Book Description

Liquefaction of loose, saturated, cohesionless soils is a phenomenon in which the soil mass suddenly loses shear strength, behaves as a fluid, and acquires a degree of mobility sufficient to permit large movements. This report reviews various case histories to determine common characteristics associated with liquefaction failures. A review of case histories reveals that liquefaction failures are dependent upon (a) a collapsible soil structure, (b) a saturated and undrained condition, and (c) a triggering mechanism. Typically collapsible soils which liquefied were fine, uniform loose sand deposits with D10 sizes ranging from 0.05 to 1.0 mm and a coefficient of uniformity ranging from 2 to 10. Saturated-undrained conditions provided a situation conducive to high pore pressure development upon collapse of the soil structure. Generally, water was the pore fluid; however, several unusual cases were reported with air as the pore fluid (termed fluidization). A variety of triggering mechanisms, including monotonically changing stresses, earthquakes, explosive blasts, and cyclic vibrations, were found to cause liquefaction failures. However, monotonically increasing shear stresses and earthquakes are the most common triggering mechanisms. Density is the most important property controlling the susceptibility of saturated-undrained sands to liquefaction. It as found that sands which liquefy when subjected to earthquake shakings do not become significantly more stable against reliquefaction. Conversely, vibrations appear to alter the sand structure, making a deposit less susceptible to liquefaction than indicated by density increases. (Author).