle of the
earth. Soil is variable by the nature of its weathering and/or deposition. The more accurately one can define
the soil at a particular site; the better one can predict the behavior of any deep foundation, such as a
CHANCE® Helical Pile or Helical Pulldown micropile. In the absence of sufficient soil data, assumptions can
be made by the designer. The field engineer or responsible person needs to be prepared to make changes in
the field based on the soil conditions encountered during construction.

CHANCE helical piles can be installed into residual soil and virgin or undisturbed soils other than rock, herein
defined as having a SPT “N-value” less than 80 to 100 blows per foot per ASTM D1586. This implies that
the correct shaft series of helical piles must be chosen to match to the soil density. For example, a standard
1-1/2” shaft, Type SS helical pile with a total helix area of 1 square foot may require so much installing torque
that it may have difficulty penetrating into the bearing stratum without exceeding the torsional strength of
the shaft.

Water-deposited soil, marine, riverene (terraces or delta) and lacustrine have a high degree of variability.
They may be highly sensitive and may regain strength with time. In these conditions, it is good practice to
extend helical piles deeper into more suitable bearing soil.

Page 3-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Very soft or very loose natural, virgin or undisturbed soils overlying a very dense soil layer, such as
unweathered rock, could present a challenge to the installation of helical piles depending on the weathered
nature of the underlying rock. The helices may not develop enough downward thrust in upper soils
to penetrate into the hard underlying material. Down pressure is often applied to the shaft to assist in
penetration of the helices into the hard underlying material.

The use of helical piles/anchors in controlled or engineered fill is another good application. For example,
helical piles are used in the controlled fills of roadways to make improvements to the infrastructure.

Helical piles should be capable of penetrating the collapsible soils (such as loess) and poorly cemented
granular soils in the southwestern United States.

EQUIPMENT
Equipment suitability consideration and selection is the domain of the contractor. Installers are familiar
with the various spatial requirements for his equipment and is best able to determine the type of mounted
or portable equipment they can utilize to do the work. The designer may contact the local CHANCE®
distributor or contractor for guidance on this matter. A wide variety of equipment can be utilized for
projects based on such considerations as headroom.

PRODUCT FEASABILITY
In the utility industry digger derricks, line trucks, bobcats, and small excavators are used for installation of
helical piles.

Page 3-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 SHAFT SIZE SELECTION BASED ON SOIL PARAMETERS
An additional condition that must be evaluated is the ability of the helical pile to penetrate soil to the
required depth. For example, a foundation design may require an installation that penetrates a dense fill
layer consisting of compacted construction debris (concrete, rubble, etc.) through a compressible organic
layer below the fill and finally into the bearing strata. A helical pile shaft with a higher torque rating may be
required to adequately penetrate through the fill even though a helical pile shaft with a lower torque rating
would satisfy the ultimate capacity requirement. Table 3-1 outlines the maximum blow count or N-value that
a particular shaft will typically penetrate. Note that the Type SS helical piles with higher strength shafts and
helix material will penetrate harder/denser soils than the Type RS helical piles. Penetrating into harder/denser
soils is generally required to support larger loads. The N-values listed in this table are intended to serve as a
guide in the preliminary selection of the appropriate shaft series based on using multi-helix configurations.
The limits are not intended to be absolute values and higher N-value soils may be penetrated by varying
helix diameter, quantity and geometry. Therefore, local field installation experience may indicate more
appropriate maximum N-values.
PRODUCT FEASABILITY

CHANCE® HELICAL SHAFT SERIES SELECTION, TABLE 3-1

SHAFT SIZE TORQUE RATING MAX N-VALUE* MAX N-VALUE
SHAFT SERIES
in (mm) Ft-lb (N-m) Clay Sand
SS125 1-1/4 (32) 4,000 (5,400) 25 20
SS5 1-1/2 (38) 5,700 (7,730) 40 30
SS150 1-1/2 (38) 7,000 (9,500) 60 50
SS175 1-3/4 (44) 10,500 (14,240) 65 65
SS200 2 (51) 16,000 (21,700) <80 <80
SS225 2-1/4 (57) 21,000 (28,475) <80 <80
RS2875.203 2-7/8 (73) 5,500 (7,500) 25 20
RS2875.276 2-7/8 (73) 8,000 (10,847) 25 20
RS3500.300 3-1/2 (89) 13,000 (17,600) 25 20
RS4500.337 4-1/2 (114) 23,000 (31,200) 30 25
Large Diameter Pipe Pile Varies based on Shaft
30 30
(LDPP) Size
*N-value or Blow Count, from Standard Penetration Test per ASTM D 1586

Figure 3-1 on page 3-7 shows the same information as contained in the above table. This figure does not
address the proper product selection based on its application.

Page 3-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 CHANCE® Helical Piles / Anchors
S C HUBBELL POWER SYSTEMS, INC.
SS125
S C CHANCE® HELICAL PILE / ANCHOR
SSS5
SS150 S C PRODUCT SELECTION GUIDE
S/C
SS175
S/C
SS200, SS225

PRODUCT SERIES
S C
RS2875., RS3500
RS4500 S C

S C
ATLAS RESISTANCE® Piers
S = SAND
C = CLAY

VERY WEATHERED TO WEATHERED ROCK;

SOIL CEMENTED SANDS; HARD CLAY SOILS COMPETENT ROCK

1
SANDS VERY DENSE IGNEOUS ROCK
DOLERITE
DENSE BASALT
DIORITE
MEDIUM
GRANITE
LOOSE
VERY
LOOSE
1
METAMORPHIC ROCK

Product Selection Guide, Figure 3-1

QUARTZITE
SOIL GNEISS ROCK
SCHIST
CLAYS HARD
VERY STIFF
1
STIFF SEDIMENTARY ROCK LIMESTONE
VERY
SOFT MEDIUM DOLOMITE
TO
SOFT SANDSTONE
SHALE

POOR FAIR GOOD EXCELLENT

0 6 10 17 25 30 40 50 65 80 0.25 0.50 0.75 0.90

STANDARD PENETRATION BLOW COUNT (per ASTM D1586) ROCK QUALITY DESIGNATION (RQD)2

Page 3-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
“N” (BLOWS PER FOOT)
NOTES:
1. Range of RQD of Slightly Weathered to Competent Rock.
Σ length of intact pieces of core > 100 mm
2. Rock Quality Designation (RQD) =
length of core advance

PRODUCT FEASABILITY
 PRELIMINARY CHANCE® HELICAL PILE/ANCHOR DESIGN GUIDE
Hubbell Power Systems, Inc. manufactures CHANCE® helical piles/anchors products for use as tension
anchors and/or compression piles for varied foundation support applications. There are many different
applications for these end bearing piles and each application will require:

• An evaluation of the soil strata and soil characteristics of that stratum in which the helical plates or tip will
be seated.
• A selection of the appropriate CHANCE® helical pile foundation, including shaft type, helical plate size,
number and configuration. (Note: Type RS piles or CHANCE HELICAL PULLDOWN® micropiles are strongly
recommended in bearing/compression applications where the N-value of supporting soil around the shaft
is less than 4. These piles have greater column stiffness relative to the standard CHANCE type SS piles.
Refer to buckling/slenderness considerations in Section 5 of this technical design mManual for a detailed
discussion of this subject).
• A determination of the ultimate bearing capacity and suitable FS.

The preliminary design guide shown in Figures 3-2 and 3-3 is intended to assist certified installers, general
PRODUCT FEASABILITY

contractors and consulting engineers in the selection of the appropriate CHANCE helical pile.

Design should involve professional geotechnical and engineering input. Specific information involving
the structures, soil characteristics and foundation conditions must be used for the final design.

Page 3-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Preliminary Design Flowchart for New Construction
CHANCE® Helical Piles/Anchors

Owner, Prime Contractor or Consultant

Requires Deep Foundation or Anchorage Design

Geotechnical Review by CHANCE Helical Pile/Anchor Designer,

Report
CHANCE Distributor, and/or

Structural Certifed CHANCE Installer

Loads

PRODUCT FEASABILITY
Feasibility Assessment

Product Selection

Load Capacity Calculations

APPLICATION

Compression
Tension
Tiebacks
Soil Screw® Anchors

Lateral Load and Buckling

Corrosion

Installation Criteria and Report

Specifications and Shop

Drawings (as required)

Design Flowchart for CHANCE® Helical Piles and Anchors (New Construction), Figure 3-2

Page 3-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 PRELIMINARY DESIGN REQUEST FORM
Contact at Hubbell Power Systems, Inc., CHANCE® Civil Construction: ___________________________________________________

Installing Contractor
Firm: Contact:
Phone: Fax: Cell:

Project
Name: Type: o Foundation o Underpinning/Shoring
Address: o New Construction o Rock
o Tieback Retaining o Other:
o Soil Nail Retaining

Project Engineer? o Yes o No

PRODUCT FEASABILITY

Firm: Contact:
Address: Phone:
Fax:
Email:

Geotechnical Engineer? o Yes o No

Firm: Contact:
Address: Phone:
Fax:
Email:

Loads
Design Load FS (Mech) #1 FS (Geo) #1 Design Load FS (Mech) #2 FS (Geo) #2
Compression
Tension
Shear
Overturning

Define the owner’s expectations and the scope of the project:

_________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________
______________________________________________________________________________________________________________

The following are attached: o Plans o Soil Boring o Soil Resistivity o Soil pH

If any of the above are not attached, please explain:

_________________________________________________________________________________________________________________
_________________________________________________________________________________________________________

Date:___________________ Requested Response:_________________________ CHANCE® #:____________ Response:___________

Please copy and complete this form to submit a design request.

Page 3-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN METHODOLOGY

Page 4-1 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN METHODOLOGY
SECTION 4

CONTENTS
STRUCTURAL LOADS.................................................................................. 4-5
CHANCE® HELICAL ANCHOR/PILE BEARING CAPACITY............. 4-6

EVALUATING SOIL PROPERTIES FOR DESIGN................................. 4-24

FACTOR OF SAFETY.................................................................................... 4-32

HELICAP® HELICAL CAPACITY DESIGN SOFTWARE..................... 4-34

APPLICATION GUIDELINES FOR CHANCE®

DESIGN METHODOLOGY

HELICAL PILES/ANCHORS........................................................................ 4-40

LATERAL CAPACITY OF HELICAL PILES............................................ 4-41

BUCKLING/SLENDERNESS CONSIDERATIONS................................ 4-49

CHANCE® HELICAL PILE/DEFLECTION AT WORKING LOAD..... 4-54

SYMBOLS USED IN THIS SECTION

Pw ................................................................................. Pier Working Load 4-5

DL ..................................................................................................Dead Load 4-5
LL ....................................................................................................Live Load 4-5
SL ................................................................................................. Snow Load 4-5
W ......................................................................................................Soil Load 4-5
FSh ............................................................. Factor of Safety (hardware) 4-5
B ...........................................Helix Diameter & Footing Width (Base) 4-6
x ............................................................................................... Helix Spacing 4-6
QULT ..........................................................Ultimate Capacity of the Soil 4-8
Ah............................................................................... Projected Helix Area 4-8
c ............................................................................................... Soil Cohesion 4-8
q’ ............................................................Effective Overburden Pressure 4-8
γ ’ ........................................................Effective Unit Weight of the Soil 4-8
Nc .....Bearing Capacity Factor for Cohesive Component of Soil 4-8
Nq .Bearing Capacity Factor for Non-Cohesive Component of Soil 4-8

Page 4-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Nγ Bearing Capacity Factor for SoiL Weight and Foundation Width. 4-8
QH .....................................................................Individual Helix Capacity 4-10
D .................................................................Vertical Depth to Helix Plate 4-10
φ ........................................................................ Angle of Internal Friction 4-11
γ ................................................................. Effective Unit Weight of Soil 4-11
su...................................................................... Undrained Shear Strength 4-12
Fc ........................................................................................ Breakout Factor 4-12
K0 .............................................. Coefficient of Earth Pressure at Rest 4-13
Ac .......................................................Surface Area of Truncated Cone 4-13
Sa......................................................Undrained Shear Strength of Clay 4-14
QM .Total Bearing Capacity of Multi Screw Pile/ Helical Anchor 4-18

DESIGN METHODOLOGY
α ............................................................................................Adhesion Factor 4-19
Qs ............................................................................ Capacity Upper Limit 4-21
psf...................................................................... Pounds per Square Foot 4-23
Qt ......................... Total Ultimate Multi-Helix Anchor/Pile Capacity 4-27
σ`vo .............................................................Effective Overburden Stress 4-31
(N1)6o................................................................. Normalized SPT N-value 4-32
σo ............................................Mean Normal Stress for Grout Column 4-37
D ....................Diameter of Timber, Steel or Concrete Pile Column 4-37
fs ................ Sum of Friction and Adhesion Between Soil and Pile 4-37
∆Lf .......................................................................Incremental Pile Length 4-37
Ca ...................................................................................... Adhesion Factor 4-38
so................................................................................. Mean Normal Stress 4-37
q................................................... Effective Vertical Stress on Element 4-38
K...................................................Coefficient of Lateral Earth Pressure 4-38
ø.................. Effective Friction Angle Between Soil & Pile Material 4-38
S......................... Average Friction Resistance on Pile Surface Area 4-40
Po............................................................. Average Overburden Pressure 4-40
Kp ..............................................Coefficient of Passive Earth Pressure 4-45
Ka .................................................Coefficient of Active Earth Pressure 4-46
H ..................................................Height of Wall or Resisting Element 4-46
Pa ............................................................................. Active Earth Pressure 4-46

Page 4-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Pp ........................................................................... Passive Earth Pressure 4-46
Pcrit ................................................................ Critical Compression Load 4-49
E .................................................................................Modulus of Elasticity 4-49
I ........................................................................................Moment of Inertia 4-49
K .......................................................................End Condition Parameter 4-49
Lu ...............................................................................Unsupported Length 4-49
d ....................................................................Foundation Shaft Diameter 4-50
L ........................................................................ Foundation Shaft Length 4-50
Kl/r ................................................................................. Slenderness Ratio 4-51
Pcr ........................................................................... Critical Buckling Load 4-51
DESIGN METHODOLOGY

Ep ..................................... Modulus of Elasticity of Foundation Shaft 4-51

Ip ............................................Moment of Inertia of Foundation Shaft 4-51
kh .......................................................... Modulus of Subgrade Reaction 4-51
Ucr ..............................................................................Dimensionless Ratio 4-51
y .................................................Lateral Deflection of Shaft at Point x 4-51
x .......................................................................... Distance Along the Axis 4-51
EI ...................................... Flexural Rigidity of the Foundation Shaft 4-51
Q .........................................................................Axial Compressive Load 4-51
Esy ........................................................... Soil Reaction per Unit Length 4-51
Es .................................Secant Modulus of the Soil Response Curve 4-51
Ca ...................................................................................... Adhesion Factor 4-40

DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to
point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted
prior to any installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption,
revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in
its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of
CHANCE® Civil Construction foundation support products.

Page 4-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
4.1 STRUCTURAL LOADS
Types Of Loads
There are generally four common loads that may be resisted by a given foundation element. These are
compression, tension, lateral and moment loads. It is anticipated that anyone reading this manual will know
the meanings of these loads, but for completeness we will describe them for our purposes here.
A compression load is one that will axially shorten a foundation and is typically considered to act vertically
downward. The tension load tends to lengthen a foundation and is often taken to be acting vertically
upward. A lateral load is one that acts parallel to the surface of the earth or perpendicular to a vertically
installed foundation. The lateral load can also be referred to as a shear load. Moment load tends to bend the
foundation about one of its transverse axis. A fifth load is torsion. It tends to twist the foundation about its
longitudinal axis. This is a load that is seldom applied except during installation of a helical pile/anchor.
This design manual generally assumes the use of allowable strength design (ASD), i.e., the entire Factor of
Safety (FS) is applied to the ultimate capacity of the steel foundation product in the soil to determine a
safe (or design) strength. Section 7 of this design manual provides the nominal, LRFD design, and allowable
strength of helical pile/anchor. Therefore, the designer can choose to use either limit states or allowable
strength design for helical pile/anchor.

DESIGN METHODOLOGY
Design Or Working Load
The design load or working load is typically considered to be the same load. This is a combination of dead
loads and live loads. The dead loads are simply the gravity load of structure, equipment, etc. that will always
be there to be resisted by the foundation. The live load takes into account seismic events, wind load, snow
load, ice, and occupancy activities. They are transient loads that are dynamic in nature. These loads are
sometimes referred to as Unfactored Loads. They do not include any Factor of Safety.
Soil load may be present in foundation lifting or restoration activities and can represent a significant
percentage of the overall design load on an individual underpinning element, sometimes approaching as
much as 50% of the total design load.

Ultimate Load
The ultimate load is the combination of the highest dead loads and live loads including safety factors. This
load may or may not be the load used for foundation design.

Factor Of Safety
Before a foundation design is complete a Factor of Safety (FS) must be selected and applied. In allowable
strength design, the Factor of Safety (FS) is the ratio between the ultimate capacity of the foundation and
the design load. A Factor of Safety of 2 is usual but can vary depending on the quality of the information
available for the design process and if testing or reliable production control is used. Hubbell Power Systems,
Inc. recommends a minimum Factor of Safety of 2 for permanent loading conditions and 1.5 for any
temporary loading condition.
Note: Ultimate load is not the same as ultimate capacity. A foundation has some finite capacity to resist
load. The ultimate capacity may be defined as the minimum load at which failure of the foundation is
likely to occur, and it can no longer support any additional load.

Reversing Loads
Foundation design must allow for the possibility that a load may reverse or change direction. This may not
be a frequent occurrence, but when wind changes course or during seismic events, certain loads may change
direction. A foundation may undergo tension and compression loads at different times or a reversal in the
direction of the applied shear load. The load transfer of couplings is an important part of the design process
for reversing loads.

Page 4-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Dynamic Loads
Dynamic or cyclic loads are encountered when supporting certain types of equipment or conditions
involving repetitive impact loads. They are also encountered during seismic events and variable wind events.
These loads can prove destructive in some soil conditions and inconsequential in others. The designer
must take steps to account for these possibilities. Research has shown that multi-helix anchors and piles
are better suited to resist dynamic or cyclic loads. Higher factors of safety should be considered when
designing for dynamic loads.

Codes And Standards

The minimum load conditions, especially live loads for buildings are usually specified in the governing
building codes. There are municipal, state and regional as well as model codes that are proposed for general
usage. The designer must adhere to the codes for the project location. Chapter 18 of the IBC 2009 and 2012
contain Code sections for helical piles, as well as sections for general design of deep foundations. Section 4
of ICC-ES ESR-2794 provides guidelines for the design and installation of helical piles.

Technical Design Assistance

The engineers at Hubbell Power Systems, Inc. have the knowledge and understand all of the elements of
DESIGN METHODOLOGY

design and installation of CHANCE® Helical Piles/Anchors, Tiebacks, Soil Screw® Anchors. Hubbell Power
Systems, Inc. will prepare a complimentary product selection (“Preliminary Design”) on a particular project

4.2 CHANCE® HELICAL PILE/ANCHOR ULTIMATE BEARING CAPACITY

The capacity of a helical pile/anchor is dependent on the strength of the soil, the projected area of
the helix plate(s), and the depth of the helix plate(s) below grade. The soil strength can be evaluated
by use of various field and lab techniques. The projected area is controlled by the size and number of
helix plates. Helical anchors and screw piles may be used for a variety of applications involving both
tension loading (helical anchors) and compression loading (screw piles or helical piles). Screw piles
and helical anchors are generally classified as either “shallow” or “deep” depending on the depth of
installation of the top helix below the ground surface, usually with respect to the helix diameter. There
are some situations in which the installation may be considered partway between “shallow” and “deep”,
or “intermediate”. In this Manual, only design procedures for “shallow” and “deep” installations will be
described. Table 1 gives a summary of the most common design situations involving screw-piles and
helical anchors that might be encountered. Note that the use of “shallow” multi-helix anchors for either
compression or tension loading is not a typical application and is not covered in this Technical Design
Manual.
The dividing line between shallow and deep foundations has been reported by various researchers to
be between three and eight times the foundation diameter. To avoid problems with shallow installations,
the minimum recommended embedment depth of helical piles and anchors is five helix diameters (5D).
The 5D depth is the vertical distance from the surface to the top-most helix. Whenever a CHANCE®
Helical Pile/Anchor is considered for a project, it should be applied as a deep foundation for the
following reasons:
1. A deep bearing plate provides an increased ultimate capacity both in uplift and compression.
2. The failure at ultimate capacity will be progressive with no sudden decrease in load resistance after
the ultimate capacity has been achieved.
The approach taken herein for single-helix piles/anchors assumes that the soil failure mechanism will
follow the theory of general bearing capacity failure. For multi-helix helical piles and anchors, two
possible modes of failure are considered in design, depending on the relative spacing of the helix
plates. For wide helix spacing (s/B ≥ 3), the Individual Plate Bearing Method is used; for close helix
spacing (s/B < 3), the Perimeter Shear Method is used.

Page 4-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
≥

DESIGN METHODOLOGY
≥

Individual Bearing and Perimerter Shear Models for Helical Piles with Slender Shafts
Figure 4-1

Page 4-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 These two methods are illustrated in Figures 4-1a & c (Individual Plate Bearing) and 4-1b & d (Perimeter
Shear). With Individual Plate Bearing, the helix capacity is determined by calculating the unit bearing
capacity of the soil at each helix and then multiplying the result by the individual helix’s projected area.
Friction along the central shaft is typically not used to determine capacity, but may be included when
the central shaft is round, as will be discussed later in this section. The Individual Plate Bearing Method
assumes that load capacity will be developed simultaneously and independently by each helix; i.e. no
interaction between helix plates. The Perimeter Shear Method assumes that because of the close helix
spacing, a prism of soil will develop between the helix plates and failure in this zone occurs along a
plane as shown in Figure 4-1b & d. In reality, the Perimeter Shear Method includes both plate bearing
and perimeter shear failure as illustrated.
The following is Terzaghi’s general bearing capacity equation, which allows determination of the
ultimate capacity of the soil. This equation and its use will be discussed in this section, as it forms the
basis of determining helix capacity in soil.
TABLE 4-2 TYPICAL DESIGN SITUATIONS FOR SINGLE-HELIX
& MULTI-HELIX SCREW-PILES AND HELICAL ANCHORS
Single-Helix Multi-Helix
DESIGN METHODOLOGY

Failure Condition Failure Condition

Shallow Deep Shallow Deep

C T C T C T C T

Clay Clay Clay Clay N/A N/A Clay Clay

Sand Sand Sand Sand N/A N/A Sand Sand

Mixed Mixed Mixed Mixed Mixed Mixed
N/A N/A
Soils Soils Soils Soils Soils Soils

Qult = Ah ( cNc + q’Nq + 0.5 γ’ BNγ )

Qult = Ultimate capacity of the soil
Ah = Projected helix area

where c = Soil cohesion

q’ = Effective overburden pressure
B = Footing width (base width)
γ’ = Effective unit weight of the soil
and Nc, Nq, and Nγ are bearing capacity factors

Terzaghi’s Bearing Capacity Factors are shown in the Table 4-2.

Page 4-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
TABLE 4-3. TERZAGHI’S SHALLOW FOUNDATION BEARING CAPACITY
FACTORS [FROM AND BOWLES (1988) AND ASCE (1993A) ]
φ’ Nc Nγ Nq
0 5.7 0.0 1.0
10 9.6 1.2 2.7
12 10.8 1.7 3.3
14 12.1 2.3 4.0
16 13.7 3.0 4.9
18 15.5 3.9 6.0
20 17.7 4.9 7.4
22 20.3 5.8 9.2
24 23.4 7.8 11.4
26 27.1 11.7 14.2
28 31.6 15.7 17.8

DESIGN METHODOLOGY
30 37.2 19.7 22.5
32 44.0 27.9 28.5
34 52.6 36.0 36.5
36 63.5 52.0 47.2
38 77.5 80.0 61.5
40 95.7 100.4 81.3
42 119.7 180.0 108.7
44 151.9 257.0 147.7
46 196.2 420.0 204.2
48 258.3 780.1 287.8

Following is quoted from Bowles (1988) concerning the use of Equation 4-6 for deep foundations where
the various terms of the bearing capacity equation are distinguished.
“1. The cohesion term predominates in cohesive soil.
2. The depth term (q’Nq) predominates in cohesionless soil. Only a small D (vertical depth to footing or
helix plate increases Qult substantially.
3. The base width term 0.5γ ’BNγ provides some increase in bearing capacity for both cohesive and
cohesionless soils. In cases where B is less than about 2 feet (0.61 m), this term could be neglected
with little error.”
The base width term of the bearing capacity equation is not used when dealing with helical anchors/piles
because, as Bowles indicates, the resulting value of that term is quite small. The effective overburden
pressure (q’, of consequence for cohesionless soils) is the product of depth and the effective unit weight
of the soil. The water table location may cause a reduction in the soil bearing capacity. The effective unit
weight of the soil is its in-situ unit weight when it is above the water table. However, the effective unit
weight of soil below the water table is its in-situ unit weight less the unit weight of water.

Page 4-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Notes on use of Terzaghi’s Bearing Capacity equation:
1. Because helix plates are generally round, Terzaghi’s adjustment for round footings is sometimes used
for compression loading:
QH = AH(1.3c’NC + q’Nq + 0.6γ’BNγ)

2. Because B is considered very small for screw-piles and helical anchors, relative to most concrete
footings, most engineers choose to ignore the term 0.5γ’BNγ in design.
3. In saturated clays under compression loading, Skempton’s (1951) Bearing Capacity Factor for shallow
round helical plates can also be used:
NC = 6.0(1 + 0.2D/B) ≤ 9.0
4. The unit weight of the soil is the total (wet) unit weight if the helical plate (s) is above the water table
and the buoyant unit weight if the helical plate(s) is below the water table.
DESIGN METHODOLOGY

5. For saturated clay soils, Nq = 1.0; For sands, Nq is a function of the friction angle, φ’.
6. For square-shaft anchors/piles, the shaft resistance is generally ignored. For round shaft piles/
anchors there may be a component of shaft resistance that contributes to capacity depending on the
configuration of connections between extension sections.
7. In all cases, for both compression and tension loading, the upper limit of capacity is governed by
the mechanical strength of the pile/anchor as provided by the manufacturer. See Section 7 of this
Manual for mechanical strength ratings of CHANCE® helical piles/anchors.

Concern can develop when a helical pile/anchor installation is terminated in sand above the water table
with the likelihood that the water table will rise with time to be above the helix plates. In this situation,
the helical pile/anchor lead section configuration and depth should be determined with the water at
its highest anticipated level. Then the capacity of the same helical-pile/anchor should be determined in
the same soil with the water level below the helical pile/anchor, which will typically produce higher load
capacities and a more difficult installation, i.e., it will require more installation torque. It is sometimes the
case that a larger helical pile/anchor product series, i.e., one with greater torque capacity, must be used
in order to facilitate installation into the dry conditions.

4.3 SINGLE-HELIX SCREW-PILES AND HELICAL ANCHORS

SHALLOW INSTALLATION
Compression Loading (Shallow Single-Helix)
A shallow installation, like a shallow foundation, is one in which the ratio of depth (D) of the helix to
diameter (B) of the helix is less than or equal to about 5, i.e., D/B ≤ 5. In this case, the design is very
analogous to compression loading of a shallow foundation.

Page 4-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Saturated Clays φ’ = 0; c > 0
In saturated clays with φ’ = 0, the term Nγ = 0 and Nq = 1.0. The bearing capacity equation becomes:
QH = AH(cNC + γ’D) Equation 4-9
where:
QH = Ultimate Bearing Capacity
AH = Projected Helix Area
c = “cohesion”; for φ’ = 0; c = undrained shear strength = su
NC = Bearing Capacity Factor for φ’ = 0; for round plates NC = 6.0(1 + 0.2D/B) ≤ 9
γ’ = effective unit weight of soil above screw-pile
D = Depth
Note: The term γ’D is sometimes ignored because it is very small.
Sands φ’ > 0; c’= 0
In clean sands with zero cohesion, the cohesion term of the bearing capacity equation drops out and
only two terms remain:

DESIGN METHODOLOGY
QH = AH(q’Nq + 0.5γ’BNγ) Equation 4-10
where:
q’ = effective surcharge (overburden pressure) = γ’D
Nq and Nγ are evaluated from the Table of Bearing Capacity Factors
Note: The term 0.5γ’BNγ is typically ignored for helical piles because the helix plate is small

Mixed Soils φ’ > 0; c’ > 0

Many soils, such as mixed-grain silty sands, sandy silts, clayey sands, etc., have both a frictional and
cohesive component of strength. In these cases, the bearing capacity equation includes all three terms:
QH = AH(c’NC + q’Nq + 0.5γ’BNγ) Equation 4-11
Note: The term 0.5γ’BNγ is typically ignored for helical piles because the helix plate is small.

Tension Loading - Axial Uplift (Shallow Single Helix)

Under tension loading in axial uplift, the behavior of a shallow single-helix helical anchor is currently
approached more-or-less as an “inverse” bearing capacity problem and the concern is for the failure
surface to reach the ground surface, producing “breakout” of the helical plate. Helical anchors should
not be installed at vertical depths less than 5 ft. for tension loading. The design approach is similar to
that under compression loading, except that instead of using a Bearing Capacity Factor, NC, a Breakout
Factor, FC, is used.

Page 4-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Saturated Clays φ’ = 0; c > 0
Test results and analytical studies indicate that the Breakout Factor for saturated clays in undrained
loading varies as a function of the Relative Embedment of the plate, i.e., D/B. This is much like the
transition of shallow to deep foundation behavior under compression loading. Table 5-3 shows the
variation in FC vs. D/B for circular plates. This figure (from Das (1990) shows that FC = 1.2(D/B) ≤ 9, so
that at D/B > 7.5, FC = 9 (i.e., the transition from shallow to deep behavior under tension in clays occurs
at about D/B > 7.5). In this case, the ultimate uplift capacity is similar to Equation 5-9 and is given as:

QHU = AH(cFC + γ’D)

where:
QHU = Ultimate Uplift Capacity
c = “cohesion”; for φ’ = 0 c = undrained shear strength = su
FC = Breakout Factor for φ’ = 0; FC = 1.2(D/B) ≤ 9
γ’ = effective unit weight of soil above helical anchor plate
DESIGN METHODOLOGY

D = Depth
Note: The term γ’D is sometimes ignored because it is very small.
In some situations the undrained shear strength of clays under tension loading may be reduced
to account for some disturbance effects of the clay above the helical plate but this is a matter of
engineering judgment.

TABLE 4-3 VARIATION IN UPLIFT BREAKOUT FACTOR

FOR SHALLOW SINGLE-HELIX ANCHORS IN CLAY

Page 4-12 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Sands φ’ > 0; c’ = 0
In sands the uplift behavior of shallow (generally D/B ≤ 5) single-helix anchors develops a failure zone
that looks similar to an inverted truncated cone. The failure is assumed to take place by the perimeter
shear acting along this failure surface, which is inclined from the vertical at an angle of about φ’/2, as
shown in Figure 4.2, and also includes the mass of the soil within the truncated cone. The Ultimate Uplift
Capacity is calculated from:
QHU = WS + πgK0(tanφ’)(cos2φ’/2) [(BD2/2) + (D3tanφ’/2)/3)] Equation 4-13
where:
WS = Mass of Soil in Truncated Cone = gV
γ = Total (wet) Unit Weight
V = Volume of Truncated Cone
K0 = At-Rest Lateral Earth Pressure Coefficient
B= helix diameter
D = vertical plate depth
The volume of the truncated cone is determined from:

DESIGN METHODOLOGY
V = [πD/3][B2 + (B + 2Dtanφ’/2)2 + (B)(B + 2D tan φ’/2)] Equation 4-14
Values of the at-rest lateral earth pressure coefficient for sands can reasonably be taken as:
K0 = 1 – sinφ’

Mixed Soils φ’ > 0; c’ = 0

In mixed soils with both frictional and cohesive
components of shear strength, there is an added
resisting force in uplift for shallow installations
above the value given by Equation 4-13. This added
component results from cohesion acting along the
surface of the truncated cone failure zone between
the helical plate and the ground surface so that
an additional term may be added to Equation 5-13
giving:
QHU = WS + πgK0(tanφ’)(cos2φ’/2) Equation 4-15
[(BD2/2) + (D3tanφ’/2)/3)] + (c)(AC)
where:
AC = Surface Area of Truncated Cone
The surface area of a truncated cone can be obtained
Figure 4-2 Proposed Failure Mechanism for Shallow
Single-Helix Anchors in Dense Sand.
from:

AC = π[(R2 + r2) + [(R2 – r2) + (D(R + r))2]0.5] Equation 5-16

where:
r = Radius of Helical Plate = B/2
R = Radius of Cone Failure Surface at the Ground Surface = B/2 + (D)tan(φ’/2)
The additional component of uplift resulting from soil cohesion, is sometimes ignored since soil cohesion
is often lost from water infiltration or rising water table.

Page 4-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 SINGLE-HELIX SCREW-PILES AND SCREW-ANCHORS – DEEP INSTALLATION
Deep installations of screw-piles and helical anchors are generally more common than shallow
installations, provided there is sufficient soil depth to actually perform the installation. The reason is
simply that higher load capacities are generally developed from a deeper installation in the same soil
so it makes more sense economically to go for a deep installation when possible. Figure 5.5 below
demonstrates the single-helix plate capacity model, where the soil failure mechanism will follow the
theory of general bearing plate capacity. Compression capacity is mobilized from soil below the helix
plate and tension capacity from soil above the helix plate.
Compression Loading (Deep Single-Helix)
A deep installation, like a deep foundation, is one in which the ratio of depth (D) of the helix to diameter
(B) of the helix is greater than 5 - 7, i.e., D/B > 5 - 7. In this case, the design is very analogous to
compression loading of deep end bearing foundation.
DESIGN METHODOLOGY

Figure 4-5 Single-Helix Plate Bearing Capacity Model – Helical Piles with Slender Shafts

Saturated Clays φ’ = 0; c’ > 0

Under compression loading, the ultimate capacity of a single-helix screw-pile in clay is calculated from
Equation 5-9 as:
QH = AH[(NC)(su) + γ’D]]
where:
NC = Bearing Capacity Factor for Deep Failure = 9
Which gives:
QH = AH[(9)(su) + γ’D] Equation 4-17

Page 4-14 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Sands φ’ > 0; c’ = 0
For clean, saturated sands, the “cohesion” is normally taken as zero, reducing the ultimate capacity, as in
Equation 5-10, to:
QH = AH(q’Nq + 0.5γ’BNγ)
Even in moist sands or sand with a small amount of fines that may give some “cohesion”, this is usually
ignored. Because the area of the plate is small, the contribution of the “width” term to ultimate capacity
is also very small and the width term is often ignored leaving:
QH = AH(q’Nq) Equation 4-18

For deep installations, the bearing capacity factor Nq is usually obtained from values used for
determining the end bearing capacity for deep pile foundations, which is different than the values
used for shallow foundations. There are a number of recommendations for Nq available in foundation
engineering textbooks as shown in Figure 4-6. The difference in Nq values shown in Figure 4-6 is largely
related to the assumptions used in the failure mechanism. Figure 4-7 gives a reasonable chart of Nq
values as a function of the friction angle of the soil, φ’, that may be used for screw-piles and helical

DESIGN METHODOLOGY
anchors. The value of Nq in Figure 5-7 is obtained from:

Nq = 0.5 (12 x φ’)φ’/54 Equation 4-19

Note: In some sands, the unit end bearing capacity of deep foundations may reach a limiting value.
The point at which this occurs is generally termed the “critical depth”. Critical depth is defined as the
depth at which effective vertical stress, a.k.a. overburden pressure, will not increase with depth. Critical
depth is not specifically defined for screw-piles and helical anchors, but engineers often use it with deep
installation in saturated sands.
Mixed Soils φ’ > 0; c’ > 0
The ultimate capacity of a deep single-helix screw-pile in mixed-grain soils can be taken from traditional
bearing capacity theory using Equation 5-11:
QH = AH(cNc + q’Nq + 0.5γBNγ)
Note: The term 0.5γ’BNγ is typically ignored for helical piles because the helix plate is small.

TENSION LOADING – AXIAL UPLIFT (DEEP SINGLE-HELIX)

Saturated Clays φ’ = 0; c’ > 0
Under tension loading, the ultimate capacity of a single-helix screw-anchor in clay the ultimate capacity
is calculated using the same approach given in Section 5.2.2.1.a. In some cases a reduction may be made
in the undrained shear strength to account for soil disturbance above the helical plate as a result of
installation, depending on the Sensitivity of the clay. Also, as previously noted in Section 5.2.1.2.a, for
a deep installation (D/B > 7.5) the Breakout Factor, FC has a default value of 9. The bearing capacity
equation becomes:
QHU = AH[(9)su + γ’D]
Sands φ’ > 0; c’ = 0
In sands, the tension capacity of a helical anchor is generally assumed to be equal to the compression
capacity provided that the soil above the helix is the same as the soil below the helix in a zone of about 3
helix diameters. Again, for clean, saturated sands, the “cohesion” is normally taken as zero, reducing the
ultimate capacity to:

Page 4-15 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 QH = AH(q’Nq + 0.5γ’BNγ)
Also, because the area of the plate is small, the contribution of the “width” term to ultimate capacity is
also very small and the width term is often ignored leaving:
QH = AH(q’Nq)
DESIGN METHODOLOGY

Figure 4-4 Reported Values of Nq for Deep Foundations in Sands [from Winterkorn & Fang (1983)].

Page 4-16 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Bearing Capacity Factor Curve
for
Cohesionless Soils
100

90

80

70

60
  

DESIGN METHODOLOGY
50

40

30

20

10

0
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44
Angle of Internal Friction, degrees

Figure 4-5 Recommended Bearing Capacity Factor Nq for Deep Screw-Piles and Helical Anchors in Sand.

Mixed Soils φ’ > 0; c’ > 0

The ultimate capacity of a deep screw-pile in mixed-grain soils can be taken from traditional bearing
capacity theory using Equation 5-11:
QH = AH(cNc + q’Nq + 0.5γBNγ)
Note: The term 0.5γ’BNγ is typically ignored for helical piles because the helix plate is small.

Page 4-17 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 MULTI-HELIX SCREW-PILES AND SCREW-ANCHORS – DEEP
INSTALLATION
The ultimate capacity of deep multi-helix screw-piles and screw-anchors depends on the geometry of
the helical section, namely the size and number of helical plates and the spacing between the plates.
As shown in Figure 5-3b and 5-3d, if the spacing of helix plates is close, the capacity is developed from
a zone of failure between the helical plates and from end bearing from the end helix plate (either the
lowest plate for compression loading or the top helix plate for tension loading), i.e., the helix plates
interact with each other. If the spacing of the helix plates is sufficiently large, the capacity is taken as the
sum of the capacity developed from the individual helix plates, i.e., there is no interaction between helix
plates. Also, there is no capacity taken along the shaft between the helix plates.
In the U.S., most manufacturers of screw-piles and helical anchors produce elements with a standard
helix spacing of 3 times the helix diameter. This spacing was originally used by CHANCE® over 30 years
ago and is assumed to allow individual helix plates to develop full capacity with no interaction between
helix plates and the total capacity is taken as the sum of the capacities from each plate as shown in
Figure 5-3a and 5-3c. Most CHANCE® Screw-Piles and Helical Anchors use inter-helix spacing that is
based on the diameter of the lower helix. For example, the distance between a 10 inch (254 mm) and a 12
DESIGN METHODOLOGY

inch (305 mm) helix is three times the diameter of the lower helix, or 10 x 3 = 30 inches (762 mm).
The first section, called the lead or starter, contains the helix plates. This lead section can consist of
a single helix or multi-helices, typically up to four. Additional helix plates can be added, if required,
with the use of helical extensions. Standard helix sizes and projected areas are shown in Table 4-4.
Comprehensive tables of helix projected areas, showing both the full plate area and the area less the
shaft for both square shaft and pipe shaft helical piles, is included in Section 7 of this Manual. The helix
plates are usually arranged on the shaft such that their diameters stay the same size or increase as they
get farther from the pilot point (tip). The practical limits on the number of helix plates per anchor/pile is
usually four to five if placed in a fine-grained soils and six if placed in a coarse-grained or granular soils.
Compression Loading
The ultimate capacity of a multi-helix screw-pile with an inter-helix spacing greater than or equal to 3
(s/B ≥3) is generally taken as the summation of the capacities of the individual plates:
TABLE 4-4 STANDARD HELIX
LEAD SECTION AND EXTENSIONS QM = ∑QH Equation 4-20
DIAMETER AREA where:
in (cm) ft2 (m2)
QM = Total Capacity of a Multi-Helix Screw-Pile/Helical Anchor
6 (15) 0.185 (0.0172) QH = Capacity of an Individual Helix
8 (20) 0.336 (0.0312)
Tension Loading
10 (25) 0.531 (0.0493) As previously noted in soft clays, especially those with high
12 (30) 0.771 (0.0716) Sensitivity, it may be appropriate to reduce the undrained shear
14 (35) 1.049 (0.0974) strength of the undisturbed clay for design of anchors in tension
16 (40) 1.385 (0.1286) to account for some disturbance of the clay as the helical plates
have passed through. This is left to the discretion of the Engineer.
Most of the evidence shows that in uniform soils, the tension
capacity of multi-helix anchors is the same as in compression.
This means that the ultimate capacity of a multi-helix helical
anchor with plate spacing of 3B or more may be taken as the
summation of the capacities of the individual plates:
QM = ∑QH
There is some evidence that shows that in tension the unit capacity of the trailing helix plates is
somewhat less than the leading helix. Engineers may wish to apply a reduction factor to account for this
behavior; of about 10% for each additional helix on the helical anchor.

Page 4-18 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
ROUND SHAFT SCREW-PILES AND HELICAL ANCHORS
Screw-piles and helical anchors are available with both square shaft and round steel pipe shafts. Square
shaft is used for tension applications and also for compression applications when shaft buckling or
bracing is not an issue. Pipe shaft helical piles have become increasingly popular for use in compression
loading for both new construction and remediation or underpinning of existing structures. They may
be either single or multi-helix. Typical round shaft pile diameters range from 2-7/8 inches (73 mm) to
12 inches (305 mm). For the most part, the design is essentially the same as with square shaft screw-
piles as previously described with two simple modifications: 1) some provision is usually made to
include the additional load capacity developed via skin friction by the round shaft; and 2) in tension
loading, the area of the helical plate is reduced to account for the central shaft as shown in Figure
4-9b. In compression loading, the full projected area of the helix plate develops capacity since the pipe
generally plugs with soil.
Typically, the length of the shaft for about one helix diameter above the helix is not included in
calculating shaft resistance due to skin friction. In addition, load capacity due to friction along the pile
shaft is generally mobilized only if the shaft diameter is at least 3 inches (89 mm).

DESIGN METHODOLOGY
Shaft Resistance in Clay φ’ = 0; c’ > 0
In clays, the shaft resistance developed by round shaft screw-piles and helical anchors is considered in
much the same way that shaft resistance in a driven pile develops. In this traditional approach that is
used for many driven piles in clays and available in most textbooks, the available “adhesion” between
the shaft and the clay is obtained as a percentage of the undrained shear strength of the clay. This is the
undrained or “Alpha” method in which:
α = fS/su Equation 4-21
where:
α = Adhesion Factor
fS = Unit Side Resistance
su = Undrained Shear Strength of the Clay

Figure 4-6 Variation in Adhesion Factor with Undrained Shear Strength of Clays [from Canadian Foundation Manual (2006)].

Page 4-19 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 The value of α is usually obtained from any one of a number of published charts and is typically related
to the absolute value of the undrained shear strength of the clay. Figures 4-6 and 4-7 give typical plots
of α vs. undrained shear strength for a number of cases in which fS has been back calculated from actual
pile load tests. Generally it is sufficient to select an average value of α for a given undrained shear
strength for use in design.
The total shaft resistance is then obtained from:
QS = (fS)(π)(d)(L) Equation 4-22
where:
QS = Total Shaft Resistance
d = Diameter of Central Shaft
DESIGN METHODOLOGY

Figure 4-7 Variation in Adhesion Factor with Undrained Shear Strength of Clays (from Murthy 2003).

Figure 4-8 Variation in Adhesion Factor from American Petroleum Institute [from ASCE (1993b)].

Page 4-20 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN METHODOLOGY
Individual Bearing and Skin Friction Models for Helical Piles with Round (Pipe) Shafts
Figure 4-9

L = Length of Round Shaft in Contact with Soil

The design line given by the American Petroleum Institute (API) shown Figure 4-10 may also be used in
which:
For su < 500 psf; α = 1.0
For su > 1500 psf; α = 0.5
For 500 psf < su < 1500 psf; α varies linearly between 1.0 and 0.5
The shaft resistance should only be calculated for that portion of the shaft length that is in full contact
with the soil. This will depend on the length of the lead section, the design of the shaft couplings that
connect the pile sections, and the type of soil. For example, flanged and bolted connections generally
create an annulus between the shaft and the soil as the pile or anchor is installed as shown in Figure
4-9. This is because the coupling, being larger than the shaft, displaces and compacts soil. Generally, the
length of the central shaft between couplings is not considered to develop shaft resistance unless the
disturbed soil moves back against the shaft, or sufficient time is allowed for the soil to recover. In this
situation, reduced shear strength should be used for shaft resistance capacity.
On the other hand, in the case of true flush connections between extension sections, the entire shaft may

Page 4-21 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 TABLE 4-5 VALUES OF UNIT SIDE RESISTANCE FOR STEEL PILES IN SAND
(FROM NAVY MANUAL DM-7)
Friction Angle of Soil φ’
s’vo
20 25 30 35 40
(psf)
Unit Side Resistance fS (psf)
500 137 175 217 263 315
1000 273 350 433 525 629
1500 410 524 650 788 944
2000 546 700 866 1050 1259
2500 683 875 1082 1313 1574
3000 819 1049 1300 1575 1888
3500 956 1244 1516 1838 2203
4000 1092 1399 1732 2101 2517
DESIGN METHODOLOGY

develop side resistance.

Shaft Resistance in Sand and Mixed Soils φ’ > 0; c’ = 0
The shaft resistance of steel pipe shaft piles in coarse-grained soils, such as sands and mixed soils is
more complex than in clays but can still be determined using traditional deep foundation analyses. The
Department of Navy Design Manual DM-7 also gives a simplified method for estimating the unit side
resistance for straight shaft steel piles. The value of fS is related to the friction angle of the soil, φ’, and
the effective vertical stress, σ’vo, as given in Table 4-5.

HELICAL ANCHOR/PILE SPACING & MINIMUM DEPTH

Reasonability Check
Consideration should be given to the validity of the values obtained when determining the bearing
capacity and shaft resistance of the soil. The calculated theoretical ultimate capacity is no better than
the data used to obtain that value. Data from soils reports, boring logs, the water table depth, and
load information may not accurately represent actual conditions where the helical pile/anchor must
function. Empirical values that are used and estimates of strength parameters, etc. that must be made
because of lack of data affect the calculated bearing capacity and shaft resistance value. In those
situations where soil data is insufficient or not available, a helical trial probe pile can help determine
such items as, location of bearing strata, pile capacity, location of soft/loose soil, and the presence of
obstructions, such as, cobbles, boulders, and debris.
An important step in the process of determining the capacity of a helical pile/anchor is to conduct
a reasonability check. The engineer should use the best engineering judgment to perform the
reasonability check. This should be based on experience, historical test data and consulting colleagues.
This is easily overlooked but must be performed by the designer or by others.
Helical Pile/Anchor Spacing
Once the capacity of the helical pile/anchor is determined, concern may turn to location of the
foundation element with respect to the structure and to other helical pile/anchors. It is recommended
that the center-to-center spacing between adjacent anchors/piles be no less than five times the
diameter of the largest helix. The minimum spacing is three feet (0.91 m). This latter spacing should
be used only when the job can be accomplished no other way and should involve special care during
installation to ensure that the spacing does not decrease with depth. Minimum spacing requirements
apply only to the helix bearing plate(s), i.e., the pile/anchor shaft can be battered to achieve minimum

Page 4-22 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
spacing. Spacing between the helical anchors/piles and other foundation elements, either existing or
future, requires special consideration and is beyond the scope of this section.
Group effect, or the reduction of capacity due to close spacing, has never been accurately measured
with helical piles. However, bearing capacity theory would indicate that capacity reduction due to group
effect is possible, so it’s considered good practice to install helical piles into dense bearing stratum when
center-to center spacing is less than 4 feet (1.2 m).
Minimum Depth
As mentioned earlier, the minimum embedment depth recommended by Hubbell Power Systems, Inc.
for a helical deep foundation is five helix diameters (5D), where D is the diameter of the largest helix.
The 5D depth is the vertical distance from the surface to the top-most helix. Standard practice is to
locate the top-most helix 6D to 8D vertical below the ground surface where practical. Minimum depth
is also a function of other factors, such as seasonally frozen ground, “active” zones (depth of wetting)
and depth of compressive soils. These factors are generally related to seasonal variations to soil strength
parameters, but can also be related to long-term conditions, such as periods of drought or extended
wet conditions. The minimum embedment depth recommended by Hubbell Power Systems, Inc. for
a helical deep foundation due to seasonal variations is three diameters (3D) below the depth of soil

DESIGN METHODOLOGY
where these seasonal variations will occur. For example, frost depths may require embedment depths
that exceed the 5D minimum, depending on the project location. ICC-ES Acceptance Criteria AC358 has
specified a minimum depth for helical tension anchors. AC358 states that for tension applications, as a
minimum, the helical anchor must be installed such that the minimum depth from the ground surface to
the uppermost helix is 12D, where D is the diameter of the largest helix. This disparity between minimum
depth requirements can be reconciled by reviewing published literature on the subject, or by performing
load tests.
Critical Depth
In granular soils, helical pile capacity is a function of both angle of internal friction (φ) and vertical
effective overburden stress. Therefore, as a helical pile is extended deeper into soil, theoretical methods
predict that the pile capacity would increase without limit as the effective vertical stress increases with
increasing depth. In reality, there may be a critical depth where any further increase in depth results
in only a small increase in the bearing capacity of the helical pile. Critical depth for helical piles is best
determined by an experienced foundation engineer. Hubbell Power Systems, Inc. recommends critical
depths of 20D to 30D be used in loose saturated soils at deep depth, where D is the diameter of the
largest helix plate. The 20D to 30D length is the depth into a suitable bearing stratum, and is not
necessarily measured from the ground surface.

TABLE 4-6 SOIL PROPERTIES REQUIRED FOR HELICAL PILE/ANCHOR/PILE

DESIGN FOR VARIOUS SITE CONDITIONS
Required Soil Properties
Unsaturated Fine-Grained,
Soil Property Category Saturated Fine-Grained Coarse-Grained
Mixed Soils
Shear Strength su φ' c', φ'

Unit Weight γsat γwet or γbuoy γwet

Page 4-23 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 4.4 EVALUATING SOIL PROPERTIES FOR DESIGN
The design of helical piles/anchors using the traditional soil mechanics approach described in the
previous section requires evaluation of soil properties for input into the various bearing and friction
capacity equations. Table 6-6 summarizes the soil properties for different site conditions for design of
both single-helix and multi-helix helical piles/anchors.
Geotechnical design of helical piles/anchors requires information on the shear strength of saturated
fine-grained soils, i.e., undrained shear strength, su, and the drained friction angle of coarse-grained
soils, φ’. The best approach to evaluating these properties for design is a thorough site investigation and
laboratory testing program on high quality undisturbed samples. However, this is not always possible
or practical and engineers often rely on information obtained from field testing, such as the Standard
Penetration Test (SPT). Whenever possible, other high quality field tests, such as Field Vane Tests (FVT),
Cone Penetration Tests (CPT), Piezocone Tests (CPTU), Dilatometer Tests (DMT), Pressuremeter Tests
(PMT) or Borehole Shear Tests (BST) are preferred. THERE IS NO SUBSTITUTE FOR A SITE SPECIFIC
GEOTECHNICAL INVESTIGATION.
Estimating Undrained Shear Strength, su, in clays:
The undrained shear strength of saturated clays, silty clays and clayey silts is not a unique soil property,
DESIGN METHODOLOGY

like Liquid Limit of clay content, but depends on the test method used for the measurement. Correlations
are available for estimating undrained shear strength from the results obtained from several of the field
tests noted above. The most common field results that may be available to engineers for design of helical
piles/anchors are the SPT and CPT/CPTU.
su from SPT
A number of correlations exist for estimating both the undrained shear strength and unconfined
compressive strength, qu, of fine-grained soils from SPT results. Several of these correlations are given
in Tables 4-7 and 4-8. The undrained shear strength is generally taken as one-half the unconfined
compressive strength. Caution should be used when using these correlations since they have been
developed for specific geologic deposits and the SPT field procedure used may not have been the same
in all cases.
su from CPT/CPTU
The undrained shear strength may also be estimated from the tip resistance obtained from the total cone
tip resistance from a CPT or the effective (net) cone tip resistance from a CPTU (e.g., Lunne et al. 1995).
Estimating su from the CPT total tip resistance is from a form of the bearing capacity equation as:

su = (qc – σvo)/Nk Equation 4-23

where:
qc = CPT tip resistance
σvo = total vertical stress at the cone tip = depth x total soil unit weight
Nk= empirical cone factor
The value of Nk varies somewhat with soil stiffness, plasticity, stress history and other factors, however
many reported observations where su has been obtained from both laboratory triaxial tests and field vane
tests suggest that a reasonable value of Nk for a wide range of soils is on the order of 16.
Estimating su from the CPTU effective tip resistance uses a modified approach since the tip resistance is
corrected for pore pressure effects to give the effective tip resistance, qt, as the undrained shear strength
is obtained from:
su = (qt – σvo)/Nkt Equation 4-24
where:
qt = CPTU effective tip resistance
Nkt= empirical cone factor

Page 4-24 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
TABLE 4-7. REPORTED CORRELATIONS BETWEEN SPT N-VALUE
AND UNDRAINED SHEAR STRENGTH, SU
Correlation to Undrained
Units of su Soil Type Reference
Shear Strength
su = 29N0.72 kPa Japanese cohesive soils Hara et al. (1974)
Insensitive Overconsolidated
su = 4.5N tsf Stroud (1974)
Clays in U.K.
su = 8N N < 10
su = 7N 10 <N< 20 Guabirotuba
kPa Tavares (1988)
su = 6N 20 <N< 30 Clay
su = 5N 30 <N< 40
su =1.39N + 74.2 tsf tropical soil Ajayi & Balogun (1988)
su = 12.5N kPa Sao Paulo
Decourt (1989)
su = 10.5N60 tsf overconsolidated clay

Note: 1 kPa = 20.9 psf

DESIGN METHODOLOGY
TABLE 4-8. REPORTED CORRELATIONS BETWEEN SPT N-VALUE
AND UNCONFINED COMPRESSIVE STRENGTH, QU
Correlation to Unconfined Compressive
Units of qu Soil Type Reference
Strength
qu = 12.5N kPa Fine-Grained Terzaghi & Peck (1967)
qu = N/8 tsf Clay Golder (1961)
qu = 25N kPa Clay
Sanglerat (1972)
qu = 20N kPa Silty Clay
qu = 25N Highly Plastic Clay
qu = 15N kPa Medium Plastic Clay Sowers (1979)
qu = 7.5N Low Plasticity Clay
qu = 24N kPa Clay Nixon (1982)
qu = 62.5 (N-3.4) kPa Sarac & Popovic (1982)
Behpoor & Ghahramani
qu = 15N kPa CL and CL-ML
(1989)
qu = 58N0.72 kPa Fine-Grained Kulhawy & Mayne (1990)
qu = 13.6 N60 CH
qu = 9.8N60 CL
kPa Sivrikaya & Togrol (2002)
qu = 8.6N60 Fine-Grained
qu = (0.19PI + 6.2)N60 Fine-Grained

The value of Nkt also has been shown to vary for different soils but a reasonable conservative value for
massive clays is on the order of 12. For very stiff, fissured clays, the value of Nkt may be as high as 30.
Other methods are available for estimating undrained shear strength from the pore pressure
measurements from a CPTU or by first estimating the stress history from CPT/CPTU results and then
converting to undrained shear strength, e.g., NCHRP (2007); Schnaid (2009), both of which are viable
approaches.

Page 4-25 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Estimating Shear Strength of Fine-Grained Soil – Other Methods
Vane Shear Test:
Shear strength of fine-grained soils may be measured both in the field and in the laboratory. One of the
most versatile devices for investigating undrained shear strength and sensitivity of soft clays is the vane
shear test. It generally consists of a four-bladed rectangular vane fastened to the bottom of a vertical
rod. The blades are pressed their full depth into the clay surface and then rotated at a constant rate by
a crank handle. The torque required to rotate the vane is measured. The shear resistance of the soil can
be computed from the torque and dimensions of the vane.
One such type of the portable vane shear test is the Torvane. It is a convenient hand-held device useful
for investigating the strength of clays in the walls of test pits in the field or for rapid scanning of the
strength of Shelby tubes or split spoon samples. A calibrated spring allows undrained shear strength
(cohesion) to be read directly from the indicator.
Pocket Penetrometer Test:
Another device used to estimate undrained shear strength in the laboratory or the field is the Pocket
Penetrometer. As with the vane shear test, the pocket penetrometer is commonly used on Shelby
tube and split spoon samples, and freshly cut test pits to evaluate the consistency and approximate
DESIGN METHODOLOGY

unconfined compressive strength (qu) of clay soils. The penetrometer’s plunger is pushed into the soil
¼” and a reading taken on the sliding scale on the side. The scale is a direct reading of shear strength.
Pocket Penetrometer values should be used with caution. It is not recommended for use in sands or
gravel soils.
Unconfined Compression Test:
The unconfined compression (UC) test is used to determine the consistency of saturated clays and
other cohesive soils. A cylindrical specimen is set up between end plates. A vertical load is applied
incrementally at such a rate as to produce a vertical strain of about 1 to 2% per minute – which is rapid
enough to prevent a volume change in the sample due to drainage. The unconfined compressive
strength (qu) is considered to be equal to the load at which failure occurs divided by the cross-sectional
area of the sample at the time of failure. In clay soils where undrained conditions are expected to be
the lower design limit (i.e. the minimum Factor of Safety), the undrained shear strength (i.e., cohesion)
governs the behavior of the clay. This undrained shear strength is approximately equal to ½ the
unconfined compressive strength of undisturbed samples (see Laboratory Testing of Recovered Soil
Samples in Section 2 of this Technical Manual).
The consistency of clays and other cohesive soils is usually described as soft, medium, stiff, or hard.
Tables 4-9 and 4-10 can be found in various textbooks and are reproduced from Bowles, 1988. Values
of consistency, overconsolidation ratio (OCR), and undrained shear strength (cohesion) empirically
correlated to SPT N-values per ASTM D 1586 are given in Table 4-9. It should be noted that consistency
correlations can be misleading because of the many variables inherent in the sampling method and the
soil deposits sampled. As such, Table 4-9 should be used as a guide.
The relative density of sands, gravels, and other granular soils is usually described as very loose, loose,
medium dense, dense, very dense, or extremely dense. The standard penetration test is a good measure
of granular soil density. Empirical values for relative density, friction angle and unit weight as correlated
to SPT “N” values per ASTM D 1586 are given in Table 5-10. It should be noted that SPT values can
be amplified in gravel because a 1”+ gravel particle may get lodged in the opening of the sampler.
This can be checked by noting the length of sample recovery on the soil boring log (see Table 2-6). A
short recovery in gravelly soils may indicate a plugged sampler. A short or “low” recovery may also be
indicated by loose sand that falls out of the bottom of the sampler during removal from the borehole.

Estimating Friction Angle, φ’, in sands

Results from both the SPT and CPT may be used to estimate the drained friction angle of sands and
other coarse-grained soils. Generally, most site investigations involving coarse-grained soils will include
the use of either the Standard Penetration Test (SPT) or the Cone Penetrometer (CPT).

Page 4-26 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
φ’ from SPT
Several correlations have been proposed to estimate the drained friction angle in sands from SPT
results. A summary of several of the more popular correlations are given in Table 4-11. The correlation of
Hatanaka & Uchida (1996) is shown in Figure 4-10, taken from FHWA Reference Manual on Subsurface
Investigations (2002).

TABLE 4-9. TERMS TO DESCRIBE CONSISTENCY OF SATURATED COHESIVE SOILS

Consistency SPT N60- Undrained Shear Strength
Stress History Comments
Term Values skf (kPa)
Normally Consolidated
Very Soft 0-2 <0.25 (12) Runs through fingers.
OCR = 1
Normally Consolidated
Soft 3-5 0.38 (18.2) to 0.63 (30.2) Squeezes easily in fingers.
OCR @ 1 – 1.2
Normally Consolidated
Medium 6-9 0.75 (36) to 1.13 (54.1) Can be formed into a ball.
OCR = 1 to 2
Normally Consolidated to Hard to deform by hand
Stiff 10 - 16 1.25 (59.9) to 2 (95.8)

DESIGN METHODOLOGY
OCR of 2-3. squeezing.
Overconsolidated
Very Stiff 17 - 30 2.13 (102) to 3.75 (179.6) Very hard to deform by hand.
OCR = 4 – 8
Highly Overconsolidated Nearly impossible to deform
Hard >30 >3.75 (179.6)
OCR > 8 by hand.

φ’ from CPT/CPTU
A similar approach may be used to estimate the friction angle of sands from the CPT/CPTU tip resistance
based on a modified bearing capacity theory. Robertson and Campanella (1983) summarized a number
of available calibration chamber tests on five sands and suggested a simple correlation between the
normalized CPT tip resistance and a cone bearing capacity factor, Nq as:

Nq = (qc/sv0’) = 0.194exp(7.63tanφ’) Equation 4-26

where:

σv0’ = vertical effective (corrected for pore water pressure) stress at cone tip

This relationship is shown in Figure 4-14.

The friction angle may also be estimated from the effective tip resistance from the CPTU. Early
calibration chamber data suggested a simple empirical correlation as:

φ’ = arctan[0.1 + 0.38 log (qt/σ’vo)] Equation 4-27

Equation 4-27 is shown in Figure 4-16.

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 TABLE 4-10. EMPIRICAL VALUES FOR DR, FRICTION ANGLE AND UNIT WEIGHT VS SPT (AS-
SUMING A 20 FT (6 M) DEPTH OF OVERBURDEN AND 70% ROD EFFICIENCY ON HAMMER)
Description Very Loose Loose Medium Dense Very Dense
Relative Density (Dr) (%) 0 15 35 65 85
Fine 1-2 3-6 7-15 16-30 ?
SPT (N70) Medium 2-3 4-6 8-20 21-40 40+
Coarse 3-6 5-9 10-25 26-45 45+
Fine 26-28 28-30 30-33 33-38 38+
Friction Angle (f) Medium 27-29 29-32 32-36 36-42 50+
Coarse 28-30 30-34 34-40 40-50 50+
Total Unit Weight (gwet) (PCF) 70-100 90-115 110-130 110-140 130-150

Additional test results from 24 different sands were compiled by Kulhawy and Mayne (1990) who pro-
posed the following expression:
DESIGN METHODOLOGY

φ’ = 17.70 + 11.0 log (qt1) Equation 4-28

where:
(qt1) = (qt/σatm)/(σ’vo/σatm)0.5
σatm = atmospheric pressure (1 atm = 1 bar = 100 kPa = 1tsf = 14.7 psi)

TABLE 5-11. REPORTED CORRELATIONS BETWEEN

SPT N-VALUE AND Φ’ FOR COARSE-GRAINED SOILS
Correlation Reference
φ’ = (0.3N)0.5 + 270 Peck et al. (1953)
φ’ = (10N)/35 + 270 Meyerhof (1956)
φ’ = (20N)0.5 + 150 Kishida (1967)
φ’ = (N/s’vo)0.5 +26.90
Parry (1977)
(s’vo in MN/m2)
φ’ = (15N)0.5 +150 Shioi & Fukui (1982)
φ’ = (15.4(N1)60)0.5 + 200 Hatanaka & Uchida (1996)

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 DESIGN METHODOLOGY
Figure 4-10 Peak Friction Angle of Sands from SPT Resistance - Correlation of Hatanaka & Uchida (1996)
from FHWA Reference Manual on Subsurface Investigations (2002)

Figure 4-11

Page 4-29 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Direct Estimate of Unit Shaft Resistance, fs, of Steel Round Shaft Piles and Grouted Helical Micropiles
Suggestions for estimating the unit side resistance, fs, of deep foundations in a variety of soils have
been presented. This approach is convenient for helical piles/anchors and reduces assumptions in first
estimating shear strength and then estimating other factors to obtain fs. Poulos (1989) summarized a
number of reported correlations between pile unit side resistance and SPT N-value and suggested that
most of these correlations could be expressed using the general equation:
fs = β + αN Equation 4-29
Lutenegger (2011) presented a summary of more-or-less “global” reported correlations between SPT
N-values and unit side resistance friction for both driven and bored piles in a number of different soil
materials and shown in Table 4-12.
DESIGN METHODOLOGY

Figure 4-12. Relationship between Bearing Capacity Number and Friction Angle from Normalized CPT Tip Resistance – from
Robertson and Campanella (1983)

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 DESIGN METHODOLOGY
Figure 4-13. Relationship Between Relative Density for Normally Consolidated (NC) and Over Consolidated (OC) Sands from CPT Data.

