The effect of in-situ stress on blast-induced rock fracture and damage zone

The pervasive demand for dynamic rock breakage has cast a new light on the potential challenges involved in blast-induced underground excavations with complex geological conditions. Due to the complexities and highcost issues associated with field tests, the finite-discrete element method (FDEM) is adopted in this study to explore the evolution of blast-induced damage zone, including the extent of the crushed zone and the propagation of tensile fractures. The influence of different durations time and peak pressure of blast loads, as well as the magnitude and anisotropy of in-situ stress are considered. The consistency and reliability of the numerical model are calibrated against the results obtained from test measurements. It is observed that the extent of damage zone shows a linear correlation with the duration of the blast load. A longer blast wave duration increases the size of both the crushed and cracked zones. The peak pressure of the blast load significantly influences the enlargement of the damage zone, particularly when it exceeds a critical threshold about 3 GPa. Furthermore, the length of the tensile fractures is constrained by high in-situ stress. The size of the cracked zone decreases sharply once the stress exceeds 10 MPa. The tendency of fractures propagating towards the direction of maximum principal stress is also enhanced by an increase in magnitude and anisotropy of the in-situ stress. The PPV recorded in the near field of the borehole decrease from 150 m/s to 0.5 m/s with attenuation coefficient alpha ranges from 1.526 to 1.603, which agrees well with the field tests.