advanced site monitoring and characterization of site dynamic properties mourad zeghal, tarek abdoun...
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Advanced Site Monitoring and Characterization of Site Dynamic Properties
Mourad Zeghal, Tarek Abdoun and Vicente Mercado
Department of Civil and Envir. Eng., Rensselaer Polytechnic Institute, Troy, NY
Anirban DeManhattan College
Quake Summit 2010, October 8 - 9, 2010.
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Outline
• Introduction and Objectives• Shape-Acceleration Array• New Array at Wildlife Refuge Site• Recent Earthquake and Field Test• Data Reduction and System Identification • Concluding Remarks
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Introduction• Evaluation of in-Situ Soil Dynamic Properties
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Introduction
• Evaluation of Soil Dynamic and nonlinear Properties: soil sample tests
How representative of in-situ conditions:
•Stress-strain response (damping, etc.)
•Lateral spreading and failure
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Objectives
• Install permanently a network of Shape-Acceleration Arrays (SAAs) with an optimal configuration at the NEES Wildlife refuge site
• Monitor the site response (acceleration, permanent displacement and pore pressure)– Future earthquakes (lateral spreading expected)– Field test(s) using T-Rex
• Develop efficient data reduction and system identification tools to evaluate the in situ 3D dynamic and nonlinear properties of the site
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Shape Acceleration Array
3D measurements• Accelerations• Permanent
displacements
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Wireless Shape Acceleration Array
Sensing System Cost Array Depth
Real Time Monitoring
Capability and Comments
Manual Slope Inclinometer $20,000 30m No
Costs include monitoring based on 2 readings/ month for 4 months
Slope Inclinometer Array $75,000 30m Yes
1D deformation measurement and no acceleration measurement
Accelerometer Downhole Array $100,000 30-50m Yes
Acceleration measurement at about 5m intervals and no deformation reading
Wireless Shape-Acceleration Array $10,000 30m
Yes Yes
3D acceleration and 3D deformation measurements
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NEES Wildlife Refuge Site• Imperial Valley of Southern California • Experienced multiple earthquakes and liquefaction and lateral
spreading events in the past
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NEES Wildlife Refuge Site
• Granular layer anticipated to liquefy during medium-size earthquakes
• Significant lateral spreading expected
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Shape Acceleration Array
Optimal configuration: analytical considerations and numerical simulations
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Installation and Site Monitoring
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Baja California Earthquake: April 4, 2010
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Low Amplitude Site Properties
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Field Test
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Field Test Data
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• CMP: Control Motion Approach (prescribed motion at all sensor “node” locations, Elmikaty and Zeghal)
• CMP Finite Element formulation
int ln
int int ( , ) ( )
ext b c
T
ext T
d
d
Md F -F F
F F d p N :σ
F N b
Interior node
Boundary node
Multi-Dimensional Local Identification
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Computational Example
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Constitutive Model (Saturated Clay)• Von-Mises yield criteria, multi-yield surfaces
• Associated flow rule• Kinematic Hardening rule• Shear Modulus Degradation and Reduction
• Visco-Elasto-Plastic Stress-Strain relation
• Identification Parameters
23( , , ) ( ) : ( ) 0
2i i i if k kα α α σ s spd dLε Q f
Qσ
d dL aα μ
0
( 1)
0
( )
1
ppn nn
G GG G
Prevost, 1987
( ) ( ) ( 0)G N N G N ( , ) ( ) ( )G N N G
vep epd d d σ = σ ε
, , , , , ,o o ref pG n W G
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Identification Stages
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Identification Stages
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Concluding Remarks
Work in progress to develop a capability to: (1) measure cyclic and permanent displacements
of field sites (2) Efficiently characterize and estimate (low and
large strain) three-dimensional in situ dynamic properties
Objective: Enable better understanding of liquefaction, lateral spreading and failure of sites
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Acknowledgements
• This research is supported by the National Science Foundation (NEESR CMS-0830325)
• NEES@UCSB
• NEES@UTexas