Innovative cut blasting method for rock excavation at depth based on numerical simulation and field tests

Abstract

Drilling and blasting (D&B) has long been an essential technique in rock excavation, particularly in drift mining, where it is frequently employed due to its high efficiency. As mining depths increase, maintaining the efficiency of D&B under high ground stress has become a significant challenge. Cut blasting, the initial stage of D&B in drift mining, plays a critical role in the overall blasting effectiveness. This paper presents an innovative cut blasting method that effectively balances rock fragmentation and cavity excavation. Numerical simulations were performed using LS-DYNA to analyze the cutting performance of the original and the proposed method under various ground stress conditions. The results show that the new method exhibits significant advantages in rock fragmentation, cavity excavation, and energy utilization even under high ground stress conditions. Subsequently, several numerical models were developed to investigate the effect of hole spacing on the cut performance of the proposed method. The findings reveal that although increasing the hole spacing can enlarge the cavity size and provide more free surface space for subsequent blasting, too large spacings lead to a marked decline in cut efficiency. Furthermore, this study explored the impact of blasthole depth on cutting performance of the proposed method. When the hole depth increased from 2.0 m to 2.4 m, the cut efficiency improved significantly, however, further increases in depth do not result in a noticeable gain in cavity volume due to the strong clamping effect, indicating that more explosive would be required for deeper blasting. Based on these findings, recommended values for hole spacing and hole depth are provided. Finally, field tests demonstrate the success and superiority of the proposed method, which can serve as a valuable reference for drift mining at depth.