<p>The excavation of deep rock masses by blasting is influenced by both the static and dynamic stresses produced by the detonation of explosives. Based on the analysis of explosive effects, formulas for explosive stress and energy have been derived. A computational model for blasting in a large cavity with four boreholes has been established. Numerical simulations were performed using the finite element analysis software ANSYS-LS/DYNA, exploring eight distinct in situ stress scenarios, which encompassed both bidirectional equal pressure and bidirectional unequal pressure conditions. The results show that explosive cracks in the four boreholes facing the cavity are denser, and the rocks in the excavation area are more fragmented. This confirms that the presence of a large cavity enhances the fragmentation effect of the blasting excavation. Given that the in situ stress is significantly lower than the pressure produced by the shock wave during detonation, its influence on the development of the fractured zone is minimal. However, it significantly influences the length and morphology of the cracks. In the blasting of rock masses with high in situ stress, the distance of crack propagation between boreholes diminishes with increasing levels of in situ stress. The cracks predominantly extend in the direction of the maximum principal stress. Therefore, arranging the boreholes along the direction of the maximum principal stress and reducing the spacing between boreholes is beneficial for connecting and penetrating the cracks between boreholes, resulting in a better blasting excavation surface.</p>