This study systematically investigated the synergistic relationship between matrix temperature and sodium nitrite concentration to resolve density unevenness and explosive power instability in site-mixed emulsion explosives caused by the mismatch between matrix temperature and sensitizer (sodium nitrite) concentration during production. Using an orthogonal experimental design, matrix temperature gradients ranging from 40℃ to 70℃ and sodium nitrite concentration gradients ranging from 1.2% to 2.8% were systematically established. Multiple sets of comparative tests were conducted to comprehensively examine the impact of these two factors on the density of emulsion explosives. The experimental results demonstrate that matrix temperature plays a critical role in determining the foaming reaction rate, with elevated temperatures markedly accelerating the reaction and, consequently, the foaming process. However, this acceleration often leads to excessive foaming, consequently reducing the explosive density. In contrast, lower temperatures slow the reaction, often resulting in insufficient foaming, which increases explosive density and adversely affects blasting stability. Additionally, the concentration of sodium nitrite, acting as the sensitizer, directly influences both the foaming efficiency and the structural stability of the bubbles. For different matrix temperatures, there is an optimal concentration range to achieve ideal explosive density and detonation performance. Based on comprehensive experimental data, this study developed practical guidelines for sodium nitrite proportions across various matrix temperature ranges. These guidelines explicitly recommended specific sensitizer concentrations for low-to high-temperature conditions, providing quantitative references for field applications. Field validation confirmed that implementing this matching table and associated control techniques substantially enhanced the accuracy of emulsified explosive density regulation. This improvement not only boosted the effective release of explosive energy but also mitigated safety risks, including density-related misfires, resulting in overall optimization of both blasting performance and operational safety. This study's findings offer valuable theoretical insights and practical applications for enhancing quality control in field-mixed explosives and systematically improving blasting performance.

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.

There was a special working face with an ultra-high bench and a large resistance at the 410 platform of a mine in Qingyuan city, which required one-time blasting. This working face had a bench height of 30m, a length of 80 m, and a face angle of 45°~80°. Due to the large bench height, small face angle, and the different face angles of the upper and lower parts, it was difficult to conduct the blasting construction. Before blasting design, the RTK measuring instrument and total station were used to measure the topography of the detailed working face, and then calculate the slope angle of each position of the face according to the topographic map. According to the rock properties, the construction experience and the drilling rig type, the powder factor and blast hole diameter were determined. Based on the above results, the toe burden, drilling angle, depth and spacing of the first row of blast holes were then deigned. Similarly, the burden, drilling angle, depth, spacing of the following rows of holes were also determined. After the hole parameters were determined, the charging structure was designed according to the burden of each row of holes, the rock volume of each hole, powder factor, and the principle of uniform blasting action. Finally, the initiation network was designed by the software of 3Dmine based on the direction of rock movement and the earthquake-proof requirements of the protected objects. During the construction process, the key links such as hole layout, hole depth measurement, drilling, charging, and network connection were strictly controlled, and positive results were obtained after blasting.