Figure 4-14. Relationship Between Friction Angle and the Effective Tip Resistance from CPTU Data

(N1)60 = N60/(σ‘vo)0.5 σ‘vo = effective overburden stress in tsf

Page 4-31 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Engineers might ask “Why should the SPT N-value correlate to pile side resistance?” Other than being
purely coincidental, there must be a rational and logical explanation for such observations. The range
in reported values of α given in Table 4-12 is quite large and the results might seem of limited use.
Nonetheless, we can make some general observations and summarize these observations: 1) For most
of these correlations, the value of β is very low and for practical purposes may be reasonably taken as
zero with little effect on the correlation, which simplifies Eq. 5-29 to:
fs = αN Equation 4-30
2) The value of α ranges from 0.3 to 12.5; 3) The observations presented in Table 4-12 generally suggest
higher values of α for fine-grained soils as compared to coarse-grained soils; and 4) Values of α are
generally higher for driven piles as compared to bored piles.
The values of α vary considerably for a number of obvious reasons, deriving from both the pile data
as well as the SPT data. In regard to the pile data: 1) The data represent a wide range of pile types, i.e.,
different geometry, such as open and closed end pipe, H-Piles and construction practices; such as dry
bored vs. wet bored as well as pile size, pile plugging, L/d, and other factors; 2) Different methods may
have been used to interpret the ultimate capacity and to isolate the side resistance from end bearing;
3) The unit side resistance from pile tests is typically averaged over the length of the pile except in
DESIGN METHODOLOGY

the case of well instrumented piles. Regarding the SPT data:1) The results most likely represent a wide
range in field practice including a wide range in energy or hammer efficiency; 2) It is likely that other
variations in field practice or equipment such as spoon geometry are not consistent among the various
studies and may affect results. Engineers should use the correlations in Table 4-12 with caution.
In fact, Equation 4-30 is similar to Equation 4-21, suggesting a correlation between SPT N-values and
undrained shear strength (su) in fine-grained soils.

FACTOR OF SAFETY
The equations discussed above are used to obtain the ultimate capacity of a helical anchor/pile. For
working, or allowable stress design (ASD), an appropriate Factor of Safety must be applied to reduce
the ultimate capacity to an acceptable design (or working) capacity. The designer determines the
Factor of Safety to be used. In general, a minimum Factor of Safety of 2 is recommended. For tieback
applications, the Factor of Safety typically ranges between 1.25 and 2.
Design or working loads are sometimes referred to as unfactored loads and do not include any Factor
of Safety. They may arise from dead loads, live loads, snow loads and/or earthquake loads for bearing
(compression) loading conditions; from dead loads, live loads, snow loads and/or wind loads for anchor
loading conditions; and earth pressure, water pressure and surcharge loads (from buildings, etc.) for
helical tieback or Soil Srew® earth retention conditions.
Ultimate loads, sometimes referred to as fully factored loads, already fully incorporate a Factor
of Safety for the loading conditions described above. Hubbell Power Systems, Inc. recommends a
minimum Factor of Safety of 2.0 for permanent loading conditions and 1.5 for temporary loading
conditions. This Factor of Safety is applied to the design or working loads as defined above to achieve
the ultimate load requirement. National and local building code regulations may require more stringent
Factors of Safety on certain projects.
Most current structural design standards in Canada use a Limit States Design (LSD) approach for
the structural design of helical piles/anchors rather than working or allowable stress design (ASD).
All specified loads (dead, live, snow, wind, seismic, etc.) are factored in accordance with appropriate
load factors and load combinations should be considered. In addition, the geotechnical resistance of
the helical pile/anchor must be factored. Geotechnical resistance factors for helical piles/anchors are
not yet clearly defined. Therefore, a rational approach should be taken by the designer and resistance
factors should be considered that are suitable to specific requirements.

Page 4-32 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
TABLE 4-12. REPORTED CORRELATIONS BETWEEN SPT N-VALUE AND
PILE SIDE RESISTANCE (FROM LUTENEGGER 2011)
Pile Type Soil β α Reference
granular 0 2.0 Meyerhof (1976)
miscellaneous soils
10 3.3 Decourt (1982)
.(fs < 170 kPa)
cohesive 0 10 Shioi & Fukui (1982)
driven
displacement cohesive 0 3 Bazaraa & Kurkur
cohesionless 0 1.8 (1986)
sandy 29 2.0
Kanai & Yubuuchi (1989)
clayey 34 4.0
misc 0 1.9 Robert (1997)
granular 0 1.0 Meyerhof (1976)
granular 55 5.8 Fujita et al. (1977)
cohesionless 0 3.3 Wright & Reese (1979)

DESIGN METHODOLOGY
cohesive (fs < 170 kPa) 10 3.3 Decourt (1982)
cohesive 0 5.0 Shioi & Fukui (1982)
cohesive 0 1.8
Bazaraa & Kurkur (1986)
cohesionless 0 0.6
residual soil & weathered
0 2.0 Broms et al. (1988)
rock
clay 0 1.3
Koike et al. (1988)
sand 0 0.3
35 3.9
sandy soil cohesive Kanai & Yubuuchi (1989)
24 4.9
bored
residual soil 0 4.5 Winter et al. (1989)
gravel 0 6.0
sand 0 4.0
Hirayama (1990)
silt 0 2.5
clay 0 1.0
residual soils 0 2.0 Chang & Broms (1991)
clayey soil 0 10.0
Matsui (1993)
sandy soil 0 3.0
17.3 1.18
misc. Vrymoed (1994)
18.2 0.65
misc. 0 1.9 Robert (1997)
sand 0 5.05 Kuwabara & Tanaka (1998)
weathered rock 0 4 Wada (2003)
cohesionless 0 5.0 Shoi & Fukui
cohesive 0 10.0 (1982)

cast-in-place cohesionless 30 2.0

(fs < 200 kPa)
Yamashita et al.(1987)
cohesive
(fs < 150 kPa) 0 5.0
Note: fs =β + αN (fs in units of kPa)

Page 4-33 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 HELICAP® HELICAL CAPACITY DESIGN SOFTWARE
Hubbell Power Systems, Inc. engineers developed HeliCAP® design software to determine the bearing
capacity of helical piles and anchors in soil. Since then, it has been revised several times to provide
additional features such as side resistance for steel pipe piles and grouted shaft helical piles. HeliCAP®
software is available to engineers and designers upon request. The software uses the same theory of
general bearing capacity as presented in Section 4.3 for deep foundations (minimum depth ≥ 5D). A
key feature of HeliCAP is it’s designed to work with the information commonly available from soils
reports. In North America, soil investigation usually includes a soil boring as described in Section 3 of
this technical design manual. The most common information available from the soils boring is the soil
profile, groundwater location, and SPT blow count data per ASTM D-1586. As such, HeliCAP includes
blow count correlations for shear strength, angle of internal friction, and unit weight. These correlations
are generally accepted as reasonable approximations given the available blow count data.
The following equations, factors, empirical values, etc., presented in this section are the algorithms used
in the HeliCAP v2.0 Helical Capacity Design Software. This program makes the selection of a helical
anchor/pile much quicker than making hand calculations. It allows calculations to be made quickly while
varying the different parameters to arrive at the most appropriate solution. As with any calculations, the
DESIGN METHODOLOGY

results from this program are no better than the input data used to generate them.
The program will assist in determining an appropriate helical lead configuration and overall anchor/pile
length. It also provides an estimate of the installation torque. The helical lead configuration can vary by
the number and sizes of helix plates required to develop adequate capacity. Helical anchor/pile length
may vary due to the combined effects of the lead configuration and soil strength. Generally speaking,
the shorter the pile length for a given load, the better the performance will be in regard to deflection
under load.

Helicap® Bearing Capacity Methodology

As detailed earlier in this section, the Individual Plate Bearing Method states the capacity of a single
or multi-helix anchor/pile is determined by summing the bearing capacity of the individual helix plate
elements specific to a given pile. Thus:
Qt = SQh
where:
Qt = Total ultimate multi-helix anchor/pile capacity
Qh = Individual helix capacity
HeliCAP determines the ultimate bearing capacity of an individual helix as per the following equation.
An upper limit for this capacity is based on helix strength that can be obtained from the manufacturer.
See Section 7 of this technical design manual for the mechanical strengths of helix plates.

Qh = Ah (cNc + q’Nq) ≤ Qs Equation 4-31

where:
Ah = Projected helix area
Qs = Capacity upper limit, determined by the helix mechanical strength

Page 4-34 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Sands φ’ > 0; c’ = 0

HeliCAP® determines the ultimate bearing capacity in a non-cohesive sand or gravel soil with Equation
4-32 in which the fine-grain (clay) term has been eliminated.
The bearing capacity factor Nq is dependent on the angle of internal friction (φ’) of the non-cohesive
sand or gravel soil. When a value is provided for the friction angle, HeliCAP uses Figure 4-7 (Nq vs φ’
) and Equation 4-19 to determine the value for Nq. When the angle of internal friction is not known,
HeliCAP estimates it (and Nq) by using blow counts obtained from the Standard Penetration Test per
ASTM D 1586. Equation 4-33 allows an estimate of the angle of internal friction from SPT blow count
data. This equation is based on empirical data given by Bowles (1968) and its results should be used
with caution. The graph in Figure 4-7 allows the determination of Nq for a specific angle of internal
friction when measured in degrees. This curve was adapted from work by Meyerhof (1976). Equation 4-19
was written for the curve shown in Figure 4-7, which is Myerhof’s Nq values divided by 2 for long term
applications. Note the correlated φ’ and Nq values determined by HeliCAP® can be overridden. This is
encouraged when more reliable soil data are available.
Qh = Ahq’Nq = Ah γ‘DNq Equation 4-32

DESIGN METHODOLOGY
where:
Ah = Projected helix area
D = Vertical depth to helix plate
Nq = Bearing capacity factor for non-cohesive component of soil
γ‘ = Effective unit weight of the soil

φ’ = 0.28 N + 27.4 Equation 4-33

where:
φ’ = Angle of internal friction
N = Blow count per ASTM D 1586 Standard Penetration Test

Fine-Grain Cohesive Soil, φ’ = 0; c’ > 0

HeliCAP determines the ultimate bearing capacity in a cohesive or fine-grained soil with Equation 4-17
with the overburden term not used. The Nc factor is 9, provided the installation depth below grade is
greater than five times the diameter of the top most helix.

Qh = AhcNc = AH[(9)(su)] Equation 4-34

where:
Ah = Projected helix area
c = “cohesion”; for φ’ = 0; c = undrained shear strength = su
Nc = Bearing Capacity Factor for Deep Failure = 9 (minimum depth ≥ 5D)

Page 4-35 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 In the event that cohesion or undrained shear strength values are not available, HeliCAP® uses the
following equation to obtain estimated undrained shear strength values when blow counts from ASTM D
1586 Standard Penetration Tests are available. This equation is based on empirical values and is offered
only as a guide when undrained shear strength values are otherwise not available. It is suggested that
results be used with caution. (NOTE: The correlated undrained shear strength values determined by
HeliCAP® can be overridden. This is encouraged when more reliable soil data are available.)
c (ksf) = N / 8 or = 0.125(N) Equation 4-35

c (kPa) = 6N
where:
c = “cohesion”; for φ’ = 0; c = undrained shear strength = su
N = Blow count value per ASTM D 1586 Standard Penetration Test

Unit Weight Correlation

DESIGN METHODOLOGY

In the event unit weight values are not available, HeliCAP® uses the following equations to obtain
estimated unit weight values when blow counts from ASTM D 1586 Standard Penetration Tests are
available.

Clay (Fine-Grain) Soils: Equation 4-36

N > 0 & N ≤ 19: γ = 80 + (2N) (lb/ft3)
N ≥ 20 & N ≤ 40 γ = 120 (lb/ft3)

N ≥ 41 & N < 50 γ = 120 + 2(N-40) (lb/ft3) Equation 4-37

N ≥ 50 γ = 140 (lb/ft3)

Sand (Coarse-Grain) Soils:

N = 0 γ = 65 (lb/ft3)

N > 0 & N ≤ 7 γ = 60 + 5N (lb/ft3) Equation 4-38

N ≥ 8 & N ≤ 10 γ = 100 (lb/ft3)

N ≥ 11 & N < 50 γ = 90 + N (lb/ft3) Equation 4-39

N ≥ 50 γ = 140 (lb/ft3)

These correlations were originally determined from Tables 3-2 and 3-3 in Bowles first edition of
Foundation Analysis and Design. These relationships provide an approximation of the total unit weight.
They have been modified slightly from how they were originally presented as experience has suggested.
(NOTE: The correlated total unit weight values determined by HeliCAP® can be overridden. This is
encouraged when more reliable soil data are available.)

Page 4-36 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Mixed Soils φ’ > 0; c’ > 0
The determination of the bearing capacity of a mixed soil, one that exhibits both cohesion and friction
properties, is accomplished by use of Equation 4-31. This is fairly uncomplicated when accurate values
are available for both the cohesion (undrained shear strength) and friction terms (φ’ & γ’) of the equation.
It is not possible to use ASTM D 1586 Blow Count correlations to determine all soil strength variables
in the bearing capacity equation. Therefore, unless the designer is quite familiar with the project soil
conditions, it is recommended that another approach be taken when accurate values are not available for
both terms of the equation.
One suggestion is to first consider the soil as fine-grained (cohesive) only and determine capacity. Then
consider the same soil as coarse-grained (cohesionless) only and determine capacity. Finally, take the
lower of the two results and use that as the soil bearing capacity and apply appropriate Factors of
Safety, etc.

Helicap® Shaft Resistance Methodology

As discussed earlier in this section, the shaft resistance developed by pipe shaft or grouted shaft screw-
piles is considered in much the same way that shaft resistance in a driven pile develops. HeliCAP® uses

DESIGN METHODOLOGY
this traditional approach that is available in most foundation design textbooks.

The general equation is:

Qf = Σ[π(D)fs(∆Lf)] Equation 4-40

where:

D = Diameter of steel or concrete pile column

fs = Sum of friction and adhesion between soil and pile
∆Lf = incremental pile length over which πD and fs are taken as constant

HeliCAP® uses two empirical methods to calculate shaft resistance - the Gouvenot Method and the
US Department of Navy Method. The Gouvenot Method is named after the French researcher; who
conducted tests on a variety of grouted shaft micropiles including gravity fed grout columns. HeliCAP®
uses the Gouvenot method to calculate shaft resistance for grouted columns only (Helical Pulldown®
micropiles). The US Navy method uses the Dept. of Navy Design Manual 7, Soil Mechanics, Foundations
and Earth Structures (1974). HeliCAP uses the Navy method to calculate shaft resistance for both
grouted columns and straight steel pipe shafts.

• Gouvenot reported a range of values for skin friction of concrete/grout columns based on a
number of field load tests. The soil conditions are divided into three categories based on friction
angle (f) and cohesion (c). The equations used to calculate fs are:

Type I: Sands and gravels with 35° < φ < 45° and c’ = 0:

fs = σo tan φ Equation 4-41

where: σo = Mean normal stress for the grout column

Type II: Mixed soils; fine loose silty sands with 20° < φ < 30° and sandy clays with
205 psf < C < 1024 psf (9.8 kPa < c < 49 kPa)

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 fs = σo( sin φ) + c(cos φ) Equation 4-42

Type III: Clays with 1024 psf < c < 4096 psf (49 kPa < c < 196 kPa)

fs = c Equation 4-43

where: 1024 psf < c < 2048 pfs (49 kPa < c < 98 kPa)
and:

fs = 2048 psf (98 kPa) Equation 4-44

where: 2048 psf < c < 4096 psf (98 kPa < c < 196 kPa)

In HeliCAP® this analysis assumes a uniform shaft diameter for each soil layer and, if required, the friction
capacity of the pile near the surface can be omitted.

• Department of the Navy Design Manual 7 Method:

DESIGN METHODOLOGY

For cohesive soils (a Method):

Qf = Σ[π(D)Ca(∆Lf)] Equation 4-45

where: Ca = Adhesion factor (See Table 5-13)

For cohesionless soils (a Method):

Qf = Σ[πD(qKtanf)∆Lf] Equation 4-46

where: q = Effective vertical stress on element ∆Lf

K = Coefficient of lateral earth pressure ranging from Ko to about 1.75 depending on volume
displacement, initial soil density, etc. Values close to Ko are generally recommended because of
long-term soil creep effects. As a default, use Ko = 1.
φ = Effective friction angle between soil and plate material

Qf = Σ[πD(S)∆Lf] Equation 4-47

where: S = Average friction resistance on pile surface area = Potanφ (See Tables 5-5 & 5-14)
Po = Average overburden pressure
For straight steel pipe shaft piles in sand, HeliCAP® uses Table 5-5 to calculate shaft resistance in sand
layers using the Alternate Navy Method.

Page 4-38 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Tables 4-13, 4-14 and 4-5 are derived from graphs in the Department of the Navy Design Manual
7, Soil Mechanics, Foundations and Earth Structures (1974). Later editions of this manual limit
the depth at which the average overburden pressure is assumed to increase. The following is an
excerpt from the manual regarding this limiting depth:
“Experimental and field evidence indicate that bearing pressure and skin friction increase with
vertical effective stress (Po) up to a limiting depth of embedment, depending on the relative
density of the granular soil and position of the water table. Beyond this limiting depth (10B±
to 40B±) there is very little increase in end bearing, and increase in side friction is directly
proportional to the surface area of the pile. Therefore, if D is greater than 20B, limit Po at the pile
tip to that value corresponding to D = 20B” where D = depth of the pile embedment over which
side friction is considered and B = diameter of the pile.
HeliCAP® v2.0 Helical Capacity Design Software calculates ultimate capacity and must have an
appropriate Factor of Safety applied to the results. The program has additional features that allow it
to be used for other applications, but it is beyond the scope of this manual to present all facets of the
program. For additional assistance, refer to the Help screen or contact Hubbell Power Systems, Inc.
application engineers.

DESIGN METHODOLOGY
The following screen is from HeliCAP® v2.0 Helical Capacity Design Software. It shows a typical workpage
with the soil profile on the left and helical pile capacity on the right.

Page 4-39 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 4.7 APPLICATION GUIDELINES FOR CHANCE® HELICAL PILES/ANCHORS
• The uppermost helix should be installed at least three diameters below the depth of seasonal
variation in soil properties. Therefore, it is important to check the frost depth or “mud” line at
the project site. Seasonal variation in soil properties may require the minimum vertical depth
to exceed five helix diameters. The influence of the structure’s existing foundation (if any) on
the helical pile/anchor should also be considered. Hubbell Power Systems, Inc. recommends
helical piles/anchors be located at least five diameters below or away from existing foundation
elements.
• The uppermost helix should be installed at least three helix diameters into competent load-
bearing soil. It is best if all helix plates are installed into the same soil stratum.
• For a given shaft length, use fewer longer extensions rather than many shorter extensions. This
will result in fewer connections and better load/deflection response.
• Check economic feasibility if more than one combination of helical pile/anchors helix
configuration and overall length can be used.
TABLE 4-13. RECOMMENDED ADHESION VALUES IN CLAY *
DESIGN METHODOLOGY

PILE TYPE SOIL CONSISTENCY COHESION, c (psf) ADHESION, Ca (psf)

Very Soft 0 – 250 0 – 250
Soft 250 – 500 250 – 480
Concrete Medium Stiff 500 – 1000 480 – 750
Stiff 1000 – 2000 750 – 950
Very Stiff 2000 – 4000 950 – 1300
Very Soft 0 – 250 0 – 250
Soft 250 – 500 250 – 460
Steel Medium Stiff 500 – 1000 460 – 700
Stiff 1000 – 2000 700 – 720
Very Stiff 2000 – 4000 720 - 750
* From Department of the Navy Design Manual 7, Soil Mechanics, Foundations and Earth Structures (1974).

TABLE 4-14. STRAIGHT CONCRETE PILES IN SAND

Effective Angle of Internal Friction (degrees) (γ’)
Po (psf) 20 25 30 35 40
S= Average Friction Resistance on Pile Surface (psf)
500 182 233 289 350 420
1000 364 466 577 700 839
1500 546 699 866 1050 1259
2000 728 933 1155 1400 1678
2500 910 1166 1443 1751 2098
3000 1092 1399 1732 2100 2517
3500 1274 1632 2021 2451 2937
4000 1456 1865 2309 2801 3356

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4.8 LATERAL CAPACITY OF HELICAL PILES
Introduction
The primary function of a deep foundation is to resist axial loads. In some cases they will be subjected
to horizontal or lateral loads. Lateral loads may be from wind, seismic events, live loads, water flow, etc.
The resistance to lateral loads is in part a function of the near surface soil type and strength, and the
effective projected area of the structure bearing against these soils. This section provides a summarized
description of the methods and procedures available to determine the lateral capacity of helical piles/
anchors in soil.
The analysis of deep foundations under lateral loading is complicated because the soil reaction
(resistance) at any point along the shaft is a function of the deflection, which in turn is dependent on
the soil resistance. Solving for the response of a deep foundation under lateral loading is one type of
soil-structure interaction problem best suited for numerical methods on a computer. Square shaft (SS)
helical piles/anchor do not provide any significant resistance to lateral loads. However, Round Shaft (RS)
helical piles/anchor and Helical Pulldown® micropiles can provide significant resistance to lateral loads
depending on the soil conditions. Over the past 7 seven years, there has been considerable research
done on the lateral capacity of grouted shaft helical piles – both with and without casing. Abdelghany &

DESIGN METHODOLOGY
Naggar (2010) and Sharnouby & Naggar (2011) applied alternating cyclic lateral loads to helical piles of
various configurations in an effort to simulate seismic conditions. Their research showed that helical piles
with grouted shafts retain all their axial load capacity after being subjected to high displacement lateral
load.
Lateral Resistance - Methods Used
Most helical piles/anchors have slender shafts [less than 3 inch (89 mm)] that offer limited resistance
to lateral loads when applied to vertically installed shafts. Load tests have validated the concept that
vertical pile foundations are capable of resisting lateral loads via shear and bending. Several methods are
available to analyze the lateral capacity of foundations in soil including: (1) Finite Difference method; (2)
Broms’ Method (1964a) and (1964b); (4) Evans & Duncan (1982) Method as presented by Coduto (2001).
Each of these methods may be applied to round shaft helical piles..
Lateral resistance can also be provided by passive earth pressure against the structural elements of the
foundation. The resisting elements of the structure include the pile cap, grade beams and stem walls. The
passive earth pressure against the structural elements can be calculated using the Rankine Method.
Battered or inclined helical piles/anchors can be used to resist lateral loads by assuming that the
horizontal load on the structure is resisted by components of the axial load. The implicit assumption in
this is that inclined foundations do not deflect laterally, which is not true. Therefore, it is better practice
to use vertically installed helical piles/anchors to resist only vertical loads and inclined helical piles/
anchors to resist only lateral loads. When inclined piles are required to resist both vertical and lateral
loads, it is good practice to limit the pile inclination angle to less than 15°.
Friction resistance along the bottom of a footing, especially in the case of a continuous strip footing or
large pile cap, can be significant. The friction component in a sandy soil is simply the structure’s dead
weight multiplied by the tangent of the angle of internal friction. In the case of clay, cohesion times the
area of the footing may be used for the friction component. When battered piles are used to prevent
lateral movement, the friction may be included in the computation. The designer is advised to use
caution when using friction for lateral resistance. Some building codes do not permit friction resistance
under pile supported footings and pile caps due to the possibility the soil will settle away from the
footing or pile cap. Shrink-swell soils, compressible strata, and liquefiable soil can result in a void under
footings and pile caps.

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 Figure 5-17. Lateral Resistance Methods
DESIGN METHODOLOGY

Finite Difference Method

Several computer programs, such as LPILEPLUS (ENSOFT, Austin, TX) are revisions of the COM624
program (Matlock and Reese) and its predecessor Beam-Column 28 (Matlock and Haliburton) that both
use the p-y concept, i.e., soil resistance is a non-linear function of pile deflection, which was further
developed by Poulos (1973). This method is versatile and provides a practical design method. This is
made possible by the use of computers to solve the governing non-linear, fourth-order differential
equation, which is explained in greater detail on page 4-20. Lateral load analysis software gives
the designer the tools necessary to evaluate the force-deflection behavior of a helical pile/anchor
embedded in soil.
Figures 4-18 and 4-19 are sample LPILEPLUS plots of lateral shaft deflection and bending moment vs.
depth where the top of the pile is fixed against rotation. From results like these, the designer can
quickly determine the lateral response at various horizontal loads up to the structural limit of the
pile, which is typically bending. Many geotechnical consultants use LPILEPLUS or other soil-structure-
interaction programs to predict soil-pile response to lateral loads.

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 Medical Office Bldg. - Portland, CT - RS6625 Medical Office Bldg. - Portland, CT - RS6625
Lateral Deflection (in) Bending Moment (in-kips)

-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 -400 -350 -300 -250 -200 -150 -100 -50 0 50 100 150 200

0
1

1
2

2
3

3
4

4
5

5
6
Depth (ft)

6
Depth (ft)
7

7
8

8
9

9
10

10

DESIGN METHODOLOGY
11

11
12

12
13

13
Case 1 Case 1
Case 2 Case 2
Case 3 Case 3
14

14

Figure 4-16. LPILEPLUS Sample Plot Figure 4-17. LPILEPLUS Sample Plot
Deflection vs Depth Bending Moment vs Depth

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 LPILEPLUS and similar computer programs work well in evaluating a single pile. When designing for
helical piles for larger shear and moment loads it is beneficial to use a pile group modeling computer
program, such as GROUP (ENSOFT, Austin, TX). This program uses similar non-linear functions of pile
deflection but in two and three dimensions over multiple piles in the form of t-z and Q-w curves for
axial loading, p-y curves for lateral loading, and T-q curves for torsional loading. This analysis makes
gives a model of the total pile interaction and the ability to design battered piles while monitoring the
stress and moment imparted on individual piles.
Similar to LPILEPLUS plots of the lateral shaft deflection and bending moment vs. depth are generated
from the software. Figures 4-18 and 4-19 are samples plots of GROUP

Brom’s (1964a & 1964b) Method

Broms’ Method is best suited for applications where the top section of the helical pile/anchor/pile is a
greater diameter than the bottom section. Enlarged top sections are commonly used to increase the
lateral capacity of the foundation shaft. Design Example 7-13 in Section 7 gives an example of this. It uses
Broms’ method for short piers in cohesive soil. A “short” pier is one that is rigid enough that it will move
in the direction the load is tending by rotation or translation. A “long” pier is one that the top will rotate
or translate without moving the bottom of the foundation, i.e., a plastic hinge will form.
DESIGN METHODOLOGY

Broms developed lateral capacity methods for both short and long piles in cohesive and non-cohesive
soil. Broms theorized that a short free-headed pier rotates about a center, above the lower end of the
foundation, without substantial deformation along its axis. The resistance is the sum of the net of the
earth pressures above and the passive earth pressure below the center of rotation. The end bearing
influence or effect is neglected. Likewise, the passive earth pressure on the uppermost 1.5 diameters of
shaft and the active earth pressure on the back of the pile are neglected.
Figure 4-20 is a reaction/shear/moment diagram that demonstrates the Broms theory for laterally
loaded short piles in cohesive soils. A simple static solution of these diagrams will yield the required
embedment depth and shaft diameter of the top section required to resist the specified lateral load. It is
recommended the designer obtain and review Broms’ technical papers (see References at the end of this
section) to familiarize themselves with the various solution methods in both cohesive and non-cohesive
soils. The Broms Method was probably the most widely used method prior to the finite difference and
finite element methods used today and gives fair agreement with field results for short piles.

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 DESIGN METHODOLOGY
Figure 4-20. Broms’ Method for Short Piles in Clay
(Energy Structures, Inc., 1994)

Lateral Capacity By Passive Earth Pressure

Passive earth pressure on the projected area of the pile cap, grade beam, or stem wall can be calculated
by the Rankine (ca. 1857) method, which assumes no soil cohesion or wall-soil friction. One can use
known or assumed soil parameters to determine the sum of the passive earth pressure minus the active
earth pressure on the other side of the foundation as shown in Figure 4-21. The following are general
equations to calculate active and passive pressures on a wall for the simple case on a frictionless vertical
face and a horizontal ground surface. Equations 4-51 and 4-52 are Rankine equations for sand. Equations
4-53 and 4-54 are the addition of the cohesion for clay or cohesive soils. Three basic conditions are
required for validity of the equations:
1. The soil material is homogenous.
2. Sufficient movement has occurred so shear strength on failure surface is completely mobilized.
3. Resisting element is vertical; resultant forces are horizontal.

K0 = 1-sin ф’ Equation 4-48

Ka = tan2 (45-ф’/2) Equation 4-49

Kp = tan2 (45+ф’/2) Equation 4-50

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For granular soil (sand):

Pa = ½KaρH2 Equation 4-51

Pp = ½KpфρH2 Equation 4-52

For cohesive soil (clay):

Pa = ½KarH2 – 2cH + 2c2/фρ Equation 4-53

Pp = ½KpρH2 + 2cH Equation 4-54

where: K0 = Coefficient of earth pressure at rest

Ka = Coefficient of active earth pressure
DESIGN METHODOLOGY

Kp = Coefficient of passive earth pressure

H = Height of wall or resisting element
c = Cohesion
ф’ = Effective stress friction angle of soil
Pa = Active earth pressure
ρ = Unit weight of soil

Equations 4-48 through 4-54 are from NAVFAC Design Manual DM7, Foundations and Earth
Structures (see References at the end of this section).

Table 4-15 is a tabulation of the coefficient for at rest, active, and passive earth pressure for various soil
types, relative densities and consistencies.
TABLE 4-15 COEFFICIENTS OF EARTH PRESSURE (DAS, 1987)
Soil K0, Drained K0, Total Ka, Total Kp, Total
Clay, soft * 0.6 1 1 1
Clay, hard * 0.5 0.8 1 1
Sand, loose 0.6 0.53 0.2 3
Sand, dense 0.4 0.35 0.3 4.6
* Assume saturated clays

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 Using the Rankine solution may be an over-
simplification of the problem but tends to be
conservative since the height of the projected
Grade Beam
area of the footing or pile cap is not large and the
cohesion term will generally be small.
Pp

Pa Batters
Lateral loads are commonly resolved with battered
helical piles and anchors. Battered piles are used
when passive lateral resistance of the surrounding
Soil: Loose Sand
soil is inadequate to transmit the lateral loads
required by a structure, or the greater rigidity of
the foundation is required.
CHANCE ® Helical Piles and Anchors have been
supplied to the seismic prone areas of the west
coast of the United States and Canada for over
30 years for projects. In tension applications,

DESIGN METHODOLOGY
they have been in service for over 50 years. They
have been subjected to many earthquakes and
aftershocks with good experience. Our helical
pre-engineered products have been used far more
extensively than any other manufacturer’s helical
Figure 4-21. Earth Pressure on a Grade Beam product in these areas. To date, there have been
no ill effects observed using battered helical piles
and anchors in seismic areas. Due to the increased
foundation stiffness design engineers must take in
account the increased foundation stiffness of battered pile foundations when designing where dynamic
horizontal loads are present.
It is common practice to assume that all lateral loads are transferred to the lateral component of the
piles axial capacity, but this assumption is not a complete model of how battered piles behave. A
portion of the lateral load is transferred to the lateral component of the pile’s axial capacity but a load
is also transferred passively to the surrounding soil. Allowable bending moment of the pile must be
taken into account when designing a group. The bending moment induced typically will be less than
that of a vertical pile under similar shear loads, but can excessive if a large enough shear load is applied
to the pile group.

Additional Comments
The lateral capacity of round shaft (Type RS) helical piles and anchors is greater than the square shaft
(Type SS) helical anchors and piles because of the larger section size. Typical pipe diameters of 2-7/8”
(73mm), 3-1/2” (89 mm) and 4-1/2” (114 mm) OD are used for CHANCE helical piles. As shown in design
example 8-13 in Section 8, enlarged shaft sections are used for certain applications. From a practical
standpoint, the largest diameter helical pile available from Hubbell Power Systems, Inc. is 10-3/4”
diameter, but larger shaft diameters are available on a project specific basis.
As previously noted, there are several other methods used to analyze the lateral capacity of the shaft
of piles. Murthy (2003) also presented a direct method for evaluating the lateral behavior of battered
(inclined) piles.

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DESIGN METHODOLOGY

Figure 4-22.Group Box Pile Deflection

Figure 4-22 shows 30 times the deflection of an RS3500 pile group within allowable bending moment.
The actual deflection of the pile group is approximatly 5/16.” The tension and compression battered piles
both resist the shear axially and passively while the vertical pile is only resisting lateral load passively.
The lateral load causes the tension pile to be pushed downward into the soil and compression pile is
pushed upward. This behavior is shown in Figure 4-23.

Figure 4-23 Behavior of Battered Piles

The tension pile sees large passive resistance than the compression pile due to the force pushing the pile
downward (Ft). The compression piles transfers a greater portion of the lateral load axially.
The pile head amount of fixity is a critical component when designing battered piles. For lateral
deflection a fixed head creates the stiffest load response, but will induce the highest bending moments
within the piles. Fixed head conditions are typical of concrete or moment resistant caps and grillages. A
pinned head condition will induce lower bending moments, but will allow much higher deflections. This
typically results in a less efficient pile cap that can withstand less shear load. Pinned head conditions are
typical of non-moment resistant caps and grillages.

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4.9 BUCKLING/BRACING/SLENDERNESS CONSIDERATIONS
Introduction
Buckling of slender foundation elements is a common concern among designers and structural
engineers. The literature shows that several researchers have addressed buckling of piles and micropiles
over the years (Bjerrum 1957, Davisson 1963, Mascardi 1970, and Gouvenot 1975). Their results generally
support the conclusion that buckling is likely to occur only in soils with very poor strength properties
such as peat, very loose sands, and soft clay.
However, it cannot be inferred that buckling of a helical pile will never occur. Buckling of helical piles in
soil is a complex problem best analyzed using numerical methods on a computer. It involves parameters
such as the shaft section and elastic properties, coupling strength and stiffness, soil strength and
stiffness, and the eccentricity of the applied load. This section presents a description of the procedures
available to evaluate buckling of helical piles, and recommendations that aid the systematic performance
of buckling analysis. Buckling of helical piles under compression loads, especially square shaft helical
piles, may be important in three situations:
1. When a pile is relatively long (>20 feet [6 m]) and is installed through very soft clay into a very hard

DESIGN METHODOLOGY
underlying layer and is end-bearing.
2. When a pile is installed in loose, saturated clean sand that undergoes liquefaction during an
earthquake event.
3. When a pile is subject to excessive eccentric load without adequate bracing.
Bracing
Bracing of pile foundation elements is a common concern among designers and structural engineers,
especially for helical piles and resistance piers with slender shafts. Section 1810.2.2 of the 2009 &
2012 International Building Code requires deep foundations to be braced to provide lateral stability in
all directions. Bracing can be provided many different ways – including pile groups of three or more,
alternate lines of piles spaced apart, and using slabs, footings, grade beams and other foundation
elements to provide lateral stability. When CHANCE® Helical Piles and ATLAS RESISTANCE® Piers are
used for foundation repair, the piers must be braced as per situation 3 above. The following figures show
two methods that are often used to ensure adequate bracing is used.

Buckling Background
Buckling of columns most often refers to the allowable compression load for a given unsupported length.
The mathematician Leonhard Euler solved the question of critical compression load in the 18th century
with a basic equation included in most strength of materials textbooks.

Pcrit π2EI/(KLu)2 Equation 4-55

E = Modulus of elasticity
where I = Moment of inertia
K = End condition parameter that depends on fixity
Lu = Unsupported length
Most helical piles have slender shafts which can lead to very high slenderness ratios (Kl/r), depending
on the length of the foundation shaft. This condition would be a concern if the helical piles were in air or

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 water and subjected to a compressive load. For this case, the critical buckling load could be estimated
using the well-known Euler equation above.
However, helical piles are not supported by air or water, but by soil. This is the reason helical piles can be
loaded in compression well beyond the critical buckling loads predicted by Equation 4-55. As a practical
guideline, soil with N60 SPT blow counts per ASTM D-1586 greater than 4 along the entire embedded
length of the helical pile shaft has been found to provide adequate support to resist buckling - provided
there are no horizontal (shear) loads or bending moments applied to the top of the foundation. Only
the very weak soils are of practical concern. For soils with N60 values of 4 blows/ft or less, buckling
calculations can be done by hand using the Davisson Method (1963) or by computer solution using the
finite-difference technique as implemented in the LPILEPLUS computer program (ENSOFT, Austin, TX).
In addition, the engineers at Hubbell Power Systems, Inc. have developed a macro-based computer
solution using the finite-element technique with the ANSYS® analysis software. If required, application
engineers can provide project specific buckling calculations - given sufficient data relating to the
applied loads and the soil profile. If you need engineering assistance, please contact your CHANCE®
Distributor in your area. Contact information for CHANCE® Distributors can be found at www.abchance.
com. These professionals will help you to collect the data required to perform a buckling analysis. The
distributor will either send this data to Hubbell Power Systems, Inc. for a buckling analysis or provide
DESIGN METHODOLOGY

this service themselves.

Buckling/Lateral Stability per International Building Code (IBC) Requirements

IBC 2009 Section 1810.2.1 - Lateral Support states that any soil other than fluid soil shall be deemed to
afford sufficient lateral support to prevent buckling of deep foundation elements in accordance with ac-
cepted engineering practice and the applicable provisions of this code. Per IBC 2006 Section 1808.2.9.2
& IBC 2009 Section 1810.2.1, pier/piles driven into firm ground can be considered fixed and laterally
supported at 5 feet below the ground surface and in soft material at 10 feet below the ground surface.
The IBC does not specifically define fluid, soft, and firm soil. To remedy this, ICC-ES Acceptance Criteria
AC358 defined these soil terms as follows:
Firm soils are defined as any soil with a Standard Penetration Test blow count of five or greater.
Soft soils are defined as any soil with a Standard Penetration Test blow count greater than zero and less
than five.
Fluid soils are defined as any soil with a Standard Penetration Test blow count of zero [weight of
hammer (WOH) or weight of rods (WOR).
Therefore, one method to check the effects of buckling and lateral stability of helical piles and
resistance piers is to assume the depth to fixity is either 5 feet in firm soil, or 10 feet in soft soil. The
corresponding axial compression capacity of the pile shaft is determined based on either 5 feet or 10
feet of unsupported length. This is the method used to determine the nominal, LRFD design, and ASD
allowable compression strengths of the helical pile product families provided in Section 6 of this manual.
Buckling Analysis by Davisson (1963) Method
A number of solutions have been developed for various combinations of pile head and tip boundary

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 DESIGN METHODOLOGY
Figure 5-24 Poulos and Davis (1980)

conditions and for the cases of constant modulus of sub grade reaction (Kh) with depth. One of these
solutions is the Davisson (1963) Method as described below. Solutions for various boundary conditions
are presented by Davisson in Figure 4-24. The axial load is assumed to be constant in the pile – that is no
load transfer due to skin friction occurs and the pile initially is perfectly straight. The solutions shown in
Figure 4-24 are in dimensionless form, as a plot of Ucr versus Imax.

where Ucr = PcrR2/EpIp or Pcr = UcrEpIp/R2 Equation 4-56

where R= 4√E I /k d Equation 4-57

pp h

Imax = L/R Equation 4-58

where
Pcr = Critical buckling load
Ep = Modulus of elasticity of foundation shaft
Ip = Moment of inertia of foundation shaft
Kh = Modulus of sub grade reaction
d = Foundation shaft diameter
L = Foundation shaft length over which kh is taken as constant
Ucr = Dimensionless ratio
By assuming a constant modulus of sub grade reaction (kh) for a given soil profile to determine R, and
using Figure 4-24 to determine Ucr, Equation 4-56 can be solved for the critical buckling load. Typical
values for kh are shown in Table 4-16.

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 TABLE 4-16. MODULUS OF SUB GRADE REACTION - TYPICAL VALUES
Soil Description odulus of Subgrade Reaction (Kh) (pci)
Very soft clay 15 - 20
Soft clay 30 - 75
Loose sand 20
Figure 4-24 shows that the boundary conditions at the pile head and tip exert a controlling influence
on Ucr, with the lowest buckling loads occurring for piles with free (unrestrained) ends. Design Example
8-16 in Section 8 illustrates the use of the Davisson (1968) method to determine the critical buckling
load.
Another way to determine the buckling load of a helical pile in soil is to model it based on the classical
Winkler (mathematician, circa 1867) concept of a beam-column on an elastic foundation. The finite
difference technique can then be used to solve the governing differential equation for successively
greater loads until, at or near the buckling load, failure to converge to a solution occurs. The derivation
for the differential equation for the beam-column on an elastic foundation was given by Hetenyi (1946).
The assumption is made that a shaft on an elastic foundation is subjected not only to lateral loading,
DESIGN METHODOLOGY

but also to compressive force acting at the center of the gravity of the end cross-sections of the shaft,
leading to the differential equation:
EI(d4y/dx4) + Q(d2y/dx2) + Esy = 0
y = Lateral deflection of the shaft at a point x along the length of the shaft
x = Distance along the axis, i.e., along the shaft
where E = Flexural rigidity of the foundation shaft
Q = Axial compressive load on the helical pile
Esy = Soil reaction per unit length
Es = Secant modulus of the soil response curve

The first term of the equation corresponds to the equation for beams subject to transverse loading. The
second term represents the effect of the axial compressive load. The third term represents the effect of
the reaction from the soil. For soil properties varying with depth, it is convenient to solve this equation
using numerical procedures such as the finite element or finite difference methods. Reese, et al. (1997)
outlines the process to solve Equation 4-59 using a finite difference approach. Several computer pro-
grams are commercially available that are applicable to piles subject to axial and lateral loads as well as
bending moments. Such programs allow the introduction of soil and foundation shaft properties that
vary with depth, and can be used advantageously for design of helical piles and micropiles subject to
centered or eccentric loads.
To define the critical load for a particular structure using the finite difference technique, it is necessary
to analyze the structure under successively increasing loads. This is necessary because the solution al-
gorithm becomes unstable at loads above the critical. This instability may be seen as a convergence to
a physically illogical configuration or failure to converge to any solution. Since physically illogical con-
figurations are not always easily recognized, it is best to build up a context of correct solutions at low
loads with which any new solution can be compared.

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Buckling Analysis by Finite Elements
Hubbell Power Systems, Inc. has developed a design tool, integrated with ANSYS® finite element soft-
ware, to determine the load response and buckling of helical piles. The method uses a limited non-linear
model of the soil to simulate soil resistance response without increasing the solution time inherent in a
full nonlinear model. The model is still more sophisticated than a simple elastic foundation model, and al-
lows for different soil layers and types.
The helical pile components are modeled as 3D beam ele-
ments assumed to have elastic response. Couplings are
modeled from actual test data, which includes an initial zero
stiffness, elastic/rotation stiffness and a final failed condition
– which includes some residual stiffness. Macros are used to
create soil property data sets, helical pile component librar-
ies, and load options with end conditions at the pile head.
After the helical pile has been configured and the soil and
load conditions specified, the macros increment the load,
solve for the current load and update the lateral resistance

DESIGN METHODOLOGY
based on the lateral deflection. After each solution, the AN-
SYS® post-processor extracts the lateral deflection and recal-
TYPE RS EXTENSION culates the lateral stiffness of the soil for each element. The
macro then restarts the analysis for the next load increment.
This incremental process continues until buckling occurs.
Various outputs such as deflection and bending moment
plots can be generated from the results.
Practical Considerations – Buckling
TYPE SS TO RS TRANSITION
As stated previously, where soft and/or loose soils (SPT N60
blow count ≤ 4) overlie the bearing stratum, the possibility of
shaft buckling must be considered. Buckling also becomes
a potential limiting factor where lateral loads (bending and
shear) are present in combination with compressive loads.
Factors that determine the buckling load include the helical
pile shaft diameter, length, flexural stiffness and strength,
the soil stiffness and strength, any lateral shear and/or mo-
ment applied at the pile head, and pile head fixity conditions
(fixed, pinned, free, etc.). In addition, all extendable helical
TYPE SS EXTENSION piles have couplings or joints used to connect succeed-
ing sections together in order to install the helix plates into
bearing soil. Bolted couplings or joints have a certain amount
of rotational tolerance. This means the joint initially has no
stiffness until it has rotated enough to act as a rigid element.
This is analogous to saying the coupling or joint acts as a pin
connection until it has rotated a specific amount, after which
it acts as a rigid element with some flexural stiffness.
Figure 5-25 Type SS to RS Combination Pile
Concern about slender shafts and joint stiffness, along with
the fact that helical piles are routinely installed in soils with
poor strength; are some of the reasons why helical piles are
often installed with grouted shafts (helical pulldown piles) and are available with larger diameter pipe
shafts (Type RS). Pipe shaft helical piles have better buckling resistance than plain square shaft (Type
SS) because they have greater section modulus (flexural resistance), plus they have larger lateral dimen-
sions, which means they have greater resistance to lateral deflection in soil. See the specifications section
of the helical pile product family pages in Section 6 for the section properties and dimensions of both
Type SS and RS helical piles/anchors.

Page 4-53 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Type SS helical piles/anchors provide the most efficient capacity-to-torque relationship (see Section 5,
Installation Methodology). Type RS helical piles/anchors provide lateral capacity and better buckling
resistance. A good compromise to address buckling in soft/loose soils is to use helical combination piles,
or “combo piles” for short. A combo pile consists of Type SS square shaft material for the lead section
and Type RS pipe shaft material for the extension sections (see Figure 4-25). The combo pile provides
the advantages of both Type SS and RS material, which enables the helical pile/anchor to penetrate
dense/hard soils, while at the same time provide a larger shaft section in the soft/loose soils above the
bearing strata. See Section 6 for more information on combo piles.
The Helical Pulldown® Micropile is a method for constructing a grout column around the shaft of either a
Type SS (square shaft) or RS (round shaft) helical pile installed in soft/loose soil. The installation process
displaces soil around the central steel shaft and replaces it with a gravity fed, neat cement grout mixture.
Upon curing, the grout forms a column that increases the section modulus of the pile shaft to the point
that buckling is not the limiting condition. In addition to buckling resistance, the grout column increases
axial load capacity due to skin friction or adhesion along the shaft; plus the load/deflection response of
the helical pile is stiffer. See Section 7 for more information on CHANCE HELICAL PULLDOWN® Micro-
piles.
CHANCE Helical Pulldown® Micropiles cannot be installed in every soil condition. To date, grouted shaft
DESIGN METHODOLOGY

helical piles have been successfully installed in overburden soil with SPT blow counts greater than 10
blows/ft. In those cases, the grouted shaft is being used to develop greater load capacity and a stiffer
response, not necessarily to prevent buckling. Contractors have successfully installed pulldown micro-
piles in glacial tills (SPT N60 > 50) using special soil displacement methods. Increasingly dense soil makes
installation more difficult for the displacement element, which has to force soil laterally outward away
from the central steel shaft.

HELICAL PILE DEFLECTION AT WORKING LOAD

Most of the discussion thus far has focused on evaluating the ultimate load capacity of helical piles/
anchors in axial compression or tension. This is considered as the Load Limit State and gives the upper
bound on the load capacity. The displacements of the pile/anchor at this load state will be very large (>
2 inches [51 mm]) and technically the pile/anchor cannot sustain additional load but the deflection just
keeps increasing. However, it is also
of great interest to most engineers
to consider the behavior of a helical
pile/anchor at a lower working load
or Serviceability State which will be
well below the Load Limit State.
We can consider a typical Load-
Displacement curve as shown above.
This plot is the test results of a 1.5 in.
x 1.5 in. square-shaft helical anchor
with a single 12 in. helix installed to
a depth of 10 ft. in a medium dense
silty sand. The test was performed
in tension. According to the IBC, the
Ultimate Capacity may be taken as
the load producing a net displace-
ment of 10% of the helix diameter or
in this case the load at 1.20 in. which
is 19,500 lbs. It is obvious that in this
case, as in most cases, the anchor

Figure 4-26

Page 4-54 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
can actually take more load, up to as much as 20% of the helix diameter.
Using a ASD Factor of Safety of 2.0, the working load for this anchors would be equal to 19,500 lbs/2.0
= 9,750 lbs. Because the load-displacement curve of most helical piles/anchors is generally nonlinear it
would be expected that the displacement at the working load would be less than ½ of the displacement
at 1.20 in. In this case, the displacement at the working load of 9,750 lbs is on the order of 0.36 in. Using
a lower Factor of Safety gives a higher displacement. For example if a Factor of Safety of 1.5 is used, the
working load becomes 19,500 lbs/1.5 = 13,000 lbs and the displacement corresponding to this load is on
the order of 0.55 in.
Based on a review of a number of tests performed on single-helix pile/anchors in Colorado, Cherry and
Perko (2012) recently suggested that for many anchors/piles, the displacement at the working loads (F.S.
= 2) averaged about 0.25 in. Additional work is needed to determine how this may vary for multi-helix
piles/anchors and if other soils show different behavior.

References:
1. Specification ASTM D 1586, Standard Test Method for Penetration Test and Split-Barrel Sampling of

DESIGN METHODOLOGY
Soils, American Society for Testing and Materials.
2. Abdelghany, Y, and El Naggar (2010), Full-scale Experimental and Numberical Analysis of
Instrumented Helical Screw Piles Under Axial and Lateral Montonic and Cyclic Loadings – A Promising
Solution for Seismic Retrofitting. Proceedings of the 6th International Engineering and Construction
Conference, Cairo, Egypt.
3. Bjerrum, L., Norwegian Experiences with Steel Piles to Rock, Geotechnique, Vol 7, 1957.
4. Bowles, J.E., Foundation Analysis and Design, First Edition, McGraw-Hill, 1968.
5. Bowles, J.E., Foundation Analysis and Design, Fourth Edition, McGraw-Hill, 1988.
6. Brinch Hansen, J., The Ultimate Resistance of Rigid Piles Against Transversal Forces, Geoteknish
Institute Bulletin No. 12, Copenhagen, 1961.
7. Broms, Bengt. B., Lateral Resistance of Piles in Cohesive Soils, Proceedings of the American Society
of Civil Engineers, Journal of the Soil Mechanics and Foundations Division, Vol. 90, SM2, 1964.
8. Broms, Bengt B., Lateral Resistance of Piles in Cohesionless Soils, Proceedings of the American
Society of Civil Engineers, Journal of the Soil Mechanics and Foundations Division, vol. 90 SM3, 1964.
9. Cadden, Allen and Jesus Gomez, Buckling of Micropiles, ADSC-IAF Micropile Committee, Dallas, TX,
2002.
10. Clemence, Samuel P. and others, Uplift Behavior of Anchor Foundations in Soil, American Society of
Civil Engineers, 1985.
11. Das, Braja M., Theoretical Foundation Engineering, Elsevier Science Publishing Company Inc., New
York, NY, 1987.
12. Davis, E.H., The Application of the Theory of Plasticity to Foundation Problems-Limit Analysis, Post
Graduate Course, University of Sydney, Australia, 1961.
13. Davisson, M.T., Estimating Buckling Loads for Piles, Proceedings of the Second Pan-American
Conference on Soil Mechanics and Foundation Engineering, Brazil, Vol 1, 1963.
14. Davisson, M.T., Laterally Loaded Capacity of Piles, Highway Research Record, No. 333: 104-112, 1970.
15. Design Manual DM7, NAVFAC, Foundations and Earth Structures, Government Printing Office, 1986.
16. Design Manual DM7, NAVFAC, Soil Mechanics, Government Printing Office, 1986.
17. Gouvenot, D., Essais en France et a l’Etranger sur le Frottement Lateral en Fondation: Amelioration
par Injection, Travaux, 464, Nov, Paris, France, 1973.

Page 4-55 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 18. HeliCALC Micropile Design Assessment Program, Theoretical and User’s Manual, Hubbell Power
Systems/A.B. Chance Co., 2001.
19. Hetenya, M., Beams on Elastic Foundations, The University of Michigan Press, Ann Arbor, MI, 1946.
20. Hoyt, Robert M., Gary L. Seider, Lymon C. Reese and Shin-Tower Wang, Buckling of Helical Anchors
Used for Underpinning, Proceedings, ASCE National Convention, San Diego, CA, 1995.
21. Meyerhof, George Geoffrey, Bearing Capacity and Settlement of Pile Foundations, Journal of the
Geotechnical Engineering Division, Proceedings of the American Society of Civil Engineers, Volume
102, No GT3, 1976.
22. Poulos, H.G., Analysis of Piles in Soils Undergoing Lateral Movements, JSMFD, ASCE, Vol. 99, SM5,
1973.
23. Reese, L.C., The Analysis of Piles Under Lateral Loading, Proceedings, Symposium on the Interaction
of Structure and Foundation, Midland Soil Mechanics and Foundation Engineering Society, University
of Birmingham, England, 1971.
24. Reese, L.C. and S.J. Wright, Drilled Shaft Design and Construction Guidelines Manual, US Department
of Transportation, Federal Highway Administration, 1977.
DESIGN METHODOLOGY

25. Reese, L.C., W.M. Wang, J.A. Arrellaga, and J. Hendrix, Computer Program LPILEPLUS Technical
Manual, Version 3.0, Ensoft, Inc., Austin, TX, 1997.
26. Sharnouby and El Naggar (2011), Montonic and Cyclic Lateral Full-scale Testing of Reinforced Helical
Pulldown Micropiles, Proceedings of the DFI Annual Conference 2011, Boston, MA.
27. Terzaghi, K. and R.B. Peck, Soil Mechanics in Engineering Practice, John Wiley and Sons, Inc., 1967.
28. Richards, Tom, “Battered Pile Misconceptions”, Deep Foundations Magazine, January 2016;
ppgs. 63-66.

Page 4-56 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 INSTALLATION METHODOLOGY

Page 5-1 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 INSTALLATION METHODOLOGY
SECTION 5

CONTENTS

CHANCE® HELICAL PILES/ANCHOR..................................................... 5-4

INSTALLATION TORQUE/LOAD CAPACITY RELATIONSHIP....... 5-4
TORQUE INDICATOR AND MOTOR CALIBRATION......................... 5-13
INSTALLATION TERMINATION CRITERIA............................................ 5-13

SYMBOLS USED IN THIS SECTION

INSTALLATION METHODOLOGY

Qult .................................................................... Ultimate Uplift Capacity 5-5

Kt ........................................................................ Empirical Torque Factor 5-5
T ................................................................... Average Installation Torque 5-5
SS ..............................................................................................Square Shaft 5-5
RS............................................................................................... Round Shaft 5-5
Hd/Sd......................................................Helix to Shaft Diameter Ratio 5-7
Qact .................................................................................. Actual Capacity 5-9
Qcalc.......................................................................... Calculated Capacity 5-9
Qact/Qcalc ........................................................................Capacity Ratio 5-9
CID.................................................................... Cubic Inch Displacement 5-12

Page 5-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 INSTALLATION METHODOLOGY
DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to
point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted
prior to any installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption,
revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in
its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of
CHANCE® Civil Construction foundation support products.

Page 5-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 CHANCE® HELICAL PILE/ANCHORS
By definition, a helical pile/anchor is a low soil displacement foundation element specifically designed
to minimize disturbance during installation. In their simplest forms, helical pile/anchors consist of at
least one helix plate and a central steel shaft (see Figure 5-4). The helix geometry is very important in
that it provides the downward force or thrust that pulls a helical pile/anchor into the ground. The helix
must be a true ramped spiral with a uniform pitch to maximize efficiency during installation. If the helix
is not formed properly, it will disturb the soil more than if a true helix advances at a rate of one pitch
per revolution. The central steel shaft transmits the rotational energy or torque from the machine to the
helix plate(s). Most helical piles in North America use a low displacement (less than 4.5 inches (114 mm)
diameter shaft in order to reduce friction and soil displacement during installation. A helical pile/anchor
functions very similar to a wood screw except that it has a discontinuous thread-form and is made to a
much larger scale.

INSTALLATION TORQUE/LOAD CAPACITY RELATIONSHIP

Before installation, a helical pile/anchor is simply a screw with a discontinuous thread and a uniform
INSTALLATION METHODOLOGY

pitch. When installed into soil, a helical pile/anchors functions as an axially loaded end-bearing deep
foundation. The helix plates serve a two-fold purpose. The first purpose is to provide the means to
install the helical pile/anchor. The second purpose is to provide the bearing element means for load
transfer to soil. As such, helical pile/anchor design is keyed to these two purposes, both of which can
be used to predict the ultimate capacity.
Section 4 detailed how helix plates act as bearing elements. The load capacity is determined by
multiplying the unit bearing capacity of the soil at each helix
location by the projected area of each helix. This capacity is
generally defined as the ultimate theoretical load capacity
because it is based on soil parameters either directly measured or
empirically derived from soil exploration sounding data.
The purpose of this section is to provide a basic understanding of
how installation torque (or installation energy) provides a simple,
reliable means to predict the load capacity of a helical pile/anchor.
More importantly, this prediction method is independent of the
bearing capacity method detailed in Section 4, so it can be used
as a “field production control” method to verify load capacity
during installation.
The installation torque-to-load capacity relationship is an empirical
method originally developed by the A. B. Chance Company in the
late 1950’s and early 1960’s. Hubbell Power Systems, Inc. has long
promoted the concept that the torsion energy required to install a
helical anchor/pile can be related to the ultimate load capacity of
a pile/anchor. Precise definition of the relationship for all possible
variables remains to be achieved. However, simple empirical
relationships, originally derived for tension loads but also valid
for compression loads, have been used for a number of years.
The principle is that as a helical anchor/pile is installed (screwed)
into increasingly denser/harder soil, the resistance to installation
(called installation energy or torque) will increase. Likewise, the
higher the installation torque, the higher the axial capacity of
the installed pile/anchor. Hoyt and Clemence (1989) presented a
landmark paper on this topic at the 12th International Conference
on Soil Mechanics and Foundation Engineering. They proposed
the following formula that relates the ultimate capacity of a helical Helical Pile/Anchor
pile/anchor to its installation torque: Figure 6-4

Page 5-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Qult = Kt x T Equation 5-1

where Qult = Ultimate uplift capacity [lb (kN)]

Kt = Empirical torque factor [ft-1 (m-1)]
T = Average installation torque [lb-ft (kN-m)]

Hoyt and Clemence recommended Kt = 10 ft-1 (33 m-1) for square shaft (SS) and round shaft (RS) helical
anchors less than 3.5” (89 mm) in diameter, 7 ft-1 (23 m-1) for 3.5” diameter round shafts, and 3 ft-1 (9.8
m-1) for 8-5/8” (219 mm) diameter round shafts. The value of Kt is not a constant - it may range from 3 to
20 ft-1 (10 to 66 m-1), depending on soil conditions, shaft size and shape, helix thickness, and application
(tension or compression). For CHANCE® Type SS Square Shaft Helical Piles/Anchors, Kt typically ranges
from 10 to 13 ft-1 (33 to 43 m-1), with 10 ft-1 (33 m-1) being the recommended default value. For CHANCE®
Type RS Pipe Shaft Helical Piles/Anchors, Kt typically ranges from 3 to 10 ft-1 (10 to 33 m-1), with 9 ft-1 (30
m-1) being the recommended default for Type RS2875; 7 ft-1 (23 m-1) being the recommended default for
Type RS3500.300; and 6 ft-1 (20 m-1) being the recommended default for Type RS4500.337.

INSTALLATION METHODOLOGY
The Canadian Foundation Engineering Manual (2006) recommends values of Kt = 7 ft-1 for pipe shaft
helical piles with 90 mm OD, and Kt = 3 ft-1 for pipe shaft helical piles approaching 200 mm OD.
The correlation between installation torque (T), and the ultimate load capacity (Qult) of a helical pile/
anchor, is a simple concept but a complicated reality. This is partly because there are a large number of
factors that can influence the determination of the empirical torque factor Kt. A number of these factors
(not including soil), are summarized in Table 5-1.
It is important to understand that torque correlation is valid when the helical pile/anchor is advancing at
a rate of penetration nearly equal to one helix pitch per revolution. Large displacement shafts [>8-5/8”
(219mm)] are less likely to advance at this rate, which means torque correlation cannot be used as a
means to determine capacity.

FACTORS INFLUENCING KT, TABLE 5-1

Factors Affecting Installation Torque (T) Factors Affecting Ultimate Capacity (Qult)

Method of Measuring Installation Torque (T) Number and Size of Helix Plates
Installed Depth Used to Determine “Average” Torque Direction of Loading (Tension or Compression)
Applied Down-Force or “Crowd” Geometry of Couplings
Rate of Rotation Spacing of Helix Plates

Alignment of Pile/Anchor Shape and Size of Shaft

Rate of Advance Time between Installation and Loading

Geometry of Couplings

Shape and Size of Shaft

Shape and Size of Shaft

Number & Size of Helix Plates
Pitch of Helix Plates

Page 5-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 In order for Equation 5-1 to be useful, installation torque must be measured. There are a variety of
methods used to measure torque. Hubbell Power Systems, Inc. offers two in-line torque indicators; in-
line indicators are the best method to determine torque for capacity prediction. Other useful methods
to measure torque are presented later in this section. For torque correlation to be valid, the rate of
penetration should be between 2.5” to 3” per revolution. The rotation speed should be consistent and
in the range of 5 to 15 RPM. And, the minimum effective torsional resistance criterion (the average
installation torque) should be taken over the last 3 feet of penetration; unless a single helix pile is used
for compression load, where it is appropriate to use the final (last) installation torque.
ICC-ES Acceptance Criteria AC358 for helical pile systems and devices Section 3 provides torque
correlation (Kt) values for conforming helical pile systems based on shaft size and shape. They are the
same as recommended by Hubbell Power Systems, Inc. and by Hoyt and Clemence. Hubbell Power
Systems, Inc. helical piles are conforming per AC358. The AC358 Kt values are the same for both
tension and compression axial loads.
The International Building Code (IBC) 2009 & 2012 Section 1810.3.3.1.9 states there are three ways to
determine the load capacity of helical piles – including well documented correlations with installation
torque.
INSTALLATION METHODOLOGY

Soil Factors Influencing Kt

Locating helix bearing plates in very soft, loose, or sensitive
soils will typically result in Kt values less than the recommended
default. This is because some soils, such as salt leached
marine clays and lacustrine clays, are very sensitive and lose
considerable shear strength when disturbed. It is better to extend
the helical pile/anchor beyond sensitive soils into competent
bearing strata. If it’s not practical to extend the helical pile/
anchor beyond sensitive soils, testing is required to determine
the appropriate Kt.
Full-scale load testing has shown that helical anchors/piles
typically have at least the same capacity in compression as in
tension. In practice, compression capacity is generally higher
than tension capacity because the pile/anchor bears on soil
Top View of Helix below rather than above the helix plates, plus at least one helix
Figure 5-2 plate is bearing on undisturbed soil. Soil above the bearing
plates is disturbed by the slicing action of the helix, but not
overly disturbed by being “augured” and removed. Typically, the
same values of Kt are used for both tension and compression
applications. This generally results in conservative results for
compression applications. A poorly formed helix shape will
disturb soil enough to adversely affect the torque-to-capacity
relationship, i.e., Kt is reduced. To prevent this, Hubbell Power
Systems, Inc. uses matching metal dies to form helix plates which
are as near to a true helical shape as is practically possible. To
understand all the factors that Kt is a function of, one must first
understand how helical piles/anchors interact with the soil during
installation.

