seismic response of stratified sites and implications for ... · ahmed elgamal, professor, ucsd....
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San Diego Regional Chapter
Workshop: Liquefaction Evaluation, Mapping, Simulation and Mitigation September 12, 2014
Geoffrey R. Martin, Professor Emeritus, USC&
Ahmed Elgamal, Professor, UCSD
Seismic Response of Stratified Sites and Implications for Foundation Systems
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Representative Stratified Site: Liquefaction Design Issues
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Bridges – Lateral Spread Design Issues
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Stratified Sites: Variability of Triggering Factors of Safety
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Historical DevelopmentsLaboratory Simulation of Seismic Loading
Cyclic Simple Shear Stress Induced by Seismic Loading
Seed et al. / Finn et al.1960’s / 1970’s
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Historical Developments
Laboratory Test Results
Representative/Cyclic TriaxialTest Results (Finn, 1971)
Representative/Cyclic Simple Shear Test Results (Peacock and Seed, 1968)
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Stress Controlled Cyclic Simple Shear Tests
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Constant Volume Strain Controlled Cyclic Simple Shear Tests
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Laboratory Tests: Silty Sand – Transitional Behavior
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Effective Stress Site Response Analysis
Finn et.al 1978 : DESRA
Matasovic 1993 : D-MOD
Martin/Qui 1998 : DESRA-MUSC
Pyke 2000 : TESS
Elgamal et.al 2002 : Cyclic/Opensees
Hashash 2009 : DEEPSOIL
Boulanger et.al 2010 : PM4 Sand Model/FLAC
Byrne/Beaty 2011 : UBC Sand/FLAC and PLAXIS
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Plasticity Based Constitutive Models
PM4 Sand Model Boulanger et. al.
Cyclic 1D ModelElgamal et. al.
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Fundamentals Constitutive Model – 1D Effective Stress Site Response Analyses
Computer Programs: DESRA (Lee and Finn, 1978)DESRAMUSC (Qui, 1998)
Objectives:
Time histories of pore water pressure increases in multi layer sites
Determine critical layer for lateral spread analyses
Determine effect of pore water pressure increases on ground surface response
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DESRA Constitutive Model Fundamentals –Cyclic Strain Based Volume Change Parameters
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Fundamentals Constitutive Model – 1D Effective Stress Site Response Analyses
Input Data for Practical Applications Nonlinear initial τ/γ backbone
curve matched to G/Gmax curve
Masing criteria used tosimulate hysteretic behavior
Strain hardening suppressed
Backbone curve degraded as a function of pore water pressure increase
Representative elastic rebound curves chosen based on N1 values
Volume change parameters (simplified to 2) chosen based on N1 values
Volume change/rebound parameters adjusted to match field liquefaction strength curves
Pore water pressure dissipation/re-distribution during analyses a program option
(Note 𝑚𝑚𝑣𝑣 = 1�𝐸𝐸𝑟𝑟
)
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Fundamentals Constitutive Model – 1D Effective Stress Site Response Analyses
Example illustrating effects of pore water pressure redistribution and sequential liquefaction
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Stratified Soil Condition at a Bridge Site
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Fundamentals Constitutive Model – 1D Effective Stress Site Response Analyses
Example illustrating effects of large strain liquefaction
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8th WCEE, 198418
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Elgamal et al. 1989
Site Liquefaction (Soil Liquefaction)
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Adalier and Elgamal 1992
Site Liquefaction (Soil Liquefaction)
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Kokusho et al. (2000)
Site Liquefaction (Soil Liquefaction)
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Project VELACS (1993)
(Verification of Liquefaction Analyses by Centrifuge
Studies)
Simple Configurations
Few sensors
Bonnie Silt!
Site Liquefaction (Soil Liquefaction)
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Fiegel and Kutter 1994
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Boulanger et al. and Kutter et al. 2001-2004
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Figure 4. Geotechnical cross-section for WLA developed from CPT data.
