Abstract: The internal pore structure and mineral composition of rocks are crucial factors contributing to the instability and failure of rock masses. To investigate the influence of pore structure and mineral composition on crack propagation, a grain based model (GBM) of rock with varying pore structures and mineral compositions was established using the particle flow code (PFC). This study examines the effect of pore size on crack evolution and the propagation behavior of cracks within different minerals. The results indicate that as the short-long axis ratio of pores increases, both the uniaxial compressive strength and elastic modulus of the rock first decrease and then increase, while the degree of rock damage initially increases and subsequently decreases. The most severe failure occurs at the short-long axis ratio of 0.8. With the increase of the short-long axis ratio of pores, the number of internal cracks first decreases, then increases, and finally decreases again. The number of tensile cracks follows a similar trend, whereas the number of shear cracks remains largely unchanged. During the failure process of the rock, intragranular tensile failure is dominant, followed by intergranular tensile failure, while shear failure is relatively rare in both intragranular failure and intergranular failure. Crack propagation behavior in sandstone matrix, clay, and mica is most significantly influenced at the short-long axis ratio of 0.6, whereas the effect on quartz and feldspar is most pronounced at the short-long axis ratio of 0.2. The research results can provide reference and research basis for solving the instability failure problem of rock mass with porosity structures.

Key words: instability failure, crack propagation, mineral composition, pore structure, numerical simulation