Hydrochemical characteristics and formation mechanism of Ordovician limestone water in Baode coal mine

Ordovician limestone karst water is the main threatening water source for mining activities in Baode coal mine, and it is one of the main water supply sources. Ordovician limestone karst water samples were systematically collected in Baode coal mine, and the methods of correlation analysis, ion proportional coefficient, saturation index inversion simulation and Chlor-Alkali index were chosen to analyze the hydrochemical characteristics and its formation mechanism. The results showed that the water quality types of Ordovician limestone water changed from runoff zone to stagnant zone in a trend of HCO₃-Na(Na·Ca)→HCO₃·Cl-Na·Ca(Ca·Mg)→Cl-Na(Na·Ca). The mass concentration of each ion was linearly related to TDS value, and positively correlated with TDS except for HCO₃^-. Cationic alternating adsorption, BSR and solution filtration were the main function to control the hydrogeochemical environment of groundwater in the coal mine. According to the saturation index(SI) calculation and simulation path, it was confirmed that calcite, dolomite and gypsum was dissolved in runoff zone, dolomite precipitation occured in stagnant zone, gypsum was always in unsaturated state and tended to dissolve. This conclusion would provide a basis for the prevention and control of water damage in deep coal mining and the utilization of mine water in Baode coal mine.