To investigate the mechanisms of floor failure and further induced risks of water inrush by the strong unloading effect of high-stress rock mass in deep coal mining

the influence of unloading on floor disturbance and failure was analysed with the theory of unloading rock mass mechanics. It calculated the strong disturbance characteristics of floor rock mass unloading damage in deep coal mining by using the discrete element method (DEM). Based on triaxial unloading tests and the concept of damage factor

we obtained the relationship between unloading percentage and damage factor

determined the propagation and failure condition of rock mass

and achieved the unloading disturbance partition of floor. Then the disturbance hazard of floor rock mass unloading damage and failure in deep coal mining were further studied. The results show that with mining depth increasing

both unloading starting point and unloading stress of floor are increased

but the unloading percentage is reduced

in which the lower unloading percentage causes damage severely in deep coal mining. When the unloading percentage of rock mass is greater

its unloading rate and displacement and the permeability coefficient become higher

which easily induces floor rock mass instability propagation. When the dip angle of crack and the ratio of horizontal stress and vertical stress are low

it easily reaches the propagation and failure conditions of floor rock mass unloading.