Method and practice of gas geological grading evaluation on coal mining face of high gas mine

Gas hazard is a main disaster type that restricts the safe production of coal mines in China. Under the cur-rent background of precise coal mining,the effective gas geological classification and accurate risk identification at the working face scale have become the key to ensure the safe and efficient production of high-gas mines. The Hancheng mining area is located in the eastern Weibei Carboniferous-Permian (C-P) coalfield in the southeastern margin of the Ordos Basin,and is characterized by complex tectonic conditions,high gas content and frequent gas dynamics phenom-enon. However,the detailed study on gas geology law at working face scale is relatively limited,which is insufficient in guiding coal mining. Based on the gas geological conditions in the Hancheng mining area and the principles of applica-bility and feasibility,six parameters including coal seam depth,thickness,coal body structure,structural deformation and absolute / relative gas emission quantity are selected as basic indexes to determine the grading evaluation threshold criteria. Based on the principle of multi-level fuzzy mathematics evaluation,a gas geological grading evaluation method for working face is proposed,which includes the establishment and grading of evaluation parameter system,the deter-mination of membership function and weight,the construction of mathematical model,geological mapping and zoning e-valuation. On this basis,taking the No. 4321 working face in the Sangshuping mine as an example,the gas geological grading evaluation index is calculated by regional mesh generation and coupling single geological index. The results show the gas geological conditions of the working face vary significantly,which can be divided into four types:type I advantageous area,type II relatively advantageous area,type III relatively disadvantageous area,and type Ⅳ disadvan-tageous area. The grading and zoning results of the working face are in good agreement with the actual geological con-ditions. The structural deformation of coal seam and the resulted coal structure fragmentation are the main geological factors influencing the safe mining of working face. The multi-level fuzzy mathematic gas geological grading evaluation method proposed in this paper meets the actual needs of current trend of accurate and safe coal mining,and has refer-ence significance for the gas geological support in other high gas mines and tectonically deformed coal development ar-eas.