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The water quality parameters of the K2 limestone aquifer of the Carboniferous Taiyuan Formation and the O2f limestone aquifer of the Ordovician Fengfeng Formation overlap each other in the Xinzhi coal mine,China.Therefore, the two water sources cannot be effectively discriminated by the conventional discriminating methods. In order to solve the problem of water source discrimination and reveal the water-rock interaction mechanism of the four main aquifers in the Xinzhi coal mine, this paper conducts a free draining column leaching experiment on the core samples of four main aquifers in Xinzhi coal mine. The results show that (1) the core samples contain sulfate of non-mineral phase, and the four main aquifer formations also contain sulfate and gypsum minerals, which cause the leachate and limestone aquifer water samples to be rich in sulfate ions;(2) the equivalent percentages of SO2-4 and Ca2+ ions in the K8, K3, K2 and O2 core leaching filtrates exceed more than 74% and 40%, respectively, and the corresponding water chemical types of all leaching filtrates are SO4-Ca type;(3) the order of anion content in all leaching filtrates is:SO2-4>HCO-3>Cl-, the order of cation content in the K8,K3,K2 and O2f core leaching filtrates are Ca>Mg>K>Na, Ca>Na>Mg>K, Ca>Mg>Na>K and Ca>Mg>K>Na,respectively;(4) the contents of Mo, Sb, U and Sr in K2 limestone core samples and leaching filtrate are higher than those in Ordovician O2f limestone core samples and leaching filtrate,but the distribution of Fe ion content is opposite. These characteristics can be as a reference factor for distinguishing K2 and O2f limestone aquifers. The water chemistry characteristics of the aquifer in Xinzhi Coal Mine are controlled by lithology, burial conditions, groundwater recharge and hydrodynamic conditions.Therefore,the actual water quality of the aquifer is more complicated and changeable than the leachate.The water chemical types of K8 sandstone aquifer and K3 limestone aquifer are HCO3-Na and SO4-Na, respectively, which are different from the corresponding leachate water chemical types.However, the water chemistry types of the K2 and O2f limestone aquifers are generally the same as the corresponding leaching filtrates.The main water-rock interaction in the Permian K8 sandstone aquifer is mainly dissolved plagioclase, and a small amount of sulfate dissolution reaction may exist in some areas. The water-rock interactions in the K3 limestone aquifer of the Taiyuan Formation are mainly the dissolution of calcite and dolomite minerals, as well as the dissolution of some sulfates and sodium salts. The main water-rock interactions in the K2 limestone aquifer of the Taiyuan Formation and the O2f limestone aquifer of the Ordovician peak group are the dissolution of calcite, dolomite and sulphate,and the desulfurization occurring in local area. [ABSTRACT FROM AUTHOR]

The permeability and mechanical strength of rock mass after grouting is an important parameter to reflect the grouting effect of rock mass. In order to quantitatively evaluate the effect of grouting water plugging project, taking the water plugging project of special large water inrush from Ordovician limestone of a mine in Anhui province as an example, this paper puts forward a method of high pressure borehole water pressure test to quantitatively evaluate the blocking source grouting effect of the Taiyuan formation limestone C53 . In view of the drastic change of rock mass permeability during high pressure water pressure test, the permeability coefficient of rock mass is calculated by the turbulent seepage law. The results show that the Taiyuan formation limestone C53 after grouting exhibits a good water resistance performance and the behavior of high water anti-pressure and low permeability. It means that the blocking source grouting has a good effect. The mechanical strength of rock mass to resist hydraulic fracturing can be judged by its critical impermeability strength. The calculated critical impermeability strength of the Taiyuan formation limestone C53 after grouting is 1. 83 MPa per meter. Based on the test principle of the energy dissipation test of water resistance coefficient, the Taiyuan formation limestone C53 after grouting is enough to resist the splitting failure of Ordovician limestone water with 5. 64 MPa pressure, and it can eliminate the threat of water inrush from Ordovician limestone in the coal seam floor, as well as it can achieve the purpose of the blocking source grouting project. [ABSTRACT FROM AUTHOR]

To study water features and hydrodynamic conditions of the No. 15 Taiyuan formation coal reservoir and its roof limestone in the southern Qinshui basin, this paper collected 51 water samples from the river, coal-bed methane well drainage, coal reservoir and its roof limestone in the South Shizhuang region. Measurements of hydrogen and oxygen isotope and main ion concentration in the water samples show that the water discharged from CBM wells is a mixture of coal seam water and roof limestone water. The No. 15 coal seam has a strong hydraulic connection with the roof limestone fracture aquifer, and receives substantial recharge from roof limestone water. The sealing ability of the roof limestone fracture aquifer is weak, and the runoff speed of water in the limestone fracture is fast. Roof limestone water demonstrates a drift of 18O, and the water that is discharged from the CBM wells of the No. 15 coal seam has the drift of both of 18O and D. At the same time, water discharged from the CBM wells of the No. 3 coal seam mainly demonstrates a drift of D. All the water discharged from the CBM wells present a positive correlation with salinity (TDS), and the data of δD and δ18O can be used as reference factors for judging the runoff, conditions of coal seam water. [ABSTRACT FROM AUTHOR]