Experimental and Modelling Investigations of the Coupled Elastoplastic Damage of a Quasi-brittle Rock

Triaxial compression tests are conducted on a quasi-brittle rock, limestone. The analyses show that elastoplastic deformation is coupled with damage. Based on the experimental investigation, a coupled elastoplastic damage model is developed within the framework of irreversible thermodynamics. The coupling effects between the plastic and damage dissipations are described by introducing an isotropic damage variable into the elastic stiffness and yield criterion. The novelty of the model is in the description of the thermodynamic force associated with damage, which is formulated as a state function of both elastic and plastic strain energies. The latter gives a full consideration on the comprehensive effects of plastic strain and stress changing processes in rock material on the development of damage. The damage criterion and potential are constructed to determine the onset and evolution of damage variable. The return mapping algorithms of the coupled model are deduced for three different inelastic corrections. Comparisons between test data and numerical simulations show that the coupled elastoplastic damage model is capable of describing the main mechanical behaviours of the quasi-brittle rock.