| It has a mining history of more than 60 years for Xinzhi Coal mine.Due to the complex geological structure and the uneven lithology of the formation,the underground water quality of the main aquifer and the hydrographic environment are complex and variable,which makes it difficult to accurately identify the water inrush from underworkings.Therefore,it is of great theoretical and practical significance to study the characteristics of water quality of main aquifers and the interaction process of water and rock,as well as the method of judging water inrush from underworkings in Xinzhi coal mine.Based on the study of hydrogeological data of Xinzhi coal mine and 62 reports of mine water quality,the water chemistry characteristics of the main aquifers were studied by analysis and testing of 15 core samples and 20 mine water samples.The mine water and the water inrush samples were distinguished by the conventional water source discrimination method,the improved gray correlation degree discriminant method and the fuzzy comprehensive discriminant method.The water-roek interaction mechanism of the four main aquifers in Xinzhi coal mine was studied by free drainage column leaching experiment and PHREEQC software.The Permian Ks sandstone core sample of Xinzhi coal mine mainly contain quartz,clay minerals and plagioclase.The local parts of the formation may contain a small amount of sulfate and chloride salts.The Permian K8 sandstone fissure aquifer has three key features,which are(1)the water chemical type is HCO3-Na,(2)the milligram equivalent percentage of sodium ion is greater than 96%,(3)the ratio of ?Ca/?Cl less than 1.The K3 limestone core samples of the Carboniferous Taiyuan Formation are mainly calcite(92%),dolomite and quartz.There may be a small amount of sulfate with evenly distributed in the fonnation,and the sulfate may be Na2SO4.The key features for the Carboniferous Taiyuan Formation K3 limestone aquifer are the water chemistry type with SO4-Na type and the ratio of ?Ca/?SO4 less than 0.5.The mineral composition of the K2 limestone core sample of the Carboniferous Taiyuan Formation is calcite(73.8%),clay minerals and quartz.The water chemical type in this aquifer is SO4-Ca·Mg.It indicates that gypsum and magnesium-containing minerals(such as dolomite)are evenly distributed in the rocks which groundwater flows.The limestone core sample in O2f Fengfeng formation of Ordovician consists of 98.4%calcite and 1.6%pyrite.The water chemistry types of this aquifer are complex,including SO4-Ca·Mg type and HCO3-Ca Mg type.It indicates gypsum,dolomite or other magnesium-containing salts are distributed in this stratum.The runoff circulation velocity and redox conditions of the O2f limestone aquifer in the Fengfeng Formation are different in different sections,resulting in a relatively large range of total dissolved solids content of the aquifer.The K2 limestone and O2f limestone aquifers cannot be effectively distinguished by the method of constant component,trace component and proportional coefficient.The results of free drainage leaching experiments show that:(1)the water chemistry type of all leachates are SO4-Ca type,and the equivalent percentage of calcium and sulfate ions in all leachates exceeds 74%and 40%,respectively.(2)four core samples contain a certain amount of sulfate,which can reasonably explain that the actual water samples of the K3,K2 and O2f limestone aquifers are all sulphate-type groundwater;(3)the order of anion content in K8,K3,K2 and O2f core leaching filtrates is:SO42->HCO3->Cl-,and the order of cation content in K8,K3,K2 and O2f core leaching filtrates are in the order of Ca>Mg>K>Na,Ca>Na>Mg>K,Ca>Mg>Na>K and Ca>Mg>K>Na;(4)the content of Fe,Mo,Sb,U and Sr in K2 and O2f limestone leaching has a good regional division.The Fe ion concentration in O2f limestone leachates is significantly higher than that in K2 limestone leachates,while the concentration distribution law of Mo,Sb,U and Sr ions are opposite to that of Fe ion.This feature can be used as a reference factors to distinguish the samples without desulfurization in K2 and O2f limestone aquifers.The main water-rock interactions in the K3 limestone aquifer of the Taiyuan Formation are the dissolution of calcite and dolomite minerals,and the dissolution of sodium sulfate.The main water-rock interactions in the K2 limestone aquifer of Taiyuan Formation are the dissolution of calcite and dolomite minerals,the dissolution of sulfate,and the different degrees of desulfurization.The main water-rock interactions in the O2f limestone aquifer of the Fengfeng Formation are the dissolution of gypsum,calcite and dolomite minerals,the dissolution of sulfate,and the desulflurization reaction in a reducing environment.According to the PHREEQC simulation results,the water quality characteristics of the BC2 water sample and the AK10 water sample mixed according to the ratio of 7:3 are consistent with the AC7 water sample,that is,the AC7 water sample is a mixed water sample of the K2 and K3 limestone aquifer.The forward and reverse simulations of PHREEQC software show that the solid phase materials involved in water-rock interaction are not only the minerals detected by the core samples,but also the undetected sulfates such as NaSO4 and CaSO4 are also involved in the reactions.Only by adding these sulfates,the water quality of the water samples simulated by PHREEQC sof'tware can be close to the actual mine water samples.This software simulation conclusion is completely consistent with the conclusions of leaching experlments and water chemistry inference.In the PHREEQC softrvare process simulation,it is recommended to use reverse simulatlon to determine the types of minerals that may be involved in water and rock interactions,and forward simulation as the main simulation method.Only in this way,the simulation results can be more objective and accurate.The accuracy of the gray correlation degree method for the water samples of 45 mines in Xinji Coal Mine is 95.6%.In this study,the milligram equivalent concentration and milliequivalent percentage of 7 constant ions(K+,Na+,Ca2+,Mg2+,Cl-,SO42-,HCO3-),the proportion coefficient of ?Ca/?Cl and ?Mg/?Cl were used as the evaluation factors of fuzzy comprehensive evaluation model,and the accuracy of identification was increased to 100%,and the identification of three water inrush water samples was also completely accurate.Therefore,this method can be used as a reliable discriminant method for water inrush source in Xinzhi Coal Mine.Based on the national and Shanxi regulations on coal mine water prevention and control,combined with the hydrogeological conditions,mining characteristics and mine water characteristics of Xinzhi Minefield,and the research results of the paper,a water safety management system suitable for the Xinzhi Coal Mine has been established.The system includes a water disaster prediction and forecasting system,a water source water source discrimination management system and a water inrush treatment management system.The management system effectively compensated for the problem of insufficient identification and management of water inrush water in Xinzhi Coal Mine. |
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