2-D Liquefaction Evaluation with Q4Mesh · evaluations of earth structures and soil deposits can...

US Army Corpsof EngineersSacramento District

3 August 20053 August 2005 2005 Tri2005 Tri--Service ISCService ISC 11

2005 Tri-Service Infrastructure SystemsConference and Exhibition2005 Tri-Service Infrastructure SystemsConference and Exhibition

-David C. Serafini, M.S., P.E.US Army Corps of Engineers, Sacramento, CA

2-D Liquefaction Evaluationwith Q4Mesh

Presentation OutlinePresentation Outline

� Liquefaction Evaluation Overview� Overview of Quad4m� Overview of Q4Mesh� Liquefaction Evaluation with Q4Mesh� Example Q4Mesh Liquefaction Model

Liquefaction Evaluation OverviewLiquefaction Evaluation Overview

� Two-dimensional seismic response and liquefactionevaluations of earth structures and soil deposits canbe complex and time intensive

� Techniques available for their evaluation range fromsimplified models to advanced constitutive and non-linear models

� Two-dimensional seismic response and liquefactionevaluations of earth structures and soil deposits canbe complex and time intensive

� Techniques available for their evaluation range fromsimplified models to advanced constitutive and non-linear models

Liquefaction Evaluation OverviewLiquefaction Evaluation Overview

� Simplified Models– Simplified Seed and Idriss procedures– 1-D equivalent linear SHAKE type analysis at multiple locations– Evaluations can be made quickly

� Advanced Models– Most accommodate the non-linear behavior of soils– Evaluations are more complex and time intensive

� Equivalent Linear Models– Can be used to approximate the actual nonlinear behavior of the soil– Quad4m (two-dimensional seismic response)

� Simplified Models– Simplified Seed and Idriss procedures– 1-D equivalent linear SHAKE type analysis at multiple locations– Evaluations can be made quickly

� Advanced Models– Most accommodate the non-linear behavior of soils– Evaluations are more complex and time intensive

� Equivalent Linear Models– Can be used to approximate the actual nonlinear behavior of the soil– Quad4m (two-dimensional seismic response)

Overview of Quad4mOverview of Quad4m

� Quad4m (A Computer Program For EvaluatingThe Seismic Response Of Soil Structures)– U.C.Davis, 1993– by Martin Byrd Hudson, I.M.Idriss, and Mohsen

Beikae

� MODIFIED FROM QUAD4, 1973– by I.M. Idriss, J. Lysmer, R. Hwang and H. Bolton

� Quad4m (A Computer Program For EvaluatingThe Seismic Response Of Soil Structures)– U.C.Davis, 1993– by Martin Byrd Hudson, I.M.Idriss, and Mohsen

Beikae

� MODIFIED FROM QUAD4, 1973– by I.M. Idriss, J. Lysmer, R. Hwang and H. Bolton

� The Quad4m analysis numerically models a continuumwith a finite number of elements interconnected attheir common nodes

� The analysis is done exclusively in the time domain,and the response of the soil deposit follows the sameapproximation of nonlinear hysteretic manner that isconventional SHAKE (1-D) analysis when subject toloading

� The Quad4m analysis numerically models a continuumwith a finite number of elements interconnected attheir common nodes

� The analysis is done exclusively in the time domain,and the response of the soil deposit follows the sameapproximation of nonlinear hysteretic manner that isconventional SHAKE (1-D) analysis when subject toloading

� Direct numerical integration by the software is usedto solve an equation of motion for the finite elementmesh to determine the developed:

– Peak Element Shear Stresses (sig-xy, τmax)– Peak Element Shearing Strains (eps, γmax)– Peak Element Principle Stresses (sig-x, sig-y)– Peak Nodal Accelerations (amax)

� Direct numerical integration by the software is usedto solve an equation of motion for the finite elementmesh to determine the developed:

– Peak Element Shear Stresses (sig-xy, τmax)– Peak Element Shearing Strains (eps, γmax)– Peak Element Principle Stresses (sig-x, sig-y)– Peak Nodal Accelerations (amax)

Overview of Q4MeshOverview of Q4Mesh

� The Q4Mesh program is a modification of theWinMesh program to create and analyze Quad4mdata

� Q4mesh was developed by ERDC (EngineeringResearch and Development Center) at WES(Waterways Experimental Station) with someassistance provided from the USACE SacramentoDistrict

