Study Of The Deformation Behavior Of Overburden Rocks In Abandoned Stope

The mining deep and the scale of abandoned stope is continuously augmenting as the demand for mineral resources increase more and more for satisfying the need of human development, which lead to the deformation of overburden and subsidence of earth surface are more and more serious. It put sorely impact on the peoples' life and production action, at the same time it cause heavy economic losses. Wherefore, it is of practicability that study the rule and mechanism of overburden deformation and earth surface subsidence caused by underground mining.The characteristics of overburden deformation and surface subsidence is non-uniform, discontinuity and large displacement, so this is a exceeding complicated non-linear problem. Our predecessors have adopted some methods, for example, monitoring in-situ, theory analysis, laboratory test and computer simulation etc, to forecast the of overburden deformation and subsidence of earth surface, to study the distributing of cranny and layer separation and to discuss the defend and control scheme of overburden deformation, many instructive experience and conclusions have been got.The paper carried through a series of study about overburden transmutation based on the project" Study of Abandoned Stope Disposal of Dayukou Ore of Mujiashan of Jingxiang Chemical Engineering Company of HuBei ". The main content and conclusion of this paper are following:l)Comprehensive and systemic investigation and analyses on disasters caused by overburden deformation and earth surface subsidence were carried out. Recent main analyses methods and study development are summarized, especially, the development situation of similarity simulation and its merits and shortcomings were reviewed, which provide a foundation for this thesis. So, the scheme that adopt FEM numerical simulation and similarity simulation to study deformation behavior of abandoned stope overburden was confirmed.2)Laboratory uniaxial compression tests, split tests and confined shear tests wereconducted to obtain the rock mechanical parameter. Combine the practice experience and acquired production, the rock -mass mechanical parameters necessary for numerical simulation and similarity simulation were established.3)The deformation and breakage rule of overburden and earth surface, the limitspan of roof are analysed by FEM ANSYS software, an attempt is made to simulate the layer separation in overburden in FEM numerical modeling. It has been found from this research that the range of surface movement increases moderately with the collapse of jambs and the increase of the roof span. The subsidence area ranges from 1.5 times to 1.7 times of the roof span and the subsidence curves are symmetrical to the vertical line through the point with maximum subsidence. The horizontal movement, however, is not symmetrical and its impacting area is larger than the range of subsidence, with its maximum value equal to 40% of the maximum subsidence. In addition, the layer Separation exist in the end of span of overburden if the subsidence happen in whole overburden , which is resulted from the shear failure of the bedding plane.4)Orthogonal experiments was adopted to determine material proportion of similarity simulation, the stratification widely in stratum was modeled by mica powder. The whole process from deformation to crack and collapse of overburden failure was modeled and the emerge course and the existence domain of layer separation is described, at the same time, the regularity of earth surface subsidence is analysed, it is concluded that relatively reliable span limit of overburden is 110m, Furthermore, the measure error and the material parameter error was discussed in paper.5 ) It is found that not only the earth surface subsidence but also the inneroverburden deformation, the conclusion of numerical simulation and similarity simulation are basically uniform, the pattern and mechanism of overburden deformation were studied. In addition, a feasible control scheme of overburden deformation was brought forward for analogous project based on the actual situation and primary control scheme have been employed.