Breakage critical state of gravels with different gradings. Part II: Constitutive modelling

A unified critical state surface for gravels considering the effect of initial grading and particle breakage was proposed in Part I based on the test results of large-scale triaxial compression tests. In this study, we proposed a state-dependent elastoplastic constitutive model to predict the shear behaviors of gravels in the framework of bounding surface plasticity and critical state theory. A simple state parameter with a reference to the unified critical state surface was applied to the dilatancy equation and the bounding stress ratio in the proposed model. The proposed constitutive model can well capture the grading state index, the relative breakage index, the deviatoric stress and the void ratio at the end of tests, and the stress-strain relationships during the shearing process. The model can still be improved by considering the influence of the confining pressure on the critical state strength.