Study on the mechanism of deep and large fracture propagation and transfixion in karst slope under the action of mining

In order to study the failure mechanism of the high and steep karst slope under the action of mining,the development law of the slope fracture under the action of mining is studied by using the numerical simulation of universal distinct element code (UDEC). The results show that the mining action has an important influence on the stability of karst slope,which is mainly manifested in the development of new fissures in the overlying rock mass of the coal seam and the expansion and connection of the original fissures in the slope body; the development of the internal fissures in the slope body has a certain time-space effect,and the height of the fracture zone increases with the extension of the mined-out area; the original deep fissures in the slope body have certain damage on the slope body. Under the control action,when the slope is damaged,the landslide body will slide along the main control fracture; under the two-dimensional condition,the karst slope body with deep and large fracture will form a similar "cantilever beam structure" under the action of mining,the cantilever beam structure will break along the main control fracture,the soft rock in the middle of the slope body will be extruded,and finally the main fracture and the free face will expand and connect,and the slope body will collapse.