LAUSR

In order to obtain separation space distribution of horizontal overburden combinations, the contact elements were set in the interface of the rock layers according to the different bending stiffness of overburden combinations. The expansion of rock layer was considered. And the mining step spacing was set according to the initial caving span and period weighting span of the main roof. The failure characteristics of overburden rock and the development of filling separation space of different overburden combinations were analyzed by numerical simulation. It was shown that the lateral pressure of coal wall of the upper-soft and lower-hard overburden combination was the largest. The lateral pressure of coal wall of the upper-hard and lower-soft overburden combinations was the smallest. The tensile stress arch gradually developed from the center of the goaf to both sides of the goaf. Two “saddle” areas with concentrated tensile stress arches were formed on the inside of the goaf. Due to the difference in the bending stiffness of rock layers, the volume of the fourth separation space at 250 m was the largest and it was suitable for separation filling. The volume of the third separation space at 220 m was the smallest. The first, second and third separation spaces were too close to the water flowing fractured zone and the three separations could be considered as the unfilled separation spaces.