Macro–Micro Failure and Energy Evolution in Heterogeneous Fault Rock Masses

XRD diffraction scanning tests were utilized to determine rock mineral composition, and a numerical calculation model of heterogeneous granite was established utilizing the PFC. The macro and micro damage characteristics of the heterogeneous granite model were analyzed. During failure, the boundary energy, strain energy, and dissipation energy were monitored. The results indicates that confining pressure can enhance the elastic modulus of the model by approximately 1.5 times. Under non-confining pressure conditions, shear failure  is dominant in the model. Conversely, under confining pressure conditions, tensile-shear composite failure is prevalent. The micro-failure types are mainly slippage failure and shear failure. The microstructural strength of Albite and Quartz is found to increase with rising confining pressure, whereas that of Kaolinite is inhibited. Confining pressure has little effect on the microstructural strength of Potassium Feldspar. The critical confining pressure for the model is determined to be 15 MPa; strain energy is the dominant energy component at pressures below this threshold, while dissipation energy become dominant above it. At the micro-level, the boundary energy in the crack initiation energy is more sensitive to the confining pressure. In the peak strength energy, the growth rate of strain energy is greater than that of dissipation energy.