Identification of the Mechanism of Water Inrush from Coal Floor Based on Geological Conditions and Numerical modeling Technology

Abstract In North China, Water inrush from the Ordovician limestone aquifer often occurs when deep coal seams are being mined due to the complicated geologic conditions and the limitations of existing detection methods. In order to deeply explore the water inrush mechanism, prevention methods, and the safe production guidance, taking the water inrush accident in the floor of the 2-112 mining face of the Ganhe coal mine in Shanxi as an example, the authors established a stress distribution model for the coal floor and used simulation method to study the water inrush process in the floor of 2-112 deep mining face. The results showed that under the condition of no geological defects in the coal seam floor, water inrush from the floor will not occur, which suggests there must be geologic defects in the floor, if water inrush occurs. According to the actual conditions and the response phenomenon of water inrush, through repeated simulation and identification, the results indicate that there is a concealed fault defect in the floor of the working face, the depth of which is about 10m under the coal floor, and the extension length is about 86m, and the inclination angle is about 70 degree. Under the coupling effect of ground stress, hydraulic pressure and mining action, the concealed fault is activated, and the plastic zone of the floor plate is enlarged, then a connected flow channel is formed. Consequently, the water inrush occurs driven by high hydraulic pressure.