A novel theory of abrasive water jet rock breaking under triaxial stress and the evolution mechanisms of rock damage

Deep Earth engineering is essential for national development, but rock fragmentation in deep, hard formations remains a significant challenge. Abrasive water jet (AWJ) technology shows considerable promise, yet current models often overlook geostress effects, limiting its effectiveness. This study proposes a new criterion for AWJ rock breaking under triaxial stress, combining the Alekseevskii–Tate (AT) long-rod penetration model, jet theory, and a modified spherical cavity expansion model. The mechanical behavior of the elastic, cracking, and crushing zones is analyzed, and a penetration depth model under triaxial stress is developed. Coupled SPH–FEM simulations are used to investigate how stress affects jet-induced stress waves, rock damage, and energy evolution, thereby clarifying the failure mechanism in rock breaking. Results show that stress significantly influences wave propagation and damage patterns: at 0 MPa, waves expand freely; at 25 MPa, wave expansion is restricted, reducing damage; at 40 MPa, waves concentrate, increasing damage. Numerical and theoretical results show an average error of 6.59 %, confirming the model's accuracy. As stress increases, rock quality decreases rapidly at first and then more slowly, with damage following a quadratic function. Compared to 0 MPa, total energy drops by 19.75 % at 15 MPa and rises by 76.31 % at 40 MPa. Damage in the jet zone exhibits brittle failure, unaffected by stress; while stress mainly influences damage in the crushing and edge zones, suppressing damage at low stress and promoting damage at high stress. These findings deepen the understanding of the damage evolution of rock under AWJ cutting, providing a theoretical basis for optimizing the parameters of AWJ grid cutting in deep rock masses.