Optimization and engineering application of three-dimensional multi-pore groove structure based on FEM-SPH coupling simulation

To address the issues of insufficient cycle advance and low blast-hole utilization resulting from inappropriate cut blasting layouts during roadway excavation, the empty-hole effect was employed to establish a three-dimensional cut blasting model using FEM-SPH（finite element method-smooth particle hydrodynamics）coupled numerical simulation. In the numerical modeling, the rock mass was described by the RHT constitutive model, which accounts for strain-rate sensitivity and confinement effects under high-strain-rate loading. The explosive was modeled using the Jones-Wilkins-Lee equation of state. A central charged hole was surrounded by four, five, or six empty holes with a spacing of 210 mm determined theoretically. SPH particles were applied to the central zone to capture large deformation, fragmentation, and rock ejection, while the FEM was used for the outer region to reduce computational cost. Non-reflecting boundaries were set to avoid stress wave reflection. The model was then used to simulate and analyze the influence of different cut blasting arrangements on rock mass damage, rock throw efficiency, and fragmentation patterns. Furthermore, field engineering tests were conducted in a copper mine roadway to validate the simulation results by examining the residual hole depth after blasting and the achieved cycle advance. The research findings indicate that a cut blasting layout with one central charged hole and five empty holes provides a moderate number of free surfaces, allowing for more sufficient superposition of stress waves and resulting in better blasting performance. Compared to layouts with four or six empty holes, the five-empty-hole configuration demonstrates optimal rock throw effects, with the slot cavity opening size increasing by 42.5% and 20.3%, respectively, and the slot cavity cross-sectional size improving by 52.4% and 34.7%, respectively. Field test results show that the cycle advance achieved with the five-empty-hole layout is 10.2% and 3.2% higher than that of the four-empty-hole and six-empty-hole layouts, respectively. The research reveals a nonlinear relationship between the number of empty holes and blasting effects, demonstrating that the optimal balance between stress wave superposition and energy concentration can be achieved using a moderate number of empty holes, providing a basis for the design and optimization of cut blasting schemes in roadway excavation.