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Correlating, V s , q c and Cyclic Resistance of a Silty Sand through Laboratory Calibration Tests

Correlating, V s , q c and Cyclic Resistance of a Silty Sand through Laboratory Calibration Tests. An-Bin Huang, Yao-Tao Huang, and Yu-Chen Kuo Department of Civil Engineering National Chiao Tung University Hsin Chu, TAIWAN. Effects of nonplastic fines on CRR. Higher CRR ? Lower CRR ?

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Correlating, V s , q c and Cyclic Resistance of a Silty Sand through Laboratory Calibration Tests

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  1. Correlating, Vs, qc and Cyclic Resistance of a Silty Sand through Laboratory Calibration Tests An-Bin Huang, Yao-Tao Huang, and Yu-Chen Kuo Department of Civil Engineering National Chiao Tung University Hsin Chu, TAIWAN

  2. Effects of nonplastic fines on CRR • Higher CRR ? • Lower CRR ? • Depends… ?

  3. Effects of nonplastic fines on qc • Variation of qc under the same void ratio and stress conditions as the fines content changes ? • What void ratio ?

  4. Seed and de Alba (1986)

  5. Ishihara (1993)

  6. Stark and Olson (1995)

  7. Effects of nonplastic fines on Vs • Variation of Vs under the same void ratio and stress conditions as the fines content changes ? • What void ratio ?

  8. Andrus and Stokoe (2000)

  9. Youd et al. (2001) • …The CRR corrections based on fines contents should be used with engineering judgment and caution…

  10. qc Vs Liquefaction potential mapping

  11. Laboratory calibration tests • CPT calibration tests • Vs measurements with bender elements • Cyclic triaxial tests • Use Mai Liao Sand (MLS), a typical silty fine sand in Central Western Taiwan

  12. Coarse grains Fine grains

  13. CPT calibration tests in MLS • FC = 0%, 15%, 30% and 50% • Dro = 50%, 70% and 85% • s’v = 100, 200 and 300 kPa • K = 0.5, 1 and 2

  14. The calibration chamber

  15. Sample preparation • Dry deposition • Saturated under a backpressure or dry • Stresses applied in steps follow the designated K value

  16. n = C1+C2 =

  17. Effects of fines on in MLS

  18. Cyclic triaxial tests • Sample preparation by wet tamping in 4 layers • K = 1 • Saturated under a back pressure • s’v = 100 kPa • Bender element Vs measurement on the same triaxial specimen

  19. Tentative due to differences in sample preparation methods

  20. Concluding remarks • The current qc and Vs methods too conservative? Not necessarily, due to differences in • Shearing mode • K values • Fines affect CRR and Vs through soil structure, grain characteristics and compressibility • Drainage effects are much more significant to qc

  21. When using CPT for liquefaction potential assessment in MLS • Make adjustment based on t50 from pore pressure dissipation test or change of qc after pore pressure dissipation • But not IC

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