| As the one of the most important energy base, North-China-Type coalfields is faced with the increasing water harmful threaten as a result of the coal production trend to deep development.For this reason, to master the hydrogeological conditions of deep coalfield and to effective avoid the water harmful has become an important issue of a guarantee to safety in production. Using hydrogeochemical methods to study the hydrogeological conditions in aquifer system which is closely related with the deep seam mining, learn more about the dynamic field of water chemistry and water features, predict and evaluate the water yield property as well as the changes and distribution in water chemical composition in karst aquifer, is a important way of preventing water inrush and ensuring coal production.Thesis aims to study the basic hydrogeochemical characteristics of deep karst aquifer system. It starts with the mineral composition of aqueous medium, chemical composition of groundwater, redox environment, mass material conservation and chemical equilibrium, to establish hydrogeochemical model for showing the distribution of groundwater chemical field in deep karst groundwater, describing the process hydrogeochemical evolution, analyzing the hydraulic connection between aquifers and the effect of fault conducted water, emphasizing on geochemical evolution of Ordovician limestone groundwater and explaining the causes of groundwater hydrochemical characteristics.Study area is located in Yanzhou Coalfield, the Southwestern Shandong Province, and the three adjacent coal mine are Xinglongzhuang, Baodian, Dongtan. There have rich borehole data, and the deepest drill hole data up to 1000 meters above. The aquifers of closely hydraulic connection with down-group coal seam that preparing to mining are the tenth limestone aquifer, the thirteenth limestone aquifer, the fourteenth limestone aquifer and the bottom Ordovician limestone aquifer. View from the horizontal distribution, chemical field with the groundwater flow field changes regularly, Ca2+ and SO42- on the contribution of salinity is markedly increased from north to south along the groundwater flow direction overall. View from the vertical distribution, from top to bottom, chemical types of groundwater is transit from Na-K-HCO3 type to Ca-SO4 type.Based on the groundwater chemistry and kinetics character, it choose reaction pathway and possible mineral phases, using PhreeQC software to modeling inverse hydrogeochemical simulation, showing main water-rock interaction and water chemistry variation in runoff area, drawing to following conclusion:(1).The main water-rock interaction of Ordovician limestone water along runoff direction is the calcite precipitation, the solution of dolomite, anhydrite and halite, cation exchange and the solution or escape of carbon dioxide and so on. (2).Ordovician limestone water’s salinity is increasing along groundwater flow direction, due to the solution of the mineral phase containing Ca2+、Mg2+、Na+、SO42- and Cl- along the way, moreover, the dissolution rate greater than the precipitation rate. (3).Combine with mentioned above, to discuss the hydraulic connection between aquifers and the influence of local structure. It considered that the hydraulic connection between aquifers is weak overall, regional normal fault has certain water conductivity. It has limited impact to complete hydrogeological units with changing the boundary conditions in the study area. More developed fracture network of local karst areas has hydraulic connection. It needs adopt relevant measures to preventing water inrush when exploiting nearby coal seam. |
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