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Saudi Soils & Foundation Code

SBC 303 - CR
Code Requirements

2018

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Saudi Building Code for Soils and foundations

SBC 303
Key List of the Saudi Codes: Designations and brief titles

Title Code Req.1 Code & Com.2 Arabic Prov. 3

The General Building Code SBC 201-CR SBC 201-CC SBC 201-AR
Structural – Loading and Forces SBC 301-CR SBC 301-CC SBC 301-AR
Structural – Construction SBC 302- CR SBC 302-AR
Structural – Soil and SBC 303-CR SBC 303-CC SBC 303-AR

Foundations
Structural – Concrete Structures SBC 304-CR SBC 304-CC SBC 304-AR
Structural – Masonry Structures SBC 305-CR SBC 305-CC SBC 305-AR
Structural – Steel Structures
Electrical Code SBC 401-CR SBC 401-AR
Mechanical Code SBC 501- CR SBC 501-CC SBC 501-AR
Energy Conservation- SBC 601- CR SBC 601- CC SBC 601- AR
Nonresidential
Energy Conservation-Residential SBC 602- CR SBC 602- CC SBC 602- AR
Plumbing Code SBC 701- CR SBC 701-CC SBC 701-AR
Private sewage Code SBC 702- CR SBC 702-AR
Fire Code SBC 801- CR SBC 801-CC SBC 801-AR
Existing Buildings Code SBC 901- CR SBC 901-CC SBC 901-AR
Green Construction Code SBC 1001- CR SBC 1001-CC SBC 1001-AR
Residential Building Code* SBC 1101- CR SBC 1101-CC SBC 1101-AR
Fuel Gas Code* SBC 1201- CR SBC 1201-CC SBC 1201-AR
1. CR: Code Requirements without Commentary
2. CC: Code Requirements with Commentary
3. AR: Arabic Code Provisions
* Under Development

COPYRIGHT © 2018
by
The Saudi Building Code National Committee (SBCNC).

ALL RIGHTS RESERVED. All intellectual property rights of this Saudi Code are owned by the
National Committee of Saudi Building Code as per the Saudi laws of the intellectual property. No part
of this code may be reproduced, distributed or leased in any form or by any means, including but not
limited to publishing on cloud sites, computer networks or any electronic means of communication,
without prior written permission from the National Committee for the Saudi Building Code. The
purchase of an electronic or paper copy does not exempt the individual or entity from complying with
the above limitations.

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Technical Committee (SBC 303):

1 Prof. Mosleh A. Al-Shamrani Chairman

2 Dr. Abdullah H. Alsabhan Member
3 Dr. Muawia A. Daf'allah Member

REVIEW COMMITTEE:

1 Dr. Naif M. Alabbadi Chairman

2 Dr. Khaled M. Aljammaz Member
3 Dr. Abdulrahman G. Al-enizi Member
4 Engr. Saeed K. Kadasah Member
5 Engr. Tawifik I. Aljrayed Member

SAUDI BUILDING CODE National Committee (SBCNC) REVIEWal SUPPORT:

1 H. E. Dr. Saad O. AlKasabi Chairman Dr. Mubashir Aziz Abdulaziz RCJY team
2 Dr. Naif M. Alabbadi Vice Chairman
3 Dr. Abdulrahman G. Al-enizi Member TECHNICAL EDITING COMMITTEE:
4 Engr. Saeed K. Kadasah Member
1 Prof. Ahmed B. Shuraim Chairman
5 Dr. Hassan S. Alhazmi Member
6 Engr. Badr S. AL-maayoof Member 2 Dr. Abdallah M. Al-Shehri Member
7 Engr. Fayez A. Alghamdi Member 3 Engr. Tawifik I. Aljrayed Member
8 Engr. Mohammed A. Alwaily Member
9 Dr. Bandar S. Alkahlan Member EDITORIAL SUPPORT:
10 Engr. Ahmad N. Hassan Member
11 Engr. Abdulnasser S. Alabdullatif Member Prof. Nadeem A. Siddiqui Engr. Rais Mirza
12 Dr. Hani M. Zahran Member
13 Engr. Khalifa S. Alyahyai Member
14 Dr. Khaled M. Aljammaz Member
15 Dr. Ibrahim O. Habiballah Member
16 Dr. Saeed A. Asiri Member
17 Dr. Abdallah M. Al-Shehri Member
18 Engr. Saad S. Shuail Member

ADVISORY COMMITTEE :
1 Dr. Khaled M. Aljammaz Chairman
2 Eng. Khalifa S. Alyahyai Vice Chairman
3 Dr. Hani M. Zahran Member
4 Prof. Ali A. Shash Member
5 Prof. Ahmed B. Shuraim Member
6 Dr. Khalid M. Wazira Member
7 Dr. Abdulhameed A. Al Ohaly Member
8 Dr. Hamza A. Ghulman Member
9 Engr. Hakam A. Al-Aqily Member
10 Prof. Saleh F. Magram Member
11 Engr. Nasser M. Al-Dossari Member
12 Dr. Waleed H. Khushefati Member
13 Dr. Waleed M. Abanomi Member
14 Dr. Fahad S. Al-Lahaim Member

SBC 303-CR-18 i

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PREFACE

PREFACE

The Saudi Building Code for Soils and Foundations referred to as SBC 303 provides minimum requirements
pertaining to material properties of soils, and design and construction of foundation systems. The first edition
of SBC 303 was published in the year of 2007. SBC 303-18 is the second edition of SBC 303 and covers:
geotechnical investigations; excavation grading and fill; presumptive load-bearing of soils; spread footings;
foundation walls; retaining walls; combined footings and mats; design for expansive soils; design for collapsible
soils; design for sabkha soils; design for vibratory loads; dampproofing and waterproofing; and deep
foundations.
The current edition of the Code has been substantially reorganized and reformatted relative to its 2007 edition.
The code is reorganized into 14 chapters. The reorganization was in response to past requests concerning the
difficulty in finding provisions. The new layout is more user-friendly and will better facilitate the use of the
design provisions.
The International Code Council (ICC) materials, especially Chapter 18 of IBC, and local and regional
geotechnical reports were used in the development of this Code. Saudi Building Code National Committee
(SBCNC) has made an agreement with the ICC to use their materials and modify them as per the local
construction needs and regulatory requirements of Saudi Arabia. The ICC is not responsible or liable in any
way to SBCNC or to any other party or entity for any modifications or changes that SBCNC makes to such
documents.
The writing process of SBC 303-18 followed the methodology approved by the Saudi Building Code National
Committee. Many changes and modifications were made in the referred sources to meet the local weather,
materials, construction and regulatory requirements.
The committees responsible for SBC 303 Code have taken all precautions to avoid ambiguities, omissions, and
errors in the document. Despite these efforts, the users of SBC 303 may find information or requirements that
may be subject to more than one interpretation or may be incomplete. The SBCNC alone possesses the authority
and responsibility for updating, modifying and interpreting the Code.
It is a common assumption that engineering knowledge is a prerequisite in understanding code provisions and
requirements; thus, the code is oriented towards individuals who possess the background knowledge to evaluate
the significance and limitations of its content and recommendations. They shall be able to determine the
applicability of all regulatory limitations before applying the Code and must comply with all applicable laws
and regulations.
The requirements related to administration and enforcement of this Code are advisory only. SBCNC and
governmental organizations, in charge of enforcing this Code, possess the authority to modify these
administrative requirements.

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SUMMARY OF CHAPTERS

SUMMARY OF CHAPTERS
The entire SBC 303-18 is divided into 14 chapters. A brief outline of these chapters is given below:
Chapter 1. General—This chapter explains where SBC 303 Code applies and how it is to be interpreted. This
chapter clarifies that allowable bearing pressures, allowable stresses and design formulas provided in this code
shall be used with the allowable stress design load combinations. The various terminologies used in the Code
are also defined in this chapter.
Chapter 2. Geotechnical Investigations—This chapter addresses the conditions that mandate a geotechnical
investigation, as well as the information that must be included in the report. The requirements of this chapter
make it mandatory that geotechnical investigations involving in-situ testing, laboratory testing or engineering
calculations shall be conducted by a registered design professional only.
Chapter 3. Excavation, Grading and Fill—This chapter provides the details of safety precautions that must
be considered at all stages of excavation, grading and fill. This chapter also emphasizes that special care,
measures, and techniques shall be followed for excavation below the groundwater table.
Chapter 4. Presumptive Load-Bearing values of Soils —This chapter provides presumptive load-bearing
values for the various class of soils and rocks. The chapter also clarifies how to use these presumptive load-
bearing values for foundations and footing design.
Chapter 5. Spread Footings—This chapter provides the requirements for the design and construction of
spread footings.
Chapter 6. Foundation Walls —Foundation walls typically serve as the enclosure for a basement or crawl
space as well as a below-grade load-bearing foundation component. These walls carry vertical loads from the
structure above, resist wind and any lateral forces transmitted to the foundations and sustain earth pressures
exerted against the walls. This chapter provides the requirements for the design and construction of foundation
walls.
Chapter 7. Retaining Walls—This chapter provides minimum requirements for the design of retaining walls
to ensure stability against overturning, sliding, excessive foundation pressure and water uplift. The provisions
of this chapter apply to all matters pertaining to design and construction of rigid gravity, semi-gravity, cantilever,
buttressed, and counterfort retaining walls.
Chapter 8. Combined Footings and Mats —This chapter provides requirements for the analysis, design, and
construction of combined footings and mats.
Chapter 9. Design for Expansive Soils —Provisions of this chapter apply to building foundation systems in
expansive soil areas. Foundation design and construction shall be based on geotechnical investigations, unless
the building official ascertains that sufficient data upon which to base the design and construction of the
foundation system is available.
Chapter 10. Design for Collapsible Soils —Provisions of this chapter apply to building foundation systems
on collapsible soil areas. Foundation design and construction shall be based on site investigations, unless the
building official ascertains that sufficient data upon which to base the design and construction of the foundation
system is available.
Chapter 11. Design for Sabkha Soils — Soils with a high content of soluble or insoluble salts and high
salinity with the occasional relatively hard crusty surface can be classified as Sabkha. Provisions of this chapter
apply to building foundation systems in sabkha soil areas. Foundation design and construction shall be based
on geotechnical site investigations unless the building official ascertains that sufficient data upon which to base
the design and construction of the foundation system is available.
Chapter 12. Design for Vibratory Loads —This chapter provides minimum requirements for the design of
foundations subjected to dynamic loading due to machinery vibrations.
Chapter 13. Dampproofing and Waterproofing— This chapter covers the requirements for waterproofing
and dampproofing those parts of substructure construction that need to be provided with moisture protection. It
identifies the locations where moisture barriers are required and specifies the materials to be used and the

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SUMMARY OF CHAPTERS

methods of application. The provisions also deal with subsurface water conditions, drainage systems and other
protection requirements.
Chapter 14. Deep Foundations—This chapter sets forth the general rules for analyzing, designing, detailing
and installing deep foundations.

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TABLE OF CONTENTS

TABLE OF CONTENTS

TAB LE OF CONTENTS ...................................................................................................................................... V

CHAPTER 1 —GENERAL ...................................................................................................................................1
1.1 —SCOPE ............................................................................................................................................................ 1
1.2 —DESIGN BASIS ................................................................................................................................................ 1
1.3 —DEFINITIONS .................................................................................................................................................. 1

CHAPTER 2 —GEOTECHNICAL INVESTIGATIONS ........................................................................................6

2.1 —GENERAL ....................................................................................................................................................... 6
2.2 —SCOPE OF INVESTIGATION .............................................................................................................................. 6
2.3 —SOIL CLASSIFICATION .................................................................................................................................... 9
2.4 —INVESTIGATION.............................................................................................................................................. 9
2.5 —SOIL BORING AND SAMPLING ....................................................................................................................... 10
2.6 —REPORTING .................................................................................................................................................. 10

CHAPTER 3 —EXCAVATION, GRADING AND FILL ..................................................................................... 13

3.1 —GENERAL ..................................................................................................................................................... 13
3.2 —COMMENCEMENT ......................................................................................................................................... 13
3.3 —EXCAVATIONS NEAR FOUNDATIONS ............................................................................................................ 13
3.4 —SLOPE LIMITS ............................................................................................................................................... 13
3.5 —SURCHARGE ................................................................................................................................................. 14
3.6 —PLACEMENT OF BACKFILL ............................................................................................................................ 14
3.7 —SITE GRADING .............................................................................................................................................. 14
3.8 —GRADING DESIGNATION ............................................................................................................................... 14
3.9 —GRADING AND FILL IN FLOOD HAZARD AREAS ............................................................................................. 14
3.10 —COMPACTED FILL MATERIAL...................................................................................................................... 15
3.11 —CONTROLLED LOW-STRENGTH MATERIAL (CLSM) ................................................................................... 15

CHAPTER 4 —PRESUMPTIVE LOAD-BEARING VALUES OF SOILS ......................................................... 16

4.1 —LOAD COMBINATIONS .................................................................................................................................. 16
4.2 —PRESUMPTIVE LOAD-BEARING VALUES ........................................................................................................ 16
4.3 —LATERAL LOAD RESISTANCE........................................................................................................................ 16
4.4 —COMPUTED LOAD-BEARING VALUES ............................................................................................................ 16

CHAPTER 5 —SPREAD FOOTINGS ............................................................................................................... 18

5.1 —GENERAL ..................................................................................................................................................... 18
5.2 —DEPTH AND WIDTH OF FOOTINGS ................................................................................................................. 18
5.3 —FOOTINGS ON OR ADJACENT TO SLOPES ....................................................................................................... 18
5.4 —DESIGN OF FOOTINGS................................................................................................................................... 19
5.5 —EMBEDDED POSTS AND POLES ...................................................................................................................... 20
5.6 —SEISMIC REQUIREMENTS .............................................................................................................................. 21

CHAPTER 6 —FOUNDATION WAL LS ............................................................................................................ 25

6.1 —GENERAL ..................................................................................................................................................... 25
6.2 —DESIGN LATERAL SOIL LOADS...................................................................................................................... 25
6.3 —UNBALANCED BACKFILL HEIGHT ................................................................................................................. 25
6.4 —RUBBLE STONE FOUNDATION WALLS ........................................................................................................... 25
6.5 —CONCRETE FOUNDATION WALLS .................................................................................................................. 25
6.6 —PRESCRIPTIVE DESIGN OF CONCRETE FOUNDATION WALLS .......................................................................... 25
6.7 —PIER AND CURTAIN WALL FOUNDATIONS ..................................................................................................... 26

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TABLE OF CONTENTS

CHAPTER 7 —RETAINING WALLS ................................................................................................................ 28

7.1 —GENERAL ..................................................................................................................................................... 28
7.2 —LATERAL EARTH PRESSURES ........................................................................................................................ 28
7.3 —BEARING CAPACITY ..................................................................................................................................... 29
7.4 —STABILITY .................................................................................................................................................... 30
7.5 —WALL DIMENSIONS ...................................................................................................................................... 30
7.6 —WALL CONSTRUCTION ................................................................................................................................. 31

CHAPTER 8 —COMBINED FOOTINGS AND MATS ...................................................................................... 35

8.1 —GENERAL ..................................................................................................................................................... 35
8.2 —LOADINGS.................................................................................................................................................... 35
8.3 —CONCRETE ................................................................................................................................................... 35
8.4 —CONTACT PRESSURE .................................................................................................................................... 35
8.5 —SETTLEMENT ............................................................................................................................................... 38
8.6 —COMBINED FOOTINGS .................................................................................................................................. 38
8.7 —CONTINUOUS FOOTINGS............................................................................................................................... 39
8.8 —GRID FOUNDATIONS..................................................................................................................................... 40
8.9 —MAT FOUNDATIONS ..................................................................................................................................... 40
8.10 — SEISMIC REQUIREMENTS ........................................................................................................................... 42

CHAPTER 9 —DESIGN FOR EXPANSIVE SOIL S .......................................................................................... 44

9.1 —GENERAL ..................................................................................................................................................... 44
9.2 —LOADINGS.................................................................................................................................................... 44
9.3 —DESIGN ........................................................................................................................................................ 44
9.4 —PRE-CONSTRUCTION INSPECTIONS ............................................................................................................... 46
9.5 —INSPECTION PRIOR TO PLACEMENT OF CONCRETE ........................................................................................ 47
9.6 —CONCRETE ................................................................................................................................................... 47

CHAPTER 10 —DESIGN FOR COLLAPSIBLE SOILS ................................................................................... 49

10.1 —GENERAL ................................................................................................................................................... 49
10.2 —LOADINGS.................................................................................................................................................. 49
10.3 —DESIGN ...................................................................................................................................................... 49
10.4 —INSPECTIONS .............................................................................................................................................. 51
10.5 —CONCRETE ................................................................................................................................................. 51

CHAPTER 11 —DESIGN FOR SABKHA SOILS ............................................................................................. 59

11.1 —GENERAL ................................................................................................................................................... 59
11.2 —LOADINGS.................................................................................................................................................. 59
11.3 —DESIGN ...................................................................................................................................................... 59
11.4 —REQUIRED PREVENTIVE MEASURES............................................................................................................ 60
11.5 —CONCRETE ................................................................................................................................................. 60
11.6 —REMOVAL OF SABKHA SOILS ...................................................................................................................... 60
11.7 —STABILIZATION .......................................................................................................................................... 61

CHAPTER 12 —DESIGN FOR VIBRATORY LOADS ..................................................................................... 63

12.1 —GENERAL ................................................................................................................................................... 63
12.2 —LOADS ....................................................................................................................................................... 63
12.3 —SOIL BEARING PRESSURES, PILE CAPACITIES AND SETTLEMENTS ............................................................... 63
12.4 —DESIGN REQUIREMENTS ............................................................................................................................. 64

CHAPTER 13 —DAMPPROOFING AND WATERPROOFING ....................................................................... 67

13.1 —SCOPE ........................................................................................................................................................ 67

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TABLE OF CONTENTS

13.2 —DAMPPROOFING......................................................................................................................................... 67
13.3 —WATERPROOFING ...................................................................................................................................... 68
13.4 —SUBSOIL DRAINAGE SYSTEM ...................................................................................................................... 68
13.5 —UNDERGROUND WATER-RETENTION STRUCTURES ..................................................................................... 69

CHAPTER 14 —DEEP FOUNDATIONS .......................................................................................................... 70

14.1 —GENERAL ................................................................................................................................................... 70
14.2 —ANALYSIS .................................................................................................................................................. 70
14.3 —DESIGN AND DETAILING............................................................................................................................. 71
14.4 —INSTALLATION ........................................................................................................................................... 82

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CHAPTER 1 GENERAL

CHAPTER 1—GENERAL

supporting formation which can be safely

1.1—Scope tolerated without causing detrimental
1.1.1 The Saudi Building Code for Soils and settlement or shear failure.
foundations referred to as SBC 303, provides Allowable Lateral Pressure. The lateral pressure
minimum requirements for foundation systems. exerted due to a foundation or earth
This requirement shall govern in all matters pressure which can be safely tolerated
pertaining to design, construction, and material without causing neither shear failure nor
properties wherever this requirement is in conflict detrimental lateral movement.
with requirements contained in other standards Augered Uncased Piles. Piles constructed by
referenced in this code. depositing concrete into an uncased
augered hole, either during or after the
1.2—Design basis withdrawal of the auger.
1.2.1 Allowable bearing pressures, allowable Backfill. Earth filling a trench or an excavation
stresses and design formulas provided in this code under or around a building.
shall be used with the allowable stress design load Building Official. The officer or other designated
combinations specified in Section 2.4 SBC 301. authority charged with the administration
The quality and design of materials used and enforcement of this code, or his duly
structurally in excavations and foundations shall authorized representatives.
comply with the requirements specified in SBC Borehole. A hole made by boring into the ground
301, SBC 304, SBC 305 of the Saudi Building to study stratification, to obtain natural
Code, and ACI 360. Excavations and fills shall also resources, or to release underground
comply with SBC 201. pressures.
Caisson Piles. Cast-in-place concrete piles
1.3—Definitions extending into bedrock. The upper portion
1.3.1 The following words and terms shall, for of a caisson pile consists of a cased pile that
the purpose of this code, have the meanings shown extends to the bedrock. The lower portion
herein. of the caisson pile consists of an uncased
socket drilled into the bedrock.
Acceptance Level. The vibration level
Cantilever Reinforced Concrete Wall. A rigid
(displacement, velocity, or acceleration) at
wall consisting of a concrete stem and base
which a machine can run indefinitely
slab which forms an inverted T.
without inducing vibration related
Cantilever or Strap Footing. A setup of a concrete
maintenance.
beam placed on two adjacent footings
Active Zone. The upper zone of soil deposit
which support concentrated loads exerted
affected by the seasonal variations in
at or close to the edge of the beam. The
moisture content.
strap footing is used to connect an
Alarm Level. The vibration level at which a
eccentrically loaded column footing to an
machine is considered to have developed a interior column such that the moment
defect that will result in related downtime.
caused from eccentricity is transmitted to
This level is usually higher than the
the interior column footing to obtain
acceptance level to allow for conservatism
uniform soil pressure beneath both
and machinery variance and is
footings.
recommended as 1.5 times the acceptance Cavity. An underground opening with widely
level but may be varied, depending on
varying sizes caused mainly by solution of
specific experience or operational
rock materials by water.
requirements.
Collapse Index The percentage of vertical relative
Allowable Foundation Pressure. The vertical
magnitude of soil collapse determined at
pressure exerted by a foundation on a 200 kPa as per ASTM D 5333.

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CHAPTER 1 GENERAL

Collapse Potential. The percentage of vertical the diameter of the remainder of the pile.
relative magnitude of soil collapse The enlarged base is designed to increase
determined at any stress level as per ASTM the load-bearing area of the pile in end
D 5333. bearing.
Collapsible Soils. Soil deposits that are Erosion. The wearing away of the ground surface
characterized by sudden and large volume as a result of the movement of wind and
decrease upon wetting. These deposits are water.
comprised primarily of silt or fine sand- Excavation. The mechanical or manual removal of
sized particles with small amounts of clay, earth material.
and may contain gravel. Collapsible soils Expansion Index The percent swell of soil
have low density, but are relatively stiff and determined in accordance with ASTM-
strong in their dry state. D4829 multiplied by fraction passing No. 4
Column. A structural member with a ratio of sieve multiplied by 100.
height-to-least-lateral dimension exceeding Expansion Joints. Intentional plane of weakness
three, used primarily to support axial between parts of a concrete structure
compressive loads. designed to prevent the crushing and
Combined Footing. A structural unit or assembly distortion, including displacement,
of units supporting more than one column buckling, warping of abutting concrete
load. structural units that might otherwise be
Compaction. Increasing the dry density of soils by developed by expansion, applied loads, or
means such as impact or by rolling the differential movements arising from the
surface layers. configuration of the structure or its
Contact Pressure. The pressure acting at and settlement.
perpendicular to the contact area between Expansive Soil. A soil or rock material that has a
footing and soil, produced by the weight of potential for shrinking or swelling under
the footing and all other forces acting on it. changing moisture conditions.
Continuous or Strip Footing. A combined footing Factor of Safety. The ratio of ultimate bearing
of prismatic or truncated shape, supporting capacity to the allowable load-bearing.
two or more columns in a row. Continuous Fill. A deposit of earth material placed by artificial
or strip footings may be of fixed thickness means.
or upper face can be stepped or inclined Flexural Length. The length of a pile from the first
with inclination or steepness not exceeding point of zero lateral deflection to the
1 unit vertical in 2 units horizontal. underside of the pile cap or grade beam.
Deep Foundation. A foundation element that does Footing. That portion of the foundation of a
not satisfy the definition of a shallow structure which spreads and transmits loads
foundation. directly to the soil.
Distortion Resistance. Distortion resistance Foundation. The portion of a structure which
corresponds to moment resistance to transmits the building load to the ground.
bending of beams, columns, footings and Helical Pile. Manufactured steel deep foundation
joints between them. element consisting of a central shaft and
Drilled Shaft. A cast-in-place deep foundation one or more helical bearing plates. A
element constructed by drilling a hole (with helical pile is installed by rotating it into the
or without permanent casing) into soil or ground. Each helical bearing plate is
rock and filling it with fluid concrete. formed into a screw thread with a uniform
Driven Uncased Piles. Piles constructed by driving defined pitch.
a steel shell into the soil to shore an Geotechnical Engineer. An engineer
unexcavated hole that is later filled with knowledgeable and experienced in soil and
concrete. The steel casing is lifted out of rock engineering.
the hole during the deposition of the Geotechnical Engineering. The application of the
concrete. principles of soils and rock mechanics in
Effective Depth of Section. The distance measured the investigation, evaluation and design of
from the extreme compression fiber to the civil works involving the use of earth
centroid of tension reinforcement. materials and the inspection and/or testing
Enlarged Based Piles. Cast-in-place concrete piles of the construction thereof.
constructed with a base that is larger than

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CHAPTER 1 GENERAL

Grade. Grade is the vertical location of the ground machinery (train) is above all natural
surface. frequencies of the system.
Grade Beam. A continuous beam subject to flexure Machine Support/Foundation System. A system
longitudinally, loaded by the line of consisting of the machinery (train)
columns it supports. including base plate and the foundation,
Gravity Concrete Wall. A gravity wall consists of support structure plus all piers, equipment
mass concrete, generally without and process piping supported on the
reinforcement. It is proportioned so that the foundation or machinery. The supporting
resultant of the forces acting on any internal soil, piling or structure shall be considered
plane through the wall falls within, or close part of the machine foundation system.
to, the kern of the section. Mat Area. The contact area between mat
Grid Foundation. A combined footing, formed by foundation and supporting soil.
intersecting continuous footings, loaded at Mat Foundation. A continuous footing supporting
the intersection points and covering much an array of columns in several rows in each
of the total area within the outer limits of direction, having a slab like shape with or
assembly. without depressions or openings, covering
Group R Occupancy. See SBC 201. an area of at least 75 % of the total area
Group U Occupancy. See SBC 201. within the outer limits of the assembly.
Heavy Machinery. Any machinery having rotating Micropile. A bored, grouted-in-place deep
or reciprocating masses as the major foundation element that develops its load-
moving parts (such as compressors, pumps, carrying capacity by means of a bond zone
electric motors, diesel engines and in soil, bedrock or a combination of soil and
turbines). bedrock.
High-Tuned System. A machine Mixed System. A machine support/foundation
support/foundation system in which the system having one or more of its natural
operating frequency (range) of the frequencies below and the rest above the
machinery (train) is below all natural operating frequency (range) of the
frequencies of the system. machinery (train).
Influence Zone. The zone under a foundation Modulus of Elasticity. The ratio of normal stress
within the vertical stress contours of 10% to corresponding strain for tensile or
of the applied pressure. compressive stresses below proportional
Karst Formation. A type of topography that is limit of material.
formed by limestone, dolomite, marble, Modulus of Subgrade Reaction. The ratio
gypsum, anhydrite, halite or other soluble between the vertical pressure against the
rocks. Its formation is the result of chemical footing or mat and the deflection at a point
solution of these rocks by percolating of the surface of contact.
waters that commonly follow the pre- Mortar. A mixture of cementitious material and
existing joint patterns and enlarge them to aggregate to which sufficient water and
caverns. Sinkholes and solution cavities at approved additives, if any, have been added
or near the ground surface are characteristic to achieve a workable, and plastic
features of karst, and pose a hazard in the consistency.
Eastern and Central regions of Saudi Natural Frequency. The frequency with which an
Arabia. Collapse features are widespread in elastic system vibrates under the action of
these regions and are commonly associated forces inherent in the system and in the
with carbonate and evaporite formations absence of any externally applied force.
that have been subjected to karst Net Pressure. The pressure that can be applied to
development during Quaternary pluvial the soil in addition to the overburden due to
epochs. the lowest adjacent grade.
Lateral Sliding Resistance. The resistance of Overburden. The weight of soil or backfill from
structural walls or foundations to lateral base of foundation to ground surface.
sliding, and it is controlled by interface Overturning. The horizontal resultant of any
friction and vertical loads. combination of forces acting on the
Low-Tuned System. A machine structure tending to rotate as a whole about
support/foundation system in which the a horizontal axis.
operating frequency (range) of the

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CHAPTER 1 GENERAL

Pier Foundations. Isolated cast-in-place concrete Sabkhas. Salt bearing arid climate sediments
structural elements extending into firm covering vast areas of the coasts of Saudi
materials. Piers are relatively short in Arabia. These soils either border partially
comparison to their width, with lengths less land-locked seas or cover a number of
than or equal to 12 times the least continental depressions. The development
horizontal dimension of the pier. Piers of this material is due to low wave energy
derive their load-carrying capacity through allowing the settlement of silt and clay
skin friction, through end bearing, or a particles to take place and then be loosely
combination of both. cemented by soluble material. Varying
Pile Foundations. Concrete or steel structural quantities of calcium carbonate,
elements either driven into the ground or magnesium carbonate, calcium sulphate
cast in place. Piles are relatively slender in and calcium, magnesium, and sodium
comparison to their length, with lengths chlorides are found. The sabkha sediments
exceeding 12 times the least horizontal are highly variable in lateral and vertical
dimension. Piles derive their load-carrying extent; various soil types, primarily
capacity through skin friction, end bearing, composed of clays, silts, fine sands, and
or a combination of both. organic matter are interlayered at random.
Pressed Edge. The edge of footing or mat along In general, sabkha sediments are
which the greatest soil pressure occurs characterized by high void ratios and low
under the condition of overturning. dry densities. Accordingly, upon wetting
Rectangular Combined Footing. A combined sabkha soil is renowned for being highly
footing used if the column which is compressible material with low bearing
eccentric with respect to a spread footing resistance, and hence considered among the
carries a smaller load than the interior weakest of foundation materials.
columns. Settlement. The gradual downward movement of
Registered Design Professional. An individual an engineering structure, due to
who is registered or licensed to practice the compression of the soil below the
respective design profession as defined by foundation.
the statutory requirements of the Shallow Foundation. a relatively near-surface
professional registration laws of the state or individual or strip footing, a mat
jurisdiction in which the project is to be foundation, a slab-on-grade foundation or a
constructed. similar foundation element.
Reinforced Concrete. Structural concrete Shoring. The process of strengthening the side of
reinforced with no less than the minimum excavation during construction stage.
amounts of non-prestressed reinforcement Slope. The inclined surface of any part of the
as specified in SBC 304. earth’s surface.
Reinforcement. A material that conforms to SBC Socketed Drilled Shaft. A drilled shaft with a
304 Section 3.5, excluding prestressing permanent pipe or tube casing that extends
steel unless specifically included. down to bedrock and an uncased socket
Retaining Walls. Structures that laterally support drilled into the bedrock.
and provide stability for soils or other Soils. Un-cemented or weakly cemented
materials, where existing conditions do not accumulation of solid particles that have
provide stability with either natural or resulted from the disintegration of rocks.
artificial slope. Soil Mechanics. The branch of geotechnical
Rocks. Natural aggregate of minerals or engineering that deals with the physical
mineraloids that are connected together by properties of soil and the behavior of soil
strong bonds or attractive forces and have masses subjected to various types of forces.
some degree of chemical and mineralogical It applies the basic principles of kinematics,
constancy. dynamics, fluid mechanics, and solid
Rock Quality Designation (RQD). An index or mechanics to soils.
measure of the quality of a rock mass, and Spiral Reinforcement. Continuously wound
is calculated as summation of length of reinforcement in the form of a cylindrical
intact pieces of core greater than 100 mm in helix.
length divided by the whole length of core Spread Footing. A concrete pad supporting
advance. column load. It can take a rectangular,

