Feasibility analysis of “regional pre-pumping and pressure relief and anti-impact” of directional long borehole in Tingnan Coal Mine working face

In view of the common use before mining at 402 face in Tingnan Coal Mine, there are some problems in the process of pressure relief drilling, such as high drilling cost, long construction period, drilling deviation, which will cause air leakage in the extraction drilling hole in this area, reduce the negative pressure of extraction and mining, and influence the efficiency of roadway excavation by the mutual interference between the construction of multiple processes, through numerical simulation, the directional drilling machine adopts the directional long borehole of 120 mm to extract the gas in the mining area of the working face, and the directional long borehole of 150 mm is used to relieve the pressure of the roadway head and the roadway side of the working face. The distribution characteristics of stress peak position, stress concentration zone, stress reduction zone and plastic zone in the lead head of directional long drilling hole with 500 m and 30 m ahead head of pressure relief hole were compared and analyzed. The results show that the stress peak of directional long borehole after pressure relief is basically distributed about 2.5 m away from the roadway, and the high stress concentration area is mainly distributed in the range of 2-5 m away from the roadway. In this range, the stress peak is transferred to the deep part of the coal, the stress concentration range is reduced, and the pressure rerange is increased, which has a better pressure relief effect.