Friction Forces Action on Central Shafts

Figure 5-3

Page 5-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Torque Resistance Factors
There are two main factors that contribute to the torque resistance generated during a pile/anchor
installation, friction and penetration resistance. Of the two factors, friction is the larger component of
torque resistance.
Friction Has Two Basic Parts:
(1) Friction on the helix plate and friction along the central steel shaft. Friction resistance increases with
helix size because the surface area of the helix in contact with the soil increases with the square of the
diameter (see Figure 5-2). Likewise, friction resistance increases with pitch size, i.e., the larger the pitch,
the greater the resistance. This is analogous to the difference between a coarse thread and a fine thread
bolt. Basic physics tells us that “work” is defined as
force time’s distance. A larger pitch causes the helix to travel a greater distance per revolution, thus more
work is required.
(2) Friction along the central steel shaft is similar to friction on the helix plate. Friction resistance
increases with shaft size because the surface area of the shaft in contact with the soil increases as
the diameter increases. An important performance factor for helical pile/anchors is the helix to shaft

INSTALLATION METHODOLOGY
diameter ratio (Hd/Sd). The higher the Hd/Sd ratio, the more efficient a given helical pile/anchor will
be during installation. Friction resistance also varies with shaft shape (see Figure 5-3). A round shaft
may be the most efficient section to transmit torque energy, but it has the disadvantage of full surface
contact with the soil during installation. When the central steel shaft is large (> 3” [76 mm] in diameter)
the shaft friction resistance contributes significantly to the total friction resistance. However, a square
shaft (< 3” [76 mm] in diameter) has only the corners in full surface contact with the soil during
installation, thus less shaft friction resistance. Friction energy (energy loss) required to install a helical
pile/anchor is related to the helix and shaft size. The total energy loss due to friction is equal to the
sum of the friction loss of all the individual helix plates plus the length of shaft subjected to friction via
contact with the soil.
Penetration Resistance Has Two Basic Parts:
(1) Shearing resistance along the leading edge of the helix plate to allow passage of the helix plate and
penetration resistance of the shaft/pilot point. Shearing resistance increases with helix size because
leading edge length increases as the diameter increases. Shearing resistance also increases with helix
thickness because more soil has to be displaced with a thick helix than with a thin helix (see Figure 5-4).
The average distance the soil is displaced is equal to approximately 1/2 the helix thickness, so as the
thickness increases the more work (i.e., energy) is required to pass the helix through the soil.
(2) Penetration resistance increases with shaft size because the projected area of the hub/pilot point
increases with the square of the shaft radius (see Figure 5-5). The average distance the soil is displaced is
approximately equal to the radius of the shaft, so as the shaft size increases, the more work (i.e., energy)
is required to pass the hub/pilot point through the soil.
The penetration energy required to install a helical pile/anchor is proportional to the volume of soil
displaced times the distance traveled. The volume of soil displaced by the anchor/pile is equal to the
sum of the volumes of all the individual helix plates plus the volume of the soil displaced by the hub/pilot
point in moving downward with every revolution.
Energy Relationships
Installation energy must equal the energy required to penetrate the soil (penetration resistance) plus
the energy loss due to friction (friction resistance). The installation energy is provided by the machine
and consists of two components, rotation energy supplied by the torque motor and downward force
(or crowd) provided by the machine. The rotation energy provided by the motor along with the
inclined plane of a true helical form generates the thrust necessary to overcome the penetration and
friction resistance. The rotational energy is what is termed “installation torque.” The downward force
also overcomes penetration resistance, but its contribution is usually required only at the start of the
installation, or when the lead helix is transitioning from a soft soil to a hard soil.

Page 5-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
INSTALLATION METHODOLOGY

Section View of Leading

Edge with Flow Lines Shaft/Pilot Point with Flow Lines
Figure 5-4 Figure 5-5

From an installation energy standpoint, the perfect helical pile/anchor would consist of an infinitely
thin helix plate attached to an infinitely strong, infinitely small diameter central steel shaft. This
configuration would be energy efficient because penetration resistance and friction resistance is low.
Installation torque to capacity relationships would be high. However, infinitely thin helix plates and
infinitely small shafts are not realistically possible, so a balanced design of size, shape, and material is
required to achieve consistent, reliable torque to capacity relationships.
As stated previously, the empirical relationship between installation torque and ultimate capacity is well
known, but not precisely defined. As one method of explanation, a theoretical model based on energy
exerted during installation has been proposed [Perko (2000)]. The energy model is based on equating
the energy exerted during installation with the penetration and friction resistance. Perko showed how
the capacity of an installed helical pile/anchor can be expressed in terms of installation torque, applied
downward force, soil displacement, and the geometry of the pile/anchor. The model indicates that Kt
is weakly dependent on crowd, final installation torque, number of helix plates, and helix pitch. The
model also indicates that Kt is moderately affected by helix plate radius and strongly affected by shaft
diameter and helix plate thickness.
The important issue is energy efficiency. Note that a large shaft helical anchor/pile takes more energy
to install into the soil than a small shaft pile/anchor. Likewise, a large diameter, thick helix takes more
energy to install into the soil than a smaller diameter, thinner helix. The importance of energy efficiency
is realized when one considers that the additional energy required to install a large displacement helical
pile/anchor contributes little to the load capacity of the pile/anchor. In others words, the return on the
energy “investment” is not as good. This concept is what is meant when Hubbell Power Systems, Inc.
engineers say large shaft diameter and/or large helix diameter (>16” diameter) pile/anchors are not
efficient “torque-wise.” This doesn’t mean large diameter or large helix plate piles are not capable of
producing high load capacity, it just means the installation energy, i.e. machine, must be larger in order
to install the pile.

Page 5-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
If one considers an energy balance between the energy exerted during loading and the appropriate
penetration energy of each of the helix plates, then it can be realized that any installation energy not
specifically related to helix penetration is wasted. This fact leads to several useful observations. For a
given helix configuration and the same available installation energy (i.e., machine):
1. Small displacement shafts will disturb less soil than large displacement shafts.
2. Small displacement shafts result in less pore pressure buildup than large displacement shafts.
3. Small displacement shafts will penetrate farther into a given bearing strata than large displacement
shafts.
4. Small displacement shafts will penetrate soils with higher SPT “N” values than large displacement
shafts.
5. Small displacement shafts will generate more axial load capacity with less deflection than large
displacement shafts.
6. Kt varies inversely with shaft diameter.

INSTALLATION METHODOLOGY
Reliability of Torque/Capacity Model
Hoyt and Clemence (1989) analyzed 91 tension load tests at 24 different sites with sand, silt and clay
soils all represented. All of the tests used in the study were short term; most were strain controlled and
included a final loading step of imposing continuous deflection at a rate of approximately 4 inches (102
mm) per minute. This final load was taken as the ultimate capacity. The capacity ratio Qact/Qcalc was
obtained for each test by dividing the actual capacity (Qact) by the calculated capacity (Qcalc). Qcalc was
calculated by using three different load capacity models: (1) Cylindrical shear, (2) Individual bearing, and
(3) Torque correlation. These data were then compared and plotted on separate histograms (see Figures
5-6 and 5-7, cylindrical shear histogram not shown).
All three capacity models exhibited the capability of over-predicting pile/anchor capacity. This would
suggest the use of appropriate Factors of Safety. However, the authors did not discriminate between
“good” and “poor” bearing soils when analyzing the results. In other words, some of the test data
analyzed were in areas where the helix plates were located in soils typically not suitable for end bearing,
(i.e., sensitive) clays and loose sands.

Individual Bearing Method Torque Correlation Model

Figure 5-6 Figure 5-7

Page 5-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 All three capacity models’ mean values were quite close, but the range and standard deviation were
significantly lower for the torque correlation method than for the other two. This improved consistency
is probably due to the removal of several random variables from the capacity model. Therefore, the
installation torque correlation method yields more consistent results than either of the other two
methods. The installation torque method does have one disadvantage, however, in that it cannot
be used until after the helical pile/anchor has been installed. Therefore, it is better suited to on-site
production control and termination criteria than design in the office.
Perko (2012) suggested that if both individual bearing capacity and torque correlation are used to
determine the bearing capacity of a helical pile/anchor, the resulting capacity will be accurate to within
97.7% reliability.
Measuring Installation Torque
The torque correlation method requires the installation torque to be measured and recorded in the
field. There are several methods that can be used to measure torque, and Hubbell Power Systems, Inc.
has a complete line of torque indicators to choose from. Each one is described below along with its
advantages and disadvantages:
INSTALLATION METHODOLOGY

• Shaft Twist
A.B. Chance Company stated in early editions of the Encyclopedia of Anchoring (1977) that for standard
SS5 anchors, “the most secure anchoring will result when the shaft has a 1 to 1-1/2 twist per 5-foot
section.” Shaft twist is not a true torque-indicating device. It has been used as an indication of “good
bearing soil” since type SS anchors were first introduced in the mid-1960’s. Shaft twist should not be
used exclusive of a true torque-indicating device. Some of the reasons for this are listed below.
Advantages:
• Simple, cheap, easy to use.
• Doesn’t require any additional tooling.
• Visible indication of torque.
Disadvantages:
• Qualitative, not quantitative torque relationship.
• Not very accurate.
• Shaft twist can’t be correlated to installation torque on a consistent
basis.
• Type SS5, SS150, SS175, SS200, and SS225 shafts twist, or wrap-up,
at different torque levels.
• Shaft twist for a round shaft is not obvious without other means of
reference.
• Shear Pin Torque Limiter
A shear pin torque limiter is a mechanical device consisting of two shear
halves mounted to a central pin such that the shear halves are free to
rotate (see Figure 5-8). Shear pins inserted into perimeter holes prevent
the shear halves from rotating and are rated to shear at 500 ft-lb of torque
per pin. Required torque can be achieved by loading the shear halves with
the appropriate number of pins, i.e., 4000 ft-lb = 8 pins. The shear pin
torque limiter is mounted in line with the torque motor and pile/anchor
tooling.
Advantages:
Shear Pin Torque Limiter
Figure 5-8 • Simple design, easy to use.
• Tough and durable, will take a lot of abuse and keep working.

Page 5-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 • Accurate within ± 5% if kept in good working
condition.
• Torque limiter - used to prevent exceeding a
specified torque.
• Relatively inexpensive to buy and maintain.
• Easy interchange from one machine to another.
Disadvantages:
• Point-wise torque indicator, i.e., indicates
torque at separate points, not continuously.
• Requires constant unloading and reloading of
shear pins.
• Limited to 10,000 ft-lb.
• Sudden release of torsional (back-lash) energy

INSTALLATION METHODOLOGY
when pins shear.
• Fits tools with 5-1/4” bolt circle only.
• Digital Torque Indicator
A digital torque indicator is a device consisting of strain
Mechanical Dial Torque Indicator
Figure 5-9 gauges mounted to a torsion bar located between
two bolt flanges (see Figure 5-9). This tool measures
installation torque by measuring the shear strain of the
torsion bar. The digital display reads torque directly.
The digital torque indicator is mounted in-line with the
torque motor and
pile/anchor tooling.
Advantages:
• Simple torsion bar & strain gauge design,
easy to use.
• Continuous reading torque indicator.
• Digital display reads torque directly.
Wireless Remote Display
Figure 5-10 • Accurate within ± 2% if kept in good
working condition.
• Fits tools with 5-1/4” and 7-5/8” bolt circles.
• Calibrated with equipment traceable to
US Bureau of Standards before leaving plant.
• Can be used as a calibration tool for other types
of torque indicators.
• Easy interchange from one machine to another.
• Reliable, continuous duty torque indicator.
• Comes with wireless remote display and an
optional remote data logger.
Disadvantages:
• Drive tools must be switched out when
Remote Data Logger installing different types of helical pile/anchor.
Figure 5-11

Page 5-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 • DP-1 Differential Pressure Torque Indicator
A differential pressure torque indicator is a hydraulic device consisting of back-to-back hydraulic
pistons; hoses, couplings, and a gauge (see Figure 5-12). Its’ operation is based on the principle that the
work output of a hydraulic torque motor is directly related to the pressure drop across the motor. The
DP-1 hydraulically or mechanically “subtracts” the low pressure from the high to obtain the “differential”
pressure. Installation torque is calculated using the cubic inch displacement and gear ratio of the torque
motor. The DP-1 piston block and gauge can be mounted anywhere on the machine. Hydraulic hoses
must be connected to the high and low pressure lines at the torque motor.
Advantages:
• Indicates torque by measuring pressure drop across hydraulic torque motor.
• No moving parts.
• Continuous reading torque indicator.
• Very durable - the unit is not in the tool string.
INSTALLATION METHODOLOGY

• Pressure gauge can be located anywhere on the machine.

• Analog type gauge eliminates “transient” torque peaks.
• Pressure gauge can be overlaid to read torque (ft-lb) instead of pressure (psi).
• Accurate within ± 5% if kept in good working condition.
• After mounting, it is always ready for use.
• Can be provided with multiple readout gauges.
Disadvantages:
• Requires significant initial installation setup time and material, i.e., hydraulic fittings, hoses,
oil.
• Requires a hydraulic pressure-to-torque correlation based on the torque motor’s cubic inch
displacement (CID) and gear ratio.
• For two-speed torque motors, pressure-to-torque correlation changes depending on which
speed the motor is in (high or low).
• Requires periodic recalibration against a known standard, such as the digital torque
indicator, or shear pin torque limiter.
• Sensitive to hydraulic leaks in the lines that connect the indicator to the torque motor.
• Relatively expensive.
• Difficult interchange from one machine to another.

Page 5-12 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 TORQUE INDICATOR AND MOTOR
CALIBRATION
All torque indicators require periodic calibration. Hubbell
Power Systems, Inc. recommends that torque indicators be
calibrated at least once per year. The digital torque indicator
can be used in the field to calibrate other indicators, such
as hydraulic pressure gauges and the DP-1. As torque
motors age, the relationship between hydraulic pressure and
installation torque will change. Therefore, it is recommended
that hydraulic torque motors be periodically checked for
pressure/torque relationship throughout their service life.
Hubbell Power Systems, Inc. has torque test equipment
available to recalibrate torque indicators and torque motors.
Differential Pressure
Torque Indicator
Figure 5-12 INSTALLATION TERMINATION CRITERIA

INSTALLATION METHODOLOGY
The engineer of record can use the relationship between
installation torque and ultimate load capacity to establish
minimum torque criteria for the installation of production helical piles/anchor. The recommended default
values for Kt of [10ft-1 (33m-1)] for CHANCE® type SS, [9ft-1 (30m-1)] for type RS2875, [7ft-1 (23m-1)] for
type RS3500 and [6ft-1 (20m-1)] for type RS4500 will typically provide conservative results.
For large projects that merit the additional effort, a pre-production test program can be used to establish
the appropriate torque correlation factor (Kt) for the existing project soils. It is recommended that Kt be
determined by dividing the ultimate load capacity determined by load test by the average installation
(effective) torque taken over the last 3 feet (1 meter) of penetration into the bearing strata. The minimum
effective torsional resistance criterion applies to the “background” resistance; torque spikes resulting
from encounters with obstacles in the ground must be ignored in determining whether the torsional
resistance criterion has been satisfied. The minimum effective torsional resistance criterion (the average
installation torque taken over the last 3 feet of penetration) may not be applicable in certain soil profiles,
such as, a relatively soft stratum overlying a very hard stratum. Engineering judgment must be exercised.
See Appendix B for more detailed explanation of full-scale load tests. Large-scale projects warrant more
than one pre-production test.
Whatever method is used to determine Kt, the production helical piles/anchors should be installed to
a specified minimum torque and overall minimum depth. These termination criteria should be written
into the construction documents. See www.abchance.com for model specifications that contain sections
on recommended termination criteria for helical piles/anchors.
ICC-Evaluation Services ESR-2794 requires the following installation termination criteria:
• When installing single-helix anchors/piles that will be loaded in tension and all multi-helix
anchors/piles, torsional resistance must be recorded at the final tip embedment minus 2 feet
(710 mm) and final embedment minus 1 foot (305 mm), in addition to the resistance at final
embedment.
• For single-helix compression piles, the final torsional resistance reading must be equal to or
exceed the specified minimum.
• For multi-helix anchors and piles, the average of the final three torsional resistance readings
must be equal to or exceed the specified minimum.
• The tip embedment and torsional resistance readings must be verified to meet or exceed the
specified termination criteria before terminating installation.

Page 5-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Minimum Bearing Depth of Top-Most Helix
For deep foundation behavior, Hubbell Power Systems, Inc. recommends the minimum vertical depth of
the top-most helix plate should be at least five times the diameter of the top-most helix. Natural factors
such as frost depth and active zones (expansive soil) can also affect minimum depth. Hubbell Power
Systems, Inc. recommends the minimum vertical depth of the top-most helix plate should be at least
three times the diameter of the top most helix below the maximum frost depth or depth of active zone.
For example, if the frost depth is 4 feet and the top-most helix plate is 12 in (305 mm), then the minimum
depth to the top-most helix is 4 + 3 x (12 in) = 7 ft (2.1 m).
Tolerances
It is possible to install helical piles/anchors within reasonable tolerance ranges. For example, it is
common to locate and install an pile/anchor within 1 inch (25 mm) of the staked location. Plumbness
can usually be held within ± 1° of design alignment. For vertical installations a visual plumbness check
is typically all that’s required. For battered installations, an inclinometer can be used to establish the
required angle. See www.abchance.com for model specifications that contain sections on recommended
termination criteria for helical piles/anchors.
INSTALLATION METHODOLOGY

Torque Strength Rating

Torque strength is important when choosing the correct helical pile/anchor for a given project. It is a
practical limit since the torque strength must be greater than the resistance generated during installation.
In fact, the central steel shaft is more highly stressed during installation than at any other time during
the life of the helical pile/anchor. This is why it is important to control both material strength variation
and process capability in the fabrication process. Hubbell Power Systems, Inc. designs and manufactures
helical piles/anchors to achieve the torque ratings published in the product family sections in Section 6.
The ratings are listed based on product series, such as SS5, SS175, RS3500, etc.
The torque rating is defined as the maximum torque energy that should be applied to the helical pile/
anchor during installation in soil. It is not the ultimate torque strength, defined as the point where the
central shaft experiences torsion fracture. It is best described as an allowable limit, or “safe torque” that
can be applied to the helical pile/anchor. Some other manufacturers publish torque ratings based on
ultimate torque strength.
The designer should select the product series that provides a torque strength rating that meets or
exceeds the anticipated torsion resistance expected during the installation. HeliCAP® Engineering
Software (see Section 4) generates installation torque vs. depth plots that estimate the torque resistance
of the defined soil profile. The plotted torque values are based on a Kt of 10 for Type SS and 9, 7 or 6 for
Type RS. The torque ratings published in the product family sections in Section 6 are superimposed on
the HeliCAP® Torque vs Depth plot, so the user can see at a glance when the estimated torque resistance
equals or exceeds the torque rating of a given product series.
In some instances, it may be necessary to exceed the torque rating in order to achieve the minimum
specified depth, or to install the helical pile/anchor slightly deeper to locate the helix plates farther
into bearing stratum. This “finishing torque limit” should never exceed the published torque rating by
more than 10%. To avoid fracture under impact loading due to obstruction laden soils, choose a helical
product series with at least 30% more torque strength rating than the expected torque resistance. Note
that the possibility of torsion fracture increases significantly as the applied torque increases beyond the
published ratings. The need to install helical pile/anchors deeper is better accomplished by reducing the
size and/or number of helix plates, or by choosing a helical product series with a higher torque rating.

Page 5-14 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
References:
1. A.B. Chance Company, Encyclopedia of Anchoring, Bulletin 01-9401UA, 1977, A.B. Chance Company,
Centralia, MO
2. A.B. Chance, a Division of Hubbell Power Systems, Inc., Product Selection Guide - Resistance Piers
and Helical Piles for Remedial (Underpinning) Applications, Bulletin 01-0601, Hubbell, Inc., Centralia,
MO, 2006.
3. Clemence, S. P., L.K. Crouch and R.W. Stephenson, Prediction of Uplift Capacity for Helical Anchors
in Sand, Conference Proceedings from the Second Geotechnical Engineering Conference - Cairo
University, Cairo, Egypt, 1994.
4. Crouch, L.K. and R.W. Stephenson (1991), Installation Torque Requirements and Uplift Capacity of
Helical Soil Anchors Using Measured Geotechnical Properties of Soil, Doctoral Dissertation, University
of Missouri-Rolla, Rolla, MO, 1994.
5. Hargrave, R.L., and R.E. Thorsten, Helical Piers in Expansive Soils of Dallas,Texas, Proceedings of the
7th International Conference on Expansive Soils, 1992.

INSTALLATION METHODOLOGY
6. Hoyt, R.M. and S.P. Clemence, Uplift Capacity of Helical Anchors in Soil, Proceedings of the 12th
International Conference on Soil Mechanics and Foundation Engineering, Rio de Janeiro, Brazil, 1989.
7. Perko, Howard A., Energy Method for Predicting Installation Torque of Helical Foundations and
Anchors, Proceedings of Sessions of Geo-Denver 2000, ASCE Geotechnical Special Publication N0.
100, 2000.

Page 5-15 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 PRODUCT DRAWINGS AND RATINGS
Section 6

CONTENTS

CHANCE® HELICAL PILES/ANCHORS................................................... 6-8

TYPE SS SERIES HELICAL PILES/ANCHORS..................................... 6-13
TYPE RS SERIES HELICAL PILES/ANCHORS..................................... 6-31
TYPE SS/RS COMBINATION HELICAL PILES..................................... 6-63
HELICAL PULLDOWN® MICROPILES..................................................... 6-64
DRAWINGS AND RATINGS

REMEDIAL REPAIR BRACKETS FOR CHANCE® HELICAL PILES 6-75

DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted prior to any
installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption, revision, implementation,
use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in its network of installing contractors and
dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of CHANCE® Civil
Construction foundation support products.

Page 6-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® HELICAL PILES/ANCHORS
Introduction

A helical pile/anchor is a factory-manufactured steel deep foundation system

designed to resist axial compression, axial tension, and/or lateral loads from
structures. It consists of a central steel shaft with one or more helical-shaped
bearing plates welded to the central steel shaft. The central steel shaft can be
one-piece (non-extendable) or fully extendable with one or more extension
shafts, couplings, and a bracket/termination that allows for connection to building
structures. A helical pile/anchor is screwed into the ground by application of
torsion and can be extended until a required depth or a suitable bearing soil
stratum is reached. Load is transferred to the soil through the helix bearing plates.
Central steel shafts are available in either Type SS (Square Shaft) series or Type
RS (Round Shaft) series. The Type SS series are available in 1-1/4” to 2-1/4” square

DRAWINGS AND RATINGS

sizes. The Type RS series are available in 2-7/8” to 8” diameter sizes. Type SS/RS
Combo Piles are available for compression applications in soil conditions where
dense/hard soils must be penetrated with softer/loose soils above the bearing
strata. The grouted shaft CHANCE HELICAL PULLDOWN® Micropile series is also
used in applications similar to those requiring the use of the Type SS/RS Combo
Piles, but have the additional benefit of generating capacity via skin friction
along the grout-soil interface in a suitable bond zone stratum. For a complete
list of mechanical ratings and section properties of the central steel shafts, see
the Tables found in each helical pile/anchor Product Family in this Section. Refer
to Section 3, Product Feasibility and Section 6, Installation Methodology for
guidelines on the proper shaft selection based on application, soil conditions, site
accessibility, etc.

Helical pile/anchor sections are joined with bolted couplings. Installation depth is
limited only by soil density and practicality based on economics. A helical bearing
plate or “helix” is one pitch of a screw thread. Most helical piles include more
than one helix plate, and the plates are arranged in a “tapered” configuration
with the smallest helix being in the bottom and the largest helix being on the top.
The large majority of CHANCE helix plates, regardless of their diameter, have a
standard 3” pitch. Being a true helical shape, the helix plates do not auger into the
soil but rather screw into it with minimal soil disturbance. CHANCE helix plates
are “pre-qualified” per the requirements of Table 3 in ICC-ES AC358 Acceptance
Criteria for Helical Pile Systems and Devices, meaning they are generally circular
in plan, have a true helix shape, and are attached perpendicular to the central
steel shaft with the leading and trailing edges parallel. Helix plates are spaced at
Pipe Shaft Pile Square Shaft distances far enough apart that they function independently as individual bearing
Pile/Anchor elements; consequently, the capacity of a particular helix on a helical pile/anchor
shaft is not influenced by the helix above or below it.

Page 6-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 Lead Section and Extensions

The starter section or “lead” section contains the helix plates. This lead section can consist of a single helix or up to
four helices. Additional helix plates can be added, if required, with the use of helical extensions. Standard helix sizes
and areas are shown in Table 6-2 and 6-3 below. Tables 6-2 and 6-3 provide the projected areas of the most common
helix plate diameters. Table 6-2 provides helix areas for Type Square Shaft Helical Piles, and Table 6-3 provides helix
areas for Type Round Shaft Helical Piles. The full plate projected area includes the area occupied by the central steel
shaft. The “area less shaft” is the projected area of the helix plates less the area occupied by the center shaft. Most
all CHANCE® helix plates are provided with a sharp leading edge, which is the front edge of the helix that penetrates
the soils as the helical anchor/pile is advanced clockwise though soil. The sharp leading edge enables the helix to
better slice through tough soils, roots, and seasonally frozen ground. Hubbell Power Systems, Inc. offers several helix
plates with “sea shell” leading edges as special options to the product series. Our standard “sea shell” configuration
that works best in most tough soils conditions is the 90° design as shown below. The sea shell cut is a leading
edge with a “spiral” cut that is very effective when installing helical piles/anchors in debris laden soils, cobbles, and
weathered rock.
DRAWINGS AND RATINGS

However, it is important to remember that the bearing capacity of the helical pile/anchor is reduced because the
bearing surface area is reduced. Therefore,
larger helix diameters or additional helix
STANDARD SEASHELL
plates may be required when using “sea
shell” cut plates. Tables 6-2 and 6-3 include
SHAFT SIZE
SHAFT SIZE
the projected areas of helix plates offered
with the sea shell cut. The helix plates
are arranged on the shaft such that their
diameters increase as they get farther from
the pilot point. The practical limits on the
PLATE DIA. LEADING EDGE
number of helices per pile/anchor is four
to five if placed in a cohesive soil and six if
placed in a cohesionless or granular soil. STANDARD SEASHELL
Pipe Shaft PLATE DIA
Plain extensions are then added in standard PLATE DIA

lengths of 3, 5, 7 and 10
SHAFT SIZE
feet until the lead section penetrates
into the bearing strata. Standard helix
configurations are provided in the
product series tables in this section. SHAFT SIZE
Note that lead time will be
LEADING EDGE
significantly reduced if a standard
helix configuration is selected. Square Shaft
Figure 6-2

Page 6-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
TABLE 6-2: CHANCE® SQUARE SHAFT HELIX PLATE SIZES
AND PROJECTED AREAS BY PRODUCT FAMILY

SQUARE SHAFTS
STANDARD SEASHELL
Diameter AREA w/o HOLE FULL PLATE AREA AREA w/o HOLE FULL PLATE AREA
in. (mm) ft2 (m2) ft2 (m2) ft2 (m2) ft2 (m2)
6 (150) 0.174 (0.0162) 0.185 (0.0172) N/A N/A
8 (200) 0.324 (0.0301) 0.336 (0.0312) 0.304 (0.0282) 0.316 (0.0294)
10 (250) 0.519 (0.0482) 0.531 (0.0493) 0.468 (0.0435) 0.479 (0.0445)
SS125
12 (300) 0.759 (0.0705) 0.771 (0.0716) 0.668 (0.0621) 0.679 (0.0631)
14 (350) 1.037 (0.0963) 1.049 (0.0975) 0.903 (0.0839) 0.915 (0.0850)
16 (406) 1.366 (0.1269) 1.378 (0.128) N/A N/A
6 (150) 0.169 (0.0157) 0.185 (0.0172) 0.156 (0.0145) 0.172 (0.0160)

DRAWINGS AND RATINGS

8 (200) 0.320 (0.0297) 0.336 (0.0312) 0.300 (0.0279) 0.316 (0.0294)
SS5/ 10 (250) 0.515 (0.048) 0.531 (0.0493) 0.463 (0.0430) 0.479 (0.0445)
SS150 12 (300) 0.755 (0.0701) 0.771 (0.0716) 0.663 (0.0616) 0.679 (0.0631)
14 (350) 1.033 (0.0960) 1.049 (0.0975) 0.899 (0.0835) 0.915 (0.0850)
16 (406) 1.362 (0.1265) 1.378 (0.128) N/A N/A
6 (150) 0.163 (0.151) 0.185 (0.0172) N/A N/A
8 (200) 0.314 (0.0292) 0.336 (0.0312) 0.293 (0.0272) 0.316 (0.0294)
10 (250) 0.509 (0.0473) 0.531 (0.0493) 0.457 (0.0425) 0.479 (0.0445)
SS175
12 (300) 0.749 (0.0696) 0.771 (0.0716) 0.658 (0.0611) 0.679 (0.0631)
14 (350) 1.027 (0.0954) 1.049 (0.0975) N/A N/A
16 (406) 1.356 (0.126) 1.378 (0.128) N/A N/A
6 (150) 0.154 (0.0143) 0.185 (0.0172) 0.143 (0.0133) 0.172 (0.0160)
8 (200) 0.305 (0.0283) 0.336 (0.0312) N/A N/A
10 (250) 0.500 (0.0465) 0.531 (0.0493) 0.450 (0.0418) 0.479 (0.0445)
SS200
12 (300) 0.740 (0.0687) 0.771 (0.0716) N/A N/A
14 (350) 1.018 (0.0946) 1.049 (0.0975) N/A N/A
16 (406) 1.349 (0.1253) 1.378 (0.128) N/A N/A
6 (150) 0.149 (0.0138) 0.185 (0.0172) N/A N/A
8 (200) 0.300 (0.0279) 0.336 (0.0312) N/A N/A
10 (250) 0.495 (0.0460) 0.531 (0.0493) N/A N/A
SS225
12 (300) 0.735 (0.0683) 0.771 (0.0716) N/A N/A
14 (350) 1.013 (0.0941) 1.049 (.0975) N/A N/A
16 (406) 1.341 (0.125) 1.378 (0.128) N/A N/A

Page 6-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 TABLE 6-3: CHANCE® PIPE SHAFT HELIX PLATE SIZES
AND PROJECTED AREAS BY PRODUCT FAMILY

PIPE SHAFTS
STANDARD SEASHELL
Diameter AREA w/o HOLE FULL PLATE AREA AREA w/o HOLE FULL PLATE AREA ft2
in. (mm) ft2 (m2) ft2 (m2) ft2 (m2) (m2)
8 (200) 0.290 (0.0269) 0.336 (0.0312) 0.270 (0.0251) 0.316 (0.0294)
10 (250) 0.485 (0.0451) 0.531 (0.0493) 0.433 (0.0402) 0.479 (0.0445)
RS2875 12 (300) 0.725 (0.0674) 0.771 (0.0716) 0.633 (0.0588) 0.680 (0.0632)
14 (350) 1.003 (0.0932) 1.049 (0.0975) 0.869 (0.0807) 0.915 (0.0850)
16 (406) 1.31 (0.122) 1.378 (0.128) N/A N/A
8 (200) 0.268 (0.0249) 0.336 (0.0312) N/A N/A
10 (250) 0.463 (0.0430) 0.531 (0.0493) N/A N/A
RS3500 12 (300) 0.703 (0.0653) 0.771 (0.0716) 0.612 (0.0569) 0.680 (0.0632)
DRAWINGS AND RATINGS

14 (350) 0.981 (0.0911) 1.049 (0.0975) N/A N/A

16 (406) 1.312 (0.122) 1.378 (0.128) N/A N/A
8 (200) 0.224 (0.0208) 0.336 (0.0312) N/A N/A
10 (250) 0.419 (0.0389) 0.531 (0.0493) 0.367 (0.0341) 0.479 (0.0445)
12 (300) 0.659 (0.0612) 0.771 (0.0716) N/A N/A
RS4500
14 (350) 0.937 (0.0871) 1.049 (0.0975) N/A N/A
16 (406) 1.266 (0.1176) 1.378 (0.128) N/A N/A
20 (508) 2.034 (0.1889) 2.146 (0.1994) N/A N/A

PIPE SHAFTS

STANDARD SEASHELL

Diameter AREA w/o HOLE FULL PLATE AREA AREA w/o HOLE FULL PLATE AREA
in. (mm) ft2 (m2) ft2 (m2) ft2 (m2) ft2 (m2)

12 (300) 0.532 (0.0494) 0.771 (0.0716) N/A N/A

14 (350) 0.810 (0.0753) 1.049 (0.0975) N/A N/A
16 (406) 1.139 (0.1058) 1.378 (0.1281) N/A N/A
RS6625 18 (457) 1.508 (0.1402) 1.748 (0.1624) N/A N/A

20 (508) 1.922 (0.1786) 2.146 (0.1994) N/A N/A

22 (559) 2.379 (0.1786) 2.618 (0.2434) N/A N/A

14 (350) 0.643 (0.0598) 1.049 (0.0975) N/A N/A
16 (406) 0.972 (0.0904) 1.378 (0.1281) N/A N/A
18 (457) 1.342 (0.1247) 1.748 (0.1624) N/A N/A
RS8626
20 (508) 1.755 (0.1632) 2.146 (0.1994) N/A N/A
22 (559) 2.212 (0.2056) 2.618 (0.2434) N/A N/A
24 (610) 2.713 (0.2522) 3.119 (0.2899) N/A N/A
16 (406) 0.748 (0.0695) 1.378 (0.1281) N/A N/A
18 (457) 1.117 (0.1039) 1.748 (0.1624) N/A N/A
20 (508) 1.531 (0.1423) 2.146 (0.1994) N/A N/A
RS1075
22 (559) 1.988 (0.1848) 2.618 (0.2434) N/A N/A

24 (610) 2.489 (0.2313) 3.119 (0.2899) N/A N/A

Page 6-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
Table 6-4 is a quick reference guide for the design professional. It relates ASTM D1586 SPT “N60” values for cohesive
and non-cohesive soils to the expected load capacity of various CHANCE Type Square Shaft (SS) and Round Shaft
(RS) Helical Piles. It is intended to be used as a reference guide to enable the designer to quickly determine which
helical pile systems to use for project specific soil conditions and load requirements.

TABLE 6-4: CHANCE® HELICAL PILE/ANCHOR LOAD CAPACITY TABLE

Soil Type Product Family Axial Compression / Tension Capacity*

“N60”- Value** “N60”-Value** Helical Pile Shaft Torque Rating Ultimate Capacity Allowable Capacity
Cohesive Non-Cohesive Size Inches (mm) Ft-lb (N-m) [Pu] Kip (kN) [Pa = 0.5 Pu] Kip (kN)
SS5 5,700
25 – 35 25 - 30 57 (254) 28.5 (127)
1-1/2 (38) (7,730)

SS150 7,000
25 - 40 25 - 35 70 (312) 35 (156)
1-1/2 (38) (9,500)

SS175 10,500

DRAWINGS AND RATINGS

35 - 50 35 -40 105 (467) 52.5 (234)
1-3/4 (44) (14,200)

SS200 16,000
50 - 70 40 - 60 160 (712) 80 (356)
2 (51) (21,700)

SS225 21,000
70 - 90 60 - 80 210 (934) 105 (467)
2-1/4 (57) (28,475)

RS2875.203 5,500
20 - 25 15 - 20 49.5 (220) 24.75 (110)
2-7/8 (73) (7,500)

RS2875.276 8,000
25 - 35 20 - 30 72 (320) 36 (160)
2-7/8 (73) (10,850)

RS3500.300 13,000
35 - 40 30 – 35 91 (405) 45.5 (202)
3-1/2 (89) (17,600)

RS4500.337 23,000
35 – 40 30 – 35 138 (614) 69 (307)
4-1/2 (114) (31,200)

* Based on Torque Rating – Axial Compression / Tension Capacity = Torque Rating x Kt. Well documented correlations with installation
torque are recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. “Default” Kt for Type SS = 10 ft-1 (33 m-1).
“Default” Kt for Type RS2875 Series = 9 ft-1 (30 m-1); for Type RS3500.300 = 7 ft-1 (23 m-1); for Type RS4500.337 = 6 ft-1 (20 m-1).
** “N60” Values or Blow Count from the Standard Penetration Test per ASTM D1586.

NOTES:
1. The table above is given as a guideline only. The capacity of CHANCE Helical Pile/Anchors may vary depending on, but not limited to,
water table elevation and changes to that elevation, changes in soil conditions and soil layer thicknesses.
2. Achievable capacities could be higher or lower than stated in the table depending on:
a. Site specific conditions
b. On-site testing verification
c. HELICAL PULLDOWN® Micropiles can achieve higher capacities in compression. On-site testing should be performed to verify
additional pile capacity.
d. This chart is to be used for preliminary design assessment only. Capacities should be verified on per project, site-specific basis by
a registered design professional.
3. The above chart represents the hardest or densest soil conditions that the helical pile can be installed into. The helical pile will
likely achieve its torque rating quickly upon encountering the highest N values indicated above.

Page 6-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE SS125 HELICAL PILES AND ANCHORS
40 kip Ultimate – 20 kip Allowable Capacity
Installation Torque Rating – 4,000 ft-lb

SS125
Multi-Purpose 1-1/4 inch Solid Round-Cornered-Square Steel Shaft with integrally formed square upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type SS125 Helical Piles and Anchors have 40 kip ultimate capacity and 20 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Solid square shaft helical piles
and anchors provide greater penetration into bearing soils and increased axial capacity in firm soils compared to pipe shaft
helical piles with similar torque strength. Strength calculations are based on a design corrosion level of 50 years for most
soil conditions. CHANCE Type SS Helical Piles and Anchors have a longer service life than do pipe shaft piles because of
their reduced surface area. CHANCE Type SS Helical Piles and Anchors feature sharpened leading edge helix plates that are
circular in plan to provide uniform load bearing in most soil conditions. Helix plates can be equipped with “sea-shell” cuts
on the leading edge to enhance penetration through dense soils with occasional cobbles and debris. Custom lengths and
helix configurations are available upon request. See below for additional information and other sections of this Technical
Manual for specifications and design details.
DRAWINGS AND RATINGS

1 - 1/4”
Square Hole accepts
Shaft 5/8” Dia.
Coupling Bolt

True
Helix Up to
3 Dia.
Form 10’ - 0
Spacing
Long
Typical

3” Pitch
Sharp
Leading 5/8” Dia.
Edge Structural
Grade Bolt

3.5”
2.2”
45˚ Pilot Point

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
SS125 Helical Pile and Anchor Specifications & Available Configurations
Shaft – Round-Cornered-Square (RCS) 1-1/4 inch solid steel shaft
produced exclusively for CHANCE products.
Coupling - forged as a deep socket from the steel shaft material as
an integral part of the extension, connected with structural bolts.
Helix - 3/8 inch Thick: ASTM A572, or A1018, or A656 with
minimum yield strength of 50 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power
Systems, Inc. for Helical Piles and Anchors.
Available Helix Diameters: 6, 8, 10, 12, or 14 inches.
All helix plates are spaced 3 times the diameter of the preceding
(lower) helix unless otherwise specified.
The standard helix plate has straight sharpened leading edges
or can be ordered with a “sea shell” cut. The “sea shell” cut is
best suited when it is necessary to penetrate soils with fill debris,
cobbles, or fractured rock.
Configurations:
· Single, double, and triple Lead Sections, 1 and 5 feet long
· Plain Extensions, 3, 5, 7, and 10 feet long

DRAWINGS AND RATINGS

· Extensions with Helix Plates, 3-1/2 feet long, single and
double helix

Helical products are Hot Dip Galvanized per ASTM A153 Class B-1.

NOTE: Helical piles shall be installed to appropriate depth in

suitable bearing stratum as determined by the geotechnical
engineer or local jurisdictional authority. Torque correlated
capacities are based on installing the pile to its torque rating,
using consistent rate of advance and RPM. A minimum factor of
safety of 2 is recommended for determining allowable capacity CHANCE Type SS125
from correlations. Deflections of 0.25 to 0.50 inches are typical at
allowable capacity.
Helical Pile Shaft Cross-Section
Figure 6-3

Nominal, LRFD Design and ASD Allowable Strengths of SS125 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Thickness Nominal Strength LRFD Design Strength ASD Allowable Strength
in (mm) in (mm) kip (kN) kip (kN) kip (kN)
6 (150) 0.375 (9.5) 37.4 (166.3) 28.05 (124.7) 18.7 (83.2)
8 (200) 0.375 (9.5) 37.4 (166.3) 28.05 (124.7) 18.7 (83.2)
10 (250) 0.375 (9.5) 46.6 (207.3) 34.9 (155.5) 23.3 (103.6)
12 (300) 0.375 (9.5) 44.1 (196.2) 33.1 (147.2) 22.1 (98.3)
14 (350) 0.375 (9.5) 36.0 (160.1) 27.0 (120.1) 18.0 (80.1)

For SI: 1 kip = 4.448 kN.

1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type SS125 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kip (kN)
Section Type & Firm Soil Soft Soil
Helix Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
Lead, Single Helix See Helix Strength Table 27.3 (121.4) 24.6 (109.4) 13.4 (59.6) 12.0 (53.4) 6.8 (30.2) 6.2 (27.6)
Lead, Multi-Helix 53.6 (238.4) 48.2 (214.4) 27.3 (121.4) 24.6 (109.4)
13.4 (59.6) 12.0 (53.4) 6.8 (30.2) 6.2 (27.6)
Extension 53.6 (238.4) 48.2 (214.4) 27.3 (121.4) 24.6 (109.4)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS125 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled Round-Cornered-Square (RCS) Solid
SHAFT Steel Bars per ASTM A29; modified AISI 1530
with 90 ksi minimum yield strength
Corroded
Shaft Size 1.25 in 32 mm
1.237 in 31.4 mm
Corroded
Moment of Inertia (I) 0.20 in4 8.3 cm4
0.191 in4 7.95 cm4
Corroded
Shaft Area (A) 1.55 in2 10.0 cm2
1.52 in2 9.81 cm2
Corroded
Section Modulus (Sx-x) 0.32 in3 5.3 cm3
0.31 in3 5.1 cm3
DRAWINGS AND RATINGS

Corroded
Perimeter 4.79 in 12.17 cm
4.74 in 12.0 cm
Coupling Integral Forged Square Deep Socket
One 5/8 inch Diameter ASTM A325 Type 1
Coupling Bolts Hex Head Bolt with Threads Excluded
from Shear Planes
0.375 inch Thick, Formed on Matching
Helix Plates
Metal Dies, ASTM A572 Grade 50 or better
Hot Dip Galvanized per ASTM A153 Class B-1,
Coatings
3.1 mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
10 ft-1 33 m-1
Factor
Torque Rating 4,000 ft-lb 5,400 N-m
STRUCTURAL CAPACITY Assembly of SS125
Nominal LRFD Design Figure 6-4
Tension Strength
50 kip 222 kN 37.5 kip 167 kN
Allowable Tension
25 kip 111 kN
Strength
TORQUE CORRELATED CAPACITY
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 40 kip 178 kN 20 kip 89 kN

ASD Allowable Compression Strengths of CHANCE® Type SS125 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kip (kN)
Section Type & Helix Count Firm Soil Soft Soil
Fixed Pinned Fixed Pinned
Lead, Single Helix See Helix Strength Table 16.4 (72.9) 8.0 (35.6) 4.1 (18.2)
Lead, Multi-Helix 32.1 (142.8) 16.4 (72.9) 8.0 (35.6) 4.1 (18.2)
Extension 32.1 (142.8) 16.4 (72.9) 8.0 (35.6) 4.1 (18.2)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE SS5 HELICAL PILES AND ANCHORS
57 kip Ultimate – 28.5 kip Allowable Capacity

SS5
Installation Torque Rating – 5,700 ft-lb
Multi-Purpose 1-1/2 inch Solid Round-Cornered-Square Steel Shaft with integrally formed square upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type SS5 Helical Piles and Anchors have 57 kip ultimate capacity and 28.5 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Solid square shaft helical piles
and anchors provide greater penetration into bearing soils and increased axial capacity in firm soils compared to pipe shaft
helical piles with similar torque strength. Strength calculations are based on a design corrosion level of 50 years for most
soil conditions. CHANCE Type SS Helical Piles and Anchors have a longer service life than do pipe shaft piles because of their
reduced surface area. CHANCE Type SS Helical Piles and Anchors feature sharpened leading edge helix plates that are circular
in plan to provide uniform load bearing in most soil conditions. Helix plates can be equipped with “sea-shell” cuts on the
leading edge to enhance penetration through dense soils with occasional cobbles and debris. Custom lengths and helix
configurations are available upon request. See below for additional information and other sections of this Technical Manual

DRAWINGS AND RATINGS

for specifications and design details.

1 - 1/2”
Square Hole accepts
Shaft 3/4” Dia.
Coupling Bolt

True
Helix Up to
3 Dia.
Form 10’ - 0
Spacing
Long
Typical

3” Pitch
Sharp
Leading 3/4” Dia.
Edge Structural
Grade Bolt

3.5”
2.2”
45˚ Pilot Point

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS5 Helical Pile and Anchor Specifications & Available Configurations
Shaft – Round-Cornered-Square (RCS) 1-1/2 inch solid steel shaft
produced exclusively for CHANCE products.
Coupling - forged as a deep socket from the steel shaft material
as an integral part of the extension, connected with structural
bolts.
Helix - 3/8 inch Thick: ASTM A572, or A1018, or A656 with
minimum yield strength of 50 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power
Systems, Inc. for Helical Piles and Anchors.
Available Helix Diameters: 6, 8, 10, 12, 14, or 16 inches.
All helix plates are spaced 3 times the diameter of the preceding
(lower) helix unless otherwise specified.
The standard helix plate has straight sharpened leading edges
or can be ordered with a “sea shell” cut. The “sea shell” cut is
best suited when it is necessary to penetrate soils with fill debris,
cobbles, or fractured rock.
Configurations:
· Single, double, triple, and quad helix Lead Sections, 3, 5, 7,
DRAWINGS AND RATINGS

and 10 feet long

· Plain Extensions, 3, 5, 7, and 10 feet long
· Extensions with Helix Plates, 3 and 5 feet long, single helix
Helical products are Hot Dip Galvanized per ASTM
A153 Class B-1.
NOTE: Helical piles shall be installed to appropriate depth in
suitable bearing stratum as determined by the geotechnical
engineer or local jurisdictional authority. Torque correlated CHANCE Type SS5
capacities are based on installing the pile to its torque rating, Helical Pile Shaft Cross-Section
using consistent rate of advance and RPM. A minimum factor of Figure 6-5
safety of 2 is recommended for determining allowable capacity
from correlations. Deflections of 0.25 to 0.50 inches are typical at
allowable capacity.

Nominal, LRFD Design and ASD Allowable Strengths of SS5 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
6 (150) 0.375 (9.5) 57.3 (254.9) 43.0 (191.2) 28.7 (127.7)
8 (200) 0.375 (9.5) 57.3 (254.9) 43.0 (191.2) 28.7 (127.7)
10 (250) 0.375 (9.5) 47.7 (212.2) 35.8 (159.2) 23.8 (105.6)
12 (300) 0.375 (9.5) 44.2 (196.6) 33.2 (147.5) 22.1 (98.3)
14 (350) 0.375 (9.5) 54.1 (240.7) 40.6 (180.5) 27.1 (120.6)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type SS5 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kip (kN)
Section Type & Firm Soil Soft Soil
Helix Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
Single 6 & Single 6 &
8 in 8 in
Lead, Single Helix See Helix Strength Table 54.4 (242.0) 48.9 (217.5) 26.6 (118.3) 24.0 (106.8) 13.6 (60.5) 12.2 (54.3)
For Other Helix Diameters,
See Helix Strength Table
Lead, Multi-Helix 89.8 (399.5) 80.8 (359.4) 54.4 (242.0) 48.9 (219.5)
26.6 (118.3) 24.0 (106.8) 13.6 (60.5) 12.2 (54.3)
Extension 89.8 (399.5) 80.8 (359.4) 54.4 (242.0) 48.9 (219.5)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with

IBC Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft
capacity.

Page 6-12 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS5 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled Round-Cornered-Square (RCS) Solid
SHAFT Steel Bars per ASTM A29; modified AISI 1044
with 70 ksi minimum yield strength
Corroded
Shaft Size 1.50 in 38 mm
1.487 in 37.8 mm
4 4 Corroded
Moment of Inertia (I) 0.40 in 16.5 cm
0.38 in4 15.6 cm4
2 2 Corroded
Shaft Area (A) 2.2 in 14.2 cm
2.16 in2 13.94 cm2
Corroded
Section Modulus (Sx-x) 0.53 in3 8.7 cm3
0.40 in3 6.6 cm3
Corroded
Perimeter 5.6 in 14.2 cm
5.5 in 14 cm
Coupling Integral Forged Square Deep Socket

DRAWINGS AND RATINGS

One ¾ inch Diameter ASTM A325 Type 1 Hex
Coupling Bolts Head Bolt with Threads Excluded from Shear
Planes
0.375 inch Thick, Formed on Matching Metal
Helix Plates
Dies, ASTM A572 Grade 50 or better
Hot Dip Galvanized per ASTM A153 Class B-1,
Coatings
3.1 mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
10 ft-1 33 m-1
Factor
Torque Rating 5,700 ft-lb 7,730 N-m
STRUCTURAL CAPACITY
Assembly of SS5
Figure 6-6
Nominal LRFD Design
Tension Strength
70 kip 312 kN 52.5 kip 234 kN
Allowable Tension
35 kip 156 kN
Strength
TORQUE CORRELATED CAPACITY
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
57 kip 254 kN 28.5 kip 127 kN
Tension / Compression

ASD Allowable Compression Strengths of CHANCE® Type SS5 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kip (kN)
Section Type & Helix Count Firm Soil Soft Soil
Fixed Pinned Fixed Pinned
Lead, Single Helix See Helix Strength Table See Helix Strength Table 16 (71.2) 8.1 (36.0)
Lead, 2-Helix 8”-10” 52.5 (233.5)
Lead, 2-Helix 10”-12” 45.9 (204.2)
32.6 (145.0) 16 (71.2) 8.1 (36.0)
Lead, 2-Helix 12”-14” 49.9 (222.0)
Lead, 2-Helix 14”-14” 53.8 (239.3)
Lead, Multi-Helix 53.8 (239.3) 32.6 (145.0) 16 (71.2) 8.1 (36.0)
Extension 53.8 (239.3) 32.6 (145.0) 16 (71.2) 8.1 (36.0)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE SS150 HELICAL PILES AND ANCHORS
70 kip Ultimate – 35 kip Allowable Capacity
Installation Torque Rating – 7,000 ft-lb

SS150
Multi-Purpose 1-1/2 inch Solid Round-Cornered-Square Steel Shaft with integrally formed square upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type SS150 Helical Piles and Anchors have 70 kip ultimate capacity and 35 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Solid square shaft helical piles
and anchors provide greater penetration into bearing soils and increased axial capacity in firm soils compared to pipe shaft
helical piles with similar torque strength. Strength calculations are based on a design corrosion level of 50 years for most
soil conditions. CHANCE Type SS Helical Piles and Anchors have a longer service life than do pipe shaft piles because of
their reduced surface area. CHANCE Type SS Helical Piles and Anchors feature sharpened leading edge helix plates that are
circular in plan to provide uniform load bearing in most soil conditions. Helix plates can be equipped with “sea-shell” cuts
on the leading edge to enhance penetration through dense soils with occasional cobbles and debris. Custom lengths and
helix configurations are available upon request. See below for additional information and other sections of this Technical
DRAWINGS AND RATINGS

Manual for specifications and design details.

1 - 1/2”
Square Hole accepts
Shaft 3/4” Dia.
Coupling Bolt

True
Helix Up to
3 Dia.
Form 10’ - 0
Spacing
Long
Typical

3” Pitch
Sharp
Leading 3/4” Dia.
Edge Structural
Grade Bolt

3.5”
2.2”
45˚ Pilot Point

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-14 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
SS150 Helical Pile and Anchor Specifications & Available Configurations
Shaft – Round-Cornered-Square (RCS) 1-1/2 inch solid steel
shaft produced exclusively for CHANCE products.
Coupling - forged as a deep socket from the steel shaft
material as an integral part of the extension, connected with
structural bolts.
Helix - 3/8 inch Thick: ASTM A656 or A1018, with minimum
yield strength of 80 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power
Systems, Inc. for Helical Piles and Anchors.
Available Helix Diameters: 6, 8, 10, 12, and 14 inch.
All helix plates are spaced 3 times the diameter of the
preceding (lower) helix unless otherwise specified.
The standard helix plate has straight sharpened leading edges
or can be ordered with a “sea shell” cut. The “sea shell” cut
is best suited when it is necessary to penetrate soils with fill
debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, and quad helix Lead Sections, 3, 5, 7, and

DRAWINGS AND RATINGS

10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 5, 7, and 10 feet long, single and
multi-helix
Helical products are Hot Dip Galvanized per ASTM A153 Class
B-1.

NOTE: Helical piles shall be installed to appropriate depth in

suitable bearing stratum as determined by the geotechnical
engineer or local jurisdictional authority. Torque correlated
capacities are based on installing the pile to its torque rating, CHANCE Type SS150
using consistent rate of advance and RPM. A minimum factor Helical Pile Shaft Cross-Section
of safety of 2 is recommended for determining allowable Figure 6-7
capacity from correlations. Axial Deflections of 0.25 to 0.50
inches are typical at allowable capacity.

Nominal, LRFD Design and ASD Allowable Strengths of SS150 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength, LRFD Design Strength, ASD Allowable Strength,
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
6 (150) 0.375 (9.5) 57.7 (257) 43.3 (192.8) 28.8 (128)
8 (200) 0.375 (9.5) 57.7 (257) 43.3 (192.8) 28.8 (128)
10 (250) 0.375 (9.5) 61.9 (275) 46.4 (206.3) 30.9 (137)
12 (300) 0.375 (9.5) 49.7 (221) 37.3 (165.8) 24.8 (110)
14 (350) 0.375 (9.5) 52.9 (235) 39.7 (176.3) 26.5 (118)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type SS150 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths, kip (kN)
Section Type & Firm Soil Soft Soil
Helix Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
Single 6, 8, or 10 Single 6, 8, or 10
Lead, Single inch – 54.4 (242) inch – 48.9 (218)
See Helix Strength Table 26.6 (118) 24.0 (107) 13.6 (60.5) 12.2 (54)
Helix For Other Helix Diameters, See Helix
Strength Table
Lead, Multi-Helix
99.5 (443) 89.5 (398) 54.4 (242) 48.9 (218) 26.6 (118) 24.0 (107) 13.6 (60.5) 12.2 (54)
Extension
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-15 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS150 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled Round-Cornered-Square (RCS) Solid
SHAFT Steel Bars per ASTM A29; modified AISI 1530
with 90 ksi minimum yield strength
Corroded
Shaft Size 1.50 in 38 mm
1.487 in 37.8 mm
Corroded
Moment of Inertia (I) 0.40 in4 16.5 cm4
0.38 in4 15.6 cm4
Corroded
Shaft Area (A) 2.2 in2 14.2 cm2
2.16 in2 13.94 cm2
Corroded
Section Modulus (Sx-x) 0.53 in3 8.7 cm3
0.40 in3 6.6 cm3
Corroded
Perimeter 5.6 in 14.2 cm
5.5 in 14.0 cm
Coupling Integral Forged Square Deep Socket
DRAWINGS AND RATINGS

One 3/4 inch Diameter ASTM A325 Type 1

Coupling Bolts Hex Head Bolt with Threads Excluded
from Shear Planes
0.375 inch Thick, Formed on Matching
Helix Plates
Metal Dies, ASTM A656 Grade 80 or better
Hot Dip Galvanized per ASTM A153 Class B-1,
Coatings
3.1 mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
10 ft-1 33 m-1
Factor
Torque Rating 7,000 ft-lb 9,500 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
70 kip 312 kN 52.5 kip 234 kN
Assembly of SS150
Allowable Tension Figure 6-8
35 kip 156 kN
Strength
TORQUE CORRELATED CAPACITY
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
70 kip 312 kN 35 kip 156 kN
Tension / Compression

ASD Allowable Compression Strengths of CHANCE® Type SS150 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength, kip (kN)
Section Type & Helix Count Firm Soil Soft Soil
Fixed Pinned Fixed Pinned
Lead, Single Helix See Helix Strength Table Above See Helix Strength Table Above 16 (71) 8.1 (36)
Lead, 2-Helix 8”-10” 59.6 (265)
Lead, 2-Helix 10”-12” 55.7 (248)
Lead, 2-Helix 12”-14” 51.3 (228)
32.6 (145) 16 (71) 8.1 (36)
Lead, 2-Helix 14”-14” 53.0 (236)
Lead, Multi-Helix 59.6 (265)
Extension 59.6 (265)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-16 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE SS175 HELICAL PILES AND ANCHORS
105 kip Ultimate – 52.5 kip Allowable Capacity
Installation Torque Rating – 10,500 ft-lb
Multi-Purpose 1-3/4 inch Solid Round-Cornered-Square Steel Shaft with integrally formed square upset sockets

SS175
Description:
Hubbell Power Systems, Inc., CHANCE Type SS175 Helical Piles and Anchors have 105 kip ultimate capacity and 52.5 kip
working or allowable capacity in compression and 100 kip ultimate capacity and 50 kip working or allowable capacity
in tension. This capacity is based on well documented correlations with installation torque, which is recognized as one
method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions couple together to extend the
helix bearing plates to the required load bearing stratum. Solid square shaft helical piles and anchors provide greater
penetration into bearing soils and increased axial capacity in firm soils compared to pipe shaft helical piles with similar
torque strength. Strength calculations are based on a design corrosion level of 50 years for most soil conditions. CHANCE
Type SS Helical Piles and Anchors have a longer service life than do pipe shaft piles because of their reduced surface area.
CHANCE Type SS Helical Piles and Anchors feature sharpened leading edge helix plates that are circular in plan to provide
uniform load bearing in most soil conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to
enhance penetration through dense soils with occasional cobbles and debris. Custom lengths and helix configurations are

DRAWINGS AND RATINGS

available upon request. See below for additional information and other sections of this Technical Manual for specifications
and design details.

1 - 3/4”
Square Hole accepts
Shaft 7/8” Dia.
Coupling Bolt

True
Helix Up to
3 Dia.
Form 10’ - 0
Spacing
Long
Typical

3” Pitch
Sharp
Leading 7/8” Dia.
Edge Structural
Grade Bolt

4”
2”
45˚ Pilot Point

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-17 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS175 Helical Pile and Anchor Specifications & Available Configurations
Shaft – Round-Cornered-Square (RCS) 1-3/4 inch solid steel shaft produced
exclusively for CHANCE products.
Coupling – forged as a deep socket from the steel shaft material as an integral part
of the extension, connected with structural bolts.
Helix - 3/8 & 1/2 inch Thick: ASTM A656, or A1018 with minimum yield strength of
80 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for Helical
Piles and Anchors.
Available Helix Diameters: 6, 8, 10, 12, or 14 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The standard helix plate has straight sharpened leading edges or can be ordered
with a “sea shell” cut. The “sea shell” cut is best suited when it is necessary to
penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, and quad helix Lead Sections, 3, 5, 7, and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 3, 5, 7, and 10 feet long, single and multi-helix
DRAWINGS AND RATINGS

Helical products are Hot Dip Galvanized per ASTM A153 Class B-1.
NOTE: Helical piles shall be installed to appropriate depth in suitable bearing stratum
as determined by the geotechnical engineer or local jurisdictional authority. Torque
correlated capacities are based on installing the pile to its torque rating, using CHANCE Type SS175
consistent rate of advance and RPM. A minimum factor of safety of 2 is recommended Helical Pile Shaft Cross-Section
for determining allowable capacity from correlations. Deflections of 0.25 to 0.50 Figure 6-9
inches are typical at allowable capacity.

Nominal, LRFD Design and ASD Allowable Strengths of SS175 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength, LRFD Design Strength, ASD Allowable Strength,
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
6 (150) 0.5 (13) 123.3 (548.5) 92.5 (411.4) 61.6 (274)
8 (200) 0.5 (13) 123.3 (548.5) 92.5 (411.4) 61.6 (274)
10 (250) 0.375 (9.5) 66.1 (294) 49.6 (220.5) 33.1 (147.2)
12 (300) 0.375 (9.5) 57.5 (255.8) 43.1 (191.9) 28.7 (127.7)
14 (350) 0.375 (9.5) 51.8 (230.4) 38.9 (172.8) 25.9 (115.2)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type SS175 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths, kip (kN)
Section Type & Firm Soil Soft Soil
Helix Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
Lead, Single 50.5 45.4 25.8 23.2
See Helix Strength Table See Helix Strength Table
Helix (224.6) (201.9) (114.8) (103.2)
Lead, 2-Helix 164.3 147.8
8”-10” (730.8) (657.4)
Lead, 2-Helix 123.6 111.2
10”-12” (549.8) (494.6)
Lead, 2-Helix 109.3 98.4
12”-14” (486.2) (437.7) 50.5 45.4 25.8 23.2
103.0 (458.2) 92.7 (412.4)
Lead, 2-Helix 103.6 93.4 (224.6) (201.9) (114.8) (103.2)
14”-14” (460.8) (415.5)
164.3 147.8
Lead, Multi-Helix
(730.8) (657.4)
164.3 147.8
Extension
(730.8) (657.4)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-18 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS175 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled Round-Cornered-Square (RCS) Solid
SHAFT Steel Bars per ASTM A29; modified AISI 1530
with 90 ksi minimum yield strength
Corroded
Shaft Size 1.75 in 44.4 mm
1.737 in 44 mm
4 4 Corroded
Moment of Inertia (I) 0.75 in 31.1 cm
0.725 in4 30.1 cm4
Corroded
Shaft Area (A) 3.1 in2 19.4 cm2
2.97 in2 19.16 cm2
Corroded
Section Modulus (Sx-x) 0.85 in3 13.9 cm3
0.835 in3 13.65 cm3
Corroded
Perimeter 6.6 in 16.7 cm
6.5 in 16.5 cm
Coupling Integral Forged Square Deep Socket
One 7/8 inch Diameter ASTM A193 Grade B7
Coupling Bolts Hex Head Bolt with Threads Excluded from
Shear Planes

DRAWINGS AND RATINGS

0.375 & 0.5 inch Thick, Formed on Matching
Helix Plates
Metal Dies, ASTM A656 Grade 80 or better
Hot Dip Galvanized per ASTM A153 Class B-1,
Coatings
3.1 mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
10 ft-1 33 m-1
Factor
Torque Rating 10,500 ft-lb 14,240 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
100 kip 445 kN 75 kip 334 kN
Allowable Tension
50 kip 222 kN
Strength
TORQUE CORRELATED CAPACITY Assembly of SS175
Capacity Limit Based Ultimate Allowable Figure 6-10
on Torque Correlation,
105 kip 467 kN 52.5 kip 234 kN
Tension / Compression

ASD Allowable Compression Strengths of CHANCE® Type SS150 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength, kip (kN)
Section Type & Helix Count Firm Soil Soft Soil
Fixed Pinned Fixed Pinned
Lead, Single Helix 30.2 (134.3)
Lead, Single 12” Helix See Helix Strength Table Above See Helix Strength Table Above 28.7 (127.7) 15.4 (68.5)
Lead, Single 14” Helix 25.9 (115.2)
Lead, 2-Helix 8”-10” 94.7 (421.2) 61.7 (274.5)
Lead, 2-Helix 10”-12” 61.8 (274.9) 61.7 (274.5)
30.2 (134.3) 15.4 (68.5)
Lead, 2-Helix 12”-14” 54.6 (242.9) 54.6 (242.9)
Lead, 2-Helix 14”-14” 51.8 (230.4) 51.8 (230.4)
Lead, Multi-Helix 98.4 (437.7) 61.7 (274.5) 30.2 (134.3) 15.4 (68.5)
Extension 98.4 (437.7) 61.7 (274.5) 30.2 (134.3) 15.4 (68.5)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-19 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE SS200 HELICAL PILES AND ANCHORS
160 kip Ultimate – 80 kip Allowable Capacity
Installation Torque Rating – 16,000 ft-lb
Multi-Purpose 2 inch Solid Round-Cornered-Square Steel Shaft with integrally formed square upset sockets

Description:

SS200
Hubbell Power Systems, Inc.,CHANCE Type SS200 Helical Piles and Anchors have 160 kip ultimate capacity and 80 kip
working or allowable capacity in compression and 150 kip ultimate capacity and 75 kip working or allowable capacity in
tension. This capacity is based on structural strength ratings and well documented correlations with installation torque,
which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions couple
together to extend the helix bearing plates to the required load bearing stratum. Solid square shaft helical piles and
anchors provide greater penetration into bearing soils and increased axial capacity in firm soils compared to pipe shaft
helical piles with similar torque strength. Strength calculations are based on a design corrosion level of 50 years for most
soil conditions. CHANCE Type SS Helical Piles and Anchors have a longer service life than do pipe shaft piles because of
their reduced surface area. CHANCE Type SS Helical Piles and Anchors feature sharpened leading edge helix plates that are
circular in plan to provide uniform load bearing in most soil conditions. Helix plates can be equipped with “sea-shell” cuts
DRAWINGS AND RATINGS

on the leading edge to enhance penetration through dense soils with occasional cobbles and debris. Custom lengths and
helix configurations are available upon request. See below for additional information and other sections of this Technical
Manual for specifications and design details.

True
Helix
Form

Hole accepts
2” 3 Dia. 1-1/8” DIa.
Square Spacing Coupling Bolt
Shaft Typical
Up to
10’ - 0
Long

3” Pitch Sharp 1-1/8” Dia.

Leading Edge Structural
Grade Bolt

5”
2.5”
45˚ Pilot Point

Triple Helix Quad Helix Helical Extension Plain Exension Coupling

Lead Section Lead Section Section Section Detail

Page 6-20 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
SS200 Helical Pile and Anchor Specifications &
Available Configurations
Shaft – Round-Cornered-Square (RCS) 2 inch solid steel shaft produced
exclusively for CHANCE products.
Coupling - forged as a deep socket from the steel shaft material as an
integral part of the extension, connected with structural bolts.
Helix – ½ inch Thick: ASTM A656, or A1018 with minimum yield strength of
80 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for
Helical Piles and Anchors.
Available Helix Diameters: 6, 8, 10, 12, and 14 inch.
All helix plates are spaced 3 times the diameter of the preceding (lower)
helix unless otherwise specified.
The standard helix plate has straight sharpened leading edges or can be
ordered with a “sea shell” cut. The “sea shell” cut is best suited when it is
necessary to penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Triple, and quad helix Lead Sections, 5, 7, 8, and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long

DRAWINGS AND RATINGS

Extensions with Helix Plates, 3, 7, and 10 feet long, single and multi-helix
Helical products are Hot Dip Galvanized per ASTM A153 Class B-1. CHANCE Type SS200
NOTE: Helical piles shall be installed to appropriate depth in suitable bearing Helical Pile Shaft Cross-Section
stratum as determined by the geotechnical engineer or local jurisdictional Figure 6-11
authority. Torque correlated capacities are based on installing the pile to its
torque rating, using consistent rate of advance and RPM. A minimum factor
of safety of 2 is recommended for determining allowable capacity from
correlations. Axial deflections of 0.25 to 0.50 inches are typical at allowable
capacity.