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CHAPTER 1 GENERAL

square or a circular shape and having a resonance forces of low-tuned or mixed

uniform or tapered thickness not less than systems during start-up or shut-down.
250 mm. Trapezoidal-Shaped Combined Footing. A
Spring Constant. The soil resistance in load per combined footing used when the column
unit deflection obtained as the product of which has too limited space for a spread
the contributory area and coefficient of footing carries the larger load.
vertical subgrade reaction. Underpinning. The process of strengthening and
Steady-State Dynamic Force. Any dynamic force stabilizing the foundation of an existing
which is periodic in nature and generated building or other structure. Underpinning
during normal operating conditions, such as may be necessary for a variety of reasons
centrifugal forces due to unbalances in including, but not limited to, the original
rotating machinery or piston forces in foundation is simply not strong enough or
reciprocating machinery. stable enough, the use of the structure has
Steel-Cased Piles. Piles constructed by driving a changed, the properties of the soil
steel shell into the soil to shore an supporting the foundation may have
unexcavated hole. The steel casing is left changed or was mischaracterized during
permanently in place and filled with planning, the construction of nearby
concrete. structures necessitates the excavation of
Support/Foundation. The part of the machine soil supporting existing foundation.
support not supplied by the equipment Underpinning is accomplished by
manufacturer as part of the machinery extending the foundation in depth or in
(train). This may include but is not limited breadth so it either rests on a stronger soil
to piers, concrete mat or block, pilings, stratum or distributes its load across a
steel structures, anchor bolts and embedded greater area.
foundation plates. Wall Footing. A strip footing supporting a wall
Surcharge. The load applied to ground surface such that the centerlines of the footing and
above a foundation, retaining wall, or the wall coincide.
slope. Water Table. The planar surface between the zone
Swell Pressure. The maximum applied stress of saturation and the zone of aeration. Also
required to maintain constant volume of an known as free-water elevation; free water
inundated sample in the oedometer. surface; groundwater level; groundwater
Table Top. A reinforced concrete structure surface, groundwater table; level of
supporting elevated machinery. saturation; phreatic surface; plane of
Total Core Recovery (TCR). The total length of saturation; saturated surface; water level;
rock pieces recovered divided by the total and waterline.
length of core advance. Weep Holes. Openings used in retaining walls to
Transient Dynamic Force. T Any dynamic force permit passage of water from the backfill to
which is short term in nature such as the front of the wall.
starting torques or short circuit moments in
electrical machinery, hydraulic forces,

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CHAPTER 2 GEOTECHNICAL INVESTIGATIONS

CHAPTER 2—GEOTECHNICAL INVESTIGATIONS

2.1—General (1) Lateral distribution and thickness of the

soil and rock strata within the zone of
2.1.1 Geotechnical investigations shall be
influence of the proposed construction.
conducted in accordance with Section 2.2 and
reported in accordance with Section 2.6 . Where (2) Suitability of the site for the proposed
required by the building official or where work.
geotechnical investigations involve in-situ testing, (3) Proposal of best method for construction
laboratory testing or engineering calculations, such on the site.
investigations shall be conducted by a registered
design professional. (4) Physical and engineering properties of
the soil and rock formations.
2.1.2 Investigations required. Geotechnical
investigations shall be conducted in accordance (5) Groundwater conditions with
with Sections 2.1.3 through 2.2.3 . consideration of seasonal changes and
the effects of extraction due to
Exception: The building official shall be permitted
construction.
to waive the requirement for a geotechnical
investigation where satisfactory data from adjacent (6) Hazardous conditions including unstable
areas is available that demonstrates an investigation slopes, active or potentially active faults,
is not necessary for any of the conditions in Sections regional seismicity, floodplains, ground
2.2.3.1 through 2.2.3.6 and Sections 2.2.3.11 and subsidence, collapse, and heave
2.2.3.12. potential.
2.1.2.1 No site investigation report is needed if the (7) Changes that may arise in the
building meets the following combined criteria: environment and the effects of these
changes on the proposed and adjacent
(1) The net applied pressure on the buildings.
foundation is less than 50 kPa.
(8) Advice on the suitability of alternative
(2) There are no dynamic or vibratory loads location for the proposed building, if
on the building. exists.
(3) Questionable or problematic soil is not (9) Thorough understanding of all
suspected underneath the building. subsurface conditions that may affect the
(4) Cavities are not suspected underneath the proposed building.
footing of the building.
2.2—Scope of investigation
2.1.3 Basis of investigation. Soil classification
2.2.1 The scope of the geotechnical investigation
shall be based on observation and any necessary
including the number and types of borings or
tests of the materials disclosed by borings, test pits
soundings, the equipment used to drill or sample,
or other subsurface exploration made in appropriate
the in-situ testing equipment and the laboratory
locations. Additional studies shall be made as
testing program shall be determined by a registered
necessary to evaluate slope stability, soil strength,
design professional.
position and adequacy of load-bearing soils, the
effect of moisture variation on soil-bearing 2.2.2 Qualified representative. The
capacity, compressibility, liquefaction and investigation procedure and apparatus shall be in
expansiveness. accordance with generally accepted engineering
practice. The registered design professional shall
2.1.4 Objectives. Geotechnical site investigation
have a fully qualified representative on site during
shall be planned and executed to determine the
all borings or sampling operations.
following:

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CHAPTER 2 GEOTECHNICAL INVESTIGATIONS

2.2.3 Investigated conditions. Geotechnical (8) Designation of bearing stratum or strata.

investigations shall be conducted as indicated in
(9) Reductions for group action, where
Sections 2.2.3.1 through 2.2.3.12 .
necessary.
2.2.3.1 Classification. Soil materials shall be
2.2.3.6 Rock strata. Where subsurface
classified in accordance with ASTM D 2487.
explorations at the project site indicate variations or
Where required, soils are to be classified in in the structure of the rock upon which foundations
accordance with ASTM D2487. This standard are to be constructed, a sufficient number of borings
provides a system for classifying soils for shall be drilled to sufficient depths to assess the
engineering purposes based on laboratory competency of the rock and its load-bearing
determination of particle size Where required, soils capacity.
are to be classified in accordance with ASTM
2.2.3.6.1 Rock cavities. In areas of karst
D2487. This standard provides a system for
formations, the building official shall require
classifying soils for engineering purposes based on
geotechnical investigation to determine the
laboratory determination of particle size.
potential sizes and locations of cavities underneath
2.2.3.2 Questionable soil. Where the classification, the building. If cavities are encountered, such
strength or compressibility of the soil is in doubt, or investigation shall recommend remedies and
where a load-bearing value superior to that construction procedures.
specified in this code is claimed, the building
2.2.3.7 Excavation near foundations. Where
official shall be permitted to require that a
excavations will reduce support from any
geotechnical investigation be conducted.
foundation, a registered design professional shall
2.2.3.3 Problematic soils. In areas likely to have prepare an assessment of the structure as
expansive, collapsible, or sabkha soils, the building determined from examination of the structure, the
official shall require geotechnical investigation to review of available design documents and, if
determine whether such soils do exist. necessary, excavation of test pits. The registered
design professional shall determine the
2.2.3.4 Ground-water table. A subsurface soil
requirements for underpinning and protection and
investigation shall be performed to determine
prepare site specific plans, details and sequence of
whether the existing groundwater table is within the
work for submission. Such support shall be
influence zone underneath the foundation of the
provided by underpinning, sheeting and bracing, or
building.
by other means acceptable to the building official.
2.2.3.5 Deep foundations. Where deep
2.2.3.8 Compacted fill material. Where shallow
foundations will be used, a geotechnical
foundations will bear on compacted fill material
investigation shall be conducted and shall include
more than 300 mm in depth, a geotechnical
all of the following, unless sufficient data upon
investigation shall be conducted and shall include
which to base the design and installation is
all of the following:
otherwise available:
(1) Specifications for the preparation of the
(1) Recommended deep foundation types
site prior to placement of compacted fill
and installed capacities.
material.
(2) Recommended center-to-center spacing
(2) Specifications for material to be used as
of deep foundation elements.
compacted fill.
(3) Driving criteria.
(3) Test methods to be used to determine the
(4) Installation procedures. maximum dry density and optimum
moisture content of the material to be
(5) Field inspection and reporting
used as compacted fill.
procedures (to include procedures for
verification of the installed bearing (4) Maximum allowable thickness of each
capacity where required). lift of compacted fill material.
(6) Load test requirements. (5) Field test method for determining the in-
place dry density of the compacted fill.
(7) Suitability of deep foundation materials
for the intended environment.

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CHAPTER 2 GEOTECHNICAL INVESTIGATIONS

(6) Minimum acceptable in-place dry D, E or F, the geotechnical investigation required

density expressed as a percentage of the by Section 2.2.3.11 shall also include all of the
maximum dry density determined in following as applicable:
accordance with Item 3.
(1) The determination of dynamic seismic
(7) Number and frequency of field tests lateral earth pressures on foundation
required to determine compliance with walls and retaining walls supporting
Item 6. more than 1.8 m of backfill height due to
design earthquake ground motions.
2.2.3.9 Controlled low-strength material
(CLSM). Where shallow foundations will bear on (2) The potential for liquefaction and soil
controlled low-strength material (CLSM), a strength loss evaluated for site peak
geotechnical investigation shall be conducted and ground acceleration, earth-quake
shall include all of the following: magnitude and source characteristics
consistent with the maximum considered
(1) Specifications for the preparation of the
earthquake ground motions. Peak ground
site prior to placement of the CLSM.
acceleration shall be determined based
(2) Specifications for the CLSM. on one of the following:
(3) Laboratory or field test method(s) to be (i) A site-specific study in
used to determine the compressive accordance with Section 21.5 of
strength or bearing capacity of the SBC 301.
CLSM. (ii) In accordance with Section
11.8.3 of SBC 301.
(4) Test methods for determining the
acceptance of the CLSM in the field. (3) An assessment of potential consequences
of liquefaction and soil strength loss
(5) Number and frequency of field tests
including, but not limited to, the
required to determine compliance with
following:
Item 4.
(i) Estimation of total and
2.2.3.10 Alternate setback and clearance. Where
differential settlement.
setbacks or clearances other than those required in
(ii) Lateral soil movement.
Section 5.3 are desired, the building official shall be
(iii) Lateral soil loads on
permitted to require a geotechnical investigation by
foundations.
a registered design professional to demonstrate that
(iv) Reduction in foundation
the intent of Section 5.3 would be satisfied. Such an
soil-bearing capacity and lateral
investigation shall include consideration of
soil reaction.
material, height of slope, slope gradient, load
(v) Soil downdrag and reduction in
intensity and erosion characteristics of slope
axial and lateral soil reaction for
material.
pile foundations.
2.2.3.11 Seismic Design Category C through F. (vi) Increases in soil lateral
For structures assigned to Seismic Design Category pressures on retaining walls.
C, D, E or F, a geotechnical investigation shall be (vii) Flotation of buried structures.
conducted, and shall include an evaluation of all of
(4) Discussion of mitigation measures such
the following potential geologic and seismic
as, but not limited to, the following
hazards:
(i) Selection of appropriate
(1) Slope instability.
foundation type and depths.
(2) Liquefaction. (ii) Selection of appropriate
(3) Total and differential settlement. structural systems to
accommodate anticipated
(4) Surface displacement due to faulting or displacements and forces.
seismically induced lateral spreading or (iii) Ground stabilization.
lateral flow. (iv) Any combination of these
2.2.3.12 Seismic Design Category D through F. measures and how they shall be
For structures assigned to Seismic Design Category

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CHAPTER 2 GEOTECHNICAL INVESTIGATIONS

considered in the design of the (1) Very soft, with SPT values in the range
structure. of 0 to 8, determined in accordance with
ASTM D1586.
2.3—Soil classification
(2) Precipitated salts of different sizes,
2.3.1 Where required, soils shall be classified in
shape, and composition within the
accordance with Sections 2.3.2, 2.3.3, 2.3.4, or
sediments.
2.3.5.
(3) High soluble salt content.
2.3.2 General. For the purposes of this section,
the definition and classification of soil materials for (4) Soil exhibits significant variations in its
use in Table 4-1 shall be in accordance with ASTM chemical composition.
D 2487. (5) Soil exhibits high degree of variability of
2.3.3 Expansive soils. Soils meeting all four of its sediments in both vertical and lateral
the following provisions shall be considered extent within a considerably short
expansive. Compliance with Items 1, 2 and 3 shall distance.
not be required if the test prescribed in Item 4 is (6) Upon wetting soil becomes impassible.
conducted:
2.4—Investigation
(1) Plasticity index of 15 or greater,
determined in accordance with ASTM D 2.4.1 Soil investigation shall be based on
4318. observation and any necessary tests of the materials
disclosed by borings, test pits or other subsurface
(2) More than 10 percent of the soil particles
exploration made in appropriate locations.
pass a No. 200 sieve (75 micrometers),
Additional studies shall be made as necessary to
determined in accordance with ASTM D
evaluate slope stability, soil strength, position and
422.
adequacy of load-bearing soils, the effect of
(3) More than 10 percent of the soil particles moisture variation on soil-bearing capacity,
are less than 5 micrometers in size, compressibility, liquefaction, expansiveness, and
determined in accordance with ASTM D collapsibility.
422.
2.4.2 Exploratory boring. The scope of the
(4) Expansion index greater than 20, geotechnical investigation including the number
determined in accordance with ASTM D and types of borings or soundings, the equipment
4829. used to drill and sample, the in-situ testing
equipment and the laboratory testing program shall
2.3.4 Collapsible soils. Soils meeting all four of
be determined by a registered design professional .
the following provisions shall be considered
In areas likely to have problematic soils, field
collapsible. Compliance with Items 1, 2 and 3 shall
explorations shall include:
not be required if the test prescribed in Item 4 is
conducted: (1) Investigations of soils between the
ground surface and the bottom of the
(1) Desiccated Alluvial (Wadi) soils.
foundation, as well as materials beneath
(2) Dry field density less than 17 kN/m3 the proposed depth of foundation.
determined in accordance with ASTM
(2) Evaluations and interpretations of the
D1556.
environmental conditions that would
(3) Clay content 10 to 30 percent, contribute to moisture changes and their
determined in accordance with ASTM probable effects on the behavior of such
D422. soils.
(4) Collapse index greater than 1-percent, 2.4.3 Number of boreholes. The minimum
determined in accordance with ASTM number of boreholes in a given site shall be taken in
D5333. accordance with Table 2-1 and its provisions. The
values included in Table 2-1 shall be considered as
2.3.5 Sabkha soils. Soils meeting the following
minimum guideline.
shall be suspected as sabkha soils:
2.4.4 Depth of boreholes. The depth of
boreholes shall cover all strata likely to be affected

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CHAPTER 2 GEOTECHNICAL INVESTIGATIONS

by the loads from the building and adjacent (2) The depth of sampling shall be at least as
buildings. The minimum depth of boreholes shall be deep as the probable depth to which
taken from Table 2-1 . moisture changes will occur but shall not
be less than 2 times the minimum width
2.5—Soil boring and sampling of foundation to a maximum of 30 meters
2.5.1 The soil boring and sampling procedure and a minimum of three base diameters
and apparatus shall be in accordance with generally beneath the base of shaft foundations.
accepted engineering practice. The registered
(3) Undisturbed samples shall be obtained at
design professional shall have a fully qualified
intervals of not greater than 1500 mm of
representative on the site during all boring and
depth.
sampling operations.
(4) In the event undisturbed samples cannot
2.5.2 Soil boring and sampling of expansive
be obtained from a borehole, test pits
soils. In areas likely to have expansive soils the
shall be excavated to sufficient depth and
following shall be taken into considerations:
dry density of the soil shall be measured
(1) Air drilling shall be used to maintain the at various horizons in the pit.
natural moisture contents of the samples
(5) Where possible, hand carved undisturbed
more effectively.
samples taken in a vertical direction shall
(2) The use of lubricant that might react with be obtained for odometer testing.
the soil and change its properties shall be Alternately, plate load test in unsoaked
avoided. and soaked conditions shall be
performed to determine the most critical
(3) The depth of sampling shall be at least as
collapse potential below foundation
deep as the probable depth to which
level.
moisture changes will occur (active
zone) but shall not be less than 1.5 times 2.5.4 Soil boring and sampling of sabkha soils.
the minimum width of slab foundations In areas likely to have sabkha soils the following
to a maximum of 30 meters and a shall be taken into considerations:
minimum of three base diameters
(1) A full chemical analyses on soil and
beneath the base of shaft foundations.
ground water to determine the average
(4) Undisturbed samples shall be obtained at and range of the aggressive compounds
intervals of not greater than 1500 mm of and the variation in content with depth.
depth. Sampling interval may be
(2) Grading of sabkha shall be determined
increased with depth.
by using wet sieving with non-polar
(5) A coating of wax shall be brushed on the solvent (sabkha brine, methylene
sample before wrapping. chloride).
(6) The outer perimeter of the sample shall (3) Basic properties including moisture
be trimmed during the preparation of content and specific gravity shall be
specimens for laboratory tests, leaving determined by using oven drying at 60oC
the more undisturbed inner core. in accordance with ASTM D854 and
ASTM D2216.
(7) The sample shall be taken as soon as
possible, after advancing the hole to the 2.6—Reporting
proper depth and cleaning out the hole,
2.6.1 The soil classification and design load-
and personnel shall be well trained to
bearing capacity shall be shown on the construction
expedite proper sampling, sealing, and
document. Where geotechnical investigations are
storage in sample containers.
required a written report of the investigations shall
2.5.3 Soil boring and sampling of collapsible be submitted to the building official. The
soils. In areas likely to have collapsible soils the geotechnical report shall include, but need not be
following shall be taken into considerations: limited the following information:
(1) Air drilling shall be used to maintain the (1) Introduction with location map depicting
natural moisture content of the samples. adjacent buildings, existing roads, and
utility lines.

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CHAPTER 2 GEOTECHNICAL INVESTIGATIONS

(2) Climatic conditions such as rain rate, strength; and the effects of adjacent
storm water discharge, etc. if relevant loads. The recommendations for
effect is suspected on the soil or rock foundation design must be based on the
formations. facts stated in the report, i.e. on the
borehole records and test data. They must
(3) Description of site topography and
not be based on conjecture.
relevant geological information.
(11) Expected total and differential
(4) A plot showing the location of test
settlements.
borings and/or excavation pits.
(12) Deep foundation information in
(5) A complete record of the soil samples.
accordance with Section 14.2.
(6) A complete record of the borehole log
(13) Combined foundations and mats
with the stand ard penetration test, SPT,
information in accordance with Section
values at the corresponding depths for
8.1 .
soil samples and RQD and TCR values
for rock samples. (14) Special design and construction
provisions for foundations founded on
(7) A record of the soil profile.
problematic soils in accordance with
(8) Elevation of the water table, if CHAPTER 9 , CHAPTER 10 , and
encountered and recommended CHAPTER 11 , as necessary.
procedures for dewatering, if necessary.
(15) Compacted fill material properties and
(9) Brief description of conducted laboratory testing in accordance with Section 3.10 .
and field tests (or its SASO or ASTM
(16) Controlled low-strength material
standards, or equivalent standard
properties and testing in accordance with
number) and a summary of the results.
Section 2.2.3.9 .
(10) Recommendations for foundation type
(17) Recommended sites for waste material
and design criteria, including but not
disposal.
limited to: bearing capacity of natural or
compacted soil; provisions to mitigate (18) Suitability of excavated material for
the effects of problematic soils reuse as fill material in site.
(expansive, collapsible, sabkha, etc.);
mitigation of the effects of liquefaction,
differential settlement and varying soil

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CHAPTER 2 GEOTECHNICAL INVESTIGATIONS

TABL ES OF CHAPTER 2

Table 2-1—Minimum number and minimum depthsof boreholes for

buildingsa,b,c,d,e

MINIMUM DEPTHf
MINIMUM DEPTHf OF
NO. OF BUILT AREA NO. OF OF ONE THIRD OF
STORIES (m2) BOREHOLES TWO THIRDS OF THE
THE BOREHOLES
BOREHOLES (m)
(m)

< 600 3 4 6
g
2 or less 600 – 5000 3 – 10 5 8

> 5000 Special investigation

3-4 < 600 3

600 – 5000 3 – 10g 6-8 9 - 12

> 5000 Special investigation
5 or higher Special investigation
a. If possible, standard penetration tests, SPT, shall be performed at all sites.
b. If questionable soils do exist underneath the building, a minimum of one borehole
shall penetrate all layers containing this soil.
c. Seasonal changes in groundwater table and the degree of saturation shall be
considered.
d. If sufficient data is available, a registered design professional may use number and
depth of boreholes that are different from the tabular values.
e. For foundation of pole and towers, a minimum of one boring with sufficient
depth shall be located in the center of the foundation.
f. Depth is measured from level of foundation bottom.
g. Number of boreholes shall be selected by a registered design professional
based on variations in site conditions, and contractor shall advice if additional
or special tests are required.

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CHAPTER 3 EXCAVATION, GRADING AND FILL

CHAPTER 3—EXCAVATION, GRADING AND FILL

3.1—General (2) Exploratory excavations under the

direction of geotechnical engineers.
3.1.1 Proper safety precautions shall be
considered at all stages of excavation. Special care, (3) An excavation which (a) is less than 600
measures, and techniques shall be followed for mm in depth, or (b) which does not create
excavation below groundwater table. a cut slope greater than 1500 mm in
height and steeper than three units
3.1.1.1 The investigation and report provisions of
horizontal to two units vertical.
CHAPTER 2 shall be expanded to include, but need
not be limited to, the following: (4) A fill less than 300 mm in depth and
placed on natural terrain with a slope
(1) Property limits and accurate contours of
flatter than five units horizontal to one
existing ground and details of terrain and
unit vertical, or less than 1000 mm in
area drainage.
depth, not intended to support structures,
(2) Limiting dimensions, elevations or finish does not exceed 40 cubic meters on any
contours to be achieved by the grading, one lot and does not obstruct a drainage
and proposed drainage channels and course.
related construction.
3.3—Excavations n ear foundations
(3) Detail plans of all surface and subsurface
3.3.1 Excavations for any purposes shall not
drainage systems, walls, cribbing, and
reduce lateral support from any adjacent foundation
other protective systems to be
without first underpinning or protecting the
constructed with, or as a part of, the
foundation against detrimental lateral or vertical
proposed work.
movement, or both.
(4) Location of any buildings or structures
3.3.2 Underpinning. Where underpinning is
on the property where the work is to be
chosen to provide the protection or support of
performed and the location of any
adjacent structures, the underpinning system shall
buildings or structures on adjacent land
be designed and installed in accordance with
which are within 5 m of the property or
provisions of SBC 303 and Chapter 33 of SBC 201.
which may be affected by the proposed
grading operations. 3.3.2.1 Underpinning sequencing. Underpinning
shall be installed in a sequential manner that
(5) Conclusions and recommendations
protects the neighboring structure and the working
regarding the effect of geologic
construction site. The sequence of installation shall
conditions on the proposed construction,
be identified in the approved construction
and the adequacy of sites to be developed
documents.
by the proposed grading.
3.4—Slope limits
3.2—Commencement
3.4.1 Slopes for permanent fill shall not be
3.2.1 Excavation, grading and fill shall not be
steeper than one unit vertical in two units horizontal
commenced without first having obtained a permit
(50-percent slope). Cut slopes for permanent
from the building official.
excavations shall not be steeper than one unit
Exception: Permit shall not be required for the vertical in two units horizontal (50-percent slope).
following: Deviation from the foregoing limitations for cut
slopes shall be permitted only upon the presentation
(1) Grading in an isolated, self-contained
of a soil investigation report acceptable to the
area if there is no apparent danger to
building official and shows that a steeper slope will
private or public property.
be stable and not create a hazard to public or private
property.

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CHAPTER 3 EXCAVATION, GRADING AND FILL

3.5—Surcharge 3.8—Grading designation

3.5.1 No fill or other surcharge loads shall be 3.8.1 The faces of cut and fill slopes shall be
placed adjacent to any building or structure unless prepared and maintained to control against erosion.
such building or structure is capable of All grading in excess of 3500 cubic meters shall be
withstanding the additional loads caused by the fill performed in accordance with the approved grading
or surcharge. Existing foundations which can be plan prepared by a registered design professional ,
affected by any excavation shall be underpinned and shall be designated as “engineering grading”.
adequately or otherwise protected against Grading involving less than 3500 cubic meters shall
settlement and shall be protected against lateral be designated as “regular grading” unless required
movement. by the building official to be considered as
“engineering grading”.
3.6—Placement of backfill
3.8.1.1 For engineering grading, grading plan shall
3.6.1 The excavation outside the foundation shall
be prepared and approved by a registered design
be backfilled with soil that is free of organic
professional. For regular grading, the building
material, construction debris, cobbles and boulders
official may require inspection and testing by an
or a controlled low-strength material (CLSM). The
approved agency. Where the building official has
ground surface shall be prepared to receive fill by
cause to believe that geologic factors may be
removing vegetation, noncomplying fill, topsoil
involved, the grading operation shall conform to
and other unsuitable materials. The backfill shall be
“engineering grading” requirements.
placed in lifts and compacted, in a manner that does
not damage the foundation or the waterproofing or 3.9—Grading and fi ll in flood h azard
dampproofing material. Special inspections of areas
compacted fill shall be in accordance with Section
3.9.1 In flood hazard areas established in Section
2.7 of SBC 302.
1612.3 SBC 201, grading, fill, or both, shall not be
Exception: CLSM need not be compacted. approved:
3.7—Site grading (1) Unless such fill is placed, compacted and
sloped to minimize shifting, slumping
3.7.1 The ground immediately adjacent to the
and erosion during the rise and fall of
foundation shall be sloped away from the building
flood water and, as applicable, wave
at a slope of not less than one unit vertical in 20
action.
units horizontal (5-percent slope) for a minimum
distance of 3000 mm measured perpendicular to the (2) In floodways, unless it has been
face of the wall. If physical obstructions or lot lines demonstrated through hydrologic and
prohibit 3000 mm of horizontal distance, a 5- hydraulic analyses performed by a
percent slope shall be provided to an approved registered design professional in
alternative method of diverting water away from the accordance with standard engineering
foundation. Swales used for this purpose shall be practice that the proposed grading or fill,
sloped a minimum of 2 percent where located or both, will not result in any increase in
within 3000 mm of the building foundation. flood levels during the occurrence of the
Impervious surfaces within 3000 mm of the design flood.
building foundation shall be sloped a minimum of 2
(3) In coastal high hazard areas, unless such
percent away from the building.
fill is conducted and/or placed to avoid
Exception: Where climate or soil conditions diversion of water and waves toward any
warrant, the slope of the ground away from the building or structure.
building foundation shall be permitted to be
(4) Where design flood elevations are
reduced to not less than one unit vertical in 50 units
specified but floodways have not been
horizontal (2 percent slope).
designated, unless it has been
The procedure used to establish the final ground demonstrated that the cumulative effect
level adjacent to the foundation shall account for of the proposed flood hazard area
additional settlement of the backfill. encroachment, when combined with all
other existing and anticipated flood
hazard area encroachment, will not

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CHAPTER 3 EXCAVATION, GRADING AND FILL

increase the design flood elevation more fills within 1.5 m, measured vertically, from the
than 3 m at any point. bottom of the foundation or lowest finished floor
elevation, whichever is lower, within the building
3.10—Compacted fi ll material pad. Oversized fill material shall be placed so as to
3.10.1 Where shallow foundations will bear on assure the filling of all voids with well-graded soil.
compacted fill material, the compacted fill shall Specific placement and inspection criteria shall be
comply with the provisions of an approved stated and continuous special inspections shall be
geotechnical report as set forth in CHAPTER 2 . carried out during the placement of any oversized
fill material.
3.10.2 Exception: Compacted fill material 300
mm in depth or less need not comply with an 3.11—Controlled low -strength m aterial
approved report, provided the in-place dry density (CLSM)
is not less than 90 percent of the maximum dry
density at optimum moisture content determined in 3.11.1 Where shallow foundations will bear on
accordance with ASTM D 1557. The compaction controlled low-strength material (CLSM), the
shall be verified by special inspection in accordance CLSM shall comply with the provisions of an
with Section 1705.6 SBC 201. approved geotechnical report, as set forth in
CHAPTER 2 .
3.10.3 Oversized materials. No rock or similar
irreducible material with a maximum dimension
greater than 300 mm shall be buried or placed in

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CHAPTER 4 PRESUMPTIVE LOAD-BEARING VALUES OF SOILS

CHAPTER 4—PRESUMPTIVE LOAD-BEARING VALUES OF SOILS

4.1—Load combinations 4.3.3 Lateral sliding resistance limit. For clay,

sandy clay, silty clay, and clayey silt, silt and sandy
4.1.1 The presumptive load-bearing values
silt, in no case shall the lateral sliding resistance
provided in Table 4-1 shall be used with the
exceed one-half the dead load.
allowable stress design load combinations specified
in Section 1605.3 of SBC 201. The values of 4.3.4 Increase for depth. The lateral bearing
vertical foundation pressure and lateral bearing pressures specified in Table 4-1 shall be permitted
pressure given in Table 4-1 shall be permitted to be to be increased by the tabular value for each
increased by one-third where used with the additional 300 mm of depth to a maximum of 15
alternative basic load combinations of Section times the tabular value.
1605.3.2 SBC 201 that include wind or earthquake 4.3.5 Increase for poles. Isolated poles for uses
loads. such as flagpoles or signs and poles used to support
4.2—Presumptive load-bearing values buildings that are not adversely affected by a 13 mm
motion at the ground surface due to short-term
4.2.1 The load-bearing values used in design for lateral loads are shall be permitted to be designed
supporting soils at or near the surface shall not using lateral-bearing pressures equal to two times
exceed the values specified in Table 4-1 unless data the tabular values.
to substantiate the use of a higher values are
submitted and approved by the building official. 4.4—Computed load-bearing values
Where the building official has reason to doubt the 4.4.1 It shall be permitted to obtain the ultimate
classification, strength or compressibility of the bearing capacity from appropriate laboratory and/or
soil, the requirements of Section 2.5 shall be field tests including, but need not be limited to,
satisfied. In case of thin soft layers existing between standard penetration test conforming to ASTM
layers of high bearing values, the foundation shall D1586 and plate load test conforming to ASTM
be designed according to the bearing capacity of the D1194. Where the soil to a deep depth is
thin soft layers. homogeneous, the plate load test shall be conducted
4.2.1.1 Presumptive load-bearing values shall apply at the level of footing base. In case the soil consists
to materials with similar physical characteristics of several layers, the test shall be conducted at each
and depositional conditions. layer to a depth equal to not less than twice the
width of footing measured from the bottom of
4.2.1.2 Mud, organic silt, organic clays or
footing. In case there is a large difference between
unprepared fill shall not be assumed to have a
the footing width and plate size, plates of different
presumptive load-bearing capacity unless data to
sizes shall be used to establish the relationship
substantiate the use of such a value are submitted.
between footing width and load-bearing.
Exception: A presumptive load-bearing capacity
4.4.1.1 It shall be permitted to use formulae in the
shall be permitted to be used where the building
computations of ultimate bearing capacity that are
official deems the load-bearing capacity of mud,
of common use in geotechnical engineering practice
organic silt or unprepared fill is adequate for the
or based on a sound engineering judgment and
support of lightweight and temporary structures.
subject to approval to the building official.
4.3—Lateral load resist ance 4.4.2 Effect of water table. The submerged unit
4.3.1 Where the presumptive values of Table 4-1 weight shall be used as appropriate to determine the
are used to determine resistance to lateral loads, the actual influence of the groundwater on the bearing
calculations shall be in accordance with Sections capacity of the soil. The foundation design shall
4.3.2 through 4.3.5 . consider the buoyant forces when groundwater is
above or expected to rise above the foundation
4.3.2 Combined resistance. The total resistance
level.
to lateral loads shall be permitted to be determined
by combining the values derived from the lateral
bearing pressure and the lateral sliding resistance
specified in Table 4-1 .

