The Use of MASW in the Assessment of Soil Liquefaction Potential

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 • Backgrounds • Multi-channel Analysis of Surface Wave • Verification Case • 2-D Imaging of Liquefaction Potential • 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 • Standard Penetration test（SPT） • Cone Penetration Test（CPT） • Shear Wave Velocity Measurements (SWV) • Vs 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 Gmax required for site response 1 2 3 4 5

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

6. Basic Principle of Surface Wave Method 1 Frequency component Geophones 2 VS VS1 3 4 VS2 5 VS3 z Dispersion curve Field Testing V Dispersion analysis Inversion f

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 1 Df 2 3 4 5 Unwrapping infdomain Df v f f

9. l = 2p/k T = 2p/w v 1 Multi-station Data Acquisition 1 u(tm,xn) Measurement: f =10, v = 200 m/s 2 3 4 5 t t-x domain x

10. Df l Dx 2p Unwrapping in xdomain f-x domain MSASW Method 1 DFT w.r.t. time domain 2 3 4 5 f f R2 x

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

12. Multi-station Analysis of Surface Wave 1 0 1 N-2 N-1 2 x0 Dx L 3 ：Source 4 ：Geophone 5

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

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 AnalysisDx = 0.5 m, L = 11.5 m 1 2 3 4 5

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

19. Verification Case – Dispersion AnalysisDx = 1 m, L = 23 m 1 2 3 4 5

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

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

22. Surface Wave Seismic Imaging 1 2 3 4 5

23. Surface Wave Seismic Imaging 1 2 3 4 5

24. Surface Wave Seismic Imaging 1 2 3 4 5

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

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

27. 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 1 2 3 4 5

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