Nominal, LRFD Design and ASD Allowable Strengths of SS220 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength, LRFD Design Strength, ASD Allowable Strength,
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
6 (150) 0.5 (13) 154 (685) 115.5 (513.8) 77 (342.5)
8 (200) 0.5 (13) 154 (685) 115.5 (513.8) 77 (342.5)
10 (250) 0.5 (13) 122.8 (546.2) 92.1 (409.7) 61.4 (273.1)
12 (300) 0.5 (13) 131.3 (584) 98.5 (438) 65.6 (291.8)
14 (350) 0.5 (13) 115.3 (512.9) 86.5 (384.7) 57.6 (256.2)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type SS200 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths, kip (kN)
Section Type & Firm Soil Soft Soil
Helix Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
Lead, Single 85.6 77.1 43.7 39.3
See Helix Strength Table See Helix Strength Table
Helix (380.8) (342.9) (194.4) (174.8)
Lead, 2-Helix 239.6 215.6
8”-10” (1065.8) (959)
Lead, 2-Helix 239.6 215.6
10”-12” (1065.8) (959)
Lead, 2-Helix 239.6 215.6
12”-14” (1065.8) (959) 86.6 77.1 43.7 39.3
Lead, 2-Helix 230.6 207.6 167.5 (745) 150.8 (670.8)
(385.2) (342.9) (194.4) (174.8)
14”-14” (1025.8) (923.5)
239.6 215.6
Lead, Multi-Helix
(1065.8) (959)
239.6 215.6
Extension
(1065.8) (959)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with

IBC Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft
capacity.

Page 6-21 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS200 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled Round-Cornered-Square (RCS) Solid
SHAFT Steel Bars per ASTM A29; modified AISI 1530
with 90 ksi minimum yield strength
Corroded
Shaft Size 2 in 51 mm
1.971 in 50 mm
Corroded
Moment of Inertia (I) 1.26 in4 52.4 cm4
1.19 in4 49.53 cm4
Corroded
Shaft Area (A) 3.9 in2 25.3 cm2
3.81 in2 24.58 cm2
Corroded
Section Modulus (Sx-x) 1.26 in3 20.6 cm3
1.21 in3 19.83 cm3
Corroded
Perimeter 7.5 in 18.9 cm
7.36 in 18.69 cm
Coupling Integral Forged Square Deep Socket
One 1-1/8 inch Diameter ASTM A193 Grade
DRAWINGS AND RATINGS

Coupling Bolts B7 Hex Head Bolt with Threads Excluded from

Shear Planes
0.5 inch Thick, Formed on Matching Metal
Helix Plates
Dies, ASTM A656 or A1018 Grade 80
Hot Dip Galvanized per ASTM A153 Class B-1,
Coatings
3.1 mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
10 ft-1 33 m-1
Factor
Torque Rating 16,000 ft-lb 21,700 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
150 kip 668 kN 112.5 kip 500 kN
Allowable Tension
75 kip 334 kN
Strength Assembly of SS200
TORQUE CORRELATED CAPACITY Figure 6-12
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 160 kip 712 kN 80 kip 356 kN

ASD Allowable Compression Strengths of CHANCE® Type SS200 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kip (kN)
Section Type & Helix Count Firm Soil Soft Soil
Fixed Pinned Fixed Pinned
Lead, Single Helix See Helix Strength Table Above See Helix Strength Table Above 51.3 (228.2) 26.2 (116.5)
Lead, 2-Helix 8”-10” 138.4 (615.6)
Lead, 2-Helix 10”-12” 127.0 (765.1)
100.3 (446.1) 51.3 (228.2) 26.2 (116.5)
Lead, 2-Helix 12”-14” 123.2 (548)
Lead, 2-Helix 14”-14” 115.2 (512.4)
Lead, Multi-Helix 143.5 (638.3) 100.3 (446.1) 51.3 (228.2) 26.2 (116.5)
Extension 143.5 (638.3) 100.3 (446.1) 51.3 (228.2) 26.2 (116.5)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-22 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE SS225 HELICAL PILES AND ANCHORS
210 kip Ultimate – 105 kip Allowable Capacity
Installation Torque Rating – 21,000 ft-lb
Multi-Purpose 2-1/4 inch Solid Round-Cornered-Square Steel Shaft with integrally formed square upset sockets

Description:

SS225
Hubbell Power Systems, Inc., CHANCE Type SS225 Helical Piles and Anchors have 210 kip ultimate capacity and 105 kip
working or allowable capacity in compression and 200 kip ultimate capacity and 100 kip working or allowable capacity in
tension. This capacity is based on structural strength ratings and well documented correlations with installation torque,
which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions couple
together to extend the helix bearing plates to the required load bearing stratum. Solid square shaft helical piles and
anchors provide greater penetration into bearing soils and increased axial capacity in firm soils compared to pipe shaft
helical piles with similar torque strength. Strength calculations are based on a design corrosion level of 50 years for most
soil conditions. CHANCE Type SS Helical Piles and Anchors have a longer service life than do pipe shaft piles because of
their reduced surface area. CHANCE Type SS Helical Piles and Anchors feature sharpened leading edge helix plates that are
circular in plan to provide uniform load bearing in most soil conditions. Helix plates can be equipped with “sea-shell” cuts

DRAWINGS AND RATINGS

on the leading edge to enhance penetration through dense soils with occasional cobbles and debris. Custom lengths and
helix configurations are available upon request. See below for additional information and other sections of this Technical
Manual for specifications and design details.

True
Helix
Form

Hole accepts
2-1/4” 3 Dia. 1-1/4” Dia.
Square Spacing Coupling Bolt
Shaft Typical
Up to
7’ - 0
Long

3” Pitch Sharp 1-1/4” Dia.

Leading Edge Structural
Grade Bolt

5-1/2”
2-7/8”
45˚ Pilot Point

Triple Helix Quad Helix Helical Extension Plain Exension Coupling

Lead Section Lead Section Section Section Detail

Page 6-23 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS225 Helical Pile and Anchor Specifications &
Available Configurations
Shaft – Round-Cornered-Square (RCS) 2-1/4 inch solid steel shaft produced
exclusively for CHANCE products.
Coupling - forged as a deep socket from the steel shaft material as an integral
part of the extension, connected with structural bolts.
Helix - ½ inch Thick: ASTM A656, or A1018 with minimum yield strength of 80
ksi.
3 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for
Helical Piles and Anchors.
Available Helix Diameters: 6, 8, 10, 12, and 14 inch.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The standard helix plate has straight sharpened leading edges or can be ordered
with a “sea shell” cut. The “sea shell” cut is best suited when it is necessary to
penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Triple, and quad helix Lead Sections, 5, 7 and 10 feet long
Plain Extensions, 5 and 7 feet long
CHANCE Type SS225
DRAWINGS AND RATINGS

Extensions with Helix Plates, 5, and 7 feet long, single and multi-helix Helical Pile Shaft Cross-Section
Helical products are Hot Dip Galvanized per ASTM A153 Class B-1. Figure 6-13
NOTE: Helical piles shall be installed to appropriate depth in suitable bearing
stratum as determined by the geotechnical engineer or local jurisdictional authority. Torque correlated capacities are based on installing
the pile to its torque rating, using consistent rate of advance and RPM. A minimum factor of safety of 2 is recommended for determining
allowable capacity from correlations. Axial deflections of 0.25 to 0.50 inches are typical at allowable capacity.

Nominal, LRFD Design and ASD Allowable Strengths of SS225 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
6 (150) 0.5 (13) 188 (836.3) 141 (627.2) 94 (418.1)
8 (200) 0.5 (13) 188 (836.3) 141 (627.2) 94 (418.1)
10 (250) 0.5 (13) 151.8 (675.2) 113.9 (506.4) 75.9 (337.6)
12 (300) 0.5 (13) 141.3 (628.5) 106 (471.4) 70.6 (314)
14 (350) 0.5 (13) 126.3 (561.8) 94.7 (421.4) 63.2 (281.1)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type SS225 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths, kip (kN)
Section Type & Helix Firm Soil Soft Soil
Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
139.0 (618.3) 125.1 (556.5)
See Helix Strength 70.9 63.8
Lead, Single Helix See Helix Strength Table
Table Single 14 inch Single 14 inch – (315.4) (283.8)
– 126.3 (561.8) 113.7 (505.8)

Lead, 2-Helix 8”-10” 331.6 (1475) 298.4 (1327.3)

Lead, 2-Helix 10”-12” 293.1 (1303.8) 263.8 (1173.4)

Lead, 2-Helix 12”-14” 267.6 (1190.3) 240.9 (1071.6) 250.1 225.1 70.9 63.8
139.0 (618.3) 125.1 (556.5)
(1112.5) (1001.3) (315.4) (283.8)
Lead, 2-Helix 14”-14” 252.6 (1123.6) 227.4 (1011.5)

Lead, Multi-Helix 331.6 (1475) 298.4 (1327.3)

Extension 331.6 (1475) 298.4 (1327.3)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-24 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 SS225 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled Round-Cornered-Square (RCS) Solid
SHAFT Steel Bars per ASTM A29; modified AISI 1530
with 90 ksi minimum yield strength
Corroded
Shaft Size 2.25 in 57 mm
2.237 in 56.8 mm
Corroded
Moment of Inertia (I) 2.04 in4 84.9 cm4
1.99 in4 82.83 cm4
Corroded
Shaft Area (A) 5.0 in2 32.1 cm2
4.93 in2 31.81 cm2
Corroded
Section Modulus (Sx-x) 1.81 in3 29.7 cm3
1.79 in3 29.37 cm3
Corroded
Perimeter 8.5 in 21.5 cm
8.43 in 21.41 cm
Coupling Integral Forged Square Deep Socket
One 1-1/4 inch Diameter ASTM A193 Grade
Coupling Bolts B7 Hex Head Bolt with Threads Excluded from

DRAWINGS AND RATINGS

Shear Planes
0.5 inch Thick, Formed on Matching Metal
Helix Plates
Dies, ASTM A656 or A1018 Grade 80
Hot Dip Galvanized per ASTM A153 Class B-1,
Coatings
3.1 mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
10 ft-1 33 m-1
Factor
Torque Rating 21,000 ft-lb 28,475 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
200 kip 890 kN 150 kip 667 kN
Allowable Tension
100 kip 445 kN
Strength Assembly of SS225
TORQUE CORRELATED CAPACITY Figure 6-14
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 210 kip 934 kN 105 kip 467 kN

ASD Allowable Compression Strengths of CHANCE® Type SS225 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kip (kN)
Section Type & Helix Count Firm Soil Soft Soil
Fixed Pinned Fixed Pinned
See Helix
Strength Table
Lead, Single Helix See Helix Strength Table Above See Helix Strength Table Above Above, except 42.5 (189)
single 6 & 8 inch
- 83.2 (370.1)
Lead, 2-Helix 8”-10” 169.9 (755.8) 149.8 (666.3)
Lead, 2-Helix 10”-12” 146.5 (651.6) 146.5 (650.7)
83.2 (370.1) 42.5 (189)
Lead, 2-Helix 12”-14” 133.8 (595.1) 133.8 (595.1)
Lead, 2-Helix 14”-14” 126.4 (562.2) 126.4 (562.3)
Lead, Multi-Helix 198.6 (883.4) 149.8 (666.3) 83.2 (370.1) 42.5 (189)
Extension 198.6 (883.4) 149.8 (666.3) 83.2 (370.1) 42.5 (189)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-25 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE RS2875.203 HELICAL PILES
63 kip Ultimate – 31.5 kip Allowable Capacity

RS2875.203
Installation Torque Rating – 7,000 ft-lb
Multi-Purpose 2-7/8” Diameter, 0.203” Wall, Round HSS Shaft with integrally formed upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type RS2875.203 Helical Piles have 63 kip ultimate capacity and 31.5 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for
DRAWINGS AND RATINGS

additional information and other sections of this Technical Manual for specifications and design details.

Hole accepts
2-7/8” Dia. 3/4” Dia.
Pipe Shaft Coupling Bolt

3“
Spacing
Up to
10’ - 0
True 3 Dia.
Long
Helix Spacing
Form Typical

3/4” Dia.
3” Pitch Structural
Sharp Grade Bolt
Leading
Edge
6-1/4”

45 Pilot Point
1-1/2”

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-26 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
RS2875.203 Helical Pile Specifications & Available Configurations
Shaft – HSS 2-7/8 inch OD x 0.203 inch (schedule 40) wall steel shaft produced
exclusively for CHANCE products.
Coupling – forged as an integral part of the plain and helical extension material as
round deep sockets connected with multiple structural bolts.
Helix – 3/8 inch Thick: ASTM A572, or A1018, or A656 with minimum yield strength
of 50 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for Helical
Piles and Anchors.
Available Helix Diameters: 8, 10, 12, or 14 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix unless
otherwise specified.
The standard helix plate has straight sharpened leading edges or can be ordered
with a “sea shell” cut. The “sea shell” cut is best suited when it is necessary to
penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, and triple helix Lead Sections, 5, 7, and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 5 and 7 feet long
Helical products are Hot Dip Galvanized per ASTM A153 Class B-1.

DRAWINGS AND RATINGS

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing
stratum as determined by the geotechnical engineer or local jurisdictional authority.
Torque correlated capacities are based on installing the pile to its torque rating,
using consistent rate of advance and RPM. A minimum factor of safety of 2 is
recommended for determining allowable capacity from correlations. Deflections of
0.25 to 0.50 inches are typical at allowable capacity. CHANCE Type RS2875.203
Helical Pile Shaft Cross-Section
Nominal, LRFD Design and ASD Allowable Strengths of RS2875.203 Helix Figure 6-15
Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.375 (9.5) 85.8 (381.7) 64.4 (286.3) 42.9 (190.8)
10 (250) 0.375 (9.5) 73.6 (327.4) 55.2 (245.6) 36.8 (163.7)
12 (300) 0.375 (9.5) 75.6 (336.3) 56.7 (252.2) 37.8 (168.1)
14 (350) 0.375 (9.5) 61.0 (271.3) 45.8 (203.5) 30.5 (135.7)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS2875.203 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Firm Soil Soft Soil
Helix Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design

69.0 (306.9) 62.1 (276.2) 64.3 (286.0) 57.9 (257.6)

Lead, Single Helix For Single For Single For Single For Single 55.5 (246.9) 49.9 (222.0) 42.0 (186.8) 37.8 (168.1)
14”– 61 14”– 54.9 14”– 61.0 14”– 57.9
(271.3) (244.2) (271.3) (257.6)
Lead, Multi-Helix 69.0 (306.9) 62.1 (276.2) 64.3 (286.0) 57.9 (257.6)
55.5 (246.9) 49.9 (222.0) 42.0 (186.8) 37.8 (168.1)
Extension 69.0 (306.9) 62.1 (276.2) 64.3 (286.0) 57.9 (257.6)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-27 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS2875.203 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 2-1/2 inch Nominal Schedule 40
SHAFT (0.203 inch nominal wall) per ASTM A500 Grade
B/C with 65 ksi minimum yield strength
Corroded
Shaft Size, OD 2.875 in 73 mm
2.862 in 72.7 mm
Corroded
Shaft Size, ID* 2.497 in 63.4 mm
2.510 in 63.75 mm
Corroded
Moment of Inertia (I)* 1.44 in4 59.9 cm4
1.344 in4 55.9 cm4
Corroded
Shaft Area (A)* 1.59 in2 10.3 cm2
1.48 in2 9.57 cm2
Corroded
Section Modulus (Sx-x)* 1.0 in3 16.4 cm3
0.939 in3 15.4 cm3
Corroded
Perimeter 9.0 in 22.8 cm
8.99 in 22.8 cm
DRAWINGS AND RATINGS

Coupling Integral Forged Round Deep Socket Sleeve

Two ¾ in Diameter SAE J429 Grade 5 Hex Head
Coupling Bolts
Bolts with Threads Excluded from Shear Planes
0.375 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A572 Grade 50 or better
Hot Dip Galvanized per ASTM A153 Class B-1, 3.1
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
9 ft-1 30 m-1
Factor
Torque Rating 7,000 ft-lb 9,491 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
60 kip 267 kN 45 kip 200 kN
Allowable Tension
30 kip 133 kN
Strength
Assembly of RS2875.203
TORQUE CORRELATED CAPACITY Figure 6-16
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 63 kip 280 kN 31.5 kip 140 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

ASD Allowable Compression Strengths of CHANCE® Type RS2875.203 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
For Single 8” – 41.3 (183.7) For Single 8” – 38.5 (171.3) 33.2 (147.7)
Lead, Single Helix See Helix Strength Table See Helix Strength Table 25.1 (111.7)
For Single 14” – 30.5 (135.7)
Above for 10”, 12” & 14” Above for 10”, 12” & 14”
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-12”
41.3 (183.7) 38.5 (171.3) 33.2 (147.7) 25.1 (111.7)
Lead, 2-Helix 12”-14”
Lead, 2-Helix 14”-14”
Lead, Multi-Helix 41.3 (183.7) 38.5 (171.3) 33.2 (147.7) 25.1 (111.7)
Extension 41.3 (183.7) 38.5 (171.3) 33.2 (147.7) 25.1 (111.7)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-28 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE RS2875.203 HELICAL PILES PER ICC-ES AC 358 FOR BUILDING
CODE EVALUATION
60.4 kip Ultimate – 30.2 kip Allowable Capacity

RS2875.203
Installation Torque Rating – 6,710 ft-lb
Multi-Purpose 2-7/8” Diameter, 0.203” Wall, Round HSS Shaft with sleeve couplings

Description:
Hubbell Power Systems, Inc., CHANCE Type RS2875.203 Helical Piles have 60.4 kip ultimate capacity and 30.2 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense

DRAWINGS AND RATINGS

soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for
additional information and other sections of this Technical Manual for specifications and design details.

Hole accepts
2-7/8” Dia. 3/4” Dia.
Pipe Shaft Coupling Bolt

3“
Spacing
Up to
10’ - 0
True 3 Dia.
Long
Helix Spacing
Form Typical

3/4” Dia.
3” Pitch Structural
Sharp Grade Bolt
Leading
Edge
6-1/4”

45 Pilot Point
1-1/2”

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-29 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS2875.203 Building Code Helical Pile Specifications & Available Configurations
Shaft – HSS 2-7/8 inch OD x 0.203 inch (schedule 40) wall steel shaft produced
exclusively for CHANCE products.
Coupling – welded sleeve forming a socket connected with multiple structural bolts.
Helix – 3/8 inch Thick: ASTM A572, or A1018, or A656 with minimum yield strength
of 50 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for Helical
Piles and Anchors.
Available Helix Diameters: 8, 10, 12, or 14 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix unless
otherwise specified.
The standard helix plate has straight sharpened leading edges or can be ordered
with a “sea shell” cut. The “sea shell” cut is best suited when it is necessary to
penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, and triple helix Lead Sections, 5, 7, and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 5 and 7 feet long
Helical products are Hot Dip Galvanized per ASTM A153 Class B-1.
DRAWINGS AND RATINGS

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing

stratum as determined by the geotechnical engineer or local jurisdictional authority.
Torque correlated capacities are based on installing the pile to its torque rating,
using consistent rate of advance and RPM. A minimum factor of safety of 2 is
recommended for determining allowable capacity from correlations. Deflections of
0.25 to 0.50 inches are typical at allowable capacity.
CHANCE Type RS2875.203
Helical Pile Shaft Cross-Section
Figure 6-17
Nominal, LRFD Design and ASD Allowable Strengths of RS2875.203 Helix
Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.375 (9.5) 135.0 (600.5) 101.3 (450.6) 67.5 (300.3)
10 (250) 0.375 (9.5) 122.7 (545.8) 92.0 (409.2) 61.4 (273.1)
12 (300) 0.375 (9.5) 127.1 (565.4) 95.3 (423.9) 63.6 (282.9)
14 (350) 0.375 (9.5) 124.9 (555.6) 93.7 (416.8) 62.4 (277.6)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS2875.203 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Firm Soil Soft Soil
Helix Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design

Lead, Single Helix

Lead, Multi-Helix 87.1 (387.4) 65.3 (290.5) 80.1 (356.3) 65.3 (290.5) 66.1 (294.0) 59.5 (264.7) 45.2 (201.1) 41.4 (184.2)

Extension

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-30 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS2875.203 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 2-1/2 inch Nominal Schedule 40
SHAFT (0.203 inch nominal wall) per ASTM A500 Grade
B/C with 65 ksi minimum yield strength
Corroded
Shaft Size, OD 2.875 in 73 mm
2.862 in 72.7 mm
Corroded
Shaft Size, ID* 2.497 in 63.4 mm
2.510 in 63.75 mm
Corroded
Moment of Inertia (I)* 1.44 in4 59.9 cm4
1.344 in4 55.9 cm4
Corroded
Shaft Area (A)* 1.59 in2 10.3 cm2
1.48 in2 9.57 cm2
Corroded
Section Modulus (Sx-x)* 1.0 in3 16.4 cm3
0.939 in3 15.4 cm3
Corroded
Perimeter 9.0 in 22.8 cm
8.99 in 22.8 cm
Welded Sleeve

DRAWINGS AND RATINGS

Coupling Welded Round Deep Socket Sleeve
Two ¾ in Diameter SAE J429 Grade 5 Hex Head
Coupling Bolts
Bolts with Threads Excluded from Shear Planes
0.375 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A572 Grade 50 or better
Hot Dip Galvanized per ASTM A153 Class B-1, 3.1
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
9 ft-1 30 m-1
Factor
Torque Rating 6,710 ft-lb 9,100 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
87 kip 387 kN 65.3 kip 290.5 kN
Allowable Tension
43.5 kip 193.5 kN
Strength Assembly of RS2875.203
TORQUE CORRELATED CAPACITY Figure 6-18
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 60.4 kip 269 kN 30.2 kip 134 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

ASD Allowable Compression Strengths of CHANCE® Type RS2875.203 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
Lead, Single Helix 43.5 (193.5) 43.5 (193.5) 39.6 (176.1) 27.5 (122.3)
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-12”
43.5 (193.5) 43.5 (193.5) 39.6 (176.1) 27.5 (122.3)
Lead, 2-Helix 12”-14”
Lead, 2-Helix 14”-14”
Lead, Multi-Helix 43.5 (193.5) 43.5 (193.5) 39.6 (176.1) 27.5 (122.3)
Extension 43.5 (193.5) 43.5 (193.5) 39.6 (176.1) 27.5 (122.3)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-31 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE RS2875.276 HELICAL PILES
72 kip Ultimate – 36 kip Allowable Capacity
Installation Torque Rating – 8,000 ft-lb

RS2875.276
Multi-Purpose 2-7/8” Diameter, 0.276” Wall, Round HSS Shaft with integrally formed upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type RS2875.276 Helical Piles have 72 kip ultimate capacity and 36 kip working or
allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for
DRAWINGS AND RATINGS

additional information and other sections of this Technical Manual for specifications and design details.

Hole accepts
2-7/8” Dia. 3/4” Dia.
Pipe Shaft Coupling Bolt

3“
Spacing
Up to
10’ - 0
True 3 Dia.
Long
Helix Spacing
Form Typical

3/4” Dia.
3” Pitch Structural
Sharp Grade Bolt
Leading
Edge
6-1/4”

45˚ Pilot Point

1-1/2”

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-32 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
RS2875.276 Helical Pile Specifications & Available Configurations
Shaft – HSS 2-7/8 inch OD x 0.276 inch (schedule 80) wall steel shaft produced
exclusively for CHANCE products.
Coupling – forged as an integral part of the plain and helical extension material as
round deep sockets connected with multiple structural bolts.
Helix – 3/8 inch Thick: ASTM A656, or A1018 with minimum yield strength of 80 ksi.
3 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for
CHANCE Helical Piles and Anchors.
Available Helix Diameters: 8, 10, 12, or 14 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix unless
otherwise specified.
The standard helix plate has straight sharpened leading edges or can be ordered
with a “sea shell” cut. The “sea shell” cut is best suited when it is necessary to
penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, and triple and quad helix Lead Sections, 3.5, 5, 7, and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 3 feet long
Helical products are Hot Dip Galvanized per ASTM A153 Class B-1.

DRAWINGS AND RATINGS

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing
stratum as determined by the geotechnical engineer or local jurisdictional authority.
Torque correlated capacities are based on installing the pile to its torque rating,
using consistent rate of advance and RPM. A minimum factor of safety of 2 is
recommended for determining allowable capacity from correlations. Deflections of
0.25 to 0.50 inches are typical at allowable capacity. CHANCE Type RS2875.276 Helical Pile Shaft Cross-Section
Figure 6-19
Nominal, LRFD Design and ASD Allowable Strengths of RS2875.276 Helix
Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.375 (9.5) 121.4 (540.0) 91.1 (378) 60.7 (270.0)
10 (250) 0.375 (9.5) 98.9 (439.9) 74.2 (330) 49.5 (220.2)
12 (300) 0.375 (9.5) 85.3 (379.4) 63.9 (284.6) 42.7 (189.9)
14 (350) 0.375 (9.5) 53.7 (238.9) 40.3 (179.2) 26.9 (119.7)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS2875.276 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Helix Firm Soil Soft Soil
Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
92.9 83.6 86.3 77.7 73.9 66.5 55.2 49.7
Lead, Single Helix (413.2) (371.9) (383.9) (345.6) (328.7) (295.8) (245.5) (221.1)
See Helix Table Above For Single 12” & 14” See Helix Table Above For Single 14”
92.9 83.6 86.3 77.7
Lead, Multi-Helix
(413.2) (371.9) (383.9) (345.6) 73.9 66.5 55.2 49.7
92.9 83.6 86.3 77.7 (328.7) (295.8) (245.5) (221.1)
Extension
(413.2) (371.9) (383.9) (345.6)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-33 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS2875.276 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 2-1/2 inch Nominal Schedule 80
SHAFT (0.276 inch nominal wall) per ASTM A500 Grade
B/C with 50 ksi minimum yield strength
Corroded
Shaft Size, OD 2.875 in 73 mm
2.862 in 72.7 mm
Corroded
Shaft Size, ID* 2.36 in 60 mm
2.375 in 60.3 mm
Corroded
Moment of Inertia (I)* 1.83 in4 76.2 cm4
1.733 in4 72.1 cm4
Corroded
Shaft Area (A)* 2.11 in2 13.6 cm2
2.0 in2 12.9 cm2
Corroded
Section Modulus (Sx-x)* 1.27 in3 20.8 cm3
1.21 in3 19.8 cm3
Corroded
Perimeter 9.0 in 22.8 cm
8.99 in 22.8 cm
DRAWINGS AND RATINGS

Coupling Integral Forged Round Deep Socket Sleeve

Two ¾ in Diameter SAE J429 Grade 5 Hex Head
Coupling Bolts
Bolts with Threads Excluded from Shear Planes
0.375 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A656 Grade 80 or better
Hot Dip Galvanized per ASTM A153 Class B-1, 3.1
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
9 ft-1 30 m-1
Factor
Torque Rating 8,000 ft-lb 10,846 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
90 kip 400 kN 67.5 kip 300 kN
Allowable Tension
45 kip 200 kN
Strength
TORQUE CORRELATED CAPACITY
Capacity Limit Based Ultimate Allowable Assembly of RS2875.276
on Torque Correlation, Figure 6-20
Tension / Compression 72 kip 320 kN 36 kip 160 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

ASD Allowable Compression Strengths of CHANCE® Type RS2875.276 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
For Single 8” – 55.6 For Single 8” – 51.7
44.3 (197.1) 33.0 (146.8)
(247.3) (230.0)
Lead, Single Helix
See Helix Strength Table See Helix Strength Table See Helix Strength Table
For Single 14” – 26.9
Above for 10”, 12” & 14” Above for 10”, 12” & 14” Above for 12” & 14”
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-12”
55.6 (247.3) 51.7 (230.0) 44.3 (197.1) 33.0 (146.8)
Lead, 2-Helix 12”-14”
Lead, 2-Helix 14”-14”
Lead, Multi-Helix 55.6 (247.3) 51.7 (230.0) 44.3 (197.1) 33.0 (146.8)
Extension 55.6 (247.3) 51.7 (230.0) 44.3 (197.1) 33.0 (146.8)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-34 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE RS2875.276 HELICAL PILES PER ICC-ES AC358 FOR BUILDING CODE
EVALUATION
80.1 kip Ultimate – 40.05 kip Allowable Capacity
Installation Torque Rating – 8,900 ft-lb

RS2875.276
Multi-Purpose 2-7/8” Diameter, 0.276” Wall, Round HSS Shaft with Sleeve Couplings

Description:
Hubbell Power Systems, Inc., CHANCE Type RS2875.276 Helical Piles have 80.1 kip ultimate capacity and 40.05 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense

DRAWINGS AND RATINGS

soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for
additional information and other sections of this Technical Manual for specifications and design details.

Hole accepts
2-7/8” Dia. 3/4” Dia.
Pipe Shaft Coupling Bolt

3“
Spacing
Up to
10’ - 0
True 3 Dia.
Long
Helix Spacing
Form Typical

3/4” Dia.
3” Pitch Structural
Sharp Grade Bolt
Leading
Edge
6-1/4”

45˚ Pilot Point

1-1/2”
Welded Sleeve

Single Helix Twin Helix Triple Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-35 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS2875.276 Building Code Helical Pile Specifications & Available Configurations
Shaft – HSS 2-7/8 inch OD x 0.276 inch (schedule 80) wall steel shaft produced
exclusively for CHANCE products.
Coupling – Welded sleeve forming a socket connected with multiple structural
bolts.
Helix – 3/8 inch Thick: ASTM A656, or A1018 with minimum yield strength of 80
ksi.
3 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for
CHANCE Helical Piles and Anchors.
Available Helix Diameters: 8, 10, 12, or 14 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The standard helix plate has straight sharpened leading edges or can be ordered
with a “sea shell” cut. The “sea shell” cut is best suited when it is necessary to
penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, and triple and quad helix Lead Sections, 3.5, 5, 7, and 10 feet
long
Plain Extensions, 3, 5, 7, and 10 feet long
DRAWINGS AND RATINGS

Extensions with Helix Plates, 3 feet long

Helical products are Hot Dip Galvanized per ASTM A153 Class B-1.

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing

stratum as determined by the geotechnical engineer or local jurisdictional
authority. Torque correlated capacities are based on installing the pile to its
torque rating, using consistent rate of advance and RPM. A minimum factor CHANCE Type RS2875.276 Helical Pile Shaft Cross-Section
of safety of 2 is recommended for determining allowable capacity from Figure 6-21
correlations. Deflections of 0.25 to 0.50 inches are typical at allowable capacity.

Nominal, LRFD Design and ASD Allowable Strengths of RS2875.276 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.375 (9.5) 113.9 (504.4) 85.4 (378.3) 56.9 (253.1)
10 (250) 0.375 (9.5) 94.5 (420.4) 70.9 (315.3) 47.3 (210.4)
12 (300) 0.375 (9.5) 93.0 (413.7) 69.8 (310.3) 46.5 (206.8)
14 (350) 0.375 (9.5) 100.3 (446.2) 75.2 (334.7) 50.2 (223.3)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS2875.276 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Helix Firm Soil Soft Soil
Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
92.9 83.6 86.3 77.7 73.9 66.5 55.2 49.7
Lead, Single Helix
(413.2) (371.9) (383.9) (345.6) (328.7) (295.8) (245.5) (221.1)
92.9 83.6 86.3 77.7
Lead, Multi-Helix
(413.2) (371.9) (383.9) (345.6) 73.9 66.5 55.2 49.7
92.9 83.6 86.3 77.7 (328.7) (295.8) (245.5) (221.1)
Extension
(413.2) (371.9) (383.9) (345.6)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-36 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS2875.276 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 2-1/2 inch Nominal Schedule 80
SHAFT (0.276 inch nominal wall) per ASTM A500 Grade
B/C with 50 ksi minimum yield strength
Corroded
Shaft Size, OD 2.875 in 73 mm
2.862 in 72.7 mm
Corroded
Shaft Size, ID* 2.36 in 60 mm
2.375 in 60.3 mm
Corroded
Moment of Inertia (I)* 1.83 in4 76.2 cm4
1.733 in4 72.1 cm4
Corroded
Shaft Area (A)* 2.11 in2 13.6 cm2
2.0 in2 12.9 cm2
Corroded
Section Modulus (Sx-x)* 1.27 in3 20.8 cm3
1.21 in3 19.8 cm3
Corroded Welded Sleeve
Perimeter 9.0 in 22.8 cm
8.99 in 22.8 cm

DRAWINGS AND RATINGS

Coupling Welded Round Deep Socket Sleeve
Two ¾ in Diameter SAE J429 Grade 5 Hex Head
Coupling Bolts
Bolts with Threads Excluded from Shear Planes
0.375 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A656 Grade 80 or better
Hot Dip Galvanized per ASTM A153 Class B-1, 3.1
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
9 ft-1 30 m-1
Factor
Torque Rating 8,900 ft-lb 12,067 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
97.9 kip 453.3 kN 73.4 kip 326.5 kN
Allowable Tension
48.9 kip 217.5 kN
Strength
Assembly of RS2875.276
TORQUE CORRELATED CAPACITY
Figure 6-22
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 80.1 kip 356.3 kN 40.05 kip 178.2 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

ASD Allowable Compression Strengths of CHANCE® Type RS2875.276 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
For Single 8” – 55.6 For Single 8” – 51.7
44.3 (197.1) 33.0 (146.8)
(247.3) (230.0)
Lead, Single Helix
See Helix Strength Table See Helix Strength Table See Helix Strength Table
For Single 14” – 26.9
Above for 10”, 12” & 14” Above for 10”, 12” & 14” Above for 12” & 14”
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-12”
55.6 (247.3) 51.7 (230.0) 44.3 (197.1) 33.0 (146.8)
Lead, 2-Helix 12”-14”
Lead, 2-Helix 14”-14”
Lead, Multi-Helix 55.6 (247.3) 51.7 (230.0) 44.3 (197.1) 33.0 (146.8)
Extension 55.6 (247.3) 51.7 (230.0) 44.3 (197.1) 33.0 (146.8)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC Section

1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-37 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE RS3500.300 HELICAL PILES
91 kip Ultimate – 45.5 kip Allowable Capacity
Installation Torque Rating – 13,000 ft-lb

RS3500.300
Multi-Purpose 3-1/2” Diameter, 0.300” Wall, Round HSS Shaft with integrally formed upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type RS3500.300 Helical Piles have 91 kip ultimate capacity and 45.5 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for
DRAWINGS AND RATINGS

additional information and other sections of this Technical Manual for specifications and design details.

3-1/2” Dia. True

Pipe Shaft Helix
Form 1-1/2 “
Spacing

Hole accepts
3/4” Dia.
Coupling Bolt Up to
10’ - 0
Long

3 Dia.
Spacing
Typical

3/4” Dia.
Structural
3” Pitch Grade Bolt
Sharp
Leading
Edge
6-1/4”
45˚ Pilot Point

1-1/2”

Twin Helix Triple Helix Quad Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-38 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
RS3500.300 Helical Pile Specifications & Available Configurations
Shaft – HSS 3-1/2 inch OD x 0.300 inch (schedule 80) wall steel shaft produced
exclusively for CHANCE products.
Coupling - forged as an integral part of the plain and helical extension
material as round deep sockets connected with multiple structural bolts.
Helix – 1/2 inch Thick: ASTM A572, or A1018, or A656 with minimum yield
strength of 50 ksi.
3 inch Helix Pitch – a Standard established by Hubbell Power Systems, Inc. for
CHANCE Helical Piles and Anchors.
Available Helix Diameters: 8, 10, 12, 14 or 16 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The standard helix plate has straight sharpened leading edges or can be
ordered with a “sea shell” cut. The “sea shell” cut is best suited when it is
necessary to penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, and quad helix Lead Sections, 3, 5, 7, and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 3-1/2 7 and 10 feet long

DRAWINGS AND RATINGS

Helical products are Hot Dip Galvanized per ASTM A123 Grade 75.

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing

stratum as determined by the geotechnical engineer or local jurisdictional
authority. Torque correlated capacities are based on installing the pile to its
torque rating, using consistent rate of advance and RPM. A minimum factor CHANCE Type RS3500.300 Helical Pile Shaft Cross-Section
of safety of 2 is recommended for determining allowable capacity from Figure 6-23
correlations. Deflections of 0.25 to 0.50 inches are typical at allowable capacity.

Nominal, LRFD Design and ASD Allowable Strengths of RS3500.300 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.5 (13) 158.3 (704.2) 118.7 (528.2) 79.1 (351.9)
10 (250) 0.5 (13) 132.5 (589.3) 99.4 (442) 66.3 (294.9)
12 (300) 0.5 (13) 98.4 (437.7) 73.8 (328.3) 49.2 (187.7)
14 (350) 0.5 (13) 132.3 (588.5) 99.2 (441.4) 66.2 (294.5)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS3500.300 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Helix Firm Soil Soft Soil
Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
128.0 115.2 121.9 109.7 110.0 99.0
(569.4) (512.4) (542.2) (488.0) (489.3) (440.3)
90.7 81.6
Lead, Single Helix For Single For Single For Single For Single For Single For Single (403.5) (363.0)
12” – 98.4 12” – 88.6 12” – 98.4 12” – 88.6 12” – 98.4 12” – 88.6
(437.7) (394.1) (437.7) (394.1) (437.7) (394.1)
128 115.2 121.9 109.7
Lead, Multi-Helix
(569.4) (512.4) (542.2) (488.0) 110.0 99.0 90.7 81.6
128.0 115.2 121.9 109.7 (489.3) (440.4) (403.5) (363.0)
Extension
(569.4) (512.4) (542.2) (488.0)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-39 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS3500.300 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 3 inch Nominal Schedule 80 (0.300
SHAFT inch nominal wall) per ASTM A500 Grade B/C with
50 ksi minimum yield strength
Corroded
Shaft Size, OD 3.5 in 89 mm
3.487 in 63.2 mm
Corroded
Shaft Size, ID* 2.942 in 74.7 mm
2.955 in 75.1 mm
Corroded
Moment of Inertia (I)* 3.69 in4 153.6 cm4
3.514 in4 146.3 cm4
Corroded
Shaft Area (A)* 2.82 in2 18.2 cm2
2.692 in2 17.4 cm2
Corroded
Section Modulus (Sx-x)* 2.11 in3 34.5 cm3
2.016 in3 33.0 cm3
Corroded
Perimeter 11.0 in 27.9 cm
10.95 in 27.8 cm
DRAWINGS AND RATINGS

Coupling Integral Forged Round Deep Socket Sleeve

Three ¾ in Dia. SAE J429 Grade 5 Hex Head Bolts
Coupling Bolts
with Threads Excluded from Shear Planes
0.5 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A572 Grade 50 or better
Hot Dip Galvanized per ASTM A123 Grade 75, 3.0
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
7 ft-1 23 m-1
Factor
Torque Rating 13,000 ft-lb 17,600 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
120 kip 534 kN 90 kip 400 kN
Allowable Tension
60 kip 261 kN
Strength
TORQUE CORRELATED CAPACITY Assembly of RS3500.300
Figure 6-24
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 91 kip 405 kN 45.5 kip 202.5 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

ASD Allowable Compression Strengths of CHANCE® Type RS3500.300 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
For Single 8” – 76.6 (340.7) For Single 8” – 73.0 (324.7) 65.9 (293.1) 54.3 (241.5)
Lead, Single Helix See Helix Strength Table See Helix Strength Table For Single 12” – 49.2 For Single 12” – 49.2
Above for 10”, 12” & 14” Above for 10”, 12” & 14” (218.9) (218.9)
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-12”
76.6 (340.7) 73.0 (324.7) 65.9 (293.1) 54.3 (241.5)
Lead, 2-Helix 12”-14”
Lead, 2-Helix 14”-14”
Lead, Multi-Helix 76.6 (340.7) 73.0 (324.7) 65.9 (293.1) 54.3 (241.5)
Extension 76.6 (340.7) 73.0 (324.7) 65.9 (293.1) 54.3 (241.5)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft
capacity.

Page 6-40 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE RS3500.300 HELICAL PILES PER ICC-ES AC358 FOR BUILDING
CODE EVALUATION
87.5 kip Ultimate – 43.75 kip Allowable Capacity

RS3500.300
Installation Torque Rating – 12,500 ft-lb
Multi-Purpose 3-1/2” Diameter, 0.300” Wall, Round HSS Shaft with Welded Sleeve Coupling

Description:
Hubbell Power Systems, Inc., CHANCE Type RS3500.300 Helical Piles have 87.5 kip ultimate capacity and 43.75 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense

DRAWINGS AND RATINGS

soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for

3-1/2” Dia. True

Pipe Shaft Helix
Form 1-1/2 “
Spacing

Hole accepts
3/4” Dia.
Coupling Bolt Up to
10’ - 0
Long

3 Dia.
Spacing
Typical Welded Sleeve

3/4” Dia.
Structural
3” Pitch Grade Bolt
Sharp
Leading
Edge Welded Sleeve
6-1/4”
45˚ Pilot Point

1-1/2”

Twin Helix Triple Helix Quad Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-41 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS3500.300 Building Code Helical Pile Specifications & Available Configurations
Shaft – HSS 3-1/2 inch OD x 0.300 inch (schedule 80) wall steel shaft produced
exclusively for CHANCE products.
Coupling – Welded sleeve forming a socket connected with multiple structural
bolts.
Helix – 1/2 inch Thick: ASTM A572, or A1018, or A656 with minimum yield
strength of 50 ksi.
3 inch Helix Pitch – a Standard established by Hubbell Power Systems, Inc. for
CHANCE Helical Piles and Anchors.
Available Helix Diameters: 8, 10, 12, or 14 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The standard helix plate has straight sharpened leading edges or can be
ordered with a “sea shell” cut. The “sea shell” cut is best suited when it is
necessary to penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, and quad helix Lead Sections, 3, 5, 7, and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 3-1/2 7 and 10 feet long
DRAWINGS AND RATINGS

Helical products are Hot Dip Galvanized per ASTM A123 Grade 75.

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing

stratum as determined by the geotechnical engineer or local jurisdictional
authority. Torque correlated capacities are based on installing the pile to its
torque rating, using consistent rate of advance and RPM. A minimum factor CHANCE Type RS3500.300 Helical Pile Shaft Cross-Section
of safety of 2 is recommended for determining allowable capacity from Figure 6-25
correlations. Deflections of 0.25 to 0.50 inches are typical at allowable capacity.

Nominal, LRFD Design and ASD Allowable Strengths of RS3500.300 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.5 (13) 141.1 (627.6) 105.8 (470.7) 70.6 (314.0)
10 (250) 0.5 (13) 155.1 (689.9) 116.3 (517.4) 77.6 (345.2)
12 (300) 0.5 (13) 159.6 (709.9) 119.7 (532.4) 79.8 (354.9)
14 (350) 0.5 (13) 139.4 (620.1) 104.6 (465.1) 69.7 (301.1)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS3500.300 Helical Pile Lead & Extension Sections1,2,3
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Helix Firm Soil Soft Soil
Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
100 90 100 90 100 90 90.7 81.6
Lead, Single Helix
(444.8) (400.3) (444.8) (400.3) (444.8) (400.3) (403.5) (363.0)
100 90 100 90 100 90
Lead, Multi-Helix
(444.8) (400.3) (444.8) (400.3) (444.8) (400.3) 90.7 81.6
100 90 100 90 100 90 (403.5) (363.0)
Extension
(444.8) (400.3) (444.8) (400.3) (444.8) (400.3)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with

IBC Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft
capacity.
3 Nominal strengths are limited to 100 kip (444.8 kN) per AC358 Section 3.8.

Page 6-42 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS3500.300 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 3 inch Nominal Schedule 80 (0.300
SHAFT inch nominal wall) per ASTM A500 Grade B/C with
50 ksi minimum yield strength
Corroded
Shaft Size, OD 3.5 in 89 mm
3.487 in 63.2 mm
Corroded
Shaft Size, ID* 2.942 in 74.7 mm
2.955 in 75.1 mm
Corroded
Moment of Inertia (I)* 3.69 in4 153.6 cm4
3.514 in4 146.3 cm4
Corroded
Shaft Area (A)* 2.82 in2 18.2 cm2
2.692 in2 17.4 cm2
Corroded
Section Modulus (Sx-x)* 2.11 in3 34.5 cm3
2.016 in3 33.0 cm3
Corroded
Perimeter 11.0 in 27.9 cm
10.95 in 27.8 cm
Welded Sleeve

DRAWINGS AND RATINGS

Coupling Welded Round Deep Socket
Two ¾ in Dia. SAE J429 Grade 5 Hex Head Bolts
Coupling Bolts
with Threads Excluded from Shear Planes
0.5 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A572 Grade 50 or better
Hot Dip Galvanized per ASTM A123 Grade 75, 3.0
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
7 ft-1 23 m-1
Factor
Torque Rating 12,500 ft-lb 16,947.7 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
100 kip 444.8 kN 86.1 kip 383.0 kN
Allowable Tension
57.4 kip 255.3 kN
Strength
TORQUE CORRELATED CAPACITY Assembly of RS3500.300
Figure 6-26
Capacity Limit Based Ultimate Allowable
on Torque Correlation,
Tension / Compression 87.5 kip 389.2 kN 43.75 kip 194.6 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

ASD Allowable Compression Strengths of CHANCE® Type RS3500.300 Helical Pile Lead & Extension Sections1,2,3
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
Lead, Single Helix 60.0 (266.9) 60.0 (266.9) 60.0 (266.9) 54.3 (241.5)
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-12”
60.0 (266.9) 60.0 (266.9) 60.0 (266.9) 54.3 (241.5)
Lead, 2-Helix 12”-14”
Lead, 2-Helix 14”-14”
Lead, Multi-Helix 60.0 (266.9) 60.0 (266.9) 60.0 (266.9) 54.3 (241.5)
Extension 60.0 (266.9) 60.0 (266.9) 60.0 (266.9) 54.3 (241.5)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with

IBC Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft
capacity.
3 ASD allowable strengths are limited to 60 kip (266.9 kN) per AC358 Section 3.8.

Page 6-43 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE RS4500.237 HELICAL PILES
108 kip Ultimate – 54 kip Allowable Capacity
Installation Torque Rating – 18,000 ft-lb

RS4500.337
Multi-Purpose 4-1/2” Diameter, 0.237” Wall, Round HSS Shaft with integrally formed upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type RS4500.337 Helical Piles have 108 kip ultimate capacity and 54 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for
DRAWINGS AND RATINGS

additional information and other sections of this Technical Manual for specifications and design details.

1-1/2”

True
4-1/2” Dia. Helix Hole accepts
Pipe Shaft Form 1” Dia.
Coupling Bolt 3”

Up to
10’ - 0” 1” Dia.
Long Structural
Grade Bolt

3 Dia.
Spacing
6-1/2”
Typical

3” Pitch
Sharp
Leading
Edge
45 Pilot Point

Single Helix Triple Helix Quad Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-44 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
RS4500.237 Helical Pile Specifications & Available Configurations
Shaft – HSS 4-1/2 inch OD x 0.237 inch (schedule 40) wall steel shaft produced
exclusively for CHANCE products.
Coupling – forged as an integral part of the plain and helical extension
material as round deep sockets connected with multiple structural bolts.
Helix – 1/2 inch Thick: ASTM A572, or A1018, or A656 with minimum yield
strength of 80 ksi.
3 inch Helix Pitch – a Standard established by Hubbell Power Systems, Inc. for
CHANCE Helical Piles and Anchors.
Available Helix Diameters: 8, 10, 12, 14, 16, or 20 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The Standard helix plate has straight sharpened leading edges or can be
ordered with a “sea shell” cut. The “sea shell” cut is best suited when it is
necessary to penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, and quad helix Lead Sections, 7 and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 5, 7 and 10 feet long

DRAWINGS AND RATINGS

Helical products are Hot Dip Galvanized per ASTM A123 Grade 75.

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing

stratum as determined by the geotechnical engineer or local jurisdictional
authority. Torque correlated capacities are based on installing the pile to its
torque rating, using consistent rate of advance and RPM. A minimum factor CHANCE Type RS4500.337 Helical Pile Shaft Cross-Section
of safety of 2 is recommended for determining allowable capacity from
correlations. Deflections of 0.25 to 0.50 inches are typical at allowable capacity.
Figure 6-27

Nominal, LRFD Design and ASD Allowable Strengths of RS4500.237 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.5 (13) 244.5 (1087.6) 183.4 (815.7) 122.3 (499.5)
10 (250) 0.5 (13) 200.3 (891.0) 150.2 (608.3) 100.2 (445.7)
12 (300) 0.5 (13) 168.5 (749.5) 126.4 (562.1) 84.3 (375.0)
14 (350) 0.5 (13) 133.0 (591.6) 99.8 (443.7) 66.5 (295.8)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Page 6-45 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS4500.237 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 4 inch Nominal Schedule 40 (0.237
SHAFT inch nominal wall) per ASTM A500 Grade B/C with
50 ksi minimum yield strength
Corroded
Shaft Size, OD 4.5 in 114 mm
4.487 in 114 mm
Corroded
Shaft Size, ID* 4.059 in 103.4 mm
4.071 in 103.4 mm
Corroded
Moment of Inertia (I)* 6.79 in4 282.6 cm4
6.415 in4 267.9 cm4
Corroded
Shaft Area (A)* 2.96 in2 19.1 cm2
2.786 in2 18.09 cm2
Corroded
Section Modulus (Sx-x)* 3.02 in3 49.6 cm3
2.859 in3 47.0 cm3
Corroded
Perimeter 14.1 in 35.9 cm
DRAWINGS AND RATINGS

14.09 in 35.8 cm
Coupling Integral Forged Round Deep Socket Sleeve
Coupling Bolts Two 1 in Dia. ASTM A193 Grade B7 Hex Head Bolts
0.5 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A572 Grade 80 or better
Hot Dip Galvanized per ASTM A123 Grade 75, 3.0
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
6 ft-1 20 m-1
Factor
Torque Rating 18,000 ft-lb 31,200 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
120 kip 712 kN 90 kip 534 kN
Allowable Tension
60 kip 356 kN
Strength
TORQUE CORRELATED CAPACITY Assembly of RS4500.337
Capacity Limit Based Ultimate Allowable Figure 6-28
on Torque Correlation,
Tension / Compression 108 kip 614 kN 54 kip 307 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

Page 6-46 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE RS4500.337 HELICAL PILES
150 kip Ultimate – 75 kip Allowable Capacity
Installation Torque Rating – 25,000 ft-lb

RS4500.337
Multi-Purpose 4-1/2” Diameter, 0.337” Wall, Round HSS Shaft with integrally formed upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type RS4500.337 Helical Piles have 150 kip ultimate capacity and 75 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for

DRAWINGS AND RATINGS

additional information and other sections of this Technical Manual for specifications and design details.

1-1/2”

True
4-1/2” Dia. Helix Hole accepts
Pipe Shaft Form 1” Dia.
Coupling Bolt 3”

Up to
10’ - 0” 1” Dia.
Long Structural
Grade Bolt

3 Dia.
Spacing
6-1/2”
Typical

3” Pitch
Sharp
Leading
Edge
45 Pilot Point

Single Helix Triple Helix Quad Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-47 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS4500.337 Helical Pile Specifications & Available Configurations
Shaft – HSS 4-1/2 inch OD x 0.337 inch (schedule 80) wall steel shaft produced
exclusively for CHANCE products.
Coupling – forged as an integral part of the plain and helical extension
material as round deep pockets connected with multiple structural bolts.
Helix – 1/2 inch Thick: ASTM A572, or A1018, or A656 with minimum yield
strength of 80 ksi.
3 inch Helix Pitch – a Standard established by Hubbell Power Systems, Inc. for
CHANCE Helical Piles and Anchors.
Available Helix Diameters: 8, 10, 12, 14, 16, or 20 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The Standard helix plate has straight sharpened leading edges or can be
ordered with a “sea shell” cut. The “sea shell” cut is best suited when it is
necessary to penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, and quad helix Lead Sections, 7 and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 5, 7 and 10 feet long
DRAWINGS AND RATINGS

Helical products are Hot Dip Galvanized per ASTM A123 Grade 75.

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing

stratum as determined by the geotechnical engineer or local jurisdictional
authority. Torque correlated capacities are based on installing the pile to
its torque rating, using consistent rate of advance and RPM. A minimum CHANCE Type RS4500.337 Helical Pile Shaft Cross-Section
factor of safety of 2 is recommended for determining allowable capacity
from correlations. Deflections of 0.25 to 0.50 inches are typical at allowable
Figure 6-29
capacity.

Nominal, LRFD Design and ASD Allowable Strengths of RS4500.337 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.5 (13) 244.5 (1087.6) 183.4 (815.7) 122.3 (499.5)
10 (250) 0.5 (13) 200.3 (891.0) 150.2 (668.3) 100.2 (445.7)
12 (300) 0.5 (13) 168.5 (749.5) 126.4 (562.1) 84.3 (375.0)
14 (350) 0.5 (13) 133.0 (591.6) 99.75 (443.7) 66.5 (295.8)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS4500.337 Helical Pile Lead & Extension Sections1,2
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Helix Firm Soil Soft Soil
Count Fixed Pinned Fixed Pinned
Nominal Design Nominal Design Nominal Design Nominal Design
191.7 172.6 186.3 167.7 175.3 157.8 156.3 140.7
(852.7) (767.7) (828.7) (746.0) (779.8) (701.9) (695.3) (625.9)
Lead, Single Helix For Single
For Single
For Nominal, see Helix Strength Table above for Single 12” & 14” 12” & 14”
14” – 133.0
For LRFD design, see Helix Strength Table above for 10”, 12” & 14” see Helix
(591.6)
Table
191.7 172.6 186.3 167.7
Lead, Multi-Helix
(852.7) (767.8) (828.7) (746.0) 175.3 157.8 156.3 140.7
191.7 172.6 186.3 167.7 (779.8) (701.9) (695.3) (625.9)
Extension
(852.7) (767.8) (828.7) (746.0)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-48 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS4500.337 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 4 inch Nominal Schedule 80 (0.337
SHAFT inch nominal wall) per ASTM A500 Grade B/C with
50 ksi minimum yield strength
Corroded
Shaft Size, OD 4.5 in 114 mm
4.487 in 114 mm
Corroded
Shaft Size, ID* 3.874 in 98.4 mm
3.886 in 98.7 mm
Corroded
Moment of Inertia (I)* 9.07 in4 377.5 cm4
8.701 in4 362.2 cm4
Corroded
Shaft Area (A)* 4.12 in2 26.6 cm2
3.951 in2 25.5 cm2
Corroded
Section Modulus (Sx-x)* 4.03 in3 66.1 cm3
3.878 in3 63.6 cm3
Corroded
Perimeter 14.1 in 35.9 cm
14.09 in 35.8 cm

DRAWINGS AND RATINGS

Coupling Integral Forged Round Deep Socket Sleeve
Coupling Bolts Two 1 in Dia. ASTM A193 Grade B7 Hex Head Bolts
0.5 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A572 Grade 80 or better
Hot Dip Galvanized per ASTM A123 Grade 75, 3.0
Coatings
mil minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
6 ft-1 20 m-1
Factor
Torque Rating 25,000 ft-lb 33,900 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
160 kip 712 kN 120 kip 534 kN
Allowable Tension
80 kip 356 kN
Strength
TORQUE CORRELATED CAPACITY
Assembly of RS4500.337
Capacity Limit Based Ultimate Allowable
on Torque Correlation, Figure 6-30
Tension / Compression 150 kip 667 kN 75 kip 334 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

ASD Allowable Compression Strengths of CHANCE® Type RS4500.337 Helical Pile Lead & Extension Sections1,2
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
For Single 8” – 114.8 For Single 8” – 111.6
105.0 (467.1) 93.6 (416.4)
(551.7) (496.4)
Lead, Single Helix See Helix Strength Table See Helix Strength Table See Helix Strength Table See Helix Strength Table
Above for 10”, 12” & 14” Above for 10”, 12” & 14” Above for 10”, 12” & 14” Above for 12” & 14”
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-
12”
Lead, 2-Helix 12”- 114.8 (551.7) 111.6 (496.4) 105.0 (467.1) 93.6 (416.4)
14”
Lead, 2-Helix 14”-
14”
Lead, Multi-Helix 114.8 (551.7) 111.6 (496.4) 105.0 (467.1) 93.6 (416.4)
Extension 114.8 (551.7) 111.6 (496.4) 105.0 (467.1) 93.6 (416.4)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.

Page 6-49 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 CHANCE® TYPE RS4500.337 HELICAL PILES PER ICC-ES AC358 FOR BUILDING
CODE EVALUATION
136.1 kip Ultimate – 68.1 kip Allowable Capacity

RS4500.337
Installation Torque Rating – 24,300 ft-lb
Multi-Purpose 4-1/2” Diameter, 0.337” Wall, Round HSS Shaft with integrally formed upset sockets

Description:
Hubbell Power Systems, Inc., CHANCE Type RS4500.337 Helical Piles have 136.1 kip ultimate capacity and 68.1 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
DRAWINGS AND RATINGS

soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for

1-1/2”

True
4-1/2” Dia. Helix Hole accepts
Pipe Shaft Form 1” Dia.
Coupling Bolt 3”

Up to
10’ - 0” 1” Dia.
Long Structural
Grade Bolt

3 Dia.
Spacing
6-1/2”
Typical

3” Pitch
Sharp
Leading
Edge
45 Pilot Point

Single Helix Triple Helix Quad Helix Helical Extension Plain Exension Coupling
Lead Section Lead Section Lead Section Section Section Detail

Page 6-50 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
RS4500.337 Building Code Helical Pile Specifications & Available Configurations
Shaft – HSS 4-1/2 inch OD x 0.337 inch (schedule 80) wall steel shaft produced
exclusively for CHANCE products.
Coupling – forged as an integral part of the plain and helical extension
material as round deep sockets connected with multiple structural bolts.
Helix – 1/2 inch Thick: ASTM A572, or A1018, or A656 with minimum yield
strength of 80 ksi.
3 inch Helix Pitch – a Standard established by Hubbell Power Systems, Inc. for
CHANCE Helical Piles and Anchors.
Available Helix Diameters: 8, 10, 12, 14, 16, or 20 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix
unless otherwise specified.
The Standard helix plate has straight sharpened leading edges or can be
ordered with a “sea shell” cut. The “sea shell” cut is best suited when it is
necessary to penetrate soils with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, and quad helix Lead Sections, 7 and 10 feet long
Plain Extensions, 3, 5, 7, and 10 feet long
Extensions with Helix Plates, 5, 7 and 10 feet long

DRAWINGS AND RATINGS

Helical products are Hot Dip Galvanized per ASTM A123 Grade 75.

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing

stratum as determined by the geotechnical engineer or local jurisdictional
authority. Torque correlated capacities are based on installing the pile to
its torque rating, using consistent rate of advance and RPM. A minimum CHANCE Type RS4500.337 Helical Pile Shaft Cross-Section
factor of safety of 2 is recommended for determining allowable capacity
from correlations. Deflections of 0.25 to 0.50 inches are typical at allowable
Figure 6-31
capacity.

Nominal, LRFD Design and ASD Allowable Strengths of RS4500.337 Helix Plates for Shaft Axial Tension and Compression1
Helix Diameter Nominal Strength LRFD Design Strength ASD Allowable Strength
Thickness in (mm)
in (mm) kip (kN) kip (kN) kip (kN)
8 (200) 0.5 (13) 180.2 (801.6) 135.2 (601.4) 90.2 (401.2)
10 (250) 0.5 (13) 180.2 (801.6) 135.2 (601.4) 90.2 (401.2)
12 (300) 0.5 (13) 180.2 (801.6) 135.2 (601.4) 90.2 (401.2)
14 (350) 0.5 (13) 180.2 (801.6) 135.2 (601.4) 90.2 (401.2)
For SI: 1 kip = 4.448 kN.
1Capacities based on a design corrosion level of 50-years.

Nominal and LRFD Design Compression Strengths of CHANCE® Type RS4500.337 Helical Pile Lead & Extension Sections1,2,3
Nominal & LRFD Design Compression Strengths kips (kN)
Section Type & Helix Firm Soil Soft Soil
Count Fixed Pinned Fixed Pinned
Nominal Design3 Nominal Design3 Nominal Design3 Nominal Design
175.3 156.3
(779.8) (695.3)
Lead, Single Helix
See Helix Strength Table Above

Lead, Multi-Helix
191.7 145.33 186.3 145.33 175.3 145.33 156.3 140.67
(852.7) (646.5) (828.7) (646.57) (779.8) (646.57) (695.3) (625.7)
Extension

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft
capacity.
3 Limited by Coupling Bolt Shear

Page 6-51 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS4500.337 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS
Hot Rolled HSS 4 inch Nominal Schedule 80 (0.337 inch
SHAFT nominal wall) per ASTM A500 Grade B/C with 50 ksi
minimum yield strength
Corroded
Shaft Size, OD 4.5 in 114 mm
4.487 in 114 mm
Corroded
Shaft Size, ID* 3.874 in 98.4 mm
3.886 in 98.7 mm
Corroded
Moment of Inertia (I)* 9.07 in4 377.5 cm4
8.701 in4 362.2 cm4
Corroded
Shaft Area (A)* 4.12 in2 26.6 cm2
3.951 in2 25.5 cm2
Corroded
Section Modulus (Sx-x)* 4.03 in3 66.1 cm3
3.878 in3 63.6 cm3
Corroded
Perimeter 14.1 in 35.9 cm
14.09 in 35.8 cm
DRAWINGS AND RATINGS

Coupling Integral Forged Round Deep Socket Sleeve

Coupling Bolts Two 1 in Dia. ASTM A193 Grade B7 Hex Head Bolts
0.5 inch Thick, Formed on Matching Metal Dies, ASTM
Helix Plates
A572 Grade 80 or better
Hot Dip Galvanized per ASTM A123 Grade 75, 3.0 mil
Coatings
minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation
5.6 ft-1 18.5 m-1
Factor†
Torque Rating 24,300 ft-lb 32,946 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
150 kip 667.2 kN 112.5 kip 500.2 kN
Allowable Tension
75 kip 333.6 kN
Strength
TORQUE CORRELATED CAPACITY
Assembly of RS4500.337
Capacity Limit Based Ultimate Allowable Figure 6-32
on Torque Correlation,
Tension / Compression 136.1 kip 605.4 kN 68.1 kip 302.9 kN

* computed with 93% of wall thickness per AISC 360-10, B4.2

† per ICC-ES AC358 Section 3.13.1.1

ASD Allowable Compression Strengths of CHANCE® Type RS4500.337 Helical Pile Lead & Extension Sections1,2,3
ASD Allowable Axial Compression Strength kips (kN)
Section Type & Helix
Firm Soil Soft Soil
Count
Fixed Pinned Fixed Pinned
See Helix Strength Table See Helix Strength Table See Helix Strength Table See Helix Strength Table
Lead, Single Helix Above for 8”, 10”, 12” & Above for 8”,10”, 12” & Above for 8”, 10”, 12” & Above for 8”, 10”, 12” &
14” 14” 14” 14”
Lead, 2-Helix 8”-10”
Lead, 2-Helix 10”-12”
96.9 (431) 96.9 (431) 96.9 (431) 93.6 (416.4)
Lead, 2-Helix 12”-14”
Lead, 2-Helix 14”-14”
Lead, Multi-Helix 96.9 (431) 96.9 (431) 96.9 (431) 93.6 (416.4)
Extension 96.9 (431) 96.9 (431) 96.9 (431) 93.6 (416.4)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil and firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.
3 Limited by Bolt Shear

Page 6-52 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE RS6625.280 HELICAL PILES
200 kip Ultimate – 100 kip Allowable Capacity

RS6625.280
Installation Torque Rating – 40,000 ft-lb
Multi-Purpose 6-5/8” Diameter, 0.280” Wall, Round HSS Shaft with welded square formed couplings

Description:
Hubbell Power Systems, Inc., CHANCE Type RS6625.280 Helical Piles have 200 kip ultimate capacity and 100 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for

DRAWINGS AND RATINGS

additional information and other sections of this Technical Manual for specifications and design details.