� The Q4Mesh program is a modification of theWinMesh program to create and analyze Quad4mdata

� Q4mesh was developed by ERDC (EngineeringResearch and Development Center) at WES(Waterways Experimental Station) with someassistance provided from the USACE SacramentoDistrict

� Q4Mesh can be used to:

– Create the Quad4m finite element mesh

– Interpret the output files from Quad4m and twoadditional user files to conduct a liquefactionevaluation

� Q4Mesh can be used to:

– Create the Quad4m finite element mesh

– Interpret the output files from Quad4m and twoadditional user files to conduct a liquefactionevaluation

� Q4Mesh– (Main Screen)

Additional Input Files for Q4MeshAdditional Input Files for Q4Mesh

Blowcount FileSurface, Phreatic, and Earthquake File

� Basic Liquefaction Procedure Equation

CSR (Cyclic Stress Ratio)CRR (Cyclic Resistance Ratio)Kσ (Stress CorrectionKα (Sloping Ground Correction)MSF (Magnitude Scaling Factor)

� Basic Liquefaction Procedure Equation

CSR (Cyclic Stress Ratio)CRR (Cyclic Resistance Ratio)Kσ (Stress CorrectionKα (Sloping Ground Correction)MSF (Magnitude Scaling Factor)

Example Q4Mesh Liquefaction ModelExample Q4Mesh Liquefaction Model

� Cyclic Resistance Ratio, CRR (Vs1 Data)� Cyclic Resistance Ratio, CRR (Vs1 Data)

� Cyclic Resistance Ratio, CRR (N1,60 Data)� Cyclic Resistance Ratio, CRR (N1,60 Data)

� Stress Correction Factor, Kσ� Stress Correction Factor, Kσ

DefaultKα=1.0

� Magnitude Scaling Factor (MSF)� Magnitude Scaling Factor (MSF)

Embankment Dam on a LiquefiableFoundation (EDOLF)

� Finite Element Mesh� Finite Element Mesh

� Material Properties� Material Properties

� Input Earthquake Record– IMPERIAL VALLEY EARTHQUAKE, CA; OCT 15, 1979– Mw=6.75 at 22km– Amax=0.28g– Filtered Record Low-Pass=20hz– Bracketed Duration ~22 seconds– "ROCK OUTCROP MOTION"

� Input Shear Wave Velocities� Input Shear Wave Velocities

Input Shear Wave Velocity Profile, Vs (ft/s)

Quad4m Analysis ResultsQuad4m Analysis Results

� Peak Nodal Horizontal Acceleration (g)� Peak Nodal Horizontal Acceleration (g)

Peak Horizontal Acceleration (g)

Time to Peak Horizontal Acceleration (seconds)

� Peak Element Induced Shear Stress and Strain� Peak Element Induced Shear Stress and StrainPeak Shear Stress (psf)

Peak Shear Strain (%)

Q4Mesh Analysis and ResultsQ4Mesh Analysis and Results

Example ModelExample Model

Given: γsat =135pcf, γmoist =130pcf for all elements

Total Stress Profile (psf)

Effective Stress Profile (psf)

� Normalized Shear Wave Velocities� Normalized Shear Wave Velocities

Normalized Shear Wave Velocity Profile, Vs1 (ft/s)

� Input Blowcount Data, (N1)60 (blows/ft)� Input Blowcount Data, (N1)60 (blows/ft)

Cyclic Resistance Ratio CRR– Vs1 Values

– (N1)60 Blowcount Values

Cyclic Resistance Ratio CRR– Vs1 Values

– (N1)60 Blowcount Values

� Cyclic Resistance Ratio, CRR– (Calculated from the Vs1 Values)

NCEER Workshop

Andrus and Stokoe (1997)

� Cyclic Resistance Ratio, CRR– (Calculated from the (N1)60 Values)

ICSDEE and ICEGE Conference

Idriss and Boulanger (2004)

Cyclic Stress Ratio CSR– Peak Element Stresses

– Seed and Idriss Simplified Procedure

Cyclic Stress Ratio CSR– Peak Element Stresses

– Seed and Idriss Simplified Procedure

� Cyclic Stress Ratio, CSR– (Calculated from Quad4m Peak Induced Shear Stresses)

� Cyclic Stress Ratio, CSR– (Calculated from Simplified Procedure)

