bring your a-game* to abc

Center for Accelerating Innovation

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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


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

• Featured A-GaME investigation methods

• Three brief case histories• Applications and benefits for

project delivery• Q&A Session

Modern methods of site characterization can provide more accurate and representative design values, favoring efficient construction

Photos by MnDOT

Improved geotechnical characterization reduced pile lengths at an abutment and two pier locations.

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Motivation

Newer geotechnical site investigation methods can help accelerate project delivery• Techniques provide fast,

high-quality, digital data• Geophysical techniques

are well suited to areas with difficult site access

• All are cost effective

Cone Penetration Testing (CPT) minimizes lane closure time

Geophysical methods can be used in tight spaces

Photos by MnDOT3


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.

Photos by MnDOT

CPT operations

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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

Photos courtesy MnDOT5


Depiction of Subsurface Information

Plan sheet by MnDOT6


Risk Examples

“Unforeseen Conditions” Are Often Avoidable

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Source: Florida DOT

Source: Kentucky Transportation Cabinet

Void Under Footing Location

Highly Variable Rock & Pile Refusal Depths in Karst


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 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 MethodsCPT - Cone Penetration Test

SCPT - Seismic Cone Penetration Test

ER - Electrical Resistivity

IP - Induced Polarization

SP - Self Potential

MWD - Measurement While Drilling

Seismic: Refraction

Seismic: Reflection

Seismic: FWI - Full Waveform Inversion

Seismic: SASW - Spectral Analysis of Surface

Waves

Seismic: Tomography

Seismic: Downhole

Seismic: Crosshole

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TDEM - Time-Domain Electromagnetic

FDEM - Frequency-Domain Electromagnetic

VLFEM - Very Low Frequency Electromagnetic

OTV - Optical Televiewers

ACT - Acoustic Televiewers

GPR - Ground Penetrating Radar

MicroGravity

PMT - Pressuremeter Test

DMT - Flat Plate Dilatometer Test

Rock Discontinuities from Photogrammetry

Pore-water pressure from Field Piezometers

Suspension Logging


Mainstream Effective Underutilized Investigation MethodsElectrical 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-CFL11


Sheet Pile EndSheet Pile Start

769 770 771 772 773

DRIVEN PILE DRILLED PILESSHEET PILE EXTENT

Depth and location of sheeting & king piles

Geophysics for final designApplying geophysics to pile design/layout

Source: MnDOT12


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

Mainstream Effective Underutilized Investigation Methods

Courtesy of Jeff Reid, Hager-Richter Assoc. 13


Seismic Refraction – Top of Bedrock

Source: Jeff Reid, Hager-Richter

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Mainstream Effective Underutilized Investigation MethodsCone 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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Televiewers – Optical and Acoustic (OTV/ATV)• High-resolution, 360o, GIS,

spatially oriented rock drillholeimages

• Continuous• In-place rock structure and

condition• Eliminates difficult oriented

coring• Independent of core quality


Courtesy of Jeff Reid, Hager-Richter Assoc. 16


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

WFL – Manning Crevice Bridge Idaho

Source: FHWA-WFL

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Source: FHWA-WFL18



Measurement While Drilling (MWD)• Continuous

profile• Discernable

stratigraphic and material changes

• Rock or Soil• Standardized in

Europe ISO 22476-15

Source: FHWA19


• Drilling equipment requirements• Measuring system requirements

MWD Equipment Requirements

(modified after Jean Lutz S.A., 2020) Slide Courtesy of Anahita Modiriasari, 202020


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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(Gui et al., 2002)

Immediate Applications• Karst Features• Detecting Boulders, Lenses, Bedrock

Interfaces• Characterization of Piedmont

Residuum and PWR• Stratification and material

identification (contrasting)

Source: FHWA

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Case HistoriesReal Project Benefits• A-GaME technologies

are fast• For a bridge

replacement a boring may take a week to advance and a week to process in the lab

• Several CPT soundings can be pushed each day.

Photo, layout, CPT and Boring Logs by MnDOT

Littlefork River bridge replacement project.

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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.

24Photo by MnDOT

Money Creek, MN bridge washout due to flood event.



Photo and diagram courtesy MnDOT

Money Creek, MN. August 27, 2007

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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.

Photo by MnDOT26


J. Cooke Park Bridge Construction

Photos by MnDOT

J. Cooke State Park, MN. Summer, 2012

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J. Cooke Park Bridge Construction

CPT Soundings helped speed the geotechnical investigation• The location of top of

rock was important for bridge design and scour considerations

Photos by MnDOT

Emergency Bridge Construction

Fast site characterization with CPT

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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 was used

to characterize the bedrock location

• No borings were advanced

Photos by MnDOT

Electrical Resistivity

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Miller Creek Bridge Construction

GabbroBedrock

Weak BedrockOr

Gravelly soilGabbroBedrock

Photos and diagrams by MnDOT30


Miller Creek

Bridge Design• While a provision for

drilled piles was included in the plans for unforeseen conditions, this technique was not used- saving time and $

• The bridge is supported on spread footings

GabbroBedrock

Photos by MnDOT

Finished bridge on spread footings

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Workflow Efficiency within the Digital Era

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

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


Workflow Efficiency - Costs

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• CPT rig costs are similar to SPT rig costs $250k-$750k.

• CPT is operationally faster and more efficient (smaller crews; less time at sites).

• MWD can be added to geotechnical drilling systems for about $30k; relatively new to US practice

• Geophysical methods are especially cost effective

• Small, portable, minimally invasive, relatively fast for data acquisition.

• Methods can be conducted in-house (with investment + training)or by consultants across the US.


Visualization

Improved Communication and Stakeholder Understanding• Helps convey information quickly

Composite image by FHWA using MnDOT electrical resistivity output and site photo.34


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.

Photos courtesy MnDOT35


Visualization

Information can be used by many functional areas• Scoping/Planning• Pre-Design• Geotechnical • Structural• Final Design• Project Managers• Construction Managers• Decision Makers• Bidders (3D BIM design)

Photo by FHWA; diagram by MnDOT

Looking at the Rice, MN project through a Hololens at a FHWA event.

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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 data density

• Digital data is BIM ready• Allows more favorable LRFD

resistance factors• Allows evaluation with appropriate

conservatism• Less $ and time: project acceleration

Photos by MnDOT

Shallow foundations on MN 610 design build project.

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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.

Photos by MnDOT38


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.

Photo by MnDOT

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

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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

Photos by MnDOT40


Questions

Derrick Dasenbrock, P.E., D. GE, F. ASCEGeotechnical EngineerGeotechnical and Hydraulic Engineering TeamFederal Highway Administration Resource CenterPhone: [email protected]/resourcecenter

Benjamin S. Rivers, P.E.Geotechnical EngineerGeotechnical & Hydraulics Technical Services TeamFederal Highway Administration Resource CenterPhone: (404) 562-3926Cell: (678) [email protected]/resourcecenter

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mailto:[email protected]

http://www.fhwa.dot.gov/resourcecenter

mailto:[email protected]

http://www.fhwa.dot.gov/resourcecenter


Benefit of Upfront Investment in Site Investigation

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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. Example Shown: Tip resistance – shafts in clay

0.0

0.1

0.2

0.3

0.4

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1.0

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Resis

tanc

e Fac

tor f

or E

nd B

earin

g, ϕ

qp

COV of Mean Undrained Shear Strength, COVsu

Bridges on Minor RoadsBridges on Major RoadsMajor Bridges (<$100 million)Major Bridges (>$100 million)

Source: Missouri DOT

bring your a-game* to abc

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