Liquefaction Mitigation Efforts

There are several options for mitigating liquefaction effects:

1. One option is to avoid locating buildings and infrastructure in areas with high liquefaction potential.

To determine the liquefaction potential of an area, proper soil characterization is essential. Characterization of soils is achieved by using historical, geological, and compositional information. Historical information describing what areas have liquefied in the past is useful in determining the future potential of liquefaction areas. Geological information about the soil's origin is also useful in determining liquefaction potential. For example, soils made up of sediments from lake, river, and aeolian (wind) deposits and artificial fill are all highly susceptible to liquefaction. Composition information of the soil is also an important factor in determining the liquefaction potential. Soils composed of well-rounded, well-sorted (particles of the same size) sandy material are the most susceptible to liquefaction.

Well-sorted, well-rounded grains susceptible to liquefaction

 

2. A second option for mitigating liquefaction effects is to require buildings to have foundations which will lessen impacts from liquefaction.

Generally, building foundations should have a sufficient degree of flexibility and be able to accommodate large ground deformations. Shallow foundations should move and settle uniformly, have a solid foundation mat, and utility lines should be designed with flexible connections to avoid breakage. Deep foundation elements essential to liquefaction mitigation are large diameter support pilings and a flexible connection to the overlying foundation.

Foundation design to lessen liquefaction impacts

 

3. A final option for liquefaction mitigation is to improve the soil.

The most important factors to improve in order to lessen liquefaction potential are compactness of the soil and drainage capacity. These are the techniques to accomplish compact soil and sufficient drainage capacity:

Compaction Grouting

Soil Compaction:

• Vibroflotation is the process of inserting a vibrating probe into the ground to cause compaction of sediments.
• Dynamic compaction, where a heavy weight is dropped on to the soil surface to compact loose sediments
• The practice of inserting stone columns into the ground is another technique used to decrease the liquefaction potential of soils.
• Compaction grouting is the process of injecting a water/sand/cement mixture into the ground to cause compaction of an existing loose soil layer. This technique is most often used when an existing building is located over a highly susceptible area.

Increasing Drainage Capacity:

• The techniques of inserting gravel or synthetic materials to increase drainage capacity of soils are used to mitigate liquefaction potential.

Source: Federal Emergency Management Agency (FEMA). Multi-hazard Identification and Risk Assessment: A Cornerstone of the National Mitigation Strategy. Washington, D.C., 1995 pg. 369

University of Washington, Soil Liquefaction Web Site

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