Hole
accepts
1” Dia.
Coupling
Stud

Up to
10’ - 0
Long
6-5/8” Dia.
Pipe Shaft

True
Helix
Form
1” Dia.
Coupling
Stud

8”
45˚ Pilot Point

Single Helix Twin Helix Lead Section Plain Exension Coupling

Lead Section w/ Plate Coupling Section Detail

Page 6-53 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS6625.280 Helical Pile Specifications & Available Configurations
Shaft – HSS 6-5/8 inch OD x 0.280 inch (schedule 40) wall steel shaft produced exclusively for
CHANCE products.
Coupling – formed and welded as a deep square socket, connected with multiple threaded
studs & nuts.
Helix – 1/2 inch Thick: ASTM A572, or A1018, or A656 with minimum yield strength of 80 ksi.
3 inch Helix Pitch – a Standard established by Hubbell Power Systems, Inc. for CHANCE
Helical Piles and Anchors.
Available Helix Diameters: 12, 14, and 16 inches.
All helix plates are spaced 3 times the diameter of the preceding (lower) helix unless
otherwise specified.
The Standard helix plate has straight sharpened leading edges or can be ordered with a
“sea shell” cut. The “sea shell” cut is best suited when it is necessary to penetrate soils with
fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, Lead Sections, 7, 10, and 15 feet long
Plain Extensions, 5, 7, and 10 feet long
Extensions with Helix Plates, 5, 7 and 10 feet long
Helical products are Hot Dip Galvanized per ASTM A123 Grade 75.
CHANCE Type RS6625.280
DRAWINGS AND RATINGS

NOTE: Helical piles shall be installed to appropriate depth in suitable bearing stratum as
determined by the geotechnical engineer or local jurisdictional authority. Torque correlated Helical Pile Shaft Cross-Section
capacities are based on installing the pile to its torque rating, using consistent rate of Figure 6-33
advance and RPM. A minimum factor of safety of 2 is recommended for determining
allowable capacity from correlations. Deflections of 0.25 to 0.50 inches are typical at
allowable capacity.

RS6625.280 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS

Hot Rolled HSS 6 inch Nominal Schedule 40 (0.280 inch
SHAFT nominal wall) per ASTM A500 Grade B/C with 50 ksi
minimum yield strength
Corroded
Shaft Size, OD 6.625 in 168 mm
6.612 in 167.95 mm
Corroded
Shaft Size, ID* 6.10 in 155.1 mm
6.118 in 155.4 mm
4 4 Corroded
Moment of Inertia (I)* 26.37 in 1096.1 cm
25.05 in4 1041.2 cm4
2 2 Corroded
Shaft Area (A)* 5.2 in 33.55 cm
4.94 in2 31.9 cm2
3 3 Corroded
Section Modulus (Sx-x)* 7.96 in 130.2 cm
7.58 in3 124 cm3
Corroded
Perimeter 20.8 in 52.8 cm
20.77 in 52.7 cm
Coupling Formed and Welded Square Socket
Coupling Bolts Four 1 in Dia. Grade 2 Studs
0.5 inch Thick, Formed on Matching Metal Dies, ASTM
Helix Plates
A572 Grade 80 or better
Hot Dip Galvanized per ASTM A123 Grade 75, 3.0 mil
Coatings
minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation Factor 5 ft-1 13 m-1
Torque Rating 40,000 ft-lb 54,233 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
200 kip 890 kN 150 kip 667 kN
Allowable Tension Strength 100 kip 445 kN
TORQUE CORRELATED CAPACITY
Capacity Limit Based on
Assembly of RS6625.280
Ultimate Allowable
Torque Correlation, Tension / Figure 6-34
Compression 200 kip 890 kN 100 kip 445 Kn
* computed with 93% of wall thickness per AISC 360-10, B4.2

Page 6-54 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® TYPE RS8625.250 HELICAL PILES
300 kip Ultimate – 150 kip Allowable Capacity

RS8625.250
Installation Torque Rating – 60,000 ft-lb
Multi-Purpose 8-5/8” Diameter, 0.250” Wall, Round HSS Shaft with welded square formed couplings

Description:
Hubbell Power Systems, Inc. , CHANCE Type RS8625.280 Helical Piles have 300 kip ultimate capacity and 150 kip working
or allowable capacity in compression or tension. This capacity is based on well documented correlations with installation
torque, which is recognized as one method to determine capacity per IBC Section 1810.3.3.1.9. Lead sections and extensions
couple together to extend the helix bearing plates to the required load bearing stratum. Round shaft helical piles offer
increased lateral and buckling resistance compared to solid square shafts with similar torque strength. Strength calculations
are based on a design corrosion level of 50 years for most soil conditions. CHANCE Type RS Helical Piles can be coupled with
square shaft lead sections (Combo Piles) to provide greater penetration into bearing soils. CHANCE Type RS Helical Piles and
Anchors feature sharpened leading edge helix plates that are circular in plan to provide uniform load bearing in most soil
conditions. Helix plates can be equipped with “sea-shell” cuts on the leading edge to enhance penetration through dense
soils with occasional cobbles and debris. Custom lengths and helix configurations are available upon request. See below for
additional information and other sections of this Technical Manual for specifications and design details.

DRAWINGS AND RATINGS

7-3/8“
Square

Hole
accepts
1-1/4” Dia.
Threaded
Stud
8-5/8” Dia.
Pipe Shaft
Up to
10’ - 0
Long

3 Dia.
Spacing
Typical

1-1/4”
Dia.
Threaded
Stud

10”
45˚ Pilot Point
8“
Square
2-5/8”

Single Helix Triple Helix Helical Extension Plate Coupling Plain Exension Coupling
Lead Section Lead Section Section Detail Section Section Detail

Page 6-55 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 RS8625.250 Helical Pile Specifications & Available Configurations
Shaft – HSS 8-5/8 inch OD x 0.250 inch (schedule 20) wall steel shaft produced exclusively
for CHANCE products.
Coupling – formed and welded as a deep square socket, connected with multiple threaded
studs and nuts.
Helix – ½, 5/8, and 3/4 inch Thick: ASTM A572, or A1018, or A656 with minimum yield
strength of 50 and 80 ksi, depending on helix diameter.
6 inch Helix Pitch – a standard established by Hubbell Power Systems, Inc. for larger
diameter CHANCE Helical Anchors and Piles.
Available Helix Diameters: 16, 18, and 24 inches
All helix plates are spaced 3 times the diameter of the preceding (lower) helix unless
otherwise specified.
The Standard helix plate has straight sharpened leading edges or can be ordered with a
“sea shell” cut. The “sea shell” cut is best suited when it is necessary to penetrate soils
with fill debris, cobbles, or fractured rock.
Configurations:
Single, double, triple, Lead Sections, 5, 7, 10, 15, and 20 feet long
Plain Extensions, 5, 7, 10, 15, and 10 feet long
Extensions with Helix Plates, 10 feet long CHANCE Type RS8625.250
Helical Pile Shaft Cross-Section
DRAWINGS AND RATINGS

Helical products are Hot Dip Galvanized per ASTM A123 Grade 75.
Figure 6-35
NOTE: Helical piles shall be installed to appropriate depth in suitable bearing stratum
as determined by the geotechnical engineer or local jurisdictional authority. Torque
correlated capacities are based on installing the pile to its torque rating, using consistent
rate of advance and RPM. A minimum factor of safety of 2 is recommended for
determining allowable capacity from correlations. Deflections of 0.25 to 0.50 inches are
typical at allowable capacity.

RS8625.250 HELICAL PILE AND ANCHOR PRODUCT SPECIFICATIONS

Hot Rolled HSS 8 inch Nominal Schedule 20 (0.250 inch
SHAFT nominal wall) per ASTM A500 Grade B/C with 50 ksi
minimum yield strength
Corroded
Shaft Size, OD 8.625 in 219 mm
8.612 in 218.7 mm
Corroded
Shaft Size, ID* 8.16 in 207.3 mm
8.172 in 207.5 mm
Corroded
Moment of Inertia (I)* 54.12 in4 2249.5 cm4
51.09 in4 2123.6 cm4
Corroded
Shaft Area (A)* 6.14 in2 39.6 cm2
5.80 in2 37.4 cm2
Corroded
Section Modulus (Sx-x)* 12.55 in3 205.2 cm3
11.87 in3 194.1 cm3
Corroded
Perimeter 27.1 in 68.8 cm
27.05 in 68.1 cm
Coupling Formed and Welded Square Socket
Coupling Bolts Four 1-1/4 in Dia. Grade 2 Studs
0.5 - 0.75 inch Thick, Formed on Matching Metal Dies,
Helix Plates
ASTM A572 Grade 80 or better
Hot Dip Galvanized per ASTM A123 Grade 75, 3.0 mil
Coatings
minimum thickness or Bare Steel
TORQUE PROPERTIES
Torque Correlation Factor 5 ft-1 13 m-1
Torque Rating 60,000 ft-lb 81,349 N-m
STRUCTURAL CAPACITY
Nominal LRFD Design
Tension Strength
300 kip 1334 kN 225 kip 1001 kN
Allowable Tension Strength 150 kip 667 kN
TORQUE CORRELATED CAPACITY
Capacity Limit Based on
Assembly of RS8625.250
Ultimate Allowable
Torque Correlation, Tension / Figure 6-36
300 kip 1334 kN 150 kip 667 kN
Compression
* computed with 93% of wall thickness per AISC 360-10, B4.2

Page 6-56 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® ROCK-IT™ HELICAL LEAD

Description:
The ROCK-IT™ Lead Section is an innovative solution to penetrate rocky or high
blow count soils without pre-drilling or field modification. The single carbide,
patent pending design was developed after site testing of several rock anchor
configurations to provide an economical, yet proven solution to reach load-bearing
depths in high blow count material.

Key Benefits:
• Wear resistant, offset carbide tip designed to break through rocky soil
• Reduced installation time to save time and money
• Reduced spiking of torque and chatter during installation for better pile
performance and a safer alternative

DRAWINGS AND RATINGS

CATALOG NO. ANCHOR FAMILY DESCRIPTION*
C1101290 SS5 or SS150 Square Shaft Anchor, SS5 or SS150, 6/8 x 3 ft. ROCK-IT
C1101291 SS5 or SS150 Square Shaft Anchor, SS5 or SS150, 8/10 x 3 ft. ROCK-IT
C1101292 SS5 or SS150 Square Shaft Anchor, SS5 or SS150, 8/10 x 5 ft. ROCK-IT
C1101293 SS175 Square Shaft Anchor, SS175, 8/10/12 x 5 ft. ROCK-IT
C1101294 SS175 Square Shaft Anchor, SS175, 8/10 x 5 ft. ROCK-IT
C1101295 SS175 Square Shaft Anchor, SS175, 6/8 x 3 ft. ROCK-IT
C1101296 SS175 Square Shaft Anchor, SS175, 8/10 x 3 ft. ROCK-IT
C1101297 SS200 Square Shaft Anchor, SS200, 8/10/12 x 7 ft. ROCK-IT
C1101298 SS225 Square Shaft Anchor, SS225, 8/10/12 x 7 ft. ROCK-IT
*See helical pile and anchor specifications of the product
family for torque rating, helix strengths and pile capacities.

Figure 6-37

Page 6-57 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 TYPE SS/RS COMBINATION HELICAL PILES
CHANCE® Helical Transition Coupler
Adapts Type SS to Type RS Pile Shafts

The Type SS/RS Combination Pile is used mainly in compression applications in

areas where soft/loose soils are located above the bearing strata (hard/dense
soils) for the helices. The Type RS material with its much greater section modulus
will resist columnar buckling in the soft/loose soil. Its larger shaft diameter also
provides for lateral load resistance. Due to its slender size, the Type SS material
provides the means for the helix plates to penetrate deeper into hard/dense
soil stratum than if the helical pile shaft was pipe shaft only. For a given helix
configuration and same available installation energy (i.e. machine), a small
displacement shaft will penetrate farther into a soil bearing strata than a large
displacement shaft and will disturb less soil.
It is recommended that a CHANCE SS/RS Combination Helical Pile be
used in all projects where pipe shaft is being used. The square shaft
lead section will provide better load capacity and less settlement than a
DRAWINGS AND RATINGS

comparable straight pipe shaft pile.

The transition section (see Figure 6-38) adapts Type SS helical lead sections to Type
RS plain extensions. Installation of this combination pile is the same as a standard
Pile Assembly with
helical pile. Table 6-5 provides the various standard transition couplers that are
Transition Coupler
available along with their ratings. Special transition couplers, such as RS2875
to RS4500, are also available. Please contact your area CHANCE Distributor for
Figure 6-38
availability and delivery times.

TABLE 6-5: TRANSITION COUPLERS

KT
CATALOG NUMBER DESCRIPTION TORQUE RATINGS SAND CLAY
< 30' ≥ 30' < 30' ≥ 30'
SS5/SS150 SQUARE SHAFT TO
C1071639 5,500 ft-lbs 10 9.5 9.5 9.5
RS2875.203 ROUND SHAFT
SS150 SQUARE SHAFT TO
C1071639 7,000 ft-lbs 10 9.5 9.5 9.5
RS2875.276 ROUND SHAFT

SS175 SQUARE SHAFT TO

C1072501 8,000 ft-lbs 10 9.5 9.5 9.5
RS2875.276 ROUND SHAFT

SS175 SQUARE SHAFT TO

C1071515 10,500 ft-lbs 9.5 9 9 8.5
RS3500.300 ROUND SHAFT

SS200 SQUARE SHAFT TO

C1072502 13,000 ft-lbs 9.5 8.5 9 8
RS3500.300 ROUND SHAFT

Page 6-58 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
CHANCE® HELICAL PULLDOWN®
MICROPILES
Grout Reservoir
The CHANCE Helical Pulldown Micropile (HPM) is a
patented (U.S. patent 5,707,180) method used to form
a grout column around the shaft of a standard square
shaft or pipe shaft helical pile/anchor. The installation
process can employ grout only (see Figure 6-39) or grout Neat Cement Grout
in combination with either steel or PVC casing (see Figure (Very Flowable)
6-40). The result is a helical pile with grouted shaft similar,
Square (SS) or
in terms of installation, to drilled and grouted anchors or Round (RS)
Shaft Extension
auger cast-in-place piles using gravity grouting.
Extension
Displacement Plate
The initial reason for developing the HPM was to Cased Extension
Displacement
design a helical pile with sufficient shaft size to resist Plate
buckling. However, since its inception, the method has Square (SS) or
demonstrated more advantages than simply buckling Round (RS)
Shaft Extension Steel or PVC Pipe
resistance. The advantages and limitations, based on the
results of field tests, are summarized herein:

DRAWINGS AND RATINGS

Lead Cased Lead
Displacement Plate
Displacement
Plate
1. Increase buckling capacity of a helical pile shaft in Cased Lead
Displacement Plate
soft/loose overburden soils to the point that end-
bearing controls failure.
2. Increased compression capacity due to the
mobilization of skin friction at the grout/soil
interface. Total capacity is a function of both skin STD. STD.
Lead Lead
friction and end-bearing. Section Section
3. Provides additional corrosion protection to
anchor shaft in aggressive soils. The grout
column provides additional corrosion protection
to the steel pile shaft from naturally occurring
aggressive soils with high metal loss rates, organic
soils such as peat or other corrosive environments
like slag, ash, swamp, chemical waste, or other
man-made material. Figure 6-39 Figure 6-40
4. Stiffens the load/deflection response of helical
piles. Axial deflection per unit load is typically less
than with un-grouted shafts.

The installation procedure for CHANCE Helical Pulldown Micropiles is rather unique in that the soil along the sides of the
shaft is displaced laterally and then replaced and continuously supported by the flowable grout as the pile is installed. To
begin the installation process, a helical pile/anchor is placed into the soil by applying torque to the shaft. The helical shape
of the bearing plates creates a significant downward force that keeps the pile advancing into the soil. After the lead section
with the helical plates penetrates the soil, a lead displacement plate and extension are placed onto the shaft. Resuming
torque on the assembly advances the helical plates and pulls the displacement plate downward, forcing soil outward to
create a cylindrical void around the shaft. From a reservoir at the surface, a flowable grout is gravity fed and immediately
fills the void surrounding the shaft. Additional extensions and displacement plates are added until the helical bearing
plates reach the minimum depth required or competent load-bearing soil. This displacement pile system does not require
removing spoils from the site.

Page 6-59 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 TABLE 6-6: THEORETICAL GROUT VOLUME PER FOOT (METER)
Grout Column Diameter inches (mm) Pile Shaft Size inches (mm) Grout Volume ft3/ft (m3/m)

4 (102) 1-1/2 (38) solid square 0.071 (0.007)

1-1/2 (38) solid square 0.120 (0.011)

5 (127)
1-3/4 (44) solid square 0.115 (0.011
1-1/2 (38) solid square 0.181 (0.017)
1-3/4 (44)solid square 0.175 (0.016)
2 (51) solid square 0.169 (0.016)
2-1/4 (57) solid square 0.161 (0.015)
6 (152)
2-7/8 x 0.203 (73 x 5.2) pipe shaft 0.185 (0.017)
2-7/8 x 0.276 (73 x 7) pipe shaft 0.181 (0.017)
3-1/2 x 0.300 (89 x 7.6) pipe shaft 0.176 (0.016)
4-1/2 x 0.337 (114 x 8.6) pipe shaft 0.166 (0.015)
1-1/2 (38) solid square 0.249 (0.023)
DRAWINGS AND RATINGS

1-3/4 (44) solid square 0.246 (0.023)

2 (51) solid square 0.240 (0.022)
7 (178)
2-1/4 (57) solid square 0.232 (0.022)
3-1/2 x 0.300 (89 x 7.6) pipe shaft 0.246 (0.023)
4-1/2 x 0.337 (114 x 8.6) pipe shaft 0.237 (0.022)
1-3/4 (44) solid square 0.328 (0.030)
2-7/8 x 0.203 (73 x 5.2) pipe shaft 0.337 (0.031)
8 (203) 2-7/8 x 0.276 (73 x 7) pipe shaft 0.333 (0.031)
3-1/2 x 0.300 (89 x 7.6) pipe shaft 0.328 (0.030)
4-1/2 x 0.337 (114 x 8.6) pipe shaft 0.319 (0.029)
2 (51) solid square 0.367 (0.034)
8.5 (216)
2-1/4 (57) solid square 0.359 (0.033)
1-3/4 (44) solid square 0.524 (0.049)
2 (51) solid square 0.517 (0.048)
10 (254) 2-1/4 (57) solid square 0.511 (0.047)
3-1/2 x 0.300 (89 x 7.6) pipe shaft 0.525 (0.049)
4-1/2 x 0.337 (114 x 8.6) pipe shaft 0.515 (0.048)

Multiply volume in chart by grout column length to get total volume.

Grout volume per length of shaft extension can easily be calculated by multiplying the shaft length by the volume in the
chart. Be sure to convert your units to feet or meters.
Note that if the piles are un-cased, more grout may be required due to irregularities in the column, and subsurface voids.
Also, don’t forget to add for the grout bath and waste when bidding the job.

Higher Compression Strengths with Grouted Shafts

The following tables provide the nominal, LRFD design, and ASD allowable compression strengths of helical piles with
various diameter grouted shafts. The strengths listed are based on an unsupported shaft length of 10 feet (3 meters) with
either a fixed or pinned end condition at the pile head. The grout column diameters listed are the most common used per
each helical product family. Each table includes the compression strengths of shafts without grout for comparison.

Per the International Building Code (IBC) 2006 Section 1808.2.9.2 & IBC 2009 Section 1810.2.1, the depth to fixity of piles
driven into soft ground can be considered fixed and laterally supported at 10 feet below the ground surface.

Page 6-60 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type SS5 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 13.6 (60) 12.2 (54) 8.1 (36) 26.6 (118) 24.0 (107) 16.0 (71)
4” OD 30.2 (134) 22.6 (101) 15.1 (67) 59.2 (263) 44.4 (198) 29.6 (132)
5” OD 54.9 (244) 41.2 (183) 27.4 (122) 104.5 (465) 78.3 (348) 52.2 (232)
6” OD 86.2 (383) 64.6 (287) 43.1 (192) 148.3 (660) 111.2 (495) 74.1 (330)
7” OD 126.2 (561) 94.6 (421) 63.1 (281) 194.6 (866) 145.9 (649) 97.3 (433)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type SS150 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed

DRAWINGS AND RATINGS

Nominal Design Allowable Nominal Design Allowable
No Grout 13.6 (60) 12.2 (54) 8.1 (36) 26.6 (118) 24.0 (107) 16.0 (71)
4” OD 30.2 (134) 22.6 (101) 15.1 (67) 59.2 (263) 44.4 (198) 29.6 (132)
5” OD 54.9 (244) 41.2 (183) 27.4 (122) 104.5 (465) 78.3 (348) 52.2 (232)
6” OD 86.2 (383) 64.6 (287) 43.1 (192) 148.3 (660) 111.2 (495) 74.1 (330)
7” OD 126.8 (564) 95.1 (423) 63.4 (282) 208.4 (927) 156.3 (695) 104.2 (464)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type SS175 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 25.8 (115) 23.2 (103) 15.4 (69) 50.5 (225) 45.4 (202) 30.2 (134)
5” OD 66.6 (296) 49.9 (222) 33.3 (148) 127.2 (566) 95.4 (424) 63.6 (283)
6” OD 111.5 (496) 83.6 (372) 55.7 (248) 185.6 (826) 139.2 (619) 92.8 (413)
7” OD 158.3 (704) 118.7 (528) 79.1 (352) 236.2 (1051) 177.2 (788) 118.1 (525)
8” OD 209.2 (931) 156.9 (698) 104.6 (465) 290.4 (1292) 217.8 (969) 145.2 (646)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type SS200 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 43.7 (194) 39.3 (175) 26.2 (117) 85.6 (381) 77.1 (343) 51.3 (228)
6” OD 128.7 (572) 96.6 (430) 64.4 (286) 233.9 (1040) 175.4 (780) 116.9 (520)
7” OD 201.9 (898) 151.4 (673) 101.0 (449) 312.9 (1392) 234.6 (1044) 156.4 (696)
8.5” OD 294.7 (1311) 221.0 (983) 147.4 (656) 407.6 (1813) 305.7 (1360) 203.8 (907)
10” OD 401.4 (1786) 301.1 (1339) 200.7 (893) 513.6 (2285) 385.2 (1713) 256.8 (1142)

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with

IBC Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft
capacity.
3 Column length to “fixity” of shaft in soil = 10 feet (3 meters)

Page 6-61 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type SS225 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 70.9 (315) 63.8 (284) 42.5 (189) 139.0 (618) 125.1 (556) 83.2 (370)
6” OD 154.9 (689) 116.2 (517) 77.5 (345) 281.8 (1254) 211.4 (940) 140.9 (627)
7” OD 228.8 (1018) 171.6 (763) 114.4 (509) 363.2 (1171) 272.4 (1212) 181.6 (808)
8.5” OD 354.3 (1576) 265.7 (1182) 177.1 (788) 482.3 (2145) 361.7 (1609) 241.1 (1072)
10” OD 466.1 (2073) 349.6 (1555) 233.1 (1037) 591.3 (2630) 443.5 (1973) 295.7 (1315)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type RS2875.203 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
DRAWINGS AND RATINGS

No Grout 42.0 (187) 37.8 (168) 25.1 (112) 55.5 (247) 49.9 (222) 33.2 (148)
6” OD 95.7 (426) 71.8 (319) 47.8 (213) 125.7 (559) 94.3 (419) 62.8 (279)
8” OD 160.1 (712) 120.1 (534) 80.1 (356) 203.2 (904) 152.4 (678) 101.6 (452)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type RS2875.276 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 55.2 (246) 49.7 (221) 33.0 (147) 73.9 (329) 66.5 (296) 44.3 (197)
6” OD 114.3 (508) 85.7 (381) 57.1 (254) 147.7 (657) 110.8 (493) 73.9 (329)
8” OD 181.4 (807) 136.0 (605) 90.7 (403) 226.9 (1009) 170.2 (757) 113.5 (505)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type RS3500.300 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 90.7 (403) 81.6 (363) 54.3 (242) 110.0 (49) 99.0 (440) 65.9 (293)
6” OD 145.1 (645) 108.8 (484) 72.5 (322) 175.6 (781) 131.7 (586) 87.8 (391)
7” OD 179.3 (798) 134.4 (598) 89.6 (399) 214.1 (952) 160.6 (714) 107.0 (476)
8” OD 216.7 (964) 162.5 (723) 108.4 (482) 257.3 (1145) 193.0 (859) 128.6 (572)
10” OD 314.4 (1399) 235.8 (1049) 157.2 (699) 365.6 (1626) 274.2 (1220) 182.8 (813)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of CHANCE® Type RS4500.337 Grouted Shaft Piles in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 156.3 (695) 140.7 (626) 93.6 (416) 175.3 (780) 157.8 (702) 105.0 (467)
6” OD 195.3 (869) 146.5 (652) 97.6 (434) 220.6 (981) 165.5 (736) 110.3 (491)
7” OD 230.4 (1025) 172.8 (769) 115.2 (512) 259.6 (1155) 194.7 (866) 129.8 (577)
8” OD 274.2 (1220) 205.6 (915) 137.1 (610) 306.4 (1363) 229.8 (1022) 153.2 (681)
10” OD 372.8 (1658) 279.6 (1244) 186.4 (829) 415.0 (1846) 311.3 (1385) 207.5 (923)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.
3 Column length to “fixity” of shaft in soil = 10 feet (3 meters)

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CHANCE® DRIVECAST™ SCREW DISPLACEMENT PILES
The CHANCE Drivecast screw displacement pile utilizes soil displacement methodology which allows
the pile to be advanced into the soil by rotation. Pile sections are comprised of a centralized steel
shaft and a patented displacement assembly placed at regular intervals from the pile tip. By design,
the pile establishes a cylindrical void which allows a column of grout to be immediately pulled down
from a gravity-fed reservoir, creating a grouted, high capacity pile.

Drivecast piles are made from structural steel meeting the requirements of ASTM A500, A572, A656,
and A1018. The displacement paddle extends from the perimeter of the central shaft to the outer
edge of the lower helix. Depth requirements are achieved by adding 5’ or 10’ extension sections via
couplings and structural grade bolts.

DISPLACEMENT PLATES FOR CASED GROUT COLUMNS

DRAWINGS AND RATINGS

Lead Displacement Plates Extension Displacement Plates
Catalog Plate Dia Casing Dia Product Catalog Plate Dia Casing Dia Product
Number (in) (in) Series Number (in) (in) Series
T1100911 5 4 SS5/SS150 T1100913 5 4 SS5/SS150
C1100912 7 6 SS175 C1100914 7 6 SS175

DISPLACEMENT PLATES FOR UNCASED GROUT COLUMNS

Lead Displacement Plates Lead Displacement Plates

Catalog Number Plate Dia (in) Product Series Catalog Number Plate Dia (in) Product Series
T1100915 5 SS5/SS150 T1100917 5 SS5/SS150
C1100916 5 SS175 C1100918 5 SS175

COMMON LEAD CONFIGURATIONS

CHANCE Helical Round-Cornered Square Shaft Leads used with HELICAL PULLDOWN® Micropile (1)
Helix Plate Diameter (in)
Figure 6-41
Catalog Nominal Effective Helix
Type Weight
Number A B C D Length (ft) Length (ft) Grade

SS5 C1100921 8 10 12 - 7 76.2 79 50

SS175 C1100922 8 10 12 - 7 76.2 100 50

(1) HELICAL PULLDOWN® Micropiles use Standard Exten-

Page 6-63 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 HIGH COMPRESSION STRENGTH WITH DRIVECAST™ PILES IN SOFT SOIL
The following tables provide the nominal, LRFD design, and ASD allowable compression strengths of Drivecast piles with
various diameter grout shafts in soft soils. The strengths listed are based on an unsupported length of 10 feet (3 meters)
with either a fixed or pinned end condition at the pile head. The grout column diameters listed reflect the results in various
soil conditions. In clay, the grout column is generally close to the diameter of the small plate on the displacement assembly.
In sand, the grout column ranges between the small and large diameter plates on the displacement assembly. In loose sand
fill, the grout column can exceed the diameter of the large plate on the displacement assembly. Each table includes the
compression strengths of shafts without external grout for comparison.

Per the International Building Code(IBC) 2015 Section 1810.2.1, the depth to fixity of piles driven into soft ground can be
considered fixed and laterally supported at 10 feet below ground surface.

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type SS175 Central Shafts in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
DRAWINGS AND RATINGS

Nominal Design Allowable Nominal Design Allowable

No Grout 25.8 (155.6) 23.2 (103.9) 15.4 (69.0) 50.5 (226.3) 45.4 (203.4) 30.2 (135.3)
8” OD 217.4 (974.4) 163.1 (731.0) 108.7 (487.2) 316.5 (1418.6) 237.3 (1063.6) 158.2 (709.0)
9” OD 280.6 (1257.7) 210.5 (943.5) 140.3 (628.8) 381.2 (1708.6) 285.9 (1281.4) 190.6 (854.3)
10” OD 350.2 (1569.6) 262.7 (1177.4) 175.1 (784.8) 451.4 (2023.2) 338.5 (1517.2) 225.7 (1011.6)
11” OD 426.0 (1909.4) 319.5 (1432.0) 213.0 (954.7) 527.1 (2362.5) 395.3 (1771.8) 263.6 (1181.5)
12” OD 507.9 (2276.5) 380.9 (1707.2) 253.9 (1138.0) 608.6 (2727.8) 456.5 (2046.1) 304.3 (1363.9)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type SS200 Central Shafts in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 43.7 (195.8) 39.3 (176.1) 26.2 (117.4) 85.6 (383.6) 77.1 (345.5) 51.3 (229.9)
8” OD 262.2 (1175.2) 196.6 (881.2) 131.1 (587.6) 374.8 (1679.9) 281.1 (1259.9) 187.4 (839.9)
9” OD 328.8 (1473.7) 246.6 (1105.3) 164.4 (736.8) 441.6 (1979.3) 331.2 (1484.5) 220.8 (989.6)
10” OD 401.4 (1799.1) 301.1 (1349.5) 200.7 (899.5) 513.6 (2302.0) 385.2 (1726.5) 256.8 (1151.0)
11” OD 479.8 (2150.5) 359.9 (1613.1) 239.9 (1075.2) 590.9 (2648.5) 443.2 (1986.5) 295.5 (1324.4)
12” OD 564.0 (2527.9) 423.0 (1895.9) 282.0 (1263.9) 673.8 (3020.1) 505.3 (2264.8) 336.9 (1510.0)
13” OD 654.1 (2931.8) 490.5 (2198.5) 327.0 (1465.6) 762.3 (3416.7) 571.8 (2562.9) 381.2 (1708.6
14” OD 749.9 (3361.2) 562.5 (2521.2) 375.0 (1680.8) 856.8 (3840.3) 642.6 (2880.2) 428.4 (1920.1)
15” OD 851.8 (3817.9) 638.8 (2863.2) 425.9 (1908.9) 957.3 (4290.8) 718.0 (3218.2) 478.7 (2145.6)
16” OD 959.7 (4301.5) 719.7 (3225.8) 479.8 (2150.5) 1063.9 (4768.6) 798.0 (3576.8) 532.0 (2384.5)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.
3 Column length to “fixity” of shaft in soil = 10 feet (3 meters)

Page 6-64 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type RS3500.300 Central Shafts in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 90.66 (403.3) 81.59 (362.9) 54.28 (241.4) 110.01 (489.3) 99.01 (440.4) 65.88 (293.0)
Grout Inside 104.27 (463.8) 78.20 (347.9) 52.14 (231.9) 131.39 (584.5) 98.55 (438.4) 65.70 (292.2)
8” OD 227.20 (1010.6) 170.40 (758.0) 113.60 (505.3) 275.51 (1225.5) 206.63 (919.1) 137.75 (612.7)
9” OD 273.01 (1214.4) 207.76 (924.2) 136.50 (607.2) 326.56 (1452.6) 244.92 (1089.5) 163.28 (726.3)
10” OD 326.90 (1454.1) 245.18 (1090.6) 163.45 (727.1) 385.18 (1713.4) 288.88 (1285.0) 192.59 (856.7)
11” OD 388.90 (1729.9) 291.68 (1297.5) 194.45 (865.0) 451.33 (2007.6) 338.50 (1505.7) 225.67 (1003.8)
12” OD 458.90 (2041.3) 344.17 (1530.9) 229.45 (1020.6) 524.92 (2335.0) 393.69 (1751.2) 262.46 (1167.5)
13” OD 536.72 (2387.4) 402.54 (1790.6) 268.36 (1193.7) 605.82 (2694.8) 454.36 (2021.1) 302.91 (1347.4)
14” OD 622.20 (2767.7) 466.65 (2075.8) 311.10 (1383.8) 693.90 (3086.6) 520.43 (2315.0) 346.95 (1543.3)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type RS4500.337 Central Shafts in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)

DRAWINGS AND RATINGS

Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 156.30 (700.5) 140.67 (630.5) 93.59 (419.4) 175.30 (785.7) 157.77 (707.1) 104.97 (470.4)
Grout Inside 190.46 (853.6) 142.84 (640.2) 95.23 (426.8) 219.25 (982.7) 164.44 (737.0) 109.63 (491.3)
8” OD 302.24 (1354.7) 226.68 (1016.0) 151.12 (677.3) 344.32 (1543.3) 258.24 (1157.4) 172.16 (771.6)
9” OD 347.89 (1559.3) 260.92 (1169.4) 173.94 (779.6) 395.11 (1770.9) 296.33 (1328.2) 197.56 (885.5)
10” OD 440.88 (1976.1) 300.66 (1347.6) 200.44 (898.4) 453.02 (2030.5) 339.76 (1522.8) 226.51 (1015.2)
11” OD 461.50 (2068.5) 346.12 (1551.3) 230.75 (1034.2) 518.18 (2322.5) 388.64 (1741.9) 259.09 (1161.2)
12” OD 529.87 (2374.9) 397.41 (1781.2) 264.94 (1187.5) 590.67 (2647.5) 443.00 (1985.6) 295.33 (1323.7)
13” OD 606.03 (2965.76) 454.53 (2021.85) 303.02 (1347.9) 670.46 (2982.36) 502.85 (2236.79) 335.23 (1491.18)
14” OD 689.92 (3068.92) 517.44 (2301.69) 344.96 (1534.46) 757.52 (3369.62) 568.14 (2527.21) 378.76 (1684.81)
15” OD 781.42 (3475.93) 586.06 (2606.93) 390.71 (1737.97) 851.77 (3788.86) 638.83 (2841.66) 425.88 (1894.41)
16” OD 880.42 (3916.30) 660.32 (2947.25) 440.21 (1958.15) 953.14 (4239.78) 714.85 (3179.81) 476.57 (2119.89)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type RS8625.250 Central Shafts in Soft Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Soft Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 272.91 245.62 163.42 280.85 252.76 168.17
Grout Inside 490.33 367.75 245.17 513.39 385.04 256.69
12” OD 674.76 506.07 337.38 708.49 531.37 354.24
13” OD 749.04 561.78 374.52 787.13 590.35 393.56
14” OD 830.02 622.52 415.01 872.47 654.35 436.23
15” OD 917.93 688.45 458.97 964.63 723.47 482.31
16” OD 1012.92 759.69 506.46 1063.69 797.76 531.84
17” OD 1115.13 836.34 557.56 1169.72 877.29 584.86
18” OD 1224.62 918.46 612.31 1282.76 962.07 641.38
19” OD 1341.44 1006.08 670.72 1402.82 1052.12 701.41
20” OD 1465.58 1099.19 732.79 1529.92 1147.44 764.96
21” OD 1597.04 1197.78 798.52 1664.02 1248.02 832.01
22” OD 1735.76 1301.82 867.88 1805.12 1353.84 902.56

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5, and the lead section with which the extension is used will provide sufficient helix capacity to develop the full shaft capacity.
3 Column length to “fixity” of shaft in soil = 10 feet (3 meters)

Page 6-65 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 HIGH COMPRESSION STRENGTH WITH DRIVECAST™ PILES IN FIRM SOILS
The following tables provide the nominal, LRFD design, and ASD allowable compression strengths of Drivecast piles with
various diameter grout shafts in firm soils. The strengths listed are based on an unsupported length of 5 feet (3 meters) with
either a fixed or pinned end condition at the pile head. The grout column diameters listed reflect the results in various soil
conditions. In clay, the grout column is generally close to the diameter of the small plate on the displacement assembly. In
sand, the grout column ranges between the small and large diameter plates on the displacement assembly. In loose sand
fill, the grout column can exceed the diameter of the large plate on the displacement assembly. Each table includes the
compression strengths of shafts without external grout for comparison.

Per the International Building Code (IBC) 2015 Section 1810.2.1, the depth to fixity of piles driven into firm ground can be
considered fixed and laterally supported at 5 feet below ground surface.

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type SS175 Central Shafts in Firm Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Firm Soil
Diameter Pinned Fixed
DRAWINGS AND RATINGS

Nominal Design Allowable Nominal Design Allowable

No Grout 103.02 (461.7) 92.82 (416.0) 61.69 (276.5) 164.26 (736.2) 147.83 (662.6) 98.36 (440.8)
8” OD 386.26 (1731.3) 289.6 (1298.4) 193.13 (865.6) 424.24 (1901.5) 318.18 (1426.1) 212.12 (950.7)
9” OD 448.60 (2010.7) 336.4 (1508.0) 224.30 (1005.3) 484.31 (2170.7) 363.24 (1628.1) 242.16 (1085.4)
10” OD 516.53 (2315.1) 387.40 (1736.4) 258.26 (1157.5) 550.36 (2466.8) 412.77 (1850.1) 275.18 (1233.4)
11” OD 590.27 (2645.7) 442.7 (1984.2) 295.13 (1322.8) 622.55 (2790.4) 466.91 (2092.7) 311.27 (1395.1)
12” OD 670.00 (3003.0) 502.5 (2252.3) 335.00 (1501.5) 701.01 (3142.0) 525.76 (2356.5) 350.50 (1571.0)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type SS200 Central Shafts in Firm Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Firm Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 167.34 (750.0) 150.60 (675.0) 100.20 (449.1) 239.01 (1071.2) 215.11 (964.1) 143.12 (641.4)
8” OD 453.11 (2030.9) 339.83 (1523.1) 226.55 (1015.4) 495.45 (2220.7) 371.59 (1665.5) 247.72 (1110.3)
9” OD 516.55 (2315.2) 387.42 (1736.5) 258.28 (1157.6) 556.10 (2492.5) 417.07 (1869.3) 278.05 (1246.2)
10” OD 585.45 (2624.1) 439.08 (1968.0) 292.72 (1312.0) 622.66 (2790.8) 466.99 (2093.1) 311.33 (1395.4)
11” OD 660.02 (2958.3) 495.02 (2218.7) 330.01 (1479.1) 695.29 (3116.4) 521.47 (2337.3) 347.64 (1558.1)
12” OD 740.48 (3318.9) 555.36 (2489.2) 370.24 (1659.4) 774.13 (3469.8) 580.60 (2602.3) 387.06 (1734.8)
13” OD 826.98 (3706.7) 620.24 (2780.0) 413.49 (1853.3) 859.27 (3851.4) 644.46 (2888.6) 429.64 (1925.7)
14” OD 919.66 (4122.1) 689.74 (3091.5) 459.83 (2061.0) 950.81 (4261.7) 713.10 (3196.2) 475.40 (2130.8)
15” OD 1018.6 (4565.5) 763.95 (3424.1) 509.30 (2282.7) 1048.78 (4700.8) 786.59 (3525.6) 524.39 (2350.4)
16” OD 1123.8 (5037.4) 842.91 (3778.1) 561.94 (2518.7) 1153.25 (5169.1) 864.94 (3876.8) 576.62 (2584.5)
For SI: 1 kip = 4.448 kN.
1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft & firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5.
3 Column length to “fixity” of shaft in soft soil = 10 feet (3 meters), and 5 feet (1.5 meters).

Page 6-66 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type RS3500.300 Central Shafts in Firm Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Firm Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 121.92 (546.4) 109.73 (491.8) 73.01 (327.2) 127.97 (573.5) 115.17 (516.2) 76.63 (343.4)
Grout Inside 148.57 (665.9) 111.43 (499.4) 74.28 (332.9) 157.41 (705.5) 118.06 (529.1) 78.70 (352.7)
8” OD 305.22 (1368.0) 228.92 (1026.0) 152.61 (684.0) 320.30 (1435.6) 240.22 (1076.7) 160.15 (717.8)
9” OD 359.15 (1609.7) 269.37 (1207.3) 179.58 (804.9) 375.60 (1683.5) 281.70 (1262.6) 187.80 (841.7)
10” OD 420.25 (1883.6) 315.19 (1412.7) 210.13 (941.8) 437.84 (1962.4) 328.38 (1471.8) 218.92 (981.2)
11” OD 488.48 (2189.4) 366.36 (1642.1) 244.24 (1094.7) 507.01 (2272.5) 380.26 (1704.4) 253.50 (1136.2)
12” OD 563.78 (2526.9) 422.84 (1895.2) 281.89 (1263.4) 583.05 (2613.3) 437.29 (1960.0) 291.53 (1306.7)
3233.04
13” OD 646.08 (2895.8) 484.56 (2171.9) 665.94 (2984.8) 499.45 (2238.6) 332.97 (1492.4)
(14491.1)
14” OD 735.30 (3295.7) 551.48 (2471.8) 367.65 (1647.8) 755.63 (3386.8) 566.72 (2540.1) 377.81 (1693.4)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type RS4500.337 Central Shafts in Firm Soil1,2,3

DRAWINGS AND RATINGS

Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Firm Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 186.32 (835.1) 167.69 (751.6) 111.57 (500.0) 191.74 (859.4) 172.57 (773.4) 114.82 (514.6)
Grout Inside 236.28 (1059.0) 177.21 (794.2) 118.14 (529.5) 244.7 (1097.0) 183.56 (822.7) 122.37 (548.4)
8” OD 369.00 (1653.9) 276.75 (1240.4) 184.50 (826.9) 381.23 (1708.7) 285.92 (1281.5) 190.61 (854.3)
9” OD 422.75 (1894.8) 317.07 (1421.1) 211.38 (947.4) 436.42 (1956.1) 327.32 (1467.1) 218.21 (978.0)
10” OD 483.42 (2166.7) 362.57 (1625.1) 241.71 (1083.3) 498.43 (2234.0) 373.82 (1675.5) 249.21 (1117.0)
11” OD 551.08 (2470.0) 413.31 (1852.5) 275.54 (1235.0) 567.27 (2542.6) 425.46 (1907.0) 283.64 (1271.3)
12” OD 625.75 (2804.7) 469.31 (2103.5) 312.88 (1402.3) 642.98 (2881.9) 482.23 (2161.4) 321.49 (1440.9)
13” OD 707.43 (3146.8) 530.57 (2360.1) 353.72 (1573.4) 725.53 (3227.3) 544.15 (2420.5) 362.76 (1613.6)
14” OD 796.09 (3541.2) 597.07 (2655.9) 398.05 (1770.6) 814.91 (3624.9) 611.19 (2718.7 407.46 (1812.5)
15” OD 891.69 (3966.4) 668.76 (2974.8) 445.84 (1983.2) 911.11 (4052.8) 683.33 (3039.6) 455.56 (2026.4)
16” OD 994.18 (4422.3) 745.63 (3316.7) 497.09 (2211.2) 1014.1 (4510.9) 760.57 (3383.2) 507.05 (2255.4)

Nominal, LRFD Design, and ASD Allowable Compression Strengths of Drivecast Piles, Type RS8625.250 Central Shafts in Firm Soil1,2,3
Nominal, LRFD Design, and ASD Allowable Compression Strengths kip (kN)
Grout Column Firm Soil
Diameter Pinned Fixed
Nominal Design Allowable Nominal Design Allowable
No Grout 285.16 256.64 170.75 287.21 258.49 171.98
Grout Inside 526.07 394.55 263.03 532.15 399.11 266.07
12” OD 727.09 545.32 363.54 736.01 552.01 368.01
13” OD 808.15 606.11 404.07 818.23 613.67 409.12
14” OD 895.89 671.92 447.95 907.13 680.35 453.57
15” OD 990.39 742.79 495.20 1002.75 752.06 501.38
16” OD 1091.68 818.76 545.84 1105.11 828.83 552.55
17” OD 1199.79 899.85 599.90 1214.22 910.66 607.11
18” OD 1314.75 986.07 657.38 1330.09 997.57 665.04
19” OD 1436.57 1077.43 718.28 1452.73 1089.55 726.36
20” OD 1565.23 1173.93 782.62 1582.14 1186.60 791.07
21” OD 1700.75 1275.56 850.37 1718.31 1288.73 859.15
22” OD 1843.09 1382.32 921.55 1861.23 1395.93 930.62

For SI: 1 kip = 4.448 kN.

1 Refer to Section 4.1.3 of ESR-2794 for descriptions of fixed condition, pinned condition, soft & firm soil.
2 Strength ratings are based on a design corrosion level of 50-years and presume the supported structure is braced in accordance with IBC

Section 1808.2.5.
3 Column length to “fixity” of shaft in soft soil = 10 feet (3 meters), and 5 feet (1.5 meters).

Page 6-67 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 TABLE 6-8
DRIVECAST™ PILE THEORETICAL GROUT VOLUME PER FOOT (METER)
PILE SHAFT DIAMETER in. (mm) GROUT COLUMN DIAMETER in. (mm) GROUT VOLUME (ft3/ft (m3/m)
8 (203.2) 0.321 (0.030)
9 (228.6) 0.413 (0.038)
1.75 (44) 10 (254) 0.517 (0.048)
11 (279.4) 0.632 (0.059)
12 (304.8) 0.781 (0.073)
8 (203.2) 0.304 (0.028)
9 (228.6) 0.396 (0.037)
10 (254) 0.500 (0.046)
11 (279.4) 0.614 (0.0570
2.00 (51) 12 (304.8) 0.774 (0.072)
13 (330.2) 0.876 (0.081)
DRAWINGS AND RATINGS

14 (355.6) 1.051 (0.098)

15 (381) 1.182 (0.110)
16 (406.4) 1.351 (0.126)
8 (203.2) 0.270 (0.025)
9 (228.6) 0.363 (0.034)
10 (254) 0.466 (0.043)
3.5 (89) 11 (279.4) 0.581 (0.054)
12 (304.8) 0.706 (0.066)
13 (330.2) 0.843 (0.078)
14 (355.6) 0.990 (0.092)
8 (203.2) 0.222 (0.021)
9 (228.6) 0.315 (0.029)
10 (254) 0.419 (0.039)
11 (279.4) 0.533 (0.050)
4.5 (114) 12 (304.8) 0.659 (0.061)
13 (330.2) 0.795 (0.074)
14 (355.6) 0.942 (0.088)
15 (381) 1.100 (0.102)
16 (406.4) 1.269 (0.118)
10 (254) 0.365 (0.034)
11 (279.4) 0.480 (0.045)
12 (304.8) 0.605 (0.056)
5.5 13 (330.2) 0.741 (0.069)
14 (355.6) 0.889 (0.083)
15 (381) 1.047 (0.097)
16 (406.4) 1.216 (0.113)
12 (304.8) 0.359 (0.033)
13 (330.2) 0.495 (0.046)
14 (355.6) 0.642 (0.060)
8.625 15 (381) 0.800 (0.074)
16 (406.4) 0.969 (0.090)
17 (431.8) 1.149 (0.107)
18 (457.2) 1.340 (0.124)

Page 6-68 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
REINFORCEMENT FOR UPPER 6’-0 OF DRIVECAST™ PILE GROUT COLUMNS
This table provides basic information about the option to add steel reinforcement to the grout column outside the central
steel shaft (hollow pipe or solid square) in the upper 6’-0 of soils with minimum 2” cover.

Perimeter or Reing’g (w/2” Clr) = πDr

Asr = 0.004(Ag)

(π)(16u)2
Max = 0.004 0.804 in2 Hoops = 0.009 in2/in of spacing = 0.009 in2/(”12”) = 0.11in2
4

DRAWINGS AND RATINGS

Figure 6-42
Figure 6-43

TABLE 6-9: STEEL REINFORECEMENT - DRIVECAST™ PILES

PILES O.D. Asr (in2) REINF’G PERIMETER (in) LONGIT BARS HOOPS

SS 10” 0.314 18.85 (3) #3 “3@12”

SS 11” 0.380 21.99 (4) #3 “3@12”

SS, RS 12” 0.452 25.13 (4) #3 “3@12”

SS, RS 13” 0.531 28.27 (5) #3 “3@12”

SS, RS 14” 0.616 31.42 (4) #4 “3@12”

SS, RS 15” 0.707 34.56 (4) #4 “3@12”

SS, RS 16” 0.804 37.70 (4) #4 “3@12”

SS, RS 17” 0.908 40.84 (4) #4 “3@12”

SS, RS 18” 1.018 43.98 (4) #5 “3@12”

SS, RS 19” 1.134 59.69 (4) #5 “3@12”

SS, RS 20” 1.257 62.83 (4) #5 “3@12”

SS, RS 21” 1.385 65.97 (4) #5 “3@12”

SS, RS 22” 1.520 69.12 (5) #5 “3@12”

Page 6-69 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 NEW CONSTRUCTION PILE CAPS
The CHANCE® new construction pile caps are designed for use with the CHANCE Type SS square shaft and RS round shaft
helical piles and for embedment in cast-in-place concrete foundations. Each new construction pile cap consists of either
one bearing plate and one steel tube sleeve that are factory-welded together to form the cap, or one bearing plate, two
re-bars and one steel tube sleeve that are factory-welded together. The plate type pile caps are designed to be used in
spread footings, grade beams, structural slabs, and reinforced concrete pile caps. The re-bar cap is designed to be used in
grade beams and reinforced pile caps. The concrete foundation and interaction of pile shaft, new construction pile cap, and
concrete footing for moment transfer, as applicable, must be designed and justified with due consideration to all applicable
limit states and the direction and eccentricity of applied loads, including reactions provided by the brackets, acting on the
concrete foundation. For preliminary design guidelines for reinforced pile caps refer to Section 4.
DRAWINGS AND RATINGS

New Construction Cap for Type SS Shafts New Construction Cap for Type SS Shafts
Compression Only Compression and Uplift
Figure 6-44 Figure 6-45

New Construction Cap for Type RS Shafts New Construction Cap for Type SS Shafts
Compression and Uplift Equal Compression and Uplift Capacity
Figure 6-46 Figure 6-47

Page 6-70 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
TABLE 6-10
CHANCE® helical New Construction Pile Caps

Plate Size Pipe OD &

Design (Working) Load kip (kN) Description
(square) Length

Fits SS5/SS150 and RS2875.165/RS2875.203; use for

40 (178) compression 6” x 6” x 1/2” 2-1/2” x 6”
compression only.

60 (267) compression 6” x 6” x 3/4” 3” x 6” Fits SS175; use for compression only.

40 (178) compression
6” x 6” x 1/2” 2-1/2” x 6” Fits SS5/SS150; use for uplift and compression.
20 (89) uplift
60 (267) compression
6” x 6” x 3/4” 3” x 6” Fits SS175; use for uplift and compression.
30 (133) uplift

35 (156) compression 7” x 7” x 1/2” 2-1/2” x 6” Fits SS5/SS150; use for compression only

DRAWINGS AND RATINGS

52.5 (234) compression 8” x 8” x 1/2” 2-7/8” x 6” Fits SS175; use for compression only

75 (334) compression 12” x 12” x 1/2” 3-1/2” x 6” Fits SS200; use for compression only

100 (445) compression 12” x12” x 1/2” 3-1/2” x 6” Fits SS225; use for compression only

36 (160) compression 7” x 7” x 1/2” 3-1/2” x 6” Fits RS2875; use for compression only

50 (222) compression 10” x 10” x 1/2” 4-1/2” x 6” Fits RS3500; use for compression only

70 (311) compression 12” x 12” x 1/2” 5-9/16” x 6” Fits RS4500; use for compression only

35 (156) compression
7” x 7” x 1/2” 2-1/2” x 6” Fits SS5/150: use for uplift and compression
23 (102) uplift
52.5 (234) compression
8” x 8” x 1/2” 2-7/8” x 6” Fits SS175: use for uplift and compression
37 (165) uplift
75 (334) compression
12” x 12” x 1/2” 3-1/2” x 6” Fits SS200; use for uplift and compression
45 (200) uplift
100 (445) compression
12” x 12” x 1/2” 3-1/2” x 6” Fits SS225; use for uplift and compression
40 (178) uplift
36 (160) compression
7” x 7” x 1/2” 3-1/2” Fits RS2875; use for uplift and compression
36 (160) uplift
50 (222) compression
10” x 10” x 1/2” 4-1/2” Fits RS3500; use for uplift and compression
50 (222) uplift
70 (311) compression
12” x 12” x 1/2” 5-9/16” Fits RS4500; use for uplift and compression
70 (311) uplift

Page 6-71 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
DRAWINGS AND RATINGS

Page 6-72 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 DESIGN EXAMPLES

Page 7-1 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES
SECTION 7

CONTENTS

DESIGN EXAMPLE 1.....................HELICAL PILES/ANCHORS FOR 7-4

..........................................................TELECOMMUNICATION TOWERS
DESIGN EXAMPLE 2.................................SELF SUPPORT TOWERS 7-11
............................. DESIGN WITH FIXED HEAD GRILLAGE DESIGN
DESIGN EXAMPLE 3.............................................. A FRAME STRUCTURE 7-16
...........DESIGN WITH CONCRETE CAP AND MICROPILE DESIGN
DESIGN EXAMPLES

DESIGN EXAMPLE 4...............MONOPOLE DESIGN W/O GROUP 7-25

DESIGN EXAMPLE 5....................................GUYED TRANSMISSION 7-32
...................................................................................STRUCTURE DESIGN
DESIGN EXAMPLE 6....HELICAL PILE FOUNDATION FOR NEW 7-37
............................................................... SUBSTATION CONSTRUCTION
DESIGN EXAMPLE 7........................ TYPE RS HELICAL PILES FOR 7-39
.........................................................SUBSTATION LATERAL SUPPORT
DESIGN EXAMPLE 8..........................HELICAL PILE FOUNDATION 7-42
...................FOR REMEDIATION OF SUBSTATION BUS SUPPORT
DESIGN EXAMPLE 9.... INSTANT FOUNDATIONS® FOR STREET 7-46
......................................................................................... LIGHT SUPPORTS
DESIGN EXAMPLE 10.............. FOUNDATION EARTH PRESSURE 7-50
................................................................................................... RESISTANCE
DESIGN EXAMPLE 11.................BUCKLING EXAMPLE USING THE 7-52
....................................................................................DAVISSON METHOD
DESIGN EXAMPLE 12................BUCKLING EXAMPLE USING THE 7-54
................................................................FINITE DIFFERENCE METHOD
DESIGN EXAMPLE 13................BUCKLING EXAMPLE USING THE 7-56
..................................................................... FINITE ELEMENT METHOD

Page 7-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES
DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your
own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and
from point to point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be
conducted prior to any installation to ascertain and verify compliance to relevant rules, regulations and
requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the
adoption, revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and
has every confidence in its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the
installation of CHANCE® Civil Construction foundation support products.

Page 7-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 1
HELICAL PILES/ANCHORS FOR TELECOMMUNICATION TOWERS
SYMBOLS USED IN THIS DESIGN EXAMPLE

SST..............................................................SELF SUPPORTING TOWER 7-4

Tug............................................................... UPPER GUYWIRE TENSION 7-5
IAug................................. UPPER GUYWIRE INSTALLATION ANGLE 7-5
Tlg...............................................................LOWER GUYWIRE TENSION 7-5
IAlg.................................LOWER GUYWIRE INSTALLATION ANGLE 7-5
C........................................................................................... COMPRESSION 7-5
FS.............................................................................. FACTOR OF SAFETY 7-5
DESIGN EXAMPLES

kip.............................................................................................. KILOPOUND 7-5

Ruc............................................ RECOMENDED ULTIMATE CAPACITY 7-5
Kt........................................................... TORQUE TO CAPACITY RATIO 7-6
T....................................................... MINIMUM INSTALATION TORQUE 7-7
DL.................................................................... RESULTANT AXIAL LOAD 7-7

Purpose
This design example provides an aid in the
selection of appropriate helical guywire
anchors and center mast helical piles for
telecommunication towers.
The guywire loads are to be resisted by a
helical tension anchor. When the vertical
and horizontal components are provided
the resultant must be determined as well
as the angle between the resultant load
and the horizontal, (this is the angle the
helical anchor should be installed at to
properly resist the guywire load(s)). There
may be one or more guywires that come
to the ground to be restrained by one or
more helical anchors depending on the
magnitude of the load and/or the soil
strength. Helical piles can be used to resist
the loads from the structure mast. These
loads will generally be composed of a
vertical load and a lateral load at the base
Tower Guy Anchor and Foundation
of the mast or pole.
Figure 7-1
If the structure is a self supporting tower
(SST), the loads from each leg of the tower
must be resisted. These generally consist
of vertical uplift and compression loads

Page 7-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
and a horizontal shear load at the ground line. These three loads can be dealt with in a number of ways.
Typically one or more helical piles are used for each leg of the tower and may be installed at a batter to
better resist the horizontal shear loads. Steel grillages and reinforced concrete caps have been used to
facilitate load transfer from the structure to the helical piles. This type design will not be covered in this
design example since the intent is to focus on the guyed mast tower structure.
Figure 8-18 shows the tower that will be used for these sample calculations. It will be noted that the four
upper guywires come to the ground at a single guywire point and that the three lower guywires come
to ground at a different guywire point. There must be at least a single helical anchor installed at each
of these points to provide restraint for the guywires which in turn stabilize the tower by resisting lateral
loads on the structure.
For this tower, the vertical and horizontal components of the guywire loads are given and must be
resolved into the tension load the helical guywire anchor is to resist.

Upper Guywire Loads

• Vertical load component = 16.6 kip
• Horizontal load component = 17.9 kip
• Tension in the upper guywire anchor = Tug = (16.62 + 17.92)0.5 = 24.4 k

DESIGN EXAMPLES
• Helical guywire anchor installation angle = IAug = tan-1 (16.6/17.9) = 43°

Lower Guywire Loads

• Vertical load component: 7.9 kip
• Horizontal load component: 9.7 kip
• Tension in the lower guywire anchor = Tlg = (7.92 + 9.72)0.5 = 12.5 k
• Helical guywire anchor installation angle = IAlg = tan-1 (7.9/9.7) = 39°

Mast Foundation Loads

• Compression (C) = 68.0 kip
• Horizontal shear (V) = 0.3 kip

Selecting Helical Guywire Anchors

Hubbell Power Systems, Inc. HeliCAP® engineering software will be utilized to determine the appropriate
helical anchor/pile sizes for this tower. Soil conditions are shown in the sample boring log in Figure
8-19. The soil data and guywire anchor data was input into the HeliCAP® engineering software to get an
appropriate output. The minimum acceptable Factor of Safety (FS) = 2.

Upper Guywire Helical Anchor

The HeliCAP® Summary Report for the upper guywire helical anchor is shown in Figure 7-2. This report
provides the following information:
• Helical Anchor: SS5 (1.5” square shaft, 5500 ft-lbs torque rating, 70 kips ultimate tension rating)
• Lead Section: 4 helix (8”-10”-12”-14”)
• Installation Angle: 43°
• Datum Depth (depth below grade where installation starts): 0 ft
• Length: 45 (ft along the shaft at the 43° installation angle)
• Recommended Ultimate Capacity (Ruc): 50.2t (kips tension)
The Factor of Safety for this tension anchor is Ruc /Tlg = 50.2 / 24.4 = 2.05 > 2 (OK). Use this helical
anchor at each of three upper guywire anchor locations per tower.

Page 7-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 The required average minimum installation torque (T) is:

T = (Tug x FS) / Kt Equation 7-1

= (24,400 x 2.0) / 10
= 4,900 ft-lbs
where: Kt = Empirical torque factor = 10 (default value for Type SS5 series)
T = 4,900 ft-lbs is less than the rated torque (5,500 ft-lbs) of the Type SS5 series. (OK).

Lower Guywire Helical Anchor

The HeliCAP® summary report for the lower guywire helical anchor is shown in Figure 8-21. This report
provides the following information:
• Helical Anchor: SS5 (1.5” square shaft, 5500 ft-lbs torque rating, 70 kips ultimate tension rating)
• Lead Section: 4 helix (8”-10”-12”-14”)
• Installation Angle: 39°
• Datum Depth (depth below grade where installation starts): 0 ft
• Length: 25 ft (along the shaft at the 39° installation angle)
DESIGN EXAMPLES

• Recommended Ultimate Capacity (Ruc): 26.6t (kips tension)

The Factor of Safety for this tension anchor is Ruc / Tug = 26.6 / 12.5 = 2.12 > 2 (OK) Use this helical
anchor at each of three lower guywire anchor locations per tower.

T = (Tlg x FS) / Kt Equation 7-2

= (12,500 x 2.0) / 10
= 2,500 ft-lbs
Empirical torque factor = 10 (default value for Type SS5
where: Kt =
series)
T = 2,500 ft-lbs is less than the rated torque (5,500 ft-lbs) of the Type SS5 series. (OK).

Helical Pile
Given:
• Compression Load = 68.0 k
• Shear Load = 0.3 k
Assume three helical piles installed at 120° intervals in plan view with each pile battered away from
vertical at a 10° angle:
68/3 piles = 22.67k ultimate/pile element.
Assume entire shear (0.3 k) is taken by one battered pile. Therefore, the resultant axial load (DL) to a
battered pile is:
DL = (22.672 + 0.32)0.5 = 22.7k
The HeliCAP® summary report for the helical piles is shown in Figure 8-22. This report provides the
following information:
• Helical Pile: SS175 (1.75” square shaft, 10,500 ft-lbs torque rating, 100 kips ultimate tension rating)
• Lead Section: 4 helix (8”-10”-12”-14”)
• Installation Angle: 80° below horizontal (10° away from vertical)
• Datum Depth: (depth below grade where installation starts): 0 ft
• Length: 34 ft (along the shaft at the 80° installation angle)
• Recommended Ultimate Capacity (Ruc): 50.7c (kips compression)

Page 7-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
The Factor of Safety for this compression pile is Ruc / DL = 50.7 / 22.7 = 2.23 > 2 (OK) Use three SS175
helical piles per tower base. The three helical piles must be captured in a “pile cap.” This may be a
reinforced concrete cap, the design of which is beyond the scope of this design example. The design of
this concrete pile cap is left to the structural engineer.

T = (DL x FS) / Kt Equation 7-3

= (22,700 x 2.0) / 10
= 4,500 ft-lbs
Empirical torque factor = 10 (default value for Type SS175
where: Kt =
series)
T = 4,500 ft-lbs is less than the rated torque (10,500 ft-lbs) of the type SS175 series. (OK).

DESIGN EXAMPLES

Sample Boring Log

Figure 7-2

Page 7-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES

HeliCAP® Summary Report for Upper Guywires

Figure 7-3

Page 7-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES

HeliCAP® Summary Report for Lower Guywires

Figure 7-4

Page 7-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES

HeliCAP® Summary Report for Foundations

Figure 7-5

Page 7-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 2
SELF SUPPORT TOWER DESIGN WITH FIXED HEAD GRILLAGE DESIGN
SYMBOLS USED IN THIS DESIGN EXAMPLE

T-Z CURVE........................AXIAL DISPLACEMENT VS LOAD PLOT 7-13

Mp................................................................................. PLASTIC MOMENT 7-14
FS.............................................................................. FACTOR OF SAFETY 7-14
Kt........................................................... TORQUE TO CAPACITY RATIO 7-15

Purpose
This design example is intended to assist with the design of Self Support Structure foundations using

DESIGN EXAMPLES
Chance® RS3500.300 Helical Piles and Can Grillages where reveal is required. The basic principles used
in this example can be used for any Self Support Structure.
In this example, each leg of the Self Support Structure will be supported by a grillage on helical piles.
This type of structure will generally have tension, compression, and shear loads that will need to be
calculated or provided by the tower manufacturer. Generally all moment loads are transferred to the
structure by Tension/Compression force couples (One side has a tension load while the other side is
compressed).
After the loads for the structure have been determined, it is possible to design the piles.

Loads For This Example

• Compression: 130 kip
• Tension: 100 kip
• Shear:
• Transverse: 11 kip
• Longitudinal: 10 kip

Soils
• Layers
• 0-15ft: 500 psf clay (500 psf is the cohesion of the clay)
• 15-30ft: 1000 psf clay
• >30ft: 2000 psf clay
• Water Table: 10 ft below surface
• Required Reveal Height: 1 ft.

Page 7-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Pile Capacity:
The first step in the design is to calculate the estimated axial capacity of the pile. This is done by putting
the boring into Helicap®, selecting the product line you wish to use (RS3500.300 for Can style grillage),
and helix configuration. This value is generally the maximum capacity of the pile type you wish to use,
but can be lower if the soils are not very good. This value is used for the initial T-Z curve in the group
model. In this example with a 10/12/14/14/14/14, a 90 kip pile can be attained (See Figure 1).
DESIGN EXAMPLES

Figure 7 -6: Helicap Printout

Page 7-12 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
At this point, the data is input into Group®. Some of the inputs include: the soils, the loads (including
different load cases for tension/compression as well as different directions the loads can act), T-Z curve,
and the pile configuration/properties (Pile configuration for grillages can be found in the grillage section
under the products tab and pile properties/capacities can be found in the same section under the
section for the desired pile.
Generally the loads put into GROUP® are working loads. Because GROUP® is estimating lateral
deflection; the best way to get a factor of safety is to apply it to the Group results. Please consult the
Group® Manual for any questions about how to use Group®.
Here are the results of this analysis for these piles.

