Shear Localization Due to Liquefaction-Induced Void Redistribution in a Layered Infinite Slope

A new approach for estimating the susceptibility of a layered, liquefiable, infinite slope to shear deformations associated with void redistribution is presented. The excess pore water pressures associated with liquefaction produce upward seepage within the slope. The lower portion of a liquefied layer expels a certain volume of pore water, Vcon, as it contracts (densifies). If the liquefied layer is overlain by a lower permeability soil, then the pore water expelled from the lower contracting zones can become trapped causing void ratio increase in a dilating sublayer near the interface, reducing its undrained shear strength. The volume of water that can be absorbed by the dilating sublayer prior to slope instability is termed the dilation capacity, Vdil. The ratio Vcon/Vdil is a measure of the potential for localization due to strength losses from void redistribution. The localization potential is shown to strongly depend on relative density, slope angle, and thickness of the liquefiable layer. The thickness of the dilating sublayer, a critical parameter, is significantly greater than the thickness of a shear band (which may be only tens of grain diameters). A detailed example is presented to show how the procedure can be applied. The results of the analysis are shown to be consistent with observed deformations and localizations in centrifuge model tests.