## 3 Methodology
### Simulation of Explosive Detonation
To investigate the detonation characteristics of explosives under different charge structures, detonation models for air-coupled and water-coupled charges were established using identical explosive parameters. The propagation of detonation waves and the loading characteristics on the blast hole wall were then analyzed. Figure 6 illustrates the propagation of the detonation wave when air is used as the uncoupled charging medium, with uncoupling coefficients of 1.29 and 1.57. As shown in Figure 6a, the detonation wave originates at the detonation position, and the explosion energy propagates along the explosive. Due to the directional and temporal effects of the cylindrical charge's detonation process, the detonation position determines both the propagation direction of the detonation wave and the flow direction of the explosion energy, as depicted in Figure 6b,c. In the case of an uncoupled charge, the shock wave generated by the explosion reflects transparently at the interface between different media, leading to the superposition of detonation waves, as shown in Figure 6d. The difference between uncoupling coefficients of 1.29 and 1.57 lies in the timing of this superposition. When air is used as the uncoupled medium, a higher uncoupling coefficient delays the superposition of the detonation waves. This delay occurs because the wave propagation speed in a solid is greater than in air. As a result, a higher uncoupling coefficient increases the time for the detonation wave to reflect off the gun hole wall, causing the superposition of detonation waves to occur later. This delay leads to uneven energy release and reduces the effectiveness of the blasting. Figure 7 illustrates the propagation of the detonation wave in water as the uncoupled medium, with decoupling coefficients of 1.29 and 1.57. The propagation pattern is similar to that observed in air, but the differences occur due to the physical properties of the water. As shown in Figure 7d, the detonation wave originates at the ignition position and propagates along the explosive, with wave superposition occurring during the process. In contrast to air, water has lower compressibility, higher viscosity, and a faster stress wave velocity. These properties reduce the time for stress wave reflection at the blast hole wall, thereby accelerating the superposition of detonation waves. Additionally, the energy concentration at the wavefront becomes more evenly distributed during propagation. This more uniform energy release improves coupling efficiency with the blast hole wall by mitigating localized pressure peaks. As a result, using water as the decoupling medium significantly enhances blasting effectiveness. Figure 5: Blast hole wall load at two points of detonation. Figure 8 illustrates the time-history curve of the blasting load on the hole wall for water and air as uncoupled charging media. The figure shows that, with a constant explosive diameter, the peak blasting load decreases as the uncoupling coefficient increases. For a given uncoupling coefficient, the blasting load on the hole wall varies based on the charging medium. When water is used as the uncoupled charging medium, the explosion energy grows significantly faster than when air is used. This difference is due to water's lower compressibility and higher viscosity compared to air. As a result, the blasting load  
Figure 6: Detonation wave propagation of air-uncoupled charge at uncoupling coefficients of 1.29 and 1.57. Figure 7: Detonation wave propagation of water-uncoupled charge at uncoupling coefficients 1.29 and 1.57.  
is slightly higher when water is the medium, and the explosion energy is released more uniformly. This leads to better energy transfer to the hole wall, enhancing the blasting effect compared to air as the uncoupled charging medium.