The Theory And Practice Research On Deep Hole Pre-split Blasting Of Open-off Cut Of Fully Mechanized Caving Face

High-strength hard roof, Joints, cracks do not develop; it has good integrity and strong self-stability characteristics; in the mining process it is easy to form a large area of roof overhang,especially the larger overhang area early recovery. Under the conditions the use of roof is caving mining; since the early period of mining goaf roof can not collapse;it easily lead top coal crushing;bracket do not take the top bracket, and face difficulties in moving frame and leakage. When suddenly a large area of collapse,they would stand a big impact destruction; While the mined out area of harmful gases, It easily lead to face gas gauge.Therefore, this site is a large area to prevent pressure problems;it doesn’t recovered during the early top coal mining, resource waste. Therefore, in the process of coal mining hard roof, it is necessary to weaken the top plate, so that it can promptly collapse, thus ensuring the face of safe production, and improving resource recovery.Studies have shown that the coal seam conditions in our country is complexity, there exists the threat of hard roof over half of mine, visible seams are hard roof is quite common. For now mechanized mining face also has a38%belong to the hard roof. Currently, most of the hard roof blasting weakening technology relies experience, and systematic study of the theory of plate weakening technology is not much.In this paper, yu wu Coal N2105face as the main object of study, the use of physical and mechanical testing laboratory, theoretical analysis, numerical simulation and field practices and other methods, has the hard roof open deep cut in the pre-split blasting theory and practice of the system Research. The main contents and conclusions are as follows:(1)Through the mine field research and data collection, and processing methods to grasp the empty area yu mu Coal mining under production conditions, roof control and management technology to provide basic data for research projects. On this basis, the N2105Coal Seam and roof and floor pilot study of physical and mechanical properties, master N2105Coal Seam and top, physical and mechanical parameters of rock bottom. N2105face old roof which umaxial compressive strength107.96MPa, tensile strength5.77MPa is a hard roof face is easy to form a large area of roof overhang during the initial mining. Therefore it is necessary to weaken the roof in advance to ensure production safety face.(2)On the basis of laboratory parameters on the resulting rock mechanics, we theoretically analysis N2105mining face hard roof Strata Behavior and security risks, and select Open Cut Deep Presplit way to weaken N2105face roof.(3)On the basis of the resulting rock mechanics laboratory parameters, through theoretical calculations we get N2105Face Deep Presplit the main parameters. The choice of mine blasting use permissible three emulsion explosives, drugs roll diameter60mm, blasthole diameter75mm, hole spacing gun7m, vertical depth of15.2m, blasthole elevation45°, borehole depth of21.5m, continuous decoupling charge, no couple coefficient1.25. each blasthole charge capacity of45kg, a charge, detonating three guns each hole.(4)Respectively, using software UDEC numerical simulate Coal N2105over yumu face that did not cut the top and cut the top in two cases blasting roof breaking down the situation. When not cut the top face, the immediate roof caving first step is21m, basic roof first weighting step45m; the face toppers, immediate roof caving step into the first12m, basic roof first weighting step becomes33m, and the initial pressure intensity decreased.(5)Develop a reasonable conclusion based on the above Cut Deep Presplit open plan and prepare a reasonable blasting process based on field experience. Finally, on-site practice. Practice shows that the use of the research results, the effective prevention of early mining face is a large area of the roof to the pressure caused by hazards; Meanwhile, ahead of the top coal recovery, economic, security and efficiency significantly, providing for fully mechanized caving mining face under similar conditions reference.