A geological assessment method of floor water inrush risk and its application

The risk assessment of floor water inrush is essential to assure the safe production in a coal pit. Floor aquifuge is the key factor controlling water inrush. Both the impermeability and the resistance to water pressure of an aquifuge vary with its lithology and structure features. With the increase of mudstone content, the permeability and resistance to water pressure of the floor drops. The dense tectonic fissures in floor will transform intact, blocky structure into very blocky or blocky/disturbed structure, lower the resistance to water pressure, increase the permeability of floor aquifuge, and thereby will raise the risk of water inrush. Considering the lithology and structure features, and based on a conventional water inrush coefficient, a coal floor water inrush risk assessment method is put forward. With Fangezhuang coal mine of China as a case study, the implementation of this method is elaborated.