Research on the theory and method of reduced-hole blasting for large cross-section tunnel based on explosive energy dissipation

The traditional tunnel drilling and blasting method places cut holes at the lower center of the excavation face, resulting in an excessive number of blasting holes. With the continuous increase in cross-section area, this design concept can no longer meet the requirements of safe and efficient tunnel boring for large cross-section tunnels. This paper puts forward the theory and method of reduced-hole blasting for large cross-section tunnels, as an alternative to the traditional drilling and blasting method of the "more holes, less charge" design concept. Based on the explosion energy dissipation law and rock's critical crushing energy dissipation characteristics, the calculation method of the extrapolation distance of the wedge-cut holes is given. The optimum extrapolation distance of the wedge-cut holes was verified using numerical simulation and field tests. The results show that the number of drilling holes can be reduced by about 15.8% using the theory and method proposed in this paper, and at the same time, the damage of retained rock can be effectively controlled. The results of this study can provide a reference for the design of blast network parameters for similar large cross-section tunnels. This paper put forward the theory and method of reduced hole blasting (RHB) for large cross section tunnels, the number of blasting holes was reduced by an average of 15.8%. This paper gave the wedge-cut hole extrapolation distance calculation method based on the explosion energy dissipation law and rock's critical crushing energy dissipation characteristics. This paper proposed a computational expression for energy dissipation under coupled in-situ stress and blast loading, determined the critical crushing energy dissipation density of gray sandstone under different combined dynamic and static loading conditions.