Design of gas control lane of 9# coal seam in Wuhushan Mine based on layer layout optimization

In order to address the issue of gas over limit in the upper corner of the working face of the 9# coal seam in Wuhushan Mine, a series of theoretical and numerical simulation analyses were conducted to evaluate the optimal configuration for the gas control lane of the 9# coal seam. In accordance with the "O" circle theory and the lithology of the overlying rock strata of the 9# coal seam, the height range of the fallout zone and fissure zone in the working face mining area was determined by employing empirical formulas. The change rule and distribution characteristics of the porosity of the fissure zone and the fall zone in the mining area were analyzed based on the characteristics of rock movement and fall. The determination method was also provided. The numerical simulation software was employed to simulate and analyze the gas concentration field in the air-mining zone under conditions of no extraction and six distinct layer positions of the gas control lane. The optimal layer position of the gas control lane in the 9# coal seam was determined and subsequently implemented in the field. The results demonstrate that the overlying rock layer in the 9# coal seam exhibits a height range of 6.86 ~ 11.26 m, while the fissure zone displays a height range of 30.11 ~ 41.31 m. When the gas control road is situated in close proximity to the working face, the gas concentration field exhibits a markedly low concentration. When the distance between the gas control lane and the return airway of the working face is 20 m and the distance from the top of the coal seam is 20 m, the gas concentration in the upper corner and the return airway is 0.35% and 0.26%, respectively. These values are close to the lowest concentration observed in the layout scheme. Additionally, the gas extraction concentration and the pure volume of the gas control lane are 23.7% and 38.3 m³ min^-1, respectively. These values represent the highest concentrations observed in the various layout schemes. The application of the gas management lane in the field, based on the numerical simulation results, demonstrated a successful extraction effect, which was consistent with the numerical simulation results. This effectively managed the issue of an over-limit of gas in the upper corner of the working face of the 9# coal seam.