| As an important part of coal mining,groundwater is not only a hidden danger but also a resource.Therefore,it is great significance to study the dynamic characteristics of groundwater in the process of coal mining,and analyse the influencing factors that make groudwater variation,which is conducive to solve the mine water damage and make rational use of groundwater resources.Taking Wugou Coal Mine in Huaibei coal field as an example,the paper discusses the change rule of water level in time and space since the coal mine was mining in Wugou Coal Mine,and the characteristics of hydrogeochemistry ions content and distribution in the area by collecting mathematical statistics and visualizing the water level and hydrogeochemistry data in this area.The factors influencing groundwater level and chemical characteristics of Wugou Coal Mine are analyzed.The former adopts Random Forest(RF)and Analytic Hierarchy Process(AHP),the latter adopts Ion Activity Ratio,Principal Component Analysis(PCA)and Hydrogeochemical Modeling.The following conclusions are obtained:(1)The characteristics of groundwater level.Affected by coal mining,the water level of Wugou Coal Mine rises first,then falls and finally stabilizes,with small overall variation and weak influence by mining.The water level of the fourth aquifer is little affected by early mining activities,but it is relatively unstable.With the water outflow from some goaf,the water level of the fourth aquifer bearing water content decreases rapidly in the middle period,which has been maintained at a low level in the last two years.The water level of the Taiyuan limestone aquifer and the Ordovician limestone aquifer fluctuates frequently and irregularly in a small range in the early stage,and tends to be stable in the later mining period.In the water level space of each aquifer,the eastern water level in the early stage of the fourth aquifer of water cut is more than that in the northwest,and it turns into the later stage of the southern water level and the northern water level,which shows a funnel type distribution around the range of the first and second mining areas,and the other areas with small drop degree.The water level of the Taiyuan limestone aquifer has declined as a whole,but the water level changes little in spatial relation,and it is opposite to the mining activity area.The water level of the Ordovician limestone aquifer does not change obviously in space.(2)The chemical characteristics of groundwater.TDS is increasing with the increase of burial depth.The cation size relationship in the study area is Na+>Ca2+>Mg2+.In the anion,the relationship between water of the fourth aquifer is HCO3->SO42->Cl-,the coal series water is SO42->HCO3->Cl-,water of the Taiyuan limestone aquifer and the Ordovician limestone aquifer are SO42->Cl->HCO3-,and the ion content of each aquifer is slightly different.In terms of source,Cl-mainly is salt rock dissolution.Na+ contains alternative adsorption of salt rock and cation,and other potential alkaline minerals.Ca2+,Mg2+ are the dissolution products of sulfate and carbonate minerals,but under the action of cation adsorption,they are consumed by different processes,and their activity is reduced.HCO3-source is rich,but mainly is dissolution of surrounding rock minerals.SO42-except for the dissolution of general sulfate minerals,Pyrite is oxidized due to human influence,which is rich in coal series and ash water.(3)The influencing factors of water level of each aquifer are determined,and the factors are divided into quantifiable control factors and non quantitative control factors based on the characteristics of each factor.The qualitative factors were analyzed by AHP.The results showed that the weight of structure control,drainage water and grouting sealing holes in mining area were 0.3553,0.2843 and 0.1421 respectively,which were the main factors affecting the water level and seepage field.The seven quantitative factors were analyzed by using random forest modeling,among which the average inflow water,unit goaf area and mine development length were the most important factors affecting the water level of limestone aquifer,including the unit goaf area and the lowest mining elevation.Because of the highest proportion of structural factors,the paper analyzes it separately,and finds that syncline and fault have great influence on the fourth aquifer and the coal measures system respectively,and that the Taiyuan aquifer and the Ordovician aquifer are relatively small under structural control.(4)The hydrochemical formation of groundwater is determined.Water of the fourth aquifer is more inclined to the horizontal axis of "Desulphite",but it is generally stable.The coal series water is more inclined to "Hardening" and water of the Taiyuan aquifer tends to "Desulphite".The saltation process occurs in all mining areas and runs through the whole process of groundwater chemistry.The composition of groundwater in the fourth aquifer and the Taiyuan aquifer in the study area is mainly composed of Calcite,Dolomite,Anhydrite and other sedimentary rock clay minerals,but there are some differences in the strength of the action.With the deep burial depth and the influence of further mining,the SO42-content in the groundwater of the Taiyuan aquifer increases,Ca2+,Mg2+precipitates,and the water body increases and concentrates continuously.Along with the dissolution of rock salt and cation alternative adsorption,it finally becomes the high salinity water dominated by Cl-Na.Figure:38 Table:8 Reference:81... |
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