Comprehensive evaluation of drainage feasibility for thick sandstone aquifer of floor

In order to guide the water disater prevention and control of floor sandstone, it is necessary to make reasonable evaluation on the aquifer. Based on the hydrogeological conditions of typical mine and water disaster case, the pumping test data of hydrogeological boreholes are analyzed, and the floor sandstone with drainage feasibility was proved. The water level variation curve slope per unit time of observation boreholes was studied by the dewatering test with large inflow and drawdown. The drainage rate of floor sandstone aquifer is fast and the recovery rate is slow. Increasing the drainage amout can accelerate the drawdown of aquifer water level effectively. The drainage with large inflow can stimulate the change of groundwater flow field to the greastest extent. In a certain range, the groundwater level can be decreased continuously by drainage of sandstone aquifer below the coal seam. In the process of single-borehole and multi-borehole drainage, the recovery time of groundwater level accounted for 77.92% and 86.21% of the dewatering time, while the groundwater level only recovered 39.11% and 46.56% of the maximum of drawdown, indicating that the groundwater level of sandstone aquifer is easy to drain and difficult to recover. According to the change of water quantity and water pressure of the dewatering boreholes, the water quantity will gradually decrease and the groundwater level will decrease significantly after a long time drainage, which proves that the recharge condition of the sandstone aquifer is general. Combined with the strata and strucural conditions of the coal field, it is suggested that the location of the sandstone aquifer in a relatively closed water-repellent space is conducive to drainage. The results show that based on the data of pumping test and dewatering test, the drainage feasibility of thick sandstone aquifer can be comprehensively evaluated from the unit time change rate of groundwater level, pumping and recovery goundwater level curve, water pressure change of dewatering boreholes and boundary condition of aquifer.