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Published byChristiana Norman Modified over 8 years ago
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Liquefaction Mitigation using GeoComposite Vertical Drains
Kyle Rollins and Joshua K.S. Anderson Brigham Young University Civil & Environmental Engineering Dept Provo, Utah, USA
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Acknowledgements NCHRP-IDEAS Program Nilex, Inc. ConeTec, Inc.
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Liquefaction Mitigation by Densification Versus…
Vibro-Compaction Stone Columns Dynamic Compaction Compaction Grouting
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Liquefaction Mitigation by Drainage
Liquefiable Sand Drains
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EQ Drain with and without Filter Fabric
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Drain Installation EQ Drain Hollow Steel Mandrel Anchor Plate
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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.
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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
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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.
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Test Site Locations Vancouver, B.C. Treasure Island, CA
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Treasure Island Test Site
Downtown San Francisco Test Site
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Installation Induced Settlement
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Blast-Induced Settlement in Untreated Area
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Blast-Induced Settlement in Treated Area
Cluster 1 Cluster 2 (Wick Drains) Cluster 4 Cluster 5 Cluster 6 Cluster 7 Cluster 3 Cluster 8 Settlement Stakes Blast Holes
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Blast-Induced Settlement
Cluster 1 Cluster 2 (Wick Drains) Cluster 4 Cluster 5 Cluster 6 Cluster 7 Cluster 3 Cluster 8 Settlement Stakes Blast Holes 20 40 60 80 100
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Pore Pressure Response
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Vancouver BC Test Site Vancouver CANLEX Test Site EQ Drain Test Site
MasseyTunnel
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Typical CPT Profile
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Layout for EQ Drain Test Areas
1.22 m 4 Blast Holes at 5 m radius
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Pipe Mandrel with Minimum Densification
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Finned-Mandrel for Maximum Densification
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Avg. Installation-Induced Settlement
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Video of EQ Drain Test Click on picture to see second earthquake drain test in vancouver, BC
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Pore Pressure Response -High Vibration
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Blast Induced Settlement for EQ Drains Relative to Untreated Test Area
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Comparison of qc with Time
Low Vibration High Vibration
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ANALYSIS OF TEST RESULTS
Calibrate model with measured response from blast event. Compute expected response from earthquake event.
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Input Parameters for FEQDrain Analysis
Soil Layering Hydraulic Conductivity, K Modulus of Compressibility, Mv Drain Properties Nq/NL, Stress Cycle Ratio Td, Earthquake Duration
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Variation of Compressibility (Mv) with Ru
Keep Ru in this Range (Seed et al,1976)
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Reality Check on Input Parameters
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Measured and Computed Pore Pressure (Treasure Island)
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Measured and Computed Pore Pressure (Vancouver)
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Measured and Computed Settlement (Vancouver)
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Drain Performance for Various Earthquake Events and Drain Spacings
Magnitude Duration (sec) Nq/Nl Drain Spacing (m) Maximum Ru Settlement (mm) Blast (Vancouver) 8 4.0 1.22 1.0 310 6.0 2.0 0.91 0.40 31 6.75 17 0.47 35 3.0 0.61 48 7.5 0.65 53
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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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