Water Source Discrimination Model And Hydrogeochemical Simulation Of Typical North China Type Coalfield

With the development of coal mining to the deep,the original hydrochemical environment of the aquifer in the North China type coalfield has been changed or destroyed,resulting in changes in the hydrochemical characteristics and water cycle evolution of the aquifer groundwater,and the threat of water inrush has become more and more serious.Therefore,taking No.13 mine of Pingdingshan coalfield as a typical study area,the hydrochemical and hydrogeological conditions of groundwater in main aquifers of mine area are analyzed.By using the methods of mathematical statistics and hydrogeochemistry,the hydrochemical characteristics of the main aquifers in mine are analyzed,the quality of groundwater is evaluated,the source of water inrush in mine is identified,the main controlling factors affecting the hydrogeochemical evolution of groundwater in mine are studied,and the hydrogeochemical process is quantitatively simulated.（1）According to the fuzzy comprehensive evaluation method,the water quality of the main water bodies in the coal mining area is evaluated.Except that most of the water samples in the Quaternary aquifer are grade IV and V,the water quality of limestone water is grade III,which can be used for domestic or industrial water in the mine area after treatment.（2）The piper-entropy weight-equivalent numerical model is constructed to identify water samples.Nine water samples are correctly identified and one is misjudged.The proportion of Na⁺+K⁺,Ca²⁺and SO₄^2-in the weight calculated by entropy weight method is large,which plays an important role in water source identification.(3 According to Gibbs diagram,typical ion ratio and chlor alkali index diagram,the hydrochemical ions of groundwater in No.13 mine mainly come from the dissolution of dolomite,calcite,gypsum,salt rock and other minerals as well as the alternating adsorption of cations.（4）The principal component analysis reveals the temporal and spatial distribution characteristics of groundwater water rock interaction.With the development of exploitation,the hydrochemical environment of Carboniferous limestone aquifer gradually opens,the dissolution of carbonate rocks and sulfate increases,and the water quality evolves to"hardening"and"salinization".The Cambrian limestone water is affected by exploitation,the water rock interaction weakens,and the"hardening"of groundwater is reduced.The middle part of Carboniferous limestone aquifer is affected by the structure,and the ion exchange is accelerated,while the intensity of desulphidation along the runoff direction of Cambrian limestone groundwater is increased.The hydrochemical evolution of groundwater is mainly affected by geological structure and exploitation.（5）The temperature of deep hot water calculated by hydrochemical temperature scale method is between 58℃and 71.46℃.With the increase of depth and temperature,the proportion of cold water mixing gradually decreases,the hydrochemical environment becomes closed,the saturation index of salt rock in groundwater gradually increases,and the unsaturated gypsum presents a downward trend.（6）The water rock interaction in the process of groundwater runoff is quantitatively studied by reverse hydrogeochemical simulation:the groundwater in Carboniferous limestone is recharged by a small amount of Cambrian limestone groundwater in the process of runoff,dolomite,calcite and gypsum are precipitated,salt rock is dissolved,and the main form of ion exchange is the replacement of Ca²⁺in water.While the groundwater in Cambrian limestone was in the process of runoff,dolomite and calcite are partially dissolved,gypsum is precipitated and ion exchange is strong.（7）The quantitative study of forward hydrogeochemical simulation shows that when the recharge of Cambrian limestone water to Carboniferous limestone water increases,the contents of SO₄^2-and HCO₃^-in Carboniferous limestone groundwater decrease,and the TDS gradually decreases;when the recharge of Cambrian limestone water to Carboniferous limestone water decreases,the contents of Ca²⁺,SO₄^2-in Carboniferous limestone groundwater increase,and the TDS gradually increases.