Summary of Geotechnical Investigations and Site Conditions

U.S. Department of EnergyOffice of Civilian Radioactive Waste Management

Summary of Geotechnical Investigations and Site Conditions at Yucca Mountain

Presented to:Nuclear Waste Technical Review BoardJoint Meeting of the Natural System and Engineered System Panels

Presented by:Ivan G. WongSenior Consulting SeismologistURS Corporation

February 24, 2003Las Vegas, Nevada

BSC Presentations_NWTRB_YMWong_02/24/03 2

Objectives

• To provide the necessary geological, geophysical, and geotechnical data for development of– Preclosure seismic design and postclosure performance

assessment earthquake ground motions– Foundation design recommendations for the Surface

Facilities

• Characterization of the subsurface lithology andstratigraphy, seismic wave velocity structure, and static and dynamic material properties of the repository block and Surface Facilities are required


Required for Seismic Design• S-wave and P-wave velocity models at surface

facilities and repository block• Lithology and stratigraphy beneath surface facilities

and repository block• Nonlinear dynamic material properties – shear

modulus reduction and damping for fill, alluvium, and tuff

• Densities

Required for Foundation Design• Densities, shear strength, and compressibility

characteristics of the alluvium, shallow tuff, and potential source of engineered fill


Design of Geotechnical Program Above Emplacement Area

• Program focused on upper block emplacement area• Limited borehole availability and difficult access due

to rough topography• Relatively uniform geology across repository block• Program consisted of shallow and deep Spectral-

Analysis-of-Surface-Waves (SASW) surveys supplemented by limited shallow borehole measurements


Emplacement Area (Upper Block)Investigated in Geotechnical Program


Design of Geotechnical Program atSurface Facilities

• Number, locations, and classifications of individual facilities at Surface Facilities Area not finalized at the time of program design

• Because of the large area to be investigated and the lack of specific building sites, the program was designed to utilize deep and shallow boreholes supplemented by extensive SASW surveys

Surface Facilities Site Characterization Area



Vs Profiles on Top of Yucca Mountain

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D-1D-2D-3D-4D-5D-6 Profile 1D-6 Profile 2D-7D-8D-9D-10D-11 Profile 1D-11 Profile 2D-11 Profile 3S-1S-2S-3S-4S-5S-6S-7S-8S-9S-10S-11S-12C-1C-2 Profile 1C-2 Profile 2C-2 Profile 3C-3C-4C-5C-6 Profile 1C-6 Profile 2C-6 Profile 3C-7

0 1000 2000 3000 4000 5000 6000 7000Seismic Velocity, feet per second

Vs = Shear Wave Velocity


Comparison of Vertical Seismic Profiling Vp Profiles

VP = Compressional Wave Velocity


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SASW + DownholeMeanMedian16th Percentile84th Percentile


VSPBase Case Profile #1Base Case Profile #2

T-2 to T-5SASWin ESF

Vs Basecase Profiles


Location of Boreholes and Test Pits


Qal = Quaternary AlluviumTpki = Tuff XTpc__ = Units of Tiva Canyon Tuff

Surface Facilities Geologic Cross-Section Looking South

Test Pit # 1

From BSC (2002)


NOTES:For definition of terms see backup slides


Borehole RF #13 Downhole VP and VSMeasurements and Generalized Lithology

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Vp (GEOVision)Vs (GEOVision)Vp (Redpath)Vs (Redpath)


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Tpki

Tpbt5

Tpcrn

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Fill

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Tpcpln

Qal = Quaternary AlluviumTpc__ = Units of Tiva Canyon Tuff


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0 1500 3000 4500 6000 7500 9000 10500 12000Shear-Wave Velocity, feet per second

Fill

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VS Suspension Data at Borehole RF #13


SASW VS Measurements in Tuff at Surface Facilities


VS Profiles at Surface Facilities


Probabilistic Representation ofVelocity Models

• Objective: Characterize variability in shear-wave velocity profiles at one location– Borehole to borehole variation within one location

(repository block or waste-handling building)– Vertical variation at one borehole (central tendency,

roughness)

• Purpose: Generate artificial velocity profiles that are statistically similar to observed profiles for use in site-response calculations


Samples Tested

• 24 intact tuff specimens from Surface Facilities• 5 reconstituted alluvial specimen from Surface

Facilities Area• 10 compacted granular fill specimens from material

from Fran Ridge Borrow Area• 5 intact tuff specimens from north portal area of

Exploratory Study Facility (ESF)


Variation in Normalized Shear Modulus and Damping Ratio with Shearing Strain (Tuff)

0.0001 0.001 0.01 0.1 1Shearing Strain (%)

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Base Case # 1Base Case #2Tpcrn - 2000 SamplesTpcpul - 2000 SamplesTpcpmn - 2000 SamplesTpcpmn - 1999 Samples

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Tpki "Tuff X" - 2000 SamplesTpki "Tuff X" - 1999 Samples


0.0001 0.001 0.01 0.1 1Shearing Strain (Percent)

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2000 Test Results - Qal1999 Test Results - QalMedian #1Median #2

Variation in Normalized Shear Modulus and Damping Ratio with Shearing Strain (Alluvium)


Summary• Based on the seismic velocity surveys (SASW,

vertical seismic profile (VSP), and shallow downhole) performed above the emplacement area and in the ESF, two basecase velocity profiles have been developed for VS and VP for the repository block

