Soil liquefaction

Soil liquefaction occurs when a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid.

The intense shaking of an earthquake can cause loosely packed water logged materials, such as sandy stream deposits or fill, to be transformed into a substance that acts like fluids. The phenomenon of transforming a somewhat stable soil into mobile material capable of rising toward Earth’s surface is known as liquefaction. When liquefaction occurs, the ground may not be capable of supporting buildings, and underground storage tanks and sewer lines may literally float toward the surface (Figure 1).

During the 1989 Loma Prieta earthquake, in San Francisco’s Marina District, foundations failed, and geysers of sand and water shot from the ground, evidence that liquefaction had occurred (Figure 2).

Figure 2 – Liquefaction These “sand volcanoes,” produced by the Christchurch, New Zealand, earthquake of 2011, formed when “geysers” of sand and water shot from the ground, an indication that liquefaction occurred.

Liquefaction also contributed to the damage inflicted on San Francisco’s water system during the 1906 earthquake. During the 2011 Japan earthquake, liquefaction caused entire buildings to sink several feet.

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