1. 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

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

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

4. Field Tests for assessing liquefaction potential 1 2 3 4 5 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

5. Shear Wave Velocity Measurements 1 2 3 4 5 Cross-hole Down hole Seismic cone Suspension PS-logger Surface wave method Non-invasive Efficient Cost effective

6. Basic Principle of Surface Wave Method 1 2 3 4 5 V S1 V S2 V S3 VSVS z Frequency component Geophones f V Dispersion curve Inversion Dispersion analysis Field Testing

7. 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) 1 2 3 4 5

8. SASW Method Unwrapping in f domain f  f v 1 2 3 4 5 

9. Multi-station Data Acquisition  k T = 2  /  1 v t-x domain 1 2 3 4 5 u(t m,x n ) Measurement: f =10, v = 200 m/s x t

10. MSASW Method f-x domain 22  xx Unwrapping in x domain DFT w.r.t. time domain 1 2 3 4 5 x f  R2R2

11. MWTSW Method f-k domain f-v domain f-x domain t-x domain DSFT w.r.t. space domain k 1 2 3 4 5

12. Multi-station Analysis of Surface Wave 1 2 3 4 5 ： Source ： Geophone L x0x0 xx 0 1 N-2 N-1

13. Multi-station Wavefield Transform 1 2 3 4 5 f- f-vf-v f-kf-k f-pf-p

14. Verification Case - Site 1 2 3 4 5

15. Seismic Equipment 1 2 3 4 5

16. Verification Case – Field Testing 1 2 3 4 5

17. Verification Case – Dispersion Analysis Dx = 0.5 m, L = 11.5 m 1 2 3 4 5

18. Verification Case – Dispersion Analysis Dx = 1 m, L = 23 m 1 2 3 4 5

19. 1 2 3 4 5

20. Verification Case – Inverse Analysis 1 2 3 4 5

21. Verification Case Vs and FS against liquefaction 3 4 5 1 2

22. Surface Wave Seismic Imaging 3 4 5 1 2

23. 3 4 5 1 2

24. 3 4 5 1 2

25. Andrus and Stokoe (2000) 1 2 3 4 5

26. Summary 3 4 5 1 2 Advantages of MASW Field testing simple & efficient Multi-station redundancy Automation: site quality control Robustness: dispersion curve visualized 2-D imaging

27. Summary 3 4 5 1 2 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

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