Simulation of shale’s deformation and failure characteristics under triaxial compression considering mineral components

To advance the design and optimization of hydraulic fracturing technology in the efficient development of shale gas, it is crucial to reveal the mechanism by which mineral composition influences the mechanical properties of shale. On the one hand, the control mechanism of mineral composition heterogeneity on shale’s mechanical behavior is not clear. On the other hand, traditional experimental methods have significant limitations in characterizing the coupled mechanical effects of multi-mineral interactions. In this study, a numerical model is constructed using the coupled finite-discrete element method, which considers the heterogeneity of mineral composition. Through systematic triaxial compression numerical simulations, the mechanisms by which mineral composition affects shale’s strength characteristics, failure modes, and crack propagation patterns are revealed. This study reveals that larger mineral particle sizes promote fracture propagation as single principal shear fractures. In contrast, smaller particle sizes enhance interfacial effects, favoring the formation of conjugate X-shaped shear fractures. Mineral phase heterogeneity affects stress transfer pathways, initial fracture locations, and propagation directions. Increased critical damage displacement leads to more pronounced stress concentration and accelerated fracture propagation. Heightened interfacial deformation resistance results in richer secondary fracture branching, more complex fracture networks, and enhanced shale brittleness. This study provides theoretical support for developing mineral-characteristic-based fracture parameter optimization models.