Layout study of bottom drainage roadway in deep mining of very close adjacent coal seam group

Based on the engineering background of the ultra-close adjacent coal seam group in the deep part of Pingdingshan No.8 coal mine, this paper studies the reasonable layering of bottom pumping roadway under the mining condition of deep ultra-close seam. FLAC^3D numerical model is used to simulate the evolution law of the plastic zone, stress field and displacement field of coal seam under different net rock distances between the roof of bottom pumping roadway and Ⅵ_16-17 coal seam. The results show that when the net rock distance is 3 m or 5 m, the coal seam above the bottom drainage roadway can be divided into pressure relief zone, stress concentration zone and primary rock stress zone under the influence of mining. When the net rock distance is 8 m or more, the coal seam above the bottom drainage roadway can be divided into pressure relief zone and primary rock stress zone under the influence of mining. The optimal layout of bottom drainage roadway is 8-10 m distance from the retained net rock. After the bottom pumping roadway is mined, the position directly above the roadway has the best pressure relief effect, the coal body in this area is fully deformed, the gas control is easier, is conducive to the support and maintenance of the coal roadway in the later period, and is the best position to arrange the coal roadway. Field monitoring effectively verified the reliability of the bottom pumping roadway in the net rock distance to control the gas outburst risk of the working face near the deep seam group.