Effect of Empty-Hole on Blasting-Induced Damage Evolution and Dynamic Response of Rock

Aiming at the issue that traditional perimeter blasting easily induces random crack damage in surrounding rocks, this study conducts an in-depth analysis of the damage evolution laws and dynamic response characteristics in empty-hole directional blasting by integrating elastic mechanics theory with numerical simulation methods based on ANSYS/LS-DYNA. Firstly, drawing on the theory of elastic mechanics, the mechanical mechanism was elucidated whereby empty holes generate tensile stress concentration through stress wave reflection under explosive loading, thereby controlling the propagation of directional cracks. Subsequently, by establishing a numerical model of planar double-hole decoupled charge blasting, the effects of blasthole spacing and in-situ stress field on damage evolution were systematically investigated. Finally, the dynamic variation patterns of peak stress and peak particle vibration velocity near the empty hole were analyzed. The results indicate that empty holes can significantly alter the distribution of explosion energy, guiding it to concentrate along the line connecting the blastholes, thereby effectively suppressing the initiation and propagation of unintended cracks. The directional effect of empty holes is modulated by the in-situ stress field; high in-situ stress conditions reduce the degree of tensile stress concentration in the horizontal direction of the empty hole, thus inhibiting crack propagation between blastholes. Therefore, blastholes should be arranged parallel to the maximum principal stress direction of the rock mass to maximize the directional effect and mitigate the inhibitory influence of in-situ stress. When the blasthole spacing is 11−14 times the blasthole diameter, stable directional propagation of main cracks is promoted, the development of unintended cracks is suppressed, and the control of surrounding rock damage is significantly improved. Under high in-situ stress conditions, it is recommended to appropriately reduce the reference hole spacing to 8−11 times the blasthole diameter.