The effect of detonator placement on rock fragmentation by blasting was studied in the Kevitsa open-pit mine. Considering rock mass properties, explosives properties, and blast parameters, a comprehensive analysis of 37 production blasts confirms that the middle detonator yields finer fragmentation than the bottom detonator in the full range of investigated sizes. Meanwhile, using the LS-DYNA code, a bench model with a single blasthole was built in a three-dimensional setting. A single detonator placed at two different positions—the middle and bottom—of the explosive column was analyzed in this study. By analyzing principal stress states on the plane through the blasthole axial and vertical to the bench face, the numerical results show that the middle detonator creates a stress concentration area near the bench face characterized by triaxial tension, while the bottom detonator does not. Furthermore, the middle detonator generates a larger stress concentration area with biaxial tension near the bench face than the bottom detonator. Considering that triaxial and biaxial tensions are more favorable to fragmentation than uniaxial tension, it can be concluded from simulation results that these areas with triaxial tension and biaxial tension in the middle detonator are a significant factor contributing to achieving better fragmentation, compared to the bottom detonator. The middle detonator position has replaced the bottom detonator position in the Kevitsa mine.
In this paper, the design method of a laser pyrotechnics system for insensitive ammunition is introduced. The functional architecture, product structure and electromagnetic protection of the semiconductor laser included in the system are designed. At the same time, the principle, structure, function and advantages of the optical safety components of the magneto-optic switch are introduced in detail, and a blunt laser ignition tube is developed, the composition and charge of the explosive are described, and the slow roasting performance of the laser ignition tube is deeply studied. The research done in this paper can effectively improve the performance of the laser fire engineering system in the aspects of safety, reliability and electromagnetic environment adaptability, so as to develop a laser ignition system prototype with strong electromagnetic interference resistance and meet the requirements of insensitive ammunition, which has important military application significance.
Tianzhu Shi Tianzhu Shi, Zhengfeng Xie Zhengfeng Xie, Fuyong Wu Fuyong Wu
et al.
: A series of Schiff base chemosensors (M1, M2 and M3) were designed and synthesized based on conjugated fuse heterocyclic aldehyde thiosemicarbazone. Optical properties of fluorescent probes M1, M2, and M3 toward various nitro explosives 2,4-dinitrotoluene (DNT), o-nitrophenol (ONP), p-nitrophenol (PNP), phenol (PhOH) and nitromethane (NM) were investigated, M1, M2, and M3 could selectively recognize PA with an obvious color change and fluorescence quenching, even in the presence of other coexistence nitro explosives. The detection limit of M1, M2, and M3 were 1.18and#215;10-7 M, 1.13and#215;10-7 M, 1.09and#215;10-7 M, respectively.