Failure Model of Nonlinear Creep Damage Evolution of Rock based on PFC

This study investigates the creep behavior and crack evolution characteristics of rock under axial pressure and shear loads using the Particle Flow Code (PFC2D) software. The results show that the rock exhibits typical three-stage creep behavior, including transient creep, steady-state creep, and residual stability stages under both axial pressure and shear load. Under axial pressure, the displacement decay rate is slower, with compression-dominated deformation and significant suppression of crack propagation due to the confining pressure. This delays the occurrence of accelerated creep. In contrast, under shear load, the displacement decay rate is faster, and cracks propagate along the shear direction, forming a distinct shear band with a failure mode combining tensile and shear fractures. Crack propagation under axial pressure primarily consists of localized shear-type microcracks, reflecting the suppressive effect of confining pressure, while shear load induces crack formation along the maximum shear stress direction, transitioning from tensile microcracks to through-going shear cracks over time. These findings suggest that high confining pressure in deep underground environments can effectively inhibit rock creep deformation, but attention must be given to the evolution of microcracks in locally stressed regions.