Numerical research on the dynamic rock-breaking process of impact drilling with multi-nozzle water jets

Based on the arbitrary Lagrangian-Eulerian finite element method (ALE-FEM), a coupling model for simulating the rock mass destruction process under the impact of a high-pressure water jet was established. Through the analysis of multi-nozzle jets’ impact on rock surface stress changes, the process of rock breaking and pore formation, and the rock breaking dynamic damage evolution, the mechanism of rock breaking by multi-nozzle jets was revealed by analyzing the stress distribution and dynamic damage of the rock mass during the impact process. The results show that nozzle jets with different inclination angles exhibit different rock breaking methods, which are mainly tensile failure and radial shear fracturing caused by the impact of the water jets. Rock breaking using multi-nozzle jets can be divided into four stages: the elastic deformation stage, the plastic deformation stage, the micro-fracture stage, and the complete failure stage. Based on the spatial-temporal evolution of the damage, the damage depth and scope of rock mass caused by multi-nozzle jets with different tilt angles are different. The results of this study provide a theoretical basis for the effect and optimization of the impact of multi-nozzle jets on rock breaking.