CSR = (CSR = (ττavav//σσ’’vovo) = 0.65() = 0.65(aamaxmax/g)(/g)(σσvovo//σσ’’vovo)rd)rd

Parameters as Defined byParameters as Defined by YoudYoud and Idriss 2001and Idriss 2001

� Stress Correction Factor, Kσ� Stress Correction Factor, Kσ

ICSDEE and ICEGE Conference

Idriss and Boulanger (2004)

Example Q4Mesh Liquefaction ModelExample Q4Mesh Liquefaction Model� Liquefaction Potential Factor of Safety, Vs1 Data� Liquefaction Potential Factor of Safety, Vs1 Data

(CSR-Quad4m, CRR-Vs1) with Kα=1.0

(CSR-Simplified Procedure, CRR-Vs1) with Kα=1.0

Example Q4Mesh Liquefaction ModelExample Q4Mesh Liquefaction Model� Liquefaction Potential Factor of Safety, (N1)60 Data� Liquefaction Potential Factor of Safety, (N1)60 Data

(CSR-Quad4m, CRR-(N1)60 with Kα=1.0

(CSR-Simplified Procedure, CRR-(N1)60 with Kα=1.0

Concluding RemarksConcluding Remarks

� Q4Mesh enables the ability to conduct 2-Dliquefaction potential evaluations from Quad4m outputdata

� Quad4m and Q4Mesh can be used as a first stepevaluation before more advanced models areimplemented

� User experience and correct model generation isimportant when evaluating the Quad4m output files

� Q4Mesh enables the ability to conduct 2-Dliquefaction potential evaluations from Quad4m outputdata

� Quad4m and Q4Mesh can be used as a first stepevaluation before more advanced models areimplemented

� User experience and correct model generation isimportant when evaluating the Quad4m output files

ReferencesReferences� Idriss, I. M., and Boulanger, R. W. (2004). "Semi-empirical procedures for

evaluating liquefaction potential during earthquakes." Proc., 11thInternational Conference on Soil Dynamics and Earthquake Engineering, and3rd International Conference on Earthquake Geotechnical Engineering, D.Doolin et al., eds., Stallion Press, Vol. 1, 32-56.

� Boulanger, R. W. and Idriss, I. M. (2004). "State normalization of penetrationresistances and the effect of overburden stress on liquefaction resistance."Proc., 11th International Conference on Soil Dynamics and EarthquakeEngineering, and 3rd International Conference on Earthquake GeotechnicalEngineering, D. Doolin et al., eds., Stallion Press, Vol. 2, 484-491.

� Youd, T. L. and Idriss, I. M. (2001). "Liquefaction resistance of soils:summary report from the 1996 NCEER and 1998 NCEER/NSF Workshops onEvaluation of Liquefaction Resistance of Soils," Journal of Geotechnical andGeoenvironmental Engineering, ASCE, Vol. 127, No. 4, pp. 297-313.

� Idriss, I. M., and Boulanger, R. W. (2004). "Semi-empirical procedures forevaluating liquefaction potential during earthquakes." Proc., 11thInternational Conference on Soil Dynamics and Earthquake Engineering, and3rd International Conference on Earthquake Geotechnical Engineering, D.Doolin et al., eds., Stallion Press, Vol. 1, 32-56.

� Boulanger, R. W. and Idriss, I. M. (2004). "State normalization of penetrationresistances and the effect of overburden stress on liquefaction resistance."Proc., 11th International Conference on Soil Dynamics and EarthquakeEngineering, and 3rd International Conference on Earthquake GeotechnicalEngineering, D. Doolin et al., eds., Stallion Press, Vol. 2, 484-491.

� Youd, T. L. and Idriss, I. M. (2001). "Liquefaction resistance of soils:summary report from the 1996 NCEER and 1998 NCEER/NSF Workshops onEvaluation of Liquefaction Resistance of Soils," Journal of Geotechnical andGeoenvironmental Engineering, ASCE, Vol. 127, No. 4, pp. 297-313.

Thank you!

2005 Tri-Service Infrastructure SystemsConference and Exhibition2005 Tri-Service Infrastructure SystemsConference and Exhibition

David C. Serafini, M.S., P.E.US Army Corps of Engineers, Sacramento, CA1325 J. StreetSacramento, CA 95814(916) 557-7584david.c.serafini@hotmail.com

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2-D Liquefaction Evaluation with Q4Mesh · evaluations of earth structures and soil deposits can...

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