Abstract: Considering the combined effect of mine pressure and water pressure of confined aquifer under the water-resisting floor, water pressure expression of floor water inrush has been derived. And then the most dangerous shear fracture plane and the critical pressure of water inrush have been obtained by trial calculation. Based on the proposed analytical solutions, the effect law of distance between cut-hole and fault zone, fault dip, advancing direction of face and lateral pressure coefficient on critical pressure of water inrush have been analyzed. The results show that the critical pressure of water inrush decreases gradually with the increase of distance between cut-hole and fault zone. With the decrease of fault dip, the critical pressure of water inrush decreases firstly, and then increases gradually. However, floor failure is not along the fault surface any more when the fault dip is less than a certain critical angle. When the working face advances from the lower wall of fault to the upper, the critical pressure of water inrush is higher than the opposite, namely the working face advances from the upper of fault to the lower. But no matter in what direction the working face advances, the critical pressure is reducing with the increase of distance from working face to the fault zone gradually. The critical pressure of water inrush increases first and then decreases with the increase of lateral pressure coefficient. The application demonstrates that the calculation results of the critical pressure accord with the actual situation.

Key words: limit equilibrium theory, floor water inrush, fault, critical pressure of water inrush