Study On Overburden Strata's Movement Pattern And Mechanism Of Mining Steeply Inclined Seams

Surface subsidence is a complex process due to mining strata's movement and deformation. For steeply inclined seams, the obliquity of the coal seams is one of the important factors deciding the displacement and the destroyed form of the overburden strata. In the past researches, many mathematical expressions were applied to describe the final surface subsidence shape. The corresponding profile functions were established to approach the shape. The overburden strata's aeolotropism of steeply inclined seams in the horizontal direction makes the subsidence processing much more complex. In addition, the complex geological condition of steeply inclined seams makes the research on deformation mechanism of overburden strata much insufficient. So it affects the correct prediction, prevention and reclamation for the surface subsidence of the mining area.The paper combined the theoretical analysis, equivalent material simulation experiment, numerical simulation with engineering example, using the obliquity of coal seam as the main factor, being based on the research achievements in the past and the research reality in mining subsidence of steeply inclined seams. Firstly, based on the theory of sheet small deflection, the theory of minimum potential energy and the theory of bifurcation, the paper analyzed the stability and the limit span of the rock sheet within overburden strata's"厂"shape movement arch. Secondly, based on the theory of the composite stratified medium, the computation model of the"厂"shape composite strata movement is established. Thirdly, based on the theory of equivalent material simulation, the experimental model of similitude material is established, and strata's obliquity of the experimental model is 60°. The advanced 3-demensional laser scanner system is firstly applied to collect and analyze the experiment data. Fourthly, based on the powerful function of numerical simulation software ANSYS, the paper researched the combination effect of the overburden strata generating from different rock characters combination in mining steeply inclined seams, the influence of different obliquity and the 3-dimensianal numerical simulation of the surface subsidence. The main research results are as follows:Firstly, based on the terrane movement characteristics and the force transfer mechanism, the paper first advanced the"厂"shape terrane movement model of overburden strata in mining steeply-inclined seams. The upper end of direct roof was easily snipped or snapped in normal direction by the pull and cut force. This deformation gradually extended to the old roof. The un-inbreak overburden strata formed level arch, which supported the up end of the old roof. The falling stones filled the mining area bottom and supported the under end of the old roof. Two terminals of the top plate was respectively supported by the level arch and the falling stones, and the super-stratum bent to mined out space in the approximate normal direction. So overburden strata formed the"厂"shape structure movement arch.Secondly, based on the theory of the sheet small deflection, the theory of minimum potential energy and the theory of the bifurcation, the paper analyzed the stability of"厂"shape movement arch in steeply-inclined seams mining. With the those theories, the paper analyzed that the left arch of the terrane board was the four sides clamped terrane board or simply support terrane board. At the same time, the limit span of the terrane board and the normal height of the arch are calculated. The paper also applied the theory of bifurcation to analyze the stability of the"厂"shape level arch and conditions that made top rock board fall.Thirdly, based on the theory of the composite stratified medium, the paper...