Mesostructure failure mode of compacted rock medium in deep strata

The mesoscopic mechanisms of a deep rock mass under high stresses exhibit significant influence on its mechanical behaviors. The mesostructural features and their variations with depth can more accurately predict the macromechanical properties of the deep rock mass. To study the mesostructural changes of the deep hard rock and their correlation with the macroscopic mechanical properties, granite over a depth of 1000 m was studied, and the mineral composition, particle size and particle shape of the rock were statistically analyzed. A model of the granite mesostructure was established to analyze the effects of particle size, porosity and microfracture density on the mechanical properties of the rock. The experimental results show that there is no significant change in the composition of granite in the depth range of 1000–2000 m, but with the increase in depth, the size of rock particles decreases and the distribution characteristics of particle shape show differences. In addition, the discrete-element simulation results show that the decrease in particle size, the increase in porosity and the increase in the density of microfractures will lead to a decrease in the compressive strength of the rock. The research results provide testing data for studying the changes in the mechanical properties of deep rocks from a mesoscopic perspective.