Prevention of water and mud inrush in longwall top coal cave mining under shallow buried thin bedrock

摘要

During longwall top coal caving mining of shallow buried thin bedrock and thick coal seams, penetrating fractures mayform in the rock strata above the roof, causing an inrush of water and sand at the working face. The 507-working face of theMadiliang Coal Mine in Inner Mongolia, China, is a shallow buried thin bedrock and thick coal seam, mined by longwalltop-coal caving mining. The field exploration results showed that the immediate roof consists of a layer of yellow mudwithin 400 m of the working face. The yellow mud has greater fluidity when encountering water and sits below a layer ofyellow sandstone, which has a high risk of inrushing water and mud. Considering the roof lithology, longwall top coal cavingmining characteristics, the fluidity of yellow mud, and the progressive failure of the coal seam, the particle flow codein two dimensions was used to establish the longwall top coal caving mining numerical model and analysed the movementcharacteristics of the top coal and yellow mud under different top coal thicknesses. Based on the results of field investigationsand numerical calculations, a work-safe mining scheme was proposed, where the working face retains 4 m of top coal formining. When the top coal thickness is less than 4 m, shearer cutting floor rock mining. A real-time mine pressure monitoringsystem was also established. The field application showed no incidents of water and mud inrush during the recoveryperiod, which protects the working face.