Challenges in Prediction Earthquake-Induced Settlements of Partially Saturated Sands

Several methods have been proposed to estimate the settlement of sands during earthquake shaking over the past forty years. Most of these methods have focused on sands in dry or water-saturated conditions, leaving a gap in our basic understanding of the mechanisms of earthquake-induced settlements of partially-saturated sands. The goal of this paper is to synthesize experience from the technical literature to form the basis of a quasi-effective stress-based methodology for prediction of the settlement of level, unsaturated sand profiles during earthquake shaking. An equivalent linear approach that includes an expression for the effective stress in unsaturated sands and an empirical definition of the pore water pressure generation during cyclic loading was deemed to be the most practical means of analysis. Results from the literature indicate that this approach is capable of considering the impacts of earthquake magnitude and stress state on the interrelationships between dynamic soil properties, pore water pressure response, and plastic volumetric straining expected during shaking. Proper consideration of these variables is necessary for accurate estimation of the settlement of unsaturated sands during earthquake shaking.