An analysis of the chemical composition characteristics and formation of the karst groundwater in the Taiyuan Group in the lower part of a coal seam

Under the deep-buried condition, coal mining always is seriously threatened by karst groundwater inrush disasters from carbonate aquifers beneath a coal seam in eastern China. Analyzing hydrogeochemical components characteristics and exploring the control factors are an important prerequisite for preventing karst groundwater hazards. In this paper the karst groundwater in the Taiyuan Group in the lower part of the coal seam floor of Group A of the Huainan Gubei mine is taken as the research object. The multivariate statistical method, hydrochemical method(piper diagram, ions ration coefficient) were combined with groundwater system theory, the hydrogeochemical component characteristics and the control factors of the karst groundwater-bearing system covered by massive unconsolidated sediments are discussed. The results show that the cations are dominated by Na⁺+K⁺, and the anions by Cl^- and HCO₃^- in the karst groundwater mining in the limestone of the Taiyuan Group in the Gubei coal mine. Cation exchange, adsorption and desulphidation mainly occur, and the groundwater is characterized by "salinity" and "hardening". The formation of hydrochemical compositions and hydrochemical types are affected by the geological structure, buried depth, different hydrochemicl environment (oxidation-reduction), temperature change and water-rock reactions along the groundwater flow paths in the Gubei mine.