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CHAPTER 4 PRESUMPTIVE LOAD-BEARING VALUES OF SOILS

TABL ES OF CHAPTER 4

Table 4-1—Presumptive load-bearing values

LATERAL LATERAL SLIDING

VERTICAL BEARING RESISTANCE
FOUNDATION PRESSURE
CLASS OF MATERIALS PRESSURE (kPa/m below Coefficient Cohesion
(kPa)a natural of frictiona (kPa)b
grade)

1. Crystalline bedrock 600 200 0.70

2. Sedimentary and foliated rock 200 60 0.35
3. Sandy gravel and/or gravel (GW
150 30 0.35
and GP)
4. Sand, silty sand, clayey sand,
silty gravel and clayey gravel 100 25 0.25
(SW, SP, SM, SC, GM and GC)
5. Clay, sandy clay, silty clay,
clayey silt, silt and sandy silt 75d 15 6
(CL, ML, MH and CH)
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 4.3 .

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CHAPTER 5 SPREAD FOOTINGS

CHAPTER 5—SPREAD FOOTINGS

5.1—General vertical in three units horizontal shall conform to

Sections 5.3.2 through 5.3.6.
5.1.1 Spread footings shall be designed and
constructed in accordance with Sections 5.1 through 5.3.2 Building clearance from ascending
5.6 . slopes. In general, buildings below slopes shall be
set a sufficient distance from the slope to provide
5.1.2 Supporting soils. Footings shall be built on
protection from slope drainage, erosion and shallow
undisturbed soil, compacted fill material or CLSM.
failures. Except as provided for in Section 5.3.6 and
Compacted fill material shall be placed in
Figure 5-1 , the following criteria will be assumed to
accordance with Section 3.10 . CLSM shall be
provide this protection. Where the existing slope is
placed in accordance with Section 3.11 .
steeper than one unit vertical in one unit horizontal
5.1.3 Stepped Footings. The top surface of (100 percent slope), the toe of the slope shall be
footings shall be level. The bottom surface of assumed to be at the intersection of a horizontal
footings shall be permitted to have a slope not plane drawn from the top of the foundation and a
exceeding one unit vertical in 10 units horizontal plane drawn tangent to the slope at an angle of 45
(10-percent slope). Footings shall be stepped where degrees to the horizontal. Where a retaining wall is
it is necessary to change the elevation of the top constructed at the toe of the slope, the height of the
surface of the footing or where the surface of the slope shall be measured from the top of the wall to
ground slopes is more than one unit vertical in 10 the top of the slope.
units horizontal (10-percent slope).
5.3.3 Foundation setback from descending
5.2—Depth and width of footi ngs slope surface. Foundation on or adjacent to slope
surfaces shall be founded in firm material with an
5.2.1 The minimum depth of footing below the embedment and set back from the slope surface
natural ground level shall not be less than 1200 mm
sufficient to provide vertical and lateral support for
for cohesionless soils, 1500 mm for silty and clay the footing without detrimental settlement. Except
soils and 600 mm to 1200 mm for rocks depending as provided for in Section 5.3.6 and Figure 5-1 , the
on strength and integrity of the rock formations. following setback is deemed adequate to meet the
Where applicable, the depth of footings shall also criteria. Where the slope is steeper than one unit
conform to Sections 5.2.2 through 5.2.3. The vertical in one unit horizontal (100 percent slope),
minimum width of footings shall be 300 mm. the required setback shall be measured from
5.2.2 Adjacent footings. Footings on granular imaginary plane 45 degrees to the horizontal,
soil shall be so located that the line drawn between projected upward from the toe of the slope.
the lower edges of adjoining footings shall not have
5.3.4 Pools. The setback between pools and
a slope steeper than 30 degrees with the horizontal, slopes shall be equal to one-half the building
unless the material supporting the higher footing is footing setback distance required by this section.
braced or retained or otherwise laterally supported That portion of the pool wall within a horizontal
in an approved manner or a greater slope has been distance of 2100 mm from the top of the slope shall
properly established by engineering analysis that is
be capable of supporting the water in the pool
accepted by the building official. without soil support.
5.2.3 Shifting or moving soils. Where it is 5.3.5 Foundation elevation. On graded sites, the
known that the shallow subsoils are of a shifting or top of any exterior foundation shall extend above
moving character, footings shall be carried to a the elevation of the street gutter at point of
sufficient depth to ensure stability. discharge or the inlet of an approved drainage
5.3—Footings on or adjacent to slopes system a minimum of 300 mm plus 2 percent.
Alternate elevations are permitted subject to the
5.3.1 The placement of buildings and structures approval of the building official, provided it can be
on or adjacent to slopes steeper than one unit demonstrated that required drainage to the point of

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CHAPTER 5 SPREAD FOOTINGS

discharge and away from the structure is provided behind equipment, where the grade is not increased
at all locations on the site. more than 300 mm from original design grade or
where approved by the building official.
5.3.6 Alternate setback and clearance.
Alternate setbacks and clearances are permitted, 5.4.1.2 Eccentric loads. When the footings are
subject to the approval of the building official. The subjected to moments or eccentric loads, the
building official shall be permitted to require a maximum stresses shall not exceed the allowable
geotechnical investigation as set forth in CHAPTER bearing capacity of the soil specified in CHAPTER
2 Section 2.2.3.10 . 4 . The centeroid of the loads exerted on the footings
shall coincide with the centeroid of the footing area,
5.4—Design of foo tings and if not possible the eccentricity shall not exceed
5.4.1 General. Footings shall be designed that 1/6 times the dimensions of the footing on both
the allowable bearing capacity of the soil is not sides. For the purpose of estimating the ultimate
exceeded, and that the total and differential load-bearing, the effective width shall be taken as
settlements are tolerable. The design of footings the actual width minus twice the eccentricity.
shall be under the direct supervision of a registered
5.4.1.3 Inclined loads. For design of footings
design professional who shall certify to the building
subjected to inclined loads, it shall be permitted to
official that the footing satisfies the design criteria.
use the following simplified formula or any method
Footings in areas with expansive soils shall be
of analysis, subject to the approval of the building
designed in accordance with the provisions of
official.
CHAPTER 9 . Footings in areas with collapsible
soils shall be designed in accordance with the
provisions of CHAPTER 10 . Footings in areas with
sabkha soils shall be designed in accordance with
   < 1.0 (5-1)

the provisions of CHAPTER 11 . Footings subject to

vibratory loads shall be designed in accordance where:
with the provisions of CHAPTER 12 .
 = Vertical component of inclined load;
5.4.1.1 Design loads. Footings shall be designed
for the most unfavorable effects due to the  = Horizontal component of inclined load;
combinations of loads specified in SBC 301 Section  = Allowable vertical load; and
2.4. The dead load is permitted to include the weight
of foundations, footings and overlying fill. Reduced
live loads, as specified in SBC 301 Section 4.8,
 = Allowable horizontal load.
5.4.1.3.1 Horizontal component shall not exceed
shall be permitted to be used in the design of soil passive resistance along the footing vertical
footings. edge and friction resistance at the footing soil
5.4.1.1.1 Seismic overturning. Where foundations interface taking a factor of safety of 2.
are proportioned using the load combinations of 5.4.1.4 Adjacent loads. Where footings are placed
Section 2.3.2 SBC 301, and the computation of at varying elevations the effect of adjacent loads
seismic overturning effects is by equivalent lateral shall be included in the footing design.
force analysis or modal analysis, the proportioning
shall be in accordance with Section 12.13.4 of SBC 5.4.1.5 Design settlements. Settlements shall be
301. estimated by a registered design professional based
on methods of analysis approved by the building
5.4.1.1.2 Surcharge. No fill or other surcharge official. The least value found from Table 5-1 and
loads shall be placed adjacent to any building or Table 5-2 shall be taken as the allowable differential
structure unless such building or structure is settlement.
capable of withstanding the additional loads caused
by the fill or the surcharge. Existing footings or Exceptions: Structures designed to stand excessive
foundations that will be affected by any excavation total settlement in coastal areas or heavily loaded
shall be underpinned or otherwise protected against structures, like silos and storage tanks, shall be
settlement and shall be protected against allowed to exceed these limits subject to a
detrimental lateral or vertical movement or both. recommendation of a registered design professional
and approval of a building official.
Exception: Minor grading for landscaping
purposes shall be permitted where done with walk-

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CHAPTER 5 SPREAD FOOTINGS

5.4.1.6 Factor of safety. Factor of safety shall not 5.4.2.6 Minimum concrete cover to
be less than 3 for permanent structures and 2 for reinforcement. When the concrete of footings is
temporary structures. Consideration shall be given poured directly on the ground or against excavation
to all possible circumstances including, but not walls the minimum concrete cover to reinforcement
limited to, flooding of foundation soil, removal of shall not be less than 75 mm. This cover shall also
existing overburden by scour or excavation, and satisfy other requirements with regard to concrete
change in groundwater table level. exposure conditions presented in SBC 304.
5.4.2 Concrete Foundations. The design, 5.4.2.7 Concrete cover. The concrete cover
materials and construction of concrete foundations provided for prestressed and nonprestressed
shall comply with Sections 5.4.2.1 through 5.4.2.8 reinforcement in foundations shall be no less than
and the provisions of SBC 304 where applicable. the largest applicable value specified in section
20.6 of SBC 304. Longitudinal bars spaced less
Exception: Where a specific design is not provided,
than 40 mm bundled bars for which the concrete
concrete footings supporting walls of light-frame
cover provided shall also be no less than that
construction are permitted to be designed in
required by Section 20.6.1.3.4 of SBC 304.
accordance with Table 5-3 .
Concrete cover shall be measured from the
5.4.2.1 Concrete or grout strength and mix concrete surface to the outermost surface of the

′
proportioning. Concrete or grout in footings shall
have a specified compressive strength ( ) of not
less than 20 MPa at 28 days.
steel to which the cover requirement applies.
Where concrete is placed in a temporary or
permanent casing or a mandrel, the inside face of
the casing or mandrel shall be considered the
5.4.2.2 Footing seismic ties. Where a structure is
concrete surface.
assigned to Seismic Design Category D, E or F, in
accordance with Chapters 9 through 16, SBC 301, 5.4.2.8 Dewatering. Where footings are carried to
individual spread footings founded on soil defined depths below ground water level, the footings shall
in Section 9.4.2, SBC 301 as Site Class E or F shall be constructed by a method that will provide the
be interconnected by ties. Unless it is demonstrated depositing or construction of sound concrete in dry
that equivalent restraint is provided by reinforced conditions.
concrete beams within slabs on grade or reinforced
5.4.3 Steel grillage footings. Grillage footings of
concrete slabs on grade, ties shall be capable of
structural steel elements shall be separated with
carrying, in tension or compression, a force equal to
approved steel spacers and be entirely encased in
gravity load times the seismic coefficient 
the lesser of the product of the larger footing design

divided by 10 and 25 percent of the smaller footing

concrete with at least 150 mm on the bottom and at
least 100 mm at all other points. The spaces
between the elements shall be completely filled
design gravity load.
with concrete or cement grout.
5.4.2.3 Placement of concrete. Concrete shall be
placed in such a manner as to ensure the exclusion
5.5—Embedded posts and poles
of any foreign matter and to secure a full-size 5.5.1 Designs to resist both axial and lateral loads
foundation. Concrete shall not be placed through employing posts or poles as columns embedded in
water unless a tremie or other method approved by earth or embedded in concrete footings in the earth
the building official is used. Where placed under or shall conform to the requirements of Sections 5.5.2
in the presence of water, the concrete shall be through 5.5.4 .
deposited by approved means to ensure minimum
5.5.2 Limitations. The design procedures
segregation of the mix and negligible turbulence of
outlined in this section are subject to the following
the water.
limitations:
5.4.2.4 Protection of concrete. Water shall not be
(1) The frictional resistance for structural
allowed to flow through the deposited concrete.
walls and slabs on silts and clays shall be
5.4.2.5 Forming of concrete. Concrete footings are limited to one-half of the normal force
permitted to be cast against the earth where, in the imposed on the soil by the weight of the
opinion of the building official, soil conditions do footing or slab.
not require forming. Where forming is required, it
(2) Posts embedded in earth shall not be used
shall be in accordance with Section 20.6 of SBC
to provide lateral support for structural or
304.
nonstructural materials such as plaster,

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CHAPTER 5 SPREAD FOOTINGS

masonry or concrete unless bracing is

provided that develops the limited
deflection required.
 = 4.25ℎ/ (5-3)

5.5.2.1 Wood poles shall be treated in accordance or alternatively

with AWPA U1 for sawn timber posts (Commodity
Specification A, Use Category 4B) and for round
timber posts (Commodity Specification B, Use
 = 4.25(/) (5-4)

Category 4B).
where:
5.5.3 Design criteria. The depth to resist lateral
loads shall be determined by the design criteria  = Moment in the post at grade, in kN-m; and
established in Sections 5.5.3.1 through 5.5.3.3, or by
other methods approved by the building official.
= Allowable lateral soil-bearing pressure in kPa
as set forth in Section 4.3 based on a depth equal to
5.5.3.1 Nonconstrained. The following formula the depth of embedment.
shall be used in determining the depth of
5.5.3.3 Vertical load. The resistance to vertical
embedment required to resist lateral loads where no
loads shall be determined by the allowable soil-
constraint is provided at the ground surface, such as
bearing pressure set forth in Table 4-1 .
rigid floor or rigid ground surface pavement, and
where no lateral constraint is provided above the 5.5.4 Backfill. The backfill in the space around
ground surface, such as a structural diaphragm. columns not embedded in poured footings shall be
done by one of the following methods:

 = 0.5114.36ℎ/ (5-2)
(1) Backfill shall be of concrete with a
specified compressive strength of not
less than 20 MPa at 28 days. The hole
shall not be less than 100 mm larger than
where: the diameter of the column at its bottom
= Depth of embedment in earth in meter but not
over 3600 mm for purpose of computing lateral
or 100 mm larger than the diagonal
dimension of a square or rectangular
pressure; column.

ℎ 
= Distance in meter from ground surface to point
of application of “ ”;
(2) Backfill shall be of clean sand. The sand
shall be thoroughly compacted by

 = 2.34/ ;
tamping in layers not more than 200 mm
in depth.
 = Applied lateral force in kN; (3) Backfill shall be of controlled low-
= Allowable lateral soil-bearing pressure in kPa
as set forth in Section 4.3 based on a depth of one-
strength material (CLSM) placed in
accordance with Section 3.11 .
third the depth of embedment; and 5.6—Seismic requirements
 = Diameter of round post or footing or diagonal
dimension of square post or footing in meter.
5.6.1 For footings of structures assigned to
Seismic Design Category C, D, E, or F provisions
5.5.3.2 Constrained. The following formula shall of SBC 301 and SBC 304 shall apply when not in
be used to determine the depth of embedment conflict with the provisions of CHAPTER 5 .
required to resist lateral loads where constraint is
provided at the ground surface, such as by a rigid
floor or pavement.

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CHAPTER 5 SPREAD FOOTINGS

TABLES AND FIGURES OF CHAPTER 5

Table 5-1—Maximum allowable total settlement

TOTAL SETTLEMENT
FOOTING TYPE (mm)
CLAY SAND
Spread Footings 60 40
Mat Foundations 80 60

Table 5-2—Maximum allowable angular distortion

BUILDING TYPE
Multistory reinforced concrete structures
L/H /
--- 0.0015
founded on mat foundation
Steel frame structure with side sway --- 0.008
Reinforced concrete or steel structure with
--- 0.002-0.003
interior or exterior glass or panel cladding
Reinforced concrete or steel structure with  5 0.002
interior or exterior glass or panel cladding 0.001
 3
Slip and high structures as silos and water tanks
--- 0.002
founded on stiff mat foundations
Cylindrical steel tank with fixed cover and
--- 0.008
founded on flexible footing
Cylindrical steel tank with portable cover and
--- 0.002-0.003
founded on flexible footing

 δ 
Rail for supporting hanged lift ---
= Building length; = Span between adjacent footings;
the structure; = Differential settlement
 0.003
= Overall height of

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CHAPTER 5 SPREAD FOOTINGS

Table 5-3—Footings supporting walls of light-frame construction a, b, c, d, e

NUMBER OF FLOORS WIDTH OF THICKNESS OF

SUPPORTED BY THE FOOTING FOOTING
FOOTING f (mm) (mm)
1 300 150
2 375 150
3 450 200
a. Depth of footings shall be in accordance with Section 5.2.
b. The ground under the floor is permitted to be excavated to the elevation of the top of the footing.
c. Interior-stud-bearing walls are permitted to be supported by isolated footings. The footing width and length
shall be twice the width shown in this table, a nd footings shall be spaced not more than 1800 mm on center.
d. See SBC 304 Chapter 21 for additional requirements for footings of structures assigned to Seismic Design
Category C or D, E, or F.
e. For thickness of foundation walls, see CHAPTER 6.
f. Footings are permitted to support a roof in addition to the stipulated number of floors. Footings supporting
roof only shall be as r equired for supporting one floor.

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CHAPTER 5 SPREAD FOOTINGS

Figure 5-1—Foundation clearances from slopes.

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CHAPTER 6 FOUNDATION WALLS

CHAPTER 6—FOUNDATION WALLS

6.1—General 6.6.3 Concrete foundation walls. Concrete

foundation walls shall comply with the following:
6.1.1 Foundation walls shall be designed and
constructed in accordance with Sections 6.2 through (1) The thickness shall comply with the
6.6 . Foundation walls shall be supported by requirements of Table 6-1
foundations designed in accordance with (2) The size and spacing of vertical
CHAPTER 5 .
reinforcement shown in Table 6-1 are
6.2—Design lateral soil loads based on the use of reinforcement with a
minimum yield strength of 420 MPa.
6.2.1 Foundation walls shall be designed for the Vertical reinforcement with a minimum
lateral soil loads set forth in Section 1610 of SBC yield strength of 270 MPa or 350 MPa
201. shall be permitted, provided the same
6.3—Unbalanced backfill height size bar is used and the spacing shown in
the table is reduced by multiplying the
6.3.1 Unbalanced backfill height is the difference spacing by 0.67 or 0.83, respectively.
in height between the exterior finish ground level
and the lower of the top of the concrete footing that (3) Vertical reinforcement, when required,
supports the foundation wall or the interior finish shall be placed nearest to the inside face
ground level. Where an interior concrete slab on of the wall a distance, d, from the outside
grade is provided and is in contact with the interior face (soil face) of the wall. The distance,
surface of the foundation wall, the unbalanced d, is equal to the wall thickness, t, minus
backfill height shall be permitted to be measured
from the exterior finish ground level to the top of
the interior concrete slab.
  =   30   / 2
30 mm plus one-half the bar diameter,
, [ ]. The
reinforcement shall be placed within a
tolerance of ± 10 mm where d is less than
6.4—Rubble stone foundation walls or equal to 200 mm or ± 12 mm where d
6.5—Concrete foundation walls is greater than 200 mm.

6.5.1 Concrete and masonry foundation walls (4) In lieu of the reinforcement shown in
shall be designed in accordance with SBC 304, as Table 6-1 , smaller reinforcing bar sizes
applicable. with closer spacings that provide an
equivalent cross-sectional area of
Exception: Concrete and masonry foundation walls reinforcement per unit length shall be
shall be permitted to be designed and constructed in permitted.
accordance with Section 6.6 .
(5) Concrete cover for reinforcement
6.6—Prescripti ve design of concrete measured from the inside face of the wall
foundation walls shall not be less than 20 mm. Concrete
cover for reinforcement measured from
6.6.1 Concrete and masonry foundation walls
the outside face of the wall shall not be
that are laterally supported at the top and bottom
less than 40 mm for bars diameter 16 mm
shall be permitted to be designed and constructed
and smaller, and not less than 50 mm for
in accordance with this section.
larger bars.
6.6.2 Foundation wall thickness. The thickness
of prescriptively designed foundation walls shall not
be less than the thickness of the wall supported,
except that foundation walls of at least 200 mm
(6)

Concrete shall have a specified
compressive strength, , of not less than
20 MPa.
nominal width shall be permitted to support brick- (7) The unfactored axial load in kN per
veneered frame walls and 250 mm cavity walls linear meter of wall shall not exceed
provided the requirements of Section 6.6.3 is met.

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CHAPTER 6 FOUNDATION WALLS

0.1 × × , where t is the specified wall

thickness in mm.
with piers spaced 1800 mm on center
(O.C.).
6.6.3.1 Seismic requirements. Based on the (3) Piers shall be constructed in accordance
seismic design category assigned to the structure in with chapter 21 SBC 201 and the
accordance with Section 1613 of SBC 201, concrete following:
foundation walls designed using Table 6-1 shall be
(i) The unsupported height of the
subject to the following limitations:
masonry piers shall not exceed
(1) Seismic Design Categories A and B. Not 10 times their least dimension.
less than one bar diameter 16 mm shall (ii) Where structural clay tile or
be provided around window, door and hollow concrete masonry units
similar sized openings. The bar shall be are used for piers supporting
anchored to develop fy in tension at the beams and girders, the cellular
corners of openings. spaces shall be filled solidly
with concrete or Type M or S
(2) Seismic Design Categories C, D, E, and
mortar.
F. Tables shall not be used except as
allowed for plain concrete members in Exception: Unfilled hollow piers shall be permitted
Section 1905.1.7 SBC 201. where the unsupported height of the pier is not more
than four times its least dimension.
6.6.4 Masonry foundation walls.
(iii) Hollow piers shall be capped
Empty
with 100 mm of solid masonry
6.7—Pier and curt ain wall foundations or concrete or the cavities of the
top course shall be filled with
6.7.1 Except in Seismic Design Category D, E,
concrete or grout.
and F, pier and curtain wall foundations shall be
permitted to be used to support light- frame (4) The maximum height of a 100 mm load-
construction not more than two stories above grade bearing masonry foundation wall
plane, provided the following requirements are met: supporting wood frame walls and floors
shall not be more than 1220 mm in
(1) All load-bearing walls shall be placed on
height.
continuous concrete footings bonded
integrally with the exterior wall footings. (5) The unbalanced fill for 100 mm
foundation walls shall not exceed 600
(2) The minimum actual thickness of a load-
mm for solid masonry, nor 300 mm for
bearing masonry wall shall not be less
hollow masonry.
than 100 mm nominal or 90 mm actual
thickness, and shall be bonded integrally

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CHAPTER 6 FOUNDATION WALLS

TABL ES OF CHAPTER 6

Table 6-1—Concrete foundation wallsb, c

Minimum Vertical Reinforcement-Bar Size and Spacing (mm)

Maximum Maximum Design lateral soil load a (kPa/m per 300 mm of depth)
Wall Unbalanced
Height Backfill 4.7 d 7.1 d 9.5

(mm) Height Minimum wall thickness (mm)

(mm) 200 250 300 200 250 300 200 250 300

1200 PC PC PC PC PC PC PC PC PC
1500
1500 PC PC PC PC PC PC PC PC PC

1200 PC PC PC PC PC PC PC PC PC

1800 1500 PC PC PC PC PC PC PC PC PC

1800 PC PC PC PC PC PC PC PC PC

1200 PC PC PC PC PC PC PC PC PC

1500 PC PC PC PC PC PC PC PC PC
2100 Dia 16 at
1800 PC PC PC PC PC PC PC PC
1200
Dia 16 at Dia 20 at
2100 PC PC PC PC PC PC PC
1100 1200

1200 PC PC PC PC PC PC PC PC PC

1500 PC PC PC PC PC PC PC PC PC

Dia16 at
2400 1800 PC PC PC PC PC PC PC PC
1100
Dia16 at Dia 20 at
2100 PC PC PC PC PC PC PC
1000 1100
Dia16 at Dia 20 at Dia 20 at Dia 20 at
2400 PC PC PC PC pc
1200 1100 800 1100

1200 PC PC PC PC PC PC PC PC PC

1500 PC PC PC PC PC PC PC PC PC

Dia16 at
1800 PC PC PC PC PC PC PC PC
1000
2700 Dia16 at Dia 20 at Dia16 at
2100 PC PC PC PC PC PC
900 900 900
Dia16 at Dia 20 at Dia16 at Dia 22 at Dia 20 at Dia 14 at
2400 PC PC PC
1000 900 900 1000 1000 1200
Dia 20 at Dia 22 at Dia 20 at Dia 22 at Dia 22 at Dia 20 at
2700 d PC PC PC
1100 1000 1000 700 1000 1000

1200 PC PC PC PC PC PC PC PC PC

1500 PC PC PC PC PC PC PC PC PC

Dia 16 at
1800 PC PC PC PC PC PC PC PC
900
Dia 20 at Dia 20 at Dia 20 at
3000 2100 PC PC PC PC PC PC
1200 900 1200
Dia16 at Dia 22 at Dia 20 at Dia 22 at Dia 22 at Dia 20 at
2400 PC PC PC
900 1200 1200 800 1900 1100
Dia 20 at Dia 14 at Dia 22 at Dia 22 at Dia 14 at Dia 20 at Dia 22 at Dia 22 at
2700 d PC
1000 1200 900 1200 1200 500 900 1200
Dia 22 at Dia 20 at Dia 22 at Dia 22 at Dia 20 at Dia 20 at Dia 22 at Dia22 at
3000 d PC
1100 1100 700 1000 900 500 950 900

a. For design lateral soil loads, see Section 1610 SBC 201.
b. Provisions for this table are based on design and construction requirements specified in Section 6.6.3 .
c. "PC" means plain concrete.
d. Where unbalanced backfill height exceeds 2400 mm and design lateral soil loads from Table 1610.1 of SBC 201 are used, the requirements for 4.7
and 7.1 kPa/m per 300 mm of depth are not applicable (see Section 1610 of SBC 201).

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CHAPTER 7 RETAINING WALLS

CHAPTER 7—RETAINING WALLS

7.1—General or passive conditions set forth in Table 7-1 , the earth

pressure coefficient shall be adjusted in accordance
7.1.1 Retaining walls shall be designed in
with Figure 7-1 .
accordance with Sections 7.2 through 7.6 to ensure
stability against overturning, sliding, excessive 7.2.3.2 Translation. It shall be permitted to
foundation pressure and water uplift. consider uniform translation required to mobilize
ultimate passive resistance or active pressure
7.1.2 Scope. This Chapter shall apply to all
equivalent to movement of top of wall based on
matters pertaining to design and construction of
rotation given in Table 7-1 .
rigid gravity, semi gravity, cantilever, buttressed,
and counterfort retaining walls. For special types of 7.2.3.3 Restrained wall. Where wall is prevented
retaining walls, provisions of this code shall apply from even slight movement, the earth pressure shall
where applicable. General safety measures during be considered to remain at-rest conditions.
construction shall comply with provisions of 7.2.3.4 Basement and other below grade walls.
CHAPTER 3 .
Pressures on walls below grade shall be computed
7.2—Lateral earth pr essures based on restrained conditions that prevail, type of
backfill, and the amount of compaction. The
7.2.1 Computations of lateral earth pressures provisions of CHAPTER 6 shall apply where
shall comply with the provisions of Sections 7.2.2 applicable.
through 7.2.7. Wall movements set forth in Table
7-1 shall be considered the magnitude required for 7.2.3.5 Wall on rock. Where the wall is founded on
active and passive conditions to exist. Soil rock, sufficient rotation of the base and wall so that
permeability characteristics, boundary drainage and active pressure is developed, shall be accomplished
loading conditions, and time shall be considered in by placing 150 to 300 mm thick earth pad beneath
selection of strength parameters. In soils where the base and by constructing the stem with
partial drainage occurs during the time of sufficient flexibility to yield with the soil pressure.
construction, analysis shall be performed for short- 7.2.4 Groundwater conditions. Pressure
term and long-term conditions, and the wall shall be computations shall include uplift pressures and the
designed for the worse conditions. effect of the greatest unbalanced water head
7.2.2 Wall friction. Wall friction and vertical anticipated to act across the wall. For cohesionless
movement, slope of the wall in the backside and materials, increase in lateral force on wall due to
sloping backfill shall be considered in determining rainfall shall be considered and walls shall be
the lateral pressures applied against the wall. Unless designed to support the weight of the full
data to substantiate the use of other values are hydrostatic pressure of undrained backfill unless a
submitted and approved by a registered design drainage system is installed in accordance with
professional, the values set forth in Table 7-2 and Sections 13.4.3 and 13.4.4.
Table 7-3 shall be used in computations that include 7.2.5 Surcharge. Stability shall be checked with
effects of wall friction. and without surcharge. Lateral pressure on wall due
7.2.3 Wall movement. The effect of wall to point and line loads shall be computed based on
movement on the earth pressure coefficients shall the assumption of an unyielding rigid wall and the
conform to the provisions of Sections 7.2.3.1 and lateral pressures are set equal to double the values
7.2.3.2. obtained by elastic equations. The applicability of
the assumption of an unyielding rigid wall shall be
7.2.3.1 Rotation. If the wall is free at the top and evaluated for each specific wall. For uniform
there are no other structures associated with, wall surcharge loading it shall be permitted to compute
tilting shall not exceed 0.1 times the height of the lateral stress by treating the surcharge as if it were
wall. Where the actual estimated wall rotation is backfill and multiplying the vertical stress at any
less than the value required to fully mobilize active depth by the appropriate earth pressure coefficient.

