Mechanism of the slope failure of horizontal thick coal seam under the condition of combined mining

Through two methods of numerical simulation and similar simulation, the failure problems of the open-pit slope under the condition of combining open-pit mining with underground mining were analyzed and discussed. The results show that the failure of the open-pit slope is a gradual process, in order to guarantee the normal open-pit mine production works well, the explored boundary must be controlled well by the vertical stature of safe mining. By the analysis of the similar simulation, the mining order is optimized.