Study on damage mechanism and influence of confinement pressure on cracking rock mass under cut-and-break blasting load

Aiming at the unclear internal damage and fracture evolution of rock mass caused by slit blasting under the action of ground stress in deep roadway, a theoretical model of slit blasting is established to study the mechanism of slit blasting to crack rock mass, and the influence of ground stress on slit blasting load to crack rock mass is analyzed theoretically. By introducing the corrected rock constitutive model into the numerical simulation software, the three-dimensional numerical model of double-hole slit bl asting under different confining pressures is established. The results show that: compared with ordinary blasting, the tensile stress value of slit blasting on rock mass in the slit direction is 2. 15 times that of ordinary blasting, but only 31% in the non-slit direction. Confining pressure has little effect on the crushing zone near the two-hole slit blasting, but has great effect on the subsequent crack propagation speed and length. Confining pressure does not change the variation trend of stress between holes in double-hole slit blasting, and there are attenuation and superposition regions between holes, but it affects the stress peak value of each point between holes. Confining pressure affects the damage of rock mass under slit blasting load, especially in the direction of maximum principal stress, and when the slit direction is consistent with the direction of maximum principal stress, the directional effect of blasting is the best. Finally, the 3D numerical model of blasting excavation in deep roadway is established to explore the influence of ground stress on rock mass damage during blasting. The results show that in the excavation area of deep roadway, the smooth blasting technology of slit blasting and delayed initiation can effectively improve the quality of pre-cracking excavation of rock mass, which has an important guarantee for the stability of rock mass.