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Water-inrush accidents often occur when coal seams are mined with thin water-resisting layer and high confined water. To prevent water-inrush from coal seam floor, based on the analysis of the characteristics of Ordovician limestone (OLS) karst in Feicheng mining area, a series of key technologies or methods for OLS aquifer were studied in this paper. First, the grouting area of the working face floor was determined by the water-inrush coefficient. According to the given formula of water bursting coefficient, the formula for calculating the thickness of reinforced aquifers by grouting was deduced. Second, the ‘three-stage casing’ drilling with small angle was designed for fully grouting in the OLS. Finally, the 3D DC mine resistivity method was used to check the effect of grouting for the working face to ensure the grouting quality of the floor. Through the case study, it shows that the technology elaborated has better practicability and popularization. [ABSTRACT FROM AUTHOR]

The roof and floor of a water-rich area can be explored using traditional two-dimensional (2D) electrical resistivity tomography (ERT), but this method cannot be applied to a water-rich internal working face. In this paper, the resistivity of an internal working face was determined using 2D ERT by laying electrodes and cables in two adjacent roadways and using an equatorial dipole device. The water inrush process of the goaf floor in the study area was monitored with pre-implanted electrodes and cables at the front of the mining working face and was analyzed using the processed results of four acquired data sets. The location of the water inrush from the floor was determined based on the change in the resistivity of the floor and the hydrological variations at the observational hole, which provided the basis for how to stop the water inrush. [ABSTRACT FROM AUTHOR]

A risk evaluation method based on principal component analysis, fuzzy mathematics, particle swarm optimization, and support vector classification, is proposed due to the limitations of the water inrush coefficient method. The many factors that influence coal floor water inrush were categorized as structural, hydrogeological, coal seam occurrence and mining condition principal components, according to principal component analysis, among which the structural and mining condition components were the most important. The principal component factors were then fuzzified. Finally, an evaluation method was established, with the parameters of the supporting vector classification optimized through the particle swarm algorithm. The validity of the method was demonstrated by comparing its predictions with actual conditions at ten coal seam mining faces. [ABSTRACT FROM AUTHOR]

On the basis of the analysis of fault distribution characteristics in the Liangzhuang minefield, the site, channel, site distribution, and probability of karst water inrush from the Ordovician limestone affected by fault type, fault drop and fault dip is expounded. First, authors introduce methods of fault influencing factors and fault fractal dimension by synthesizing these faultage elements mentioned above. Next, the quantitative study of fault development characteristics in the Liangzhuang minefield is carried out using nonlinear theory, which reveals the intrinsic relationship between fault and karst fissure developing in the Ordovician limestone. Ultimately, through a combination of microslice identification and macrogeophysical analysis, the horizontal and vertical distribution regularities of Ordovician limestone karst fissures in the Liangzhuang minefield are studied, that is, the horizontal distribution shows discontinuity, and the vertical distribution shows relative continuity from the top interface of Ordovician limestone down the depth from 10 m to 40 m. This research can play an important guiding role in predicting water inrush from the Ordovician limestone karst during mining deep coal seam. [ABSTRACT FROM AUTHOR]

• Interval extended by TFN is used to determine the 2-tuple weighted vectors. • 2-tuple water-richness evaluation model is built by an extended ITL-VIKOR using TFN. • Model is verified by three dimensional high-density resistivity method. • Water-richness evaluation is extended to binary pattern for the first time. Jiaozuo coalfield is the most typical in Northern China type coalfield. When it mined the Permian coal seams, it was threatened by water inrush from the confined aquifer of thin karst fissure limestone in the lower Carboniferous. How to scientifically evaluate and predict the water-richness of thin karst fissure limestone in Carboniferous system has become the most important work in mine water control and prevention. Taking the mining of coal seam No. 2 1 of Shanxi Formation in Guhanshan coal mine as an example, this paper analyzed the water-richness main controlling factors of L 8 Limestone Aquifer of Taiyuan Formation, and selected four evaluation indexes, i.e. water inflow of drilling, the thickness of L 8 Limestone Aquifer, the water level of L 8 Limestone Aquifer and fault fractal dimension. The 2-tuple linguistic weights of all factors were obtained by the use of interval 2-tuple linguistic method extended by triangular fuzzy numbers. Following the above outlines, the mathematical model for the 2-tuple linguistic evaluation of water-richness was established based on ITL-VIKOR method extended by triangular fuzzy numbers. The data of geophysical exploration were collected to test the accuracy of the model. In addition, the results of 2-tuple linguistic assessment of water-richness and geophysical exploration were used to evaluate the water-richness of L 8 Limestone Aquifer, which extends the evaluation and prediction of water abundance for karst fractured aquifers to dyadic array. These results have been applied to guide the safe mining in Guhanshan coal mine, and will be further extended to the mines with similar geological conditions. It is our goal to establish an intelligent application system to ensure safe production in coal mines, which is great beneficial to the technical personnel engaged in mine water prevention and control. [ABSTRACT FROM AUTHOR]

Accurate prediction of the water-bearing capacity of aquifers is crucial for protecting the surface ecological environment and ensuring safety during coal mining. In this study, a macro–micro combination was used to investigate the water-bearing capacity of bedrock aquifers. At the micro-level, the micro pore parameters of various sandstones were determined through cast sheeting. At the macro-level, the porosity and water absorption rate of various sandstones were determined experimentally. After that, a new index weighting method was proposed to comprehensively evaluate the water-bearing capacity index of sandstone. According to this method, the water-bearing capacity of aquifers in the Guojiahe coalmine were evaluated. The research results revealed that the water-bearing capacity of sandstone was mainly related to its pore connectivity, and the water-bearing capacity of sandstone in the Luo'he and Zhi'luo formation was considerably greater than that in the Yan'an formation. The water bearing capacity of strata in the eastern part of the mining area is lower than that in the western part of the mining area. The research results can provide considerable money savings for coal mining and protect the ecological environment and groundwater resources in the region. [ABSTRACT FROM AUTHOR]