Optimal measures for gas control on fully mechanized working face of close-distance coal seam group

Compared with single coal seam or other coal seam group, the mining process of the close-distance coal seam group is more likely to be affected by the stress of the adjacent seam. Moreover, the gas is more likely to gush into the coal seam through the developed fissures, causing gas accumulation on the working face of the mining seam. The existing gas control research for close-distance coal seam group mainly focuses on the determination of single measure parameters and effect analysis, without in-depth research of the relationship between gas management measures in time and space. The researches on the optimal combination of comprehensive gas management measures, the basis for determining specific parameters and the effect analysis after the measures being taken are not sufficient enough. In order to solve the above problems, taking the 81403 fully mechanized working face of No.1 Coal Mine of Yangquan Coal Industry (Group) Co., Ltd. as the research object, the paper analyzes the stress distribution and evolution process of mining under the conditions of close-distance coal seam group through numerical simulation. The research studies the overlying rock destruction and fissures development change law, and proposes that the main sources of gas on the 81403 fully mechanized working face are coal seam desorption gas, pressure relief gas in upper adjacent coal seam and goaf gas, etc. Based on the different gas emission sources and characteristics, the paper proposes the gas extraction measures of bedding pre-extraction + high extraction roadway+high borehole+buried pipes in the extraction area. Before mining, pre-extraction is applied to reduce the amount of coal seam desorption gas. High extraction roadway and high borehole are used to deal with gas gush from adjacent coal seam. Buried pipes are used to control local gas accumulation in the upper corner. The measures form a comprehensive management system in time and space so as to achieve the purpose of gas control. Practical application results show that the gas extraction rate reaches 89.9% on the working face, and the gas volume fraction of the return airway and upper corner is kept below 1%, ensuring the safe mining of the working face.