A rate- and pressure-dependent damage-plasticity constitutive model for rock

Abstract

A new damage-plasticity constitutive model which takes account of the effect of confining pressure and strain rate on the strength and post-peak behaviour is proposed for rock subjected to dynamic loading. The model treats the compressive and tensile damages, both related to plastic and volumetric deformations, separately. The strain rate effect is considered by incorporating a newly developed dynamic increase factor formula, which reflects the pure rate sensitivity of rock, into the yield surface via radial enhancement approach. Fractionally-associated flow rule and lode-angle dependency are employed to capture the shear dilation behaviour of rock. The new model is then implemented into LS-DYNA via a user defined material subroutine to simulate the mechanical response of rock under various loading scenarios including triaxial compression, direct tension, Split Hopkinson Pressure Bar compression, oval-nose projectile penetration and explosive blast action, reported in literature. The robustness and accuracy of the new model are demonstrated by validating against available experimental results and by benchmarking with the reported simulations.