Study on the effects of double-primer initiation on rock damage and stress evolution

The initiation method significantly influences the fracture mechanism of rock blasting during the blasting process. This study employs Computed Tomography(CT) scanning technology, multi-fractal theory, and numerical simulations to investigate the collision and energy-focusing effects of detonation waves during double-primer initiation within blastholes through field applications. It reveals the impact of initiation point locations on the blasting effectiveness of rock fragmentation. The results indicated that the multi-fractal spectrum width Δα of specimens subjected to double-primer initiation exceeds those with single initiation points, indicating enhanced rock fragmentation and a higher degree of rock damage due to the superposition and collision of explosive stress waves. This superposition alters the spatial distribution and allocation of explosive energy within the blastholes after detonation, improving the utilization efficiency of explosive energy. In addition, the mutual collision of detonation waves increases the wavefront pressure at the collision points, enhancing the local rock fragmentation effect. Numerical simulations show that the peak stress in the charged area is significantly greater than in the uncharged area, and at the same measurement point, peak stress is lower in specimens with single initiation points compared to those with double initiation points. In addition, adjusting the positions of initiation points within blastholes can improve post-blast stress distribution.