Research Of Deformation Mechanism Of Mining Overburden Separated Strata

The coal measures stratum are characterized by the bedded sedimentary rock.When coal masses are extracted, the separated strata in the overburden is an inevitable phenomenon.The development of the separated strata follows the specific time-space law. As long as we obtain concordant relation among the evolution of the separated strata and their macroscopic, midscopic structures,the time-space law of the separated strata heights widtlu length and flexibility are obtained, the new technology of being in separated strata grout to slow down the subsidence is efficient absolutely.The technology of the separated strata grout to slow down the subsidence has been applied tentatively in some ten mines. The variable ratios of slowing down the subsidence are achieved respectively. Some study results are obtained by theoretical research and by practice. But many key questions are still not solved in theory and in practice, for instance, what mechanism about deformation follows and what statement about stress of the overburden separateded strata is, what mechanism about pressure arch follows and how about the shape of the arch is in the overburden, how about the relation among the mining space and the height and the length of the separated strata is, how about deformation of the grouting material born large pressure in the separated strata space is, etc.. These deficiencies are the major factors to limit the application of the technology .For above reasons, the writer, based on the experience of many years in theoretical research and in practice, has studied the following questions:(1) Study of the stress statement of overburden obtained by physical simulation and numerical simulation provides a credible basis for calculating the flexibility of the separated strata.(2) The concordant relation between the mining space and the height of the separations strata, the length of the separated strata rock layers is obtained, and the relation between the mining space and the quantity of grouting material is also given.(3) The mechanics model of the pressure balance arch in overburden is founded, that is necessary to calculate the sizes of separated strata rock layers.(4) The mechanics principle of the deformation of the separated strata rock layersis analyzed. Based on the small flexibility theory of thin plate, the mechanics model and the computation method used to calculate the flexibility of separated strata rock layers are obtained to calculate the volume of the separated strata space and the quantity of grouting material.(5) The physical mechanics property of the slurry of coal dust is tested, and the actual volume of it in the separated strata space is calculated in condition that it has been compressed.(6) The method of evaluating the effect of grouting in layer separations is obtained.(7) The mechanics model of calculating the maximal value of the subsidence after grouting or not is founded in variable conditions.(8) The studying results are verified by examples.