Center for Accelerating Innovation

Bring Your A-GaME* to ABC

Adding Project Value Using Newer Geotechnical Tools

*Advanced Geotechnical Methods in Exploration

Derrick Dasenbrock, P.E. and Benjamin S. Rivers, P.E.

FHWA- Resource Center
ABC-UTC Monthly Webinar | June 17th, 2021
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Outline
• How newer geotechnical tools
provide value to ABC projects
• What geotechnical risk reduction
looks like and what it means for
you: a geotechnology overview Modern methods of site characterization can
provide more accurate and representative design

• Featured A-GaME investigation values, favoring efficient construction

methods Improved geotechnical characterization reduced

pile lengths at an abutment and two pier locations.
• Three brief case histories
• Applications and benefits for
project delivery
• Q&A Session
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Photos by MnDOT
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Motivation
Newer geotechnical site
investigation methods can
help accelerate project
delivery
• Techniques provide fast, Cone Penetration Testing (CPT) minimizes lane closure time

high-quality, digital data

• Geophysical techniques
are well suited to areas
with difficult site access
• All are cost effective
Geophysical methods can be used in tight spaces
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Photos by MnDOT
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Benefits: Risk reduction. Building projects more efficiently.

In addition to cost, time, quality-

Improved geotechnical data leads to right-
sized foundations
• Less conservatism leads to reduced
construction material and time to construct
• Less material delivery/removal
• Appropriate means, methods, and bids
Reduced potential for work stoppages,
changes in plans, contract amendments, and
delay impacting other progress of the work.
CPT operations
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Photos by MnDOT
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Foundation Selection Example

US 10 in Rice, MN Subsurface
Visualization
• Compare traditional SPT
information to CPT and
exploration geophysical
digital data
• A-GaME techniques offer
greater accuracy, data
density, BIM importability,
and superior visualization

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Photos courtesy MnDOT
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Depiction of Subsurface Information

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Plan sheet by MnDOT
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Risk
Examples

“Unforeseen
Conditions”
Are Often
Avoidable

Source: Florida DOT

Highly Variable Rock
Void Under & Pile Refusal
Footing Depths in Karst
Location
Source: Kentucky Transportation Cabinet

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Common Sources of Delays and Cost Escalations:

• Pile overruns
• Higher than expected groundwater
• Other problems with seepage, including those requiring
dewatering, which were identified as notably more costly than
other types of changes
• Misclassified or mischaracterized subgrade, resulting in often
significant quantity revisions related to pavements, earthwork,
and removal and replacement requirements for foundations
• Unanticipated rock during foundation construction
• Mischaracterized rock for drilled shaft construction
Source: NCHRP Synthesis 484 - Influence of Geotechnical
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Investigation and Subsurface Conditions on Claims, Change
Orders, and Overruns
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The A-GaME’s Mission

Mitigate risks to project schedule and budget, and

improve reliability by optimizing geotechnical site
characterization using proven, effective exploration
methods and practices.

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Mainstream Effective Underutilized Investigation Methods

CPT - Cone Penetration Test TDEM - Time-Domain Electromagnetic
SCPT - Seismic Cone Penetration Test FDEM - Frequency-Domain Electromagnetic
ER - Electrical Resistivity VLFEM - Very Low Frequency Electromagnetic
IP - Induced Polarization OTV - Optical Televiewers
SP - Self Potential ACT - Acoustic Televiewers
MWD - Measurement While Drilling GPR - Ground Penetrating Radar
Seismic: Refraction MicroGravity
Seismic: Reflection PMT - Pressuremeter Test
Seismic: FWI - Full Waveform Inversion DMT - Flat Plate Dilatometer Test
Seismic: SASW - Spectral Analysis of Surface Rock Discontinuities from Photogrammetry
Waves Pore-water pressure from Field Piezometers
Seismic: Tomography Suspension Logging
Seismic: Downhole
Seismic: Crosshole

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Mainstream Effective Underutilized Investigation Methods

Electrical Methods (Electrical Resistivity, Induced Polarization, Self Potential)
• Discern contrasting materials and groundwater conditions over large
areas
• Clay, Silts, Sands/Gravel, Voids, Groundwater, geologic features

Source: FHWA-CFL
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Geophysics for final design

Applying geophysics to pile design/layout

Sheet Pile Start Sheet Pile End

DRILLED PILES
DRIVEN PILE SHEET PILE EXTENT

769 770 771 772 773

Depth and location of sheeting & king piles

Source: MnDOT
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Mainstream Effective Underutilized Investigation Methods