DESIGN EXAMPLES

Figure 7-7: Resultant Deflection, Moment, and Shear

Page 7-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 When looking at the GROUP® results, the important things to look for in Figure 2 are: Is the resultant
deflection greater than acceptable? Is the moment greater than 0.6 Mp? Generally with a Self Support
Structure, 1” lateral defection at working loads is acceptable and 0.6 Mp for resolved is 87 kip-in.
The minimum embedment for the helical piles (or minimum amount of pipe for the piles in Combo piles)
is where the resultant shear reaches and stays very close to 0 kip. In this case, it would be 14 ft. There
are some scenarios that can increase minimum embedment. If there is a soft layer of soil, the minimum
embedment can require bearing below that layer. It can also be used to ensure the last helix plate is a
minimum of 5 helix diameters below the surface.
DESIGN EXAMPLES

Figure 7 -8: GROUP® Results

From Figure 7-8, the important things to look for include, is the total stress greater than the yield stress
and is the required axial capacity smaller than half the capacity of the T-Z curve (for a FS=2). In this case
the maximum total stress is 48.3 ksi which is less than (50 ksi) and the axial load is 42.2 kip which is less
than 90/2=45.
At this point, if the axial capacity from the T-Z curve is considerably larger than double the required by
the model, the T-Z curve is adjusted to be closer and the helical configuration is also adjusted in the
Helicap model until the right capacity is found.

Page 7-14 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
With the final ultimate capacity known, the torque required for installation can be calculated. Equation
7-4 shows the equation for calculating installation torque.

Installation Torque (ft-lbs)=required Capacity(kip)*1000/kt Equation 7-4

• kt=7 for RS3500
• Required Capacity is 90 kip
• Installation torque: 1000*90/7=12,900 ft-lbs

Recommendation:
1. Install 4-RS3500.300 helical piles
a. Helix Configuration: 10/12/14/14/14/14
b. Installation Torque: 12,900 ft-lbs
c. Estimated Embedment: 50 ft.
d. Minimum embedment: 14 ft.

2. Assumptions

DESIGN EXAMPLES
a. Boring B-1 is representative of the site
1. Water table: 10 ft.
b. Loads given:
a. 130kip Comp
b. 100kip Tension
c. Shear:
1. Transverse 10kip
2. Longitudinal 10kip
c. Piles are installed at ground level
d. Pile Revea: 1 ft.
e. Torque to Capacity Ratio: 7:1
f. Fixed Head Condition
g. Axial FS: 2.0
i. Amount of Lateral deflection acceptable at working loads: 0.7"
3. Notes
a. May reach installation torque before reaching minimum embedment.
Adhere to minimum embedment
b. Maximum torque for RS3500.300 is 13,000 ft-lbs. Do not Overtorque!

Page 7-15 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 3
H-FRAME STRUCTURE DESIGN WITH
CONCRETE CAP AND MICROPILE DESIGN
SYMBOLS USED IN THIS DESIGN EXAMPLE

T-Z CURVE........................AXIAL DISPLACEMENT VS LOAD PLOT 7-17

Mp................................................................................. PLASTIC MOMENT 7-19
FS.............................................................................. FACTOR OF SAFETY 7-20
Kt........................................................... TORQUE TO CAPACITY RATIO 7-21

Purpose
DESIGN EXAMPLES

This design example is intended to assist with the design of H-Frame Structure foundations. This
example will show how to design using GROUP® and a concrete cap. A grillage can be used for an
H-frame structure, and an example of how to design for a grillage is given in Design Example 2
Each leg of the H-Frame Structure will be supported by a concrete pile cap. This type of structure
will generally have tension, compression, shear, and moment loads that will need to be calculated or
provided by the tower manufacturer
After the loads for the structure have been determined, it is possible to design the piles.
For this example the loading soil is as follows:

Loads
• Compression: 100 kip
• Tension: 80 kip
• Shear:
• Transverse: 9.5 kip
• Longitudinal: 1 kip
• Moment
• Longitudinal: 150 kip-ft

Soil Profile:
• Layers
• 0-10 ft: 28° Friction Angle Sand
• 10-30 ft: 30° Friction Angle Sand
• >30ft: 35° Friction Angle Sand
• Water Table: Surface (0 ft)

Page 7-16 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Pile Capacity:
The first step in the design is to look at the soil profile and estimate a maximum ultimate axial capacity
that can be attained. This is done by putting the boring into Helicap®, selecting the product line you wish
to use, and helix configuration. This value is generally the maximum capacity for the pile you wish to
use (the axial capacities of shafts can be found in the Drawings and Ratings section), but can be lower
if the soils are not very good. You will use this value for the initial T-Z curve in the group model. In this
example, we will use a SS175 pulldown pile with helical configuration 10/12/14/14. The estimated capacity
is 100 kip (See Figure 7-9).

DESIGN EXAMPLES

Figure 7-9: Helicap Printout

Page 7-17 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 There are a few options for consideration at this point in design. Are the piles going to have a fixed or
pinned end condition? Batter or no batter? Embed the pile cap or not? A fixed head condition will make
the foundation more rigid and result in smaller defections with lateral loads. However, it also results in
greater moments. Battered piles will also make a foundation more rigid and result in less deflection. This
results in the ability to uses smaller shafts to resist lateral loads, but also required an axial load to work.
It is acceptable to embed the pile cap, but there are many variables that have to be considered before
doing so. Can it be guaranteed that the cap will always have soil around it? Will the soil around it have
the same properties as has been assumed for the top layer/is the soil disturbed? These are just a few of
the items that need to be considered before GROUP®.
At this point, the data is input into Group®. Some of the inputs include: the soils, the loads (including
different load cases for tension/compression as well as different directions the loads can act), T-Z curve,
and the pile configuration/properties. The pile configuration is going to be made up of 2 sections. The
first is a cased pulldown pile (to resist moment) and the next will be an uncased pulldown pile. You
want the cut off between the two to be at the point where estimated moment in the pile is less than the
cracking moment of the uncased column.
Generally the loads put into GROUP® are working loads. Because GROUP® is estimating lateral
deflection; the best way to get a factor of safety is to apply it to the GROUP® results. Please consult the
GROUP® Manual for any questions about how to use GROUP®.
DESIGN EXAMPLES

With the data in GROUP®, the design becomes an iterative process to come up with a pile configuration
that works well. If the piles have too much moment, they can be spaced further apart or battered at a
different angle to relieve it. If the piles have too much axial loading, spacing a little closer together can
fix that issue. Sometimes, the loads will just require larger diameter pipe, greater diameter column, or
more piles to have an acceptable model. If the axial capacity from the T-Z curve is considerably larger
than double the required by the model, the T-Z curve can be adjusted down to get a more cost effective
pile. In this case the T-Z curve was adjusted from 100 to 85 kips.
Here are the results of the analysis with the T-Z curve capacity of 85 kips on 4 piles battered 10 degrees
from vertical, away from the center, and spaced on the corners of a 5’ square.

Page 7-18 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES
Figure 7-10: Resultant Deflection, Moment, and Shear

When looking at the GROUP® results, the important things to look for in Figure 7-10 are: Is the resultant
deflection greater than acceptable and is the moment greater than allowable. For a pulldown pile, the
acceptable moment is either 0.6 Mp of the casing or the cracking moment. In this case, the cracking
moment is 10.6 kip-in.
The minimum depth of grout for the piles is where the resultant shear becomes very close to 0 (less
than 50 lbs). This is the location where the square shaft no longer requires the grout column (assuming
the soil is greater than 4 blow materials). The minimum depth of the grout column in this example is
16 ft. The minimum depth of casing is the deepest depth at which the resultant moment is equal to the
cracking moment of the uncased shaft. In this case the minimum cased depth is 14 ft.

Page 7-19 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES

Figure 7 -11: GROUP® Results

From Figure 7-11, the important thing to look for is that the axial capacity of the pile (from the T-Z curve)
is greater than or equal to 2 times the axial reactions (for an axial FS of 2.0). In this case the 85 kips
from the T-Z curve is greater than 40*2= 80 kips.
Since the T-Z curve was changed during design, the Helicap® run needs to be run again to get an 85 kip
pile. Here are the results.

Page 7-20 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Figure 7-9: Helicap Final Run DESIGN EXAMPLES
With a final ultimate capacity known, it is time to determine the installation requirements. With the helix
configuration being a 10/12/14/14, the length of the lead is 11 ft. Therefore the grout will start 11 ft from
the start of the pile. From the Helicap® report, it is known that in the 28 ft length, 6.8 kips of ultimate
friction were developed a the estimated friction bearing capacity per foot is .242 kip/ft. Therefore, for
every foot the pile is longer than 11 ft, it will require 0.242 kips less capacity per foot. So for example
at 39 ft, it will only require 78.2 kip of bearing capacity. Being as torque to capacity ration Kt is 10:1,
therefore, only 7,900 ft-lbs of torque is required instead of the 8,500 had friction not been included. With
this known, it is possible to plot the required torque on a chart vs. depth as seen in Figure 7-13.

Page 7-21 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES

Figure 7 -13: Torque vs. Required Length

You will also want to include a pile layout for your design to make it a little less confusing. A simple pile
layout for this design is included in Figure 7-14.

Page 7-22 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES
Figure 7 -14: Pile Layout

Recommendation:
1. Install a SS175 Helical Pulldown Micropile
a. 6” Grout Column
b. Case first 12 ft with minimum 6” Nominal Schedule 40 pipe per ASTM A500 GRD B
c. Helix Configuration: 10/12/14/14
d. Installation torque and length per attached installation torque vs required pile length plot Figure
7-13
e. Locate piles per attached Pile Layout (Figure 7-14)
f. Estimated Embedment: 40 ft
g. Minimum embedment: 27 ft (16+11)

Page 7-23 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 2. Assumptions
a. Boring is representative of the site
1. Water table depth: 0 ft.
b. Loads given:
i. 10kip Comp
ii. 80kip Tension
iii. Shear
1. Transverse: 9.5kip
2. Longitudinal 4kip
iv. Moment:
1. Longitudinal: 150kip ft.
c. Piles are installed at ground level
d. Torque to Capacity Ratio: 10:1
d. Head Condition: Fixed
DESIGN EXAMPLES

e. Axial FS: 2.0

f. Amount of Lateral deflection acceptable at working loads: 0.2

3. Notes
i. May reach installation torque before reaching minimum embedment. Adhere to minimum
embedment requirements
ii. Ensure final torque is greater than required installation torque at given depth
iii. Maximum torque for SS175 is 10,500 ft-lbs. Do not Overtorque! (Torque capacities can be
found in the Drawings and Ratings section)

Page 7-24 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 4
MONOPOLE DESIGN WITHOUT GROUP
SYMBOLS USED IN THIS DESIGN EXAMPLE

Mp................................................................................. PLASTIC MOMENT 7-30

FS.............................................................................. FACTOR OF SAFETY 7-28
Kt........................................................... TORQUE TO CAPACITY RATIO 7-31

Purpose
This design example is intended to assist with the design of small Monopole Structures. It will go
through the basic design using hand calculations/L-pile. GROUP® can also be used for this eample.
The leg of the Monopole Structure will be supported by a concrete pile cap. This type of structure will

DESIGN EXAMPLES
generally have compression, shear, and moment loads that will need to be calculated or provided by the
tower manufacturer
After the loads for the structure have been determined, it is possible to design the piles.
For this example the loading is as follows:

Loads
• Compression:
• 50 kip
• Shear:
• 40 kip
• Moment
• 200 ft-kip

Soil Profile:
• Layers
• 0-15 ft: 1000 psf clay
• 15-30 ft: 1500 psf clay
• >30ft: 2000 psf clay
• Water Table: Surface (0 ft)

Pile Capacity:
The first step in the design is to look at the soil profile and estimate a maximum ultimate axial capacity
that can be attained. This is done by putting the boring into Helicap® and selecting the product line and
helix configuration you wish to use. This value is generally the maximum capacity for the pile you wish to
use (the axial capacities of shafts can be found in the Drawings and Ratings section), but can be lower if
the soils are not very good.

Page 7-25 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES

Figure 7-15: Helicap Printout

As can be seen from the Helicap® model, 99 kip can be attained using an RS4500.337.
L-pile/Hand Calc Method
For this analysis, the cap is going to be considered fully rigid. The first step is to determine a pile
configuration and spacing, then ensure the load to the piles is not greater than allowable. In this case,
the wanted configuration includes 9 piles (all with 100 kip capacity) and located on a 3x3 grid. A sample
pile layout can be seen in Figure 7-16.

Page 7-26 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES
Figure 7-16: Anticipated Pile Layout

Because this example assumes the load can act in any direction, it is necessary to determine the worst
case loading for this pile layout. In this case, two scenarios will be evaluated. In one case, the load acts
along the lines in the grid. In the second case, it acts at a 45 to the first case. The two layouts can be
seen in Figures 7-17.

Page 7-27 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES

Figure 7-17 GROUP® Results

With the two layouts determined, it is now possible to analyze and ensure that the piles have the
required capacity with the intended spacing. Because the pile cap will not be truly rigid and the fact
that the piles can continue to deflect and carry their ultimate capacities, beyond the location they reach
ultimate capacity, it will be assumed the capacity of each pile is 100 kips ultimate (50 kip working). To
ensure the FS=2 kip will be used as the capacity of each of the 9 piles.
Because there are 3 piles that will not be taking any axial load from the moment in both cases, it is
assumed that that axial load will be transferred through these piles and not through the other piles in the
concrete cap.
It is now possible to calculate the amount of moment that can be resisted by the layout. This can be
conducted by using a summation of moments about the center of the cap (location where load is
applied).

Page 7-28 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Moment=Load*perpindicular distance Equation 7-5
Along the grid, the summation of moments would look like this (positive is resistance and
negative is load):

∑Moments=7.25ft*50kip*3piles+7.25ft*50kip*3piles-2000kip ft=175 kip ft

Therefore, the piles can resist an additional 175 kip-ft of moment with a FS of 2.0.
For the corner to corner analysis, the summation of moments looks like this:

∑Moments=(10.3ft*50kip*1 pile+5.1ft*50kip*2pile)*2-2000kip ft=50 kip ft

Therefore, the piles can resist the moment and axial loads in both directions.

With the axial design completed, it is time to ensure the piles can take the shear loads. It is assumed that
the piles will have a pinned pile head condition and the shear load is distributed to each pile evenly.

DESIGN EXAMPLES
Shear Shear Force 40 kip
= = = 4.44 kip/pile
Pile Number of Piles 9 Piles

This shear load as well as an axial load of 50 kips are input into L-pile along with the pile properties for
R345001337 (found in the Drawings and Ratings section of this manual) and soil properties. See the
Design Methodology section for assistance as well as the L-pile manual for assistance in using L-pile. The
resulting deflection curve is included in Figure 7-18 and the moment curve is included in Figure 7-19.

Figure 7-18: Lateral Deflection vs Depth

Page 7-29 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES

Figure 7-19: Bending Moment vs Depth

These results show that the piles will be able to carry the required shear capacity with 0.9” deflection
and 114 kip-in of moment. This deflection is generally acceptable for transmission structures and the
moment is less than the 0.6 Mp used in standard design.
Recommendation:
1. Install 9-RS4500.337 Helical Piles
a. Helix Configuration: 10/12/14/14/14/14
b. Installation torque: 16,700 ft-lbs
c. Locate piles per attached Pile Layout (Figure 2)
d. Estimated Embedment: 50 ft
e. Minimum embedment: 20 ft

Page 7-30 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
2. Assumptions
a. Boring is representative of the location
i. Water table depth is deeper than 50 ft
b. Given loads are working (moment and shear can act in any direction)
i. Compression: 50 kip
ii. Moment: 2000 kip-ft
iii. Shear: 40 kip
c. Piles are installed at ground level
d. Torque to Capacity Ratio for RS4500 is 6:1
e. Pinned Head Condition
f. Axial FS=2.0
g. 1” of Lateral deflection acceptable at working loads

3. Notes

DESIGN EXAMPLES
a. May reach installation torque before reaching minimum embedment. Adhere to minimum
embedment requirement
i. Ensure final torque is greater than installation torque
b. Maximum torque for RS4500.337 is 21,000 ft-lbs. Do not overtorque!

Page 7-31 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 5
GUYED TRANSMISSION STRUCTURE DESIGN
SYMBOLS USED IN THIS DESIGN EXAMPLE

Mp................................................................................. PLASTIC MOMENT 7-34

FS.............................................................................. FACTOR OF SAFETY 7-34
Kt........................................................... TORQUE TO CAPACITY RATIO 7-35

Purpose
This design example is intended to assist with the design of Guyed Transmission Structure foundation.
This example will show how to design using L-pile® and a pinned head condition grillage. This type of
structure will generally have tension, compression, and shear loads that will need to be calculated or
provided by the tower manufacturer.
DESIGN EXAMPLES

After the loads for the structure have been determined, it is possible to design the piles.
For this example the working loading and soil profile is as follows:

Loads
• Center Base
• Compression: 100 kip
• Shear:
• 1 kip
• Guyes
• 30 kip

Soil Profile:
• Layers
• 0-10 ft: 200 psf clay
• 10-30 ft: 1000 psf clay
• >30ft: 2000 psf clay
• Water Table: Surface (0 ft)

Pile Capacity:
The first step in the design is to determine the pipe shaft diameter or Micropile required to resist the
lateral load. To do this, the pile properties, soil properties, and loads are put into L-pile. The pipe
properties can be calculated for all pipe products with the information found in the Drawings and
Ratings section of this manual. Generally working loads will be input into L-pile so that failure criteria of x
lateral deflection at working loads can be used. In this example, 2R78625, 188 Pipe Piles will be used. The
results are plotted in Figure 7-20 and Figure 7-21.

Page 7-32 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES
Figure 7-20: Lateral Deflection vs Depth

Figure 7-21: Lateral Deflection vs Depth

Page 7-33 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 When looking at L-pile results, the goal is to have the deflection below what is allowable for the design
and the moment less than 0.6Mp. These results show that 2-RS8625.188 wall pipes will carry the lateral
load with an estimated 0.07” deflection and 20 kip-in of moment.
With the intended pipe shaft determined, Helicap® is now used to get a helix configuration and estimated
installation depth for both the center piles as well as the guy anchors. Figure 3 is the Helicap® report for
the center piles.
DESIGN EXAMPLES

Figure 7-22: RS8625.188 Helicap® Report

For the guy anchors, with the ultimate capacity known (FS*working), it is possible to design the anchor
using Helicap®. See Figure 7-23 for results.

Page 7-34 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLES
Figure 7-23: Guy Piles Helicap® Report

With these results, it is possible to calculate the required installation torques for the piles. For an 8”
diameter pipe, the Kt is 4:1 and for SS150, Kt is 10:1. To calculate required torque, equation:

Installation Torque (ft-lbs)=required Capacity(kip)*1000/Kt Equation 7-6

The required installation torque for the RS8625 piles is 25,000 ft-lbs and for the guy anchors is 6,000
ft-lbs.

Page 7-35 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Recommendation:
1. Center Piles
a. Install 2-RS8625.188
i. Minimum spacing is 48” (6*largest helix dia)
ii. Installation Torque=25,000 ft-lbs
iii. Estimated embedment=40 ft
iv. Minimum embedment=15 ft

2. Guy Anchors
a. Install SS150 Helical Anchors
i. Minimum effective installation torque: 6,000 ft-lbs
ii. Estimated Embedement=55 ft
iii. Batter piles within ±5° of guy wires
DESIGN EXAMPLES

2. Assumptions
i. Boring is representative of the location
1. Water table deeper than 40 ft
ii. Loads given are working loads
1. Center Base
a. Compression: 100 kip
b. Shear: 1 kip
2. Guyes
a. 30 kip
iii. Piles are installed at ground level
iv. Torque to Capacity Ratio:
1. RS8625 is 4:1
2. SS150 is 10:1
v. RS8625 piles have pinned head condition
vi. Require an axial factor of safety of 2.0
vii. ½” of lateral deflection acceptable at working loads

3. Notes
a. May reach installation torque before reaching minimum embedment. Adhere to minimum
embedment
i. Ensure final torque is greater than required installation torque at given depth
b. Maximum torque for RS8625.188 is 50,000 ft-lbs. Do not overtorque
c. Maximum torque for SS150 is 7,000 ft-lbs. Do not overtorque

Page 7-36 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 6
HELICAL PILE FOUNDATION FOR NEW SUBSTATION CONSTRUCTION
SYMBOLS USED IN THIS DESIGN EXAMPLE

P..................................................................ALLOWABLE DESIGN LOAD 7-38

FS.............................................................................. FACTOR OF SAFETY 7-38
Qt....................................................................ULTIMATE PILE CAPACITY 7-38
Kt........................................................... TORQUE TO CAPACITY RATIO 7-38
A...........................................................................AREA OF HELIX PLATE 7-38
C..................................................................................COHESION OF SOIL 7-38
Nc.............................................................BEARING CAPACITY FACTOR 7-38

DESIGN EXAMPLES
T........................................................................................................ TORQUE 7-38
N................................................................................. SPT BLOW COUNTS 7-38

Purpose
This design example is intended to assist with the design of new construction substation structures that
require deep piles beneath a concrete cap for compression capacity. This example will show how to
calculate the bearing capacity of four piles beneath a 10 feet square concrete cap holding an oil filled
transformer.
After the loads for the structure have been determined, it is possible to design the piles.
For this example the working load is as follows:
• Compression: 56 kip (Load includes weight of concrete cap)
• Shear loads are assumed to be taken by up by passive pressure and fiction along the bottom of
the concrete cap.

Figure 7-24 Figure 7-25

Page 7-37 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Soil Profile:

Figure 7-26
DESIGN EXAMPLES

CHANCE® Helical Pile Selection

RS2875.203 with 8-10-12 helix configuration

Ultimate Pile Capacity Equation 7-7

• Qt = (A8 + A10 + A12) c Nc
A8, A10, A12 = Projected area of helical plates.
A8 = 0.34ft2 A10 = 0.53 ft2 A12 = 0.77 ft2
Nc = Bearing Capacity Factor = 9.0
C = N/8 = 16/8 = 2 ksf
• Qt = (1.64ft2)(2,000 psf) ( 9.0)
• Qt = 29,520 lb (installed depth is over 20 ft)
Check Qt
• Conduct Field Load Test (if required per specifications)
Estimate installation Torque Equation 7-8
P = 56,000lb/4 Piles = 14,000 lb
T = (P X FS)/Kt = (14,000 lb x 2)/9 = 3,150 ft-lb
Kt = empirical torque factor (default value =9 for the RS2875 series)
The rated installation torque of the RS2875.203 series is 5500 ft-lb, which greater than the required
estimated installation torque of 3,150 ft-lb. (OK)
NOTE: If during installation T = 3,150 ft-lb is not achieved then two options are available: (1) add piles if
spacing allows, or (2) change helix configuration to a larger combination, i.e, (10-12-14) (3) Install Deeper
Factor of Safety Equation 7-9
• Theoretical Ultimate Capacity
FS = (Qt/P) = 29,520/14,000 = 2.1 (OK)
• Torque Correlation:
FS = (T x Kt)/P
FS = (3,150 x 9)/14,000 = 2.03 (OK)

Page 7-38 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 7
TYPE RS HELICAL PILES FOR SUBSTATION LATERAL SUPPORT
SYMBOLS USED IN THIS DESIGN EXAMPLE

C............................................................... COHESION FACTOR OF SOIL 7-4O

Ps.............................................APPLIED HORIZONTAL SHEAR LOAD 7-4O
Cu............................................................................... COHESION OF CLAY 7-4O
D............................................................... DIAMETER OF FOUNDATION 7-4O
L................................................ MINIMUM LENGTH OF FOUNDATION 7-4O
e........................................................................................... ECCENTRICITY 7-4O
F.......................................................................................BENDING STRESS 7-4O

DESIGN EXAMPLES
MPOSmAX.............................................. MAXIMUM BENDING MOMENT 7-4O
FS.............................................................................. FACTOR OF SAFETY 7-4O

Purpose
This design example is intended to assist with the design of new construction substation structures that
requires a low axial load with high shear load on a single pile. This example will show how to calculate
the lateral capacity of a single pile using the Broms’ Method for a 345KV medium switch support.
After the loads for the structure have been determined, it is possible to design the piles.

Page 7-39 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 For this example the working loading is as follows:

Loads
• Shear: 2300 lbs
• Shear applied to switch 10 feet above grade.

Soil Profile:
• Soil is a clay with a cohesion of 0.5 ksf.

Solution

P = Applied horizontal shear load: Use 2300 lbs. Include a Factor of Safety of 2 in the
calculations, thus doubling the horizontal shear load; P = 2 x 2300 lbs = 4600 lbs
Cu = Cohesion of Clay: 500 psf
D = Diameter of foundation: Use D = 10.75” (10” nominal pipe size)
e = Eccentricity; distance above grad to resolve load: Given e = 10 ft.
DESIGN EXAMPLES

L = Minimum Length of foundation based on above criteria.

F = P/ [9 (Cu) D] Equation 7-11

= 4600 lbs/ [9 (500 psf) (10.75in/12)]
= 1.141 ft
MPOSmAX = P (e +1.5D + 0.5F)
= 4600 lbs [10 + 1.5(10.75 in /12) + 0.5 (1.141 ft)]
= 54,806 ft-lbs
MPOS mAX = 2.25 D x g2 x Cu
54,806 ft-lb = 2.25 (10.75 in/12) g2 (500 psf)
g2 = 54.38
g = 7.38 ft
L = 1.5D + F + G
= 1.5 (10.75 in/12) + 1.141ft + 7.38ft
= 9.87 FT

Page 7-40 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Summary
The 10” Nominal Round Shaft helical pile should be at least 10’-0 long to resist the 2300 lb lateral load
applied 10 feet above grade

DESIGN EXAMPLES
Figure 7-26

Page 7-41 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 DESIGN EXAMPLE 8
HELICAL PILE FOUNDATION FOR REMEDIATION
OF SUBSTATION BUS SUPPORT
SYMBOLS USED IN THIS DESIGN EXAMPLE

ɸ.........................................................ANGLE OF INTERNAL FRICTION 7-43

γ............................................................................ UNIT WEIGHT OF SOIL 7-43
N................................................................................. SPT BLOW COUNTS 7-43
PC.........................ALLOWABLE DESIGN LOAD IN COMPRESSION 7-45
Pt....................................... ALLOWABLE DESIGN LOAD IN TENSION 7-45
FS.............................................................................. FACTOR OF SAFETY 7-45
DESIGN EXAMPLES

Qt....................................................................ULTIMATE PILE CAPACITY 7-45

Kt........................................................... TORQUE TO CAPACITY RATIO 7-45
A...........................................................................AREA OF HELIX PLATE 7-45
Nc.............................................................BEARING CAPACITY FACTOR 7-45
T......................................................................................................... TORQUE 7-45

Purpose
This design example is intended to assist with the remediation design of a substation bus support that
has settled. The plan of repair is to replace the central drilled concrete shaft beneath each leg with two
type RS (Round Shaft) piles with a steel grade beam. The central concrete shaft will be demolioshed as
well during pile install. This example will show how to calculate the axial capacity of the type RS piles
and the lateral capacity of the type RS pile, using L-pile.
After the loads for the structure have been determined, it is possible to design the piles.

Page 7-42 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
For this example the loading is as follows:

Loads
• Compression: 5,000 lbs
• Tension: 2,000 lbs
• Shear Long Direction: 1,200 lbs
• Shear Trans Direction: 1, 200 lbs
• Moment About Long Axis: 10,000 ft-lbs
• Moment About Trans Axis: 0 ft-lbs

DESIGN EXAMPLES
Figure 7-27

Soil Profile:

Soil Description Depth ft. SPT -N Blows/ft

Silty Sand Loose

γ=90lb/ft3 0 4
ɸ=27°

Sand
γ=120lb/ft3
5 10
Φ=30°

Note: Water Table = 0 FT

Figure 7-28

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 CHANCE® Helical Pile Selection
RS6625.280 with a single 16” diameter helix

Lateral Capacity Analysis using L-Pile

Moment load about the longitudinal axis is assumed to be transferred to the piles in tension and
compression. The piles will require passive resistance of the resultant shear load of
(1,2002 + 1,2002)1/2= 1,698 lbs with a maximum deflection under this load of 1/2” that is typical
for substation structures. L-Pile yields the following output for this shaft that is within the design
parameters and requires a minimum embedment of 14 feet.
DESIGN EXAMPLES

Figure 7-28

Page 7-44 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Ultimate Pile Capacity
• Pc= Compression/2 piles + 10,000 ft-lbs/4 ft spacing
= (5000 lbs / 2) + 2,500 lbs
= 5,000 lbs
• Pt= Tension/2 piles + 10,000 ft-lbs/4 ft spacing
= (2000 lbs / 2) + 2,500 lbs
= 3,500 lbs
• Qt = (A16) qh Nq
A14 = Projected area of helical plates.
Compression will have full helix area = A16C = 1.281 ft2
Tension will area will be full helix area minus pipe shaft = A16T = 0.972 ft2
Nq = Bearing Capacity Factor related to ɸ of residual soil (30°) = 0.5 (12 x Φ) Φ/54 = 13
• qh = γ’ x Dh (Effective unit weight times depth of helix below ground line, ft)
= (90 pcf – 62.4pcf) (5ft) + (120 pcf – 62.4pcf) (8.5ft)

DESIGN EXAMPLES
= 627 psf
• QtC = (1.281 ft2) (627 psf) (13) = 10,441 lbs (Ultimate Compression Capacity)
• QtT = (0.972 ft2) (627 psf) (13) = 7,922 lbs (Ultimate Tension Capacity)

Check Qt
• Conduct Field Load Test (if required per specifications)

Estimate installation Torque

P = 5000 lbs
T = (P X FS)/Kt = (5,000 lb x 2)/5 = 2,000 ft-lb
Kt = empirical torque factor (default value =5 for the RS6625 series)

NOTE: If during installation T = 2,000 ft-lb is not achieved then two options are available: (1) install piles
deeper, or (2) change helix configuration to a larger combination, i.e, (16-18)

Factor of Safety
• Theoretical Ultimate Bearing Capacity
FS = (QtC/P) = 10,441/ 5,000 = 2.09 (OK Compression)
FS = (QtT/P) = 7,922 / 3,500 = 2.26 (OK Tension)

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 DESIGN EXAMPLE 9
INSTANT FOUNDATIONS® for STREET LIGHT SUPPORTS
SYMBOLS USED IN THIS DESIGN EXAMPLE

SLF.......................................................... STREET LIGHT FOUNDATION 7-46

DL........................................................................DEAD OR DOWN LOAD 7-47
V..................................... HORIZONTAL OR LATERAL SHEAR LOAD 7-47
M........................................................................................MOMENT LOADS 7-47
AASHTO................................ AMERICAN ASSOCIATION OF STATE 7-47
..............................HIGHWAY AND TRANSPORTATION OFFICIALS
L...................................................................................REQUIRED LENGTH 7-48
DESIGN EXAMPLES

C..................................................................................COHESION OF SOIL 7-48

FS.............................................................................. FACTOR OF SAFETY 7-48
VF..................................................APPLIED SHEAR AT GROUNDLINE 7-48
.......................................................... INCLUDING FACTOR OF SAFETY
VM............................................. APPLIED MOMENT AT GROUNDLINE 7-48
.......................................................... INCLUDING FACTOR OF SAFETY
D............................................................... DIAMETER OF FOUNDATION 7-48
q............................................................................. BROMS’ COEFFICIENT 7-48
MMAX................. MAXIMUM MOMENT APPLIED TO FOUNDATION 7-48
φ.........................................................INTERNAL ANGLE OF FRICTION 7-49
γ............................................................................ UNIT WEIGHT OF SOIL 7-49
KP...................................PASSIVE EARTH PRESSURE COEFFICIENT 7-49

Purpose
This design example provides example solutions to aid in the selection of appropriate CHANCE®Instant
Foundation® products for different job parameters.

SLF Loads
The resulting pole loads to be resisted by a street light foundation (SLF) are dead or vertical down loads
(DL), horizontal, lateral or shear loads (V) due to wind on the pole and luminaire (light fixture), and over-
turning moment loads (M) resulting from the tendency to bend at or near the ground line as the wind
causes the pole to displace and the foundation restrains the pole base at one location (see Figure 7-30).

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 The DL for an SLF application is so small that a foun-
wp = Wind Pressure SLF REACTIONS dation sized to resist V and M will typically be much
EPAlf = Effective Projected Area of a Light Vlf = [EPAlf x wp] more than adequate to resist DL. Therefore, DL will
Fixture Vp = [EPAp x wp] not control the SLF design and will not be consid-
EPAp = Effective Projected Area of a Light Pole V = Vlf +Vp ered here. If DL is large enough to be of concern for
Hlf = Moment Arm to EPAlf Centroid M = [Vlf x Hlf] + [Vp x Hp] an application where an SLF will be used, it may be
evaluated based on bearing capacity equations ap-
plied to the soil around the helical bearing plate and
EPAlf friction along the shaft. These evaluations are beyond
the scope of this design example, which will only deal
with SLF applications.
Since SLF products are used as lighting foundations
along public highways, it is appropriate to men-
tion the American Association of State Highway
and Transportation Officials (AASHTO) publication
Standard Specifications for Structural Support for
Highway Signs, Luminaires and Traffic Signals. This
document is often taken as the controlling specifi-

DESIGN EXAMPLES
Hlf cation for jobs using SLF’s and will be referenced
EPAp
throughout this discussion.
DL SLF Selection
The SLF selection process is a trial and error proce-
dure that may require more than one iteration. First,
Hp select an SLF diameter based on the applied bending
moment (M) that must be resisted. That is, ensure
that the applied moment is less that the allowable
moment on the shaft. Determining the allowable mo-
M
ment requires a structural analysis of the pipe shaft
section capacities (often based on a reduced cross
V
section through cable ways, bolt slots, base plate
size, welds, etc). This effort should be familiar to en-
gineers engaged in design work, so a sample of this
process will not be given here.
Pole Load Diagram The design or selection of a foundation size to resist
Figure 7-30 light pole loads in a given soil may be determined
by various methods. Numerical methods using finite
element and finite difference techniques may be used
but have proven to be somewhat sophisticated for
the rather simple SLF application. The Fourth Edition
of the AASHTO specification lists a number of pre-
liminary design methods that can be employed in the
design process. Among those listed and discussed
are the methods developed by Bengt B. Broms
for embedment lengths in cohesive and cohesion-
less soils and a graphical method dealing with the
embedment of lightly loaded poles and posts. The
Broms Method will be used for this design example
as experience has shown these methods to both use-
able and appropriate. Calculations are provided for
both cohesive soil (clay) and cohesionless soil (sand).
Foundation in Cohesive Soil
Figure 7-31

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 Cohesive Soil (See Figure 7-31)
Assumed values:
• Applied shear load at the groundline (V) = 460 lbs.
• Applied moment at the groundline (M) = 8600 ft-lbs.
• Foundation diameter is 6” nominal Schedule 40. Use 6.625” as the actual pipe size in
calculations. Cableway openings are 2.5” wide by 12” high. The allowable moment capacity of this
foundation shaft size and cableway opening is 10,860 ft-lbs.
• The required length (L) will be determined using the Broms method.
• Cohesion (c) = 1000 psf.
• Factor of Safety = 2.

VF = V (FS) Equation 7-12

= 460 (2)
= 920 lbs
DESIGN EXAMPLES

VM = M (FS) Equation 7-13

= 8600 (2)
= 17,200 ft-lbs

L = 1.5D+q [1+{ 2 + (4H+6D)/q} 0.5] Equation 7-14

1.5 (6.625/12) + 0.185157 x [1 + { 2+ ( 4 x 18.69565 + 6
=
x (6.625/12)) / (0.185157)} 0.5]
= 4.82 ft
D = Diameter of foundation = 6.625 inches
where: q = VF/9cD = 920 / (9 x 1000 x 6.625/12) = 0.185157ft
c = Shear strength of cohesive soil = 1000 psf
Moment / Shear = M/V = VM / VF = 17200 ft-lbs / 920
H =
lbs = 18.69565 ft
Calculated Foundation Length to Provide a SF of 2
L =
Against Soil Failure.
The length required to provide a Factor of Safety of 2 against soil failure is 4.82 ft. Since SLF lengths are
provided in even foot lengths, use L = 5 ft. For the required embedment length, the maximum moment in
the shaft is:

MMAX = V ( H + 1.5D + 0.5q) Equation 7-15

= 460 (18.69565 + (1.5 x 6.625/12) + (0.5 x 0.185157)
= 9023.5 ft-lbs
Maximum moment can be compared with the allowable moment capacity of the foundation shaft to
determine adequacy. For this example the allowable moment in the 6” pipe shaft is given as 10,860 ft-lbs,
which is greater than the applied moment. Therefore, the 6” diameter by 5’ long SLF is adequate for the
applied loads in the clay soil.

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 Cohesionless Soil (See Figure 7-32)
Assumed values:
• Applied shear load at the groundline (V) = 460 lbs.
• Applied moment at the groundline (M) = 8600 ft lbs.
• Foundation diameter is 6” nominal Schedule 40.
Use 6.625” as the actual pipe size in calculations.
Cableway openings are 2.5” wide by 12” high. The
allowable moment capacity of this foundation shaft
size and cableway opening is 10,860 ft-lbs.
• The required length (L) will be determined using the
Broms method.
• ф = 30°
Foundation in Cohesionless Soil • γ = 100 lbs/ft3
Figure 7-32
• Factor of Safety = 2.

= V (FS) Equation 7-16

DESIGN EXAMPLES
VF = 460 (2)
= 920 lbs

= M (FS) Equation 7-17

VM = 8600 (2)
= 17,200 ft-lbs
Broms equation for cohesionless soil requires a trial and error solution. For the trial and error solution, start by
assuming the foundation diameter (D) is 6.625” and the length (L) is 6 feet:

0 ≤ L3 - ( 2VFL / KPgD ) – ( 2VM / KPgD ) Equation 7-18

63 - [ 2 x 920 x 6) / (3 x 100 {6.625/12})] - [(2 x 17200) /
=
(3 x 100 x {6.625/12})]
where: = - 58.35
0 > - 58.35
KP = tan2 (45 + j/2 ) = 3.0
g = Effective unit weight of soil = 100 lbs/ft3
The 6 foot length is too short so we will try a 7 foot length and repeat the calculation:

0 = 73 - [2 x 920 x 7) / (3 x 100 {6.625/12})] - [(2 x 17200) / (3 x 100 x {6.625/12})]

= 57.53
0 < 57.53
A 7 foot long SLF will be adequate. The maximum moment in the foundation shaft can be determined with the
following equation:

MMAX = V ( H + 0.54 x ( V / gDKP ) 0.5 ) Equation 7-19

= 460 (18.69565 + 0.54 x ( 460/100 x (6.625/12) x 3) 0.5)
= 9013.968 ft-lbs
This is less than the allowable moment capacity of 10,860 ft-lbs, therefore a 6” diameter by 7’ long SLF is
adequate for the applied load in the sandy soil.

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 DESIGN EXAMPLE 10
FOUNDATION EARTH PRESSURE RESISTANCE
SYMBOLS USED IN THIS DESIGN EXAMPLE

PCF.............................................................. POUNDS PER CUBIC FOOT 7-50

KA....................................ACTIVE EARTH PRESSURE COEFFICIENT 7-50
KP...................................PASSIVE EARTH PRESSURE COEFFICIENT 7-50
PA............................................................................................ACTIVE LOAD 7-51
PP...........................................................................................PASSIVE LOAD 7-54
DESIGN EXAMPLES

Project
A CHANCE® helical type SS5 1-1/2” square shaft
helical anchor is proposed as part of a pier and
beam foundation for a residential structure (see
Figure 8-31). The top of the helical anchor is
fixed in a concrete grade beam that extends 4’-0
below grade. The surface soils are loose sands.
Determine the lateral capacity of the grade beam
using the Rankine earth pressure method.

Assumptions
• The lateral capacity of the 1-1/2” square shaft
helical anchor is limited based on shaft size. It
is generally not assigned any contribution to
the lateral capacity of a foundation
• The effective length of the grade beam for
lateral resistance is 25’-0
• Assume a unit weight of 95 pcf
• The water table is well below the bottom of
the grade beam
• There are no surcharge loads
Earth Pressure on a Grade Beam • From Table 8-9, Ka = 0.2, Kp = 3
Figure 7-33

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Solution

Pa = 0.5KagH2 Equation 7-20

= 0.5 x 0.2 x 95 x 42
= 152 lb/ft
Pp = 0.5KpgH2
= 0.5 x 3 x 95 x 42
= 2280 lb/ft
Pp - Pa = 2280 - 152
= 2128 lb/ft
Total lateral
= 2128 x 25'-0 = 53,200 lbs
resistance

NOTE: In this example, more than 1” of movement will probably be required to fully mobilize the total lateral
resistance. Partial mobilization requires less deflection.

DESIGN EXAMPLES
COEFFICIENTS OF EARTH PRESSURE (DAS, 1987)
SOIL K0' DRAINED K0' TOTAL Ka' TOTAL Kp' TOTAL
Clay, soft 1 0.6 1 1 1
Clay, hard 1 0.5 0.8 1 1
Sand, loose 0.6 0.53 0.2 3

Sand, dense 0.4 0.35 0.3 4.6

Note:
1Assume saturated clays.

Figure 7-34

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 DESIGN EXAMPLE 11
BUCKLING EXAMPLE USING THE DAVISSON METHOD
SYMBOLS USED IN THIS DESIGN EXAMPLE

kh.............................................................. Empirical Torque Factor for Helix 7-52

Ucr..............................................................................................Critical Capacity 7-52
R..............................................................................................................Resistance 7-53
Imax..................................................................... Maximum Moment of Inertia 7-53
Pcr............................................................................................... Critical Pressure 7-53
Ep....................................................................................... Modulus of Elasticity 7-53
Ip.............................................................................................. Moment of Inertia 7-53
DESIGN EXAMPLES

D....................................................................................................Shaft Diameter 7-53

kip.......................................................................................................... Kilopound 7-53

Project
A three-helix CHANCE® helical type SS150 1-1/2” square shaft helical pile is to be installed into the soil
profile as shown in Figure 8-33. The top three feet is uncontrolled fill and is assumed to be soft clay. The
majority of the shaft length (12 feet) is confined by soft clay with a kh = 15 pci. The helix plates will be
located in stiff clay below 15 feet. The buckling model assumes a pinned-pinned end condition for the
helical pile head and tip. Determine the critical buckling load using the Davisson method.

Assumptions
• kh is constant, i.e., it does not vary with depth.
This is a conservative assumption because kh
usually varies with depth, and in most cases
increases with depth.
• Pinned-pinned end conditions are assumed.
In reality, end conditions are more nearly fixed
than pinned, thus the results are generally
conservative.
• From Figure 7-35, Ucr ≈ 2

Poulos and Davis (1980)

Figure 7-32

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R = 4√(30 x 106 x 0.396) / (15 x 1.5) = 26.96 Equation 7-21
Imax = (15 x 12) / 26.96
= 6.7
Pcr = (2 x 30 x 106 x 0.396) / 26.962
= 32.69 kips

CHANCE® HELICAL TYPE SS150 SQUARE SHAFT

FOUNDATIONS PHYSICAL PROPERTIES, TABLE 7-1
MODULUS of ELASTICITY (Ep) MOMENT of INERTIA (Ip) SHAFT DIAMETER (D)
30 x 106 psi 0.396 in4 1.5 in

DESIGN EXAMPLES

Foundation Details
Figure 7-36

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 DESIGN EXAMPLE 12
BUCKLING EXAMPLE USING THE FINITE DIFFERENCE METHOD
SYMBOLS USED IN THIS DESIGN EXAMPLE

WOH.....................................................................................Weight of Hammer 7-54

WOR..............................................................................................Weight of Rod 7-54
psf..............................................................................Pounds per Square Foot 7-55
ID................................................................................................. Inside Diameter 7-55
HPM.......................................CHANCE HELICAL PULLDOWN® Micropile 7-55

A four-helix CHANCE® Helical Pile is to be installed

DESIGN EXAMPLES

into the soil profile as shown in Figure 8-34. The

top five feet is compacted granular fill and is
considered adequate to support lightly loaded
slabs and shallow foundations. The majority of the
shaft length (50 feet) is confined by very soft clay
described by the borings as “weight of hammer”
(WOH) or “weight of rod” (WOR) material. WOH
or WOR material means the weight of the 130-lb
drop hammer or the weight of the drill rod used
to extend the sampler down the borehole during
the standard penetration test is enough to push
the sampler down 18+ inches. As a result, a low
cohesion value (15 psf) is assumed. The helix
plates will be located in dense sand below 55 feet.
Determine the critical buckling load of a Type SS175
1-3/4” square shaft and Type RS3500.300 round
shaft piles using LPILEPLUS 3.0 for Windows®
(ENSOFT, Austin, TX).
When the computer model is completed, the
solution becomes an iterative process of applying
successively increasing loads until a physically
logical solution converges. At or near the critical
buckling load, very small increasing increments of
axial load will result in significant changes in lateral
deflection – which is a good indication of elastic
buckling. Figure 7-38 is an LPILEPLUS output
plot of lateral shaft deflection vs depth. As can be
seen by the plot, an axial load of 14,561 lb is the
critical buckling load for a Type SS175 1-3/4” square
shaft because of the dramatic increase in lateral
deflection at that load compared to previous lesser
loads. Figure 8-36 indicates a critical buckling load
Foundation Details of 69,492 lb for Type RS3500.300 round shaft.
Figure 7-37

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Note that over the same 50-foot length of very soft clay, the well-known Euler equation predicts a critical
buckling load for Type SS175 of 614 lb with pinned-pinned end conditions and 2,454 lb with fixed-fixed
end conditions. The Euler critical buckling load for Type RS3500.300 is 3,200 lb for pinned-pinned
and 12,800 lb for fixed-fixed. This is a good indication that shaft confinement provided by the soil will
significantly increase the buckling load of helical piles. This also indicates that even the softest materials
will provide significant resistance to buckling.
All extendable helical piles have couplings or joints used to connect succeeding sections together in
order to install the helix plates in bearing soil. One inherent disadvantage of using the finite difference
method is its inability to model the effects of bolted couplings or joints that have zero joint stiffness
until the coupling rotates enough to bring the shaft sides into contact with the coupling walls. This is
analogous to saying the coupling or joint acts as a pin connection until it has rotated a specific amount,
after which it acts as a rigid element with some flexural stiffness. All bolted couplings or joints, including
square shaft and round shaft piles, have a certain amount of rotational tolerance. This means the joint
initially has no stiffness until it has rotated enough to act as a rigid element. In these cases, it is probably
better to conduct buckling analysis using other means, such as finite element analysis, or other methods
based on empirical experience as mentioned earlier.
If couplings are completely rigid, i.e., exhibit some flexural stiffness even at zero joint rotation, axial load
is transferred without the effects of a pin connection, and the finite difference method can be used. An

DESIGN EXAMPLES
easy way to accomplish rigid couplings with round shaft piles is to pour concrete or grout down the ID of
the pipe after installation. Another method is to install a grout column around the square or round shaft
of the foundation using the CHANCE® Helical Pulldown® micropile (HPM) method. The HPM is a patented
(U.S. Patent 5,707,180) installation method initially developed to install helical anchor foundations in very
weak soils where buckling may be anticipated.

LPILEPLUS Output Plot of Deflection vs Depth LPILEPLUS Output Plot of Deflection vs Depth
Figure 7-37 Figure 7-37

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 DESIGN EXAMPLE 13
BUCKLING EXAMPLE USING THE FINITE ELEMENT METHOD
SYMBOLS USED IN THIS DESIGN EXAMPLE

SPT............................................................Standard Penetration Test 7-56

N.....................................................................................SPT Blow Count 7-56
psf................................................................. Pounds per Square Foot 7-56
kip..............................................................................................Kilopound 7-56
HPM......................... CHANCE HELICAL PULLDOWN® Micropile 7-56
DESIGN EXAMPLES

Displaced Shape of Shaft ANSYS® Output

Figure 7-41

A three-helix CHANCE® Helical Type SS5 1-1/2” square shaft helical

pile is to be used to underpin an existing townhouse structure that
has experienced settlement (see Figure 8-37 for soil profile details).
The top 12 feet is loose sand fill, which probably contributed to the
settlement problem. The majority of the shaft length (30 feet) is
confined by very soft clay with an SPT blow count “N” of 2. As a
Foundation Details result, a cohesion value (250 psf) is assumed. The helix plates will be
Figure 7-40 located in medium-dense sand below 42 feet. Determine the critical
buckling load using the ANSYS integrated file element model.
Output indicates the Type SS5 1-1/2” square shaft buckled at around 28 kip. Figure 8-38 shows the
displaced shape of the shaft (exaggerated for clarity). The “K0” in Figure 8-38 are the locations of the
shaft couplings. Note that the deflection response is controlled by the couplings, as would be expected.
Also note that the shaft deflection occurs in the very soft clay above the medium-dense bearing stratum.
Since the 28 kip buckling load is considerably less than the bearing capacity (55+ kip) it is recommended
to install a grout column around the 1-1/2” square shaft using the CHANCE® Helical Pulldown® micropile
(HPM) method.

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 CORROSION

Page A-1 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 CORROSION - AN OVERVIEW
APPENDIX A

CONTENTS

INTRODUCTION................................................................................................. A-4
CORROSION THEORY..................................................................................... A-4
SOIL ENVIRONMENTS..................................................................................... A-6
PREDICTING CORROSION LOSS................................................................. A-8
CORROSION LOSS RATES............................................................................. A-10
FIELD MEASUREMENT OF SOIL RESISTIVITY....................................... A-13
CORROSION CONTROL TECHNIQUES..................................................... A-15
DESIGN EXAMPLES.......................................................................................... A-21
CORROSION

SYMBOLS USED IN THIS SECTION

pH.......................................................... Acidity or Alkalinity of a Solution A-7

ASTM................................ American Society for Testing and Materials A-7
V............................................................................................................... Voltage A-7
I..............................................................................................Electrical Current A-25
R...............................................................................Resistance or Resistivity A-8
L.........................................................................................................Pin spacing A-8
NBS.............................................................. National Bureau of Standards A-8
FHWA....................................................Federal Highway Administration A-9
AASHTO................................American Association of State Highway
and Transportation Officials A-9

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 Rmeter................ Resistivity Indication from Nillson Resistivity Meter A-13
WSF......................................................................... Wenner Spacing Factor A-13
CL...............................................................................Corrosion Weight Loss A-17
GWT............................................................................... Ground Water Table A-19
ppm........................................................................................ Parts per Million A-9
ASL................................................................................ Allowable Steel Loss A-21
SL..................................................................................................... Service Life A-22
G................................................................ Amount of Galvanized Coating A-23
Ws.................................................................................... Weight of Steel Pile A-24
K2..........................................................................Weight Loss by Corrosion A-24

CORROSION
DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted prior to any
installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption, revision, implementation,
use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in its network of installing contractors and
dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of CHANCE® Civil
Construction foundation support products.

Page A-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 INTRODUCTION
Corrosion is defined as the degradation of a material or its properties due to a reaction with the environ-
ment. Corrosion exists in virtually all materials, but is most often associated with metals. Metallic corro-
sion is a naturally occurring process in which the surface of a metallic structure is oxidized or reduced
to a corrosion product such as rust by chemical or electrochemical reaction with the environment. The
surface of metallic structures is attacked through the migration of ions away from the surface, resulting
in material loss over time. Given enough time, the material loss can result in significant reduction of area,
which in turn leads to a reduction in the structural capacity of a given metallic element. When corrosion
eventually destroys a sufficient amount of the structure’s strength, a failure will occur.
The corrosion mechanisms involved with buried metallic structures are generally understood, but ac-
curate prediction of metal loss rates in soil is not always easily determined. This appendix provides an
introduction to the concepts of underground corrosion and the factors that influence this corrosion in
disturbed and undisturbed soils. A few design examples are provided to give the reader a better under-
standing as to whether corrosion is a critical factor in a CHANCE® helical pile/anchor application. This
section is not intended to be a rigorous design guide, but rather a “first check” to see if corrosion is a
practical concern given the specific project site conditions. A qualified corrosion engineer should be
consulted for a site specific recommendation if steel foundation products are to be used in a known cor-
rosive soil.
Experience over the past 50 years has shown the vast majority of square shaft and round shaft helical
anchors/piles have a calculated service life well in excess of the design life of the structure (typically 50
CORROSION

to 75 years in the United States). In highly corrosive soils and areas of stray currents (e.g., underground
transmission pipelines, DC railroads) additional measures must be taken to protect steel foundation prod-
ucts. In these cases, active protective measures such as sacrificial anodes are employed.

CORROSION THEORY
To understand why metallic corrosion occurs, it is necessary to understand how a metal, such as carbon
steel, is formed. During the steel making process, natural low energy iron ore is refined into metal. This
process adds a great deal of energy to the metal. When the steel is placed into a corrosive environment,
it will, by natural processes, return to its low energy state over time. To make the return trip, the steel
must give up the energy gained at the mill. This is the essence of the reduction process that we call cor-
rosion.
Mechanical strength, physical size and shape, and chemical composition of the steel are all properties
that must be considered when designing CHANCE helical pile/anchors. Mechanical and physical proper-
ties are well defined and controlled during the manufacturing process. This is also true of the chemical
composition, primarily due to the superior process controls used by the steel mills. Of the three proper-
ties, chemical composition is the primary factor with respect to corrosion.
Corrosion of steel is an electrochemical process. Romanoff (1957) stated:
“For electrochemical corrosion to occur there must be a potential difference between two points
that are electrically connected and immersed in an electrolyte. Whenever these conditions are ful-
filled, a small current flows from the anode area through the electrolyte to the cathode area and
then through the metal to complete the circuit, and the anode area is the one that has the most
negative potential, and is the area that becomes corroded through loss of metal ions to the elec-
trolyte. The cathode area, to which the current flows through the electrolyte, is protected from
corrosion because of the deposition of hydrogen or other ions that carry the current.
“The electrochemical theory of corrosion is simple, i.e., corrosion occurs through the loss of metal
ions at anode points or areas. However, correlation of this theory with actual or potential corro-
sion of metals underground is complicated and difficult because of the many factors that singly
or in combination affect the course of the electrochemical reaction. These factors not only deter-

Page A-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 mine the amount or rate at which corrosion occurs but also the kind of corrosion.”
Depending on the many factors that affect the electrochemical reaction, corrosion can affect a metal in
several different ways. Some of these types are listed below:

CORROSION TYPES, TABLE A-1

TYPE CHARACTERISTICS
Uniform or Near Uniform Corrosion takes place at all area of the metal at the same or a similar rate.
Some areas of the metal corrode at different rates than other areas due to heterogeneities in
Localized
the metal or environment. This type of attack can approach pitting.
Very highly localized attack at specific areas resulting in small pits that may penetrate to
Pitting
perforation.

Considerations need to be applied as to the types and rates of corrosion anticipated. Current theory does
not permit accurate prediction of the extent of expected corrosion unless complete information is available
regarding all factors. Therefore, uniform corrosion will be the corrosion type discussed herein.
Romanoff states there are several conditions that must be met before the corrosion mechanism takes place.
These are:
Electrical Factors
Two points (anode and cathode) on a metallic structure must differ in electrical potential. The an-
ode is defined as the electrode of an electrochemical cell at which oxidation occurs, i.e., the negative
terminal of a galvanic cell. The cathode is defined as the electrode of an electrochemical cell at which

CORROSION
reduction occurs, i.e., the positive terminal of a galvanic cell. An electrical potential can be caused by
differences in grain orientation within the steel structure, i.e., different orientations of the steel grain
structure can cause some grains to act as anodes while others act as cathodes, while the rest of the
steel material exhibits excellent electrical conductivity. In addition, chemical anisotropy, non-metallic
inclusions, strained and unstrained areas, and other imperfections on the surface of a metal can create
potential differences that drive the corrosion process.
Metallic Path
The anode and the cathode must be electrically bonded or connected to complete the circuit.
Electrolyte
The principle function of soil moisture is to furnish the electrolyte for carrying current. The ions in
the electrolyte may be hydrogen and hydroxyl ions from the water itself and a variety of cations
and anions, which depend upon the number and amount of soluble salts dissolved in the water. The
presence of these ions determines the electrical conductivity, expressed as resistivity (measured in
ohms/cm), of the electrolyte, as well as chemical properties such as acidity or alkalinity, and the de-
velopment of chemical reactions between the primary products of corrosion and the electrolyte. For
example, ferrous material is corroded by electrolytes that contain sulfates or chlorides from the soil
because the corrosion products formed at the anode and the cathode are both soluble.
Aeration
Aeration affects the access of oxygen and moisture to the metal. Oxygen, either from atmospheric
sources or from oxidizing salts or compounds, stimulates corrosion by combining with metal ions to
form oxides, hydroxides, or metal salts. If corrosion products are soluble or are otherwise removed
from the anodic areas, corrosion proceeds, but if the products accumulate, they may reduce corrosion
by providing a barrier that is more noble (cathodic) than the bare metal. The aeration characteristics
of a soil are dependent upon physical characteristics such as the particle size, particle size distribu-
tion, and unit weight. In volume change soils such as clay, a reduction in moisture content results in
cracks that provide effective channels for the oxygen of the air to reach buried metal. Disturbed soils
such as fill result in oxygen being more readily available. In some instances, atmospheric oxygen can
become trapped in isolated pockets or cells creating the potential for localized anodic regions.

Page A-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 SOIL ENVIRONMENTS
Soil Type
Soils constitute the most complex environment known to metallic corrosion. Corrosion of metals in soil can
vary from relatively rapid material loss to negligible effects. Obviously, some soil types are more corrosive
than others. The origin of soils, along with climate, geologic location, plant and animal life, and the effects of
man all influence the corrosive potential of a given soil. Chemical analysis of soils is usually limited to deter-
minations of the constituents that are soluble in water under standardized conditions. The elements that are
usually determined are the base-forming elements, such as sodium, potassium, calcium, and magnesium;
and the acid-forming elements, such as carbonate, bicarbonate, chloride, nitrate, and sulfate. The nature and
amount of soluble salts, together with the moisture content of the soil, largely determine the ability of the
soil to conduct an electric current. Therefore, fine-grained soils such as clays and some silts are considered
to have a greater corrosion potential because they typically have lower hydraulic conductivity resulting in the
accumulation of acid and base forming materials, which cannot be leached out very quickly. However, granu-
lar soils such as sands and gravels are considered to have a reduced corrosion potential because they typi-
cally have increased hydraulic conductivity, resulting in the leaching of accumulated salts.
Ground Water
Moisture content in soil will probably have the most profound effect when considering corrosion potential
than any other variable. No corrosion will occur in environments that are completely dry. The effect of mois-
ture content on the resistivity of a clay soil is shown in Figure A-1. When the soil is nearly dry, its resistivity is
very high (i.e., no corrosion potential). However, the resistivity decreases rapidly with increases in moisture
CORROSION

content until the saturation point is reached, after which further additions of moisture have little or no effect

Effect of Moisture on Soil Resistivity Effect of Temperature on Earth Resistance

(Romanoff, 1957) (Romanoff, 1957)
Figure A-1 Figure A-2

Page A-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
on the resistivity. Figure A-2 shows the effect of temperature on the resistivity of a soil. As the temperature
decreases down to the freezing point (32°F or 0°C), the resistivity increases gradually. At temperatures below
the freezing point, the soil resistivity increases very rapidly.
Soil pH
Soil pH can be used as an indicator of corrosion loss potential for metals in soil. The term “pH” is defined as
the acidity or alkalinity of a solution that is assigned a number on a scale from 0 to 14. A value of 7 represents
neutrality, lower numbers indicate increasing acidity and higher numbers increasing alkalinity. Each unit of
change represents a ten-fold change in acidity or alkalinity which is the negative logarithm of the effective
hydrogen-ion concentration or hydrogen-ion activity in gram equivalents per liter of solution. The develop-
ment of acidity in soils is a result of the natural processes of weathering under humid conditions. Acidic soils
are those that have had soluble salts
and other materials removed, usu-
ally by moderate to high rainfall. In
general, the soils of the Midwest and
Eastern United States are acid to
a considerable depth, whereas the
soils whose development has been
retarded by poor drainage or other
conditions are alkaline. Most soils fall Corrosion of Metal in Soil vs pH
within a pH range that is strongly Figure A-3

CORROSION
acid to mildly alkaline.
Extremely acid soils (below pH 4.5) and very strongly alkaline soils (above pH 9.1) have significantly high
corrosion loss rates when compared to other soils (see Figure A-3). Soil pH is best measured in the field
using a pH meter and following the methods defined in ASTM G 51 – 77.
Soil Resistivity
Soil resistivity (the reciprocal of conductivity) is the one variable that has the greatest influence on corrosion
rate. However, other factors such as hydrogen-ion concentration, soluble salts and total acidity are interrelat-
ed, and it is difficult to control conditions so that there is only one variable. In general, the lower the resistiv-
ity, the higher the corrosion rate. Metals buried in low resistivity soils will generally be anodic, whereas metals
buried in adjacent high resistivity soils will generally be cathodic.
As shown in Figure A-1, moisture content has a profound effect on resistivity. Soil that is completely free of
water has extremely high resistivity. For example, sandy soils that easily drain water away are typically non-
corrosive; clayey soils that hold water have low resistivity and are typically corrosive. Backfill material will
generally be more corrosive than native
earth because the backfill soil has a high-
er moisture content. In addition, backfill
material typically never reconsolidates
back to the same degree as native soil,
allowing more penetration and retention
of water.
Soil resistivity is typically measured
using one or both of two methods: (1)
testing onsite with the Wenner four-pin
method, and/or (2) taking a soil sample
to a laboratory for a soil box resistiv-
ity test. The recommended practice is
the onsite Wenner four-pin method per
ASTM G57-78. The four-pin method is
Wenner 4-Pin Method for Measuring Soil Resistivity recommended because it measures the
Figure A-4 average resistivity of a large volume of
earth with relative ease. As Figure A-4

Page A-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 shows, this method places four pins at equal distances from each other. A current is then sent through
the two outer pins. By measuring the voltage across the two inner pins, the soil resistance can be calcu-
lated using Ohm’s Law (V= IR). Soil resistivity can be determined using Equation A-1.

Resistivity = 191.5 (R) (L) (ohms/cm) Equation A-1

where R = Resistance measured with a soil resistivity meter
L = Pin spacing (ft)

The soil box resistivity test is not recommended because it requires taking large number of samples for an
accurate map of soil resistivities in a given area. The soil box test is also much more time-consuming than the
four-pin method. Table A-2 is offered as a guide in predicting the corrosion potential of a soil with respect to
resistivity alone.

SOIL RESISTIVITY AND POTENTIAL CORROSION RATE, TABLE A-2

RESISTANCE CLASSIFICATION SOIL RESISTIVITY (ohms/cm) CORROSION POTENTIAL
Low 0 - 2000 Severe
Medium 2000 - 10,000 Moderate
High 10,000 - 30,000 Mild
Very High Above 30,000 Unlikely
CORROSION

PREDICTING CORROSION LOSS

Bare Steel
The National Bureau of Standards (NBS) performed extensive studies of underground corrosion between
1910 and 1955. More than 36,500 metal samples were exposed at 128 test locations throughout the United
States. In 1957, Romanoff presented the results of these investigations in Underground Corrosion (1957). The
studies showed that most underground corrosion was a complex electrochemical process dependent on the
various properties discussed previously. The NBS studies were primarily concerned with buried pipeline cor-
rosion. Since pipes are installed in backfilled trenches, the NBS work was performed on specimens placed in
trenches ranging from 18 in (0.46 m) to 6 ft (1.8 m) deep. The following conclusions can be drawn from these
studies:
• The metal loss rates reported were from samples placed in backfilled, i.e., disturbed soils.
• Atmospheric oxygen or oxidizing salts stimulate corrosion by combining with metal ions to form ox-
ides, hydroxides, or metallic salts. This is particularly true in disturbed soils at or near the soil surface.
• The least corrosive soils had resistivities above 3,000 ohms/cm and low soluble salt concentrations.
• Metal loss rates in disturbed soils can be determined by assuming they will be similar to the loss rates
found at test sites with similar pH and resistivity levels as provided in NBS Circular 579, Tables 6, 8 and
13.
Hubbell Power System, Inc. bulletin 01-9204, Anchor Corrosion Reference and Examples, contains extensive
metal loss rate data derived from Romanoff’s work. It is recommended that this information be used to deter-
mine the service life of non-galvanized steel in disturbed soil. The service life for most structures in the United
States is 50 to 75 years. Assuming a corrosion allowance for steel piles/piers, Romanoff’s metal loss rate data
for specific soil types and locations can be used to determine if the required service life can be achieved.

