Advanced Site Monitoring and Characterization of Site Dynamic Properties

Mourad Zeghal, Tarek Abdoun and Vicente MercadoDepartment of Civil and Envir. Eng., Rensselaer Polytechnic Institute, Troy, NY

Anirban DeManhattan College

Quake Summit 2010, October 8 - 9, 2010.

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

Introduction• Evaluation of in-Situ Soil Dynamic Properties

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

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

Shape Acceleration Array

3D measurements• Accelerations• Permanent

displacements

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

NEES Wildlife Refuge Site• Imperial Valley of Southern California • Experienced multiple earthquakes and liquefaction and lateral

spreading events in the past

NEES Wildlife Refuge Site

• Granular layer anticipated to liquefy during medium-size earthquakes

• Significant lateral spreading expected

Shape Acceleration Array

Optimal configuration: analytical considerations and numerical simulations

Installation and Site Monitoring

Baja California Earthquake: April 4, 2010

Low Amplitude Site Properties

Field Test

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

17

Computational Example

18

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

19

Identification Stages

20

Identification Stages

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

Acknowledgements

• This research is supported by the National Science Foundation (NEESR CMS-0830325)

• NEES@UCSB

• NEES@UTexas