Earthquake liquefaction, often referred to simply as liquefaction, is the process by which saturated, unconsolidated soil or sand is converted into a suspension during an earthquake. The effect on structures and buildings can be devastating, and is a major contributor to urban seismic risk. Ancient earthquakes have caused liquefaction, leaving a record in the sediments (paleoseismology). Liquefaction may refer to: Soil liquefaction, the process by which sediments are converted into suspension, as in earthquake liquefaction, quicksand, quick clay, and turbidity currents. ... Flour suspended in water In chemistry, a suspension is a colloidal dispersion (mixture) in which a finely-divided species is combined with another species, with the former being so finely divided and mixed that it doesnt rapidly settle out. ... An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy that radiates seismic waves. ... A mixed group of structures Urban seismic risk is special subset of the general term seismic risk. ... Paleoseismology is the study of ancient earthquakes as shown by the deformation of rocks. ...

Sand Compaction

Liquefaction occurs when a saturated sand formation is turned into a liquid. The key ingredient is a formation of loose, saturated sand. As seen in the figure, uniform sand grains can be packed either in a loose or a compact (dense) formation. Loose sand has usually been deposited gently underwater, either naturally, or sluiced into what is called hydraulic fill. The loose grains can support considerable weight, as they are in contact with each other in a statically stable formation. Image File history File links Seissand. ... Patterns in the sand Sand is an example of a class of materials called granular matter. ... A hydraulic fill is an embankment or other fill in which the materials are deposited in place by a flowing stream of water, with the deposition being selective. ...

Once strong earthquake shaking begins, the grains move and are no longer resting on each other. Eventually, the grains will settle into a more compact arrangement. However, this transition is not immediate, and requires excess water to leave the formation. For a short period of time, depending how long it takes for the water to drain from the formation, the grains float in a liquid slurry. The excess water is squeezed out which causes the quicksand condition at the surface. If there is a dry soil crust or impermeable cap, the sand slurry will sometimes come to the surface through cracks in the confining layer, bringing much of the excess water with it, creating sand boils, colloquially called "sand volcanos". Quicksand and warning sign at a gravel extraction site. ...

Soil liquefaction can cause damage to structures in several ways. Buildings whose foundations bear directly on sand which liquefies will experience a sudden loss of support, which will result in drastic and irregular settlement of the building. Liquefaction causes irregular settlements in the area liquefied, which can damage buildings and break underground utility lines where the differential settlements are large. Sand boils can erupt into buildings through utility openings, and may allow water to damage the structure or electrical systems. Soil liquefaction can also cause slope failures. Areas of land reclamation are often prone to liquifaction because many are reclaimed with hydraulic fill, and are often underlain by soft soils which can amplify earthquake shaking. Land reclamation is either of two distinct practices. ... A hydraulic fill is an embankment or other fill in which the materials are deposited in place by a flowing stream of water, with the deposition being selective. ...

Study of past liquefaction events in geologic formations can provide information about the strength of prehistoric earthquakes, a vital component of paleoseismology Paleoseismology is the study of ancient earthquakes as shown by the deformation of rocks. ...

Liquefaction primarily occurs in sands, but there are formations of quick clay, which can cause many of the same problems as liquefiable sands. Quick clay, also known as Leda Clay in Canada, is a unique form of highly sensitive clay, with the tendency to change from a relatively stiff condition to a liquid mass when it is disturbed. ...

Mitigating potential damage from liquefaction is part of the field of geotechnical engineering. Bostons Big Dig presented geotechnical challenges in an urban environment. ...

External links

• Soil liquefaction web page at University of Washington

• Earthquakes and the New Madrid Fault Line