Page A-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Romanoff’s data can also be arranged in easy-to-
use graphs or tables. Figure A-5 provides a pre-
liminary estimate for metal corrosion loss of bare
steel if specific information is available on the soil
(soil type, pH and resistivity). Figure A-5 provides
a technique for quickly assessing those situa-
tions for which concern and design consideration
for corrosion must be taken into account when
metallic structures are placed below ground. For
example, a clay soil with resistivity of 2000 ohms/
cm and a pH of 6 will have an average metal loss
rate of approximately 5 oz/ft2/10yrs, or 0.5 oz/ft2/
yr. This figure was developed from the results of
the NBS studies in addition to similar field experi-
mentation results as presented in the Proceedings,
Eighth International Ash Utilization Symposium,
Volume 2, American Coal Ash Association, Wash-
ington, DC, 1987.
The Federal Highway Administration (FHWA) has
proposed uniform corrosion loss rates based on
a simple assessment of the electrochemical index

CORROSION
properties. Per FHWA-RD-89-198, the ground is
considered aggressive if any one of the critical
indicators in Table A-3 shows critical values.

Steel Loss Due to Corrosion

Figure A-5

ELECTROMECHANICAL PROPERTIES OF MILDLY CORROSIVE SOILS, TABLE A-3

PROPERTY TEST DESIGNATION CRITERIA
Resistivity AASHTO T-288-91 > 3000 ohm/cm
pH AASHTO T-289-91 >5 < 10
Sulfates AASHTO T-290-91 200 ppm
Chlorides AASHTO T-291-91 100 ppm
Organic Content AASHTO T-267-86 1% maximum

The design corrosion rates, per FHWA-SA-96-072, suitable for use in mildly corrosive soils having the electro-
chemical properties listed in Table A-3 are:
For zinc: 15 µm/year (0.385oz/ft2/yr) for the first two years
4 µm/year (0.103 oz/ft2/yr) thereafter
For carbon steel: 12 µm/year (0.308 oz/ft2/yr)

Page A-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
CORROSION

Nomograph for Estimating the Corrosion Rate of Pile/Anchor Shafts

Figure A-6

Examples:
• For pH of 6.5 and resistivity of 200 ohms/cm weight loss is approximately 1.3 oz/ft2/yr and expected life
(for 1/8” shaft loss) is approximately 65 years.
• For pH of 7.5 and resistivity of 200 ohms/cm weight loss is approximately 2.3 oz/ft2/yr and expected life
(for 1/8” shaft loss) is approximately 38 years.
Other methods are available to predict corrosion loss rates. Figure A-6 is a nomograph for estimating the
corrosion rate of helical anchor/pile/pier shafts. It is a corrosion nomograph adapted from the British Cor-
rosion Journal (King, 1977). Its appeal is its ease of use. If the resistivity and soil pH are known, an estimate
of the service life (defined as 1/8” material loss, for example) of a CHANCE® helical pile/anchor shaft can be
obtained for either an acidic or alkaline soil.

CORROSION LOSS RATES

Water/Marine Environment
Factors other than resistivity and pH can have a strong influence on corrosion loss rates. It is well known that
marine environments can be severely corrosive to unprotected steel, particularly in tidal and splash zones.
Corrosion loss rates in these environments can be quite high, averaging 6.9 oz/ft.2 (Uhlig, Corrosion Hand-
book, 2000). Salt spray, sea breezes, topography, and proximity all affect corrosion rate. Studies have shown
that the corrosion rate for zinc exposed 80 ft (24.4 m) from shore was three times that for zinc exposed 800
ft (244 m) from shore.

Page A-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Seawater immersion is less corrosive than tidal or splash zones. This is because seawater deposits protective
scales on zinc and is less corrosive than soft water. Hard water is usually less corrosive than soft water toward
zinc because it also deposits protective scales on the metallic surface. Table A-4 provides corrosion loss rates
of zinc in various waters. In most situations, zinc coatings would not be used alone when applied to steel
immersed in seawater, but would form the first layer of a more elaborate protective system, such as active
protection using sacrificial anodes.
CORROSION OF ZINC IN VARIOUS WATERS (CORROSION HANDBOOK, VOLUME 13
CORROSION, ASM INTERNATIONAL), TABLE A-4
WATER TYPE µ m/yr mils/yr oz/ft2
Seawater
Global oceans, average 15 - 25 0.6 - 1.0 0.385 - 0.642
North Sea 12 0.5 0.308
Baltic Sea and Gulf of Bothnia 10 0.4 0.257
Freshwater
Hard 2.5 - 5 0.1 - 0.2
Soft river water 20 0.8 0.513
Soft tap water 5 - 10 0.2 - 0.4 0.128 - 0.257
Distilled water 50 - 200 2.0 - 8.0 1.284 - 5.130

CORROSION
Corrosion in undisturbed soil
In NBS Monograph 127, (Underground Corrosion of Steel Pilings) (Romanoff, 1972), it was reported that driven
steel piles did not experience appreciable corrosion when driven into undisturbed soils. These findings were
obtained during NBS studies of steel pile corrosion. Romanoff also stated that the NBS corrosion data for
steel exposed in disturbed soils was not applicable to steel piles driven in undisturbed soil. He concluded:
“. . . that soil environments which are severely corrosive to iron and steel buried under disturbed
conditions in excavated trenches were not corrosive to steel piling driven in the undisturbed soil. The
difference in corrosion is attributed to the differences in oxygen concentration. The data indicates
that undisturbed soils are so deficient in oxygen at levels a few feet below the ground line or below
the water table zone that steel pilings are not appreciably affected by corrosion, regardless of the soil
types or the soil properties. Properties of soils such as type, drainage, resistivity, pH, or chemical com-
position are of no practical value in determining the corrosiveness of soils toward steel pilings driven
underground.”
The following conclusions can be drawn from these studies:
• Oxygen is required at cathodic sites to support underground corrosion of a steel foundation product.
• Disturbed soils (fill) contain an adequate supply of oxygen to support underground corrosion, at least
at shallow depths. Thus, the top-most extension(s) of the CHANCE® helical pile/anchor central steel
shaft merits corrosion protection, either using passive protection like zinc, epoxy or teflon coatings or
active protection like sacrificial anodes.
• The aggressiveness of disturbed soils can be measured, and they can be classified as aggressive and
non-aggressive (see Table A-2).
• Undisturbed soils were deficient in oxygen a few feet below the ground surface, or below the water
table. It is recommended to install the helical bearing plates of a helical pile/anchor into de-aerated
soil.

Page A-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Disturbed
Soil
Corrosion
Water Table
Corrosion Soil

Extension Extension
Undisturbed Section
Section
Soil

Helical Helical
Screw Screw
Lead Foundation
Foundation Section
CORROSION

Corrosion of Helical Pile/Anchor in Corrosion of Helical Pile/Anchor

Disturbed Soil at the Waterline
Figure A-7 Figure A-8

The role of oxygen in an undisturbed soil overrides

the effects of soil resistivity, pH, etc. In those situa-
tions where a steel foundation product is installed
into a soil profile where a disturbed soil layer overlies
undisturbed soil, the section of the central shaft in the
Concrete disturbed soil is cathodic to the rest of the foundation
Cathode in the undisturbed region as illustrated in Figure A-7.
Soil As a result, the most severe corrosion occurs on the
Anode section of the central shaft just below the disturbed
Corrosion
layer.
Extension Similarly, a steel foundation product located in undis-
Section turbed soil with a high water table can suffer some
corrosion attack at the waterline as illustrated in Fig-
Helical ure A-8. This combination does not result in serious at-
Screw tack, but it is believed that the situation is aggravated
Foundation by a continuously changing water table, which would
draw in oxygen as the waterline dropped. The section
Lead of the central shaft above the waterline acts as a weak
Section
cathode to the anode below the waterline.
Helical piles are commonly terminated in concrete
cap or grade beams. The area of steel in the concrete
forms a passive oxide film generated by the action
of the highly alkaline environment, and this area is
Corrosion of Helical Pile/Anchor Foundation
cathodic to the rest of the helical pile in the soil. How-
With a Concrete Cap
ever, the high resistivity of the concrete limits the ef-
Figure A-9
fectiveness of the cathode, thereby limiting the small
amount of corrosion attack to the region of the helical
pile immediately outside the concrete as illustrated in
Figure A-9.

Page A-12 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
FIELD MEASUREMENT OF SOIL RESISTIVITY
Field measurement of soil resistivity is not a difficult or time consuming process and results in the most ac-
curate assessment of corrosion potential for the site. Hubbell Power Systems, Inc. recommends the use of
the Nillson Model 400 soil resistance meter system. The depth of the soil resistivity measurement is directly
related to the pin spacing on the surface. The most accurate assessment is obtained by performing the test
using a pin spacing of 5-20 foot intervals. In addition, the test should be repeated at a right angle to the origi-
nal test to ensure that stray currents are not influencing the readings.
A. Equipment Set-Up
1. Insert the four sensor pins into the soil in a straight line leading away from the Resistivity Meter at
a center-to-center distance of five feet (see Figure A-10).
2. Connect one wire to each pin and to the appropriate terminal on the Nillson meter.
B. Resistivity Measurement
1. Adjust the OHMS resistivity dial and the MULTIPLIER dial to the maximum setting (turned fully to
the right) (see Figure A-11).
2. Place the SENSITIVITY switch in the LOW position and rotate the MULTIPLIER dial to the left until
the meter needle goes past the NEUTRAL point, then rotate the MULTIPLIER one position to the
right. Note the MULTIPLIER (M) amount on the field notes.

CORROSION
3. Move the OHMS dial to the left until the meter needle is at NEUTRAL.
4. Adjust the SENSITIVITY switch to HIGH position and adjust the OHMS dial to refine the reading.
5. Record the reading (Rmeter)
6. Return the OHMS and MULTIPLIER to the maximum settings and repeat the test.
7. Repeat the test with the pins spaced at 10-feet on center, then at 15-feet and 20-feet on center.
Record the readings
C. Calculation of Soil Resistivity

R = Rmeter (M) (WSF) Equation A-2

where: Rmeter = Meter resistance reading (ohms)
M = Meter MULTIPLIER reading
WSF = Wenner spacing factor = 191.5L (ft) = 628L (m)
L = Pin spacing
R = Soil resistivity (ohms/cm)
D. Additional Resistivity Measurements
1. The soil resistivity (R) is the average value over the depth of soil equal to the spacing of the pins.
Therefore, to get a profile of the soil resistivity one must repeat the procedures in paragraph B
above with the pins spaced at 10, 15 and 20 feet on center.
2. Repeat the entire test at right angles to the original alignment.

Page A-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
CORROSION

Sensor Pin Installation Nillson Resistivity Meter

Figure A-10 Figure A-11

E. Documentation
Record the field data and the calculations onto the soil resistivity log. A sample log is presented be-
low (See Figure A-12).
F. Evaluate Results
When the Soil Resistivity (R) has been determined, refer to Figure A-5 to determine an estimate of
the loss of weight by corrosion over a 10-year period for underground bare steel structures.

COMBINED WENNER 4-PIN SOIL RESISTIVITY LOG

Location: Job No.

Date: Weather Conditions: Orientation of Pins:

WENNER METHOD OF SOIL RESISTIVITY

PIN SPACING METER RESISTANCE METER WENNER SPACING FAC- SOIL RESISTIVITY
(Depth in Feet) (RMeter) (ohms) MULTIPLIER TOR (WSF) R = (RMeter) x M x WSF
(M) (191.5* x Pin Spacing)

* If pin spacing is measured in meters, use WENNER SPACING FACTOR (WSF) of 628 instead of 191.5
Sample Resistivity Log
Figure A-12

Page A-14 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
CORROSION CONTROL TECHNIQUES
The amount and type of corrosion control is a function of structure type, service life, and the overall ag-
gressiveness of the project soils. The following requirements are typical. The specifier should review and
edit as appropriate for the project.
• Structure Type: Temporary structures generally do not require corrosion protection. A temporary
structure is defined within a specified time frame (i.e., months rather than years). In general, per-
manent structures have a service life greater than 24 months.
• Service Life: A typical service life of 50 to 75 years should be used unless otherwise specified.
If the service life of a temporary CHANCE® helical pile/anchor is likely to be extended due to con-
struction delays, it should be considered permanent. For a service life of less than 20 years in
non-aggressive soil, corrosion protection is not recommended.
• Soil: Soil can be classified as aggressive or non-aggressive. See Guide to Model Specification
-Helical Piles for Structural Support and Model Specification - Helical Tieback Anchors for Earth
Retention in Appendix C of this Technical Design Manual for examples of aggressiveness classifi-
cations. It is recommended that steel foundation elements installed into soils classified as aggres-
sive be provided with some type of corrosion protection.
Several alternatives are available to protect steel foundation products against corrosion and can be
roughly categorized in terms of cost. Because of the added cost, the need for corrosion protection must
be carefully determined and specified as necessary. Depending upon the classification as to the corro-

CORROSION
sion potential for a soil environment, several alternatives are available to deter the corrosion cycle and
extend the performance life of the underground steel element. These control measures can be split into
categories:
• Passive Control: For use in soils classified as mild to moderate corrosion potential. It typically
consists of a metal loss allowance (i.e., 1/8”) and/or coatings – such as galvanization or epoxy.
Passive control is relatively inexpensive.
• Active Control: For use in soils classified as moderate to severe corrosion potential. It typically
consists of cathodic protection via the use of sacrificial anodes. Active control is relatively expen-
sive and is used in permanent applications.
passive control
Allowable Metal Loss Rate
As mentioned previously, Hubbell Power Systems, Inc. bulletin 01-9204, “Anchor Corrosion Refer-
ence” and Examples, contains extensive metal loss rate data derived from Romanoff’s work. Other
metal loss rate data is presented on pages A-8 through A-12. The design examples at the end of this
section demonstrate passive control calculations that estimate the service life of helical pile shafts in
soil using these metal loss rates. Design Example 1 uses the metal loss rates from Romanoff (Bulletin
01-9204). The service life is defined as the estimated length of time required for 1/8” of material loss
to occur on the helical pile/anchor shaft. Design Example 2 uses the metal loss rates from Figure A-5
in conjunction with Equation A-2. The service life in this example is defined as the estimated length
of time required for a 10% material loss to occur on the helical pile shaft. Design Example 3 uses the
design corrosion rates per FHWA-SA-96-072 (as quoted here on page A-8) and an assumed service
life of 85 years.
The amount of loss in these design examples is strictly arbitrary, but the assumed material loss of 1/8”
in Design Example 1 is common for pile evaluation.
Galvanization (Passive Control)
Aggressive soils, and the conditions illustrated in Figures A-7, A-8, and A-9 demonstrate the need
to coat the section of the steel foundation product above the waterline in the disturbed soil and, in
particular, the area of the central shaft in the concrete cap or grade beam. Thus, by removing the
cathode, the anode/cathode system is disrupted resulting in reduced corrosion. If it were possible to
apply a coating capable of guaranteed isolation of the steel surface from the electrolyte (soil), all cor-

Page A-15 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 rosion concerns would be solved. However, a coating capable of 100% guaranteed isolation has yet
to be developed. Epoxy coatings provide excellent electrical isolation, but will chip and abrade easily
during handling and installation. The same holds true for porcelain, teflon, and polyurethane coatings.
A small chip or crack in the protective coating can cause corrosion activity to be highly localized,
possibly leading to severe damage. The single best coating for steel foundation products is hot dip
galvanizing.
The first step in the galvanizing process is pickling the steel in dilute acid. This removes any rust,
scale, oil or other surface contaminants. The clean steel is then dipped in a vat of molten zinc for time
periods ranging up to several minutes for the more massive steel foundations. After the hold pe-
riod, the zinc-coated steel is withdrawn from the vat at a controlled rate, which allows the coating to
quickly cool and harden. The result is a tough, combined zinc and zinc-iron coating which metallurgi-
cally bonds to the steel. Other galvanization processes, such as mechanical galvanizing and electro-
plating, do not form a coating that is metallurgically bonded to the steel.
Hubbell Power System, Inc. galvanizes to the latest ASTM standards – either ASTM A153 class B or
ASTM A123. ASTM A153 Class B requires an average weight of zinc coating to be 2.0 oz./ft2 (3.4 mils)
and any individual specimen to be no less than 1.8 oz./ft2 (3.1 mils). ASTM A123 can be used to specify

thicker zinc coatings – up to

2.3 oz./ft2 (3.9 mils) depending
on the coating thickness grade
CORROSION

used. Regardless of which ASTM

galvanizing specification is used,
typical zinc coating thickness
for hot-dip galvanized CHANCE®
Helical Pile/Anchor or ATLAS
RESISTANCE® Piers ranges be-
tween 4 and 6 mils.
Figure A-13 illustrates how zinc
and steel react to form zinc-iron
alloy layers. The bottom of the
picture shows the base steel,
then a series of alloy layers and,
on the outside, the relatively
Photomicrograph of Zinc Layer Section pure outer zinc layer. The under-
Figure A-13 lying zinc-iron alloy layers are
actually harder than the base
steel. Therefore, below the relatively soft pure zinc layer, the zinc-alloy layers provide protection in
abrasive conditions such as dense sands and gravels.
Hot dip galvanized coatings protect the carbon steel shaft in two ways. First, the zinc coating pro-
vides a protective layer between the foundation’s central shaft and the environment. Second, if the
zinc coating is scratched and the steel surface exposed, the zinc, not the steel, will corrode. This is
because zinc is a dissimilar metal in electrical contact with the steel, thus the difference in potential
between the two metals and their relative chemical performance (anode or cathode) can be judged
by examining a galvanic series as shown in Table A-5. The materials at the top of the list are most ac-
tive (anodic) compared to the noble (cathodic) materials at the bottom of the list. Steel is more noble
than zinc, thus the more active zinc coating will act as an anode and corrode while the more noble
steel will be the cathode and be protected.

Page A-16 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Service Life Increase Through Galvanization
Hubbell Power Systems, Inc. bulletin 01-9204, “Anchor Corrosion Reference and Examples,” contains
extensive metal loss rate data on galvanized steel derived from Romanoff’s work. It is recommended
that this information be used to determine the service life of the hot dipped galvanized coating in
disturbed soil. When hot-dip galvanized steel is used, the total service life should be increased by the
time it takes the zinc coating to be lost due to corrosion. Another method for estimating service life
increase is presented in the following paragraphs.
The results of the studies conducted by the National Bureau of Standards and by Porter indicated
that a galvanized coating (zinc) was effective in delaying the onset of corrosion in the buried steel
structures. Typical conclusions drawn from this study for 5 mil (3 oz/ft2) galvanized coatings include:
• It is adequate for more than 10 years corrosion protection for inorganic oxidizing soils.
• It is adequate for more than 10 years corrosion protection for inorganic reducing soils.
• It is insufficient for corrosion protection in highly reducing organic soils (pH<4), inorganic
reducing alkaline soils and cinders, typically offering 3 to 5 years of protection in such cases.
It was also noted, however, that the use of a galvanized coating significantly reduces the rate of cor-
rosion of the underlying steel structure once the zinc coating was destroyed.
The observed rates of corrosion for the galvanized coating were different (less) than that for bare
steel in the NBS study. For galvanized coatings (zinc) of 5 mils, Equation A-3 can be used to estimate
the corrosion (weight loss) rate.

CORROSION
CL1 = 0.25 - 0.12 log10 (R/150) Equation A-3
CL1 = Weight loss (oz/ft2/yr)
R = Soil resistivity (ohms/cm)

NOTE: For thinner galvanized coatings, the rate of galvanized coating loss is two to three times the
rate determined from Equation A-3.

Page A-17 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Bituminous and Other Coatings (Passive Control)
Bituminous as well as other materials have been used as coatings on buried steel elements for years
as a corrosion protection technique. The primary requirements of a bituminous coating are good
adherence (permanence), continuous coating and resistance to water absorption. The bituminous
coating can either be heat baked onto the shaft or field applied just prior to installation. As is
the case for the manufactured coatings, this coating technique prevents oxygen and water from
contacting the metal surface, thus preventing or retarding the corrosion process.
Bituminous or asphaltic coatings or paints only provide physical protection from the environment.
They will wear off quickly due to the abrasive action during installation of CHANCE® helical piles/
anchors. Extension sections are typically hot-dip galvanized, but other coatings can be specified.
Practical application of asphaltic coatings is generally limited to the extension sections located
at or near the surface where the coating will provide the greatest benefit. Bituminous and other
coatings are best applied in severely corrosive conditions where part of the helical anchor/pile is
exposed above grade. Examples are steel foundations used in tidal marshes, coastal regions, and
contaminated soils.
A limited amount of available data indicates that bituminous coatings can extend the performance
life of underground steel piles and piers by 5 to 15 years, depending on the soil environment and the
thickness of the coating. For the vast majority of CHANCE® helical piles/anchors applications, the use
of coating techniques (galvanized and/or bituminous) will provide a sufficiently long-term solution
for corrosion protection.
CORROSION

Cathodic Protection (Active Control)

As indicated previously, corrosion is an electrochemical process that involves a flow of direct
electrical current from the corroding (anodic) areas of the underground metallic structure into the
electrolyte and back onto the metallic structure at the non-corroding (cathodic) areas. In situations
where metallic structures such as Hubbell Power Systems, Inc. foundation products are to be
placed in a severe corrosive soil environment, an active corrosion control technique should be used.
This active control technique is termed cathodic protection. Cathodic protection is a method of
eliminating corrosion damage to buried steel structures by the application of DC current. The effect
of the DC current is to force the metallic surface to become cathodic (i.e., collecting current). If the
current is of sufficient magnitude, all metallic surfaces will become cathodic to the external anode.
Both sacrificial anode and impressed current (rectifier and ground bed) cathodic protection systems
are used to provide the required current. If the current source is derived from a sacrificial metal
(magnesium and zinc are the two most common galvanic anodes used in soils), the effectiveness
will depend on the soil properties in which it is placed. More available current is generated from a
sacrificial anode in low resistance soils than high resistance soils. It is also best to place impressed
current anode beds in lower resistant soils. However, since the available driving potential is greater
(rectifier control), the soil resistivity is less significant.
Current requirements needed to protect a steel structure from corrosion will vary due to physical and
environmental factors. These requirements could range from 0.01ma/ft2 of metal surface for a well-
applied, high-dielectric-strength plastic coating to 150 ma/ft2 for bare steel immersed in a turbulent,
high velocity, salt-water environment. In soil, 1 to 3 ma/ft2 is typically used as the required current to
protect carbon steel.
The basic principle in cathodic protection is to apply a direct current of higher electromotive
potential than that generated by the corroding metallic structure, thus effectively eliminating the
corrosion process.

Page A-18 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Sacrificial Anodes (Active Control)
In the case of CHANCE® helical piles/anchors, sacrificial anodes are the most common method of
cathodic protection used. This is done by electrically connecting the steel to a properly selected
anode of a less noble metal such as zinc or magnesium. The dissimilar metals buried in a common
electrolyte (soil) form a galvanic cell. The cell works much like the battery in the family car; the less
noble anode corrodes or sacrifices itself while the more noble cathode is protected. For steel to be
cathodically protected, it is generally recognized that at least one of the following conditions must be
met:
• The potential of the steel must be at -0.85 volts or more negative with respect to a saturated
copper-copper sulfate half-cell in contact with the electrolyte, or
• A potential shift of -0.3 volts or more negative upon connection of the cathodic protection.
Magnesium, zinc and aluminum are the most commonly used galvanic sacrificial anodes. The
sacrificial anode (galvanic) is attached to each underground metallic structure by a metallic
conductor (cable) and placed within the common electrolyte (soil medium). The sacrificial anode
works best when a small amount of current is needed and/or when the soil resistivities are low .
Anodes are installed normally 3 feet below the surface and 3 to 7 feet from the CHANCE® helical
piles/anchors.
In designing and using sacrificial anode systems, the soil profile conditions as to the type of soil,
resistivities, soil pH and location of the ground water table (GWT), if present, must be determined.

CORROSION
Among the design considerations for the system:
• Use of wire type or canister type anode
• Selection of the appropriate anode material (magnesium, titanium, etc.)
• Designing the ground bed (location, dimensions, horizontal vs. vertical, depth of placement,
type of backfill, etc.)
• Determining the number of piles/piers per anode
• Type, size and connections between pile(s) and the sacrificial anode.
The application of cathodic protection using galvanic sacrificial anode bags to underground metallic
structures offers the following advantages:
• No external power supply required
• Low system cost (bags and installation)
• Minimum maintenance costs

Cathodic Protection Products

Hubbell Power Systems, Inc. recommends a selection of magnesium anodes (9, 17, 32, and 48-pound bag
sizes) for cathodic protection of foundation support systems. Cathodic protection is generally used to
extend the life of a steel product in corrosive soil beyond the added life available by hot dip galvanizing
the components. While it is possible to protect mill finish steel, the engineer usually calls for the cathodic
protection in addition to zinc galvanizing.

Factors Influencing Anode Output:

• Soil Resistivity: Current output from the magnesium anode increases as the soil resistivity
decreases. Therefore, magnesium anodes are usually specified in applications where the soil
resistivity is 5,000 ohms/cm or less. The effectiveness of this type of cathodic protection
decreases as the resistivity increases above 5,000 ohms/cm. Above 10,000 ohms/cm resistivity,
magnesium anodes are not effective.

Page A-19 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 • Anode Surface Area: The amount of current output generated by an anode is directly
proportional to the surface area of the anode. Different manufacturers of cathodic protection
produce anodes with different surface areas. Just because magnesium anodes from different
manufacturers weigh the same is not to be assumed that the current output will be the same. The
data presented here is representative for the products identified here.
• Alloy Potential: H-1 magnesium alloy has an open circuit potential of -1.53 to -1.55 volts, which
works well with vertically installed foundation support systems. High potential anodes are
available from other sources. These high cost, high potential anodes are generally used along
horizontal pipelines where the higher potential produced by the anode translates to fewer anodes
being required. Table A-5 provides estimates of current output from a single, standard potential
H-1 magnesium alloy anode as related to soil resistivity.

MAGNESIUM ANODES, TABLE A-5

MAGNESIUM ANODES
TYPE H-1 STANDARD POTENTIAL MAGNESIUM

Item No Magnesium Weight Package Size Unit Weight

PSA4438 9 lb. 6” Dia. x 17” Tall 27

PSA4439 17 lb. 6-1/2” Dia. x 24” Tall 45

CORROSION

PSA5106 32 lb. 8” Dia. x 28” Tall 72

PSA4440 48 lb. 8” Dia. x 38” Tall 100

MAGNESIUM ANODE CURRENT OUTPUT – mA

Resistivity – ohm-cm 1,000 2,000 3,000 4,000 5,000
9# Anode 106.5 53.3 35.5 26.6 21.3
17# Anode 150 75 50 37.5 30
32# Anode 159 79.5 53 39.8 31.8
48# Anode 163.5 81.8 54.5 40.9 32.7

Design Example 4 at the end of this section provides a method for estimating the service life of a
sacrificial magnesium anode. For additional information on anode selection, refer to Hubbell Power
Systems, Inc. bulletin 2-8307, Cathodic Protection of Anchors – A Basic Guide to Anode Selection and
Hubbell Power Systems, Inc. bulletin 01-9204, Anchor Corrosion Reference and Examples.
Impressed Current (Active Control)
In areas of the most severe corrosion potential, where a larger current is required and/or in high
resistance electrolytes, an impressed current system is generally recommended which requires a power
source, rectifier and a ground bed of impressed current anodes. These systems require a continuous
external power source.
The majority of applications where Hubbell Power Systems, Inc. foundation products may be specified
will not require an active corrosion protection system. In those cases where the combination of soil and
electrolyte conditions requires an active system, the sacrificial anode protection system will likely be the
most economical approach.
Active cathodic protection systems must be individually designed to the specific application. The major
variables are soil moisture content, resistivity of soil and pH. Each of these items influences the final
selection of the cathodic protection system. Typical design life for the cathodic protection is 10 to 20
years, depending upon the size and length of the anode canister.

Page A-20 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
DESIGN EXAMPLES
Design Example 1:
• Project: Santa Rosa, CA Residence
The purpose of the calculations is to estimate the service life of type SS helical pile shafts on the
subject project. Service life is defined as the estimated length of time required for 1/8” of material
loss to occur on the helical pile shaft. This amount of loss is strictly arbitrary, but is common for
pile evaluation.
• Given:
Helical piles galvanized to ASTM A153 (Minimum Zinc Coating = 1.8 oz/ft2)
Soil resistivity is 760 ohms-cm minimum
Soil pH - 7.70
Water soluble chloride – 11 ppm
Water soluble sulfate – 417 ppm
• Assumptions:
It is assumed that the material loss rates will be similar to the loss rates found at test sites with
similar pH and resistivity levels as given in Romanoff’s Underground Corrosion, NBS Circular #579

CORROSION
(1957), Tables 6, 8 and 13.
In Circular #579, Site #5 is indicated as having a resistivity of 1,315 ohms-cm and a pH of 7.0.
This soil is Dublin Clay Adobe and is located around Oakland, California. In addition, Site #2
is indicated as having a resistivity of 684 ohms-cm and a pH of 7.3. This soil is bell clay and is
located around Dallas, Texas. The corrosion rates for these two sites will be used to estimate the
life of the type SS helical pile shaft material.
• Allowable Steel Loss:
Based on the loss of 1/8” thickness of the helical pile shaft, calculate the allowable steel loss (ASL)
in terms of weight per unit area:

ASL = (0.125 in) (0.283 lb/in3) (16)

= (0.566 oz/in2) (144 in2/ft2)
= 81.5 oz/ft2
• Average Metal Loss per Year:
From Site #5: (Dublin Clay Adobe)
EXPOSURE DURATION (years) WEIGHT LOSS (oz/ft2) LOSS PER YEAR (oz/ft2)
1.9 1.4 0.737
4.1 2.2 0.585
6.2 4.8 0.774
8.1 5.2 0.642
12.1 5.4 0.446
17.5 8.3 0.474

The average metal loss per year is 0.61 oz/ft2. Note that as the duration of exposure increases, the

Page A-21 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 material loss per year generally decreases.
• Pile Shaft Life:
To determine the pile shaft service life (SL), the allowable steel loss is divided by the average loss
per year:

SL = (81.5 oz/ft2) / (0.61 oz/ft2)

= 133.6 years
• Total Zinc Coating Loss:
CHANCE® helical piles/anchors are typically provided already hot dip galvanized per ASTM A153.
The coating thickness for ASTM A153 class B = 1.8 oz/ft2. From Romanoff, NBS Circular #579,
Page 110, Table 65 gives the following average loss rates for Site #5 soils:
EXPOSURE DURATION (years) WEIGHT LOSS (oz/ft2) LOSS PER YEAR (oz/ft2)
10.17 2.66 0.262

• Estimated Life of Zinc: 1.8 oz/ft2 / 0.262 oz/ft2 = 6.9 years

• Total Estimated Service Life of Helical Pile Shaft: 133.6 + 6.9 = 140.5 years
• From Romanoff Site #2 (Bell Clay):
CORROSION

EXPOSURE DURATION (years) WEIGHT LOSS (oz/ft2) LOSS PER YEAR (oz/ft2)
2.1 2.4 1.143

4.0 3.0 0.750

5.9 3.4 0.576
7.9 3.6 0.456
12.0 5.9 0.492
17.6 8.1 0.460

The average loss per year is 0.65 oz/ft2.

Note that as the duration of exposure increases, the
material loss per year generally decreases.
• Helical Pile Shaft Life:
To determine the helical pile shaft’s service life (SL), the allowable steel loss is divided by the
average loss per year.

SL = (81.5 oz/ft2) / (0.65 oz/ft2)

= 125.4 years
• Total Zinc Coating Loss:
CHANCE® Civil Construction helical anchors/piles are already provided hot dip galvanized per
ASTM A153. The coating thickness for ASTM A153 class B = 1.8 oz/ft2. From Romanoff, NBS
Circular #579, Page 110, Table 65 gives the following average loss rates for site #2 soils.
EXPOSURE DURATION (years) WEIGHT LOSS (oz/ft2) LOSS PER YEAR (oz/ft2)
9.92 0.44 0.044

• Estimated Life of Zinc: 1.8 oz/ft2 / 0.044 oz/ft2 = 40.9 years

• Total Estimated Service Life of Helical Pile Shaft: 125.4 + 40.9 = 166.3 years

Page A-22 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 • Summary:
Total estimated service life of helical pile shaft in Site #5 soils = 140.5 years
Total estimated service life of helical pile shaft in Site #2 soils = 166.3 years
These calculations are an estimate of the service life only (1/8” material loss from shaft) and are
based upon loss rates obtained from Romanoff’s disturbed soil sites. It is generally accepted
that the majority of any corrosion will occur at or near the surface. Therefore, it is very likely that
helical pile shaft metal loss will control the design. In the event the estimated service life does not
meet the design requirements, one option is to use a larger sized helical pile shaft.

Design Example 2:
• Project: An access bridge designed to cross a wetland area.
The purpose of the calculations is to estimate the service life of type RS3500.300 helical piles on
this project. The service life is defined as the estimated length of time required for a 10% metal
loss to occur to the helical pile shaft.
• Given:
1. Helical Piles will receive a hot dipped galvanized coating (G) of 5-mil thick (3-oz/ft2)
2. Soil Resistivity (R) – 1,000 ohms/cm

CORROSION
3. Soil pH – 6.0
4. Soil type – organic silt in top 10’ with SPT blow counts of 2 to 4 blows per foot.
• Assumptions:
1. The metal loss rates will be based on the values given in Figure A-5 with a pH of 6.0 and
a resistivity of 1,000 ohms/cm. These values place the organic silt in the severe corrosion
environment region.
2. The galvanized coating loss rates will be based on Equation A-3 as shown on page A-17.
• Estimated Life of Galvanized Coating:
To estimate average life for galvanized coating in a location with a soil resistivity of 1000 ohms/
cm, Equation A-3 is used:

CL1 = 0.25 - 0.12 log10 (R/150)

= 0.25 - 0.12 log10 (1000/150)
= 0.25 - 0.12 (0.824)
= 0.15 oz/ft2/yr
where: CL1 = Weight loss per year

The estimated life of the galvanized coat is:

L1 = G/CL1 Equation A-4

= (3 oz/ft2) / (0.15 oz/ft2)
= 20 years
Amount of galvanized coating = 3.0 oz/ft2
where: G = for typical hot dipped galvanized coating (5
mil)

Page A-23 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 L1 = Life expectancy (yrs)
• Estimated Life of of Steel:
The formula for estimating average life for loss in steel wall thickness is given in Equation A-5
below:
L2 = Ws/K2 Equation A-5
where: L2 = Life expectancy (yrs)
Ws = Weight of steel pile (oz/ft2)
Loss in weight by corrosion (oz/ft2/yr) as
K2 =
determined from Figure A-5

Reference to Figure A-5 indicates a corrosion weight loss range for bare steel of approximately 3
to 10 oz/ft2 for a 10-year period. In this case (also checking the NBS data) an estimate was used
of 8 oz/ft2 for 10 years. Therefore K2 = 8.0 oz/ft2 per 10 years or 0.8 oz/ft2/year.
A 10% weight loss of the wall thickness of the steel for the RS3500.300 pile results in:

Ws = 0.1 (0.300 in/12 in/ft) (489.6 lb/ft3) (16 oz/lb)

= 20 oz/ft2
CORROSION

The estimated additional life becomes:

L2 = Ws / K2
= (20 oz/ft2) / (0.8 oz/ft2/yr)
= 25 yrs

• Life Estimate Summary (Galvanized Steel Round Shaft):

Based upon the assumptions, the results of this analysis indicate that the CHANCE® Type
RS3500.300 helical pile as specified for the bridge foundation will experience an average 40 to
45 year estimated life.
Design Example 3:
Extendable helical piles/anchors consist of segmented elements that are coupled together with
structural bolts. It is possible for coupling bolts to be located near the surface in disturbed soils.
Therefore, it is recommended that the coupling bolt service life be calculated based on corrosion loss
rates. This can be accomplished using methods similar to those shown in Design Example 1.
• Determine the diameter reduction of Type SS5/150 coupling bolts using corrosion loss rates per
FHWA-SA-96-072. Type SS5/150 Helical Piles/Anchors use 3/4” diameter bolts per ASTM A325.
Assume a service life of 85 years.
• Total Zinc Coat Loss:
Hubbell Power Systems, Inc. provided fasteners are hot dip galvanized per ASTM A153. The
coating thickness for ASTM A153 class B = 1.8 oz/ft2.
Zinc loss the first two years: = 0.385 oz/ft2/year x 2 years = 0.77 oz/ft2
Estimated life of zinc coating = [1.8 oz/ft2 - 0.77 oz/ft2 = 1.03 oz/ft2/0.103 oz/ft2 = 10 years] + 2
years = 12 years
• Total Steel Loss:
Coupling bolt steel loss will occur after the zinc coating is lost. The exposure time to corrosion for
the bolt steel is: 85 years – 12 years = 73 years.
Bolt steel loss over 73 years: = 0.308 oz/ft2/year x 73 years = 22.5 oz/ft2

Page A-24 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 22.5 oz/ft2/144 in2/ft2 x 16 oz/lb x 0.283 lb/in3 = 0.035” (0.9 mm)
Diameter reduction after 85 years is 0.75”– 2 x 0.035” = 0.68” (17.3 mm)
• Determine the tensile load capacity reduction of type SS5/150 coupling bolts: The minimum
ultimate tensile strength for CHANCE® type SS5/150 helical piles/anchors is 70 kip. The failure
mechanism is double shear of the coupling bolt. Assuming a linear relationship between diameter
and shear capacity, the bolt diameter reduction from an 85-year exposure per FHWA-SA-96-072
corrosion loss rates suitable for use in mildly corrosive soils will result in a reduced tension load
capacity, i.e., 0.68 x 70/0.75 = 63.5 kips.
Design Example 4:
1. Estimated Average Life of Sacrificial Magnesium Type Anode:
The formula for estimating average life for sacrificial magnesium anode life is given in Equation A-6
below:

L3 = [57.08 (K3) (Wa)] / I Equation A-6

Life expectancy of magnesium or zinc anode
where: L3 =
(yrs)
K3 = Efficiency of anode bag (60%-70%)
Wa = Weight of anode (lbs)

CORROSION
Current output of anode (mA). Available from
Table A-5 for CHANCE® Civil Construction
I =
supplied anodes or from the vendor when using
other anodes.

NOTE: Equation A-6 is not unit consistent.

Assume that in the previous design example 2, the pile performance life is to be further extended
(beyond 40 to 45 years) by use of a 48-pound magnesium sacrificial anode for each pile. For this
size bar and soil resistivity condition (R = 1000 ohms/cm), the vendor indicates I = 163.5 mA and
K = 65%. Therefore, equation A-12 becomes:

L3 = [57.08 (0.65) (48)] / 163.5

= 11 yrs

Page A-25 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 References:
1. A.B. Chance Company, Anchor Corrosion Reference and Examples, Bulletin 01-9204, A.B. Chance
Company, Centralia, MO, 1992.
2. A.B. Chance Company, Chance Anchor Corrosion Report, Bulletin 31-9403, reprinted with permission
from the Texas Department of Transportation, A.B. Chance Company, Centralia, MO, 1994.
3. Corrosion and Its Control: An Introduction to the Subject, Second Edition, NACE International, 1995.
4. Corrosion Tests and Standards - Application and Interpretation, ASTM Manual Series, MNL 20, 1995.
5. Escalante, Edward, Concepts of Underground Corrosion, part of ASTM STP 1013, Effects of Soil
Characteristics on Corrosion, Edited by V. Chaker and J.D. Palmer, American Society for Testing and
Materials, Philadelphia, PA, 1989.
6. Federal Highway Administration, Publication No. FHWA-SA-96-072, Corrosion/Degradation of Soil
Reinforcement for Mechanically Stabilized Earth Walls and Reinforced Slopes.
7. King, R.A., Corrosion Nomograph, TRRC Supplementary Report, British Corrosion Journal, 1977.
8. Metals Handbook, Volume 13, Ninth Edition, Corrosion, ASM International, Metals Park, Ohio, 1987.
9. Porter, Frank, Corrosion Resistance of Zinc and Zinc Alloys, Marcel Dekker, Inc., New York, NY.
10. Proceedings, Eighth International Ash Utilization Symposium, Volume 2, American Coal Ash
Association, Washington, DC, 1987.
CORROSION

11. Rabeler, R.C., Soil Corrosion Evaluation of Screw Anchors, ASTM STP 1013, Effects of Soil
Characteristics on Corrosion, Edited by V. Chaker and J.D. Palmer, American Society for Testing and
Materials, Philadelphia, PA, 1989.
12. Romanoff, Melvin, Corrosion of Steel Pilings in Soil, part of National Bureau of Standards Monograph
127, NBS Papers on Underground Corrosion of Steel Piling 1962-71, published March, 1972.
13. Romanoff, Melvin, Underground Corrosion, National Association of Corrosion Engineers, Houston, TX,
1989. (Republished from National Bureau of Standards Circular 579, 1957)
14. Suzuki, Ichero, Corrosion-Resistant Coatings Technology, Marcel Dekker, Inc., New York, NY, 1989.
15. Tefankjian, D.A., Application of Cathodic Protection, Proceedings of the 19th Annual Underground
Corrosion Short Course.
16. Uhlig’s Corrosion Handbook, Second Edition, Edited by R. Winston Revie, Electrochemical Society
Series, 2000.
17. West, Edward L., Cathodic Protection of Anchors - A Basic Guide to Anode Selection, A.B. Chance
Bulletin 2-8307, A.B. Chance Company, Centralia, MO, 1983.
18. Winterkorn, Hans F., and Hsai-Yang Fang, Foundation Engineering Handbook, Van Nostrand Reinhold
Company, New York, NY, 1962.
19. Various Cathodic Protection System Vendors.

Page A-26 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 CORROSION

Page A-27 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 LOAD TESTS
APPENDIX B

CONTENTS

STATIC AXIAL LOAD TESTS (COMPRESSION/TENSION)............. B-3

STATIC LOAD TESTS (LATERAL)............................................................ B-9
ACCEPTANCE CRITERIA............................................................................ B-12

SYMBOLS USED IN THIS SECTION

FS ....................................................................................... Factor of Safety B-3
LOAD TESTS

PT............................................................................................... Test Pressure B-3

DL............................................................................................... Design Load B-3
A............................................................................Effective Cylinder Area B-3
AL........................................................................................ Alignment Load B-4
ASTM............................ American Society for Testing and Materials B-6
D........................................................................................................ Diameter B-6

DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to
point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted
prior to any installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption,
revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in
its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of
CHANCE® Civil Construction foundation support products.

Page B-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
STATIC AXIAL LOAD TESTS (COMPRESSION/TENSION)
Pre-Production Load Tests
Load tests shall be performed to verify the suitability and capacity of the proposed helical anchor/
pile, and the proposed installation procedures prior to installation of production helical anchors/piles.
These load tests shall be performed prior to the installation of the production helical anchors/piles. The
Owner shall determine the number of pre-production load tests, their location, acceptable load and
displacement criteria, and the type(s) of load direction (i.e., tension, compression, or both). An additional
purpose of pre-production tests is to empirically verify the ultimate capacity to the average installing
torque relationship of the helical pile/anchor for the project site with the torque measurement equipment
used for the project. Pre-production helical pile/anchor installation methods, procedures, equipment,
and overall length shall be identical to the production helical anchors/piles to the extent practical except
where approved otherwise by the Owner.
It is recommended that any field load test for compression or tension be conducted under the
supervision of a Registered Professional Engineer. The engineer will specify the test and measurement
procedure, load increments, time intervals, and acceptable ultimate displacement consistent with specific
project and load conditions. Test procedures shall conform to ASTM D-1143-07, Standard Test Method for
Pile under Static Axial Compressive Load and/or ASTM D3689-07, Standard Test Method for Pile under
Static Axial Tension Load unless otherwise specified by the engineer. These ASTM specifications do not
specify a particular method to be used, but rather provide several slow-testing and quick-testing optional
methods.

LOAD TESTS
Citing the Canadian Foundation Engineering Manual, 2007:
“The slow-testing methods . . . (outlined by the ASTM D1143-07. . . are very time-consuming. When the
objective of the test is to determine the bearing capacity of the pile, these methods can actually make
the data difficult to evaluate and disguise the pile true load movement behavior, thereby counteracting
the objective of the test. The benefit of the (slow) test methods lies in the additional soil-pile behavior
information, occasionally obtained, which the interpreting engineer can use, when required, in an overall
evaluation of the piles.
“. . . For routine testing and proof testing purposes, the quick methods . . . are sufficient. Where the
objective is to determine the bearing capacity of the pile . . . the quick test is technically preferable to the
slow methods.”
Therefore, the following test procedure is based on the “Quick Load Test Method for Individual Piles”.
This test procedure shall be considered to meet the minimum requirements for load testing. It is not
intended to preclude local building codes, which may require the use of other testing methods as
described in the ASTM specifications..
Pre-Production Load Tests
1. Determine the depth to the target stratum of soil from the geotechnical site investigation report that
includes boring logs. Use these data to select an pile/anchor design capacity, ultimate capacity and
estimate the installation torque at the target stratum and depth.
2. Set the spacing and install the four reaction anchors at the test site (see Figure B-3). The recommended
spacing between the test pile and the reaction anchors is at least 5D, where D = diameter of the largest
helical plate. For tension only tests, the reaction anchors are not required.
3. Install the test helical pile at the centroid of the reaction anchors to the target depth and torque
resistance. For tension tests, install the test anchor at the desired location to the target depth and torque
resistance.
4. Mount the two anchor beams on the four reaction anchors/piles and the reaction beam between the
anchor beams (see Figure B-3). For tension tests, center the reaction beam over the anchor and support
each end of the beam on cribbing or dunnage. The helical reaction piles are not required if the surface

Page B-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
LOAD TESTS

Basic Compression Field Test Set-up

Figure B-3

soils have sufficient bearing strength to support the

cribbing/dunnage under the applied loading without
excessive deflections.
5. Install a load cell, hydraulic load jack, actuator
and pressure gauge. The center hole load jack will
be mounted below the reaction beam for a bearing
(compression) test (see Figure B-3) and above the
reaction beam for an anchor (tension) test. A solid core
hydraulic jack can be used for compression tests.
6. Set the displacement measuring devices. Deflection
measuring devices can include analog dial or electronic
digital gauges (must be accurate to .001”) mounted on
an independent reference beam, a transit level surveying
system, or other types of devices as may be specified by
the engineer.
7. Apply and record a small alignment or seating load,
usually 5% to 10% of the design load. Unless otherwise
Indoor Compression Test defined, the ultimate test load shall be assumed equal
Figure B-4 to 200% of the design load. Hold the seating load
constant for 10 minutes or until no further displacement
is measured.

Page B-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
8. Set the displacement measuring device(s) to zero.
9. Axial compression or tension load tests shall be conducted by loading the helical anchor/pile in step-wise
fashion as shown in Table B-3 to the extent practical. Pile/anchor head displacement shall be recorded
at the beginning of each step and after the end of the hold time. The beginning of the hold time shall be
defined as the moment when the load equipment achieves the required load step. There is a generalized
form for recording the applied load, hold periods, and pile/anchor head deflections provided at the end
of this Section.
10. Test loads shall be applied until continuous jacking is required to maintain the load step or until the test
load increment equals 200% of the design load (i.e., 2.0 x DL), whichever occurs first. The observation
period for this last load increment shall be 10 minutes or as otherwise specified. Displacement readings
shall be recorded at 1, 2, 3, 4, 5 and 10 minutes (load increment maxima only).
11. The applied test load shall be removed in four approximately equal decrements per the schedule in Table
B-3. The hold time for these load decrements shall be 1 minute, except for the last decrement, which shall
be held for 5 minutes. Refer to Acceptance Criteria on page B-13 for acceptable movement criteria.
NOTE: Refer to Helical Pile Load Tests in the Model Specification - Helical Piles for Structural Support at
http://www.abchance.com/resources/specifications for further information regarding load test
equipment, load test setup, dial gauges for monitoring anchor displacement, etc..
Production Load Test Procedures (Optional - As Specified)
1. Follow the test setup procedures listed under Pre-Production Load Test Procedures (Items 1 through 7),

LOAD TESTS
except the maximum test load to be applied to the pile/anchor is the Design Load (DL). (This may be the
only type of load test conducted depending on the conditions.)
2. The Contractor shall perform axial load tests on the number and location of helical piles as specified
by the Owner. At the Contractor’s suggestion, but with the Owner’s permission, tension tests may be
performed in lieu of compression tests up to 1.00 DL for helical piles with sufficient structural tension
capacity. The requirements of Table B-4 may be regarded as a minimum, however, it is not recommended
to test production helical piles to values of up to 2.0 DL unless the helical pile’s failure load is significantly
higher than 2.0 DL. The maximum production helical pile test load shall be determined by the Owner. For
example, ASTM D1143 stipulates testing to 2.0 DL.

PRE-PRODUCTION TEST SCHEDULE, TABLE B-3

PRE-PRODUCTION TEST SCHEDULE
CYCLICAL LOAD INCREMENTS (%DL/100)

Load Increment Hold Period (Min.) Load Increment Hold Period (Min.)

AL 1.0 AL 1.0

0.20DL 4.0 0.50DL 4.0

0.40DL 4.0 1.00DL 4.0
0.60DL 4.0 1.20DL 4.0
0.80DL 4.0 1.40DL 4.0
1.00DL 4.0 1.60DL 4.0
0.75DL 4.0 1.80DL 4.0
0.50DL 4.0 2.00DL 10.0
0.25DL 4.0 1.50DL 4.0
1.00DL 4.0
0.50DL 4.0
AL 5.0
AL = Alignment Load, usually 10% of DL; DL = Design (Working) Load

Page B-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 3. Axial compression or tension load tests shall be conducted by loading the helical pile/anchor in the load
sequence as shown in Table B-4. Anchor/pile head displacement shall be recorded at the beginning
of each step and after the end of the hold time. The beginning of the hold time shall be defined as the
moment when the load equipment achieves the required load step. The observation period for this last
load increment shall be 5 minutes or as otherwise specified. Displacement readings shall be recorded at
0.5, 1, 2, 3, 4, and 5 minutes (load increment maxima only).
4. The applied test load shall be removed in four approximately equal decrements per the schedule in Table
B-4. The hold time for these load decrements shall be 1 minute, except for the last decrement, which shall
be held for 5 minutes. Refer to Acceptance Criteria on page B-13 for acceptable displacement criteria.

STATIC LOAD TESTS (LATERAL)

Helical pile/anchor offer maximum benefits structurally when loaded axially (concentrically) either
in tension or compression. In certain design situations, the anchors/piles may be subjected to lateral
loads and it is important to establish their lateral load capacity. Such applications may include support
for communication equipment platforms, foundations for light poles, and sign standards or use as
foundation systems for modular homes. It is recommended that the field lateral load test on pile/anchor
be conducted under the supervision of a Registered Professional Engineer. The engineer will specify the
test and measurement procedure, load increments, time intervals, and acceptable ultimate deflection
consistent with specific project and load conditions. If the desired ultimate lateral load capacity and test
LOAD TESTS

lateral load capacity results are close, the engineer may choose to increase the diameter of the anchor/
pile shaft and/or use a concrete collar on the anchor/pile head in order to achieve the desired Factor of
Safety. Lateral load tests shall be conducted in accordance with ASTM D-3966-07, standard test method
for piles under lateral load.

PRODUCTION TEST SCHEDULE (OPTIONAL - AS SPECIFIED), TABLE B-4

PRODUCTION TEST SCHEDULE
LOAD INCREMENT HOLD PERIOD (MIN.)
AL 0
0.20 DL 4.0
0.40 DL 4.0
0.60 DL 4.0
0.80 DL 4.0
1.00 DL 5.0
0.60 DL 1.0
0.40 DL 1.0
0.20 DL 1.0
AL 5.0
AL = Alignment Load, usually 10 of DL.
DL = Design (Working) Load

Page B-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Test Procedure
1 . In order to conduct a lateral load test on an
installed pile/anchor, it is necessary to install a
reaction anchor system. The reaction anchor
system consists of helical pile/anchor installed
at a battered angle, and using a test apparatus
setup such as shown in Figure B-5. Once the
reaction anchor system is installed, the test pile/
anchor is installed to the specified estimated
depth and design torque.
2. Threaded steel bar or cable shall be used to
connect the test pile to the reaction anchor
Lateral Load Test Equipment Configuration frame. A hydraulic ram and pressure gauge
Figure B-5
is installed to apply the test load(s) and to
measure the applied force.
3. Set the displacement measuring devices.
Displacement measuring devices can include
analog dial or electronic digital gauges (must
be accurate to 0.001”) mounted on a reference
beam, a transit surveying system, or other type

LOAD TESTS
of device as specified by the engineer.
4. For the load capacity tests, follow steps
7 through 11 in the static axial load tests on
page B-6 & B-7.
5. A failure criterion is often established by
the project engineer and will reflect project
specific conditions. The load versus lateral
Lateral Load Test Apparatus deflection is plotted. Interpretation of
Figure B-6
these results to determine the ultimate and
working lateral load capacities often requires
engineering judgment. Refer to Acceptance
Criteria on page B-14 for acceptable
displacement criteria.

Page B-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 STATIC AXIAL LOAD TESTS (COMPRESSION/TENSION)
Pre-Production Load Tests
Acceptance of the load test results is generally governed by the building code for that jurisdiction and is
subject to review by the structural designer. The structural designer determines the maximum displacement
the structure can withstand without undue loss of function or distress. The acceptance criteria must be
defined prior to conducting the load test.
The load displacement data may be plotted for a quick overview of the results. Figure B-7 shows a sample
test plot. Various building codes have their own acceptance criteria, which is generally a limit on deflection at
the factored load. A fast way to determine the ultimate geotechnical capacity is by use of a technique called
the “intersection of tangents.” This is accomplished by graphically constructing two tangent lines. One line
is drawn tangent to the second “straight line” portion of the load curve, which is beyond the curved or non-
linear portion of the load deflection curve. The other line is drawn tangent to the initial “straight line” portion
of the load deflection curve. The point where the two tangents intersect identifies an estimate of the ultimate
capacity

An example of a Code-based acceptance criteria for

the allowable capacity is the Chicago and New York
City Code, which calls for the design load to be the
LOAD TESTS

lesser of:

1. 50% of the applied load causing a net

displacement (total displacement less rebound) of
the pile of 0.01” per ton of applied load, or
2. 50% of the applied load causing a net
displacement of the pile of 1/2”. Net displacement is
defined as the gross displacement at the test load
less the elastic compression.
Other allowable capacity acceptance criteria include:
Sample Compression Test Load-Deflection Curve
Figure B-7 • Maximum total displacement under a specified
load.
• Maximum net displacement after the test load.
• Maximum displacement under the design load,
or various techniques such as that defined by the
Davisson Method (1973) and shown in Figure B-8.
The recommended acceptance criteria for the
allowable geotechnical capacity for helical piles/
anchors is 1/2 of the applied test load causing a net
displacement (gross displacement less the elastic
compression/tension) not to exceed 0.10 times the
average diameter of the helix plate(s). This is the
acceptance criteria used in ICC-ES Acceptance
Criteria AC358 for Helical Systems and Devices, per
Section 4.4.1.2.
When relatively low foundation capacities are
required, the allowable capacity for helical piles/
Davisson Method for Determining Net Displacement anchors might be based on minimum depth and
Figure B-8 minimum torque criteria. This is similar to what the
New York City code for driven piles up to 30 tons
requires, which is to define capacity by the minimum

Page B-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Axial Compression Load (kip)
0 10 20 30 40 50 60 70 80
0

0.2

0.4
Axial Deflection (in)

0.6

0.8

LOAD TESTS
Type SS5 1-1/2" Square Shaft Screw Pile
1.2 10"-12" Lead Section
12'-0 Overall Length
Installed Torque - 4,000 ft-lb
1.4

ASTM D1143 “Quick Test” Compression Plot

Figure B-9

“blows per foot of set.” The subject of load tests and acceptance criteria are discussed by Crowther (1988)
and may be referred to for a more complete treatment of the subject.
Figure B-9 is a plot of results from a compression “quick test” per ASTM D1143-07 of a 12 ft long, 1-1/2”
square shaft helical pile having 10” and 12” helix plates. It was installed in the residual fine grained soils of
Roanoke, Virginia and tested immediately after installation. The load-displacement curve is completely
below the elastic compression line, indicating no skin friction was acting on the shaft during the test. The
load-displacement curve does not cross the PL/AE + 0.10Dave, which indicates the maximum test load is
less than the ultimate geotechnical capacity of the helical pile.
Figure B-10 is a plot of results from a tension “quick test” per ASTM D3689-07 of a 16 foot long, 1-1/2”
square shaft helical anchor having 8”, 10” and 12” helix plates. It was installed in the residual fine grained
soils of Centralia, MO and tested immediately after installation. The load-displacement curve is completely
above the elastic tension line (red line), indicating no skin friction was acting on the shaft during the test.
The load-displacement curve crosses the PL/AE + 0.10Dave line at approximately 41 kip. The average
installation torque over the last three readings was 3,450 ft-lb. The torque correlation method (Kt) of
capacity prediction says the ultimate geotechnical capacity is 3,450 x 10 = 34,500 lb (34.5 kip), using a Kt
of 10 ft-1 as outlined in Section 6. The tested ultimate geotechnical capacity based on 10% average helix
diameter net displacement is 41 kip. Therefore, the Kt based on the load test is 41,000/3450 = 11.9 @ 12.

Page B-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 3.0

2.5

2.0
Deflection (inches)

1.5

Elastic
Elastic Tension
Tension++ 0.10D
0.01Dave
ave

1.0
LOAD TESTS

0.5

Elastic Tension
0.0
0 5 10 15 20 25 30 35 40 45 50
Load (kip)

ASTM D3689 “Quick Test” Tension Plot

Figure B-10

Production Load Tests (Optional)

Some projects are large enough in size to justify the expense of several production tests. Production tests
are useful to verify helical anchor/pile capacity at multiple locations across the project site, especially
with varying soil conditions. The net displacement of helical anchor/piles at the allowable load (1/2 the
geotechnical capacity) typically ranges between 0.25 inches (25 mm) and 0.5 inches (51 mm) total vertical
movement as measured relative to the top of the helical anchor/pile prior to the start of testing. The Owner
or structural engineer usually determines what the allowable displacement is, and it must be defined prior to
conducting the Production Load Test. Limiting axial net deflections of 1” to 1-1/2” at the ultimate geotechnical
capacity are typical.

Static Load Tests (Lateral)

Acceptance Criteria for Helical Systems and Devices AC358 states the allowable load capacity shall be equal
to half the load required to cause 1 inch (25 mm) of lateral deflection as measured from the ground surface.
The acceptance criteria must be defined prior to conducting the Lateral Load Test. The acceptance criteria
must be realistic in its magnitude so as not to potentially damage the structure. Limiting lateral deflections of
1”+ at the ultimate load capacity have been used on some projects. It is suggested that large lateral loads be
resisted through some other means (such as helical anchors, battered helical piles, or enlarged concrete pile
caps/grade beams).

Page B-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
CHANCE® HELICAL PILE/ANCHOR AXIAL TEST
Project: Date: Sheet of

Anchor/Pile Number: Anchor/Pile: ☐ SS5 ☐ SS150 ☐ SS175

☐ SS200 ☐ SS225. ☐ RS
Helix Configuration: Total Depth:

Time: Start Finish Recorded by:

PRESS LOAD TIME DISPLACEMENT

(psi) (kip) (min)
GAUGE A GAUGE B GAUGE C
(in) (in) (in)

LOAD TESTS

Page B-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 References
1. AC358 Acceptance Criteria for Helical Systems and Devices, ICC-Evaluation Services, June 2013
Revision.

2. ASTM D1143-07, Static Load Test Method for Piles under Static Axial Compressive Load, American
Society for Testing and Materials, Philadelphia, PA.

3. ASTM D3689-07, Standard Test Method for Pile under Static Axial Tension Load, American Society for
Testing and Materials, Philadelphia, PA.

4. ASTM D-3966-07, Standard Test Method for Piles under Lateral Load, American Society for Testing
and Materials, Philadelphia, PA.

5. Canadian Foundation Engineering Manual, Canadian Geotechnical Society, 1985.

6. Crowther, Carroll L., Load Testing of Deep Foundations, John Wiley and Sons, 1988.

7. Davisson, M.T., High Capacity Piles, Department of Civil Engineering, Illinois Institute of Technology,
Chicago, IL, 1973.
LOAD TESTS

Page B-12 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 HELICAL PILES AND ANCHORS

Page C-1 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 HOW TO USE THIS MANUAL - DESIGN OF HELICAL
PILES & ANCHORS A BASIC GUIDELINE FOR DESIGNERS
APPENDIX C

CONTENTS

I. INTRODUCTON..................................................................................... C-3
II. HELICAL PILE CAPACITY.................................................................. C-4
III. DESIGN PROCESS................................................................................ C-5
A. Data Gathering.............................................................................. C-5
HELICAL PILES AND ANCHORS

B. Feasibility......................................................................................... C-5
C. P1, P2, P3 & P4............................................................................... C-6
IV. P4 - GEOTECHNICAL CAPACITY................................................... C-6
V. P1, P2 AND P3 - STRUCTURAL STRENGTH............................... C-10
VI. SUMMARY............................................................................................... C-17
VII. RELIABILITY........................................................................................... C-17
VIII. OTHER TOPICS RELATED TO DESIGN........................................ C-17
IX. HOW TO SPECIFY HELICAL PILES............................................... C-20
X. CONSTRUCTION DOCUMENTS...................................................... C-21

DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted prior to any
installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption, revision, implementation,
use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in its network of installing contractors and
dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of CHANCE® Civil
Construction foundation support products.

Page C-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 How to Use this Manual – Design of
Helical Piles & Anchors:

A Basic Guideline for Designers

Contributors:
Cary Hannon, PE – Vice President of Engineering Foundation Technologies, Inc.
Gary L. Seider, PE – Engineering Manager, Hubbell Power Systems, Inc.

I. INTRODUCTION
This Technical Design Manual (TDM) is a comprehensive collection of information for the express purpose
to educate the practicing engineer in the art of helical pile design. The amount of information is extensive,

HELICAL PILES AND ANCHORS

and we recognize the need to provide a short length “primer” for the busy professional who does not have
the time to read and learn all the comprehensive methods used to design helical piles. The goal of this
“How To” is to bring the design and selection of helical piles and anchors into a short easy-to-follow Guide-
line. This Guideline will provide the design method used every day by the Application Engineering Staffs
at Hubbell Power Systems, Inc. and its authorized Civil Construction Distributors. Citations throughout will
direct the designer where to find the required information in the Technical Design Manual. The result is a
simple step-by-step process culminating in a helical pile design that can then be correctly written into a
project specification.

Page C-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 II. HELICAL PILE CAPACITY
The design method for helical pile capacity is simple. It consists of two limit states criteria; namely the Ul-
timate Resistance and the Serviceability Limit. Serviceability is the behavior of a helical pile at a particular
load that is less than the ultimate resistance. For helical pile design, the Serviceability Limit primarily deals
with limiting the deflection or displacement of the pile at a specified service load. Ultimate Resistance
is the limit state based on the structural strength or the geotechnical capacity of the helical pile, defined
as the point at which no additional load can be applied without failure. For helical pile design, ultimate
resistance typically consists of two elements – the geotechnical capacity and the structural capacity, or
strength. It is more descriptive to refer to structural “strength” of the helical pile components, which is the
approach taken in the TDM.

A. According to the International Building Code (IBC) Section 1810.3.3.1.9, there are four ways to deter-
mine the ultimate resistance of helical piles.

• Method 1: Base resistance plus shaft resistance of the helical pile, where the base resistance is
equal to the sum of the areas of the helical bearing plates times the ultimate bearing resistance of
the soil or rock comprising the bearing stratum, and shaft resistance is equal to the frictional resis-
HELICAL PILES AND ANCHORS

tance of the soil times the shaft area above the helix bearing plates. This is commonly referred to
as the theoretical geotechnical limit state method. It is described in great detail in Section 5 of the
TDM.
• Method 2: Ultimate capacity determined from well documented correlations with installation
torque. This is commonly referred to as the empirical geotechnical limit state method. The key
words are “well documented” which will be discussed later. Torque correlation is described in Sec-
tion 6 of the TDM.
• Method 3: Ultimate capacity determined from load tests. This is the most direct method to de-
termine the geotechnical capacity of any pile, not just helical piles. Load testing of helical anchors
and pile is described in Appendix B of the TDM.
• Method 4: Resistance of the pile’s structural elements (shaft, helix, couplings, connection to struc-
ture). Structural strength is described in Sections 5 & 7 of the TDM.

Of the four methods above, the only one that is unique to helical piles is Method 2, commonly referred
to as torque correlation.

B. According to IBC Section 1810.3.3.1.9, the geotechnical capacity (Methods 1, 2, or 3 above) shall not
exceed the strength of the pile’s structural elements (Method 4); including the pile connection to struc-
ture, pile shaft, pile shaft couplings, and the helix bearing plates. The structural strength of CHANCE
brand helical piles is described in Section 7 of the TDM.

C. Therefore, both the geotechnical capacity and the structural strength of the helical pile must be deter-
mined; and whichever limit state is the lesser, will control the capacity. This is the ultimate resistance
of the helical pile. In most cases, the geotechnical capacity will be the limit state, but the structural
strength can sometimes control.

