Top-coal caving structure and technology for increasing recovery rate at extra-thick hard coal seam

In order to overcome the poor caving property problem of extra-thick hard coal seam with shallow depth in mining area of west China,the top-coal caving structure and recovery rate improvement technologies were analyzed through theoretical model calculation,numerical modeling analysis and equipment structure optimization design based on the coal seam occurrence conditions at Jinjitan Coal Mine. Through building the cantilever beam model for extra- thick hard coal seam,the relationship between the top-coal thickness and the cantilever ultimate fracture length was analyzed and calculated. The damage effect from the repeating support of hydraulic support on the top-coal was quanti- tatively analyzed for the first time,and the top-coal damage depth and lumpiness from the active support reaction and support frequency of hydraulic support was studied. The contradiction between the rib spalling prevention and top-coal recovery rate improvement was analyzed,which could be settled by optimizing the network structure of hydraulic sup- port. Three level efficient top-coal caving institution and the rear scraper conveyor cross side discharge arrangement were innovatively designed,which enhanced the top-coal recovery rate and efficiency.