Abstract: To research the failure characteristic of coal seam floor with a certain dip angle, based on the theories of ground pressure, a mechanical model of workface lateral floor was established by considering the dip angle of coal seam, and the calculation formula of the maximum failure depth of workface lateral floor was deduced based on the Mohr-Coulomb yield criterion. The mining-induced failures in floor can be divided into three zones along the inclination, and the failure forms present a “spoon-shaped” state, which is larger than the width of workface. Finally, the influencing laws of dip angle on floor failure depth, failure form and the position of the maximum failure depth were simulated by FLAC3D. The results show that: 1) the plastic failure depth of floor increases with the increase of workface width, and increases first and then decreases with the increase of coal seam dip angle. It will reach the maximum failure depth at 30°, and is more likely to induce shear sliding failure; 2) the maximum plastic failure depth position of coal seam floor gradual deviates from the middle of workface and downward with the increase of dip angle of coal seam, and the wider the workface, the farther the deviation.

Key words: dip angle of coal seam, mining floor, failure depth, failure form