Principle and key technologies of controlled water mining and practice of fully-mechanized mining under soft sandstone aquifer

In view of the different geological and hydrogeological conditions,complicated types of water bodies and the engineering practice of coal mining under water body,the idea,technical principle and key technology of water-con- trolled coal mining technology were expounded in detail considering the important factors such as coal mine safety and economic rationality. This technology solves the problems of large coal resources losses caused by different types of wa- terproof coal pillar technology in coal mining under traditional water body,and the problem that the single use of aqui- fer drainage technology is not only easy to form artificial water diversion channel,but also increases mine water inflow and drainage cost due to the excessive drilling of aquifer. Combined with the characteristics of fully mechanized caving technology,the technique was applied to fully mechanized top-coal caving mining under semi-consolidated sandstone aquifer in Tiebei Coal Mine. The results show that according to the existing state and water-rich degree of coal seam roof sandstone aquifer,the different damage degree of overburden and the spatial relationship between main coal seam and aquifer,based on the technical principle of combining pre-mining and edge-mining thinning before water-con- trolled mining,using the layout of fully mechanized caving stope along the bottom of coal seam,the characteristics of flexible adjusting and controllable coal thickness,the overall scheme of water-controlled coal mining,which consists of the combination of mining with top-water body and mining with dewatering or draining,the combination of mining after draining and mining while draining,the combination of borehole dewatering or draining and mining dewatering or drai- ning,and the combination of controlling the thickness of top-coal caving and aquifer draining degree in sections,is fea- sible. Three to eight meter step-type safe mining has been realized,which can control water inflow,improve working environment and prevent water-burst sand disaster.