In order to study the mechanical properties and damage evolution of fissured rocks under the influence of microstructure caused by inhomogeneous mineral crystals,a grain-based model considering the influence of mineral crystal structure was developed by combining the results of mechanical tests on granite. An empirical model of peak stress under the influence of the dual factors of circumferential pressure and fissure inclination was established by carrying out the compression numerical modeling of fissured granite with different peripheral pressures,and the rup-ture mechanism of microcracks was elucidated on a microscopic scale. The results show that with the increase of fracture inclination angle,the compressive strength of granite exhibits a first decrease and then increase trend,with the lowest strength observed at an inclination angle of 31.8° under no confining pressure. During the stress loading process,the microcrack evolution in granite is spatially localized. Intergranular tensile cracks are randomly distribu-ted within the granite sample,whereas transgranular tensile cracks primarily congregate near the fracture surfaces during the crack propagation stage,accompanied by macroscopic failure. With the increase of the peripheral pres-sure,the total number of mineral cracks gradually increased,and the proportion of the crystal-piercing tensile cracks in the total cracks increased significantly,and tensile transgranular cracks accounted for 36.1％,45.0％,48.3％ and 51.4％ of the total number of cracks at the peripheral pressures of 0,10,20 and 30 MPa,respectively. The strength characteristics of non-homogeneous fractured granite are affected by the spatial distribution of mineral matrix,and orthoclase prevents the expansion and aggregation of microcracks. Specimens with V-shaped macroscop-ic cracks under the influence of non-homogeneity have the higher peak stresses when compared to granite with a sin-gle shear cross section.
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