The Propagation Pattern of Smooth Blasting Cracks under Conditions of Increasing In-Situ Stress

In deep rock mass engineering, the interaction between in-situ stress and blasting load significantly influences the propagation behavior of blast-induced cracks and the quality of blasting wall contour. Based on the Dahongshan Copper Mine tunneling project, this study employs finite-element numerical simulation to investigate the evolution characteristics of crack propagation under varying in-situ stress conditions. The results indicate that within the 0–12 MPa range, increasing in-situ stress suppresses the development of transverse cracks, reducing their length by 37.19%, while shifting longitudinal crack propagation toward the free face. When the in-situ stress exceeds 12 MPa, transverse cracks gradually disappear, and the longitudinal crack length decreases by 43.63%, accompanied by a transition of the blasting wall contour from concave to convex. Further analysis also fitted the relationship curve between the peak maximum principal stress and the bursting center distance, used 18 MPa as the benchmark for determining the dynamic tensile strength, and analyzed it in combination with the grayscale image of the wall after on-site blasting to verify the influence law of the ground stress on the crack extension. These findings provide theoretical insights and technical support for blasting design and construction in complex stress environments.