Study On Gas Control Technology Of Fully Mechanized Caving Face With Hard Roof In Extra-thick Coal Seam

The gas in the upper corner of the fully mechanized top coal caving face in extra-thick seam hard roof is easy to exceed the limit,which is a technical problem restricting the safe and efficient mining of the fully mechanized top coal caving face.Solving the upper corner gas transfinite is of great significance to the safe and efficient mining.Based on the mining conditions of Xiaogangou coal mine in Hutubi,Xinjiang,taking the dynamic gas control as the concept,through field measurement,theoretical analysis and engineering practice,the gas emission law of coal mining face is studied,and the main source of the gas is analysed,the treatment scheme is put forward,and it is verified by practice.The thickness of coal seam in 11144 working face is 13m,and the roof is medium hard.During the working face mining,there are more coal left in the goaf,and there are cavities in the goaf,and the gas overrun often occurs in the upper corner,especially when the roof plate is broken in a large area.In order to solve the problem of gas overrun in 11144 working face,based on the accurate measurement of gas content,the analysis of gas source and gas emission law in working face,combined with the law of overburden breaking in goaf,gas distribution and migration in goaf,the dynamic gas control measures with the roof moving to high-level borehole gas extraction as the main means are determined.Through measurement,the maximum gas content of coal seam in the working face is 3.32m3/t,with an average content of 2.35m3/t;the maximum absolute gas emission of the working face is predicted to be 9.68m3/min,with a minimum of 5.33m3/min,with an average of 6.61m3/min;research and analysis show that 68.7%of the gas in the working face comes from the goaf,and according to the flow and accumulation rules of the gas in the goaf to the top caving zone and fracture zone,the dynamic gas control scheme of high-level borehole gas drainage is developed.The engineering practice shows that after adopting the gas control scheme,the gas in the upper corner of 11144 working face does not exceed the limit,The gas concentration in thereturn air tunnel is reduced to 0.1%-0.3%,and that in the upper corner is reduced to 0.2%-0.4%,and the gas in the upper corner and return air lane is effectively controlled,which meets the requirements of gas control in the production period.The study of this paper not only solves the problem of gas control in the same working face of Xiaogangou coal mine,but also provides experience for gas control in the similar coal mine working face.