Microcrack Growth Behavior and CWFS Criterion Parameters Optimization of Granite with PFC

Based on the physical and mechanical parameters obtained in laboratory tests, along with the section scanning of granite specimens, a microgeometric model of the granite particles was established in the Particle Flow Code (PFC) programs. The loading codes were programed and adjusted using the Fish language to simulate both uniaxial and triaxial compression tests. The micromechanical behavior and the evolution of cracks from the microcosm to the macrocosm of the granite were obtained under different loading conditions based on the complete stress-strain curves, Acoustic Emission (AE) monitoring results and crack number obtained from the tests, and PFC simulation. On this basis, the Cohesion Weakening and Friction Strengthening (CWFS) criterion model parameters of the granite were optimized and verified using the stress-strain curves, the relationship between the cracks, friction energy and plastic strain, and Fast Lagrangian Analysis of Continua simulation. The optimized CWFS criterion parameters of initial cohesion, residual cohesion, initial friction angle, and residual friction angle, as well as the critical plastic strain epsilon(p)(c) and epsilon(p)(f) of the granite, are 23 MPa, 4.3 MPa, 0 degrees, 46.3 degrees, 0.0015, and 0.0037, respectively. This provides a scientific basis for the establishment of a rock constitutive model during the transfer from open pit to underground mining in the Xingshan Iron Mine in China.