Influence of Slot Angle and Hole Spacing on Directional Crack Propagation in Sandstone with V-Shaped Slotted Blastholes

To improve the directional propagation of blasting-induced cracks in sandstone and reduce over-excavation, under-excavation, and surrounding-rock damage caused by conventional circular blastholes, circular and V-shaped slotted blasthole models were established in LS-DYNA. The ALE fluid–solid coupling algorithm was adopted to investigate the effects of slot angle on the effective stress field, crack propagation pattern, and crack control index. The stress field theory at the tip of the V-shaped slot was further used to explain the directional cracking mechanism. On this basis, a two-hole V-slotted blasting model is established to analyze the influence of hole spacing on crack penetration. The results show that the V-shaped slot can form an obvious stress concentration at the tip, which changes the crack from approximately isotropic extension to directional extension along the direction of the slots. Under the present two-dimensional homogeneous sandstone model with simultaneous initiation, the 60° slot angle corresponds to the highest peak effective stress and crack control index. For the synchronized two-hole model, when the hole spacing is 70–90 cm, namely the ratio of hole spacing to blasthole diameter is approximately 14–18, the inter-hole crack penetration effect is better, and the proportion of effective cracks along the slot direction is about 80%. These results provide baseline numerical references for sandstone-controlled blasting parameter design under the modeling conditions of this study.