Dynamic constitutive model for rockfill materials based on generalized plasticity theory

The stress-strain behaviors of typical rockfill materials under cyclic loading with constant and variable stress amplitudes are analyzed. The stress-dilatancy equations, loading directions, tangential modulus and the representations of plastic modulus are derived based on experimental observations, and a generalized plasticity model is proposed to simulate the dynamic behaviours of rockfill materials. The model treats all the loading-unloading-reloading phases as elastoplastic ones and captures the hardening effects (the influences of the accumulated volumetric strain on the dilatancy and the overall stress strain behaviour) during cyclic loading by incorporating an aging function into the stress-dilatancy equations. There are totally 12 parameters involved in the proposed model, all of which can be determined by the conventional monotonic and cyclic tests. To check the validity of the proposed model, the parameters of two rockfill materials are calibrated based on the experimental data, and the typical cycle triaxial compression tests with constant and variable stress amplitudes are modeled. Satisfactory agreement between the numerical and experimental results under different confining pressures confirms the capability of the proposed model in capturing the hysteretic stress-strain behaviours and the accumulation of permanent deformation under cyclic loading effectively.