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CHAPTER 7 RETAINING WALLS

It shall be permitted for design purposes to ∗= Slope of wall back with respect to vertical;
considerer a distributed surface load surcharge on
the order of 15 kPa to account for construction
 = Inclination of soil surface (upward slopes away
from the wall are positives);
materials and equipment placed within 5 to 10
meters from the wall. Where construction ∗∗  
= + )= Modified slope of wall back;
equipment is anticipated within 2 meters of the
  
= + )= Modified inclination of soil surface;
wall, it must be accounted for separately.
 = Unit weight of soil; and
7.2.6 Compaction. For backfill of granular soils
compacted in a confined wedge behind the wall, the
horizontal pressure beyond those represented by
 = Seismic inertia angle given as follows:

active or at-rest values shall be computed in

accordance with Figure 7-2 . Compaction-induced
pressures shall not be considered in bearing,
 = tan− 1  (7-2)

overturning and sliding analyses and need to be

considered for structural design only. Backfill shall = Horizontal ground acceleration in g’s; and
be brought up equally on both sides until the lower
side finished grade is reached and precautions shall
= Vertical ground acceleration in g’s.
be taken to prevent overcompaction which will 7.2.7.2 For modified slope angle  * and  *, the
cause excessive lateral forces to be applied to the
modified coefficient of earth pressures k A (  *,  *)
wall.
shall be calculated from the Coulomb theory.
7.2.6.1 Clays and other fine-grained soils, as well as Dynamic pressure increment shall be obtained by
granular soils, with amount of clay and silt greater
than 15 percent shall not be used as a backfill
behind retaining wall. Where they must be used, the
from Coulomb theory for given  
subtracting static active force (to be determined
and ) from
combined active force given by Equation (7-1).
lateral earth pressure shall be calculated based on Location of resultant shall be obtained by
at-rest conditions, with due consideration to considering the earth pressure to be composed of a
potential poor drainage conditions and swelling. static and dynamic component with the static
Where loose hydraulic fill is used it shall be placed component acts at the lowest third point, whereas
by procedures which permit runoff of wash water the dynamic component acts above the base at 0.6
and prevent building up of large hydrostatic times the height of the wall. Under the combined
pressures. effect of static and earthquake load the factor of
7.2.7 Earthquake loading. For retaining walls safety shall not be less than 1.2.
assigned to Seismic Design Category C, D, E, or F 7.2.7.3 Where soil is below groundwater table, the
provisions of SBC 301 and SBC 304 shall apply hydrodynamic pressure computed from the
when not in conflict with the provisions of following formula shall be added
CHAPTER 7 .

7.2.7.1 The combined resultant active force due to

initial static pressure and increase in pressure from
ground motion shall be computed from the
 = 32 ℎ/ (7-3)

following formula:
where:

 = 12 ∗,∗× = Hydrodynamic pressure at depth z below

groundwater table;

cos ∗ 
1 cos (7-1) ℎ = Height of water;
 = Depth below the groundwater table; and

where:
= Unit weight of water (9.81 kN/m3).
7.3—Bearing capacity
 = Combined resultant active force;
 = Coefficient of active earth pressure;
7.3.1 The allowable soil pressure shall be
determined in accordance with the provisions of
 = Wall height;
CHAPTER 4 . The determination of the allowable

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CHAPTER 7 RETAINING WALLS

bearing pressure shall be made according to the compressible, settlement shall be computed based
bearing capacity of a foundation subjected to on any method approved by the building official.
eccentric loads. The bearing capacity shall be Tilt of rigid wall shall be obtained from the
checked for the same loading conditions as estimated settlement. Differential settlement shall
determined by the overturning analysis for each be limited to the amount of tilting that shall not
case analyzed. Where the wall is founded on sloped exceed 5 percent of wall height. If the consequent
ground, methods for determination of ultimate tilt exceeds acceptable limits, the wall shall be
bearing capacity that deal with this situation shall proportioned to keep the resultant force at the
be used. The factor of safety with respect to bearing middle third of base. The retaining wall shall be
capacity shall not be less than 3. For walls founded proportioned so that the factor of safety against
on rocks, high toe pressure that may cause breaking overturning is not less than 1.5. The value of
the toe from the remainder of the base shall be angular distortion (settlement/length of structure) of
avoided by proportioning the footing so that the retaining walls shall not exceed 0.002 radians.
resultant falls near its centroid.
Exception: Where earthquake loads are included,
7.4—Stability the minimum safety factor for retaining wall
overturning shall be 1.1.
7.4.1 Retaining walls shall be designed to ensure
stability against overturning, sliding, and stability 7.4.4 Deep-seated sliding. Where retaining
of supporting ground. Stability analyses shall walls are underlain by weak soils, the overall
conform to the provisions of Sections 7.4.2 through stability of the soil mass containing the retaining
7.4.5. wall shall be checked with respect to the most
critical surface of sliding. The stability analysis
7.4.2 Sliding stability. The base shall be at least
shall be made for after construction and for long-
1000 mm below ground surface in front of the wall.
term conditions. The factor of safety for the overall
Sliding stability shall be adequate without including
stability of the soil mass containing the wall shall
passive pressure at the toe. Where insufficient
not be less than 2.
sliding resistance is available, one provision shall
be taken including, but not limited to, increasing the 7.4.5 Wall with key. Prior to performing an
width of the wall base, founding the wall on piles or overturning analysis, the depth of the key and width
lowering the base of the wall. If the wall is of the base shall be determined from the sliding
supported by rock or very stiff clay, it shall be stability analysis. For a wall with a horizontal base
permitted to install a key below the foundation to and a key, it shall be permitted to assume the
provide additional resistance to sliding. The key shearing resistance of the base to be zero and the
shall conform to the provisions of Section 7.4.5 . horizontal resisting force acting on the key is that
Where a keyway is extended below the wall base required for equilibrium. For a wall with a sloping
with the intent to engage passive pressure and base and a key, the horizontal force required for
enhance sliding stability, lateral soil pressures on equilibrium shall be assumed to act on the base and
both sides of the keyway shall be considered in the the key. In both cases the resisting soil force down
sliding analysis. The safety factor against lateral to the bottom of the toe shall be computed using at-
sliding shall be taken as the available soil resistance rest earth pressure if the material on the resisting
at the base of the retaining wall foundation divided side will not lose its resistance characteristics with
by the net lateral force applied to the retaining wall. any probable change in water content or
The factor of safety against sliding shall not be less environmental conditions and will not be eroded or
than 1.5 for cohesionless backfill and 2.0 for excavated during the life of the wall.
cohesive backfill.
7.5—Wall dimensions
Exception: Where earthquake loads are included,
7.5.1 Thickness of the upper part of the wall shall
the minimum safety factor for retaining wall sliding
not be less than 300 mm, whereas thickness of the
shall be 1.1.
lower part of the wall shall be enough to resist shear
7.4.3 Overturning stability. For walls on without reinforcement. Depth of wall foundation
relatively incompressible foundations, overturning shall be located below line of seasonal changes and
check is ignored if the resultant is within the middle shall be deep enough to provide adequate bearing
third of the base for walls founded on soils and if capacity and soil sliding resistance. The wall
the resultant is within the middle half for walls foundation shall be proportioned such that the wall
founded on rocks. Where foundation soil is does not slide or overturn, the allowable bearing

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CHAPTER 7 RETAINING WALLS

capacity of the soil is not exceeded, and that total considered they shall be designed by a registered
and differential settlements are tolerable. The base design professional and subject to the approval of
and other dimensions shall be such that the resultant the building official. As a minimum, there shall be
falls within the middle third of the base. Where weep holes with pockets of coarse-grained material
additional front clearance is needed, it shall be at the back of the wall, and a gutter shall be
permitted to construct counterfort retaining walls provided for collecting runoff. All retaining walls
without a toe provided that the sliding and shall have adequate surface drainage to dispose of
overturning stability requirements stated in surface water. A layer of impervious soil shall be
Sections 7.4.2 and 7.4.3 are met. placed on top of the soil backfill to reduce surface
infiltration of rainfall. It shall be permitted to use
7.6—Wall construction inclined and horizontal drains in conjunction with
7.6.1 Concrete shall not be placed through water back drain.
unless a tremie or other method approved by the
7.6.4.1 The weep holes shall be of sufficient size
building official is used. Where placed under or in
and be carefully surrounded with a granular filter or
the presence of water, the concrete shall be
by the use of filter fabric on the backfill side and
deposited by approved means to ensure minimum
directly surrounding the entrance to the weep holes.
segregation of the mix and negligible turbulence of
The weep holes shall be spaced not more than 3 m
the water and that will provide the depositing or
apart vertically and horizontally. Where
construction of sound concrete in the dry condition.
longitudinal drains along the back face are used, a
7.6.2 Minimum concrete cover to layer of free-draining granular material shall be
reinforcement. When the concrete of retaining placed along the back of the wall and surrounding
walls is poured directly on the ground or against the drain pipes opening. The gradation of the filter
excavation walls the minimum concrete cover to shall satisfy the following piping or stability
reinforcement shall not be less than 75 mm and not criterion.
less than 40 mm when concrete is poured against
lean concrete or vertical forms. This cover shall also
satisfy other requirements with regard to concrete
15 ≤ 5 (7-4)
exposure conditions presented in SBC 304. 85
7.6.3 Joints. Construction and expansion joints
where:
shall be provided where needed. Construction joints
shall be constructed into a retaining wall between
successive pours of concrete both horizontally and

and
= size of filter material at 15 percent passing;

vertically. Horizontal construction joints shall be

kept to a minimum and the top surface of each lift
 = size of protected soil at 85 percent passing.
shall be cleaned and roughened before placing the and
next lift. Long walls shall have expansion joints at
intervals of 10,000 mm. Where vertical-expansion
joints are considered, they shall be placed along the
50 ≤ 25 (7-5)
wall at spacing of 20,000 to 30,000 mm. 50
Reinforcing steel and other fixed metal embedded
or bonded to the surface of the concrete shall not where:
extend through the expansion joint. For cantilever
concrete walls, it shall be permitted to locate the

and
= size of filter material at 50 percent passing;
vertical expansion joints only on the stem, and the
footing is a continuous placement.
7.6.3.1 The thickness of joint filler necessary to
 = size of protected soil at 50 percent passing.
The filter material shall be more permeable than the
provide stress relief shall be determined from the material being drained and the following condition
estimated initial contraction and subsequent shall be met.
expansion from maximum temperature variation.
7.6.4 Drainage. Regardless of the drainage
system used, the wall must have an adequate factor
of safety assuming the drainage system is
4 < 1515 < 20 (7-6)

inoperative. Where drainage measures are

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CHAPTER 7 RETAINING WALLS

where: dust, etc. shall be replaced and filter materials

 = size of filter protected soil at 15 percent
passing.
subject to cementation shall be rejected.
7.6.4.3 In lieu of a granular filter, it shall be
permitted to use prefabricated geocomposite drains
7.6.4.2 Where a blanket of well-graded sand and
with adequate filter flow capacity and acceptable
gravel that is placed along the back of the wall it
shall satisfy the requirements of Equation (7-4)
through Equation (7-6). Where longitudinal drains
passing, 
retention. The size of filter material at 50 percent
, shall not be less than the diameter of
the hole for circular openings and shall be 1.2 times
are used within drainage blanket, they shall be large
slot width for slotted openings. The drainage
enough to carry the discharge and have adequate
composite manufacture’s recommendations for
slope to provide sufficient velocity to remove
backfilling and compaction near the composite shall
sediment from the drain. Segregation of sand and
be followed.
gravel during construction shall be avoided. Filter
or drain materials contaminated by muddy water,

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CHAPTER 7 RETAINING WALLS

TABLES AND FIGURES OF CHAPTER 7

Table 7-1—Magnitude of rotation to reach failure

SOIL TYPE AND CONDITION

ROTATION 
ACTIVE PASSIVE
Dense cohesionless soil 0.0005 0.002
Loose cohesionless soil 0.002 0.006
Stiff cohesive soil 0.01 0.02
Soft cohesive soil 0.02 0.04

a.
= Horizontal translation at the top of the wall;  = Height of the wall

Table 7-2—Ultimate friction factors for dissimilar materials

INTERFACE MATERIALS
Clean sound rock
FRICTION FACTOR,
0.7

Clean gravel, gravel-sand mixtures, coarse sand 0.55 – 0.60
Clean fine to medium sand, silty medium to coarse sand, silty 0.45 – 0.55
or clayey gravel
Clean fine sand, silty or clayey fine to medium sand 0.35 – 0.45
Fine sandy silt, nonplastic silt 0.30 – 0.35
Very stiff and hard residual or preconsolidated clay 0.40 – 0.50
Medium stiff and stiff clay and silty clay 0.30 – 0.35
a

Values for shall not exceed one-half the angle of internal friction of the backfill soils for steel and precast concrete
and two-third the angle of internal friction of the backfill soils for cast-in place concrete.

Table 7-3—Ultimate adhesion for dissimilar materials

COHESION ADHESION
INTERFACE MATERIALS
(kPa) (kPa)
Very soft cohesive soil 0 – 10 0 – 10
Soft cohesive soil 10 – 25 10 – 25
Medium stiff cohesive soil 25 – 50 25 – 35
Stiff cohesive soil 50 – 100 35 – 45
Very stiff cohesive soil 100 – 200 45 – 60

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CHAPTER 7 RETAINING WALLS

Figure 7-1—Effect of wall movement on wall pressures (nafac, 1986).

Figure 7-2—Horizontal pressure on walls from compaction effort (Nafac, 1986).

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

CHAPTER 8—COMBINED FOOTINGS AND MATS

8.1—General foundations, footings and overlying fill. Reduced

live loads, as specified in Section 4.8 SBC 301, are
8.1.1 Analysis and design of combined footings
permitted to be used in designing footings. Strength
and mats shall conform to all requirements of ACI
design of reinforced concrete systems and elements
336.2R Suggested Analysis and Design Procedures
shall comply with load combinations specified in
for Combined Footings and Mats except as
SBC 304.
modified by CHAPTER 8 . All provisions of SBC
303 not specifically excluded, and not in conflict 8.3—Concrete
with the provisions of CHAPTER 8 shall apply to
8.3.1 Material, construction, and placement of
combined footings and mats, where applicable.
concrete shall be in accordance with the provisions
Design of combined or mat foundations shall be
of Section 5.4.2 . For mats construction joints shall
based on the Strength Design Method of SBC 304.
be carefully located at sections of low shear stress
8.1.2 Combined footings and mats shall be or at the center lines between columns. An elapse of
designed and constructed on the basis of a site at least 24 hours shall be left between pours of
investigation as defined in CHAPTER 2 , unless the adjacent areas. If bar splicing is needed, sufficient
building official ascertains that sufficient data upon overlapping shall be provided. The concrete shall be
which to base the design and installation is strong enough to transfer the shear stress across the
available. The investigation and report provisions joint. If necessary, the mat may be thickened to
of CHAPTER 2 shall be expanded to include, but provide sufficient strength in the joints.
need not be limited to, the following:
8.4—Contact pressure
(1) Values for modulus of subgrade reaction.
8.4.1 Soil contact pressure acting on a combined
(2) Recommended shapes of combined footing or mat and the internal stresses produced by
footings. them shall be determined from one of the load
8.1.3 Approval of special systems of design or combinations given in Section 2.4 SBC 301,
construction. Sponsors of any system of design or whichever produces the maximum value for the
construction within the scope of CHAPTER 8 , the element under investigation.
adequacy of which has been shown by successful 8.4.2 The combinations of unfactored loads
use or by analysis or test, but which does not which will produce the greatest contact pressure on
conform to or is not covered by CHAPTER 8 , shall a base area of given shape and size shall be selected.
have the right to present that data on which their The allowable soil pressure shall be determined in
design is based to the building official or to a board accordance with the provisions of CHAPTER 4 .
of examiners appointed by the building official. Loads shall include the vertical effects of moments
This board shall be composed of competent caused by horizontal components of these forces
geotechnical and structural engineers and shall have and by eccentrically applied vertical loads.
authority to investigate the data so submitted, to Buoyancy of submerged parts where this reduces
require tests, and to formulate rules governing the factor of safety or increases the contact
design and construction of such systems to meet the pressures, as in flood conditions shall be
intent of CHAPTER 8 . These rules when approved considered.
by the building official and promulgated shall be of
8.4.3 The maximum unfactored design contact
the same force as the provisions of CHAPTER 8 .
pressures shall not exceed the allowable soil
8.2—Loadings pressure as obtained from CHAPTER 4 or cause
settlements that exceed the values set forth in Table
8.2.1 Combined footings and mats shall be
5-1 and Table 8-3 . Where wind or earthquake forces
designed for the most unfavorable effects due to the
form a part of the load combination, the allowable
combinations of loads specified in SBC 301 Section
soil pressure may be increased as allowed by the
2.4. The dead load shall include the weight of
SBC or approved by the building official.

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

8.4.4 In determination of the contact pressures minimum soil pressures may then be calculated
and associated subgrade response, the validity of from the following formula, which applies only to
simplifying assumptions and the accuracy of any the rectangular base areas and only when
resulting computations shall be approved by the eccentricity is located along one of the principal
building official and evaluated on the basis of the axes of the footing.
following variables:
(1) The increased unit pressures developed
along the edges of rigid footings on
, = ∑ 1 ± 6 (8-1)
cohesive soils and at the center for rigid
footings on cohesionless soils. where:
(2) The effect of embedment of the footing  = Maximum soil contact pressure;
on pressure variation.
 = Minimum soil contact pressure;
(3) Consideration in the analysis of the
behavior of the foundations immediately  = Any force acting perpendicular to base area;
after the construction as well as the
effects of long-term consolidation of
 = Foundation width or width of beam column
element;

(4)
compressible layers.
Consideration of size of the footing in

with centroid of footing area (  ≤ /6
= Eccentricity of resultant of all vertical forces
); and
determination of the modulus of
subgrade reaction of soil.  = Foundation base length or length of beam
column element.
(5) The variation of contact pressures from
eccentric loading conditions. For footings with eccentricity about both axes (two-
way eccentricity), soil pressure is obtained from:
(6) Consideration of the influence of the
stiffness of the footing and the
superstructure on deformations that can
occur at the contact surface and the
 = ∑ 1± 6 ± 6 (8-2)

corresponding variation on contact

pressure and redistribution of reactions where:
occurring within the superstructure
frame.  = Soil contact pressure;

8.4.5 Distribution of soil reactions. Contact

pressures at the base of combined footings and mats
 = Eccentricity of resultant of all vertical forces
with respect to the x-axis;
shall be determined in accordance with Sections
8.4.5.1 through 8.4.5.3.
 = Eccentricity of resultant of all vertical forces
with respect to the y-axis; and
8.4.5.1 General. Except for unusual conditions, the
contact pressures at the base of a combined footings
 = Any force acting perpendicular to base area.

and mats may be assumed to follow either a 8.4.5.2.2 Contact pressure over part of area. The
distribution governed by elastic subgrade reaction soil pressure distribution shall be assumed
or a straight-line distribution. At no place shall the triangular and the resultant has the same magnitude
calculated contact pressure exceed the allowable and colinear, but acts in the opposite direction of the
bearing capacity as determined from CHAPTER 4 . resultant of the applied forces.

8.4.5.2 Straight-line distribution of contact 8.4.5.2.2.1 The maximum soil pressure at the
pressure. It shall be permitted to assume a linear footing edge under this condition shall be calculated
distribution for soil contact pressure if continuous from the following expression:

 = 23 2 

footings meet the requirement of Section 8.7.2 and
mats conform to the requirements of Section
8.9.3.3. (8-3)

8.4.5.2.1 Contact pressure over total base area. If

the resultant force is such that the entire contact area The minimum soil pressure at distance L 1 is set
of foundation is in compression, the maximum and equal to zero, where L1 is the footing effective

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

length measured from the pressed edge to the plate load tests and shall be obtained using subgrade
position at which the contact pressure is zero and is reaction theory, but shall be modified to
given by: individually consider dead load, live load, size
effects, and the associated subgrade response.

 = 32  (8-4)

Zones of different constant subgrade moduli shall
be considered to provide a more accurate estimate
of the subgrade response as compared to that
predicted by a single modulus of subgrade reaction.
Equation (8-3) and Equation (8-4) are applied based
on the assumption that no tensile stresses exist 8.4.5.3.2.2.1 The value for the modulus of subgrade
between footing and soil and for cases where the reaction for use in elastic foundation analysis may
resultant force falls out of the middle third of the be estimated from a plate load test carried out in
base. accordance with ASTM D1194. Since plate load
tests are conducted on small plates, great care must
8.4.5.3 Distribution of contact pressure be exercised to ensure that results are properly
governed by the modulus of subgrade reaction. extrapolated. The modulus of subgrade reaction
It shall be permitted to get the distribution of contact from plate load test shall be converted to that of mat
pressure based on modulus of subgrade reaction using the following formula:
obtained from Section 8.4.5.3.2. The thickness shall
be sized for shear without using reinforcement. The
flexural steel is then obtained by assuming a linear
soil pressure distribution and using simplified
 =    (8-5)

procedures in which the foundation satisfies static

equilibrium. The flexural steel may also be obtained where:
by assuming that the foundation is an elastic
member interacting with an elastic soil. = Coefficient (or modulus) of vertical subgrade
reaction; generic term dependent on dimensions of
8.4.5.3.1 Beams on elastic foundations. If the loaded area;
combined footing is assumed to be a flexible slab,
it may be analyzed as a beam on elastic foundation.
It shall be permitted to analyze a beam on elastic
 = Coefficient of subgrade reaction from a plate
load test;
foundation using the discrete element method, the  = Mat width;
finite element method, or any other method as
approved by the building official.  = Plate width; and
8.4.5.3.2 Estimating the modulus of subgrade
reaction. The value for modulus of subgrade
 = Factor that ranges from 0.5 to 0.7.
8.4.5.3.2.2.2 Allowance shall be made for the depth
reaction may be obtained from one of the methods
of compressible strata beneath the mat and if it is
in Sections 8.4.5.3.2.1 through 8.4.5.3.2.4. It shall be
less than about four times the width of footing,
permitted to use a constant value for the modulus of
lower values of “n” shall be used.
subgrade reaction except where the rigidity of the
footing and superstructure is considered small, the 8.4.5.3.2.3 Modulus of subgrade reaction from


decrease in the value of modulus of subgrade
reaction, , with increasing applied load shall be
taken into consideration.
elastic parameters. It shall be permitted to estimate
the value for the modulus of subgrade reaction
based on laboratory or in situ tests to determine the
elastic parameters of the foundation material. This
8.4.5.3.2.1 Presumptive modulus of subgrade
shall be done by numerically integrating the strain
reaction values. It shall be permitted to use values
for the modulus of subgrade reaction for supporting
soils as set forth in Table 8-1 and Table 8-2 to
∆ and back computing 
over the depth of influence to obtain a settlement
as:
determine about the correct order of magnitude of
the subgrade modulus obtained from Sections
8.4.5.3.2.1 through 8.4.5.3.2.5. These values shall be
 = ∆ (8-6)

used only as a representative guide.

where:
8.4.5.3.2.2 Modulus of subgrade reaction from
plate load test. For mat foundations, this soil
property shall not be estimated on the basis of field
 = Applied pressure; and

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

∆ = Settlement. settlement due to consolidation, and differential

settlement of the foundation.
8.4.5.3.2.3.1 Several values of strain shall be used
in the influence depth of approximately four times 8.5.3 Total settlements. Total settlement of
the largest dimension of the base. combined footings and mats shall not exceed the
value set forth in Table 5-1 .
8.4.5.3.2.3.2 It shall be permitted to estimate the
modulus of subgrade reaction based on laboratory 8.5.4 Differential settlement. Differential
measured modulus of elasticity such that settlements for combined footings shall not exceed
the values set forth in Table 5-2 . For mats the
 
 = 1 differential settlement shall be taken as three-fourth
(8-7)

of the total settlement if it is not more than 50 mm
or determined based on relative stiffness, , as
shown in Table 8-3 .
where:
8.6—Combined footing s
 = Poisons ratio for soil; and
 = Modulus of elasticity for soil.
8.6.1 Combined footings shall be designed and
constructed in accordance with Sections 8.6.2
through 8.6.4 .
8.4.5.3.2.4 Modulus of subgrade reaction from
load bearing. In the absence of a more rigorous 8.6.2 Rectangular-shaped footings. The length
data, it shall be permitted to consider a value for the and width of rectangular-shaped footings shall be

allowable load bearing. The value for 

modulus of subgrade reaction equal to 120 times the
shall be
verified from in situ tests in case of sensitive and
established such that the maximum contact pressure
at no place exceeds the allowable soil pressure as
obtained from CHAPTER 4. All moments shall be
important structures. calculated about the centeroid of the footing area
8.4.5.3.2.5 Time-dependent subgrade response. and the bottom of the footing. All footing
Consideration shall be given to the time-dependent dimension shall be computed on the assumption
subgrade response to the loading conditions. An that the footing acts as a rigid body.
iterative procedure may be necessary to compare 8.6.2.1 When the resultant of the column loads,
the mat deflections with computed soil response. including consideration of the moments from lateral
Since the soil response profile is based on contact forces, coincides with centroid of the footing base,
stresses which are in turn based on mat loads, it shall be permitted to assume that the contact
flexibility, and modulus of subgrade reaction, pressure is uniform over the entire area of the
iterations shall be made until the computed mat footing. The resultant of the load of the two
deflection and soil response converge are within columns shall not fall outside the middle third of the
acceptable tolerance. footing. In case where this provision cannot be
fulfilled the contact pressure may be assumed to
8.5—Settlement
follow a linear distribution such that it varies from
8.5.1 Settlements of combined footings and mats a maximum at the pressed edge to a minimum either
shall conform to the provisions of Sections 8.5.2 beneath the footing or at the opposite edge to zero
through 8.5.4. at a distance that is equal three times the distance
8.5.2 General. The combinations of unfactored between the point of action of the resultant of loads
loads which will produce the greatest settlement or and the pressed edge.
deformation of the foundation, occurring either 8.6.2.2 Consideration shall be given to horizontal
during and immediately after the construction or at forces that can generate vertical components to the
a later stage, shall be selected. Loadings at various foundation due, but need not be limited to, wind,
stages of construction such as dead load or related earth pressure, and unbalanced hydrostatic
internal moments and forces, stage dead load pressure. A careful examination of the free body
consisting of the unfactored dead load of the must be made with the geotechnical engineer to
structure and foundation at a particular time or stage fully define the force systems acting on the
of construction, and stage service live load foundation before the structural analyses are
consisting of the sum of all unfactored live loads at attempted.
a particular stage of construction, shall be evaluated
8.6.3 Trapezoidal or irregularly shaped
to determine the initial settlement, long-term
footings. For reducing eccentric loading conditions,

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

it shall be permitted to design a trapezoidal or  = Overturning moment; and

irregularly shaped footing with the footing
considered to act as a rigid body and the contact
 = Least resultant of all forces acting
perpendicular to base area under any condition of
pressure determined in accordance with Section 8.4 .
loading simultaneous with the overturning moment.
8.6.4 Strap footings. The strap shall be rigid
8.6.5.2 Both cases of rectangular and triangular
enough to avoid rotation of the exterior footing and
distribution of the soil pressure along the pressed
the footings shall be proportioned for
edge of the footing shall be considered and the value
approximately equal soil pressure. A large
for FS shall not be less than 1.5.
difference in footing width shall be avoided to
reduce differential settlement. It shall be permitted 8.7—Continuous footings
to consider the strap to be rigid if it has a moment
8.7.1 Continuous footings shall be designed and
of inertia that is not less than four times that of the
constructed in accordance with Sections 8.7.2
attached footing. The width of the strap shall be
through 8.7.3 .
equal to the smallest column width.
8.7.2 Design for rigid structures. Continuous
8.6.4.1 Shear reinforcement in the strap shall not be
strip footings supporting structures which, because
used to increase rigidity. If the depth of footing is
of their stiffness, will not allow the individual
restricted, the depth of the strap may be increased to
columns to settle differentially may be designed
obtain the necessary rigidity. The strap shall be out
using the rigid body assumption with a linear
of contact with soil. The strap shall be securely
distribution of soil pressure as determined based on
fixed to the column and footing by dowels so that
principles of statics.
the system acts as a unit. The footings shall be
proportioned so that the least lateral dimensions are 8.7.2.1 Rigidity check based on relative stiffness.
within 300 to 600 mm of each other and the soil If the analysis of the relative stiffness of the footing
pressures are approximately equal. yields a value greater than 0.5, the footing can be
considered rigid and the variation of soil pressure
8.6.5 Overturning calculations. In analyzing
shall be determined on the basis of simple statics. If
overturning of the footing, the combination of
the relative stiffness factor is found to be equal or
unfactored loading that produces the greatest ratio
less than 0.5, the footing shall be designed as a
of overturning moment to the corresponding
flexible member using the foundation modulus
vertical load shall be used. Where the eccentricity
approach as described under Section 8.7.3 . The
is inside the footing edge, the factor of safety
relative stiffness shall be determined as:
against overturning shall be taken as the ratio of

 = 
resisting moment to the maximum overturning
moment. The maximum overturning moment and
(8-9)
the resisting moment caused by the minimum dead
weight of the structure; both shall be calculated
about the pressed edge of the footing. The factor of
where:
safety shall not be less than 1.5.
 = Relative stiffness;
8.6.5.1 If overturning is considered to occur by
yielding of the subsoil inside and along the pressed
edge of the footing, the factor of safety against
 = Modulus of elasticity of the material used in the
superstructure;
overturning shall be calculated from:
 = Modulus of elasticity of soil;

 =   (8-8)

 = Base width of foundation perpendicular to
direction of interest; and
 = Moment of inertia per unit width of the
superstructure.
where:
 = Factor of safety;
An approximate value for the flexural rigidity of

 = Distance from resultant of vertical forces to

overturning edge;
structure and footing, EIB, for unit width of the
structure can be obtained by adding the flexural
rigidity for footing, EfIf, flexural rigidity for each
υ = Distance from the pressed edge to ; member in the superstructure, EIb, and flexural
rigidity for shear walls, Eah3/12 as follows:

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

 =    ℎ12 

supported by subgrade reactions, if the footing
meets the following basic requirements:
(8-10)
(1) The minimum number of bays is three.
(2) The variation in adjacent column loads is
where;
ℎ = Wall height;
not greater than 20 percent.

 = Wall thickness;
(3) The variation in adjacent spans is not
greater than 20 percent.
 = Modulus of elasticity for footing; (4) The average length of adjacent spans is
 
= Moment of inertia for any member making up
the frame resistance perpendicular to ; and
between the limits of 1.75/λ and 3.50/λ.
If these limitations are met, the contact pressures
= Moment of inertia per unit width of the
foundation.
can be assumed to vary linearly, with the maximum
value under the columns and a minimum value at
the center of each bay.
8.7.2.2 Rigidity check based on column spacing. 8.8—Grid foundations
If the average of two adjacent spans in a continuous
strip having adjacent loads and column spacings 8.8.1 Grid foundations shall be designed and
that vary by not more than 20 percent of the greater constructed in accordance with provisions of
value, and is less than 1.75/λ, the footing can be Sections 8.7 . Grid foundations shall be analyzed as
considered rigid and the variation of soil pressure independent strips using column loads proportioned
shall be determined on the basis of simple statics. in direct ratio to the stiffness of the strips acting in
The characteristic coefficient λ is given by: each direction.
8.9—Mat foundations

 = 4 (8-11)
8.9.1 General. Mats shall be designed and
constructed in accordance with Sections 8.9.1
through 8.9.3 . Mats may be designed and analyzed
as either rigid bodies or as flexible plates supported
where: by an elastic foundation (the soil). In the analysis
 = Width of continuous footing or a strip of mat
between centers of adjacent bays;
and design of mats, a number of factors shall be
considered that include, but need not be limited to,

 = Modulus of elasticity of concrete;

the following:

 = Moment of inertia of the strip; and

(1) Reliability of proposed value for the
modulus of subgrade reaction obtained in
 = Modulus of subgrade reaction of soil.
(2)
accordance with Section 8.4.5.3.2.
Finite soil-strata thickness and variations
(as limited above) is greater than 1.75/
8.7.2.2.1 If the average length of two adjacent spans
, the beam-
on-elastic foundation method noted in Section 8.7.3
in soil properties both horizontally and
vertically.
shall be used. For general cases falling outside these (3) Shape of the mat.
limitations, the critical spacing at which the
(4) Variety of superstructure loads and
subgrade modulus theory becomes effective shall
probability of their occurrence.
be determined individually.
(5) Effect of superstructure stiffness on mat
8.7.3 Design for flexible footings. A flexible
and vice versa.
continuous footing (either isolated or taken from a
mat) shall be analyzed as a beam-on-elastic 8.9.1.1 The design and construction of mats shall be
foundation. Thickness shall be established on the under the direct supervision of a registered design
basis of allowable wide beam or punching shear professional having sufficient knowledge and
without use of shear reinforcement. The evaluation experience in foundation slab engineering, who
of moments and shears can be simplified from the shall certify to the building official that the mats as
procedure involved in the classical theory of a beam constructed satisfy the design criteria.

