Theory and numerical simulation of deep hole cut blasting based on dispersed charge and staged detonation

Abstract

The rock drilling and blasting method is the most commonly adopted method for rock roadway excavation in China, where cutting efficiency is the key factor affecting the excavation speed. The conventional wedge-shaped cut blasting is not suitable for deep hole blasting since the method requires the explosives to be concentrated at the bottom of the borehole, resulting in uneven fragmentation of the upper rock and difficulty in throwing the bottom rock. In addition, the cut area is small, and the range of cavity created after cut hole blasting cannot meet the needs of large section blasting tunneling. This present study proposes an efficient method for charging and detonation inside and between boreholes called disperse charge and staged detonation (DCSD) cut blasting technique. The DCSD cut blasting and traditional wedge cut blasting models were established and compared using the smooth particle hydrodynamics-finite element method (SPH-FEM). The results shows that the DCSD model reduces the minimum resistance line of rock blasting and creates a new free surface, promoting the throwing of the bottom rock mass and the overall rock mass failure. Furthermore, the cutting efficiency is defined to quantitatively analyze the influence of different parameters on the cutting effect. The cutting efficiency of the DCSD model with dispersed charge is 21.89% higher than that of the blasting model with continuous charge. The cutting effect is at its greatest for the three types of ε designed for the study, when ε = 0.5. The increase in hole depth reduces the cutting efficiency marginally, although it is still higher than that in the traditional mode. Finally, the successful application of digital electronic detonator and DCSD in domestic rock roadway blasting construction verifies the applicability of DCSD and provides a reference for subsequent projects involving rock roadway deep hole drilling and blasting construction.