Deformation characteristic of key strata and control effect of surface subsidence in mining with grouting into overburden bed-separation

In order to study the deformation characteristic of key strata and control effect of surface subsidence in mining with grouting into overburden bed-separation, and predict the surface movement and deformation accurately, the mechanical analysis of key strata deformation was carried out based on the elastic foundation beam theory, and the combination of filling body in bed-separation and coal-rock mass under the key strata was divided into solid coal area, under-compaction area and compaction area, of which the deflection equation of each section of key strata and the calculation method of elastic foundation coefficients were given respectively; By means of simulation layer-by-layer, numerical simulation on the deformation of key strata and surface subsidence in mining with grouting into bed-separation was carried out, the development characteristics of bed-separation, the fracture characteristics of key strata, and the surface movement and deformation characteristics under different injection-production ratios were studied; The bending subsidence space of key strata in mining with grouting into bed-separation was regarded as the mining space with reference to the theory of equivalent mining height, and the surface subsidence prediction model suitable for mining with grouting into bed-separation was established, combined with the probability integral method. It was verified in a mining face with grouting into bed-separation in Huaibei Mining Area, the results showed that the face width should be designed within the range of 90-120 m under the geological condition in the study area; The average error between the predicted value and the measured value was 9 mm, within the allowable error range; The surface subsidence control effect of mining with grouting into bed-separation was remarkable, and the subsidence reduction rate was about 83%.