Research On Groundwater Chemical Characteristics And Genesis Mechanism Of Main Water-filled Aquifers In Xinzhi Coal Mine

The chemical composition of aquifer groundwater is the result of long-term interaction between aquifer medium and groundwater.Understanding its characteristics and genetic mechanism can help people better understand the regional geological history and the evolution of the natural environment with the participation of groundwater,and reveal the hydrogeological environment of groundwater,also helps to understand the relationship between people and ground,analyze the source of mine gushing and water inrush,and infer the hydraulic connection between aquifers.In this paper,the main water-filled aquifers in Xinzhi Mine:Shanxi Formation K₈sandstone aquifer,Taiyuan Formation K₂ limestone aquifer,Ordovician limestone aquifer are the research objects.Based on data such as groundwater's main conventional ions,TDS,p H value,etc.,the groundwater chemical characteristics and groundwater chemical action of main water-filled aquifers in mining areas,and hydraulic connections between aquifers was studied using Piper's three-line diagram,Gibbs diagram,saturation index method,ion ratio coefficient,principal component analysis,hydrogeochemical simulation,and so on.The following main results have been achieved:?1?The water chemical types and characteristics of the main water-filled aquifers were identified.The water chemistry types of K₈ sandstone in Shanxi Formation are mainly SO4-Na and HCO3-Na;the water chemistry types of K₂ limestone in Taiyuan group are mainly SO4-Ca and HCO3-Ca;the water chemistry types of Ordovician limestone are mainly SO4-Ca and HCO3-Ca.The overall circulation of groundwater in the study area alternated slowly.The main ionic components that affect the TDS content in the K₈ sandstone water of the Shanxi Formation are K⁺+Na⁺,Ca²⁺,Mg²⁺,and SO₄^2-;K⁺+Na⁺,Mg²⁺,Cl^-,SO₄^2-,HCO₃^-in the K₂ limestone water of the Taiyuan Formation all have an effect on the TDS content;in the Ordovician limestone water,SO₄^2-,Ca²⁺,and Mg²⁺are the main ionic components that affect the TDS content.Among them,the hydrogeochemical evolution process of Taiyuan Formation K₂ limestone and Ordovician limestone aquifer is similar.?2?The genesis mechanism of the main components in the groundwater of carbonate aquifers was studied by Gibbs diagram,saturation index and ion ratio coefficient.Among them,K⁺,Na⁺,and Cl^-are mainly derived from the dissolution of rock salt,and K⁺and Na⁺are also affected by the cation alternate adsorption and silicate rock dissolution;Ca²⁺,Mg²⁺,and HCO₃^-are mainly affected by the dissolution of carbonate rock,Ca²⁺and SO₄^2-are also affected by gypsum segments in the aquifer.?3?It points out that coal seam mining has a restructuring effect on groundwater chemical composition,which is mainly reflected in the fact that the mining fissure has increased the groundwater flow channel,the mine drainage has taken away the original water source of the aquifer,and the mixing between different aquifer waters has occurred near structures such as water-conducting fractures or water-conducting sinking columns.All these have changed the groundwater chemical environment and made the aquifer groundwater chemistry more complicated.?4?According to tracer tests,principal component analysis,and reverse hydrogeochemical simulation,it is shown that the roof water of 10#coal seam in the Dongsi extension of Xinzhi Mine has little connection with the Ordovician limestone water,which mainly belongs to Taiyuan Formation K₂ limestone water.The reason for the change of the groundwater chemical composition here is that the excavation of the roadway caused cracks,which destroyed the original runoff environment of the groundwater in the aquifer and accelerated the dissolution of the groundwater.However,there may be a hydraulic connection between the K₂ limestone aquifer in the Taiyuan Formation and the Ordovician limestone aquifer in other fracture or subsidence column positions in the area.Attention should be paid to prevent water inrush when mining coal seams.