Research The Roles Of Surface Movement Of Repeatedly Mining Under Thick Unconsolidated Layers

Surface subsidence is a progress of nolinear variations in time and space after the underground resources is exploited, In the study of ground movement and reformation, not only the size and distribution of the value of the final movement and reformation should be considered in, but also the tendency with time should also be considered in. As the result of increasing destroy from the repeat mining, the movement and reformation of surface is intensified. Thus, to obtain the law and the parameters of the movement and reformation, analysis the mechanism of parameters variations, and accomplish the dynamic prediction are the key points of the study.Corresponding to the data of first working face in Wolonghu coal mine, the characters and laws of the movement and reformation were analyzed in the two conditions of first and repeat mining and the parameters were obtained by Matlab. The changes of the angel parameters, including traveling angel, border angel, crack angel, the dynamic parameters, including advanced influence distance, advance influence angel and subsidence rate, the prediction parameter, including subsidence factors q, tangent of the major influence angel tgβ, inflection point offset distance S, mining influence spreading angel θ and horizontal shifts coefficient b, were also analyzed. The major discussion was focused on the dynamic prediction mechanism based on the Knothe time function in the base of probability integral model. Finally, the time influence parameter c was calculated and the maps of surface movement and reformation, the maps of subsidence isogram, and the3D surface diagrams of the moving basin were drawn. The study results for the directive function are significant and useful in the mining design and the protection of surface buildings under the similar geological conditions.