2-D Liquefaction Evaluation with Q4Mesh -David C. Serafini, M.S., - - PowerPoint PPT Presentation

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2-D Liquefaction Evaluation with Q4Mesh -David C. Serafini, M.S., - - PowerPoint PPT Presentation

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2005 Tri-Service Infrastructure Systems 2005 Tri-Service Infrastructure Systems US Army Corps Conference and Exhibition Conference and Exhibition of Engineers Sacramento District 2-D Liquefaction Evaluation with Q4Mesh -David C. Serafini,

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2005 Tri-Service Infrastructure Systems Conference and Exhibition 2005 Tri-Service Infrastructure Systems Conference and Exhibition

  • David C. Serafini, M.S., P.E.

US Army Corps of Engineers, Sacramento, CA

2-D Liquefaction Evaluation with Q4Mesh

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Presentation Outline Presentation Outline

I

Liquefaction Evaluation Overview

I

Overview of Quad4m

I

Overview of Q4Mesh

I

Liquefaction Evaluation with Q4Mesh

I

Example Q4Mesh Liquefaction Model

I

Liquefaction Evaluation Overview

I

Overview of Quad4m

I

Overview of Q4Mesh

I

Liquefaction Evaluation with Q4Mesh

I

Example Q4Mesh Liquefaction Model

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Liquefaction Evaluation Overview Liquefaction Evaluation Overview

I Two-dimensional seismic response and liquefaction

evaluations of earth structures and soil deposits can be complex and time intensive

I Techniques available for their evaluation range from

simplified models to advanced constitutive and non- linear models

I Two-dimensional seismic response and liquefaction

evaluations of earth structures and soil deposits can be complex and time intensive

I Techniques available for their evaluation range from

simplified models to advanced constitutive and non- linear models

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Liquefaction Evaluation Overview Liquefaction Evaluation Overview

I Simplified Models

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

I Advanced Models

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

I Equivalent Linear Models

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

I Simplified Models

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

I Advanced Models

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

I Equivalent Linear Models

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

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Overview of Quad4m Overview of Quad4m

I Quad4m (A Computer Program For Evaluating

The Seismic Response Of Soil Structures)

– U.C.Davis, 1993 – by Martin Byrd Hudson, I.M.Idriss, and Mohsen Beikae

I MODIFIED FROM QUAD4, 1973

– by I.M. Idriss, J. Lysmer, R. Hwang and H. Bolton Seed

I Quad4m (A Computer Program For Evaluating

The Seismic Response Of Soil Structures)

– U.C.Davis, 1993 – by Martin Byrd Hudson, I.M.Idriss, and Mohsen Beikae

I MODIFIED FROM QUAD4, 1973

– by I.M. Idriss, J. Lysmer, R. Hwang and H. Bolton Seed

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Overview of Quad4m Overview of Quad4m

I The Quad4m analysis numerically models a continuum

with a finite number of elements interconnected at their common nodes

I The analysis is done exclusively in the time domain,

and the response of the soil deposit follows the same approximation of nonlinear hysteretic manner that is conventional SHAKE (1-D) analysis when subject to loading

I The Quad4m analysis numerically models a continuum

with a finite number of elements interconnected at their common nodes

I The analysis is done exclusively in the time domain,

and the response of the soil deposit follows the same approximation of nonlinear hysteretic manner that is conventional SHAKE (1-D) analysis when subject to loading

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Overview of Quad4m Overview of Quad4m

I Direct numerical integration by the software is used

to solve an equation of motion for the finite element mesh 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)

I Direct numerical integration by the software is used

to solve an equation of motion for the finite element mesh 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)

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Overview of Q4Mesh Overview of Q4Mesh

I The Q4Mesh program is a modification of the

WinMesh program to create and analyze Quad4m data

I Q4mesh was developed by ERDC (Engineering

Research and Development Center) at WES (Waterways Experimental Station) with some assistance provided from the USACE Sacramento District

I The Q4Mesh program is a modification of the

WinMesh program to create and analyze Quad4m data

I Q4mesh was developed by ERDC (Engineering

Research and Development Center) at WES (Waterways Experimental Station) with some assistance provided from the USACE Sacramento District

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Overview of Q4Mesh Overview of Q4Mesh

I Q4Mesh can be used to:

– Create the Quad4m finite element mesh – Interpret the output files from Quad4m and two additional user files to conduct a liquefaction evaluation

I Q4Mesh can be used to:

– Create the Quad4m finite element mesh – Interpret the output files from Quad4m and two additional user files to conduct a liquefaction evaluation

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Overview of Q4Mesh Overview of Q4Mesh

I Q4Mesh

– (Main Screen)

I Q4Mesh

– (Main Screen)

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Overview of Q4Mesh Overview of Q4Mesh

Additional Input Files for Q4Mesh Additional Input Files for Q4Mesh

1) 3) 4) 5) 2)

Blowcount File Surface, Phreatic, and Earthquake File

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Overview of Q4Mesh Overview of Q4Mesh

I Basic Liquefaction Procedure Equation

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

I Basic Liquefaction Procedure Equation

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

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

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

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

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

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Stress Correction Factor, Kσ I Stress Correction Factor, Kσ

Default Kα=1.0

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Magnitude Scaling Factor (MSF) I Magnitude Scaling Factor (MSF)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

Embankment Dam on a Liquefiable Foundation (EDOLF) Embankment Dam on a Liquefiable Foundation (EDOLF)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Finite Element Mesh I Finite Element Mesh

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Material Properties I Material Properties

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I 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"

I 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"

