切顶沿空留巷U+L型通风采场煤自燃风险判定研究

Study on the risk assessment of coal spontaneous combustion in U+L typeventilation stopes with roof cutting gob-side entry retaining

为探究切顶沿空留巷首采面U+L型通风采空区煤自燃危险性,以蒙西棋盘井煤矿东区9-1#层11101工作面为工程背景开展研究。通过封闭耗氧实验,测定得出煤样的耗氧能力弱、不同氧体积分数下煤样的耗氧速度慢、窒熄氧气体积分数(煤耗氧临界值)为15%。通过现场实测确定切顶沿空留巷和工作面的两端压差和漏风分布,现场埋管实测得到回风侧的氧分布数据,搭建了切顶沿空留巷采场相似模拟实验台,得到采场的漏风移动规律。运用CFD仿真探究了切顶沿空留巷采空区的漏风与自燃氧化分布特征,得到采空区可能具有自燃危险的3个区域分别位于开切眼附近、靠近沿空留巷的5~10 m内和工作面后方。提出在尾巷注氮和沿空留巷边界注浆堵漏防灭火措施条件下,可将U+L型通风采空区自燃模式转化为U型通风采空区自燃模式的危险性判定,得到棋盘井矿采空区自燃氧化带的最大宽度为80 m,最低安全推进速度1.2 m/d,无自燃风险,为工程防灭火做出指导。

In order to explore the risk of spontaneous combustion of coal in the U+L type ventilation air area of the first mining surface along the roof cutting gob-side entry retaining,the engineering background of the 11101 working surface of layer 9-1#in the east area of the Mengxi Checkerboard Well Coal Mine was carried out.Through closed oxygen consumption experiments,it is determined that the oxygen consumption capacity of coal samples is weak,the oxygen consumption rate of coal samples is slow under different oxygen volume fractions,and the suffocation oxygen volume fraction(critical value of coal oxygen consumption)is 15%.The pressure difference and air leakage distribution between the two ends of roof cutting gob-side entry retaining and the working surface were determined by on-site measurement,the oxygen distribution data of the return air side was obtained by the actual measurement of the buried pipe at the site,and a similar simulation experimental bench was built for the roof cutting gob-side entry retaining in the mining area to obtain the leakage movement law of the stope.The characteristics of the leakage and spontaneous combustion oxidation distribution of the goaf area along the empty retention lane of the cut top were explored by CFD simulation,and the 3 areas of the goaf area that may have spontaneous combustion hazard were located near the open eye,close to the 5~10 m along the empty space lane and behind the working surface.Under the conditions of nitrogen injection in the tail lane and grout plugging and leak prevention and fire extinguishing measures along the boundary of the empty lane,the risk of converting the spontaneous combustion mode of the U+L ventilation air area into the spontaneous combustion mode of the U-type ventilation air area can be determined.The maximum width of the spontaneous combustion oxidation belt in the goaf area of the Checkerboard Well Mine is 80 m,the minimum safe propulsion speed is 1.2 m/d,and there is no risk of spontaneous combustion,which provides guidance for the engineering fire prevention.