D. Allowable Strength Design (ASD) or Limits States Design (LRFD). ASD has been used for many years
for the geotechnical capacity of deep foundations. It is sometimes referred to as deterministic design
since the factor of safety is determined based on standard practice. LRFD is sometimes referred to
as probabilistic design. It uses load factors and resistance factors based on statistically based prob-
abilities of uncertainty. In the United States, most geotechnical design is deterministic based (global
factor of safety); whereas in Canada most geotechnical design is probabilistic (limit states – ULS, SLS).
The TDM includes both LRFD design and ASD allowable strength values, so the design can use either
design method.

E. The Serviceability Limit may also control. Serviceability is the load/deflection response of a helical pile
at a particular load of interest, i.e. a factored load well below the ultimate resistance limit state. There
may be strict deflection limits required based on the application; the structure may be sensitive to
overall settlement or differential settlement, which may require the helical pile ultimate resistance to
be increased. For example, a deflection limit may be specified at the working/design load. Cherry and
Perko (2012) reviewed hundreds of tension and compression load tests. They suggested that for end-

Page C-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 bearing helical anchors/piles, the net displacement of the helix plates at the working loads averaged
about 0.25 in (6.4mm). The working load is based on the geotechnical capacity divided by a factor of
safety of 2 (deterministic design). CHANCE application engineers have either conducted or reviewed
the results of several hundred load tests, which support the findings of Cherry and Perko. Serviceabil-
ity limits should also take into account the elastic response of the helical pile material, which can be
significant for deep piles with slender shafts.

III.DESIGN PROCESS
The designer has a specific task to perform, or problem to solve to which helical piles can offer a solution.
At the beginning of the design process, it is best to keep all options on the table until circumstances dic-
tate one foundation option(s) as being the better choice for the client. The designer should always keep
in mind the client is best served with a good solution at a reasonable price, both of which are not always
intuitively obvious. As with any deep foundation, helical pile design has several steps. The steps can be
summarized as:

A. Data Gathering:

HELICAL PILES AND ANCHORS

• The loads applied to the foundation. Section 4 of the TDM is a brief review of structural loads and
provides several tables that can be used to estimate dead and live loads for various residential &
commercial structures. If applicable, lateral loads must be included.
• The description and strength characteristics of the project soils. See Section 2 of the TDM for a
brief review of soil mechanics and the procedures used for site investigations, which are typically
summarized in the geotechnical report. Information needed in the geotechnical report includes:
soil profile, Nspt values per ASTM D-1586, depth to ground water, the presence of fill, debris, or
cobbles, and bedrock.
• The designer must determine load resistance requirements and serviceability based on the applica-
tion. This includes choosing either ASD with a deterministic factor of safety, or LRFD with probabi-
listic load and resistance factors. Section 5 for the TDM provides guidelines to evaluate soil prop-
erties for foundation design, and also gives estimates of helical pile displacement at working loads.
Section 5 also provides the design methodology used with HeliCAP®, which is the design software
most often used to determine the axial capacity of helical piles.
• The applicability of local, regional, or national building codes. The designer must comply with
code requirements depending on the jurisdiction. For example, some codes require helical piles
to be tested for every project. Others only require load tests if the pile capacity is above a certain
limit. Codes often dictate acceptance criteria in terms of allowable displacement for deep founda-
tions, such as the City of Chicago and New York building codes.
• Location tolerances. The helical pile designer must understand the location tolerances for the
piles. For example, most CHANCE helical piles can be installed to a location tolerance of 1 inch or
less, and an elevation tolerance of 1/8 inch. Angular tolerances are typically less than 2°.

B. Feasibility:

• Helical piles are designed to transfer load to soil or bedrock with a reasonable displacement. How-
ever, they are not designed to drill into solid rock. Table 7-4 on page 7-12 is a quick reference guide
for feasibility. It lists helical pile type based on the upper limit Nspt range of soils that pile type can
be installed into, along with the typical upper limit of ultimate resistance. It’s a good place to start
for helical pile feasibility. For example, Type RS2875.276 2-7/8” OD pipe shaft helical piles can be
installed into soils with Nspt blow counts up to 35 bpf.
• The size (diameter) of the helical pile shaft should be closely tied to its application. CHANCE of-
fers small displacement (up to 4 in.), medium displacement (4 in, to 8 in.), and large displacement
(> 8 in) helical piles. The pile shaft should be large enough to transfer the axial and lateral loads
to the soil. However, it is detrimental to oversize the helical pile shaft. This is because of torque
correlation – the relationship between the amount of torque energy required to install a helical pile
and its load capacity. Smaller diameter helical piles more easily advance like a screw, which mini-
mizes soil disturbance and increases capacity efficiency. More information about shaft type and
size will be presented later.

Page C-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 • Project site factors such as equipment access, overhead clearance, right-of-way restrictions, spoils
disposal, noise restrictions, etc. must be considered. This is often where helical piles turn out to
be the most cost effective deep foundation. Small equipment results in low mobilization cost and
easy access.
• Manageable schedule must be considered as well. Helical piles and anchors can be loaded immedi-
ately after installation, which can save time compared to waiting for concrete or grout to cure.

C. It is convenient to break down the geotechnical capacity and the structural strength into subcategories
or groups. For helical piles and anchors the groups are:

• P1 – bracket or connection to structure

• P2 – shaft, including couplings
• P3 – Helix(s)
• P4 – Soil (geotechnical) capacity, including resistance to both axial and lateral loads

We recommend the design sequence be inverted – start with P4 – soil (geotechnical) capacity because
it usually will control the ultimate resistance.
HELICAL PILES AND ANCHORS

IV. P4 – GEOTECHNICAL CAPACITY:

The axial and lateral capacity is determined per the methods detailed in Section 2 and Section 5 of the
TDM. Installation torque requirements can be estimated at this point. If a geotechnical report is available,
use HeliCAP® v2.0 Helical Capacity Design Software to determine the axial capacity (tension, compression,
or both) via bearing capacity on the helix plates and side resistance on the shaft [Method 1]. HeliCAP®
will help determine the shaft type (square shaft, pipe shaft, Combo Pile, or grouted PULLDOWN Pile), shaft
size (diameter), pile depth, helix configuration (number and size of helix plates), and estimate the torque
required to install the pile.

If a geotechnical report is not available, then axial capacity must be determined by other methods. Heli-
cal piles have the advantage of being installed (screwed) into the ground and then removed (unscrewed)
quickly. A “probe” helical pile can be installed to assess the relative shear strength of the soil profile using
torque correlation relationships per TDM Section 6. Well documented correlations with torque are used
to estimate helical pile capacity based on the torque measured with the probe pile [Method 2]. The shaft
type, shaft size (diameter), pile depth, helix configuration can be determined based on the probe pile.

The axial capacity can also be determined from full-scale load tests per Appendix B of the TDM [Method
3]. Full-scale tests are often used to verify Method 1 capacity and Method 2 torque correlation.

If a geotechnical report is available, the lateral capacity of a vertical shaft can be determined with vari-
ous methods including the Finite Difference method (LPILE & GROUP by Ensoft®) and the Broms’ Method
(1964a) and (1964b) as detailed in Section 5 of the TDM [Method 1]. Each of these methods may be ap-
plied to Round Shaft helical piles or PULLDOWN® Micropiles. Lateral resistance can also be provided by
passive earth pressure against the structural elements of the foundation. The resisting elements of the
structure include the pile cap, grade beams and stem walls. The passive earth pressure against the struc-
tural elements can be calculated using the Rankine Method. Battered or inclined piles can be used to resist
lateral loads by components of the axial capacity on the battered pile. The induced shear and moment in
battered piles often dictates the shaft size and batter angle.

If a geotechnical report is not available, the lateral capacity of a vertical shaft must be determined from
load tests per Appendix B of the TDM [Method 3].

P4 SHAFT Type and Size:

The shaft type/size is critical to both the axial and lateral capacity – especially for compression in soft/
loose overburden soils where lateral stability of the shaft must be considered. The following is a brief sum-
mary of the 4 different shaft types for helical piles.

Page C-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
• Type 1 - Square Shaft: Square shaft piles are foundation elements that range in size from 1-1/2” solid
round-cornered-square (RCS) to 2-1/4” solid RCS. They are compact sections, meaning they have rela-
tively low section properties, but relatively large cross-sectional area since they are solid bars. They
are more efficient than pipe shaft helical piles in regards to axial capacity derived from installation
energy. A square shaft helical pile will have more axial capacity than a pipe shaft helical pile installed
with the same amount of torsional energy into the same soil profile. Therefore, square shaft helical
piles are better at penetrating dense material than pipe shaft helical piles.

Square shaft piles have slender cross sections. Therefore, they do not have a large cross section to
resist much lateral load via passive earth pressure along the side of the shaft. In addition, they do not
have much section modulus/ stiffness to resist buckling under compressive loads without support from
the surrounding soil. As long as there is sufficient soil confinement around the pile to prevent buck-
ling, square shaft piles are suitable for compressive loads. As a general rule, if the soil profile has ASTM
D-1586 SPT N60 value of 5 or greater, there is sufficient lateral support to prevent the square shafts
from buckling at the compressive loads that they are rated for. If SPT N60 values are 4 or less, then
square shaft buckling may be a practical concern. A rigorous analysis can be done if enough reliable

HELICAL PILES AND ANCHORS

soil data is available, but the problem is best solved by selecting either a pipe shaft or Helical PULL-
DOWN Micropile as described in the following sections.

The designer is encouraged to use square shaft helical piles as much as possible due to their advan-
tages with torque correlation efficiency and better penetration in dense soil.

• Type 2 – Pipe Shaft: Pipe shaft piles are foundation elements that range in size from 2-7/8” OD pipe
shaft to 10-3/4” OD pipe shaft with various wall thicknesses and material strengths. Pipe shaft piles
have larger section properties compared to square shaft, so they are used to resist lateral load, or to
provide stability when columnar buckling or potential unsupported length is a concern. The designer
may ask why not use pipe shaft helical piles exclusively? The answer is square shaft helical piles offer
greater axial capacity for a given amount of installation energy due to their greater efficiency (see the
torque correlation table C-1 below). In addition, pipe shaft helical piles do not penetrate dense material
as effectively as square shaft. Therefore, the designer must size the helical pile shaft large enough to
transfer/resist all loads, but no larger than necessary. Helical piles evaluated per ICC-ES AC358 comply
with the requirement of International Building Code (IBC) Section 1810.3.3.1.9 for the use of “well docu-
mented” correlations with installation torque.

Helical piles, whether they are square shaft or pipe shaft, are generally considered to be slender mem-
bers. The lateral capacity is dependent on the effective projected area of the pile shaft, the flexural
stiffness of the pile, and the resistance of the soil as the pile deflects laterally under load. Due to their
slender size, helical pile shafts have relatively small effective projected area for the soil to bear against.
Therefore, helical piles with shaft diameter ≤ 4” have about 4 kip lateral resistance; shaft diameters ≤
8” have about 10 kip lateral resistance; and shaft diameters ≤ 10” have about 20 kip lateral resistance at
typical allowable lateral displacements of 1” or less. As mentioned previously, square shaft helical piles
don’t have any significant lateral capacity.

Page C-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 Table C-1
PRODUCT SE- EVALUATED PER
DESCRIPTION Kt
RIES AC358
1.25” ROUND CORNERED SQUARE
SS125 10
BAR
1.50” ROUND CORNERED SQUARE
SS5 YES 10
BAR
1.50” ROUND CORNERED SQUARE
SS150 10
BAR
1.75” ROUND CORNERED SQUARE
SS175 YES 10
BAR
2.00” ROUND CORNERED SQUARE
SS200 10
BAR
2.25” ROUND CORNERED SQUARE
SS225 10
BAR
RS2875.203 2.875” OD, 0.203 WALL PIPE YES 9
HELICAL PILES AND ANCHORS

RS2875.276 2.875” OD, 0.276 WALL PIPE YES 9

• Type 3 - Combo Pile: A combo pile (Combination Pile) is a compression helical pile that has the advan-
tages of both square shaft and pipe shaft. A combo pile has a square shaft lead section that is better
at penetrating dense material and generating bearing capacity; and is then transitioned to a pipe shaft
for the plain extensions where over- burden soils are softer/less dense and a larger section modulus is
desired for lateral stability and/or buckling resistance, or when lateral load resistance is required. An-
other advantage provided by combo piles is the torque correlation factor (Kt) is increased compared
to the straight pipe shaft pile per the table below. Note as the overall shaft length increases, the Kt fac-
tor decreases.

Table C-2 - Combo Pile Length Less than 30’-0

COMBO PILE TYPE SAND CLAY COMBINED
SS5/150/RS2875 10 9.5 10
SS175/RS3500 9.5 9 9
SS200/RS3500 9.5 9 9

Table C-3 - Combo Pile Length Greater than 30’-0

COMBO PILE TYPE SAND CLAY COMBINED
SS5/150/RS2875 9.5 9.5 9.5
SS175/RS3500 9 8.5 8.5
SS200/RS3500 8.5 8 8

• Type 4 - A Helical PULLDOWN Micropile is a helical pile that has the shaft section encased in a small
diameter grout column, typically 5” – 7” in diameter. Both square shaft and pipe shaft helical piles can
be encased in a grout column, but square shaft is much more common. It has the advantage of the
square shaft lead section to penetrate dense material for end-bearing. The added grout column pro-
vides greater section properties for shaft stability and lateral resistance in soft soils. Lateral load resis-
tance with grouted shafts requires a steel case – typically extending 5’-0 to 10’-0 from the pile head.
The grout in contact with the soil will develop side resistance via a bond zone in suitable soil stratum.
This can greatly increase the total axial capacity of the pile (end-bearing and side resistance) as well as
stiffen the axial load response of the pile. The grout column also provides additional corrosion protec-
tion to the steel shaft.

Grouted shaft Helical PULLDOWN Micropiles are recommended for square shaft piles in soft soils,
when additional capacity via side resistance is needed, or when working loads exceed about 60 kip.
To-date, Helical PULLDOWN Micropiles have achieved 450 kip ultimate resistance.

Page C-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
P4 Other Considerations:
There are several design considerations that should be taken into account when choosing the required
shaft type. This is often the most important aspect of specifying a helical pile and too often receives the
least amount of attention prior to installation.

1. Is the shaft section sufficient to carry the intended axial load? This will have a great deal to do with the
selection of the shaft type. Refer to Table 7-4 of the TDM as a good place to start. It lists torque cor-
related capacities for shaft diameters up to 4.5” OD [Method 2]. Large diameter pipe shaft (≥ 6”) and
PULLDOWN Piles can achieve higher capacities than those listed in Table 7-4. Allowable load upper
limit for CHANCE helical piles up to 10” nominal diameter is 100 ton. Tension capacity is controlled by
the structural strength of the couplings as detailed in P2 below.

2. The helix plates must generate the downward thrust required to advance the shaft through the soil.
Helical piles (i.e. screw piles) are displacement piles that have the advantage of no spoils. The soil that
is displaced by the shaft during installation is displaced to the side. The smaller the shaft size relative
to the diameter of the helical plates (higher aspect ratio), the more efficient the pile will be in regards
to capacity derived from the same installation energy. A helical pile that has a smaller shaft size rela-

HELICAL PILES AND ANCHORS

tive to the size of the helical plates will be better at penetrating dense soil than one with a larger shaft
size relative to the size of the helical plates (lower aspect ratio). Displacing more soil will require more
installation energy, i.e. additional installation torque and down pressure. The greater the installation en-
ergy, the larger the required equipment to install the pile. For example, a 25 ton allowable load square
shaft helical pile can be installed with a mini-excavator or skid-steer. However, an 8” diameter pipe
shaft helical pile requires a 20 to 25 ton track-hoe excavator.

3. If a soil stratum is too dense, or the shaft too large relative to the size of the helix plates, the pile could
“spin-out”. “Spin-out” means that the pile is still being rotated but is not advancing, and installation
torque drops dramatically. This is similar to “stripping” a screw. The capacity-to-torque correlation
is no longer valid for spun-out piles. (Note: see Section 6 – Installation Methodology of the TDM for
a complete explanation of torque correlation for helical anchors and piles). A spun-out pile is just an
end bearing pile that was advanced to depth via a screw mechanism. This does not mean that the pile
has no capacity, but rather that the capacity cannot be estimated by torque correlation as is normally
done for a normally installed helical pile. The pile’s capacity will depend on the type of material the
helical plate(s) are in, how much the soil was disturbed, and whether or not the shaft tip, or pilot point,
contributes to the capacity in end bearing. High capacities can be possible if the shaft tip is sitting on
rock.

4. Lateral resistance requires either pipe shaft or Helical PULLDOWN Micropiles. A Helical PULLDOWN
Micropile with a steel casing at the top of the pile will offer the stiffest pile section and the most resis-
tance to lateral loads. Lateral capacity ranges from 2 to 4 kip for 3” to 4” diameter piles, 10 kip for 6”
to 8” diameter helical piles, and up to 20 kip for 10” diameter piles at allowable lateral displacements
of 1” or less. The use of battered (inclined) piles can be utilized to resist lateral loads if needed and are
discussed in Section 5 of the TDM.

5. For tension only foundation elements, square shaft is always the logical choice. As noted above, square
shaft helical anchors are more efficient in regards to load capacity versus installation energy (torque
correlation), are better at penetrating dense soils, and have less surface area for corrosion potential.
The size and strength of the square shaft section is governed by the required installation torque, not
the tension capacity. There is more steel section available than is required to carry the rated axial ten-
sion load. The reason for this is because the steel in the shaft is subjected to more stress during instal-
lation than it will ever see while in service. Once the helical anchor is installed, the tension strength is
governed by the shear strength of the coupling bolt – see Section 7 of the TDM.

Page C-9 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 6. For piles required to resist compression and tension loads, the designer must recognize that helical
piles are a pre-manufactured product with bolted connections. There is manufacturing tolerance in
each connection. For example, most helical piles have up to 1/8” axial tolerance in each connection.
The tolerance is required to ensure the connections fit together in the field. If the load reverses, the
top of the pile will displace (up or down) a distance equaling the sum of the bolt tolerance in all of the
bolted connections before it can resist the reversed load. This may or may not be of concern to the
designer and is dependent on the type of structure that is being supported with the piles. The grout
column of Helical PULLDOWN Micropiles fills the connections, thereby removing the bolt tolerance as
well as stiffening the axial load response. That is why grouted shafts are often utilized for piles with
reversing load conditions. Grouting the ID of pipe shaft helical piles will also stiffen the coupling for
reversing load conditions. Pipe shaft piles with couplings above grade should be grout filled to stiffen
the connection.

V. P1, P2 AND P3 – STRUCTURAL STRENGTH:

The axial and lateral strength of the helical pile components (shaft, helix and connection to structure) is
HELICAL PILES AND ANCHORS

determined per the methods detailed in AISC 360-10 Steel Construction Manual and Chapter 18 of the
International Building Code (IBC). The structural strength of CHANCE helical piles is detailed in Section
7 of the TDM [Method 4]. The factors required for structural design are soil strength (firm, soft, fluid),
the strength of the concrete, end condition (pinned, fixed, free), Application (new construction, remedial
repair, tiebacks), coupling strength, and load direction (tension, compression, or both).

Soil strength is an important factor because it affects buckling & bracing of helical piles. It is important
to categorize the project soils as either “fluid” (N=0), “soft” (0<N<5) or “firm” (N≥5) as detailed in Sec-
tion 5 of the TDM. If the soil is “fluid”, then buckling is possible and the shaft size is determined based on
the critical buckling load. Examples are provided in Section 8 of the TDM (Examples 16, 17 & 18). If the
soil is “soft” or “firm” buckling is not the concern, but depth to fixity and lateral support is. The term “fully
braced” is used by some in the industry to describe a pile shaft with complete soil confinement all the way
from the pile head to the tip. However, Hubbell Power Systems Inc. application engineers believe the term
“fully braced” is unachievable from a practical standpoint. A “fully braced” condition is not listed as an
option in Section 7 of the TDM since it is considered unrealistic and ensures the capacity of the helical pile
will better match long term performance. Therefore, Section 7 details the nominal, LRFD design and ASD
allowable compression strength of helical piles in terms of “firm soil” [5’-0 depth to fixity] and ”soft soil”
[10’-0 depth to fixity].

Once the soil strength is determined, the designer must now consider the end condition (K) at the pile
head and how it affects the effective length of the pile shaft. The connection to the structure (and the
effective length) greatly affects the structural capacity of the pile. A pinned condition means the pile
head is restricted against lateral translation (side to side movement) but is free to rotate as shown in Table
C-C2.2 (b) below from AISC 360-05. A pinned condition uses a K of 0.7. A fixed condition mean the pile
head is restricted against both lateral translation and rotation as shown in Table C-C2.2 (a) below. A fixed
condition uses a K of 0.5. To achieve a fixed end condition, the pile head has to be embedded at least 7.5”
from the bottom of a concrete pile cap/footing/grade beam. Anything less than that is typically consid-
ered pinned. A pile with a fixed end condition has a shorter effective length, thereby having a greater
stability and higher axial compressive strength. The compressive strength of a “free” headed helical pile
(Table C-C2.2 (e) is not provided in the TDM. It can be provided as needed using a K factor of 2.0.

Page C-10 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
Table C-C-2.2 - from AISC 360-05

HELICAL PILES AND ANCHORS

The strength of the concrete will also factor into the axial compressive strength of helical piles. Higher
strength concrete results in higher bearing pressure with both embedded new construction pile caps (P1)
and foundation repair brackets (P1).

Helical piles can be one-piece foundation elements, but are more commonly produced in sections that
are coupled together during installation. Therefore, the strength of the coupling must be considered in
the design as part of the shaft (P2). CHANCE helical pile couplings are designed to meet or exceed the
torque correlated geotechnical capacity [Method 2]. They are also designed to meet or exceed the bend-
ing strength of the shaft itself. Structurally, the couplings limit both the tension and compression strength.
For CHANCE Type SS helical piles, the coupling bolt is the limiting factor for tension strength.

Load direction is an important consideration and strongly affects the shaft type and size required. This
was discussed previously under P4. The Application (new construction, foundation repair, earth retention,
etc.) also affects the shaft type and size required. For example, it is not practical to use large diameter
shaft helical piles for underpinning existing building structures.

Page C-11 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 Section 7 is broken down by specific helical pile product families. Each family sub-section lists the tension
and compression strengths in various tables, in addition to specifications and available configurations. For
example, the P2 (shaft) strength and P4 (geotechnical) tension capacity for Type SS175 helical piles are
shown below.

Table C-3 - SS175 - P2 Tension Strength and P4 Torque Correlated Capacity

HELICAL PILES AND ANCHORS

The pre-qualified and verified torque correlation factor (Kt) is 10 for Type SS175. The torque rating for
SS175 is 10,500 ft-lb. Therefore, per P4 [Method 2], the torque correlated capacity limit for SS175 is 105
kip (see Section 6 TDM). The nominal strength of Type SS175 shaft (P2) is limited to 100 kip by the shear
strength of the coupling bolt. Comparing the two, 105 kip > 100 kip, therefore P2 tension strength controls
at max torque. If the installation torque is less than 10,000 ft-lb, then P4 [Method 2] will control. The al-
lowable geotechnical capacity of 52.5 kip is based on a deterministic factor of safety of 2.

It is convenient to tabulate axial compression strength in terms of either P2 (shaft) & P3 (helix), or P1
(bracket) & P2 (shaft). The table below from Section 7 of the TDM lists the P2 (shaft) and P3 (helix) ASD
allowable strengths for Type SS175 square shaft helical piles. It is used to easily determine P2 and P3,
which can then be compared to P4 to see which will control the design. The table is broken down by soil
type, end condition, and number/diameter of the helix plates.

Table C-4 - SS175 - P2 Shaft Compression Strength and P3 Helix Strength in Firm or Soft Soil

Page C-12 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
For example, a Type SS175 helical pile in firm soil & fixed end condition with multi-helix plates (3 or more
plates) has ASD allowable compression strength of 98.3 kip. However, that exceeds the P4 geotechnical
allowable capacity of 52.5 kip. But if the soil is soft with the same fixed end condition, the ASD allowable
compression strength is 30.2 kip; which is less than the P4 geotechnical allowable capacity of 52.5 kip.
The difference is the depth to fixity, which is 5’-0 in firm soils and 10’-0 in soft soils.

The table below from Section 7 of the TDM lists the P1 (new construction bracket) and P2 (shaft) ASD
allowable strengths for Type SS175 helical piles. It is used to easily determine P1 and P2, which can
then be compared to P4 to see which will control the design. The table is broken down by concrete
strength, soil type and end condition.

Table C-5 - SS175 – P1 Pile Cap Compression Strength and P2 Shaft Compression Strength in
Firm and Soft Soils

HELICAL PILES AND ANCHORS

For example, a Type SS175 helical pile in firm soil & fixed end condition with a new construction cap em-
bedded in 2500 psi concrete has an ASD allowable compression strength of 52.7 kip based on the strength
of the cap (P1). The P4 geotechnical allowable capacity of 52.5 kip is basically the same. But if the soil is
soft with the same fixed end condition, the ASD allowable compression strength is 30.2 kip based on the
shaft strength; which is less than the P4 geotechnical allowable capacity of 52.5 kip. Again, the difference
is the depth to fixity, which is 5’-0 in firm soils and 10’-0 in soft soils.

The table below from Section 7 of the TDM lists the P1 (remedial repair bracket) and P2 (shaft) ASD al-
lowable strengths for Type SS175 helical piles. It is used to easily determine P1 and P2, which can then be
compared to P4 to see which will control the design. The table is broken down by concrete strength and
soil type. CHANCE Remedial Repair Brackets provide fixed end condition at the bracket-shaft connection.

Table C-6 - SS175 – P1 Repair Bracket Compression Strength and P2 Shaft Compression Strength
in Firm and Soft Soils

Page C-13 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 For example, a Type SS175 helical pile in firm soil with a remedial repair bracket connected to an existing
2500 psi concrete footing has an ASD allowable compression strength of 36.8 kip based on the strength
of the repair bracket (P1). The P4 geotechnical allowable capacity of 52.5 kip is greater, which means the
bracket strength controls the design. This is also true if the soil is soft; the ASD allowable compression
strength is 27.7 kip based on the bracket strength. The allowable load for remedial repair brackets is less
because of the eccentric compressive load. Note from the table above the allowable strength can increase
with stronger concrete.

Note from Table C-4 above that the allowable shaft (P2) compressive strength for SS175 in soft soils is sig-
nificantly less than the torque correlated (P4) capacity. That is one reason why pipe shaft or grouted shaft
helical piles are used.

The table below from Section 7 of the TDM lists the P2 (shaft) and P3 (helix) ASD allowable strengths for
Type RS3500 3-1/2” OD pipe shaft helical piles. It is used to easily determine P2 and P3, which can then
be compared to P4 to see which will control the design. The table is broken down by soil type, end condi-
tion, and number/diameter of the helix plates.
HELICAL PILES AND ANCHORS

Table C-7 – RS3500 - P2 Shaft Compression Strength and P3 Helix Strength in Firm or Soft Soil

For example, a Type RS3500 helical pile in firm soil & fixed end condition with multi-helix plates (3 or more
plates) has ASD allowable compression strength of 76.6 kip. But the ASD allowable compression strength
in soft soil is either 65.9 kip with a fixed end condition, or 54.3 with a pinned end condition. These ASD
allowable strengths are much higher than for SS175 in soft soil, which are 30.2 kip and 15.4 kip with fixed
and pinned end conditions respectively. The P4 torque based geotechnical allowable capacity for RS3500
is 45.5 kip, which is less than the structural strength of RS3500 for any combination of soil type and end
condition and thus controls the design. This is why SS/RS Combo piles are a good choice in soft overbur-
den soil conditions.

Another way to increase structural strength is with grouted shaft Helical PULLDOWN Micropiles per Table
C-7 below. The grout column increases the section modulus, which in turn increases the axial compression
strength. Another benefit of the grout column is increased axial capacity (P4) base and shaft resistance,
due to the soil-grout bond [Method 1].

Page C-14 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
Table C-8 – SS175 Grouted Shaft in Soft Soils P2 Shaft Compression Strength

For example, an SS175 helical pile with a 5” diameter grout column more than doubles the ASD allowable
compression strength of the P2 shaft. Larger grout columns increase the structural strength even higher.
This is an example where torque correlation [Method 2] does not limit the (P4) geotechnical capacity.

HELICAL PILES AND ANCHORS

Base and side resistance [Method 1] calculated with HeliCAP® v2.0 Helical Capacity Design Software is
often greater than strictly torque relationships.

The helix strength (P3) is best determined directly by testing. The photos below (courtesy of CTL | Thomp-
son) show how the helix strength can be determined. The load is applied through the shaft and resisted
by the helix shaped fixture. The line of bearing is located at the average helix radius. The load is applied
until the helix plate closes or the welds fail due to bending and shear. The test is stopped when the applied
load begins to drop off. The maximum test load is considered the ultimate strength of the helix.

Fig. C-1 – P3 Helix Strength Set-Up Fig. C-2 – RS2875 14” Dia. Helix – Test Results

Page C-15 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 Table C-9 – SS175 P3 Helix Strength

The allowable helix strength (P3) must equal or exceed the end-bearing capacity (P4) of the of the helix
plates. It is possible for the bearing capacity of a helix plate to exceed the structural strength of the helix
plate For example, an SS175 10” diameter helix plate has an allowable strength of 33.1 kip per Table C-9
above. If the maximum allowable torque based capacity of an SS175 helical pile (52.5 kip) is needed, then
more than one 10” helix is required to meet structural strength requirements since 33.1 kip is less than
52.5 kip. A twin-helix or triple-helix configuration will work. This is an example where the designer may
HELICAL PILES AND ANCHORS

want to specify a minimum number of helix plates in the project plans.

As helix plate diameter increases, the helix strength (P3) generally decreases. This is because the line
of bearing (average radius) increases with increasing diameter, which in turn increases the moment arm
distance. The increased distance increases the bending forces at the helix/shaft welded connection.

Load tests [Method 3] are used to verify the feasibility and capacity of helical piles/anchors and are de-
scribed in detail in Appendix B of the TDM. They can be part of a pre-production test program where at
least one helical pile is installed and tested to determine the ultimate resistance and the load/deflection
response. Project requirements may also require production tests on a specified number of helical piles/
anchors to ensure capacity and performance requirements are being met. It is VERY IMPORTANT that
the performance requirements be clearly specified BEFORE the start of work. It should be part of the
data gathering process and feasibility assessment for helical piles. Helical piles are primarily end-bearing
foundation elements, meaning they derive most of their resistance with the helix plates transferring load
to the soil at the pile tip. Therefore, the load/deflection response of a helical pile at a particular load
(serviceability) must take into account the section modulus and length of the shaft. The designer must
understand that long end-bearing piles will displace more than short end-bearing piles because of the
pile length.

The recommended acceptance criteria for the allowable capacity of helical piles/anchors is 50% of the
applied test load causing a net displacement equal to 10% of the average helix diameter. This means that
total displacement of the pile/anchor may exceed 1 inch in order to fully mobilize the bearing capacity of
the helix plates. This is the acceptance criteria used in ICC-ES Acceptance Criteria AC358 for Helical Sys-
tems and Devices, per Section 4.4.1.2. It can be expressed mathematically as PL/AE + 0.10Dave, where
“PL/AE” is the elastic shortening or lengthening of the pile shaft under load. As mentioned previously,
the net displacement of the helix plates at allowable loads will average 0.25 in (6.4mm) ± 0.12 in when us-
ing a geotechnical factor of safety of two.

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VI. SUMMARY:
In summary, helical pile design determines the geotechnical resistance (P4) and structural capacity (P1, P2,
& P3), typically in that order. Probe helical piles and load tests are often done before start of work when
a geotechnical report is not available or when verification of capacity is required. The geotechnical and
structural resistance are separate limit states and whichever one is the lesser will control the design. In
most cases, the geotechnical resistance (P4) will be the controlling factor. The designer is encouraged to
design helical piles so that the geotechnical resistance (P4) controls to make the most efficient use of the
soil’s ability to bear load. This often means choosing the right shaft type/size, end condition, and helix
configuration to maximize capacity.

VII. RELIABILITY:
Reliability is an important aspect of helical pile design. Reliability is defined as the probability of long-
term satisfactory performance. The better the capacity prediction method(s) used, the greater the reli-
ability. Hubbell Power Systems, Inc. recommends using base plus shaft resistance [Method 1] and torque
correlation [Method 2] to determine capacity whenever possible. Perko 2009 did a statistical analysis of

HELICAL PILES AND ANCHORS

helical pile capacity in order to check the reliability of this approach. He used a database of several hun-
dred load tests in the analysis and used a factor of safety of 2 to determine a safe allowable load (deter-
ministic approach). Using bearing capacity theory, the load test data suggests that 1 out of 10 helical piles
will exhibit unsatisfactory performance. That is a 90% success rate, but still means 10% will have unac-
ceptable performance. Using torque correlation, load test data suggests that 0.3 out of 10 will exhibit
unsatisfactory performance. That’s a 97% success rate which is much better, but still means that 3% will
have unacceptable performance. Methods 1 and 2 are independent methods used to determine helical pile
capacity. When two independent methods are statistically combined, the result of poor helical pile per-
formance drops to only 3 piles out of 1000, or 0.3%. That is a 99.7% success rate, which most engineers
agree is acceptable reliability. Loads tests [Method 3] is another independent method of capacity predic-
tion which can be used when soil data is lacking or uncertain, or when soil conditions change.

VIII. OTHER TOPICS RELATED TO DESIGN:

Corrosion Potential: Underground corrosion is discussed in detail in Appendix A of the TDM. In most
ground conditions, corrosion is not a practical concern for deep foundations, including helical piles. There
is typically little to no oxygen in undisturbed soils, especially below the ground water table. Driven steel
piles have been installed with pile hammers for more than a century and are still commonly used today.
The vast majority of interstate highway bridges in the Piedmont regions of the southeast United States
are bearing on driven steel H-piles. If the geotechnical report declares the corrosion potential is moder-
ate to severe for a given project, then a square shaft helical pile is a good choice because of its solid cross
section and low perimeter surface area compared to a pipe shaft; which is hollow and has more perimeter
surface area relative to the cross-sectional area of steel. Hot-dip galvanization adds a thick coating of zinc
to the steel pile. It provides a durable coating that increases service life. Service life calculations based on
metal loss rates can be done when corrosion potential data is available. Appendix A of the TDM contains 4
design examples for corrosion design.

A Helical PULLDOWN® Micropile with its solid square shaft encased in a very dense grout mixture provides
the most resistance to corrosion since the grout acts as an additional layer of protection. Cathodic protec-
tion, or adding a corrosion allowance (additional thickness of sacrificial steel) are also options in aggres-
sive environments.

Page C-17 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 Helix strength: The structural strength of an individual helix is dependent on the plate thickness, grade of
steel, diameter, and strength of the weld that connects it to the pile/anchor shaft. There must be enough
helix plates so that the sum of their individual strengths can share the load that is required of the pile/
anchor. The product family sub-sections in Section 7 of the TDM provide the P3 helix strengths. A perfor-
mance-based specification requires a minimum number of helix plates required to share the load. The size
of each helix plate is left up to the installation contractor as long as the minimum number plates is provid-
ed, and that other requirements are met, such as minimum depth and installation torque. For example, if
60 kip capacity is required, and the individual helix strength is 40 kip, then a minimum of two helix plates
are required to share the 60 kip load. A prescriptive-based specification would be explicit on the exact
number and size of the helix plates.

Helix Size and Configuration: The size (diameter) of helix plates have a significant influence on the installa-
tion and performance of a helical pile/anchor. The helical configuration (number and size of helix plates)
can change from pile to pile. The designer can choose between a performance based design and a pre-
scriptive based design. A performance based design means the helical pile contractor is responsible for
some design and construction procedures. A prescriptive based design means the owner or designer has
the sole responsibility for all aspects of helical pile design and installation. Hubbell Power Systems, Inc.
HELICAL PILES AND ANCHORS

recommends using a performance based design in most situations.

An example of a performance based design for helical piles is minimum number of helix plates, minimum
installation torque, and minimum depth. The contractor can then decide the actual number and size of
helix plates, depths and torque required to achieve the required resistance; so long as the specified mini-
mums are met. A prescriptive based design is the actual number and size of helix plates, actual installation
torque, and actual depth. A prescriptive design may be required for comparative bid reasons and is fine
as long as a payment mechanism for adjustment is provided. Typically, the denser the soil, the helix plates
must be smaller. Alternately, the softer or less dense the bearing soil strata, the helix plates must be larger
to generate the required torque/capacity.

It is important that the smallest helix plate be the bottom-most helix. A multi-helix pile will then have sub-
sequent helices increasing in size. Generally, the same size helix is not repeated until the largest size avail-
able is reached. For example, a typical three-helix configuration would be an 8”/10”/12” or 10”/12”/14”. The
larger the shaft size, the larger the smallest helix diameter. For example, the smallest helix plate on pipe
shaft is typically 10 in or larger.

Helical piles with multiple helix plates will drive straighter, and are more likely to advance properly than
single helix configurations, and perform better. If too few helical plates are used, the most likely instal-
lation problem is “spinning out”. This can be solved by adding more helix plates, larger helix plates, and/
or more crowd pressure (downward force from installing equipment). Increasing crowd pressure may
require a larger piece of equipment (excavator, backhoe etc.). Generally, adding more helical plates is
more economical compared to upsizing to larger equipment. If too many helical plates are used, the likely
installation problem is that the torque capacity of the shaft is reached prior to reaching the required depth.
Helical extensions can be removed by unscrewing the pile/anchor, taking them off and reinstalling the pile/
anchor. If helix plates on the lead section need to be removed, it will require the installation contractor
to supply a different configuration lead section or remove helical plates in the field with a torch or saw.
Removal of helix plates in the field is done quite often, but for cost/time reasons the installing contractor
would prefer not having to remove helical plates regardless of the method.

Page C-18 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
Minimum Length (depth): The minimum length (depth) for helical piles to behave as a deep foundation is
controlled by the depth to the top-most helix plate. The plate closest to the ground surface should be a
minimum vertical depth of 5 diameters (5D) where D is the diameter of the largest helix. If the helix plate
is not installed to this depth, the failure mode will be similar to a shallow foundation, i.e. a rupture of soil at
the surface if there is not enough confining pressure. For example, if a site has loose overburden sand that
trends to medium-dense sand with increasing depth, the minimum length requirement may be “the upper-
most helix must be 5D below sub-grade”. Most specifications simplify this to 5 feet below subgrade.

Helical piles are required to be a minimum length to ensure that the pile is deep enough to provide reliable,
long term capacity. Minimum depth ensures the helix plate(s) are located in a soil stratum that will bear
load over the long term with reasonable settlement. Geotechnical reasons can override the 5D require-
ment. Geotechnical reasons that affect minimum length are frost depth, seasonal change in moisture
content, depth of fill, organic soils, volume change (shrink-swell) soils, expansive soils, liquefiable soils,
and ground water fluctuations. For example, if it is known that a compressible peat layer exists between
15’ and 20’ depth, then it is important for the pile to bear in soil stratum below the peat layer. Therefore,
a minimum depth should be required that locates the helix plates in a bearing soil below the peat layer,
thereby ensuring the pile will not settle over time as the peat consolidates.

HELICAL PILES AND ANCHORS

Tension Piles/Anchors – The 5D requirement over the uppermost helix for tension elements is very impor-
tant. If this requirement is not met, there is not enough confining pressure and a wedge or plug of soil can
erupt to the surface as the anchor fails. ICC-ES Acceptance Criteria AC358 has specified a minimum depth
for helical tension anchors. AC358 states that for tension applications, as a minimum, the helical anchor
must be installed such that the minimum depth from the ground surface to the uppermost helix is 12D,
where D is the diameter of the largest helix.

For helical tieback anchors, the 5D requirement is 5D beyond the active failure plane, which is dependent
on the friction angle of the soil and the wall height. It is important that the helical plates are not stress-
ing soil in the active failure wedge. If this happens, the wall could experience a global type failure. Again,
most specifications simplify this dimension to 5 feet beyond the active failure plane. Therefore, the mini-
mum length requirement for helical tiebacks should be “the uppermost helix must be 5 feet beyond the ac-
tive failure plane”. There should be a schedule, table, or formula for determining this in the field to ensure
that the minimum length is achieved.

Cost: The total installed length has a direct impact on the cost of the helical pile/anchor in both material
cost and installation time. The designer must always keep this in mind. The length defined (or undefined)
by the bidding documents has enormous ramifications on the cost. Well written bidding documents should
define the piles well enough to obtain the pile/anchor performance that the owner requires, as well as
obtain competitive pricing from the installing contractor. If the helical piles are not well defined, the instal-
lation contractor that leaves the most out of his bid will likely get the job. This is not good for the owner
as it increases the likelihood that the owner is not going to get the performance from the piles that is
needed; or be presented with an expensive change order after construction has begun. Bidding should be
based upon a minimum estimated bid length with some method for adjustment for differing lengths. This
approach better utilizes the flexibility of helical piles, which is one of their advantages. A thorough discus-
sion of bidding and construction documents and strategies is discussed in Section X of this Guide, titled
“Construction Documents”.

Page C-19 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 IX. HOW TO SPECIFY HELICAL PILES:
A. Minimum Capacity or Installation Torque: Whether using a performance or prescriptive specification, the
helical pile/anchor capacity (ultimate resistance) should be specified in order to ensure that the required
pile/anchor resistance is achieved. This can be done by specifying the minimum capacity directly or indi-
rectly by specifying the required installation torque. The designer can choose either way.

A.1: Minimum Capacity: Regardless of the design method used, the ultimate resistance is the same.
Ultimate resistance is the limit state based on the structural strength or the geotechnical capacity of
the helical pile, defined as the point at which no additional load can be applied without failure.

A factor of safety (or a resistance factor) is applied to the ultimate resistance to provide a reserve ca-
pacity greater than expected loads. This “normal use” load is commonly referred to as service, design,
working, SLS or un-factored load. The safety or resistance factor may be prescribed by building code,
but is often left up to the designer. A proper factor of safety/resistance is a combination of economics
and statistics. It is not typically economically feasible to design for zero probability of failure. Generally
the more uncertainty, the higher the factor of safety/resistance applied. Conversely, the less uncertain-
HELICAL PILES AND ANCHORS

ty, the lower the factor of safety/resistance applied. For ASD design, the industry standard for helical
piles is a factor of safety of 2 for permanent applications. For LRFD design, the resistance factor (Ø)
recommended for helical piles used in compression range from 0.65 to 0.75. The resistance factor (Ø)
recommended for helical piles used in tension range from 0.55 to 0.65.

For tieback anchors that are going to be individually post-tensioned and tested, a factor of safety of
1.5 is used. A lower factor of safety is justified since there is less uncertainty (the tieback is tested).

One problem with construction documents regarding helical piles/anchors is clearly identifying the
capacity required. The best method is to clearly define the ultimate resistance required. If the de-
signer chooses to specify the un-factored load, then the loads should be clearly identified as (service/
design/working/SLS/un-factored loads) and clearly state what the required factor of safety/resistance
is.

A.2: Installation Torque: Installation torque can also be specified as the minimum requirement as it
relates to the pile/anchor capacity required. This should only be done for piles/anchors that will not
receive a proof test. Installation torque should not be used to specify minimum capacity for helical
tieback anchors when each anchor will be post tensioned and proof tested. In that case, passing the
proof test is the only criteria that matters and obtaining a minimum torque is really a convenience for
the contractor to ensure the anchorage does not fail the proof test.

If the installation torque approach is utilized, the designer should be aware that torque capacity corre-
lations only apply to helical piles with advancement rate that equals or exceeds 85% of the helix pitch
per revolution at the time of final torque measurement. Refer to Section 6 of the TDM for a full discus-
sion of torque correlation (Kt) relationships. On-site testing can be used to obtain a site specific Kt,
otherwise use the default values listed in Table C-1 above.

Also, tension and multi-helix compression capacity should be determined based on the average torque
measured over the last three helix diameters of installed length. Most specifications simplify this to 3
feet. The reason this is done is to better predict the bearing capacity of the helix plates as they distrib-
ute load to the soil in a passive pressure bulb either below (compression) or above (tension) the helix
plate(s). Depending on how fast the torque increases over the last 3 feet of penetration will have a
significant impact on the capacity of the helical pile/anchor. Note that it is virtually impossible to av-
erage a helical anchor/pile’s maximum torque rating over the last three average helix diameters, which
means a shaft with higher torque strength may be needed in very dense soils.

Page C-20 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
X. CONSTRUCTION DOCUMENTS:
A. Construction Plans: The previous sections presented the various design elements that should be con-
sidered when using helical piles/anchors. Each one of the following design elements should be defined in
the construction plans on a well-engineered project.

• Shaft Type
• Shaft Size
• Helix Configuration
• Pile/Anchor Length
• Minimum Capacity or Install Torque

By defining the parameters that will be acceptable for each of these design elements, more favorable
results will be obtained from both a pricing and performance perspective. It is the author’s experience that
summarizing the pile/anchor parameters in a format similar as listed above works well.

For example, consider using the following format or similar plans:

HELICAL PILES AND ANCHORS

Table C-10 - Helical Pile Data Summary

Pile Type Square Shaft Helical Pile

Shaft Material: CHANCE Type SS175 1-3/4” Solid Square Shaft
Helix Configuration 8”/10”/12” Helix Plates
Bid Length 28’-0
Ultimate Resistance, or 80 kip Minimum
Installation Torque 8,000 ft-lb Min Average

Other design parameters can also be added such as grout column diameter for grouted Helical PULL-
DOWN® Micropiles, minimum length (if different from bid length), termination type, angle of installation, or
required casing diameter & length. Soil conditions may also require the pile head end condition (fixed or
pinned) be specified if shaft capacity controls the design.

The above summary provides enough information for bidders to aggressively bid on the same items as
other bidders. It reduces the risk of being undercut by a contractor bidding with either lesser material,
or a lesser estimated length. This also gives the owner and the engineer a comparative basis for their bid
analysis. A method for payment should also be established for deviations from the bid length and should
be considered in the bid analysis.

B. Bidding Documents: Well-crafted construction documents will allow installation contractors to ac-
curately bid and properly install helical piles to serve their intended purpose. It is in the owner’s and
engineer’s best interest for contractors to have the proper information to be able to accurately bid and
properly install the piles/anchors. Poorly-crafted construction documents with lack of definition will result
either in high pricing because the contractor has to assume an inordinate amount of risk, less than desired
performance from the piles/anchors, installation problems, or change orders from the contractor. None of
these things make the designer, or helical piles, attractive to the owner for future projects.

Bid processes can be handled in several different ways, and are dependent on the particular aspects and
needs of each project. No two projects are exactly the same. Therefore, different aspects of the project
may be the driving force behind the bid process or bid structure. These could be price, speed, or function.
Helical piles/anchors are used in design/build projects, lump sum bids and projects with a unit pricing
structure. It is the writer’s experience that unless there is a wealth of geotechnical information that is
available to the bidder’s, lump sum pricing is generally not in the owner’s best interest.

Page C-21 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 A pricing structure that shares some of the risk with the owner and the contractor tends to result in better
overall pricing. One exception to this would be if the bidders are allowed access to the site to install probe
or exploratory helical piles prior to bidding. Helical piles/anchors are well suited to exploratory installations
because of torque-to-capacity relationships, the pile/anchor material can be recovered, and there is mini-
mal disruption to the site. The less risk the contractor assumes, the better the pricing will be.

Generally, a pricing structure that allows for per/pile price to a specified bid depth with unit pricing for
additional/deductible length works best. For example, if the geotechnical information available indicates
the average pile/anchor depth to be between 25’-0 and 30’-0, then a bid length of 28’-0 might be estab-
lished with unit pricing by the foot for piles that exceed or are short of that length. Unit pricing would
likely be even better if it is based on increments of helical pile section lengths (5’-0 & 7’-0) rather than 1’
increments, since 7’-0 is the most common section length. This is because the same amount of material
is likely to be used once the contractor has to add an additional section. In other words, if the pile depth
exceeds 28’- 0, there is an additional unit cost per unit additional 7’-0 extension. Some situations may lend
themselves to providing a unit price for helical extensions. Many helical tieback projects have benefited by
utilizing this approach.
HELICAL PILES AND ANCHORS

Another unit pricing strategy is to have the bidders provide a unit price per foot for the entire length of
piling or anchorage on the project and not have a price per pile/anchor. In other words, the construction
plans might show 100 piles at an average 50’ depth and the bid quantity would be set up for unit pric-
ing by the foot, (or 7’ increments) for 5000 lineal feet (LF) of piling. Payment would be made by the unit
price for the quantity of piling installed, whether it is 4500 LF or 5500 LF.

C. Technical Specifications: Technical Specifications are an important part of well-crafted construction

documents and should further define the details regarding helical piles or anchors. Technical Specifications
should define anything that affects the pricing or performance of the piles or anchors. At a minimum, the
following should be defined:

• Pile materials
• Installation tools and equipment
• Quality control methods
• Installation records required
• Installation tolerances and techniques
• Load testing requirements, procedures, and acceptance criteria (if any)

Model specifications for helical piles, anchors, and tiebacks that can be used as templates and edited for
your specific project needs are included on www.abchance.com.

Page C-22 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2019
 FORMS

Page D-1 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 FORMS
APPENDIX D
CONTENTS

Preliminary Design Request Form................................................... D-3

HeliCAP® Helical Capacity Design Software Buyer................... D-4
Qualification and Order Form
CHANCE® Helical Anchor/Pile Axial Test Form.......................... D-6
CHANCE® Helical Anchor/Pile Installation Log............................D-7
CHANCE HELICAL PULLDOWN® Micropile Installation Log.D-8
FORMS

DISCLAIMER

The information in this manual is provided as a guide to assist you with your design and in writing your own specifications.

Installation conditions, including soil and structure conditions, vary widely from location to location and from point to
point on a site.

Independent engineering analysis and consulting state and local building codes and authorities should be conducted
prior to any installation to ascertain and verify compliance to relevant rules, regulations and requirements.

Hubbell Power Systems, Inc., shall not be responsible for, or liable to you and/or your customers for the adoption,
revision, implementation, use or misuse of this information. Hubbell, Inc., takes great pride and has every confidence in
its network of installing contractors and dealers.

Hubbell Power Systems, Inc., does NOT warrant the work of its dealers/installing contractors in the installation of
CHANCE® Civil Construction foundation support products.

Page D-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
PRELIMINARY DESIGN REQUEST FORM Contact at Hubbell Power Systems, Inc.:

Installing Contractor
Firm:______________________________________________ Contact_________________________________________
Phone:____________________________ Fax:_____________________________ Cell: ____________________________
Project
Name:_________________________________________ Type: o Foundation o Underpinning/Shoring
Address:________________________________________ o New Construction o Rock
_______________________________________________ o Tower Foundation o Other:
_______________________________________________

Project Engineer ? o Yes o No

Firm: __________________________________________ Contact: ____________________________________________
Address:________________________________________ Phone: _____________________________________________
_______________________________________________ Fax: _______________________________________________
_______________________________________________ Email: ______________________________________________

Geotechnical Engineer ? o Yes o No

FORMS
Firm: __________________________________________ Contact: ____________________________________________
Address:________________________________________ Phone: _____________________________________________
_______________________________________________ Fax: _______________________________________________
_______________________________________________ Email: ______________________________________________

Loads
Design Load FS (Mech) #1 FS (Geo) #1 Design Load FS (Mech) #2 FS (Geo) #2
Compression _______________ ____________ _____________ _____________ ______________ ___________
Tension _______________ ____________ _____________ _____________ ______________ ___________
Shear _______________ ____________ _____________ _____________ ______________ ___________
Overturning _______________ ____________ _____________ _____________ ______________ ___________

Define the owner’s expectations and the scope of the project:_____________________________________________

______________________________________________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________

The following are attached: o Plans o Soil Boring o Soil Resistivity o Soil pH

If any of the above are not attached, please explain:_____________________________________________________

______________________________________________________________________________________________________

Date: ___________________Requested Response:__________________________________________________________

Please copy and complete this form to submit a design request.

Page D-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 HeliCAP® Helical Capacity Design Software
Buyer Qualification and Order Form

Qty Description Price Each Hard Drive Serial # (see instructions on next page)

1 HeliCAP® Helical Capacity __________ ______________________________________________

Design Software
o Please send me a copy of HeliCAP® on CD.
Three additional licenses are available per copy. Go to www.abchance.com or contact Hubbell Power
Systems, Inc. for more information.

BACKGROUND INFORMATION APPLICATION REFERENCE

Engineer UTILITY
o Structural o Guy Anchors (Transmission Line)
o Geotechnical o Telecommunication Towers
o Civil o DOT/FFA
o Mechanical o Registered Professional
o Electrical o Other __________________
FORMS

o Registered professional
o Previous helical experience
o Other _________________
Contractor
o General
o Sub
o Design-Build
o Other _________________
o Architect
o Distributor
o Government Agency
o Educational Institute
o Student
o Power Utility
o End User
o Other _________________

Page D-4 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
System Requirements
• Windows® XP/7/8
• Pentium® 100 MHz processor
• 32 Mb RAM
• 35 Mb free hard disk space
• 2X CD-ROM drive
• MAC users must have Virtual PC installed.
How to Find Your Hard Drive Serial Number
Your hard drive serial number is required in order to issue a license key for the HeliCAP® Hare. To find your hard
drive serial number:
• Click the Start button at the lower left corner of the desktop.
• In the search prompt, type “cmd”.
• A dialog box will pop up that should have “CMD”. It should be near the top of the box and it should be
highlighted. Press Enter.
• A DOS window should appear and display a DOS prompt. The DOS prompt will normally start with “C:”,
which is the default drive. If you want to install HeliCAP® on a different drive, type the drive letter followed
by a colon (e.g., “d:”) at the prompt and press Enter.
• Type “vol” at the DOS prompt and press Enter. The hard drive serial number (or Volume Serial Number)
will be displayed. The Volume Serial Number is 8 digits, with a dash in between. The characters are alpha

FORMS
numeric.
• Record the serial number and close the DOS prompt window.

Page D-5 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 CHANCE® Helical Pile/Anchor Axial Test
Project: Date: Sheet   of
Anchor/Pile Number: Product Series: o SS o RS
Helix Configuration: Total Depth:
Time: Start        Finish Recorded by:

DISPLACEMENT
PRESS LOAD TIME
(psi) (kip) (min) GAUGE A GAUGE B GAUGE C
(in) (in) (in)
FORMS

Page D-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 CHANCE® Helical Pile/Anchor Installation Log
Project: Date: Sheet   of
Anchor/Pile Number: Product Series: o SS o RS
Helix Configuration: Installation Angle:
Time: Start        Finish Recorded by:

DEPTH PRESSURE TORQUE

COMMENTS
(ft) (psi) (ft-lb)

FORMS

Page D-7 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 CHANCE HELICAL PULLDOWN® Micropile Installation Log
Project: Date: Sheet   of
Anchor/Pile Number: Product Series: o SS o RS
Helix Configuration: Installation Angle:
Grout Column Diameter: Sleeve Depth: From to
Time: Start        Finish Recorded by:

DEPTH PRESSURE TORQUE

GROUT FLOW (Volume/Shaft/Length)
(ft) (psi) (ft-lb)
FORMS

Page D-8 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 GLOSSARY

Page G-1 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 GLOSSARY of TERMS

Alignment Load (AL) A low magnitude load applied to a pile/anchor at the

start of the load test to keep the testing equipment cor-
rectly positioned and to remove any slack in the reac-
tion system.
Allowable Capacity The geotechnical capacity of a pile/anchor or pier as
determined by a reduction of the ultimate capacity with
an appropriate factor of safety or resistance factor.
Anchor or Anchorage A combination of anchor and the soil or deeply weath-
ered rock into which it is installed that together resist
tension loads applied to the anchor.
Axial Load (P) An axially oriented compression or uplift (tension) load
GLOSSARY

supported by an pile/anchor or pier resulting from

dead, live and seismic loads.
Bearing Load A load generally regarded as an axial compressive load
on a pile or pier.
Bearing Stratum Soil layers of sufficient strength to be capable of resist-
ing the applied axial load transferred by a pile or pier.
Contractor The person or firm responsible for performing the re-
quired construction, i.e., installation of CHANCE® Helical
Piles/Anchors or ATLAS RESISTANCE® Piers.
Coupling A central steel shaft connection for CHANCE® Type SS
and RS helical piles. Couplings may be either separable
sleeve couplings or integral forged sockets.
Coupling Bolts High strength structural steel fasteners used to connect
helical anchor/pile segments together. For CHANCE®
Type SS segments the coupling bolt transfers axial
loads. For CHANCE® Type RS segments the coupling
bolt transfers both axial and torsional loads.
Creep The movement that occurs during the Creep Test of a
pile/anchor or pier under a constant load.
Dead Load (DL) Generally, vertical loads comprised of the weight of the
structure plus various fixed assets, such as equipment,
machinery, walls and other permanent items.
Design Load (Pd) The maximum anticipated service load applied to a pile
or pier, comprised of calculated dead and live loads.
Also known as Working Load.

Page G-2 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
Effective Stress The total force on a cross section of a soil mass that is
transmitted from grain to grain of the soil, divided by
the area of the cross section. Also known as Intergranu-
lar Stress.
Elastic Movement The recoverable movement measured during a pile/pier
load test resulting from the elastic shortening or length-
ening of the pile/pier shaft material.
End Bearing The transfer of axial loads to the soil at the tip of a heli-
cal pile via helix plates or at the tip of a pier.
Evaluation Services Report (ESR) The evaluation of a manufactured product or building
component by the evaluation services of the various
model code agencies (ICC). The report outlines the re-
quirements that must be met to satisfy the intent of the
Building Code.
Failure Criteria A method used to determine the ultimate capacity of
a pile/anchor based on a load test. A typical failure
criteria for helical piles is the load where the pile head
displacement is equal to 10% of the average helix diam-
eter plus the elastic movement.

GLOSSARY
Foundation Soil Load The load from soil overburden on the outstanding toe
of a footing. This soil load is in addition to the existing
structure weight supported by the footing. It increases
the dead load used as a reaction to install a push pier
and therefore aids the installation. However, it may work
to defeat attempts to lift a structure and may require
reduction or removal if a lift is required.
Gunite A dry concrete mixture that is carried to a nozzle in
moving air where it is mixed with water. The operator
controls the water-cement ratio.
Helical Extension A helical pile/anchor component installed immediately
following the lead section (if required) to increase the
bearing area of the foundation. This component con-
sists of one or more helical plates welded to a central
steel shaft.
Helical Pile A bearing type foundation consisting of a lead section,
helical extension (if required by site conditions), plain
extension section(s) and a pile cap. Also known as a
screw pile or helical screw foundation.
HELICAL PULLDOWN® Micropile A small diameter, soil displacement, cast-in-place heli-
cal pile in which the applied load is resisted by both
end bearing and friction. The design is protected under
United States Patent 5,707,180, Method and Apparatus
for Forming Piles In-Situ.

Page G-3 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Helix Plate A round steel plate formed into a ramped spiral. The he-
lical shape provides the downward force used to install
a helical pile/anchor, plus the plate transfers the load
to the soil in end bearing. Helical plates are available in
various diameters and thicknesses.
In-Situ In the natural or original position. Used in soil mechan-
ics to describe the original state of soil condition prior
to disturbance from field testing or sampling methods.
Installation Torque The resistance generated by a helical pile/anchor when
installed into soil. The installation resistance is a func-
tion of the soil plus the size and shape of the various
components of the helical pile/anchor. The installation
energy must equal the resistance to penetrate the soil
(penetration energy) plus the energy loss due to fric-
tion (friction energy).
Kip One thousand pounds of force, or a "kilopound."
Lateral Load (V) A load applied perpendicular to the longitudinal axis of
a pile or pier resulting from live and seismic loads. Also
GLOSSARY

called a shear load.

Lead Section The first helical pile/anchor component installed into
the soil, consisting of single or multiple helix plates
welded to a central steel shaft. The helical plates trans-
fer the axial load to bearing stratum.
Live Load (LL) A load comprised of roof, wind, floor, and in some cas-
es, seismic loads. Floor loads include people, temporary
or non-fixed equipment, furniture and machinery. Roof
loads include ice and snow.
Load Bearing Stratum See Bearing Stratum.
Net Settlement The non-elastic (non-recoverable) movement or dis-
placement of a pile/pier measured during load testing.
Open Specification An arrangement in which the contractor is given the
responsibility for the scope and design of the pile or
pier installation. The construction, capacity and perfor-
mance of the pile or pier are the sole responsibility of
the contractor. This specification is most common for
securing bids on temporary projects, and is not recom-
mended for permanent applications. See also Perfor-
mance Specification and Prescriptive Specification.
Overburden Natural or placed material that overlies the load bearing
stratum.

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Performance Specification An arrangement in which the contractor is given the re-
sponsibility for certain design and/or construction pro-
cedures, but must demonstrate to the owner through
testing and/or mutually agreed upon acceptance crite-
ria that the production piles/piers meet or exceed the
specified performance parameters. The contractor and
owner share responsibility for the work. See also Open
Specification and Prescriptive Specification.
Pile Cap A means of connection through which structural loads
are transferred to a pile or pier. The type of connection
varies depending on the requirements of the project
and the type of pile/pier material used.
NOTE: Care must be used in the design of pile caps to
ensure adequate structural load transfer. Design con-
straints such as expansive soils, compressible soils and
seismic loads must be accounted for in pile cap design.
Pipe Shaft A central shaft element made from hollow, steel, round
pipe, ranging in diameter from 2" to 10". Also known
as Hollow Shaft, Round Shaft (Type RS), Type T/C and

GLOSSARY
Type PIF for CHANCE® Helical Piles.
PISA® System The acronym for Power Installed Screw Anchor. The
PISA® System was originally developed for the power
utility industry in the late 1950's.
Plain Extension A central steel shaft segment without helical plates. It is
installed following the installation of the lead section or
helical extension (if used). The units are connected with
separable sleeve couplings or integral forged couplings
and bolts. Plain extensions are used to extend the heli-
cal plates beyond the specified minimum depth into
competent load bearing stratum.
Pore Pressure Unit stress carried by the water in the soil pores in a
cross section.
Prescriptive Specification An arrangement in which the owner has the sole re-
sponsibility for the scope and design of the pile or pier
installation and specifies the procedures that must be
followed. Prescriptive specifications mandate the owner
to be responsible for the proper performance of the
production piles/piers. The contractor is responsible
for fulfilling the obligations/details as specified in the
construction documents.
Pretensioning The prestressing of an anchor or foundation prior to the
service load being applied.
Proof Test The incremental loading of a pile or pier, where the load
is held for a period of time and the total movement is
recorded at each load increment. The maximum applied
load is generally 1.0 to 1.25 times the design load.

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 Rebound Waste created by sprayed concrete falling to the floor
or ground below the intended target location. Rebound
is usually half for shotcrete compared to gunite.
Round Shaft Hollow steel, round pipe, central shaft elements ranging
in diameter from 2" to 10". Also known as Hollow Shaft,
Round Shaft (Type RS), Type T/C and Type PIF for
CHANCE® Helical Piles.
Safety Factor (SF) The ratio of the ultimate capacity to the working or de-
sign load used for the design of any structural element.
Also referred to as a factor of safety.
Seismic Load A load induced on a structure caused by ground mo-
tions resulting from a seismic event (earthquake). Usu-
ally included as part of the live load.
Shaft A steel or composite steel/grout shaft or rod used to
transfer load from the surface to the bearing plates.
Soldier Pile An H or WF section normally driven (or placed in a
drilled hole and backfilled with weak grout or concrete)
vertically at intervals of several feet to resist the load on
the lagging of a retaining wall. It is the main structural
GLOSSARY

element of a retaining wall. Also known as an h-pile.

Square Shaft (SS) A solid steel, round-cornered-Square central Shaft ele-
ment ranging in size from 1-1/4" to 2-1/4". Also known as
Type SS for CHANCE® Helical Anchors.
Starter Section With reference to a CHANCE® Helical Pile, a lead section
Test Load The maximum load applied to a pile or pier during test-
ing.
Torque Rating The maximum torque energy that can be applied to a
helical anchor/pile during installation in soil. Also known
as allowable torque or safe torque.
Ultimate Capacity (Qu) The limit state based on the structural and/or geotech-
nical capacity of a pile or pier, defined as the point at
which no additional capacity can be justified.
Ultimate Load (Pu) The load determined by applying a safety factor to the
working load. The ultimate load applied to a structural
element must be less than the ultimate capacity of that
same element or a failure limit state may occur.
Underpinning Bracket A bracket used to connect an existing strip or spread
foundation or footing to a CHANCE® Helical Pile
Uplift Load Generally, an axial tensile load on an anchor.
Verification Test Similar to the Proof Test except a cyclic loading method
is used to analyze total, elastic and net movement of
the pile. Used for pre-contract or pre-production pile
load tests.
Working Load Another term for Design Load.

Page G-6 | Hubbell Power Systems, Inc. | All Rights Reserved | Copyright © 2017
 Hubbell Power Systems, Inc. | Centralia, Missouri 65240 | © Copyright 2017 Hubbell Incorporated
®
TD_06_088_E

Because Hubbell has a policy of continuous product improvement,

we reserve the right to change design and specifications without notice.

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