A Modified Empirical Model for Predicting Liquefaction in Partially Saturated Sands

One of the theoretical judgments for liquefaction triggering is that the maximum excess pore pressure ratio (r_u,max) becomes unity. Some studies show that reducing the degree of saturation and creating partially saturated zones in the soil can lower r_u,max, preventing liquefaction. Geotechnical engineers are interested in predicting r_u,max as a control parameter for liquefaction triggering. Empirical models to predict r_u,max of a free-field layer of partially saturated sand are mostly based on large and small-scale experimental setups, which cannot exactly explore the effect of high effective stresses. Also, the liquefaction responses obtained from the experimental studies mostly focus on shallow soil layers, limiting their applicability to deep field layers. This paper modifies an existing empirical model (RuPSS model) to make it able to capture the effect of high effective stresses up to 100 kPa in the prediction of r_u,max of partially saturated sands in free-field conditions. A comparison of r_u,max obtained from RuPSS model and the modified RuPSS model with the experimental test results confirms that the RuPSS model is unable to predict r_u,max response under high effective stress while the modified RuPSS model can acceptably predict r_u,max of partially saturated sands.