Evolution of the Mining-Induced Bed Separation and Hydraulic Variation in an Extra-Thick Aquifer

Mu Us desert and beach extensively distribute in the middle area of Ordos Basin, Northwest China, which has good ecological environment due to the abundant groundwater resource of phreatic aquifer and Cretaceous aquifer with the shallow depth. Cretaceous strata are mainly composed of sandstone with extra-thick layer structure whose thickness ranges from 300 to 1000 m. Underlying the Cretaceous strata, Jurassic coal strata reserve a large amount of coal resource which makes the Ordos region been the largest coal-producing area in China currently. Due to underground coal mining, water table decrease of the Cretaceous aquifer was observed, which caused impact on the shallow water resource and surface ecosystem. However, the water of Cretaceous aquifer does not inflow into the goaf, which is located over the water-conducting fracted zone. Taking the Yingpanhao Mine in the grassland as a case study, the evolution of bed separation and hydraulic variation were tested by monitoring the strata movement and hydraulic pressure and the developed location of bed separation in Cretaceous strata were theoretically analyzed. The impact on the flow field induced by the bed separation was analyzed and the mechanism of non-inrush and non-leakage of Cretaceous aquifer in Mu Us desert and beach area were determined, which plays an important role for the protection of shallow water resource and ecosystem in coal mining area.