Abstract

Rockburst and methane prevention are methods of rock mass destruction. The use of explosives can reduce these hazards in the immediate bore hole. Currently in the Central Mining Institute intensive research in creating new charges explosives and blasting methods which weaken rock mass is underway. One condition of effective rock mass destruction is intensive rock cracking. The effectiveness of such preventions methods dictates activity destruction and penetrating explosive gases. A complex testing device was designed and constructed for the assessment of dynamic pressure increase of explosive gases. This allows confining pressure in the explosive material's surroundings to be changed. This article presents the complex testing device and the results of confining pressure influence on explosive dynamics. According to the authors the results open new possibilities for the use of explosives, creating new charge explosives and their methods of use.

1. Introduction

In mines in which rock bursts and methane hazards were found, drilling technology and explosives are used for local destruction of rock mass in order to obtain a thick web of cracks. The radius of the cracks, i.e. permanent consequences of the explosives, explotion, mainly depends on rock resistance, the kind of explosives used, the construction of the charges, and the concentration of explosive per meter hole blasting [4].

Very strong rock destruction is carried out only in the immediate vicinity of the blasting hole. This is proven by the results of in situ work that indicates that this destruction is limited to a few diameters of blasting hole. Respectively, a wider range of permanent causes of detonation is gained using very strong explosives. But, still in this case the widest distance of a gap is limited to about 3–4 meters from the shot-hole [2, 4, 5, 10, 11]. Gaps of such distances determine the effectiveness of mining hazard prevention that require rock destruction.

The use of mining explosives guarantees the production of a vast network of subsurface cracks only in the case of a dense network of blast holes. It is necessary for methane drainage of the deck before exploitation. However, due to the power of explosives approved for use in methane hazardous conditions it is difficult to implement. Effective methane drainage deck requires its destruction at a level similar to the form of excavated material from the wall. Such a strong fragmentation deck blasting technique would require large expenditures for blasting and due to its current cost, this is economically unjustified. With this in mind, and its common usage in underground mining blasting techniques, the Central Mining Institute has begun research to develop new techniques for stimulating seam for methane drainage whilst cutting the exploitation field. This is possible as a result of producing vast and targeted zones of intense fracture. As a result, the priority of this research is to develop a new construction of explosives dedicated to specially prepared blasting holes [6]. The preparation of blasting holes is performed by a series of disk-shaped slots. At the moment of explosion, a slot which has a much wider range than gained by traditional blasting methods is created. In the case of the sequenced detonation of charges in the hole in which the disk-shaped slots have been inserted, the range and intensity of the slots will be greater in comparison to those used with an instant charge. The sequenced detonation of charges in a hole is connected with use in conditions of growing explosive gas pressure. Developing such an explosive technique requires tests which give opportunity to evaluate detonators' and highly energetic materials' working in the conditions of growing confining pressures.

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