Deep Hole Loose Blasting Technology Research On Hard Roof In The Mechanized Caving Mining Face

In the process of coal mining,the hard roof on the mining coal seam is oneof the main disasters of coal mine accidents. Hard roof refers to coal seam roofwhich is thick, high strength, strong joints and fissures highly developed,integrity and the bearing capacity of roof. These can lead to hanging roof whichhas a very large area, which collapses suddenly so that the dynamic pressurewhich was produced by hanging roof can put the impact on downhole equipmentand workers. This can bring huge hidden trouble to coal mine safety inproduction.Therefore, based on the research of the past researchers on the roof,this paper explores the control blasting technology of this kind of roof and takeshard roof on2105fully-mechanized coal mining face in Zhangcun coal mine asindustrial practice.This paper analyses hard roof on2105fully-mechanized coal mining facein Zhangcun coal mine based on the theoretical research, numerical simulationand the method of industrial practice. Firstly, we get on-site investigation anddata gathering on2105fully-mechanized coal mining face in Zhangcun coalmine, master the fully-mechanized coal mining method and the management ofthe roof of the technology and so on, and combine with the experienceultimately to determine the deep hole loose blasting technology to weaken thefully-mechanized face hard roof. By adopting the deep hole loose blastingtechnology,it can destroy the integrity of the roof in advance, reduce the area ofroof hanging, turn down the roof caving step distance for the first time, toprevent or weaken the large area roof pressure. By comparing CO concentrationand the support working resistance of before and after blasting, as well as the results of peeking roof broken condition, we analyze effect of the hard roofwhich was weakened by deep hole blasting technology.Finally with the aid of ANSYS/LS-DYNA numerical simulation software,the coupl ing charging structure and air non-coupl ing charging structure isanalyzed by simulation, through drawing stress and fissure figure can indicatesthat the air non-coup ling charging structure can make the ho le penetrationbetween the fracture, and destroy the integrity of the hard roof, achieving thegoal of safe caving. Through comparing stress and fissure figure of blastinggroup distance of8.5m,9m,9.5m, it is concluded that when the blastinggroup distance is9m, the blasting effect is better, the adjacent hole fracturepenetration is better, extended range which was get by each blasting group is notvery big, and adjacent hole has had little impact to the other. Blasting groupdistance of9m which was simul ated is consistent with design of blastingscheme, thus verify the feasibility of blasting scheme.