An improved method for calculating the peak explosion pressure on the borehole wall in decoupling charge blasting

The peak explosion pressure acting on the borehole wall in decoupling charge blasting was investigated by employing analytical, numerical, and experimental approaches. The theoretical solution of the pressure increase ratio after collision between an air shock wave and an elastic wall was derived to analyse factors influencing the peak explosion pressure acting on the borehole wall. A numerical simulation of fluid–solid coupling using a dynamic finite element method was used to study the peak explosion pressure under the conditions of three types of rock, two common explosives, ten common radial decoupling coefficients, seven radial decoupling coefficients for experimental verification, and two axial decoupling coefficients. The results of the theoretical analysis and numerical simulation were used to obtain a calculation formula for the pressure increase ratio; this formula mitigates the shortage of the unreasonable value range and the uncertain value present in the previous methods. Further, an improved method for calculating the peak explosion pressure acting on the borehole wall in decoupling charge blasting was proposed by referencing an isentropic expansion and adiabatic expansion model for calculating the borehole pressure; the effect of the axial decoupling charge coefficients on the peak explosion pressure acting on the borehole wall was considered. Furthermore, the experiment results obtained by placing explosive cartridges in steel tubes to simulate decoupling charge blasting and the calculation results obtained using the improved method proposed in this paper show good agreement, thereby verifying the reliability and accuracy of the improved method. This research provides an improved method for determining the peak explosion pressure acting on the borehole wall as the key parameter of blasting design in contour blasting and a numerical simulation related to the blasting vibration response of non-fluid–solid coupling.