Gas Migration Rule And Its Application In The Fully Mechanized Mining Face Gob Of Close Distance Coal Seams

Because of the existence of the adjacent layer, the source and migration of gas are special in time and space when the fully mechanized face of close distance coal seams are mined. With these particularity, The control and prevention of gas hazard is more difficult.So the knowledge of failure characteristics of cover rock after mining is very necessary,as so as the seepage low of gas in the gob and cover rock.This paper is based on the similar material experiment and theoretical analyses of distributing of stress and overburden rock fracture, the failure characteristics of overburden rock fracture after mining are analyzed. In order to make clear the laws of stress distribution and fissure evolutionary of overburden in topple mining, we attempt to adopt the physical simulation experiment in the lab. Then through the similar material experimental conclusion and the fluid dynamics and seepage mechanics, the equation of the gas seepage in gob is establish. Then this paper use FLUENT to simulate 3D models of gas concentration distribution in gob of fully mechanized face. According to the numerical simulation, with the U-ventilate model, adjusting the air volume has a great influence on the concentration of gas in gob, but sometime it can not solve problem that gas concentration is often over limit in return airflow corner. According to the scene determining whether it is need to set up the advance roadway borehole diversion extraction, or not. By choosing the right extraction amount, the concentration of gas at working face can be reduced effectually, and the problem that gas in upper corner out of gauge can be solved. Finally,By investigating The actual situation after the advance roadway borehole diversion extraction be used in fully mechanized face 14-2# coal seam 81004 of Meiyukou coal mine in Datong. From actual measurement, it is concluded in this paper that the actual situation fits well with the experimental results: a large quantity of gas is drained by with the advance roadway borehole diversion extraction. In the same time, the concentration and emission to the workplace of gas is reduced, ensure safe production.