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Services: Liquefaction Mitigation

Conditions for Liquefaction:
  • Saturated ground.
  • Loose granular and other non-plastic soils.
  • Strong ground motion.

How Liquefaction Occurrs:
  • Earthquake Shear strains transfer forces to pore water.
  • Excess pore water pressure cannot dissipate fast enough.
  • Effective stress is reduced to “zero” (lead to loss of bearing capacity)
  • After shaking stops pore water pressures dissipate (leads to excessive settlement).

Approach to Mitigation of Liquefaction Effects (Criteria)

Counteract causes of liquefaction:
  • Densify loose granular soil
  • Dewater or control water pressure buildup (Drainage)
  • Modify cohesive properties of soil
  • Reinforce soil (reduce strain level during EQ)
  • Remove and replace with nonliquefiable soil

Control consequences of liquefaction:
  • Reinforce and connect structural shallow foundation
  • Install deep foundation designed for liquefiable soils
  • Partial soil improvement (control deformations)

particle rearrangement due to
seismic shaking

Niigata, Japan, 1964 - Loss of Bearing Capacity due to Soil Liquefaction
click to enlarge

Typical sand Boils from Liquefaction
click to enlarge

Applicable Improvement Criteria Based on Liquefiable Soil Type


Clean Sands
<80% No
100 Sieve

Silty Sands
<15% Fines
<3% Clay

Silty Sands /
Sandy Silts
<60% Fines
<8% Clay

Non-Plastic Silts
Densification XXX XX X
(with pre-installed wicks)
Drainage XX X    
Reinforcement   X XX XXX

Red = Soil type
Green = Criterion

Common Techniques and Type of Improvement

  Densification Drainage Reinforcement
  • Dynamic Compaction
  • Vibro Tamper
  • Vibro Compaction
  • Vibro-Stone Columns
  • Compaction Grouting
XX   X
  • Deep Mixing
  • Permeation Grouting
  • Jet Grouting

Green = Criterion
Red = Improvement Technique

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