Mechanical analysis of fracture process of key strata in surface-underground combined mining

In the process of the surface-underground combined mining, the fracture development of strata has important influence on layout of roadways and stability of the mining slope. Based on a pratical engineering in Pingshuo Mining Area, key strata theory is applied, and the key stratum is regarded as a thick rectangular plate on elastic foundation, then a mechanical model is built. Formulas for calculating the stress and deformation are derived by using the reciprocal theorem method on the basis of Reissner's theory. Combined with engineering examples, stress and deformation characteristics of the key strata when the working face advances are revealed.