Coupling simulation of groundwater dynamics and solute transfer in the process of deep reinjection of mine water

The deep well reinjection of mine water is a main form of "transfer storage" treatment of mine water. According to the geological and mine water characteristics of the coal mine area in Ordos Basin, the paper puts forward the basis for selecting the target layer of mine water reinjection from the perspective of good matching between groundwater and mine water in the target layer of reinjection, the water isolation of upper and lower strata, permeability and sealing of the reinjection layer. Based on Darcy's law of groundwater and Dupuit's theory, a mathematical model of steady flow of water injection well in polar coordinate system is established. It is concluded that under the condition of steady water injection, the reinjection quantity is positively correlated with the permeability coefficient, thickness, reinjection pressure, water level burial depth and reinjection well diameter of water injection layer, negatively correlated with the influence radius, and it has nothing to do with the burial depth of water injection layer. The construction method of coupling simulation model of groundwater dynamics and solute transfer in the process of deep mine water reinjection was put forward, and mine water reinjection test was taken as the analysis object. The simulation results show that the formation of water injection well is the "high water mound" in the process of high-pressure mine water reinjection; the higher the injection pressure is, the more obvious the reinjection amount is. The model analysis results are basically consistent with the field test results. Moreover, the solute transfer range forms a "cylindrical" dispersion shape centered on the water injection well; the ion concentration changes sharply along both sides of the reinjection well; the ion concentration of the aquifer is rapidly diluted. With the extension of time, the increase of dispersion dilution range is relatively small, which indicates that the relative recharge of mine water has little effect on groundwater chemistry of deep high concentration aquifer. The research results are expected to provide scientific basis for efficient recharge of mine water in western coal mining area.