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Input Shear Wave Velocities I Input Shear Wave Velocities

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

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

Quad4m Analysis Results Quad4m Analysis Results

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Peak Nodal Horizontal Acceleration (g) I Peak Nodal Horizontal Acceleration (g)

Peak Horizontal Acceleration (g) Time to Peak Horizontal Acceleration (seconds)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Peak Element Induced Shear Stress and Strain I Peak Element Induced Shear Stress and Strain

Peak Shear Stress (psf) Peak Shear Strain (%)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

Q4Mesh Analysis and Results Q4Mesh Analysis and Results

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Example Model Example Model

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

Total Stress Profile (psf) Effective Stress Profile (psf)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Normalized Shear Wave Velocities I Normalized Shear Wave Velocities

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

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

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

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

Cyclic Resistance Ratio CRR

– Vs1 Values – (N1)60 Blowcount Values

Cyclic Resistance Ratio CRR

– Vs1 Values – (N1)60 Blowcount Values

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Cyclic Resistance Ratio, CRR

– (Calculated from the Vs1 Values)

I Cyclic Resistance Ratio, CRR

– (Calculated from the Vs1 Values)

NCEER Workshop Andrus and Stokoe (1997)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Cyclic Resistance Ratio, CRR

– (Calculated from the (N1)60 Values)

I Cyclic Resistance Ratio, CRR

– (Calculated from the (N1)60 Values)

ICSDEE and ICEGE Conference Idriss and Boulanger (2004)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

Cyclic Stress Ratio CSR

– Peak Element Stresses – Seed and Idriss Simplified Procedure

Cyclic Stress Ratio CSR

– Peak Element Stresses – Seed and Idriss Simplified Procedure

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Cyclic Stress Ratio, CSR

– (Calculated from Quad4m Peak Induced Shear Stresses)

I Cyclic Stress Ratio, CSR

– (Calculated from Quad4m Peak Induced Shear Stresses)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Cyclic Stress Ratio, CSR

– (Calculated from Simplified Procedure)

I Cyclic Stress Ratio, CSR

– (Calculated from Simplified Procedure) CSR = ( CSR = (τ τav

av/

/σ σ’ ’vo

vo) = 0.65(

) = 0.65(a amax

max/g)(

/g)(σ σvo

vo/

/σ σ’ ’vo

vo)rd

)rd Parameters as Defined by Parameters as Defined by Youd Youd and Idriss 2001 and Idriss 2001

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Stress Correction Factor, Kσ I Stress Correction Factor, Kσ

ICSDEE and ICEGE Conference Idriss and Boulanger (2004)

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Liquefaction Potential Factor of Safety, Vs1 Data I Liquefaction Potential Factor of Safety, Vs1 Data

(CSR-Quad4m, CRR-Vs1) with Kα=1.0 (CSR-Simplified Procedure, CRR-Vs1) with Kα=1.0

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Example Q4Mesh Liquefaction Model Example Q4Mesh Liquefaction Model

I Liquefaction Potential Factor of Safety, (N1)60 Data I 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

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Concluding Remarks Concluding Remarks

I Q4Mesh enables the ability to conduct 2-D

liquefaction potential evaluations from Quad4m output data

I Quad4m and Q4Mesh can be used as a first step

evaluation before more advanced models are implemented

I User experience and correct model generation is

important when evaluating the Quad4m output files

I Q4Mesh enables the ability to conduct 2-D

liquefaction potential evaluations from Quad4m output data

I Quad4m and Q4Mesh can be used as a first step

evaluation before more advanced models are implemented

I User experience and correct model generation is

important when evaluating the Quad4m output files

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References References

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

evaluating liquefaction potential during earthquakes." Proc., 11th International Conference on Soil Dynamics and Earthquake Engineering, and 3rd International Conference on Earthquake Geotechnical Engineering, D. Doolin et al., eds., Stallion Press, Vol. 1, 32-56.

I Boulanger, R. W. and Idriss, I. M. (2004). "State normalization of penetration

resistances and the effect of overburden stress on liquefaction resistance." Proc., 11th International Conference on Soil Dynamics and Earthquake Engineering, and 3rd International Conference on Earthquake Geotechnical Engineering, D. Doolin et al., eds., Stallion Press, Vol. 2, 484-491.

I Youd, T. L. and Idriss, I. M. (2001). "Liquefaction resistance of soils:

summary report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils," Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 127, No. 4, pp. 297-313.

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

evaluating liquefaction potential during earthquakes." Proc., 11th International Conference on Soil Dynamics and Earthquake Engineering, and 3rd International Conference on Earthquake Geotechnical Engineering, D. Doolin et al., eds., Stallion Press, Vol. 1, 32-56.

I Boulanger, R. W. and Idriss, I. M. (2004). "State normalization of penetration

resistances and the effect of overburden stress on liquefaction resistance." Proc., 11th International Conference on Soil Dynamics and Earthquake Engineering, and 3rd International Conference on Earthquake Geotechnical Engineering, D. Doolin et al., eds., Stallion Press, Vol. 2, 484-491.

I Youd, T. L. and Idriss, I. M. (2001). "Liquefaction resistance of soils:

summary report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils," Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 127, No. 4, pp. 297-313.

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Thank you!

2005 Tri-Service Infrastructure Systems Conference and Exhibition 2005 Tri-Service Infrastructure Systems Conference and Exhibition

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David C. Serafini, M.S., P.E.

US Army Corps of Engineers, Sacramento, CA

1325 J. Street Sacramento, CA 95814 (916) 557-7584 david.c.serafini@hotmail.com

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