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8.9.2 Excavation heaves. The influence of heave for columns. The reinforcing steel for bending is
on subgrade response shall be determined by a designed by treating the mat as a rigid body and
geotechnical engineer. Recovery of the heave considering strips both ways, if the following
remaining after placing the mat shall be treated as criteria are met:
either a recompression or as an elastic problem. If
(1) Column spacing is less than 1.75/λ or the
the problem is analyzed as a recompression
mat is very thick.
problem, the subsurface response related to
recompression shall be obtained by a geotechnical (2) Relative stiffness kr as noted in Equation
engineer. The subsurface response may be in the (8-9) is greater than 0.5.
form of a recompression index or deflections
(3) Variation in column loads and spacing is
computed by the geotechnical engineer based on
not over 20 percent.
elastic and consolidation subsurface behavior.
These strips are analyzed as combined footings with
8.9.3 Design. A mat may be designed using the
multiple columns loaded with the soil pressure on
Strength Design Method of SBC 304. Analyses and
the strip, and column reactions equal to the factored
designs using computer programs shall be permitted
(or unfactored) loads obtained from the
provided design assumptions, user input, and
superstructure analysis.
computer-generated output are submitted. The mat
plan shall be proportioned using unfactored loads 8.9.3.3.1 Consideration shall be given to the shear
and any overturning moments. The pressure transfer between strips to satisfy a vertical load
diagram is considered linear and computed from summation.
Equation (8-2) and shall be less than allowable load 8.9.3.4 Flexible design. For mats not meeting the
bearing capacity of soil. Loads shall include the criteria of Section 8.9.3.3 , it shall be designed as a
effect of any column moments and any overturning flexible plate in accordance with Sections 8.9.3.4.1
moment due to wind or other effects. Any moments and 8.9.3.4.2 .
applied to the mat from columns or overturning,
etc., shall be included when computing the 8.9.3.4.1 Uniform loads and spacings. If variation
eccentricity. in adjacent column loads and in adjacent spans is
not greater than 20 percent it shall be permitted to
8.9.3.1 The contact pressure shall not exceed the analyze mats as continuous footings that can be
allowable load bearing capacity of soil determined analyzed according to the provisions of Section
from CHAPTER 4 . The allowable soil pressure may 8.7.3 . The mat shall be divided into strips the width
be furnished as one or more values depending on of each is equal to the distance between adjacent
long-term loading or including transient loads such bays. Each strip shall be analyzed independently
as wind. The soil pressure furnished by the considering column loads in both directions. The
geotechnical engineer shall be factored to a pseudo contact pressure is equal to the average contact
“ultimate” value by multiplying the allowable pressure evaluated for each strip in each direction.
pressure with the ratio of the sum of factored design
loads to the sum of the unfactored design loads. 8.9.3.4.2 Nonuniform loads and spacings. If
columns have irregular spacings or loads, mats may
8.9.3.2 Mat thickness. The minimum mat be analyzed based on theory of modulus subgrade
thickness based on punching shear at critical reaction, elastic, plate method, finite difference
columns shall be computed based on column load method, finite grid method, finite element method,
and shear perimeter. The depth of the mat shall be or any other method approved by the building
computed without using shear reinforcement and official.
determined on the basis of diagonal-tension shear as
noted in SBC 304 Chapter 15. Investigation of a 8.9.4 Circular mats or plates. For tall structure,
two-sided (corner column) or three-sided diagonal differential settlements shall be carefully controlled
tension shear perimeter shall be made for columns to avoid toppling when the line of action of gravity
adjacent to mat edge. An investigation for wide- forces falls out of the base. The plate depth shall be
beam or diagonal tension shall be made for designed for wide-beam or diagonal-tension shear
perimeter load-bearing walls. as appropriate.

8.9.3.3 Rigid design. It shall be permitted to design 8.9.5 Ring foundations. For ring foundations
mats as rigid body with linear distribution for used for water-tower structures, transmission
contact pressure if the mat, superstructure, or both towers, television antennas, and various other
are rigid enough not to allow differential settlement possible superstructures, analysis and design shall

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

be carried out using advanced method of analysis shall apply when not in conflict with the provisions
and carried out by a registered design profession of CHAPTER 5 . Strips between adjacent columns
knowledgeable in geotechnical and structural shall be capable of carrying, in tension or
engineering. compression, a force equal to the product of the
larger column load times the seismic coefficient SDS
8.10— Seismic requirements divided by 10 unless it is demonstrated that
8.10.1 For combined footings and mats of equivalent restraint is provided by the strips.
structures assigned to Seismic Design Category C,
D, E, or F, provisions of SBC 301 and SBC 304

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CHAPTER 8 COMBINED FOOTINGS AND M ATS

TABL ES OF CHAPTER 8

Table 8-1—Presumptive modulus of subgrade reaction values for

cohesionless soils
MODULUS OF SUBGRADE REACTION (kN/m 3)
RELATIVE UNCORRECTED SPT-N
DENSITY VALUES DRY AND MOIST
SUBMERGED SOILS
SOILS
Loose Less Than 10 15000 10000
Medium dense 10-30 45000 30000
Dense >30 175000 100000

Table 8-2—Presumptive modulus of subgrade reaction

Values for cohesive soils

SHEAR STRENGTH FROM

MODULUS OF SUBGRADE
CONSISTENCY UNCONFINED COMPRESSION TEST
REACTION (kN/m3)
(kPa)

Stiff 105-215 25000

Very stiff 215-430 50000
Rigid > 430 100000

Table 8-3—Maximum allowable differential settlements of mats

 SHAPE
DIFFERENTIAL SETTLEMENT

0
Rectangular base
Square base
0.0.355×∆
(mm)

×∆
0.5
 0.5
- 0.1×∆
Rigid mat: no differential settlement
a.
∆H
= Total settlement estimated based on approved methods of analysis but
shall not exceed values in Table 5-1.

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CHAPTER 9 DESIGN FOR EXPANSIVE SOILS

CHAPTER 9—DESIGN FOR EXPANSIVE SOILS

9.1—General 9.3.2 General requirements. Foundations

placed on or within the active zone of expansive
9.1.1 Provisions of this chapter shall apply to
soils shall be designed to resist differential volume
building foundation systems in expansive soil
changes and to prevent damage to the supported
areas. Foundation design and construction shall be
structure. Deflection and cracking of the supported
based on geotechnical investigations as defined in
structure shall be limited to that which will not
CHAPTER 2 , unless the building official ascertains
interfere with the usability and serviceability of the
that sufficient data upon which to base the design
structure. Foundations placed below where volume
and construction of the foundation system is
change occurs or below expansive soil shall comply
available.
with the following provisions:
9.1.2 Approval of special systems of design or
(1) Foundations extending into or penetrating
construction. Sponsors of any system of design or
expansive soils shall be designed to prevent
construction within the scope of CHAPTER 9 , the
uplift of the supported structure.
adequacy of which has been shown by successful
use or by analysis or test, but which does not (2) Foundations penetrating expansive soils
conform to or is not covered by CHAPTER 9 , shall shall be designed to resist forces exerted
have the right to present that data on which their on the foundation due to soil volume
design is based to the building official or to a board changes or shall be isolated from the
of examiners appointed by the building official. expansive soil.
This board shall be composed of competent 9.3.2.1 Geotechnical investigation report shall
geotechnical and structural engineers and shall have indicate the value or range of heave that might take
authority to investigate the data so submitted, to place for the subject structure. Potential soil
require tests, and to formulate rules governing movement shall be determined based on the
design and construction of such systems to meet the estimated depth of the active zone in combination
intent of CHAPTER 9 . These rules when approved
with either of the following:
by the building official and promulgated shall be of
the same force as the provisions of CHAPTER 9 . (1) ASTM-D 4546, or any other method
which can be documented and defended
9.2—Loadings as a good engineering practice in
9.2.1 Foundations shall be designed for the most accordance with the principles of
unfavorable effects due to the combinations of unsaturated soil mechanics carried out by
loads specified in Section 2.4 SBC 301. The dead a Geotechnical Engineer and approved
load shall include the weight of foundations and by the building official.
overlying fill. Reduced live loads, as specified in 9.3.3 Foundations. Foundations for buildings
SBC 301 Section 4.8, are permitted to be used in and structures founded on expansive soil areas shall
designing foundations. Strength design of be designed in accordance with Sections 9.3.3.1,
reinforced concrete systems and elements shall 9.3.3.2 , or 9.3.3.3. Alternate foundation designs
comply with load combinations specified in SBC shall be permitted subject to the provisions of
304. Section 9.1.2 . Foundation design need not comply
9.3—Design with Section 9.3.3.1 , 9.3.2.2, or 9.3.3.3 where the
soil is removed in accordance with Section 9.3.5 ,
9.3.1 Design for expansive soils shall be in nor where the building official approves
accordance with the provisions of Sections 9.3.2 stabilization of the soil in accordance with Section
through 9.3.6 . Provisions of CHAPTER 5 and 9.3.5 , nor where the superstructure is designed by a
CHAPTER 8 not specifically excluded and not in registered design professional to accommodate the
conflict with the provisions of CHAPTER 9 shall potential heave.
apply, where applicable.

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CHAPTER 9 DESIGN FOR EXPANSIVE SOILS

9.3.3.1 Shallow foundations. Continuous or expanded to include, but need not be limited to,
spread footings shall not be used on expansive soils the requirements of Sections 9.3.3.3.1and
unless the soil deposit has a low expansion 9.3.3.3.2.
potential, as determined in accordance with Table
9.3.3.3.1 General requirements.
9-1 or the superstructure is designed to account for
the potential foundation movement. The uplift (1) A void space shall be maintained beneath
pressures on the sides of the footing shall be the grade beam between the piers. The
minimized as much as possible. required void space shall be determined
based on the predicted heave of the soil
9.3.3.1.1 For continuous footings, the swell
beneath the beam but shall not be less
pressure shall be counteracted without exceeding
than 150 mm.
the bearing capacity of the soil deposit by
narrowing the width of the strip footing and/or (2) Care shall be taken in the design to
providing void spaces within the supporting beam provide for sealing the space between the
or wall. The continuous foundation shall be soil and the pier, such that deep seated
stiffened by increasing the reinforcement around heave that may result from water gaining
the perimeter and into the floor slab. access to soils below active zone along
the shaft of the pier, is prevented.
9.3.3.1.2 For spread footings, a void space shall be
provided beneath the grade beams using the same (3) Sufficient field penetration resistance
technique as described for pier and grade beam tests shall be performed not only to
construction in Section 9.3.3.3. The footings shall establish the proper friction value but
be designed using as high bearing pressure, as also to ensure that soft soils are not the
practicable. cause of tensile forces developed in the
pier.
9.3.3.2 Slab-on-ground foundations. Moments,
shears and deflections for use in designing slab- (4) The upper 1.5 m of soil around the pier
on-ground, mat or raft foundations on expansive shall be excluded when calculating the
soils shall be determined in accordance with pier load capacity.
WRI/CRSI Design of Slab-on-Ground Foundations.
(5) Friction piers shall not be used at sites
It shall be permitted to analyze and design such
where groundwater table is either high or
slabs by other methods that account for soil-
expected to become high in the future.
structure interaction, the deformed shape of the soil
support, the plate or stiffened plate action of the slab (6) Uplift skin friction shall be permitted to
as well as both center lift and edge lift conditions. be assumed constant throughout the
Such alternative methods shall be rational and the active zone.
basis for all aspects and parameters of the method (7) Where the upper soils are highly
shall be available for peer review. expansive or if there is a possibility of
9.3.3.2.1 A conventionally reinforced slab-on- loss of skin friction along the lower
ground mat or raft foundation shall conform to anchorage portion of the shaft due to rise
applicable provisions of SBC 304, where of groundwater table, the bottom of the
applicable. All variables affecting finished-slab shaft shall be belled or under-reamed.
performance shall be considered when selecting a The vertical side shall be a minimum of
slab type and when specifying or executing a slab 150 mm high and the sloping sides of the
design. All slab-on-ground mat or raft foundations, bell shall be formed at either 60o or 45o.
with the exception of conventionally reinforced For piers founded well below the active
2
slabs less than 50 m , shall be designed by a zone, the shaft may not be under-reamed.
registered design professional having sufficient (8) Upward movement of the top of the pier
knowledge and experience in structural and and the tensile forces developed in the
foundation engineering. Design of slab shall be pier shall be considered in the design of
conducted for conditions of both center and edge drilled piers.
heave. Construction joints shall be placed at
intervals not exceeding 4.5 m. (9) Mushrooming of the pier near the top
shall be avoided. Cylindrical cardboard
9.3.3.3 Beam-on-drilled pier. The design at/or extended above the top of the
provisions of Chapter 13 SBC 304 shall be

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CHAPTER 9 DESIGN FOR EXPANSIVE SOILS

concrete shall be used to prevent storm sewer or suitable ground surface

formation of mushroomed piers. location downhill.
9.3.3.3.2 Reinforcement. Reinforcing steel shall (3) The ground surface shall slope away
extend the entire length of the pier and shall be from the structure. Bare or paved areas
hooked into the belled bottom, if used, and into the shall have a slope not less than 2 %, and
grade beam at the top. The area of the steel shall be if possible the ground surface within 3
designed to resist all tensile loads to which the pier meters of the structure shall be sloped at
may be subjected but shall not be less than a a 10 percent grade.
minimum of 1 percent of the cross- sectional area
(4) Storage tanks and septic tanks shall be
of the pier.
reinforced to minimize cracking and
9.3.4 Removal of expansive soil. Where have adequate flexible water-proofing as
expansive soil is removed in lieu of designing per Section 13.5 .
foundations in accordance with Section 9.3.3.1 ,
(5) Plants and irrigation systems shall not be
9.3.3.2, or 9.3.3.3, the soil shall be removed to a
placed immediately adjacent to the
depth sufficient to ensure constant moisture
structure and spray heads shall be
content in the remaining soil. Fill material shall not
directed away from the structure. Large
contain expansive soils and shall comply with
trees and bushes shall be kept away from
Sections 3.6 and 3.10 or 3.11. If the expansive strata
the foundations for a distance greater
are not entirely removed, the fill material shall be
than half of their mature height.
impermeable enough not to provide access for water
into expansive grades or foundation soils. (6) If horizontal moisture barriers are
installed around the building to move
Exception: Expansive soil need not be removed to
edge effects away from the foundation
the depth of constant moisture, provided the
and minimize seasonal fluctuations of
confining pressure in the expansive soil created by
water content directly below the
the fill and supported structure exceeds the swell
structure, care shall be taken to seal
pressure.
joints, seams, rips, or holes in the barrier.
9.3.5 Stabilization. Where the active zone of Horizontal moisture barriers may take
expansive soils is stabilized in lieu of designing different forms including, but not
foundations in accordance with Section 9.3.3.1, necessarily limited to, membranes, rigid
9.3.3.2, or 9.3.3.3, the soil shall be stabilized by paving (concrete aprons, etc.), or flexible
chemical, installation of moisture barriers, pre- paving (asphalt membranes, etc.).
wetting or other techniques designed by a
(7) If vertical moisture barriers are used
geotechnical engineer knowledgeable in
around the perimeter of the building they
unsaturated soil mechanics and approved by the
shall be installed at least one meter from
building official. In pre-wetting technique, the
the foundation to a depth equal to or
effect of strength loss shall be evaluated to ensure
greater than the depth of seasonal
that strength criteria are met. Limitations and
moisture variation (active zone). Theses
implementation procedures of the contemplated
barriers may consist of polyvinyl
stabilization technique shall receive careful
chloride, polyethylene, polymer-
consideration and thorough evaluation.
modified asphalt or any other approved
9.3.6 Required preventive measures. methods or materials.
Applicable provisions of CHAPTER 13 shall be
(8) If the structure has a basement, the
expanded to include, but need not be limited to, the
backfill shall consist of non-expansive
following:
soils and it shall comply with Sections
(1) All water-supply pipes and wastewater 3.6 and 3.10 or 3.11 .
pipes shall be watertight and have
9.4—Pre-construction ins pections
flexible connections and couplings.
9.4.1 A pre-construction site inspection shall be
(2) All rainwater pipes shall be ducted well
performed to verify the following:
away from the foundations. It shall be
ensured that all water from downspout is
discharged away from the building into

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CHAPTER 9 DESIGN FOR EXPANSIVE SOILS

(1) Vegetation and associated root systems 9.5—Inspection pr ior to p lacement of

have been removed from the concrete
construction site.
9.5.1 Prior to the placement of concrete, an
(2) No beam trench cuttings or scarified inspection of the beam geometrics, penetrations,
material have been placed as fill material. cable(s), anchorage/steel placements and other
(3) All fill has been placed in accordance details of the design shall be made to verify
with Sections 3.6 and 3.10 or 3.11 in any conformance with the design plans.
portions or sections of the foundation 9.6—Concrete
supporting grade.
9.6.1 Material, construction, and placement of
(4) Proper soil compaction of the foundation concrete shall be in accordance with the provisions
footprint and fill material has been of Section 5.4.2 and Section 8.3 .
performed to a minimum of 95 percent
standard proctor density.

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CHAPTER 9 DESIGN FOR EXPANSIVE SOILS

TABL ES OF CHAPTER 9

Table 9-1—Classification of expansion potential

Expansion Index (EI) a
Expansion Potential

0 - 20 Very low
21 - 50 Low
51 - 90 Medium
91 - 130 High

> 130 Very high

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

CHAPTER 10—DESIGN FOR COLLAPSIBLE SOILS

10.1—General soil areas shall be designed in accordance with

Sections 10.3.2.1 through 10.3.2.2 Alternate
10.1.1 Provisions of this chapter shall apply to
foundation designs shall be permitted subject to the
building foundation systems on collapsible soil
provisions of Section 10.1.2. Footing or foundation
areas. Foundation design and construction shall be
design need not to comply with Sections 10.3.2.1
based on site investigations as defined in CHAPTER
and 10.3.2.2 where the soil is removed in
2 , unless the building official ascertains that
accordance with Section 10.3.3 , nor where the
sufficient data upon which to base the design and
building official approves stabilization of the soil in
construction of the foundation system is available.
accordance with Section 10.3.4 , nor where the
10.1.2 Approval of special systems of design or superstructure is designed by a registered design
construction. Sponsors of any system of design or professional to accommodate the potential collapse
construction within the scope of CHAPTER 10 , the settlements.
adequacy of which has been shown by successful
10.3.2.1 Classification of collapse potential.
use or by analysis or test, but which does not
Collapse potential shall be permitted to be
conform to or is not covered by CHAPTER 10 , shall
classified in accordance with one of the methods
have the right to present that data on which their
prescribed in Sections 10.3.2.1.1, 10.3.2.1.2, or
design is based to the building official or to a board
10.3.2.1.3.
of examiners appointed by the building official.
This board shall comprise of competent 10.3.2.1.1 Collapse index method. The
geotechnical and structural engineers and shall collapsibility of a particular soil under specified
have authority to investigate the data so submitted, conditions could be determined in accordance with
to require tests, and to formulate rules governing ASTM D5333. The specimen collapse shall be
design and construction of such systems to meet the classified according to the collapse index, Ie, as set
intent of CHAPTER 10 . These rules when approved forth in Table 10-1 .
by the building official and promulgated shall be of
10.3.2.1.2 S t a n d a r d plate load test
the same force as the provisions of CHAPTER 10 .
m e t h o d . Where undisturbed soil specimens are
10.2—Loadings irretrievable, collapse potential for specific field
conditions could be estimated from standard plate
10.2.1 Footings shall be designed for the most
load tests (SPLT), conducted in a test pit under
unfavorable effects due to the combinations of
unsoaked and soaked conditions in accordance with
loads specified in Section 2.4 SBC 301. The dead
ASTM D1194.
load shall include the weight of foundations,
footings and overlying fill. Reduced live loads, as 10.3.2.1.3 BREA infiltration and plate load test
specified in SBC 301 Section 4.8, are permitted to method. Collapse potential could be determined in
be used in designing footings. Strength design of accordance with BREA Building Regulations in
reinforced concrete systems and elements shall Eastern Arriyadh Sensitive Soils procedures
comply with load combinations specified in SBC (BPLT). The procedures shall apply to tests
304. performed in test pits or trenches. The infiltration
field test shall be performed in accordance with the
10.3—Design procedure set forth in Table 10-2 and the field plate
10.3.1 Design for collapsible soils shall be in load test shall be carried following the procedure
accordance with the provisions of Sections 10.3.2 outlined in Table 10-3 . The stability of the reaction
through 10.3.4 . Provisions of CHAPTER 5 and column and side-wall of the test pit shall be
CHAPTER 8 not specifically excluded and not in considered, particularly for test pits deeper than 4
conflict with the provisions of CHAPTER 10 shall meters.
apply, where applicable. 10.3.2.1.3.1 Design curve construction. A design
10.3.2 Foundations. Footings or foundations for curve for the site shall be constructed in accordance
buildings and structures founded on collapsible with the steps outlined in Table 10-4 . A data sheet

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

in the form shown in Table 10-4 may be used for the is taken equal to the value corresponding to
raw data gathered during the test and for the reduced settlement of test plate determined from Equation
data. (10-3) as follows:

 = 14 {1 } 
10.3.2.2 Design procedure. Based on the method
2
used in estimating the collapse potential of the soil
(10-3)
deposit as provided in Sections 10.3.2.1.1,
10.3.2.1.2, or 10.3.2.1.3, design for collapsible soils
shall be in accordance with Sections 10.3.2.2.1,
where:
10.3.2.2.2, or 10.3.2.2.3, respectively.
= Settlement of test plate;
10.3.2.2.1 Design based on collapse index.
Potential settlement that may occur in a soil layer
under the applied vertical stress is obtained as
 = Design settlement of prototype foundation
taken to be equal to half the allowable settlement
follows: value given from Section 5.4.1.5;

 = 100 
= Width of prototype footing; and
(10-1)  = Width of test plate.
10.3.2.2.2.1 Based on the obtained allowable load
where: bearing, the foundation system shall be designed in

 = potential settlement;
accordance with the provisions of CHAPTER 5 and
CHAPTER 8 , where applicable.
 = Thickness of the collapsible soil layer; and Limitations. In determining the bearing pressure
 = Collapse potential, determined using a
predetermined applied vertical stress applied to a
for the specified tolerable differential settlement,
the validity and accuracy of any resulting
soil specimen taken from the soil layer as follows: computations shall be approved by the building
official and evaluated on the basis of the following

 = ℎ 100 (10-2)

variables:
(1) Dependence of the amount of settlement
on the extent of the wetting front and
availability of water, which can rarely be
where: predicted prior to collapse.
= Specimen height at the appropriate stress level
before wetting;
(2) The influence depth set to be four times
the footing width is significantly
 = Specimen height at the appropriate stress level
after wetting; and
different for the model versus prototype
footing.

ℎ = Initial specimen height.

(3) Increased soil stiffness due to increase in
confinement with depth.
10.3.2.2.1.1 Based on settlement value determined
10.3.2.2.3 Design based on BPLT. Design of
by Equation (10-1), the foundation system shall be
spread and strip footings shall conform to the
designed in accordance with the provisions of
provisions of Section 10.3.2.2.3.1 and mats shall
CHAPTER 5 and CHAPTER 8 , where applicable.
be designed in accordance with the provisions of
10.3.2.2.1.2 Limitations. Amount of settlement Section 10.3.2.2.3.2.
depends on the extent of wetting front and
and continuous footings. Spread
10.3.2.2.3.1 Spread
availability of water, which can rarely be predicted
and continuous footings are permitted to be used
prior to collapse. Prediction of settlement based on
without modifications in areas with low collapse
collapse potential shall be viewed and interpreted
potential, as determined in accordance with. In
accordingly.
areas with higher collapse potential, strip footings
10.3.2.2.2 Design based on SPLT. From the load- are permitted, provided that the requirements for
deformation curve obtained from standard plate additional distortion resistance specified in Table
load test under soaked condition in accordance 10-8 are met.
with Section 10.3.2.1.2, the allowable load bearing

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

10.3.2.2.3.2 Stiffened mat foundations. The be evaluated to ensure that strength criteria are met.
design procedure for mat foundations in collapsible Great care must be exercised when using pre-
soils is summarized in Table 10-9 . The mat shall be wetting near existing structures that underlain by
designed and constructed in accordance with the collapsible soils, particularly if the soil has strong
provisions of CHAPTER 8 , where applicable, and stratification, as in the case of many alluvial soils,
the requirements for additional distortion and injected water may flow horizontally more than
resistance specified in Table 10-8 shall be met. it does vertically. Limitations and implementation
procedures of the contemplated stabilization
10.3.3 Removal of collapsible soil. Where
technique shall receive careful consideration and
collapsible soil is removed in lieu of designing
thorough evaluation.
footings or foundations in accordance with Section
10.3.2, the soil shall be removed to a sufficient 10.4—Inspections
depth to ensure constant moisture content in the
10.4.1 A pre-construction site inspection shall be
remaining soil. Fill material shall not contain
conducted to verify that the provisions of Section
collapsible soils and shall comply with the
9.4 have been met.
provisions of Sections 3.6 and 3.10 or 3.11 .
10.3.4 Stabilization. Where collapsible soils are 10.5—Concrete
stabilized in lieu of designing footings or 10.5.1 Material, construction, and placement of
foundations in accordance with Section 10.3.2, the concrete shall be in accordance with the provisions
soil shall be stabilized by compaction, pre-wetting, of Section 5.4.2 and Section 8.3 . Prior to the
vibroflotation, chemical, or other techniques placement of concrete, an inspection of the beam
designed by a geotechnical engineer knowledgeable geometrics, reinforcements and other details of the
in unsaturated soil mechanics and approved by the design shall be made to verify conformance with the
building official. The provisions of Section 9.3.6 design plans.
shall also be considered, where applicable. In pre-
wetting technique, the effect of strength loss shall

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

TABLES AND FIGURES OF CHAPTER 10

Figure 10-1—Extra steel in wall and floor for mat foundation.

Table 10-1—Classification of collapse potential

a Degree of Collapse
Collapse index (Ie) %
0 None
0.1-2.0 Slight
2.1-6.0 Moderate
6.1-10.0 Moderately severe
 10 Severe
a,
 = +∆ 100 ∆
where = change in void ratio resulting from wetting, and e
o
= initial void ratio.

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

Table 10-2—BREA infiltration field test procedure

1. Excavate a trench or test pit to the desired depth of testing and provide a smooth flat surface for testing. Do not backfill to
achieve smoothness.

2. At a distance no less than 3 plate diameters (3D) from the trench or test pit excavated in step 1, excavate a shallow
infiltration pit to a depth of 60 to 100 mm and a diameter of 2D. This pit for the preliminary rate-of-infiltration test shall be
separated by 3D from the supports of the reference beam. Measure the depth of the dry infiltration pit at the center.

3. Fill the infiltration pit with water and note the time at which wetting was commenced. Add water during infiltration as
needed to keep the bottom of the pit covered.

4. 
After an infiltration time, , of about 10 to 20 minutes, remove the excess water from the test pit, quickly excavate at the
center of the pit to locate the depth of wetting, and measure down to the wetting front. The depth of wetting from the
preliminary infiltration test ( ) is equal to depth of wetting front minus the original depth of the dry pit.

5. The infiltration coefficient for the preliminary test (  ) is computed as

Where:

 = ()/  = depth of infiltration for the preliminary infiltration test, mm.

 = infiltration coefficient for the preliminary infiltration test, mm/min 1/2.

 = time duration of infiltration for the preliminary infiltration test, min.

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

Table 10-3—BREA Plate Load Test Procedure (BPLT)

1. For the BPLT, choose the target depth of infiltration (  ), equal to 0.5 plate diameters (0.5D).

2.
Compute target time of infiltration (  ) from:  =  
3. Place the loading plate on a smooth flat surface and twist and tap lightly. The bottom of the loading plate may be coated with
5-10 mm of quick setting epoxy before placing it on the soil.
4. Construct a berm to hold water in preparation for ponding. The outside diameter of the ponded water shall be about 2D.

5. Install the reference beam to rest on firm supports located at least 3D from center of loading plate.

6. Attach displacement gauges so that they touch the loading plate on opposite sides and approximately equidistant from the
center of the plate.

7. Install the loading jack and reaction column.

8. Apply a seating load of 3 to 8 kPa and zero the displacement gauges. It may be convenient to use the weight of the loading
jack and plate as the seating load.

9. Increase load to 15 kPa. Wait one minute and take displacement readings.

10. Commence wetting and note starting time. Maintain water level 10 to 20 mm above the top of the plate.

11. Continue wetting until

kPa.
 (computed from step 2) has elapsed. Read displacement gauges, note time and increase load to 40

12. Wait ∆  ∆

minutes, read displacement gauges, note time, increase load to 100 kPa. The time increment
the larger of 2 minutes or 0.1 . For convenience, may be rounded to the nearest minute.
∆ may be chosen as

13. Wait ∆ minutes, read displacement gauges, note time, increase load to 200 kPa.

14. Wait ∆ minutes, read displacement gauges, note time, increase load to 400 kPa.

15. Wait ∆  

minutes, read displacement gauges, note time, remove load from the plate, remove the plate and quickly excavate to
determine the final depth ( ) and note the corresponding time .

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

Table 10-4—Data reduction for design curve construction

1. In column-1, description of the test stage. This will give meaning to column-2 (time column).
In column-2, time shall be recorded.
2.
3. 
In column-3, elapsed time ( ) shall be computed. Elapsed time is set equal to zero when ponding is commenced.

4. In column-4, pressure reading on the jack shall be recorded. A load cell could be substituted for the pressure gauge on the jack.
5. In column-5, the added load on the plate shall be recorded.

6. In column-6, the total load on the plate shall be recorded. This is obtained by adding column-5 to the weight (in kN) of the jack and
the loading plate.
7. In column-7, the left and right displacement gauges readings shall be recorded.

