Study On Movement And Failure Law Of Overburden In Upward Mining Of Short Distance Coal Seam

Coal and gas outburst exists in close coal seams in more than half of China’s mines.Due to the characteristics of low permeability,high stress,high gas content and pressure,it further aggravates the difficulty of mining.According to the relevant national regulations on gas safety management,when facing the coal seams with high gas and gas outburst,the coal seams with relatively low gas content should be mined first,and the risk of other coal seams with gas outburst should be reduced through the pressure relief and release in the mining process.In this paper,in order to solve the risk of gas outburst caused by close distance 7 and 9 coal seams in mining area I 13 of Linhuan coal mine,various methods are adopted to explore the feasibility of upward mining,and the displacement,deformation and failure laws of surrounding rock.In this paper,the interval of mining influence coefficient K is10.36≤K≤37.03,and the average value is 15.02.7 coal is above the caving zone after 9 coal mining and within the fracture zone,which meets the upward mining conditions.There is no bench subsidence and maintains the overall continuity.The plastic zone does not evolve to coal 7.The pressure relief line at an angle of67 °with coal 9 at the cut hole is the dividing line,the outside of the pressure relief line is the pressurization zone,and the inside of the pressure relief line is the pressure relief zone,The place within 70 ～ 160 m from the cut hole in the goaf is the re compaction area.The stress outside the cut hole and the stope line is basically unchanged beyond 40 m ～ 50 m,which is the original rock stress area.The numerical simulation results show that the plastic zone does not develop above coal 7.The monitoring results of on-site multi-point displacement meter show that the change process of the vertical downward subsidence rate of the roof of coal 9 tends to be stable from the beginning of slow growth-rapid growth-slow growth-and the roof of coal 9 tends to be stable after 216 days from the beginning of subsidence.Due to the limitation of the observation time of the model,the interval after the mining of the lower coal seam is not less than 10 months,and the roadway excavation of the upper coal seam can be carried out.Based on the above results,the development height,roof movement,stress change law and overburden settling time of the two zones of coal 9 are obtained,which proves that the upward mining of coal 9 in mining area I 13 of Linhuan mine is feasible,and the gas outburst of coal 7 is alleviated.The research results provide reference and guidance for the mining of similar mines in the future.Figure [63] Table[19] Reference[65]...