Mechanical mechanism of control holes in guiding the directional propagation of blast-induced cracks under in-situ stress conditions

The rational design of control holes is crucial for achieving directional propagation of blast-induced cracks. Previous studies have overlooked the influence of the secondary stress field around the control holes on crack propagation. To address this issue, this study investigates the mechanical control mechanism by which control holes guide blast-induced cracks under in-situ stress conditions. Experimental results reveal that the guiding effect depends on the orientation of the in-situ stress conditions. Improper arrangement of control holes may lead to a secondary compressive stress field around them, which can inhibit crack propagation. Numerical simulations further show that when control holes are arranged in groups and the line connecting the blast hole and the control holes forms a 45° angle with the maximum and minimum principal stresses, the blast-induced cracks can effectively connect the control holes, achieving directional propagation.