Particle flow simulation of macro- and meso-mechanical behavior of the prefabricated fractured rock sample

To examine the macro-and meso-mechanical behaviors and crack propagation mode of the prefabricated and fractured rock sample under biaxial compression, the particle flow code (PFC) is first used to study the effect of the micro-parameters of the parallel bond model on the macro-parameters. Combined with the conventional triaxial compression test of intact granite, the meso-parameters are calibrated. The mechanical properties of the sample with prefabricated double fractures (upper fracture ① and lower fracture ②) under confining pressure are simulated with the set of parameters. The results show that the PFC code and the calibrated parameters can better simulate the failure of the complete samples. As the confining pressure increases, the peak strength and elastic modulus of the double-fractured rock sample increase. When the angle α₂ between the lower fracture ② and the horizontal is 90°, both of them reach the maximum values. Under different α₂, the simulated crack evolution of each rock sample goes through three stages of crack initiation, development and stabilization. With the decreasing confining pressure and the increasing axial stress, the damage of the force chains between particles becomes more severe. Due to the difference in the concentration and distribution of the tensile force chains, the cracks along the length of the horizontal fracture propagate along the axial direction, and the penetration of the two fractures presents different ways.