Investigation on the Impact Mechanism of Fracture Geometric Properties on Rock Fracture Toughness and Energy Release

Granite strata is important for the construction of underground water - sealed petroleum storage caverns, and the distribution of fractures in the surrounding rock of the caverns is a crucial factor affecting the water - sealing effect of the caverns. In order to investigate the mechanical properties and energy evolution of the rock body in underground water-sealed petroleum storage caverns, compression test of granite, obtained the macroscopic parameters and damage modes of granite have been carried out; a numerical model is established by using PFC ^2D to study the numerical test of the uniaxial compression of granite under the conditions of different slit inclination angles and lengths, and to analysis the mechanical properties and the evolution of the energy damage. The research results show that the inclination angle and length of fractures have a significant impact on the failure mode of rock, the energy release process and the development height of cracks. The failure mechanism is mainly manifested as a shear-dominated and tension-assisted shear-tension failure mode; when the fracture inclination angle is 0°, granite is the easiest to fracture, and with the increase of the fracture length, the macro cracks and the degree of damage of the specimen reach the maximum when the fracture inclination angle gradually decreases (60°-30°-15°). In addition, the smaller the YU value, the greater the released energy, and the number of macro cracks and the degree of damage also increase, which is more conducive to the generation of cracks. The research results can provide a theoretical basis for understanding the rock mass failure and safety problems in excavation of underground water-sealed petroleum storage caverns.