To study the influence of high ground stress on crack propagation and stress propagation during deep rock blasting, a theoretical model of blasting stress wave propagation and rock damage under in situ stress conditions is developed. The implicit-display coupling method of ANSYS/LS-DYNA is used to numerically simulate the double-hole blasting of the slit charge under two-way equal pressure and two-way different pressures. A theoretical analysis shows that, in blasting under ground stress conditions, at the near end of the blasting source, the loading stress does not increase sufficiently upon unloading, and the stress wave peak value decreases with the increase in ground stress, while the opposite behavior is obtained at the far end of the blasting source. Under the two-way isostatic condition, the crack that develops at 45° deviates from the principal stress direction. Under the condition of two-way different pressures, the crack develops in the direction of θ (θ = arctan (σx/σy)) with the principal stress angle. The numerical results under the two-way equal pressure conditions show that a higher ground stress leads to a larger suppression of the blasting effect. When the ground stress is smaller, the slit charge cannot be effectively suppressed, and the cracks are biased toward the cutting direction. The numerical results under two-way different pressures show that the in situ stress has a significant inhibitory effect on the vertical cracks and that the cracks are more likely to develop in the direction of high stress after blasting. These results provide a reference for directional blasting of deep rock masses.

To address the problems with deep-hole presplit blasting intended to fracture and improve the permeability of deeply buried, soft, high-gas-content coal seams, a method using a blasthole and a relief hole drilled into the underlying rock stratum was proposed. By establishing a theoretical model for this purpose, the stress wave propagation characteristics during the blasting process were analyzed, and the working mechanisms of the relief hole and the stress transmission characteristics were investigated. The blasting of the C13-1 coal seam in the Huainan mining area under different in situ stress conditions using different blasthole–relief hole distances was simulated using an implicit–explicit coupled method and the ANSYS/LS-DYNA software. The results showed that the blasting-induced stress wave was reflected from the coal–rock interface and transformed into a tensile wave owing to the different wave impedances of coal and rock, thereby fracturing the rock and coal masses better and achieving the intended permeability improvement effect. A free surface effect was produced near the relief hole during the blasting process, which directed the stress wave to propagate in the direction of the relief hole, thereby promoting fracturing in that direction. The in situ stress inhibited the blasting-induced fracturing in the coal mass. Thus, for blasting intended to improve the permeability of deeply buried coal masses, the blasthole–relief hole distance should be reduced to achieve better fracturing. Our results have a certain reference value for directional blasting intended to fracture and improve the permeability of deeply buried, soft, high-gas-content coal seams.