8. In column-8, the displacement, ∆

, for the left and right gauges shall be recorded. They are obtained by subtracting the initial gauge
readings at seating load from each subsequent reading.
9. In column-9, the average displacement ∆ ∆
is obtained by averaging the values from the left and right reading in column-8.

10.
/  /  
and then use it with 
to get  = 
from:
/
In column-10, the depth of wetting ( ) shall be computed by first determining
 =  
from:

11. In column-11, /shall be computed (column-10 divided by plate diameter).

12. In column-12, the influence factors   and /

obtained from the below figure at shall be recorded.

13. In column-13, the contact pressure (  ) shall be calculated by dividing column-6 by the plate area.

14.
 
In column-14, the average stress within the wetted zone
for first loading or for subsequent loadings).
shall be calculated by multiplying column-13  by column-12 ( 
15. In column-15, the average strain
result by 100.
 ∆
shall be computed by dividing column-9 by column-10 (  ) and multiplying the

16. Plot  versus for different tests on the same diagram. Obtain the average of all tests and draw a DESIGN CURVE.

Data sheet and computations

Date: Depth of Test Pit: Cip: Ztar:
Job No.: Ground Surface Elevation: Zwp: ttar:
Test Location: Test Pit tp:
t:
No.:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)
Total load on
Stage Time Elapsed Pressure reading Added load plate Dial gauge reading Displacement
Have Zw Zw/D IF or IS qcon qave  ave
time, t w on Jack (mm) (mm)
(kN)
(min.)
(min.) (kN) Left Right Left Right (mm) (mm) (kPa) (kPa) (percent)
Seating load
applied
Dry loading
Wetting
commenced
etc.

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

Table 10-5—Design of spread and strip footings on collapsible soils

1.

2.
From
Table 10-6, use strain under the plate corresponding to a stress of 100 kPa  ) to classify the site with respect
Pre-wetting is required for very high collapse potential, and permitted but not required for high collapse potential.

3. When pre-wetting is chosen or required, the DESIGN CURVE constructed in Table 10-4 is replaced with a recompression
design curve whose strain values are everywhere 15-percent of those on the original design curve, and the site is
4. Use

5. 
From Table 10-7 use column spacing, , to compute ∆  ∆ 
Table 10-6 and Table 10-7 to obtain re uired desi n arameters foundation de th
, then compute
de th of wetted bulb
from the same table.

6. Compute  =     = ∆ /
.
7. Compute maximum allowable   .
8. Compute the overburden pressure  
at .

9. From the DESIGN CURVE, get allowable 

corresponding to .

10. If ≥ allowable  from step-7, change 

, foundation type or stiffness level and recalculate.

 
=≥allalolwabl
owable e   
11. If , use allowable in the DESIGN CURVE to get allowable , then find as follows:

 
12.
 = allowabl
Assume a first trial value of
follows: e /
(footing width). Compute / 
, find from the figure below and compute  as

13.
  
Use the trial value of , footing shape and column load to compute .  ≈  
If
otherwise change and iterate until convergence, then proceed with structural design.

then value is accepted,

14. In case of no convergence or if

stiffness or a combination of those.
or 
are not acceptable, increase , change footing type, change distortion

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

Table 10-6—Minimum design parameters as a function of collapse potential

Minimum design Required
 100 Collapse Minimum Df Allowable types of
depth of wetting distortion
(percent) potential (m) foundation
Dwdes (m) stiffness
0 - 0.5 Low 1.0 3.5 Level 0 Spread, Strip, Mat
0.5 - 1.5 Moderate 1.5 3.5 Level I Strip, Mat
1.5 - 5.0 High 2.0 3.5 Level II Strip, Mat
> 5.0 Very high 2.5 3.5 Level II Strip, Mat

Table 10-7—Required minimum ratios of differential to totalsettlement as a

function of foundation type and distortion stiffness
Type of Min. Design Hdiff / Htot as a function of Required Extra
foundation Hdiff /L Distortion Resistance
Level 0 Level I Level II
Spread 1/500 0.85 0.75 0.65
Strip 1/500 0.65 0.55 0.45
Mat 1/500 0.35 0.30 0.25

Table 10-8—Requirements for extra distortion resistance

Distortion Type of Extra Extra Extra Steel Extra Steel Extra Steel in
Stiffness Foundation Concrete in Concrete in in Footing in Wall and Foundation
Grade Beam Footing Floor Column
Level 0 Refers to standard design and requires no extra distortion resistance
Spread 10 percent 10 percent −
2 bars 3 bars
Footing higher thicker
Strip 10 percent 10 percent −
Level I 2 bars 3 bars
Footing higher thicker
−
15 percent, see
Mat − − −
Figure 10.1
Spread 20 percent 20 percent −
3 bars 6 bars
Footing higher thicker
Strip 20 percent 20 percent −
Level II 3 bars 6 bars
Footing higher thicker
25 percent, see
Mat − − − −
Figure 10.1

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CHAPTER 10 DESIGN FOR COLLAPSIBLE SOILS

Table 10-9—Design of mat foundation on collapsible soils

1.

2.
From
Table 10-6, use strain under the plate corresponding to stress of 100 kPa  ) to classify the site with respect
Pre-wetting is required for very high collapse potential, and permitted but not required for high collapse potential.
3. When pre-wetting is chosen or required, the DESIGN CURVE is replaced with a recompression design curve whose
strain values are everywhere 15-percent of those on the original design curve, and the site is reclassified accordingly.
4. Use

5. Compute ∆ .

6. Compute  =    .
7. Compute maximum allowable  = ∆/ .
8.
 
Compute the overburden pressure
only a fraction of the
at 1/3 of the way from the base of the foundation to
acts on the soil during wetting as seen from the table below.
 . For mat foundations,

9.

The average contact stress under a mat, , is governed by the weight of the structure including the mat and the footprint

, /  

of the structure. Only and distortion stiffness can be chan ged in pursuit of an acceptable design.
10. Compute and estimate from Table 10-5, using the curve for square footing or interpolate between the
curves as a function of the shape of structure in plan (length/width ≥ 4 can be interpreted as strip).

11. Compute  =  ×

12. Compute  =  ×
mats and is obtained as:
, where the factor ‘ a ’represent percentage of overburden stress acting on the wetted soil under

/
0 - 0.1
0.1
0.1 - 0.3 0.3
0.3 - 0.6 0.5

13. Compute  =  

14. Enter the DESIGN CURVE to get  and compute ∆ =  × .
15. If ∆ ∆
allowable from above, the design is acceptable. Proceed with structural design.
16.
If ∆ ∆
allowable from above, increase  and/or increase distortion stiffness and recalculate ∆
Note:  =  = That portion of the overburden stress assumed to produce strain upon wetting.

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CHAPTER 11 DESIGN FOR SABKHA SOILS

CHAPTER 11—DESIGN FOR SABKHA SOILS

11.1—General specifically excluded and not in conflict with the

provisions of CHAPTER 11 shall apply, where
11.1.1 Provisions of this chapter shall apply to
applicable.
building foundation systems in sabkha soil areas.
Soils with high content of soluble or insoluble salts 11.3.2 General requirements. Foundations
and high salinity with occasional relatively hard placed on or within sabkha soils shall be designed
crusty surface can be classified as Sabkha. to prevent structural damage to the supported
Foundation design and construction shall be based structure due to detrimental settlement. Deflection
on geotechnical site investigations as defined in and racking of the supported structure shall be
CHAPTER 2 , unless the building official ascertains limited to that which will not interfere with the
that sufficient data upon which to base the design usability and serviceability of the structure. Design
and construction of the foundation system is shall consider, but need not limited to, the
available. following:
11.1.2 Approval of special systems of design or (1) The decrease in strength of the surface
construction. Sponsors of any system of design or crust of the sabkha as a result of moisture
construction within the scope of CHAPTER 11 , the content increase. This crust shall not be
adequacy of which has been shown by successful used as a foundation layer.
use or by analysis or test, but which does not (2) The variation of compressibility
conform to or is not covered by CHAPTER 11 , shall characteristics of the site resulting from
have the right to present that data on which their differences in layer thickness, degree of
design is based to the building official or to a board cementation, and relative density of
of examiners appointed by the building official.
different locations within the site.
This board shall consist of competent geotechnical
and structural engineers and shall have authority to (3) Differential settlements and foundation
investigate the data so submitted, to require tests, instabilities due to volume changes that
and to formulate rules governing design and accompany hydration and dehydration of
construction of such systems to meet the intent of gypsum rich layers under the hot and
CHAPTER 11 . These rules when approved by the humid conditions.
building official and promulgated shall be of the (4) High concentrations of chlorides and
same force as the provisions of CHAPTER 11 . sulfates in the sabkha sediments and
11.2—Loadings brines, and the subsequently highly
corrosive to both concrete and steel.
11.2.1 Foundations shall be designed for the most
unfavorable effects due to the combinations of 11.3.2.1 Soil investigation report shall indicate the
loads specified in SBC 301 Section 2.4. The dead value or range of settlement that might take place
load shall include the weight of foundations and for the subject structure. Potential settlements shall
overlying fill. Reduced live loads, as specified in be estimated by a method of analysis that can be
SBC 301 Section 4.8, are permitted to be used in documented and defended as a good engineering
designing foundations. Strength design of practice and approved by the building official.
reinforced concrete systems and elements shall Allowable settlements shall conform to the
comply with load combinations specified in SBC requirements of Sections 5.4.1.5 and 8.5 , where
304. applicable.

11.3—Design 11.3.3 Foundations. For heavy structures, mat or

deep foundations shall be considered, and
11.3.1 Design for sabkha soils shall conform to the provisions of CHAPTER 8 and CHAPTER 14 shall
provisions of Sections 11.3.2 through 11.3.3 . govern, where applicable.
Provisions of CHAPTER 5 and CHAPTER 8 not

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CHAPTER 11 DESIGN FOR SABKHA SOILS

11.3.3.1 For lightly loaded buildings and structures (1) Domestic and irrigation water shall be
founded on sabkha soil areas, and provided that strictly controlled, especially in low
water table is always kept beneath the foundation density sands cemented with sodium
level, it shall be permitted to design and construct chloride. Protection by drainage around
foundations in accordance with Sections 11.3.3.3 major structures shall be considered to
through 11.3.3.5 , subject to the approval of building reduce the risks associated with
official, and under a direct supervision of a rainstorms or water mains burst.
geotechnical engineer knowledgeable in sabkha
(2) There shall be external protection against
soils.
corrosion for all pipelines, fittings and
11.3.3.2 Alternate foundation designs shall be valves, whether it is made of steel,
permitted subject to the provisions of Section ductile iron, or asbestos-cement. Ductile
11.1.2. Foundation design need not to comply with iron pipe work shall be factory coated
Section 11.3.2 and 11.3.3 where the soil is removed with a bituminous coating compatible
in accordance with Section 11.6 , nor where the with a specified pipe wrapping material.
building official approves stabilization of the soil in Steel pipe work shall be factory coated
accordance with Section 11.7 , nor where the with either a thermosetting, fusion
superstructure is designed by a registered design bonded, dry powder epoxy coating not
professional to accommodate the potential less than 300 micrometers thick or a
settlements. catalyst-cured epoxy coating applied in
three coats, to a total cured dry film
11.3.3.3 Water table below 5 meters depth.
thickness of 240 micrometers. Ductile
Where groundwater is 5 meters below the ground
iron, steel and asbestos-cement pipe
surface level, external and internal walls have to be
work shall then be wrapped with durable
supported by a concrete strip foundation. Water
self-adhesive, rubber bitumen compound
infiltration shall be prevented under the floor slabs
with PVC carrier strip. The pipe work
by installing durable polythene sheeting, or other
shall be sleeved with 0.2 mm thick
approved materials, as shown in Figure 11-1 (a).
polyethylene sleeving.
Joints in the polythene sheeting shall be lapped and
sealed in accordance with the manufacturer’s 11.5—Concrete
installation instructions. Strip foundation shall be
11.5.1 Material, construction, and placement of
supported by lean mix concrete to prevent
concrete shall be in accordance with the provisions
contamination of the wet concrete when poured.
of Section 5.4.2 and Section 8.3 , where applicable.
11.3.3.4 Water table between 2.5 and 5 meters
11.5.2 Concrete protection. Concrete shall
depth. Where groundwater is between 2.5 meters
satisfy the durability criteria of SBC 304 Chapter 4.
and 5 meters below the ground surface level,
Protection against salt attack on foundation
provisions of Section 11.3.3.3 shall be satisfied.
materials, buried pipes, and metal objects shall be
Slab floors have to be supported by a strip
provided by using sulfate resistance cement.
foundation as illustrated in Figure 11-1 (b). Coarse,
Concrete used in the construction of foundation on
durable gravels shall be placed beneath the floor
sabkha formations shall be made from Type V
slab and around the strip foundation.
Portland cement, with minimum cement content of
11.3.3.5 Water table between ground level and 370 kg/m3, and maximum water cement ratio of 0.4
2.5 meters depth. Where groundwater is between for corrosion protection and 0.45 for sulfate
ground level and 2.5 meters, the provisions of protection. Reinforcement type shall be epoxy
Section 11.3.3.4 shall be fulfilled. Further, the strip coated and a minimum cover to reinforcement of 75
foundation and the floor slab shall also be underlain mm shall be stringently enforced.
by a rolled coarse gravel capillary cut-off, not less
than 150 mm thick, resting on a compacted fill 11.6—Removal of sabkha soils
blanket as illustrated in Figure 11-1 (c). 11.6.1 Where sabkha soil is removed in lieu of
designing foundations in accordance with Section
11.4—Requir ed preventive measures
11.3.3 , the soil shall be removed to a depth
11.4.1 The applicable provisions of Section 9.3.6 sufficient to ensure adequate load-bearing capacity
and CHAPTER 13 shall be expanded to include, but and tolerable settlement for the remaining soil. Fill
need not be limited to, the following: material shall not contain sabkha soils and shall
comply with the provisions of Sections 3.10 or 3.11 .

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CHAPTER 11 DESIGN FOR SABKHA SOILS

11.7—Stabilization reduce its settlement characteristics, the upper,

loose portion of sabkha shall be densified, or treated
11.7.1 Where the sabkha soil is stabilized in lieu
without adversely affecting the underlying
of designing foundations in accordance with
cemented layers. In pre-wetting technique, the
Section 11.3.3, the soil shall be stabilized by stone
effect of strength loss shall be evaluated to ensure
columns, preloading, vibroflotation, or other
that strength criteria are met. Limitations and
techniques designed by a geotechnical engineer
implementation procedures of the contemplated
knowledgeable in sabkha soil and approved by the
stabilization technique shall receive careful
building official. Where attempts to densify the
consideration and thorough evaluation.
upper portion of sabkha material by conventional
means, in order to improve its bearing capacity and

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CHAPTER 11 DESIGN FOR SABKHA SOILS

TABLES AND FIGURES OF CHAPTER 11

Figure 11-1—Shallow foundation design strategies: (a) Water table below 5 m depth; (b) Water
table between 2.5 m and 5 m depth; (c) Water table between ground level and 2.5 m depth.

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CHAPTER 12 DESIGN FOR VIBRATORY LOADS

CHAPTER 12—DESIGN FOR VIBRATORY LOADS

12.1—General with exact location of centers of gravity, number of

revolutions per minute (Operating speed or range of
12.1.1 Where machinery operations or other
operating speeds), diagrams showing all primary
vibrations are transmitted through the foundation,
and secondary forces and moments, and curves of
the foundations and support structures shall be
free forces and moments against crank angle
designed according to Sections 12.2 through 12.4.8 .
degrees.
Foundations and support structures designed for
machinery vibrations must be capable of 12.2.5.1 For rotating machinery, the equipment
withstanding dynamic loading due to machinery manufacturer(s) shall supply the weights of the
vibrations and all other loadings to which they may machine, rotor and auxiliary equipment with exact
be subjected with stresses not exceeding the location of centers of gravity, range of operating
allowable-load bearing values specified in speeds, possible unbalanced forces and points of
CHAPTER 4 . application (for operating conditions based on
alarm level). Where there is no manufacturer
12.2—Loads information available, the steady state dynamic
12.2.1 All concrete sections shall be proportioned force for rotating machinery can be estimated as
to resist the sum of the static loads and dynamic follows:
loads as described in Sections 12.2.2 through 12.2.5 .
12.2.2 Static loads. Static loads shall consist of all
dead and live loads on the foundation, etc., thermal
 = 0.001. (12-1)

and fluid forces from process piping, loads due to where:

temperature differentials, wind loads and any other
sustained loads.  = Steady state dynamic force in kN;

12.2.3 Transient dynamic loads. If not specified  = Total mass of the rotating part in kg; and
by the equipment manufacturer, transient forces
consisting of vertical, lateral, and longitudinal
 = Machine speed in revolutions per minute.

forces equal to 25 percent of the total weight of the 12.3—Soil bearing pressures, pile
machine train and acting through the center capacities and settlements
machine bearing axis shall be used in design. These 12.3.1 Foundation adequacy for static bearing
forces need not be considered to act concurrently. capacity and settlement considerations shall be
For purposes of strength design, the forces shall be checked by a registered design professional. In
treated as quasi-static loads. addition, effect of dynamic loading on foundation
12.2.4 For low-tuned systems, dynamic load soil shall be investigated. In-situ or laboratory
effects due to transient resonance during machine testing to establish appropriate dynamic parameters
start-up or shut-down shall be considered. For of the foundation soils, whether in-situ treated or
transient response calculations, damping effects untreated, or compacted fill, shall be carried out by
shall be included to avoid unrealistically high an approved agency. If a requirement for piles is
results as the frequency ratio passes through the 0.7 established, appropriate dynamic parameters for the
to 1.3 range. Unless foundations or structures or piles shall be determined by an approved agency.
connecting piping are unusual, response due to 12.3.2 The site investigation report shall give
transient dynamic forces need not be evaluated. insight to the expected dynamic behavior of the soil
12.2.5 Steady state dynamic forces. Information or piles. As a minimum the report should give the
on steady state dynamic forces shall be furnished by density, Poisson’s ratio, dynamic modulus of sub-
the equipment manufacturer(s). For reciprocating grade reaction or dynamic pile spring constant and
machinery, the supplied information shall include the shear modulus for soils, or the equivalent fixate
weights of the machine and all auxiliary equipment level of piles.

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CHAPTER 12 DESIGN FOR VIBRATORY LOADS

12.3.3 Unless foundation settlement calculations machinery shall be large enough to avoid
for dynamic loads show otherwise, the allowable transmission of detrimental vibration
soil bearing pressures shall not exceed 50% of the amplitudes through the surrounding soil
allowable bearing pressure permitted for static or the foundations shall be protected in
loads, as determined from CHAPTER 4 , for high- other ways. Transmissibility of
tuned foundations and 75% for low-tuned amplitudes shall be limited to 20 percent
foundations. The allowable soil bearing pressure between adjacent foundations, unless
shall be reduced for heavy machinery foundations otherwise agreed by the Building
to provide a factor of safety against excessive official.
settlement due to vibrations.
(6) Where practical and economical, the
12.4—Design requirements machine foundation system shall be
proportioned to be low-tuned.
12.4.1 Foundation and support structures designed
for machinery vibrations shall meet the provisions (7) High-tuned machine foundation systems
of Sections 12.4.2 through 12.4.8 . shall be used only when a low-tuned
system is not practical or economical.
12.4.2 General. The provisions of CHAPTER 5
and CHAPTER 8 shall be expanded to include the (8) For elevated machinery, the flexibility of
following: the entire support structure shall be
considered in the dynamic analysis.
(1) Support structures or foundations for
centrifugal rotating machinery greater (9) The foundation design shall be capable
than 500 horsepower shall be designed of resisting all applied dynamic and static
for the expected dynamic forces using loads specified by the machinery
dynamic analysis procedures. For units manufacturer, loads from thermal
less than 500 horsepower, in the absence movement, dead and live loads, wind or
of a detailed dynamic analysis, the seismic forces as specified in SBC 301,
foundation weight shall be at least three any loads that may be associated with
times the total machinery weight, unless installation or maintenance of the
specified otherwise by the manufacturer. equipment, and fatigue. For fatigue, the
dynamic loads shall be increased by a
(2) For reciprocating machinery less than
factor of 1.5 and applied as quasi-static
200 horsepower, in the absence of a
loads.
detailed dynamic analysis, the
foundation weight shall be at least five The applied loads shall be combined to produce the
times the total machinery weight, unless most unfavorable effect on the supporting
specified otherwise by the manufacturer. foundations. The effect of both wind and seismic
activity need not be considered to act
(3) All coupled elements of the machinery
simultaneously. Design load combinations shall be
train shall be mounted on a common
as specified in Section 2.4 SBC 301 except that
foundation or support structure.
strength design of reinforced concrete systems and
(4) Foundations for heavy machinery shall elements shall comply with load combinations
be independent of adjacent foundations specified in SBC 304.
and buildings. Concrete slabs or paving
(1) Design shall be such that buried cables,
adjacent to the foundation shall have a
pipes etc., will not be incorporated in the
minimum 12 mm isolation joint around
foundation, and be protected from the
the foundation using an approved elastic
influence of foundation stresses. If
joint filler with sealant on top. Joint filler
incorporation in the foundation cannot be
material shall be an expansion joint
avoided, cables and pipes shall be
material according to ACI 504R Guide
sleeved.
for Sealing Joints in Concrete Structures.
Preformed expansion joint filler shall be (2) Where practical, operator platforms shall
of the full thickness and depth of the joint be independent from the main machinery
with splicing only on the length. carrying structure(s).
(5) The clear distance in any direction (3) Quantifying whole-body vibration in
between adjacent foundations for heavy relation to human health and comfort, the

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CHAPTER 12 DESIGN FOR VIBRATORY LOADS

probability of vibration perception, and (5) When foundation thickness is greater

the incidence of motion sickness shall than 1200 mm thick, mix and placement
conform to International Organization of concrete shall conform to the
for Standardization ISO 2631-1 provisions of ACI 207.2R-07 and SBC
Mechanical Vibration and Shock 304.
Evaluation of Human Exposure to
12.4.4 Anchor bolts. Anchor bolts shall be in
Whole-Body Vibration-Part 1: General
accordance with SAES-Q-005. When specified, the
Requirements and Evaluation of Human
diameter, steel quality, projection and installation
Exposure to Whole-Body Vibration-Part
method shall be as required by the machine
2: Continuous and Shock-induced
manufacturer. Requirements for anchor bolt coating
Vibration in Buildings (1 to 80 Hz) ISO
shall be in compliance with Saudi Aramco
2631-2.
Materials System Reports 12-SAMSS-007
12.4.3 Reinforced concrete. The structural Fabrication of Structural and Miscellaneous Steel
design of all reinforced concrete shall be in and requirements for double nuts shall be in
accordance with SBC 304 when not in conflict with compliance with Saudi Aramco Engineering
the provisions of CHAPTER 12 . The following Standard SAES-Q-005 Concrete Foundations.
provisions shall be satisfied:
12.4.4.1 The foundation design engineer shall
(1) The minimum compressive strength of verify the capacity of any vendor furnished or
concrete at 28 days shall not be less than detailed anchor bolts. Unless otherwise specified by
28 MPa. the equipment manufacturer, equipment shall be
installed on mounting plate(s), and the direct
(2) All faces of concrete shall be reinforced
attachment of equipment feet to the foundation
bi-axially. For deformed bars, the
using the anchor bolts shall not be permitted.
reinforcement in each direction shall not
Mounting plates shall be of sufficient strength and
be less than 0.0018 times the gross area
rigidity to transfer the applied forces to the
perpendicular to the direction of
foundation. Grouting shall be in accordance with
reinforcement.
Saudi Aramco Engineering Standard SAES-Q-011
Exception: In an event that a foundation size Epoxy Grout for machinery Support and machine
greater than 1200 mm thick is required for stability, manufacturer’s instructions.
rigidity, or damping, the minimum reinforcing steel
12.4.4.2 The drawing shall clearly indicate the
may be as recommended in ACI 207.2R-07 Effect
locations and types of the anchor bolts and sleeves,
of Restraint, Volume Change, and Reinforcement
the anchor bolt diameter, the depth of embedment
on Cracking of Massive Concrete with a suggested
into the foundation of the anchor bolts, the length of
minimum reinforcement of Dia 22 mm bars at 300
the anchor bolts threads, and the length of the
mm on center.
anchor bolt projections.
(1) Main reinforcement in piers shall not be
12.4.5 Stiffness requirements. The foundation
less than 1 percent and not more than 8
must be of sufficient width to prevent rocking and
percent of the cross-sectional area of the
adequate depth to permit properly embedded anchor
piers. Main reinforcement in pedestals
bolts. The width of the foundation shall be at least
shall not be less than 1/2 percent.
1.5 times the vertical distance from the base to the
(2) Minimum tie size in piers shall be 12 machine centerline, unless analysis carried out by a
mm. registered design professional demonstrates that a
lesser value will perform adequately. For concrete
(3) Maximum tie spacing in piers shall be the
foundations, the weight of the foundation for
smallest of 8-bar diameters, 24-tie
reciprocating equipment shall not be less than 5
diameters or 1/3 the least dimension of
times and, for rotary equipment, shall not be less
the pier.
than 3 times the weight of the machinery, including
(4) Slabs with thickness of 500 mm or more its base plate and the piping supported from the
shall be provided with shrinkage and foundation, unless analysis carried out by a
temperature reinforcement in accordance registered design professional demonstrates that a
with applicable provisions of SBC 304. lesser value will perform adequately.

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CHAPTER 12 DESIGN FOR VIBRATORY LOADS

12.4.5.1 For foundations and piers constructed with 12.4.6.1 The horizontal eccentricity, parallel to the
normal weight concrete, the dynamic modulus of bearing axis between the center of gravity of the
elasticity shall be taken as: machine foundation system and the centroid of the
soil contact area (or in the case of piled foundations,
 = 6560. (12-2)
the elastic support point of the pile group) shall not
exceed 0.05 times length of foundation in meters.
The machine bearing axis and the centroid of the
where: support (soil contact area, or pile group) shall lie in
= Dynamic modulus of elasticity of concrete in
MPa; and
a common vertical plane.
12.4.6.2 Piers and columns shall be proportioned in

= Compressive strength of concrete at 28 days in
MPa.
such a manner that the centroid of their vertical
stiffness lies in the same vertical plane as the
bearing axis and center of gravity of the machinery.
12.4.5.2 The minimum thickness of the concrete
foundations shall not be less than (0.60+L/30) 12.4.7 Permissible frequency ratios. The ratio
where L is the length of foundation in meters between the operating frequency of the machinery,
parallel to the machine bearing axis in meters. Piers f, and each natural frequency of the machine
shall not be used unless absolutely required by foundation system, fn shall not lie in the range of 0.7
operation or maintenance or if required by machine to 1.3. Accordingly, for high-tuned systems, f/fn,
vendor specification. Block foundations for shall be less than 0.7 and for low-tuned systems f/fn
reciprocating machines shall have a minimum of 50 shall be greater than 1.3. A need for exceptions shall
% of the block thickness embedded in the soil, be approved by a registered design professional.
unless otherwise specified by the equipment 12.4.8 Permissible vibration. Where
manufacturer. Manufacturer’s vibration criteria are not available,
12.4.6 Allowable eccentricities for concrete the maximum velocity of movement during steady-
foundations with horizontal shaft machinery. state normal operation shall be limited to 3 mm per
Secondary moments that could significantly second for centrifugal machines and 4 mm per
influence the natural frequencies of the foundation second for reciprocating machines. For rocking and
shall be minimized. The horizontal eccentricity, torsional mode calculation the vibration velocities
perpendicular to the machine bearing axis, between shall be computed with the dynamic forces of the
the center of gravity of the machine foundation machinery train components assumed in phase and
system and the centroid of the soil contact area (or 180 degrees out of phase.
in case of piled foundations, the elastic support
point of the pile group) shall not exceed 0.05 times
the width of foundation in meters.

