Explicit Integration and Implementation of State-Dependent Constitutive Model for Rockfill Materials

The dilatancy and stress-strain relationship of rockfill materials often depend on their material states. To better simulate the strength and deformation behaviors of rockfill materials under complex stress states, the state void-ratio index was incorporated into Rowe’s stress-dilatancy equation, bounding stress ratio, and plastic modulus. A state-dependent constitutive model was established within the framework of the critical state theory and the bounding surface plasticity theory. The proposed model can well describe the strain hardening, strain softening, and dilatancy behaviors of rockfill materials. Thereafter, the adaptive sub-stepping explicit integration algorithm was adopted in the state-dependent model and implemented into a finite element code. To validate the proposed scheme, a numerical model was established at element scale to simulate drained triaxial compression tests in a large density and pressure ranges. Comparisons between the simulation results and experimental data, the performance of the explicit integration algorithm for the state-dependent constitutive model are analyzed. The accuracy and efficiency of the explicit integration to describe the state-dependent behavior of rockfill materials is verified, which lays a foundation for further engineering applications.