Research On Top Cutting And Roadway Protection Technology Of 2505 Fully Mechanized Caving Face In Zhangcun Mine

The size of the stop-line coal pillars at the end of the mining period is often determined by experience.The lack of corresponding design basis will not only cause waste of coal resources,but also lead to large deformation of adjacent roadways.At the same time,after the working face is stopped,the overburden layer forms a long cantilever beam with coal pillar as the fulcrum.The coal pillar bears a large supporting force,which not only affects the integrity of the coal pillar,but also may damage the stability of the mining roadway.This paper takes the 2505 fully mechanized caving face of Zhangcun Coal Mine as the engineering background,and solves the problems of coal pillar design and the technology of cutting roof protection technology.Based on field investigation,theoretical analysis,numerical simulation,field practice and other methods,the cutting technology of 2505 fully mechanized caving face is studied.The main research contents and results are as follows:(1)By means of theoretical analysis,the distribution law of pressure of advanced support in fully mechanized caving face is analyzed.The leading bearing pressure of fully mechanized caving working face shows a trend of first rising and then falling,and finally tends to the original rock stress,whose influence range is about 70 m in front of the working face.(2)Through the analysis of the geometric model,it is determined that the mechanism of hydraulic fracturing is as follows: under the combined action of high pressure water pressure and original rock stress,the tangential tensile stress generated at a certain place of the borehole wall is greater than the tensile strength at that place,thus resulting in the phenomenon of fracture in the borehole wall.In this paper,the technical principle of hydraulic cutting top is given,the form and propagation direction of hydraulic crack,artificial surface of hydraulic crack initiation and fracture position of hydraulic cutting top are determined,and the construction technology of hydraulic cutting top is formed.(3)Through theoretical analysis and numerical simulation,the reasonable size of stop-line coal pillar in 2505 working face is studied,and it is concluded that the theoretical size of stop-line coal pillar should be 80 m,but after the top-cutting treatment,when the stop-line coal pillar size is 70 m,the stability of stop-line coal pillar can be guaranteed and the requirements of safe production of roadway can be met.(4)Based on the above research results,the hydraulic cutting design is given,and the industrial practice is carried out in the 2505 fully mechanized caving face of Zhangcun Coal Mine.The application results show that the hydraulic cutting technology of the 2505 fully mechanized caving face effectively breaks the overhanging roof,protects the stability of the 25 mining roads,reduces the loss of coal resources,and has significant economic and social benefits.