Associative Plasticity for Dilatant Soils

Abstract

In this study, a set of rules is established that, when used in the modeling of dilatant soils, within the framework of associative plasticity, enables very successful shear and dilatancy predictions. The most important of the proposed principles are outlined as follows: (1) The plasticity model must have a loading surface that hardens kinematically and a failure surface that is perfectly plastic; and (2) experimental evidence shows that uniformly deformed sand samples dilate with a constant rate when they reach their ultimate strength value, while critical state is only achieved at very large strains (well in excess of 30%). There is a unique point A on the loading surface that corresponds to the experimentally observed dilatation rate. The hardening rule must, therefore, ensure that the stress point approaches A as it comes closer to the failure surface. The implementation of these rules to a plasticity model gives results that compare very well with experimental observations.