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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]

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]