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. Drain Installation
EQ Drain
Hollow Steel Mandrel
Anchor Plate

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

13. Installation Induced Settlement

14. Blast-Induced Settlement in Untreated Area

15. 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

16. 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

17. Pore Pressure Response

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

19. Typical CPT Profile

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

22. Pipe Mandrel with Minimum Densification

23. Finned-Mandrel for Maximum Densification

24. Avg. Installation-Induced Settlement

25. Video of EQ Drain Test
Click on picture to see second earthquake drain test in vancouver, BC

26. Pore Pressure Response -High Vibration

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

28. Comparison of qc with Time
Low Vibration
High Vibration

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

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

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

32. Reality Check on Input Parameters

33. Measured and Computed Pore Pressure (Treasure Island)

34. Measured and Computed Pore Pressure (Vancouver)

35. Measured and Computed Settlement (Vancouver)

36. 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

37. 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.