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Liquefaction Mitigation using GeoComposite Vertical Drains

Liquefaction Mitigation using GeoComposite Vertical Drains. Kyle Rollins and Joshua K.S. Anderson. Brigham Young University Civil & Environmental Engineering Dept Provo, Utah, USA. Acknowledgements. NCHRP-IDEAS Program Nilex, Inc. ConeTec, Inc.

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Liquefaction Mitigation using GeoComposite Vertical Drains

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  1. Liquefaction Mitigation using GeoComposite Vertical Drains Kyle Rollins and Joshua K.S. Anderson Brigham Young University Civil & Environmental Engineering Dept Provo, Utah, USA

  2. Acknowledgements • NCHRP-IDEAS Program • Nilex, Inc. • ConeTec, Inc.

  3. Liquefaction Mitigation by Densification Versus… Vibro-Compaction Stone Columns Dynamic Compaction Compaction Grouting

  4. Liquefaction Mitigation by Drainage Liquefiable Sand Drains

  5. EQ Drain with and without Filter Fabric

  6. EQ Drain Anchor Plate Hollow Steel Mandrel Drain Installation

  7. Potential Problems with Conventional Densification • Expensive and time consuming effort • Cost increases and success decreases as fines content increases. • Cost of improvement increases as initial blow count increases. • Improved density may be overestimated by conventional penetration correlations.

  8. Potential Advantages of Earthquake Drains • Reduced cost of installation • Shorter installation time • Greater flow capacity than stone columns • Densification during drain installation • May provide mitigation for silty sands that are difficult to densify

  9. PROJECT OBJECTIVES • Evaluate ability of drains to dissipate excess pore pressures. • Evaluate ability of drains to reduce liquefaction-induced settlement. • Provide case histories to validate/calibrate computer models.

  10. Test Site Locations Vancouver, B.C. Treasure Island, CA

  11. Treasure Island Test Site Downtown San Francisco Test Site

  12. Installation Induced Settlement

  13. Blast-Induced Settlement in Untreated Area

  14. Cluster 4 Cluster 3 Cluster 5 (Wick Drains) Cluster 2 (Wick Drains) Cluster 1 Cluster 6 Cluster 7 Blast Holes Cluster 8 Settlement Stakes Blast-Induced Settlement in Treated Area

  15. Cluster 4 Cluster 3 Cluster 5 (Wick Drains) Cluster 2 (Wick Drains) Cluster 1 Cluster 6 Cluster 7 Blast Holes Cluster 8 Settlement Stakes Blast-Induced Settlement 20 40 60 80 100

  16. Pore Pressure Response

  17. Vancouver BC Test Site Vancouver CANLEX Test Site EQ Drain Test Site MasseyTunnel

  18. Typical CPT Profile

  19. 1.22 m 4 Blast Holes at 5 m radius Layout for EQ Drain Test Areas

  20. Pipe Mandrel with Minimum Densification

  21. Finned-Mandrel for Maximum Densification

  22. Avg. Installation-Induced Settlement

  23. Video of EQ Drain Test

  24. PorePressureResponse-High Vibration

  25. Blast Induced Settlement for EQ Drains Relative to Untreated Test Area

  26. Comparison of qc with Time Low Vibration High Vibration

  27. ANALYSIS OF TEST RESULTS • Calibrate model with measured response from blast event. • Compute expected response from earthquake event.

  28. Input Parameters for FEQDrain Analysis • Soil Layering • Hydraulic Conductivity, K • Modulus of Compressibility, Mv • Drain Properties • Nq/NL, Stress Cycle Ratio • Td, Earthquake Duration

  29. Keep Ru in this Range Variation of Compressibility (Mv) with Ru (Seed et al,1976)

  30. Reality Check on Input Parameters

  31. Measured and Computed Pore Pressure (Treasure Island)

  32. Measured and Computed Pore Pressure(Vancouver)

  33. Measured and Computed Settlement (Vancouver)

  34. Drain Performance for Various Earthquake Events and Drain Spacings

  35. Conclusions Relative to Drains • Significant densification provided. • Rate of dissipation increased. • Settlement can be reduced for low Ru. • Drain layout must be designed for anticipated earthquake.

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