Study On Water Circulation Mode Of The Main Discharged Aquifers In Suixiao Coal-Mining District Based On Hydrogeochemical Characteristics

Affected by mining activities and the gradual increase of mining depth,the structure of groundwater systems in many types of aquifers in coal fields has been generally destroyed,and the circulation mode has changed,resulting in frequent occurrence of water inrush accidents in coal mines.Taking the Huaibei coalfield Yanxiao mining area as a research example,this paper selected Hydrogeochemical data of the unconsolidated pore aquifer of Cenozoic group,the fissured sandstone aquifer of Permian system in the coal seam roof and floor,and the karst fissured limestone aquifer of Carboniferous Taiyuan formation and Ordovician system in the coal seam floor.Multivariate statistical analysis of conventional ions revealed the mechanism of water-rock interaction and spatio-temporal evolution of groundwater in the district.Combined with analysing the distribution characteristics of stable isotope and Sr element,the water circulation mode on a typical profile was established.At the same time,the spatial distribution characteristics of rare earth elements and other trace elements in each aquifer of the mining area were judged to indicate the effect on water-rock interaction and circulation mode.By analyzing the distribution characteristics of hydrogen-oxygen stable isotope and Sr element,the sandstone aquifer in the mining area received the infiltration and recharge of atmospheric precipitation after evaporation,and the limestone aquifer receives direct infiltration replenishment without atmospheric evaporation.Runoff from east to west.The conventional ion multivariate statistical analysis showed that the oxidation and cation alternate adsorption of pyrite in the sandstone aquifer of the mining area were strong in the middle and weak in the west;the hydrochloric acidification of limestone aquifer,the oxidation of pyrite and the alternating adsorption of cations were weak in the west and strong in the east.The eastern part of the mining area was almost water-free and acts as a water supply area.From the above conclusions,the groundwater circulation mode in the district was near the eastern Huangzangyu anticline and the Xiangshan-Xiaoxian anticline,the atmospheric precipitation directly supplied the limestone aquifer,and the runoff from east to west,limestone and sandstone The hydraulic connection between aquifers was weak.The central and western parts of the district were not directly recharged by atmospheric precipitation,and there was only a certain degree of hydraulic connection between sandstone and limestone aquifer.The geochemical parameters of rare earth elements were analyzed by principal component analysis,and compared with the conventional ion principal component representing water-rock interaction mentioned above.It was found that the parameters(La/Yb)_N,(La/Sm)_N and(Gd/Yb)_N were mainly affected by the carbon salt acidification of groundwater,while the Eu and LREE/HREE were mainly affected by the alternating adsorption of cation and pyrite oxidation.Among other trace elements,the distribution rules of Li,Rb and Mn were basically consistent with the spatial evolution rules of carbonate acidification and pyrite oxidation in the mining aquifer,which can be used to indicate the carbonate acidification and pyrite oxidation.The content distribution of Mo and V indicated the simple carbonate leaching.The content of Ba can be used as a reverse indicator of cationic alternating adsorption.The research results are expected to provide theoretical basis for hydrogeochemical exploration of concealed coal mines in China and establishment of water inrush early warning systems.