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CHAPTER 13 DAMPPROOFING A ND WATERPROOFING

CHAPTER 13—DAMPPROOFING AND WATERPROOFING

13.1—Scope the lowest floor, the floor and walls shall be

dampproofed in accordance with Section 13.2. The
13.1.1 Walls or portions thereof that retain earth
design of the system to lower the ground-water
and enclose interior spaces and floors below grade,
table shall be based on accepted principles of
and underground water-retention structures shall be
engineering that shall consider, but not necessarily
waterproofed and dampproofed in accordance with
be limited to, permeability of the soil, rate at which
provisions of this Chapter, with the exception of
water enters the drainage system, rated capacity of
those spaces containing groups other than
pumps, head against which pumps are to operate
residential and institutional where such omission is
and the rated capacity of the disposal area of the
not detrimental to the building or occupancy.
system.
Ventilation for crawl spaces shall comply with
Section 7.3.4 SBC 201. 13.2—Dampproofing
13.1.2 Story above grade plane. Where a 13.2.1 Where hydrostatic pressure will not occur
basement is considered a story above grade plane as determined by Section 2.2.3.4 , floors and walls
and the finished ground level adjacent to the shall be dampproofed in accordance with this
basement wall is below the basement floor Section.
elevation for 25 percent or more of the perimeter,
For a general definition of “Dampproofing,” see the
the floor and walls shall be dampproofed in
commentary to Section 13.1. Where a ground-water
accordance with Section 13.2 and a foundation
table investigation made in accordance with the
drain shall be installed in accordance with Section
requirements of Section 2.2.3.4 (see commentary)
13.4.3. The foundation drain shall be installed
has established that the high water table will occur
around the portion of the perimeter where the
at such a level that the building substructure will not
basement floor is below ground level. The
be subjected to hydrostatic pressure, then
provisions of Sections 2.2.3.4, 13.3 and 13.4.2 shall
dampproofing in accordance with this section and a
not apply in this case.
subsoil drain in accordance with Section 13.4 are
13.1.3 Under-floor space. The finished ground sufficient to control moisture in the floor below
level of an under-floor space such as a crawl space grade. Since the wall will not be subject to water
shall not be located below the bottom of the under pressure, the more restrictive provisions of
footings. Where there is evidence that the ground- waterproofing, as outlined in Section 13.3 , are not
water table rises to within 150 mm of the ground required.
level at the outside building perimeter, or that the
13.2.2 Floors. Dampproofing materials for floors
surface water does not readily drain from the
shall be installed between the floor and the base
building site, the ground level of the under-floor
course required by Section 13.4.2, except where a
space shall be as high as the outside finished ground
separate floor is provided above a concrete slab.
level, unless an approved drainage system is
provided. The provisions of Sections 2.2.3.4, 13.2 , 13.2.2.1 Where installed beneath the slab,
13.3 and 13.4.2 shall not apply in this case. dampproofing shall consist of not less than 0.15 mm
polyethylene with joints lapped not less than 150
13.1.3.1 Flood hazard areas. For buildings and
mm, or other approved methods or materials.
structures in flood hazard areas, as established in
Where permitted to be installed on top of the slab,
SBC 301 Section 5.3, the finished ground level of
dampproofing shall consist of mopped-on bitumen,
an under-floor space such as a crawl space shall be
not less than 0.10 mm polyethylene, or other
equal to or higher than the outside finished ground
approved methods or materials. Joints in the
level on at least one side.
membrane shall be lapped and sealed in accordance
Exception: Under-floor spaces of Group R-3 with the manufacturer’s installation instructions.
buildings that meet the requirements of FEMA-TB
13.2.3 Walls. Dampproofing materials for walls
11.
shall be installed on the exterior surface of the wall,
13.1.4 Groundwater control. Where the ground- and shall extend from the top of the footing to above
water table is lowered and maintained at an ground level.
elevation not less than 150 mm below the bottom of

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CHAPTER 13 DAMPPROOFING AND W ATERPROOFING

13.2.3.1 Surface preparation of walls. Prior to or masonry walls, the walls shall be prepared in
application of dampproofing materials on concrete accordance with Section 13.2.3.1.
walls, holes and recesses resulting from the removal
13.3.4 Joints and penetrations. Joints in walls
of form ties shall be sealed with a bituminous
and floors, joints between the wall and floor and
material or other approved methods or materials.
penetrations of the wall and floor shall be made
Unit masonry walls shall be parged on the exterior
water-tight utilizing approved methods and
surface belowground level with not less than 10 mm
materials.
of Portland cement mortar. The parging shall be
coved at the footing. 13.4—Subsoil drainage system
Exception: Parging of unit masonry walls is not 13.4.1 Where a hydrostatic pressure condition
required where a material is approved for direct does not exist, dampproofing shall be provided and
application to the masonry. a base shall be installed under the floor and a drain
installed around the foundation perimeter. A subsoil
13.3—Waterproofing
drainage system designed and constructed in
13.3.1 Where the ground-water investigation accordance with Section 13.1.4 shall be deemed
required by Section 2.2.3 indicates that a hydrostatic adequate for lowering the ground-water table.
pressure condition exists, and the design does not
13.4.2 Floor base course. Floors of basements,
include a ground-water control system as described
except as provided for in Section 13.1.2, shall be
in Section 13.1.4, walls and floors shall be
placed over a floor base course not less than 100
waterproofed in accordance with this Section.
mm in thickness that consists of gravel or crushed
13.3.2 Floors. Floors required to be waterproofed stone containing not more than 10 percent of
shall be of concrete, designed and constructed to material that passes through a No.4 (4.75 mm)
withstand the hydrostatic pressures to which the sieve.
floors will be subjected.
Exception: Where a site is located in well-drained
13.3.2.1 Waterproofing shall be accomplished by gravel or sand/gravel mixture soils, a floor base
placing a membrane of rubberized asphalt, butyl course is not required.
rubber, fully adhered/fully bonded HDPE or
13.4.3 Foundation drain. A drain shall be placed
polyolefin composite membrane or not less than
around the perimeter of a foundation. It shall satisfy
0.15 mm polyvinyl chloride with joints lapped not
the requirements of Equation (7-4) through
less than 150 mm or other approved materials under
Equation (7-6) in lieu it shall consist of gravel or
the slab. Joints in the membrane shall be lapped and
crushed stone containing not more than 10-percent
sealed in accordance with the manufacturer’s
material that passes through a No. 4 (4.75 mm)
installation instructions.
sieve. The drain shall extend a minimum of 300 mm
13.3.3 Walls. Walls required to be waterproofed beyond the outside edge of the footing. The
shall be of concrete or masonry and shall be thickness shall be such that the bottom of the drain
designed and constructed to withstand the is not higher than the bottom of the base under the
hydrostatic pressures and other lateral loads to floor, and that the top of the drain is not less than
which the walls will be subjected. 150 mm above the top of the footing. The top of the
drain shall be covered with an approved filter
13.3.3.1 Waterproofing shall be applied from the
membrane material. Where a drain tile or perforated
bottom of the wall to not less than 300 mm above
pipe is used, the invert of the pipe or tile shall not
the maximum elevation of the groundwater table.
be higher than the floor elevation. The top of joints
The remainder of the wall shall be dampproofed in
or the top of perforations shall be protected with an
accordance with Section 13.2.3. Waterproofing
approved filter membrane material. The pipe or tile
shall consist of two-ply hot-mopped felts, not less
shall be placed on not less than 50 mm of gravel or
than 0.15 mm polyvinyl chloride, 1.0 mm polymer-
crushed stone complying with Section 13.4.2, and
modified asphalt, 0.150 mm polyethylene or other
shall be covered with not less than 150 mm of the
approved methods or materials capable of bridging
same material.
nonstructural cracks. Joints in the membrane shall
be lapped and sealed in accordance with the 13.4.4 Drainage discharge. The floor base and
manufacturer’s installation instructions. foundation perimeter drain shall discharge by
gravity or mechanical means into an approved
13.3.3.2 Surface preparation of walls. Prior to the
drainage system that complies with the SBC 701.
application of waterproofing materials on concrete

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CHAPTER 13 DAMPPROOFING AND W ATERPROOFING

Exception: Where a site is located in well-drained Environmental Engineering Concrete Structures

gravel or sand/gravel mixture soils, a dedicated shall govern, where applicable.
drainage system is not required.
13.5.4 Waterproofing. All internal faces of an
13.5—Underground water-retention underground water-retention structure shall be
structures waterproofed (using approved material such as
epoxy films, concrete admixtures, etc.). All such
13.5.1 Underground water-retention structures waterproofing materials in contact with water shall
shall meet the provisions of Sections 13.5.2 through neither be toxic nor hazardous to human health. All
13.5.5. construction joints shall have proper water-stops.
13.5.2 General requirements. All underground All construction holes, recesses, plumbing sleeves
water-retention structures shall meet the following etc. shall be sealed properly.
requirements: 13.5.4.1 In cases where the floor slab of the water-
(1) All internal faces (including the top face) retention structure is less than one meter above the
of the water-retention structure shall be anticipated groundwater level, it is required to
waterproofed. provide a base layer of compacted granular fill,
followed by dampproofing layer as described in
(2) Shall not be located under drainage or
Section 13.2.2 .
non-potable water piping.
13.5.4.2 In cases where floor slab is below or close
(3) Shall be provided with a waterproof to groundwater level, the floor slab and all exterior
cover to prevent water and foreign matter faces of the structure shall be waterproofed in
from entering the tank. The cover shall accordance with Section 13.3 . In cases where cover
be large enough to allow access for slab of the structure is below or close to
maintenance. groundwater level, all parts of the structure
(4) Underground tanks in flood hazard areas (including the opening of the water-retention
shall be anchored to prevent flotation, structure) shall be waterproofed in accordance with
collapse or lateral movement resulting Section 13.3 .
from hydrostatic loads, including the
13.5.5 Testing. Following complete application of
effects of buoyancy, during conditions of waterproofing of the structure, and before
the design flood. backfilling is permitted; underground water-
13.5.3 Design and construction. For design and retention structures shall be tested against leakage
constructions of underground water-retention full of water for a minimum of 48 hours.
structures, provisions of SBC 304 and ACI 350

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CHAPTER 14 DEEP FOUNDATIONS

CHAPTER 14—DEEP FOUNDATIONS

14.1—General 14.2—Analysis
14.1.1 Deep foundations shall be analyzed, 14.2.1 The analysis of deep foundations for design
designed, detailed and installed in accordance with shall be in accordance with Sections 14.2.2 through
Sections 14.1 through 14.4 . 14.2.6 .

14.1.2 Geotechnical investigation. Deep 14.2.2 Lateral support. Any soil other than fluid
foundations shall be designed and installed on the soil shall be deemed to afford sufficient lateral
basis of a geotechnical investigation as set forth in support to prevent buckling of deep foundation
CHAPTER 2 . elements and to permit the design of the elements
in accordance with accepted engineering practice
14.1.3 Use of existing deep foundation
and the applicable provisions of this code.
elements. Deep foundation elements left in place
where a structure has been demolished shall not be 14.2.2.1 Where deep foundation elements stand
used for the support of new construction unless unbraced in air, water or fluid soils, it shall be
satisfactory evidence is submitted to the building permitted to consider them laterally supported at a
official, which indicates that the elements are sound point 1500 mm into stiff soil or 3050 mm into soft
and meet the requirements of this code. Such soil unless otherwise approved by the building
elements shall be load tested or redriven to verify official on the basis of a geotechnical investigation
their capacities. The design load applied to such by a registered design professional.
elements shall be the lowest allowable load as
14.2.3 Stability. Deep foundation elements shall
determined by tests or redriving data.
be braced to provide lateral stability in all directions.
14.1.4 Deep foundation elements classified as Three or more elements connected by a rigid cap
columns. Deep foundation elements standing shall be considered braced, provided that the
unbraced in air, water or fluid soils shall be elements are located in radial directions from the
classified as columns and designed as such in centroid of the group not less than 60 degrees (1
accordance with the provisions of this code from rad) apart. A two-element group in a rigid cap shall
their top down to the point where adequate lateral be considered to be braced along the axis
support is provided in accordance with Section connecting the two elements. Methods used to
14.2.2. brace deep foundation elements shall be subject to
the approval of the building official.
Exception: Where the unsupported height to least
horizontal dimension of a cast-in-place deep 14.2.3.1 Deep foundation elements supporting
foundation element does not exceed three, it shall walls shall be placed alternately in lines spaced at
be permitted to design and construct such an least (300 mm) apart and located symmetrically
element as a pedestal in accordance with SBC 304. under the center of gravity of the wall load carried,
unless effective measures are taken to provide for
14.1.5 Special types of deep foundations. The
eccentricity and lateral forces, or the foundation
use of types of deep foundation elements not
elements are adequately braced to provide for
specifically mentioned herein is permitted, subject
lateral stability.
to the approval of the building official, upon the
submission of acceptable test data, calculations and Exceptions:
other information relating to the structural
(1) Isolated cast-in-place deep foundation
properties and load capacity of such elements. The
elements without lateral bracing shall be
allowable stresses for materials shall not in any
permitted where the least horizontal
case exceed the limitations specified herein.
dimension is no less than 600 mm,
adequate lateral support in accordance
with Section 14.2.2 is provided for the
entire height and the height does not

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CHAPTER 14 DEEP FOUNDATIONS

exceed 12 times the least horizontal reinforcement is within seven times the
dimension. least element dimension of the pile cap
and within seven times the least element
(2) A single row of deep foundation
dimension of the interfaces of strata that
elements without lateral bracing is
are hard or stiff and strata that are
permitted for one- and two-family
liquefiable or are composed of soft- to
dwellings and lightweight construction
medium-stiff clay.
not exceeding two stories above grade
plane or 10,500 mm in building height, 14.2.6 Group effects. The analysis shall include
provided the centers of the elements are group effects on lateral behavior where the center-
located within the width of the supported to-center spacing of deep foundation elements in
wall. the direction of lateral force is less than eight times
the least horizontal dimension of an element. The
14.2.4 Settlement. The settlement of a single deep
analysis shall include group effects on axial
foundation element or group thereof shall be
behavior where the center-to-center spacing of
estimated based on approved methods of analysis.
deep foundation elements is less than three times
The predicted settlement shall cause neither harmful
the least horizontal dimension of an element.
distortion of, nor instability in, the structure, nor
Group effects shall be evaluated using a generally
cause any element to be loaded beyond its capacity.
accepted method of analysis; the analysis for uplift
14.2.5 Lateral loads. The moments, shears and of grouped elements with center-to-center spacing
lateral deflections used for design of deep less than three times the least horizontal dimension
foundation elements shall be established of an element shall be evaluated in accordance with
considering the nonlinear interaction of the shaft Section 14.3.4.1.6.
and soil, as determined by a registered design
professional. Where the ratio of the depth of 14.3—Design and detailing
embedment of the element to its least horizontal 14.3.1 Deep foundations shall be designed and
dimension is less than or equal to six, it shall be detailed in accordance with Sections 14.3.2 through
permitted to assume the element is rigid. 14.3.14 .
14.2.5.1 Seismic Design Category D through F. 14.3.2 Design conditions. Design of deep
For structures assigned to Seismic Design Category foundations shall include the design conditions
D through F, as determined in Section 1613.3.2 of specified in Sections 14.3.2.1 through 14.3.2.6, as
SBC 201, shall be designed and constructed to applicable.
withstand maximum imposed curvatures from
14.3.2.1 Design methods for concrete elements.
earthquake ground motions and structure response.
Where concrete deep foundations are laterally
Curvatures shall include free-field soil strains
supported in accordance with Section 14.2.2 for the
modified for soil-foundation-structure interaction
entire height and applied forces cause bending
coupled with foundation element deformations
moments no greater than those resulting from
associated with earthquake loads imparted to the
accidental eccentricities, structural design of the
foundation by the structure.
element using the load combinations of Section
Exception: Deep foundation elements that satisfy 1605.3 of SBC 201 and the allowable stresses
the following additional detailing requirements specified in this chapter shall be permitted.
shall be deemed to comply with the curvature Otherwise, the structural design of concrete deep
capacity requirements of this section. foundation elements shall use the load combinations
(1) Precast prestressed concrete piles of Section 1605.2 of SBC 201 and approved strength
detailed in accordance with Section design methods.
14.3.9.3. 14.3.2.2 Composite elements. Where a single
(2) Cast-in-place deep foundation elements deep foundation element comprises two or more
with a minimum longitudinal sections of different materials or different types
reinforcement ratio of 0.005 extending spliced together, each section of the composite
the full length of the element and assembly shall satisfy the applicable requirements
detailed in accordance with Sections of this code, and the maximum allowable load in
18.7.5.2, 18.7.5.3 and 18.7.5.4 of SBC each section shall be limited by the structural
304 such that the transverse confinement capacity of that section.

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CHAPTER 14 DEEP FOUNDATIONS

14.3.2.3 Mislocation. The foundation or seismic hooks, as defined in SBC 304, and shall be
superstructure shall be designed to resist the effects turned into the confined concrete core.
of the mislocation of any deep foundation element
14.3.3.1.3 SBC 304 Equation (25.7.3.3). Where
by no less than 75 mm. To resist the effects of
this chapter requires detailing of concrete deep
mislocation, compressive overload of deep
foundation elements in accordance with Section
foundation elements to 110 percent of the
18.7.5.4 of SBC 304, compliance with Equation
allowable design load shall be permitted.
(25.7.3.3) of SBC 304 shall not be required.
14.3.2.4 Driven piles. Driven piles shall be
14.3.3.2 Prestressing steel. Prestressing steel shall
designed and manufactured in accordance with
conform to ASTM A 416.
accepted engineering practice to resist all stresses
induced by handling, driving and service loads. 14.3.3.3 Steel. Structural steel H-piles and
structural steel sheet piling shall conform to the
14.3.2.5 Helical piles. Helical piles shall be
material requirements in ASTM A 6. Steel pipe
designed and manufactured in accordance with
piles shall conform to the material requirements in
accepted engineering practice to resist all stresses
ASTM A 252. Fully welded steel piles shall be
induced by installation into the ground and service
fabricated from plates that conform to the material
loads.
requirements in ASTM A 36, ASTM A 283, ASTM
14.3.2.6 Casings. Temporary and permanent A 572, ASTM A 588 or ASTM A 690.
casings shall be of steel and shall be sufficiently
14.3.3.4 Timber. Timber foundations are not
strong to resist collapse and sufficiently water tight
applicable to the Kingdom of Saudi Arabia (KSA).
to exclude any foreign materials during the placing
of concrete. Where a permanent casing is 14.3.3.5 Protection of materials. Where boring
considered reinforcing steel, the steel shall be records or site conditions indicate possible
protected under the conditions specified in Section deleterious action on the materials used in deep
14.3.3.5. Horizontal joints in the casing shall be foundation elements because of soil constituents,
spliced in accordance with Section 14.3.7 . changing water levels or other factors, the elements
shall be adequately protected by materials, methods
14.3.3 Materials. The materials used in deep
or processes approved by the building official.
foundation elements shall satisfy the requirements
Protective materials shall be applied to the elements
of Sections 14.3.3.1 through 14.3.3.8, as applicable.
so as not to be rendered ineffective by installation.
14.3.3.1 Concrete. Where concrete is cast in a The effectiveness of such protective measures for
steel pipe or where an enlarged base is formed by the particular purpose shall have been thoroughly
compacting concrete, the maximum size for established by satisfactory service records or other
coarse aggregate shall be 19 mm. Concrete to be evidence.
compacted shall have a zero slump.
14.3.3.6 Allowable stresses. The allowable stress
14.3.3.1.1 Concrete or grout strength and mix for materials used in deep foundation elements shall


proportioning. Concrete or grout in foundations
shall have a specified compressive strength ( ) not
less than the largest applicable value indicated in
not exceed those specified in Table 14-2.
14.3.3.7 . Increased allowable compressive stress
for cased cast-in-place elements. The allowable
Table 14-1 .
compressive stress in the concrete shall be
14.3.3.1.1.1 Where concrete is placed through a permitted to be increased as specified in Table 14-2
funnel hopper at the top of a deep foundation for those portions of permanently cased cast-in-
element, the concrete mix shall be designed and place elements that satisfy all of the following
proportioned so as to produce a cohesive workable conditions:
mix having a slump of not less than 100 mm and not
(1) The design shall not use the casing to
more than 200 mm. Where concrete or grout is to
resist any portion of the axial load
be pumped, the mix design including slump shall be
imposed.
adjusted to produce a pumpable mixture.
(2) The casing shall have a sealed tip and be
14.3.3.1.2 Seismic hooks. For structures assigned
mandrel driven.
to Seismic Design Category C or D the ends of
hoops, spirals and ties used in concrete deep (3) The thickness of the casing shall not be
foundation elements shall be terminated with less than manufacturer's standard gage
No. 14 (1.75 mm).

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(4) The casing shall be seamless or provided the size, strength and weight of the driven elements.
with seams of strength equal to the basic The use of a follower is permitted only with the
material and be of a configuration that approval of the building official. The introduction
will provide confinement to the cast-in- of fresh hammer cushion or pile cushion material
place concrete. just prior to final penetration is not permitted.
(5)
 
The ratio of steel yield strength ( ) to
specified compressive strength ( ) shall
not be less than six.
14.3.4.1.2 Load tests. Where design compressive
loads are greater than those determined using the
allowable stresses specified in Section 14.3.3.6,
where the design load for any deep foundation
(6) The nominal diameter of the element element is in doubt, or where cast-in-place deep
shall not be greater than 400 mm. foundation elements have an enlarged base formed
14.3.3.8 Justification of higher allowable either by compacting concrete or by driving a
stresses. Use of allowable stresses greater than precast base, control test elements shall be tested in
those specified in Section 14.3.3.6 shall be accordance with ASTM D 1143 or ASTM D 4945.
permitted where supporting data justifying such At least one element shall be load tested in each
higher stresses is filed with the building official. area of uniform subsoil conditions. Where required
Such substantiating data shall include the by the building official, additional elements shall
following: be load tested where necessary to establish the safe
design capacity. The resulting allowable loads shall
(1) A geotechnical investigation in
not be more than one-half of the ultimate axial load
accordance with CHAPTER 2 .
capacity of the test element as assessed by one of
(2) Load tests in accordance with Section the published methods listed in Section 14.3.4.1.3
14.3.4.1.2, regardless of the load with consideration for the test type, duration and
supported by the element. subsoil. The ultimate axial load capacity shall be
determined by a registered design professional with
14.3.3.8.1 The design and installation of the deep
consideration given to tolerable total and
foundation elements shall be under the direct
differential settlements at design load in accordance
supervision of a registered design professional
with Section 14.2.4 . In subsequent installation of
knowledgeable in the field of soil mechanics and
the balance of deep foundation elements, all
deep foundations who shall submit a report to the
elements shall be deemed to have a supporting
building official stating that the elements as
capacity equal to that of the control element where
installed satisfy the design criteria.
such elements are of the same type, size and
14.3.4 Determination of allowable loads. The relative length as the test element; are installed
allowable axial and lateral loads on deep using the same or comparable methods and
foundation elements shall be determined by an equipment as the test element; are installed in
approved formula, load tests or method of analysis. similar subsoil conditions as the test element; and,
for driven elements, where the rate of penetration
14.3.4.1 Allowable axial load. The allowable
(e.g., net displacement per blow) of such elements is
axial load on a deep foundation element shall be
equal to or less than that of the test element driven
determined in accordance with Sections 14.3.4.1
with the same hammer through a comparable
through 14.3.4.1.9.
driving distance.
14.3.4.1.1 Driving criteria. The allowable
14.3.4.1.3 Load test evaluation methods. It shall
compressive load on any driven deep foundation
be permitted to evaluate load tests of deep
element where determined by the application of an
foundation elements using any of the following
approved driving formula shall not exceed 360 kN.
methods:
For allowable loads above 360 kN, the wave
equation method of analysis shall be used to (1) Davisson Offset Limit.
estimate driveability for both driving stresses and
(2) Brinch-Hansen 90-percent Criterion.
net displacement per blow at the ultimate load.
Allowable loads shall be verified by load tests in (3) Butler-Hoy Criterion.
accordance with Section 14.3.4.1.2. The formula or
(4) Other methods approved by the building
wave equation load shall be determined for gravity-
official.
drop or power-actuated hammers and the hammer
energy used shall be the maximum consistent with

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14.3.4.1.4 Allowable frictional resistance. The 14.3.4.1.7 Load-bearing capacity. Deep

assumed frictional resistance developed by any foundation elements shall develop ultimate load
uncased cast-in-place deep foundation element capacities of at least twice the design working loads
shall not exceed one-sixth of the bearing value of in the designated load-bearing layers. Analysis shall
the soil material at minimum depth as set forth in show that no soil layer underlying the designated
Table 4-1 , up to a maximum of 24 kPa, unless a load-bearing layers causes the load-bearing
greater value is allowed by the building official on capacity safety factor to be less than two.
the basis of a geotechnical investigation as
14.3.4.1.8 Bent deep foundation elements. The
specified in CHAPTER 2 or a greater value is
load-bearing capacity of deep foundation elements
substantiated by a load test in accordance with
discovered to have a sharp or sweeping bend shall
Section 14.3.4.1.2. Frictional resistance and bearing
be determined by an approved method of analysis
resistance shall not be assumed to act
or by load testing a representative element.
simultaneously unless determined by a
geotechnical investigation in accordance with
Section CHAPTER 2 . 
14.3.4.1.9 Helical piles. The allowable axial
design load, , of helical piles shall be determined
as follows:
14.3.4.1.5 Uplift capacity of a single deep
foundation element. Where required by the
design, the uplift capacity of a single deep
foundation element shall be determined by an
 = 0.5 (14-1)

approved method of analysis based on a minimum

factor of safety of three or by load tests conducted
where  is the least value of:

in accordance with ASTM D 3689. The maximum (1) Sum of the areas of the helical bearing
allowable uplift load shall not exceed the ultimate plates times the ultimate bearing capacity
load capacity as determined in Section 14.3.4.1.2, of the soil or rock comprising the bearing
using the results of load tests conducted in stratum.
accordance with ASTM D 3689, divided by a factor (2) Ultimate capacity determined from well-
of safety of two. documented correlations with
Exception: Where uplift is due to wind or seismic installation torque.
loading, the minimum factor of safety shall be two (3) Ultimate capacity determined from load
where capacity is determined by an analysis and one tests.
and one-half where capacity is determined by load
tests. (4) Ultimate axial capacity of pile shaft.

14.3.4.1.6 Uplift capacity of grouped deep (5) Ultimate axial capacity of pile shaft
foundation elements. For grouped deep couplings.
foundation elements subjected to uplift, the (6) Sum of the ultimate axial capacity of
allowable working uplift load for the group shall be helical bearing plates affixed to pile.
calculated by a generally accepted method of
analysis. Where the deep foundation elements in the 14.3.4.2 Allowable lateral load. Where required
group are placed at a center-to-center spacing less by the design, the lateral load capacity of a single
than three times the least horizontal dimension of deep foundation element or a group thereof shall be
the largest single element, the allowable working determined by an approved method of analysis or
uplift load for the group is permitted to be by lateral load tests to at least twice the proposed
calculated as the lesser of: design working load. The resulting allowable load
shall not be more than one-half of the load that
(1) The proposed individual allowable produces a gross lateral movement of 25 mm at the
working uplift load times the number of lower of the top of foundation element and the
elements in the group. ground surface, unless it can be shown that the
(2) Two-thirds of the effective weight of the predicted lateral movement shall cause neither
group and the soil contained within a harmful distortion of, nor instability in, the
block defined by the perimeter of the structure, nor cause any element to be loaded
group and the length of the element, plus beyond its capacity.
two-thirds of the ultimate shear 14.3.5 Special soil conditions. Deep foundations
resistance along the soil block. to be installed through subsiding or calcareous soils

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shall be designed in accordance with Sections registered design professional shall submit a report
14.3.5.1 through 14.3.5.2, as applicable. to the building official stating that the elements
were installed in compliance with the approved
14.3.5.1 Subsiding soils. Where deep foundation
construction documents.
elements are installed through subsiding fills or
other subsiding strata and derive support from 14.3.6.2.3 Micropiles. Micropiles shall have an
underlying firmer materials, consideration shall be outside diameter of 300 mm or less. The minimum
given to the downward frictional forces that may diameter set forth elsewhere in Section 14.3.6
be imposed on the elements by subsiding upper shall not apply to micropiles.
strata.
14.3.6.3 Steel. Steel deep foundation elements
14.3.5.1.1 Where the influence of subsiding fills is shall satisfy the requirements of this section.
considered as imposing loads on the element, the
14.3.6.3.1 Structural steel H-piles. Sections of
allowable stresses specified in this chapter shall be
structural steel H-piles shall comply with the
permitted to be increased where satisfactory
requirements for HP shapes in ASTM A 6, or the
substantiating data are submitted.
following:
14.3.5.2 Piles in calcareous soils. Where piles are
(1) The flange projections shall not exceed
driven through calcareous soils and derive support
14 times the minimum thickness of metal
from frictional forces developed between the pile
in either the flange or the web and the
and the surrounding soil, consideration shall be
flange widths shall not be less than 80
given to loss of frictional forces due to driving. For
percent of the depth of the section.
bored cast in-situ piles within calcareous soils
where support is derived from both friction and tip (2) The nominal depth in the direction of the
resistance, consideration shall be given to the web shall not be less than 200 mm.
possibility of presence of voids/cavities below the
(3) Flanges and web shall have a minimum
tip of the bored pile.
nominal thickness of 9.5 mm.
14.3.6 Dimensions of deep foundation
14.3.6.3.2 Fully welded steel piles fabricated
elements. The dimensions of deep foundation
from plates. Sections of fully welded steel piles
elements shall be in accordance with Sections
fabricated from plates shall comply with the
14.3.6.1 through 14.3.6.3, as applicable.
following:
14.3.6.1 Precast. The minimum lateral dimension
(1) The flange projections shall not exceed
of precast concrete deep foundation elements shall
14 times the minimum thickness of metal
be 200 mm. Corners of square elements shall be in either the flange or the web and the
chamfered. flange widths shall not be less than 80
14.3.6.2 Cast-in-place or grouted-in-place. Cast- percent of the depth of the section.
in-place and grouted-in-place deep foundation (2) The nominal depth in the direction of the
elements shall satisfy the requirements of this web shall not be less than 200 mm.
section.
(3) Flanges and web shall have a minimum
14.3.6.2.1 Cased. Cast-in-place deep foundation nominal thickness of 9.5 mm.
elements with a permanent casing shall have a
nominal outside diameter of not less than 200 mm. 14.3.6.3.3 Structural steel sheet piling. Individual
sections of structural steel sheet piling shall
14.3.6.2.2 Uncased. Cast-in-place deep foundation conform to the profile indicated by the
elements without a permanent casing shall have a manufacturer, and shall conform to the general
diameter of not less than 300 mm. The element requirements specified by ASTM A 6.
length shall not exceed 30 times the average
diameter. 14.3.6.3.4 Steel pipes and tubes. Steel pipes and
tubes used as deep foundation elements shall have
Exception: The length of the element is permitted a nominal outside diameter of not less than 200 mm.
to exceed 30 times the diameter, provided the Where steel pipes or tubes are driven open ended,
design and installation of the deep foundations they shall have a minimum of 220 mm2 of steel in
are under the direct supervision of a registered cross section to resist each 1350 N-m of pile
design professional knowledgeable in the field of
hammer energy, or shall have the equivalent
soil mechanics and deep foundations. The strength for steels having a yield strength greater

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than 240 MPa or the wave equation analysis shall 14.3.7.2 Seismic Design Categories C and D.
be permitted to be used to assess compression For structures assigned to Seismic Design
stresses induced by driving to evaluate if the pile Categories C and D splices of deep foundation
section is appropriate for the selected hammer. elements shall develop the lesser of the following:
Where a pipe or tube with wall thickness less than
(1) The nominal strength of the deep
4.6 mm is driven open ended, a suitable cutting shoe
foundation element.
shall be provided. Concrete-filled steel pipes or
tubes in structures assigned to Seismic Design (2) The axial and shear forces and moments
Category C or D shall have a wall thickness of not from the seismic load effects including
less than 4.75 mm. The pipe or tube casing for overstrength factor in accordance with
socketed drilled shafts shall have a nominal outside Section 12.4.3 or 12.14.3.2 of SBC 301.
diameter of not less than 460 mm, a wall thickness
14.3.8 Top of element detailing at cutoffs.
of not less than 9.5 mm and a suitable steel driving
Where a minimum length for reinforcement or the
shoe welded to the bottom; the diameter of the rock
extent of closely spaced confinement reinforcement
socket shall be approximately equal to the inside
is specified at the top of a deep foundation element,
diameter of the casing.
provisions shall be made so that those specified
Exceptions: lengths or extents are maintained after cutoff.
(1) There is no minimum diameter for steel 14.3.9 Precast concrete piles. Precast concrete
pipes or tubes used in micropiles. piles shall be designed and detailed in accordance
with Sections 14.3.9.1 through 14.3.9.3 .
(2) For mandrel-driven pipes or tubes, the
minimum wall thickness shall be 2.5 14.3.9.1 Reinforcement. Longitudinal steel shall
mm. be arranged in a symmetrical pattern and be
laterally tied with steel ties or wire spiral spaced
14.3.6.3.5 Helical piles. Dimensions of the central
center to center as follows:
shaft and the number, size and thickness of helical
bearing plates shall be sufficient to support the (1) At not more than 25 mm for the first five
design loads. ties or spirals at each end; then
14.3.7 Splices. Splices shall be constructed so as (2) At not more than 100 mm, for the
to provide and maintain true alignment and position remainder of the first 600 mm from each
of the component parts of the deep foundation end; and then
element during installation and subsequent thereto
(3) At not more than 150 mm elsewhere.
and shall be designed to resist the axial and shear
forces and moments occurring at the location of the 14.3.9.1.1 The size of ties and spirals shall be as
splice during driving and for design load follows:
combinations. Where deep foundation elements (1) For piles having a least horizontal
of the same type are being spliced, splices shall dimension of 400 mm or less, wire shall
develop not less than 50 percent of the bending not be smaller than 5.6 mm (No. 5 gage).
strength of the weaker section. Where deep
foundation elements of different materials or (2) For piles having a least horizontal
different types are being spliced, splices shall dimension of more than 400 mm and less
develop the full compressive strength and not less than 500 mm, wire shall not be smaller
than 50 percent of the tension and bending strength than 6 mm (No. 4 gage).
of the weaker section. Where structural steel cores (3) For piles having a least horizontal
are to be spliced, the ends shall be milled or ground dimension of 500 mm and larger, wire
to provide full contact and shall be full-depth welded. shall not be smaller than 6.5 mm round
14.3.7.1 Splices occurring in the upper 3000 mm of or 6.6 mm (No. 3 gage).
the embedded portion of an element shall be 14.3.9.2 Precast nonprestressed piles. Precast
designed to resist at allowable stresses the moment non-prestressed concrete piles shall comply with
and shear that would result from an assumed the requirements of Sections 14.3.9.2.1 through
eccentricity of the axial load of 75 mm, or the 14.3.9.2.3.
element shall be braced in accordance with Section
14.2.3 to other deep foundation elements that do not 14.3.9.2.1 Minimum reinforcement. Longitudinal
have splices in the upper 3000 mm of embedment. reinforcement shall consist of at least four bars

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with a minimum longitudinal reinforcement ratio of

0.008.

