Effects of biaxial confining stress on rock fragmentation and energy utilization in straight and empty hole blasting

The global mining industry, particularly deep high-stress hard-rock mining, confronts prominent challenges of massive energy consumption and low crushing/grinding efficiency. Optimized blasting, as an alternative to grinding, effectively reduces energy usage and improves transportation efficiency. Despite extensive research on the effects of confining stress to cut blasting, studies focusing on fragmentation characteristics of deep confined blasting remain scarce. This study integrates theoretical analysis, similarity model tests, and SPH-FEM simulations to investigate fragmentation size distribution and energy dissipation under varying confining stresses. Results show that the Swebrec (SWE) function achieves superior fitting to fragmentation data (goodness-of-fit > 0.95). With increasing confining stress, the fractal dimension of specimens increases (ranging from 2.16 to 2.42 in model tests), while fragmentation energy decreases—55.23% lower under high confining stress than no confining stress in tests, and 50.61% lower at 40 MPa than 0 MPa in simulations. The ratio of fragmentation energy to blasting energy is 2%-10%. Distinct from previous studies emphasizing confining stress macro-effects on cut blasting, this work explores fragmentation distribution functions and energy under biaxial confining stress, providing valuable insights for blasting efficiency evaluation and promoting energy conservation and emission reduction in post-mineral processing.