Seismic Methods (Surface Waves, Refraction, FWI, Downhole,
Reflection)
• Indicates stratigraphic changes and boundaries over large areas
• Load-displacement behavior
• Seismic hazard susceptibility

Courtesy of Jeff Reid,

Hager-Richter Assoc.
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Seismic Refraction – Top of Bedrock

Source: Jeff Reid, Hager-Richter

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Mainstream Effective Underutilized Investigation Methods

Cone Penetration Testing
(CPTu/SCPTu)
• More reliable
parameters than from
conventional SPT
• Small strata changes
easily discernable
• Pore-water pressure
measurements
• Shear-wave
measurements with
SCPTu
• 3-10 times faster than
conventional drilling

Source: FHWA

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Mainstream Effective Underutilized Investigation Methods

Televiewers – Optical and
Acoustic (OTV/ATV)
• High-resolution, 360o, GIS,
spatially oriented rock drillhole
images
• Continuous
• In-place rock structure and
condition
• Eliminates difficult oriented
coring
• Independent of core quality
Courtesy of Jeff Reid,
Hager-Richter Assoc.
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WFL – Manning Crevice Bridge Idaho

Replacement of 1930s, 250’ long
suspension bridge with asymmetrical,
300’ long suspension Bridge.

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Source: FHWA-WFL
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Source: FHWA-WFL
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Mainstream Effective Underutilized Investigation Methods

Measurement While
Drilling (MWD)
• Continuous
profile
• Discernable
stratigraphic and
material changes
• Rock or Soil
• Standardized in
Europe ISO 22476-
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Source: FHWA
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MWD Equipment Requirements

• Drilling equipment requirements
• Measuring system requirements

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(modified after Jean Lutz S.A., 2020) Slide Courtesy of Anahita Modiriasari, 2020
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Most Basically, MWD provides…

• Continuous quantitative
drilling record
• Means to assess site
variability
• QC/QA value

Source: Harry Moore

(Retired TN DOT)

Courtesy of Liz Smith, Terracon

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Immediate Applications
• Karst Features
• Detecting Boulders, Lenses, Bedrock
Interfaces
• Characterization of Piedmont
Residuum and PWR
• Stratification and material
identification (contrasting)

Source: FHWA
(Gui et al., 2002)
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Case Histories
Real Project Benefits
• A-GaME technologies
are fast
• For a bridge
replacement a Littlefork River bridge replacement project.

boring may take a

week to advance
and a week to
process in the lab
• Several CPT
soundings can be
pushed each day.

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Photo, layout, CPT and Boring Logs by MnDOT
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Whitewater State Park Bridge Replacement

Accelerating Project Delivery

• An unusually heavy rain in
a valley resulted in a flash
flood which completely
removed a bridge in
southeast MN in 2007.
• There was interest in getting
an emergency contract let
quickly to replace the
structure in-kind. Money Creek, MN bridge washout due to flood event.

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Photo by MnDOT
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Whitewater State Park Bridge Replacement

Money Creek, MN. August 27, 2007

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Photo and diagram courtesy MnDOT
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Whitewater State Park Bridge Replacement

CPT soundings were

completed in 1-Day
• The CPT crew used the
1-hour detour route to
access the other side
• Four soundings were
advanced and sent
electronically to the
MnDOT Foundations Unit
• A report was issued
before the crew was
back from the field.

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Photo by MnDOT
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J. Cooke Park Bridge Construction

J. Cooke State Park, MN. Summer, 2012

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Photos by MnDOT
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J. Cooke Park Bridge Fast site characterization with CPT

Construction

CPT Soundings helped

speed the geotechnical
investigation
• The location of top of
rock was important for
bridge design and scour
considerations

Emergency Bridge Construction

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Photos by MnDOT
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Miller Creek Bridge Construction (MnDOT BR 69656)

A new bridge was being

designed to span a trout stream
• Minimally invasive methods
were desired
• Rock outcrops were present Electrical Resistivity

• Electrical resistivity was used

to characterize the bedrock
location
• No borings were advanced

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Photos by MnDOT
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Miller Creek Bridge Construction

Weak Bedrock
Or
Gravelly soil Gabbro
Gabbro
Bedrock Bedrock

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Photos and diagrams by MnDOT
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Miller Creek

Bridge Design
• While a provision for
Gabbro
drilled piles was included Bedrock
in the plans for
unforeseen conditions,
this technique was not
used- saving time and $
• The bridge is supported
on spread footings
Finished bridge on spread footings

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Photos by MnDOT
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Workflow Efficiency within the Digital Era

https://www.geoinstitute
.org/special-
projects/diggs

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Workflow Efficiency - Costs

• CPT rig costs are similar to • Geophysical methods are

SPT rig costs $250k-$750k. especially cost effective
• CPT is operationally faster • Small, portable, minimally
and more efficient (smaller invasive, relatively fast for
crews; less time at sites). data acquisition.
• MWD can be added to • Methods can be
geotechnical drilling systems conducted in-house (with
for about $30k; relatively investment + training)or by
new to US practice consultants across the US.