= Yield strength of spiral reinforcement < 590
MPa; and
14.3.9.2.2 Seismic reinforcement in Seismic
Design Categories C through F. For structures
= Spiral reinforcement index (vol. of spiral/vol.
core).
assigned to Seismic Design Categories C, D, E or
F, precast nonprestressed piles shall be reinforced At least one-half the volumetric ratio required by
as specified in this section. The minimum Equation (14-2) shall be provided below the upper
longitudinal reinforcement ratio shall be 0.01 6000 mm of the pile.
throughout the length. Transverse reinforcement 14.3.9.3.3 Seismic reinforcement in Seismic
shall consist of closed ties or spirals with a minimum Design Category D through F. For structures
9.5 mm diameter. Spacing of transverse assigned to Seismic Design Categories D, E or F,
reinforcement shall not exceed the smaller of eight precast prestressed piles shall have transverse
times the diameter of the smallest longitudinal bar or reinforcement in accordance with the following:
150 mm within a distance of three times the least pile
(1) Requirements in SBC 304, Chapter 18,
dimension from the bottom of the pile cap. Spacing
need not apply, unless specifically
of transverse reinforcement shall not exceed 150 mm
referenced.
throughout the remainder of the pile.
(2) Where the total pile length in the soil is
14.3.9.2.3 Additional seismic reinforcement in
11,000 mm or less, the lateral transverse
Seismic Design Category D through F. For
reinforcement in the ductile region shall
structures assigned to Seismic Design Categories
occur through the length of the pile.
D, E or F, transverse reinforcement shall be in
Where the pile length exceeds 11,000
accordance with Section 14.3.10.4.2.
mm, the ductile pile region shall be taken
14.3.9.3 Precast prestressed piles. Precast as the greater of 11,000 mm or the
prestressed concrete piles shall comply with the distance from the underside of the pile
requirements of Sections 14.3.9.3.1 through cap to the point of zero curvature plus
14.3.9.3.3. three times the least pile dimension.
14.3.9.3.1 Effective prestress. The effective (3) In the ductile region, the center-to-center
prestress in the pile shall not be less than 2.80 MPa spacing of the spirals or hoop
for piles up to 9200 mm in length, 3.80 MPa, for reinforcement shall not exceed one-fifth
piles up to 15,500 mm in length and 4.80 MPa of the least pile dimension, six times the
for piles greater than 15,500 mm in length. diameter of the longitudinal strand or 200
14.3.9.3.1.1 Effective prestress shall be based on an mm, whichever is smallest.
assumed loss of (210 MPa) in the prestressing steel. (4) Circular spiral reinforcement shall be
The tensile stress in the prestressing steel shall not spliced by lapping one full turn and
exceed the values specified in SBC 304. bending the end of each spiral to a 90-
14.3.9.3.2 Seismic reinforcement in Seismic degree hook or by use of a mechanical or
Design Category C. For structures assigned to welded splice complying with Section
Seismic Design Category C, precast prestressed 25.5.7 of SBC 304.
piles shall have transverse reinforcement in (5) Where the transverse reinforcement
accordance with this section. The volumetric ratio consists of circular spirals, the
of spiral reinforcement shall not be less than 0.007 volumetric ratio of spiral transverse
or the amount required by the following formula for reinforcement in the ductile region shall
the upper 6000 mm of the pile. comply with the following:

 = 0.12/ (14-2)  = 0.25(⁄)(⁄ 1.0)

where:
[0.51.4⁄( )] (14-3)


= Specified compressive strength of concrete
(MPa);
but not less than

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 = 0.12(⁄ )  = Spacing of transverse reinforcement measured

along length of pile, (mm);

[0.51.4⁄()] 0.12 ⁄ (14-4)

ℎ = Cross-sectional
reinforcement, (mm2); and
area of transverse

and need not exceed: 

= Specified compressive strength of concrete,
(MPa).

 = 0.021 (14-5) 14.3.9.3.3.1 The hoops and cross ties shall be

equivalent to deformed bars not less than 9.5 mm in
size. Rectangular hoop ends shall terminate at a
where:
 = Pile cross-sectional area, (mm2);
corner with seismic hooks.
14.3.9.3.3.2 Outside of the length of the pile
= Core area defined by spiral outside diameter,
(mm2);
requiring transverse confinement reinforcing, the
spiral or hoop reinforcing with a volumetric ratio


= Specified compressive strength of concrete,
(MPa);
not less than one-half of that required for transverse
confinement reinforcing shall be provided.


= Yield strength of spiral reinforcement < 590
MPa;
14.3.10 Cast-in-place deep foundations. Cast-in-
place deep foundation elements shall be designed
and detailed in accordance with Sections 14.3.10.1
= Axial load on pile, (kN), as determined from
Equations 16-5 and 16-7 of SBC 201; and
through 14.3.10.6 .
14.3.10.1 Design cracking moment. The design
 = Volumetric ratio (vol. of spiral/vol. core). cracking moment (Mn) for a cast-in-place deep
foundation element not enclosed by a structural
This required amount of spiral reinforcement is steel pipe or tube shall be determined using the
permitted to be obtained by providing an inner and following equation:
outer spiral.
(1) Where transverse reinforcement consists
of rectangular hoops and cross ties, the
 = 0.25√ (14-8)

total cross-sectional area of lateral

transverse reinforcement in the ductile where:
region with spacing, s, and perpendicular
dimension, hc, shall conform to:
= Specified compressive strength of concrete or
grout, (MPa); and

=1.0.43ℎ⁄((⁄)] )⁄ 1 [0.5
= Elastic section modulus, neglecting
reinforcement and casing, (mm3).
(14-6)
14.3.10.2 Required reinforcement. Where
subject to uplift or where the required moment
strength determined using the load combinations of
but not less than: Section 1605.2 of SBC 201 exceeds the design
cracking moment determined in accordance with
 = 0.12ℎ(1.⁄4⁄)[0.(5)] (14-7)
Section 14.3.10.1, cast-in-place deep foundations
not enclosed by a structural steel pipe or tube shall
be reinforced.
14.3.10.3 Placement of reinforcement.
where:
= Yield strength of transverse reinforcement <
480 MPa;
Reinforcement where required shall be assembled
and tied together and shall be placed in the deep
foundation element as a unit before the reinforced
ℎ= Cross-sectional dimension of pile core
measured center to center of hoop reinforcement,
portion of the element is filled with concrete.
Exceptions:
(mm); (1) Steel dowels embedded 1550 mm or less
shall be permitted to be placed after

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concreting, while the concrete is still in a soil provides adequate lateral support in
semi- fluid state. accordance with Section 14.2.2.
(2) For deep foundation elements installed (3) Deep foundation elements supporting the
with a hollow-stem auger, tied concrete foundation wall of Group R-3
reinforcement shall be placed after and U occupancies not exceeding two
elements are concreted, while the stories of light-frame construction shall
concrete is still in a semifluid state. be permitted to be reinforced as required
Longitudinal reinforcement without by rational analysis but with not less than
lateral ties shall be placed either through two 12 mm bars, without ties or spirals,
the hollow stem of the auger prior to where the design cracking moment
concreting or after concreting, while the determined in accordance with Section
concrete is still in a semifluid state. 14.3.10.1 exceeds the required moment
strength determined using the load
(3) For Group R-3 and U occupancies not
combinations with overstrength factor in
exceeding two stories of light-frame
Section 12.4.3.2 or 12.14.3.2 of SBC 301
construction, reinforcement is permitted
and the soil provides adequate lateral
to be placed after concreting, while the
support in accordance with Section
concrete is still in a semifluid state, and
14.2.2 .
the concrete cover requirement is
permitted to be reduced to 50 mm, (4) Closed ties or spirals where required by
provided the construction method can be Section 14.3.10.4.2 shall be permitted to
demonstrated to the satisfaction of the be limited to the top 900 mm of deep
building official. foundation elements 3000 mm or less in
depth supporting Group R-3 and U
14.3.10.4 Seismic reinforcement. Where a
occupancies of Seismic Design Category
structure is assigned to Seismic Design Category C,
D, not exceeding two stories of light-
reinforcement shall be provided in accordance with
frame construction.
Section 14.3.10.4.1. Where a structure is assigned
to Seismic Design Category D, E, or F, 14.3.10.4.1 Seismic reinforcement in Seismic
reinforcement shall be provided in accordance with Design Category C. For structures assigned to
Section 14.3.10.4.2. Seismic Design Category C, cast-in-place deep
foundation elements shall be reinforced as specified
Exceptions:
in this section. Reinforcement shall be provided
(1) Isolated deep foundation elements where required by analysis.
supporting posts of Group R-3 and U
14.3.10.4.1.1 A minimum of four longitudinal
occupancies not exceeding two stories of
bars, with a minimum longitudinal reinforcement
light-frame construction shall be
ratio of 0.0025, shall be provided throughout the
permitted to be reinforced as required by
minimum reinforced length of the element as
rational analysis but with not less than
defined below starting at the top of the element.
one 12 mm bar, without ties or spirals,
The longitudinal reinforcement shall extend beyond
where detailed so the element is not
the minimum reinforced length of the pile by the
subject to lateral loads and the soil
tension development length. The minimum
provides adequate lateral support in
reinforced length of the element shall be taken as the
accordance with Section 14.2.2.
greatest of the following:
(2) Isolated deep foundation elements
(1) One-third of the element length.
supporting posts and bracing from decks
and patios appurtenant to Group R-3 and (2) A distance of 3000 mm.
U occupancies not exceeding two stories
(3) Three times the least element dimension.
of light-frame construction shall be
permitted to be reinforced as required by (4) The distance from the top of the element
rational analysis but with not less than to the point where the design cracking
one 12 mm bar, without ties or spirals, moment determined in accordance with
where the lateral load, E, to the top of the Section 14.3.10.1 exceeds the required
element does not exceed 890 N and the moment strength determined using the

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load combinations of Section 1605.2 of load combinations of Section 1605.2 of

SBC 201. SBC 201.
14.3.10.4.1.2 Transverse reinforcement shall 14.3.10.4.2.2 Transverse reinforcement shall
consist of closed ties or spirals with a minimum 9.5 consist of closed ties or spirals no smaller than 9.5
mm diameter. Spacing of transverse reinforcement mm bars for elements with a least dimension up to
shall not exceed the smaller of 150 mm or 8- 500 mm, and 12 mm bars for larger elements.
longitudinal-bar diameters, within a distance of Throughout the remainder of the reinforced length
three times the least element dimension from the outside the regions with transverse confinement
bottom of the pile cap. Spacing of transverse reinforcement, as specified in Section 14.3.10.4.2.3
reinforcement shall not exceed 16 longitudinal bar or 14.3.10.4.2.4, the spacing of transverse
diameters throughout the remainder of the reinforcement shall not exceed the least of the
reinforced length. following:
Exceptions: (1) 12 longitudinal bar diameters;
(1) The requirements of this section shall not (2) One-half the least dimension of the
apply to concrete cast in structural steel element; and
pipes or tubes.
(3) 300 mm.
(2) A spiral-welded metal casing of a
Exceptions:
thickness not less than the manufacturer's
standard No. 14 gage (1.72 mm) is (1) The requirements of this section shall not
permitted to provide concrete apply to concrete cast in structural steel
confinement in lieu of the closed ties or pipes or tubes.
spirals. Where used as such, the metal
(2) A spiral-welded metal casing of a
casing shall be protected against possible
thickness not less than manufacturer's
deleterious action due to soil
standard No. 14 gage (1.72 mm) is
constituents, changing water levels or
permitted to provide concrete
other factors indicated by boring records
confinement in lieu of the closed ties or
of site conditions.
spirals. Where used as such, the metal
14.3.10.4.2 Seismic reinforcement in Seismic casing shall be protected against possible
Design Category D through F. For structures deleterious action due to soil
assigned to Seismic Design Category D, E or F, cast- constituents, changing water levels or
in-place deep foundation elements shall be other factors indicated by boring records
reinforced as specified in this section. of site conditions.
Reinforcement shall be provided where required by
14.3.10.4.2.3 Site Classes A through D. For
analysis.
Site Class A, B, C or D sites, transverse
14.3.10.4.2.1 A minimum of four longitudinal confinement reinforcement shall be provided in the
bars, with a minimum longitudinal reinforcement element in accordance with Sections 18.7.5.2,
ratio of 0.005, shall be provided throughout the 18.7.5.3 and 18.7.5.4 of SBC 304 within three
minimum reinforced length of the element as times the least element dimension of the bottom of
defined below starting at the top of the element. the pile cap. A transverse spiral reinforcement ratio
The minimum reinforced length of the element shall of not less than one-half of that required in Section
be taken as the greatest of the following: 18.7.5.4(a) of SBC 304 shall be permitted.
(1) One-half of the element length. 14.3.10.4.2.4 Site Classes E and F. For Site Class
E or F sites, transverse confinement reinforcement
(2) A distance of 3000 mm.
shall be provided in the element in accordance with
(3) Three times the least element dimension. Sections 18.7.5.2, 18.7.5.3 and 18.7.5.4 of SBC 304
within seven times the least element dimension of
(4) The distance from the top of the element
the pile cap and within seven times the least element
to the point where the design cracking
dimension of the interfaces of strata that are hard or
moment determined in accordance with
stiff and strata that are liquefiable or are composed
Section 14.3.10.1 exceeds the required
of soft- to medium-stiff clay.
moment strength determined using the

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14.3.10.5 Belled drilled shafts. Where drilled by mill certifications or two coupon test samples per
shafts are belled at the bottom, the edge thickness 18200 kg of pipe and tube.
of the bell shall not be less than that required for the
14.3.11.3 Reinforcement. For micropiles or
edge of footings. Where the sides of the bell slope
portions thereof grouted inside a temporary or
at an angle less than 60 degrees (1 rad) from the
permanent casing or inside a hole drilled into
horizontal, the effects of vertical shear shall be
bedrock or a hole drilled with grout, the steel pipe
considered.
or tube or steel reinforcement shall be designed to
14.3.10.6 Socketed drilled shafts. Socketed carry at least 40 percent of the design compression
drilled shafts shall have a permanent pipe or tube load. Micropiles or portions thereof grouted in an
casing that extends down to bedrock and an uncased open hole in soil without temporary or permanent
socket drilled into the bedrock, both filled with casing and without suitable means of verifying the
concrete. Socketed drilled shafts shall have hole diameter during grouting shall be designed to
reinforcement or a structural steel core for the carry the entire compression load in the reinforcing
length as indicated by an approved method of steel. Where a steel pipe or tube is used for
analysis. reinforcement, the portion of the grout enclosed
within the pipe is permitted to be included in the
14.3.10.6.1 The depth of the rock socket shall be
determination of the allowable stress in the grout.
sufficient to develop the full load-bearing capacity
of the element with a minimum safety factor of 14.3.11.4 Seismic reinforcement. For structures
two, but the depth shall not be less than the outside assigned to Seismic Design Category C, a
diameter of the pipe or tube casing. The design of permanent steel casing shall be provided from the
the rock socket is permitted to be predicated on the top of the micropile down to the point of zero
sum of the allowable load-bearing pressure on the curvature. For structures assigned to Seismic
bottom of the socket plus bond along the sides of Design Category D, E or F, the micropile shall be
the socket. considered as an alternative system in accordance
with Section 104.11 of SBC 201. The alternative
14.3.10.6.2 Where a structural steel core is used,
system design, supporting documentation and test
the gross cross-sectional area of the core shall not
data shall be submitted to the building official for
exceed 25 percent of the gross area of the drilled
review and approval.
shaft.
14.3.12 Pile caps. Pile caps shall be of reinforced
14.3.11 Micropiles. Micropiles shall be designed
concrete, and shall include all elements to which
and detailed in accordance with Sections 14.3.11.1
vertical deep foundation elements are connected,
through 14.3.11.4.
including grade beams and mats. The soil
14.3.11.1 Construction. Micropiles shall develop immediately below the pile cap shall not be
their load-carrying capacity by means of a bond considered as carrying any vertical load. The tops
zone in soil, bedrock or a combination of soil and of vertical deep foundation elements shall be
bedrock. Micropiles shall be grouted and have embedded not less than 75 mm into pile caps and
either a steel pipe or tube or steel reinforcement at the caps shall extend at least 100 mm beyond the
every section along the length. It shall be permitted edges of the elements. The tops of elements shall
to transition from deformed reinforcing bars to steel be cut or chipped back to sound material before
pipe or tube reinforcement by extending the bars capping.
into the pipe or tube section by at least their
14.3.12.1 Seismic Design Categories C and D.
development length in tension in accordance with
For structures assigned to Seismic Design Category
SBC 304.
C or D concrete deep foundation elements shall be
14.3.11.2 Materials. Reinforcement shall consist connected to the pile cap by embedding the
of deformed reinforcing bars in accordance with element reinforcement or field-placed dowels
ASTM A 615 Grade 60 or 75 or ASTM A 722 anchored in the element into the pile cap for a
Grade 150. distance equal to their development length in
accordance with SBC 304. It shall be permitted to
14.3.11.2.1 The steel pipe or tube shall have a
connect precast prestressed piles to the pile cap by
minimum wall thickness of 4.8 mm. Splices shall
developing the element prestressing strands into the
comply with Section 14.3.7. The steel pipe or tube
pile cap provided the connection is ductile. For
shall have a minimum yield strength of 310 MPa
deformed bars, the development length is the full
and a minimum elongation of 15 percent as shown
development length for compression, or tension in

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the case of uplift, without reduction for excess including overstrength factor in
reinforcement in accordance with Section 25.4.10 accordance with Section 12.4.3 or
of SBC 304. Alternative measures for laterally 12.14.3.2 of SBC 301 or the anchorage
confining concrete and maintaining toughness and shall be capable of developing the full
ductile-like behavior at the top of the element axial, bending and shear nominal
shall be permitted provided the design is such that strength of the element.
any hinging occurs in the confined region.
14.3.12.2.1 Where the vertical lateral force-
14.3.12.1.1 The minimum transverse steel ratio for resisting elements are columns, the pile cap flexural
confinement shall not be less than one-half of that strengths shall exceed the column flexural strength.
required for columns. The connection between batter piles and pile caps
shall be designed to resist the nominal strength of
14.3.12.1.2 For resistance to uplift forces,
the pile acting as a short column. Batter piles and
anchorage of steel pipes, tubes or H-piles to the pile
their connection shall be designed to resist forces
cap shall be made by means other than concrete
and moments that result from the application of
bond to the bare steel section. Concrete-filled steel
seismic load effects including overstrength factor in
pipes or tubes shall have reinforcement of not less
accordance with Section 12.4.3 or 12.14.3.2 of
than 0.01 times the cross-sectional area of the
SBC 301.
concrete fill developed into the cap and extending
into the fill a length equal to two times the required 14.3.13 Grade beams. For structures assigned to
cap embedment, but not less than the development Seismic Design Category D, E or F, grade beams
length in tension of the reinforcement. shall comply with the provisions in Section 18.3.3
14.3.12.2 Seismic Design Category D through F. of SBC 304 for grade beams, except where they are
For structures assigned to Seismic Design Category designed to resist the seismic load effects including
overstrength factor in accordance with Section
D, E or F. deep foundation element resistance to
uplift forces or rotational restraint shall be provided 12.4.3 or 12.14.3.2 of SBC 301.
by anchorage into the pile cap, designed 14.3.14 Seismic ties. For structures assigned to
considering the combined effect of axial forces due Seismic Design Category C, D, E, or F, individual
to uplift and bending moments due to fixity to the deep foundations shall be interconnected by ties.
pile cap. Anchorage shall develop a minimum of 25 Unless it can be demonstrated that equivalent
percent of the strength of the element in tension. restraint is provided by reinforced concrete beams
Anchorage into the pile cap shall comply with the within slabs on grade or reinforced concrete slabs
following: on grade or confinement by competent rock, hard
(1) In the case of uplift, the anchorage shall cohesive soils or very dense granular soils, ties shall
be capable of developing the least of the be capable of carrying, in tension or compression,
following: a force equal to the lesser of the product of the
larger pile cap or column design gravity load times
(i) The nominal tensile strength of the seismic coefficient, SDS, divided by 10, and 25
the longitudinal reinforcement in percent of the smaller pile or column design
a concrete element. gravity load.
(ii) The nominal tensile strength of
a steel element. Exception: In Group R-3 and U occupancies of
(iii) The frictional force developed light-frame construction, deep foundation elements
between the element and the soil supporting foundation walls, isolated interior posts
multiplied by 1.3. detailed so the element is not subject to lateral loads
or exterior decks and patios are not subject to
Exception: The anchorage is permitted to be interconnection where the soils are of adequate
designed to resist the axial tension force resulting stiffness, subject to the approval of the building
from the seismic load effects including official.
overstrength factor in accordance with Section
12.4.3 or 12.14.3.2 of SBC 301. 14.4—Installation
(1) In the case of rotational restraint, the 14.4.1 Deep foundations shall be installed in
anchorage shall be designed to resist the accordance with Section 14.4 . Where a single deep
axial and shear forces, and moments foundation element comprises two or more sections
resulting from the seismic load effects of different materials or different types spliced

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together, each section shall satisfy the applicable grade. The approved agency shall furnish an
conditions of installation. affidavit of compliance to the building official.
14.4.2 Structural integrity. Deep foundation 14.4.4 Location plan. A plan showing the
elements shall be installed in such a manner and location and designation of deep foundation
sequence as to prevent distortion or damage that elements by an identification system shall be filed
may adversely affect the structural integrity of with the building official prior to installation of
adjacent structures or of foundation elements being such elements. Detailed records for elements shall
installed or already in place and as to avoid bear an identification corresponding to that shown
compacting the surrounding soil to the extent that on the plan.
other foundation elements cannot be installed
14.4.5 Preexcavation. The use of jetting,
properly.
augering or other methods of preexcavation shall
14.4.2.1 Compressive strength of precast be subject to the approval of the building official.
concrete piles. A precast concrete pile shall not be Where permitted, preexcavation shall be carried out
driven before the concrete has attained a compressive in the same manner as used for deep foundation
strength of at least 75 percent of the specified elements subject to load tests and in such a manner
compressive strength (f‘ c), but not less than the that will not impair the carrying capacity of the
strength sufficient to withstand handling and driving elements already in place or damage adjacent
forces. structures. Element tips shall be driven below the
preexcavated depth until the required resistance or
14.4.2.2 Casing. Where cast-in-place deep penetration is obtained.
foundation elements are formed through unstable
soils and concrete is placed in an open-drilled hole, 14.4.6 Vibratory driving. Vibratory drivers shall
a casing shall be inserted in the hole prior to placing only be used to install deep foundation elements
the concrete. Where the casing is withdrawn during where the element load capacity is verified by load
concreting, the level of concrete shall be tests in accordance with Section 14.3.4.1.2. The
maintained above the bottom of the casing at a installation of production elements shall be
sufficient height to offset any hydrostatic or lateral controlled according to power consumption, rate of
soil pressure. Driven casings shall be mandrel penetration or other approved means that ensure
driven their full length in contact with the element capacities equal or exceed those of the test
surrounding soil. elements.

14.4.2.3 Driving near uncased concrete. Deep 14.4.7 Heaved elements. Deep foundation
foundation elements shall not be driven within six elements that have heaved during the driving of
element diameters center-to-center in granular soils adjacent elements shall be redriven as necessary to
or within one-half the element length in cohesive develop the required capacity and penetration, or
soils of an uncased element filled with concrete less the capacity of the element shall be verified by load
than 48 hours old unless approved by the building tests in accordance with Section 14.3.4.1.2 .
official. If the concrete surface in any completed 14.4.8 Enlarged base cast-in-place elements.
element rises or drops, the element shall be Enlarged bases for cast-in-place deep foundation
replaced. Driven uncased deep foundation elements elements formed by compacting concrete or by
shall not be installed in soils that could cause heave. driving a precast base shall be formed in or driven
14.4.2.4 Driving near cased concrete. Deep into granular soils. Such elements shall be
foundation elements shall not be driven within four constructed in the same manner as successful
and one-half average diameters of a cased element prototype test elements driven for the project.
filled with concrete less than 24 hours old unless Shafts extending through peat or other organic soil
approved by the building official. Concrete shall shall be encased in a permanent steel casing. Where
not be placed in casings within heave range of a cased shaft is used, the shaft shall be adequately
driving. reinforced to resist column action or the annular
space around the shaft shall be filled sufficiently to
14.4.3 Identification. Deep foundation materials reestablish lateral support by the soil. Where heave
shall be identified for conformity to the specified occurs, the element shall be replaced unless it is
grade with this identity maintained continuously demonstrated that the element is undamaged and
from the point of manufacture to the point of capable of carrying twice its design load.
installation or shall be tested by an approved
agency to determine conformity to the specified

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14.4.9 Hollow-stem augured, cast-in-place withdrawn in a controlled manner with

elements. Where concrete or grout is placed by the grout level maintained at the top of
pumping through a hollow-stem auger, the auger the element to ensure that the grout
shall be permitted to rotate in a clockwise direction completely fills the drill hole. During
during withdrawal. As the auger is withdrawn at a withdrawal of the casing, the grout level
steady rate or in increments not to exceed 300 mm, inside the casing shall be monitored to
concreting or grouting pumping pressures shall be verify that the flow of grout inside the
measured and maintained high enough at all times casing is not obstructed.
to offset hydrostatic and lateral earth pressures.
(2) For a micropile or portion thereof
Concrete or grout volumes shall be measured to
grouted in an open drill hole in soil
ensure that the volume of concrete or grout placed
without temporary casing, the minimum
in each element is equal to or greater than the
design diameter of the drill hole shall be
theoretical volume of the hole created by the auger.
verified by a suitable device during
Where the installation process of any element is
grouting.
interrupted or a loss of concreting or grouting
pressure occurs, the element shall be redrilled to (3) For micropiles designed for end bearing,
1550 mm below the elevation of the tip of the auger a suitable means shall be employed to
when the installation was interrupted or concrete or verify that the bearing surface is properly
grout pressure was lost and reformed. Augured cast- cleaned prior to grouting.
in-place elements shall not be installed within six
(4) Subsequent micropiles shall not be
diameters center to center of an element filled with
drilled near elements that have been
concrete or grout less than 12 hours old, unless
grouted until the grout has had sufficient
approved by the building official. If the concrete or
time to harden.
grout level in any completed element drops due to
installation of an adjacent element, the element (5) Micropiles shall be grouted as soon as
shall be replaced. possible after drilling is completed.
14.4.10 Socketed drilled shafts. The rock socket (6) For micropiles designed with a full-
and pipe or tube casing of socketed drilled shafts length casing, the casing shall be pulled
shall be thoroughly cleaned of foreign materials back to the top of the bond zone and
before filling with concrete. Steel cores shall be reinserted or some other suitable means
bedded in cement grout at the base of the rock employed to assure grout coverage
socket. outside the casing.
14.4.11 Micropiles. Micropile deep foundation 14.4.12 Helical piles. Helical piles shall be
elements shall be permitted to be formed in holes installed to specified embedment depth and
advanced by rotary or percussive drilling methods, torsional resistance criteria as determined by a
with or without casing. The elements shall be registered design professional . The torque applied
grouted with a fluid cement grout. The grout shall during installation shall not exceed the maximum
be pumped through a tremie pipe extending to the allowable installation torque of the helical pile.
bottom of the element until grout of suitable quality 14.4.13 Special inspection. Special inspections in
returns at the top of the element. The following accordance with Sections 1705.7 SBC 201 and
requirements apply to specific installation methods: 1705.8 SBC 201 shall be provided for driven and
(1) For micropiles grouted inside a cast-in-place deep foundation elements,
temporary casing, the reinforcing bars respectively. Special inspections in accordance
shall be inserted prior to withdrawal of with Section 1705.9 SBC 201 shall be provided for
the casing. The casing shall be helical piles.

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CHAPTER 14 DEEP FOUNDATIONS

TABL ES OF CHAPTER 14

Table 14-1—Minimum specified compressive strength  of concrete or grout

DEEP FOUNDATION ELEMENT OR CONDITION SPECIFIED

1. Precast nonprestressed driven piles 28 MPa
2. Socketed drilled shafts 28 MPa
3. Micropiles 28 MPa
4. Precast prestressed driven piles 35 MPa

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Table 14-2 —Allowable streses for materials used in deep foundations elements
a
MATERIAL TYPE AND CONDITION MAXIMUM ALLOWABLE STRESS

1. Concrete or grout in compression

• Cast-in-place with a permanent casing in accordance 0.4 

with Section 14.3.2.7

• Cast-in-place in a pipe, tube, other permanent casing

0.33 
or rock

• Cast-in-place without a permanent casing

0.3 
• Precast nonprestressed
0.33 
• Precast prestressed
0.33  - 0.27 fpc

2. Nonprestressed reinforcement in compression 0.4 fy < 220 MPa

3. Steel in compression
0.5 Fy < 220 MPa
• Cores within concrete-filled i es or tubes
• Pipes, tubes or H-piles, where justified in 0.5 Fy < 220 MPa
accordance with Section 14.3.3.8 .
0.4 Fy < 220 MPa
• Pi es or tubes for micro iles
0.35 Fy < 110 MPa
• Other i es tubes or H- iles
• Helical piles 0.6 Fy < 0.5 Fu

4. Nonprestressed reinforcement in tension

0.6 fy
• Within micropiles
0.5 fy < 165 MPa
• Other conditions
5. Steel in tension

• Pipes, tubes or H-piles, where justified in 0.5 Fy < 220 MPa

accordance with Section 14.3.3.8 .
0.35 Fy < 110 MPa
• Other i es, tubes or H- iles
0.6 Fy < 0.5 Fu
• Helical piles
a

is the specified compressive strength of the concrete or grout; fpc is the compressive stress on the gross concrete
section due to effective prestress forces only; fy is the specified yield strength of reinforcement; Fy is the specified
minimum yield stress of steel; Fu is the specified minimum tensile stress of structural steel.
b
The stresses specified apply to the gross cross-sectional area within the concrete surface. Where a temporary or
permanent casing is used, the inside face of the casing shall be considered the concrete surface.

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