Safely improving by stage the upper limit of mining under extremely thick loose aquifer

For maximum recovery of coal and safely reducing waterproof coal pillar in Huaibei Liudong coal mine, the upper limit of mining was improved by two steps:water-proof and sand control. In west No.3 mining district, firstly through research and analysis of the hydrogeological data of the aquifer and water-resisting clay layer at the bottom of the Quaternary system, the bottom aquifer of the Quaternary system in the western 31000 coalface was determined as weak watery, and the mining disturbance of water body was of level II. Then through numerical simulation, physical simulation comparison and analysis, the damage height of overlying rock after mining was studied and compared with the mine actual observation value, the development height of the water conducting fractured zone was confirmed as 41.3 meters; The paper put forward the safe and reasonable waterproof upper limit of mining, and 0.221 million tons of dull reserves were liberated. A good foundation has been set for further safe mining through sand control.