Coupling Deterioration Model of Mechanical Parameters for the Jinping Marble Under Progressive Damage Conditions

Cognition of the deformation and failure characteristics of rock under progressive damage conditions is quite important for the stability assessment and numerical back analysis of underground projects. A series of cyclic loading/unloading tests for the Jinping marble were carried out to investigate its coupling deterioration evolution of mechanical parameters during the elastoplastic deformation and failure process. First, based on the triaxial cyclic loading and unloading testing results under different confining pressures, the evolution rules of its mechanical parameters were obtained. Second, some nonlinear evolution models were established to describe the progressive deterioration evolution of Young's modulus, cohesion, internal friction angle, and dilation angle respectively by introducing a new plastic internal variable with confining pressure dependence. Third, the modified binary-medium model was presented to reveal the coupling evolution mechanism of marble's strength parameters by describing the increase and decrease of the relative volume fraction of the bonding element and frictional element regulated by the load sharing principle. Finally, a new interaction matrix for marble's mechanical parameters was developed based on the multi-dimensional triangular pyramid type interrelations. The results can provide a reference for parameter deterioration during the establishment of mechanical models, stability assessment, and numerical back analysis for underground engineering.