Methane control for mechanised longwall top-coal caving faces in high gas content mines

In China, mechanised longwall top-coal caving technology (LTCT) has been widely used under suitable thick coal seam conditions due to its low cost, high production and productivity since it was introduced in 1982. It has even been applied in some high gas-content mines (e.g. No. 5 Mine, Yangquan coalfield), where methane is the most serious hazard affecting production in the mine. With the introduction of LTCT in 1992, the frequency of production delays greatly increased due to excess methane. In order to solve these problems, China University of Mining and Technology (CUMT) has been carrying out methane research jointly with Yangquan Coal Group Co. (YCGC) since 1993. The major focus of the research was concerned with the gas source and emission characteristics of the longwall top-coal caving face (LTCF) and the methane drainage methods from the adjacent strata during initial and normal mining. The research has helped the mine to control methane-related production delays to tolerable levels. The methane problems during normal mining were solved by the adoption of the high-level strike drainage roadway (HSDR). The methane concentration during initial mining was kept below the statutory limits by the adoption of the mid-level drainage roadway (MDR). In this way, the methane-related production delay problems were successfully solved by introduction of the HSDR in conjunction with the MDR. This paper analyses the gas source and emission characteristics of LTCF, and describes the experiences and methodologies adopted in methane control at the LTCF during normal and initial mining.