A Coupled PBM-FEM-SPH Investigation of Air-Decked Charge Structures for Improved Fragmentation and Flyrock Control in Bench Blasting

Optimizing the utilization of explosive detonation energy through bench blasting is central to improving both the efficiency and safety of open-pit mining operations. However, conventional blasting geometries often produce a non-uniform energy distribution, with excessive toe burden at the bench base and insufficient crest burden near the slope top, conditions that can significantly increase the risk of flyrock. This study proposes an air-decked charge configuration to mitigate these imbalances and enhance blast performance. A coupled numerical framework integrating the Particle Blast Method, Finite Element Method, and Smoothed Particle Hydrodynamics is employed, complemented by high-speed photographic field monitoring, to examine rock fragmentation behavior and the evolution of fragment velocities under air-decked loading conditions. The results show that air-decked configurations promote a more uniform borehole pressure distribution and markedly reduce the initial ejection velocity of rock fragments along the slope, effectively suppressing flyrock generation. In particular, for top air-deck arrangements, an optimal air-deck-to-charge length ratio in the range of 27% to 36% is identified, achieving a favorable balance between fragmentation efficiency and hazard control.