Abstract: The rock crushing process involves the variation of multiple variables (stress, strain, porosity, etc.) and generation, expansion and accumulation of cracks. It is an effective way to study the mechanism of rock consumption. In order to improve the rock granule model in the existing literature, the internal characteristics of rock materials should be considered. In order to characterize non-uniform distribution and accumulation of particles inside the studied rock, rock axial crushing experiment and rock lithofacies analysis were carried out. On this basis, a multi-scale cohesive particle model conforming to the internal characteristics of the real rock was constructed. According to the BPM theory of discrete elements, the mechanical relationship between the bonds of particles with different grain sizes in the multi-scale cohesive particle model was solved. It is found that the bond breaking criterion formed by the secondary particles is ≥ 2 GPa, and this criterion formed between the tertiary particles is ≥ 6 GPa. On this basis, an evolution model for simulating fragmentation of the particle model is established. By simulating the axial crushing experiment, the fracture evolution model can predict (i) the real-time changes of the bearing force on bond between the particles in the particle model from the mesoscopic point of view and (ii) the fracture sequence of the bond from the outside to the inside during the rock crushing process. It has a V shape extending from both ends of the upper surface and intersecting the middle of the rock. The rock crack characteristics simulated by the proposed method are found to be in a good agreement with the experimental results from rock axial crushing tests. The reliability of the model is verified, and the rock crushing process is analyzed from the microscopic and macroscopic perspectives.

Key words: multi-scale cohesion, particle model, breaking process, mesomechanics