A modified bounding surface plasticity model for sand

A modified bounding surface plasticity model developed within the critical state soil mechanics framework is presented. Herein a modified version of the Dafalias and Manzari (2004) model is proposed, specifically developed to improve its capability to reproduce the cyclic behaviour of sands under different strain levels adopting a unique set of constitutive parameters. The proposed modified version of the model includes a thermodynamically consistent isotropic hyperelastic formulation for the very small strain range, which realistically reproduces the nonlinear stress dependence of the elastic stiffness. Furthermore, modified versions of the plastic modulus and dilatancy laws are introduced leading to a more realistic small to medium strain range cyclic behaviour, while preserving the original good predictive capability for monotonic and cyclic loading at large strains. The model response is illustrated by comparison with experimental data over a wide range of void ratios and stress states.