The Use of MASW in the Assessment of Soil Liquefaction Potential Chih-Ping Lin C-C Chang, I-L Chen, T-S Chang National Chiao Tung University, Taiwan November 4, 2003

Outline 1.Backgrounds 2.Multi-channel Analysis of Surface Wave 3.Verification Case 4.2-D Imaging of Liquefaction Potential 5.Summary

Acknowledgement Funding for this research was provided by the National Science Council and Institute of Planning & Hydraulic Research.

Field Tests for assessing liquefaction potential Standard Penetration test （ SPT ） Cone Penetration Test （ CPT ） Shear Wave Velocity Measurements (SWV) V s vs. Liquefaction resistance Effects of large particles minor Non-invasive method can be used Can be measured in the lab and in-situ Directly related to G max required for site response

Shear Wave Velocity Measurements Cross-hole Down hole Seismic cone Suspension PS-logger Surface wave method Non-invasive Efficient Cost effective

Basic Principle of Surface Wave Method V S1 V S2 V S3 VSVS z Frequency component Geophones f V Dispersion curve Inversion Dispersion analysis Field Testing

Surface Wave Methods Two-station methods Steady-state Rayleigh wave method (SSRW) Spectral analysis of surface wave (SASW) Multi-station Method Phase-offset regression (MSASW) Multi-station wavefield transformation of surface wave (MWTSW)

SASW Method Unwrapping in f domain f  f v 

Multi-station Data Acquisition  k T = 2  /  1 v t-x domain u(t m,x n ) Measurement: f =10, v = 200 m/s x t

MSASW Method f-x domain 22  xx Unwrapping in x domain DFT w.r.t. time domain x f  R2R2

MWTSW Method f-k domain f-v domain f-x domain t-x domain DSFT w.r.t. space domain k

Multi-station Analysis of Surface Wave ： Source ： Geophone L x0x0 xx 0 1 N-2 N-1

Multi-station Wavefield Transform f- f-vf-v f-kf-k f-pf-p

Verification Case - Site

Seismic Equipment

Verification Case – Field Testing

Verification Case – Dispersion Analysis Dx = 0.5 m, L = 11.5 m

Verification Case – Dispersion Analysis Dx = 1 m, L = 23 m

Verification Case – Inverse Analysis

Verification Case Vs and FS against liquefaction

Surface Wave Seismic Imaging

Andrus and Stokoe (2000)

Summary Advantages of MASW Field testing simple & efficient Multi-station redundancy Automation: site quality control Robustness: dispersion curve visualized 2-D imaging

Summary The results show that the MASW efficient, cost effective, and non-invasive useful in gravelly soils effective for ‘first look’ or investigation of lateral variations Further Research Lateral resolution Inversion and vertical resolution

Thank You! Chih-Ping Lin Geotechnical Engineering Group National Chiao Tung University