Crack propagation law and optimal hole spacing of presplit blasting under high in-situ stress

To investigate the damage characteristics and crack propagation laws of rock under high in-situ stress conditions during presplit blasting, this study adopted an integrated theoretical and numerical approach to analyze damage evolution during single-hole and double-hole blasting, and to determine the optimal crack-forming spacing under varying decoupling coefficients and stress conditions. Numerical results demonstrate that fractures tend to propagate along the maximum principal stress direction, while growth along the minimum principal stress direction is suppressed and the inhibitory effect becomes more pronounced as the maximum principal stress increases. The evolution of inter-hole presplit fractures is primarily controlled by σ v . The design of a high decoupling coefficient and small hole spacing tends to generate excessive vertical cracks between boreholes and aggravate damage to the surrounding rock. Under constant stress conditions, a reduction in the decoupling coefficient causes the optimal hole spacing to progressively increase at an accelerating rate. Compared to high in-situ stress conditions, the crack zone extent varies more significantly with the decoupling coefficient under low in-situ stress levels for a constant lateral stress coefficient. A high decoupling coefficient reduces the differential influence of high and low in-situ stresses on crack propagation. Under low in-situ stress, a small decoupling coefficient markedly enhances crack growth but induces developed vertical cracks that compromise surrounding rock stability. Under high in-situ stress, a high decoupling coefficient can substantially suppress crack propagation and reduce the efficiency of presplit blasting. This study offers critical theoretical insights into the fracture propagation behavior and the optimization of borehole spacing in deep rock presplit blasting.