Research on the deformation mechanism of high steep reverse inclined composite slope under disturbance of end slope mining

As a new method for mining end slope coal, in order to explore its impact on the deformation of high steep reverse inclined composite slopes, taking a certain open-pit mine as the engineering background, the deformation and failure characteristics of coal pillar groups and slopes after end slope mining are analyzed. The results show that after the end slope coal mining, the nonlinear distribution of gravity and the boundary conditions of simply supported on two sides and fixed supported on one side change the stress deformation characteristics of the composite slope. The deformation of the end slope is mainly in the horizontal direction, and the deformation of the waste dump is mainly settlement. Along the dip direction, the vertical displacement and stress curves of the coal pillars change from gentle to steep. Near the coal wall side of the center, the horizontal displacement gradually attenuates, and the degree of plastic failure decreases. Along the strike direction, the deformation of the coal pillar group is saddle-shaped. The edges of the permanent coal pillars are deformed into an arch-shaped distribution under shear action. A stable rock mass structure is formed above the single mining roadway and the coal pillar group. The roof stress is distributed in an arch shape, and the plastic zone expands from the center to both sides. The deformation of the composite slope is divided into a violent deformation zone, a slow deformation zone, and a stable zone. The deformation of the slope front changes from parallel to the slope surface to oblique intersection. The roof of the mining roadway changes from arc-shaped shear-out sliding to settlement. The deformation and failure mode changes from arc-shaped sliding caused by gravity to large-scale fold-shaped sliding caused by the settlement after the failure of the coal pillars. Thus, it can be concluded that end slope mining makes the deformation of the composite slope mainly settlement, which is distributed in the waste dump and the end slope in a zoned manner, intensifying the deformation of the slope in the mining area. The deformation of the coal pillars is the key to the stability of the composite slope. The stress, deformation and mining depth have a non-linear relationship and are asymmetrically distributed. The degree of damage decreases. The peak points of vertical stress and displacement are close to the working face, and the horizontal displacement decreases non-linearly. The non-linear distribution of slope gravity caused by the steep then gentle structure of the composite slope and the reverse inclined characteristics of the coal seam, as well as the differences in boundary conditions caused by end slope mining, are the main reasons for the deformation and failure of the coal pillars and slopes.