Research and application of cross fusion of the influence of the inclination angle of fully mechanized caving face on the differential shape dimension of gas transport and storage

It was of great significance to clarify the flow and accumulation law of depressed-pressure gas in goaf during coal mining to ensure the safety of mine operation. Using the main mining face of the B5 coal seam in Tengda Coal Mine, Heze, Xinjiang, China, as a case study, the evolution patterns of mining-induced fissures under different coal seam inclination angles were investigated. The transport and storage areas of pressure relief gas were determined. The variation process of pressure relief gas transport and storage areas were studied by using fractal dimension software. A fractal dimension quantitative characterization model of dip effect in gas transport and storage areas under pressure relief was established. The cross-fusion characteristics of gas transport and storage areas under the influence of dip angle were revealed. The results shown that the fracture field could be divided into gas reservoir area, gas migration area and overburden compaction area by the abrupt change point of 1.87 m and 0.57 of penetration degree during mining. By studying the fractal dimension changed law of different regions, it was understood that the gas transport and storage areas presented the change process of “transport and storage integration—regional display—cross fusion—regional separation” with the advance of the working face. In the stage of “region formation—cross fusion—region separation”, the fractal dimension presented three states: small change, drastic change and new development. The characteristic parameters (regional height and width) of gas transport and storage areas under the influence of dip angle were obtained. A fractal dimension quantitative representation model of dip effect in gas transport and storage areas was established. According to the actual situation on site, the space section range of gas transport and storage areas was calculated. The layout parameters of gas extraction borehole with pressure relief on the working face were optimized through the section range. After optimization, the extraction purity and volume fraction of pressure relief gas increased significantly. The fractal dimension quantitative characterization model of inclination effect in gas transport and storage areas and the rationality of borehole layout were verified. The research results could provide a reference for accurate and zonal extraction of pressure relief gas in inclined thick coal seam.