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NCREE Ming-Hung Chen* NCU Kuo-Liang Wen NTU Chin-Hsiung Loh

U.S.-Taiwan Workshop on Soil Liquefaction. Experience of Suspension P-S Logging Method and Empirical Formula of Shear Wave Velocities in Taiwan. NCREE Ming-Hung Chen* NCU Kuo-Liang Wen NTU Chin-Hsiung Loh USC Robert L. Nigbor. INTRODUCTION.

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NCREE Ming-Hung Chen* NCU Kuo-Liang Wen NTU Chin-Hsiung Loh

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  1. U.S.-Taiwan Workshop on Soil Liquefaction Experience of Suspension P-S Logging Method and Empirical Formula of Shear Wave Velocities in Taiwan NCREE Ming-Hung Chen* NCU Kuo-Liang Wen NTU Chin-Hsiung Loh USC Robert L. Nigbor

  2. INTRODUCTION • Nearly 700 free-field strong motion stations were set in Taiwan • Since 2000, National Center for Research on Earthquake Engineering (NCREE) collaborated with Central Weather Bureau (CWB) in site investigating.

  3. ●investigated ▲unfinished

  4. INTRODUCTION • Nearly 700 free-field strong motion stations were set in Taiwan • Since 2000, National Center for Research on Earthquake Engineering (NCREE) collaborated with Central Weather Bureau (CWB) in site investigating. • Suspension P-S Logging method was executed in this project

  5. INTRODUCTION (cont’d) • Lots of measuring in soil, gravel and rock layers were experienced • Based on the abundant and reliable shear wave velocities, an empirical formula for alluvial deposits was developed • For some specific sites, surface wave test, seismic refraction test and downhole velocity test were also executed

  6. CHARACTERISTICS OF SUSPENSION P-S LOGGING METHOD • The entire probe in lowered into the borehole filled with water • The separation of the two receivers is one meter • Average wave velocity is determined by inversion of the wave travel time between the two receivers.

  7. B A C D CHARACTERISTICS OF SUSPENSION P-S LOGGING METHOD (cont’d) • Path A – surface wave and seismic refraction • Path B – downhole and uphole • Path C – crosshole • Path D – suspension P-S logging

  8. CHARACTERISTICS OF SUSPENSION P-S LOGGING METHOD (cont’d) • receiver-to-receiver, R-R method • source to receiver, S-R method • Plot all records together to be the depth sequence

  9. P-wave

  10. S-wave

  11. CHARACTERISTICS OF SUSPENSION P-S LOGGING METHOD (cont’d) Spectrum of different layers Clay Vs=263 m/sec l  0.44 m Sand Vs=270 m/sec l  0.54 m Gravel Vs=358 m/sec l  0.30 m Rock Vs=1176 m/sec l  0.67 m

  12. CHARACTERISTICS OF SUSPENSION P-S LOGGING METHOD (cont’d) I: P- wave appears in S-wave recordII,III: S-wave appears in P-wave record

  13. EMPERICAL FORMULA OF SHEAR WAVE • 45 boreholes locate in southwestern alluvium plain area of Taiwan

  14. YunLin ChiaYi TaiNan

  15. EMPERICAL FORMULA OF SHEAR WAVE • 45 boreholes locate in southwestern alluvium plain area of Taiwan • Two major factors: SPT-N value & depth

  16. EMPERICAL FORMULA OF SHEAR WAVE • 45 boreholes locate in southwestern alluvium plain area of Taiwan • Two major factors: SPT-N value & depth • Proposing form: vs = c1+ c2·z+ c3·N1 • N1= corrected N value to a standard σ’= 1 kg/cm2…………….….Liao & Whitman

  17. EMPERICAL FORMULA OF SHEAR WAVE • 45 boreholes locate in southwestern alluvium plain area of Taiwan • Two major factors: SPT-N value & depth • Proposing form: vs = c1+ c2·z+ c3·N1 • vs = c1+4.09·z+ c3·N1

  18. EMPERICAL FORMULA OF SHEAR WAVE • 45 boreholes locate in southwestern alluvium plain area of Taiwan • Two major factors: SPT-N value & depth • Proposing form: vs = c1+ c2·z+ c3·N1 • vs = c1+4.09·z+ c3·N1 • vs = 139.1 + 4.09·z + 2.0415∙N1

  19. PREDICTED AND MEASURED SHEAR WAVE VELOCITIES

  20. COMPARISON WITH OTHER TESTS

  21. CONCLUSION • Very high-resolution data reliably for suspension P-S logging method • More than 200 boreholes have been tested • Materials are classified into three layers as soil, rock and gravel • Empirical formula of shear wave velocity is available in terms of drilling depth and corrected SPT-N values

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