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Visualization

Improved Communication and Stakeholder Understanding

• Helps convey information quickly

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Composite image by FHWA using MnDOT electrical resistivity output and site photo.
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Foundation Selection Example

US 10 in Rice, MN
• SCPTu - Seismic Cone
Penetration Testing
(soil stiffness)
• Bridges were designed
using spread footings
using a soil subcut with
a geosynthetic front
facing wrap.

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Photos courtesy MnDOT
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Visualization

Information can be used

by many functional areas
• Scoping/Planning
• Pre-Design
• Geotechnical
• Structural Looking at the Rice, MN project through a Hololens at a FHWA event.
• Final Design
• Project Managers
• Construction Managers
• Decision Makers
• Bidders (3D BIM design)

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Photo by FHWA; diagram by MnDOT
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Applications for Alternative Delivery

Design Build & CMGC/CMAR
• Improved data quality allows for
improved design predictions
• Provides support for design concept
alternates and Alternative Technical
Concepts (ATCs)
• Technologies provide fast digital
data with greater coverage and Shallow foundations on MN 610 design build project.
data density
• Digital data is BIM ready
• Allows more favorable LRFD
resistance factors
• Allows evaluation with appropriate
conservatism
• Less $ and time: project acceleration
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Photos by MnDOT
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Conclusions for ABC

• A-GaME techniques accelerate design and
construction
• Involving the geotechnical discipline early in
the ABC project process is important; using
newer technologies can aid with scoping and
provide time-of-construction advantages in
the pre-design and final design phases.
• A-GaME tools are fast, and provide digital
data which is especially useful for data
exchange and inclusion in BIM, digital twins,
and digital as-builts, adding value to all
project stakeholders. MnDOT has been using CPT to
add project value to large
bridge projects since 2001.
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Photos by MnDOT
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Conclusions for ABC

• CPT, MWD, geophysical methods, and ATV/OTV televiewers are
examples of proven techniques that add value and should be
incorporated into ABC projects for improved foundation selection,
design quality, and risk reduction.
• The methods are advantageous in both DBB and alternatively delivery
procurement processes, especially where performance specifications
are used.
• Many DOTs are using these techniques now, to great advantage.

Bridge pile capacity was based on CPT design analysis (Victoria, MN; construction June 2012)

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Photo by MnDOT
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A-GaME ABC Implementation

• Provide support to your

geoprofessional community
• Include language in manuals of
practice, guides, and DB/CMGG
documents
• Ensure requirements and
specifications allow and encourage
the use of current A-GaME practices
• NCHRP Web-Only Doc. 258 Manual on
Subsurface Investigations
• New FHWA GEC information and
AASHTO Manuals are in process

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Photos by MnDOT
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Questions

Derrick Dasenbrock, P.E., D. GE, F. ASCE Benjamin S. Rivers, P.E.

Geotechnical Engineer Geotechnical Engineer
Geotechnical and Hydraulic Engineering Team Geotechnical & Hydraulics Technical Services Team
Federal Highway Administration Resource Federal Highway Administration Resource Center
Center Phone: (404) 562-3926
Phone: 202.923.0972 Cell: (678) 613-2807
derrick.dasenbrock@dot.gov benjamin.rivers@dot.gov
www.fhwa.dot.gov/resourcecenter www.fhwa.dot.gov/resourcecenter

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Benefit of Upfront Investment in Site Investigation

Source: NCHRP Synthesis 484 - Influence of Geotechnical

Investigation and Subsurface Conditions on Claims, Change
Orders, and Overruns (After Figure 1)
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MODOT Approach for Relating Design Reliability to

Variability. 1.0Example Shown: Tip resistance – shafts in clay
Bridges on Minor Roads
0.9 Bridges on Major Roads
Major Bridges (<$100 million)
0.8

Resistance Factor for End Bearing, ϕ qp

Major Bridges (>$100 million)
0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
COV of Mean Undrained Shear Strength, COVsu
Source: Missouri DOT 44