San Francisco Bay Region Geology and Geologic Hazards

Introduction > What Can I Do?

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What Can I Do?

Liquefaction can do great damage where it occurs during an earthquake, but the major cause of damage in an earthquake is shaking. Earthquake-induced landslides and surface fault rupture are other hazards of concern. The whole range of earthquake hazards should thus be addressed together. The way this is done will depend on the objective or the site/structure. For many this will be evaluating hazard to a home, but for others it may be for designing new construction or making land use decisions.

The actions one should take in an area subject to liquefaction depend on the use and occupants of the structure, the degree of hazard, the topographic setting, one's willingness to accept risk, and the degree to which the hazard is understood and quantified. If the three factors necessary for liquefaction are thought to exist at a site, then obtaining the advice of an expert geologist or geotechnical engineer is recommended.

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One approach to ground improvement is dynamic deep compaction.
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Once the liquefaction hazard is identified and characterized, methods of accommodation or mitigation can be considered. Mitigation is accomplished through a variety of approaches, including: (1) avoiding hazardous areas, (2) purchasing insurance to cover anticipated losses, (3) "improving" the ground so it is less susceptible to liquefaction or so that if liquefaction does occur the amount of surface deformation is reduced, and (4) fortifying structures to withstand liquefaction of underlying soils.

The table below shows some of the ground improvement and structural solutions that are available to reduce hazard from liquefaction.

Ground improvement and structural solutions that are available to reduce hazard from liquefaction.
General Category Mitigation Methods Notes
I. Excavation and/or compaction
  1. Excavation and disposal of liquefiable soils
  2. Excavation and recompaction
  3. Compaction (for new fill)
II. In-situ ground densification
  1. Compaction with vibratory probes (e.g.: Vibroflotation, Terraprobe, etc.)
  2. Dynamic consolidation (Heavy tamping)
  3. Compaction piles
  4. Deep densification by blasting
  5. Compaction grouting
  • Can be coupled with installation of gravel columns
  • Can also provide reinforcement
III. Selected other types of ground treatment
  1. Permeation grouting
  2. Jet grouting
  3. Deep mixing
  4. Drains
    • Gravel drains
    • Sand drains
    • Pre-fabricated strip drains
  5. Surcharge pre-loading
  6. Structural fills
  • Many drain installation processes also provide in-situ densification.
IV. Berms, dikes, sea walls, and other edge containment structure/systems
  1. Structures and/or earth structures built to provide edge containment and thus to prevent large lateral spreading.
V. Deep foundations
  1. Piles (installed by driving or vibration)
  2. Piers (installed by drilling or excavation)
  • Can also provide ground densification
VI. Reinforced shallow foundations
  1. Grade beams
  2. Reinforced mat
  3. Well-reinforced and/or post-tensioned mat
  4. "Rigid" raft
(table from Seed and others, 2001)



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