Study on Optimization of Blasting Parameters for Burn Cut with Multiple Relief Holes

To address critical technical challenges in the -450 m level middle roadway blasting of an iron mine, including excessive blasthole quantities, difficulties in enhancing advance per blast cycle, and low blasthole utilization efficiency, this study proposes and develops an optimized multi-blasthole burn cut blasting design. The proposed scheme aims to improve roadway excavation footage by simultaneously reducing the number of required blastholes and enhancing cut-blasting performance. Firstly, theoretical calculations were performed utilizing rock fragmentation range theory, rock breakage expansion space effects, and relief hole concentration effects, establishing a preliminary center-to-center distance of 24.4 cm between the central cutting hole and relief hole. Subsequently, a numerical model for multi-hole cut blasting was developed using ANSYS/LS-DYNA. Through comparative analysis of stress contours, damage distribution patterns, and fragmentation characteristics under various hole-spacing and relief-hole configurations, the optimal parameters for the relief-hole cutting scheme were determined as follows: 25 cm spacing between central cutting holes and relief holes, with 5 relief holes. Field trials conducted with these theoretically and numerically optimized parameters demonstrated significant improvements, achieving an average advance of 2.3 m per blast cycle and increasing blasthole utilization to 92%. Compared to the original blasting design, the optimized scheme demonstrates measurable improvements: a 0.2 m advance per blast cycle, a 10% reduction in required blastholes, and an 8% improvement in hole utilization efficiency, collectively resulting in significant tunneling productivity gains. These findings validate the scientific rationale and practical viability of the multi-hole burn-cut blasting optimization approach, establishing both a theoretical framework and operational guidelines for refining blasting parameters in comparable iron mine roadway development projects.