Steidl and Seale 2010
Site Stratification (Wildlife Array, Imperial County, CA)
Youd and Holzer 1994 25
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Cyclic mobility at large shear strain (Zeghal and Elgamal 1994)
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Cyclic mobility at large shear strain (Zeghal and Elgamal 1994)
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Soil Constitutive ModelMulti-yield surface plasticity model (based on Prevost 1985)
Incorporating dilatancy and cyclic mobility effects
Conical yield surfaces for granularsoils (Prevost 1985; Elgamal et al.2003; Yang and Elgamal 2008)
Shear stress-strain and effectivestress path under undrained shearloading condition (Parra 1996, Yang2000, Yang and Elgamal 2002)
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Permeability is a critical parameter for the estimation of liquefaction-induced lateral deformations
Yang, Z. and Elgamal, A. “Influence of Permeability on Liquefaction-Induced Shear Deformation,” Journal of Engineering Mechanics, ASCE, 128, 7, July 2002.
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Before After
1m of Lateral Spreading ( > 3 pile diameters)
NIED, Tsukuba, Japan
Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)
Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
NIED, Tsukuba, Japan
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Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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Side-view shear
Plan-view shear
around the pile (depends on pile
stiffness)
Shaking Table Tests: US-Japan Research (UCSD, NSF, NIED, PEER, CALTRANS)5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe
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OpenSees FE Model
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5.0
LVDT Accelerometer Pore pressure sensor Strain gage
3.8 m 3.9 m 3.9 m----------------------------------- 11.6 m ------------------------------
2 degrees
5.0
mInstrumentation Layout/Experimental Data
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
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Ground Lateral Displacement (m)
Depth
(m)
Free-Field Displacement Profile at 10 seconds
NumericalExperimental
Recorded and computed free-field displacement profile at 10 seconds
k= 5 e-5 m/sec
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
0.5
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1.5
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2.5
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Ground Lateral Displacement (m)
Depth
(m)
Free-Field Displacement Profile at 10 seconds
k = 5 e -5 m/sk = 5 e -4 m/sk = 5 e -3 m/sk = 5 e -2 m/s
Influence of permeability on free-field displacement profile at 10 seconds
1 2 34
1 2 34
(undrained) k1<k2<k3<k4 (drained)
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Influence of permeability on stiff pile moment profile at 10 seconds
-20 0 20 40 60 80 100 120 140 160 180
-1
0
1
2
3
4
5
Moment (kN·m)
Depth
(m)
Stiff Pile Moment Profile at 10 seconds
k = 5 e -5 m/sk = 5 e -4 m/sk = 5 e -3 m/sk = 5 e -2 m/s
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Ground Lateral Displacement (m)
Depth
(m)
Free-Field Displacement Profile at 10 seconds
k = 5 e -5 m/sk = 5 e -4 m/sk = 5 e -3 m/sk = 5 e -2 m/s
1
1
2
234
34
Free-Field Displacement
1 2 34
(undrained) k1<k2<k3<k4 (drained)
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Conclusion-Permeability is a critical parameter for the estimation of liquefaction-induced lateral deformations- Permeability is a critical parameter for the estimation of pile moments due to liquefaction-induced lateral ground deformation- Larger ground displacement is not always proportional to higher moment in piles
Yang, Z. and Elgamal, A. “Influence of Permeability on Liquefaction-Induced Shear Deformation,” Journal of Engineering Mechanics, ASCE, 128, 7, July 2002 44
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For Saturated Cohesionless soils…
Shear resistance depends on:
1) N1(60) , CPT qc1 , Vs
2) Soil/System Permeability k
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http://soilquake.net/openseespl/
46
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OpenSeesPL: http://soilquake.net/openseespl/
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OPENSEESPL Example Input Files (http://soilquake.net/openseespl/example_input_files/
Pile in Ground Strata 3-D Shear Beam Site Amplification48
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OPENSEESPL Example Input Files (http://soilquake.net/openseespl/example_input_files/
Ground Modification by Stone Columns. Pile-pinning, Earthquake Drain, or Deep Soil Mixing Grids
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Pile Groups and Piled Rafts
OPENSEESPL Example Input Files (http://soilquake.net/openseespl/example_input_files/
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