Isotropic–kinematic hardening model for coarse granular soils capturing particle breakage and cyclic loading under triaxial stress space

In this paper, a simple but comprehensive cyclic stress-strain model that incorporates particle breakage for granular soils including ballast and rockfill has been proposed on the basis of bounding surface plasticity theory within a critical state framework. Particle breakage and its effects are captured by a critical state line that is translated in voids ratio-stress space according to the dissipated energy (plastic work), through a hyperbolic function. A comprehensive equation related to particle breakage is proposed for the stress-dilatancy relationship in order to capture the complex dilatancy of granular soils. By extending Masing's rule to bounding surface plasticity theory and introducing a generalised homological centre, a combined isotropic-kinematic hardening rule and a mapping rule have been established to simulate more realistically the response of gravelly soils under cyclic loading. The applicability and accuracy of this model are demonstrated by comparing its predictions with experimental results for different types of granular soils, including rockfill, under both monotonic and cyclic loading conditions. This study shows that the model can capture the characteristic features of coarse granular soils under complex loading paths.