Failure behavior and simulation analysis on coal and oil shale combined mining through ascending unloading mining method

Based on the engineering background of Beizao Coal Mine in Longkou, the ascending combined mining method of coal and oil shale is put forward in this paper. The key problems of combined mining on coal and oil shale include the failure mechanism and post-peak strength characteristics of oil shale,mining face layout and surrounding rock control,the mining discontinuous deformation analysis of oil shale etc. The oil shale will fail after the excavation of coal,and then be compacted. The strength of failed oil shale will increase with compacting. Therefore,the oil shale can be mined at a reasonable range of strength. Research indicates that the reasonable spacing range of layers is about from 13. 2 m to 32. 9 m for the ascending combined mining of coal and oil shale in Beizao Coal Mine. MDDA program has been used to simulate the combined mining of coal and oil shale. Simulation results indicates that the oil shale mining face can be arranged behind the coal mining face more than 125 m. The combined mining of coal and oil shale has been successfully applied in Beizao Coal Mine,which achieved good economic benefits and realized sustainable the development of the coal mine.