Study on optimization and evaluation of continuous mining scheme in coal seam group

In order to optimize the continuous mining scheme of coal seam group in Yushuling Coal Mine, FLAC3D simulation is used to study the coal seam integrity and working face stress distribution law under two continuous mining schemes of downward mining and upward mining of coal seam group, and the economic benefits of the two schemes are compared. The results show that the coal seam suffers plastic damage to a certain extent during upward mining, but the damage scope of the coal seam plastic zone can be effectively reduced by arranging the transportation roadway and return air roadway of the lower No.7 and No.8 coal seams and the transportation roadway and return air roadway of the lower No.10 coal seam in an inboard way of 10 m. The undamaged areas of the lower No.7 and No.8 coal seams account for 87.5% and 60.4% respectively, and the integrity of the coal seam meets the requirements of safe mining. Compared with the downward mining, the average stress of the lower No.7 and No.8 coal seams during upward mining is reduced by 45.3% and 34.9% respectively, and the maximum supporting stress of the lower No.7 and No.8 coal seams is reduced by 66.7% and 36.4% respectively, and the economic benefit increase by 64.9%. Therefore, the upward mining is preferred as the continuous mining scheme of coal seam group in Yushuling Coal Mine. The optimization result of continuous mining scheme of coal seam group is theoretically verified by using analytic hierarchy process and fuzzy mathematics theory. By establishing the comprehensive evaluation index model of the coal seam group continuous mining scheme, constructing the judgment matrix of the criterion layer relative to the target layer and the index layer and carrying out the consistency test, the evaluation index weight vector is obtained. The membership degree matrix of each factor of the index layer relative to the downward mining and upward mining is constructed by using the linear function method and the binary comparison and ranking method, and the comprehensive membership degree index matrix is obtained. According to the evaluation index weight vector and the comprehensive membership index matrix, the comprehensive evaluation weights of the downward mining and upward mining schemes are obtained as 0.170 87 and 0.704 42 respectively, which verifies the feasibility of upward mining as the optimal scheme for the continuous mining of the coal seam group in this mine.