Research and Application of Presplitting Blasting Construction Technology Using Coupled Charging with Wide Hole Spacing and Low-energy Bulk Emulsion Explosives

Presplit blasting serves as an essential technique for maintaining optimal excavation profile integrity and enhancing rock mass stability in open-pit mining operations. Traditional presplit blasting techniques are plagued by excessive drilling requirements, prohibitive construction expenses, and suboptimal operational efficiency. To address these technical and economic constraints, this study introduces and comprehensively examines an innovative technique: wide-spacing presplit blasting with low-power, bulk-loaded explosives and a coupled-charging configuration. This investigation focuses on the engineering of metamorphic sandstone slopes at the 380 platform on the left side of a specific open-pit mining operation, which serves as the research context for the study. This study addresses the critical technical challenges in implementing the novel method under conditions of high rock hardness (strength factor f = 12 ~ 16) and intact rock mass structure, focusing on two key aspects: the diminished superposition effect of stress waves and the enhanced difficulty of crack coalescence resulting from significantly increased borehole spacing (18 ~ 25 times the borehole diameter, e.g., 3.0 m spacing for a 140 mm diameter holes); and the stringent requirements for precise energy distribution and optimal utilization of the “air wedge effect” imposed by the unique charging configuration that combining bottom-coupled charges with upper decked air gaps. Based on stress wave propagation theory and explosion gas quasi-static pressure mechanisms, this study develops an optimized blasting design featuring bottom-coupled charges for effective crack initiation combined with upper decked air gaps to facilitate crack propagation, while employing an electronic detonator-based precision delay initiation network to ensure prioritized presplit hole detonation and coordinated inter-hole stress field development. Field application demonstrated outstanding performance metrics: the technique achieved an average half-hole preservation rate of 85.2% while maintaining presplit surface deviation within 8.7 cm. The innovative approach yielded substantial economic benefits, including a 50% reduction in drilling volume, an 84% cost saving through electronic detonator substitution for detonating cord,and more than fivefold efficiency gains via bulk explosive loading systems, collectively reducing comprehensive costs per square meter by 46.6%. This advanced wide-spacing, low-power, bulk-loaded emulsion explosive coupled charge presplit blasting technology represents a technically sophisticated, economically viable, and operationally reliable solution that effectively addresses conventional method limitations. The successful implementation establishes a replicable framework for slope control blasting in analogous open-pit mining environments, demonstrating significant potential for widespread engineering applications.