Appendix D - Geotechnical Exploration - Alameda County Government
Advanced Geotechnical Methods for Exploration: The A-GaME
Transcript of Advanced Geotechnical Methods for Exploration: The A-GaME
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Advanced Geotechnical Methods for Exploration:The A-GaME
Bring It!
Benjamin S. Rivers, P.E.FHWA- Resource Center
64Th Alabama Transportation ConferenceFebruary 10th, 2021
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What are the Advanced Geotechnical Methods in Exploration?
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The A-GaME is a toolbox of underutilized subsurface exploration tools that will assist with:• Assessing risk and variability in site
characterization• Optimizing subsurface exploration programs• Maximizing return on investment in project
delivery
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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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Risk
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Source: FHWASource: Ohio DOT
Source: ALDOT
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Risk
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Source: Florida DOT
Source: Kentucky Transportation Cabinet
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Benefit of Upfront Site Investigation Investment
6Source: 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
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COV of Mean Undrained Shear Strength, COVsu
Bridges on Minor RoadsBridges on Major RoadsMajor Bridges (<$100 million)Major Bridges (>$100 million)
Source: Missouri DOT
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Mainstream Effective Underutilized 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
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Site Characterization – Current Practice
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Total Volume Tested or Sampled < 0.01% (typically)
To Scale
Boring/CPT LocationsBorings: Typ. SPT every 5 feet; 18 inch of Sampling
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Site Characterization – Bringing your A-GaME
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Source: Florida DOT
• 6-Mile Section
• 1-day Field Testing
• ½-day Processing
Confirm conditions
Concentrate additional investigation where most valuable
Soft Soils Likely
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Sheet Pile EndSheet Pile Start
769 770 771 772 773
DRIVEN PILE DRILLED PILES
SHEET PILE EXTENT
Depth and location of sheeting & king piles
Geophysics for final designApplying geophysics to pile design/layout
Source: MNDOT
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Seismic Refraction – Top of Bedrock
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Source: Jeff Reid, Hager-Richter
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Mainstream Effective Underutilized 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
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Source: FHWA
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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
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Mainstream Effective Underutilized Methods
Courtesy of Jeff Reid, Hager-Richter Assoc.
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Mainstream Effective Underutilized MethodsMeasurement While Drilling (MWD)• Continuous
profile• Discernable
stratigraphic and material changes
• Rock or Soil• Standardized in
Europe ISO 22476-15
15Source: FHWA
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• Drilling equipment requirements• Measuring system requirements
MWD Equipment Requirements
(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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(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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Continuing Work Needed to…Understand interdependencies while maintaining production:• Between drilling
parameters• Bit types and size• Drilling methods –
Including HSA
Correlate to engineering index parameters
(Reiffsteck et al., 2018)
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Quantitative analysisMeasuring rock strength while drilling shafts socketed into Florida limestone
Examples of MWD Investigations in Geotechnical Engineering
(Rodgers et al., 2018)Slide Courtesy of Anahita Modiriasari, 2020
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A-GaME: What’s Next?In-The-Works• User Groups• Virtual Demos/Workshops/Deep-Dive Webinars (in partnership
with A-GaMEr DOTs, DFI, Industry)• A-GaME Web Platform (in partnership with DFI)
• Archived “A-GaME Winter Webinar Series” Recorded Webinars
• MWD Implementation Document• Geophysics Webtool• Case-Histories/References/Resources• User-Group Links
• DIGGS Implementation (in partnership with GI)• Look Up AASHTO PP 102
• AASHTO Manual on Subsurface Investigation (AASHTO COMP TS1b)
• Influence of COV in LRFD (AASHTO COBS T-15)• Stop-Gap Standards of Practice (collaboration with DFI, GI,
EEGS)
A-GaME e-News New!
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