Effect of roof movement on gas flow in an extremely thick coal seam under fully mechanized sublevel caving mining conditions

摘要

The abnormal emission of gas in coals is the main factor that induces serious gas disasters in coal mines. During the coal mining process, roof movement has important effects on the gas emission law and gas flow characteristics. In this study, an extremely thick coal seam under fully mechanized sublevel caving mining conditions from the Tashan coal mine in China was used as an example; the effect of roof weighting on gas emission in the goaf was studied. Then, the large roof weighting step and the small roof weighting step caused by the different thicknesses of lamprophyre breakage were used as the objects and a numerical simulation study on the gas flow characteristics in the goaf was carried out. The results indicate that the mining coal seams, the overlying adjacent unmined coal seams, and the goaf are the main contributors to the large gas emission capacity, and even situations exist where the gas concentration exceeds the limit in the working face. During roof weighting, the gas concentration and emission capacity in the return airway, upper corner, and high drainage roadway increase substantially. The results of the numerical analysis are in good agreement with the observed data, which indicates that it is effective to control the gas in coal seams by designing the location of high drainage roadway according to the mining characteristics of coal seam and the gas emission law.