The generation and the role of the energy concentration effect are described in this paper, and the energy concentration effect, the rock fragmentation mechanism for wedge-shaped explosive are discussed. Through some model tests, the result of energy concentration blasting is obtained when the material of energy concentration cover is stainless steel and the conical angle is 60°. Compared with the result of regular blasting, the conclusion can be drawn that energy concentration blasting with wedged charge is characterized by the small number of needed bore holes, the concentration of energy, the strong directionality, the great penetrating force, and the effectiveness of directional rock fragmentation.
In some projects of mine construction, hydraulic construction, slope engineering, and in specific areas with complex geology, the special rock drilling and blasting techniques should be adopted so that the flatness and smoothness of the walls of tunnel and slope could be guaranteed, in this way, over break during excavation could be reduced and the surrounding rock and slope could be kept in a stable condition (Zhang, 1988; Henrych, 1979). A number of field tests concerning rock blasting have been conducted to investigate the corresponding effects (Huang, 1993; Jiao, 2005; Huang, 1988). In the present paper, the energy concentration effect produced by the blasting of wedge-shaped explosive as well as the application of the special explosion energy concentration technique is described; some useful conclusions are drawn from the study.
The energy concentration effect of the explosive detonation is a special case of the direct action of the blast. When the explosion energy concentrates into one direction, the local fragmentation by blasting can reach several times or even tens of times of the fragmentation by conventional explosive blasting. The energy concentration of the explosion is produced as follows: A hollow charge is formed on a certain surface of the explosive. After initiation, the explosion products on the surface of the concave cavity of the hollow charge fly outwards basically in the direction perpendicular to the charge surface. As a result of the interaction of air-flow micro portions, at a specific distance from the charge bottom surface, the air-stream has the smallest diameter, the greatest velocity and the largest density. If some metallic or non-metallic charge covers are placed on the concave surface of the hollow charge, the energy concentration effect increases greatly. This is because the extremely high pressure of the explosion products causes the speedy inward deformation of the charge cover. The micro portions of the cover, which is symmetrical to the charge axial line, are compressed simultaneously to the axial line. The detonation wave firstly reaches the top of the cover, and the micro portions of the charge cover near the cover top are 948 firstly dashed against each other along the axial line and become relatively compact. In the deformation process the jet efflux is formed.