• Based on SASW, downhole, and suspension data, single basecase profiles for VS and VP have been developed for the surface facilities

• A probabilistic representation of the velocity profiles has been developed to characterize the variability at the emplacement area and WHB


Summary (Continued)

• Shear modulus reduction and damping curves have been developed for the tuff and alluvium

• Uncertainties in the velocity structure and dynamic properties in the emplacement area and to a lesser extent, the WHB are being incorporated into the design ground motions to a greater degree than if more site-specific data were available. This results in more conservative ground motions


Backup


Soil Terms and Acronyms• Abbreviations and Terms used for soil units (SU)

SUx = Soil unit, number (x)

GM = Silty-gravel [gravel with significant sand/silt content]GP = Poorly-graded gravel with a small amount of sand/silt GP-GM = Poorly-graded gravel with a small to significant

amount of sand and silt

scb = Soil includes cobbles and boulderssc = Soil includes cobbless = Soil

Fill = Undefined soil type, manually placed Spoil pile = Excavated soil/rock pile

BSC (Bechtel SAIC Company) 2002. Geotechnical Data for a Potential Waste Handling Building and for Ground Motion Analyses for the Yucca Mountain Site Characterization Project. ANL-MGR-GE-000003 REV 00. Las Vegas, Nevada: Bechtel SAIC Company. ACC: MOL.20021004.0078.


D’C’

D’C’

B’ B’

A’ A’A A’C D

B B’C D

0 5 10 20km

Geologic Map of the Yucca Mountain Region


Lithostratigraphy


STATIC LAB TESTS – WHB &BORROW SITE

(URS)

DOWNHOLE SEISMIC – WHB16 boreholes

(Redpath)

DOWNHOLE SEISMIC – MTN8 boreholes(Redpath)

DYNAMIC LAB TESTS –WHB, MTN, & BORROW SITE

(Stokoe)

GEOPHYSICAL LOGS17 boreholes

(Schulmberger)

SUSPENSION SEISMIC - WHB16 boreholes(GeoVision)

SASW – MTN33 surveys(Stokoe)

SASW – TUNNEL5 surveys(Stokoe)

SASW – WHB37 surveys(Stokoe)

BOREHOLE/TEST PITLOGS – WHB

(USBR)

GEOTECH DATA REPORTPI: Mike Luebbers, Ivan Wong, Rob LungRM: Cliff Howard

Seismic TopicalReport #2

Seismic DesignMethodology

Seismic Topical Report #1PSHA Methodology

Probabilistic FaultDisplacement andGround Motion

Analyses (Point A)

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Receive data via input transmittal 1-Oct-01

2

Flow Chart for Geotechnical Investigations


SEISMIC DESIGN INPUTS REPORTREV 01PI: Ivan Wong, Patricia ThomasRM: Richard Quittmeyer

TOPICAL REPORT #3REV 00PI: Carl Stepp, Ivan WongRM: Richard Quittmeyer

SOILS REPORTPI: Mike LuebbersRM: Cliff Howard

DESIGN OF WASTEPACKAGE & SubD/EBS

DESIGN OF WHB – SFD(Surface Facilities Design)

CORRELATIONANALYSIS – WHB

(Toro)

CORRELATIONANALYSIS – MTN

(Toro)

VELOCITY BASECASE –WHB

(Silva/Wong)

VELOCITY BASECASE(S)– MTN

(Silva/Wong)

DYNAMIC MATERIALPROPERTIES(Silva/Pyke)

GROUND MOTIONANALYSES for Pts B,C, & D

(Silva)1

Calculate UHS(Toro)

Calculate DEAs(Toro)

2Develop Vertical Control

Motions for Point A(Silva)

Finalize control motionapproach (1 or 2 DEAs)

(Silva)

Flow Chart for Geotechnical Investigations(Continued)


Spectral Analysis of Surface Waves Surveys in the N-S Drift


Downhole VS Measurements in the Surface Facilities Area

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RF#13RF#14RF#15RF#16RF#17RF#18RF#19RF#20RF#21RF#22RF#23RF#24RF#25RF#26RF#28RF#29



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Downhole MedianSASW Median

Comparison of Spectral Analysis of Surface Waves and Downhole Measurements at Surface Facilities,

Soil Without Fill, South of the Fault


Shear-Wave Velocities for Downhole, Suspension and Spectral Analysis of Surface Waves Measurements at Surface

Facilities, South of the Fault, Tuff

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Downhole MedianSASW MedianSuspension Median


Dynamic Laboratory TestingTo provide dynamic property data to aid in the development of material/site specific normalized shear modulus and hysteretic damping versus shearing strain curves for use in seismic analyses.

Gmax

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Shearing Strain, γ , %

G

Dmin

D, %12

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Shearing Strain, γ , %

Gmax

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1x10-4 1x10-3 1x10-2 1x10-1 1x100

Shearing Strain (%)

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UTA-23-UUTA-23-VUTA-23-WUTA-23-Y

Variation in Normalized Shear Modulus and Damping Ratio with Shearing Strain (Fill)


Formulation

=

Actually, formulation workswith ln(Velocity), not with velocity as shown here

Ti is the thickness of layer i


Specimens UTA-23-A to 23-J

Documents

Summary of Geotechnical Investigations and Site Conditions