Initiation of Soil Liquefaction Under Static Loading Conditions

Abstract

Liquefaction of loose, saturated sands may be caused by cyclic or static (monotonically increasing) undrained loading. Most previous studies of static liquefaction behavior have emphasized liquefaction susceptibility and the behavior of liquefied soils. An experimental investigation is undertaken to evaluate the stress conditions required to initiate liquefaction and the influence of various parameters on those stress conditions. The static liquefaction resistance, denned as the shear stress increase under undrained conditions required to initiate liquefaction, is observed to increase with increasing relative density and confining pressure, and to decrease dramatically with increasing initial shear stress level. At high initial shear stress levels, initiation of liquefaction is observed to result from increases in shear stress under undrained conditions of only a few percent of the initial shear stress. The distinction between the initiation and the effects of liquefaction is discussed, and an expression for a factor of safety against the initiation of liquefaction is proposed.