Influence Of Mining Subsidence On The Stability Of Ground Surface

The influence of the mining subsidence on the stability of the ground surface is a task of great significance and research value. This thesis studies the task by the numerical analysis employing the analyzing software ANSYS, and it mainly involves the following aspects: 1.After referring to a large amount of literature materials, it summarizes the history and the present state of the research on the theory of the mining subsidence, expounds in detail about two main types of research methods: Statistic method , Mechanical study method, and also points out the disadvantages of them. It gives a detail introduction about the numerical method analyzing the mining sinking based on the mechanical study method. 2.A brief summary of the basic rules causing the sinking, which includes an introduction of the district, the form of motion and the process of the damage of superimposed rock, and an introduction of the range of surface sinking, the forms of surface moving damage and the basic surface distortion parameters. 3.The thesis also sums up the constitutive relationship of the elasticity and plasticity of the soil and briefly accounts for the Drucker-Prager Model and the choice of the model parameters. It particularly introduces that how to realize the numerical analysis of the soil non-linear mechanics by ANSYS. Through a concrete project it explains how to use the ANSYS to have the numerical analysis on the stability of the ground surface of the mining subsidence, and the calculating result is applied to the project. 4.The conclusion after having the numerical analysis of the influencing factors of the mining sinking: (1)The influence of the mining depth: with the increase of the mining depth, the surface sinking decreases; the maximal level distortion decreases; the range of the sinking basin expands and becomes more and more even. (2)The influence of the mining thickness: with the increase of the thickness, the vertical sinking of the surface increases by degrees; the maximal level distortion also increases by degrees; the range of the sinking basin doesn't have an obvious change and the sinking difference on the verge of the basin increases by degrees. (3)The influence of the mining width: with the increase of the width, the vertical displacement of the ground surface increases by degrees and the rate is quicker; the maximal level distortion also rapidly increases; the range of the sinking basin continually expands. (4)The influence of the quality of the superimposed rocks: with the increase of the rigidity of the rock formation, both the maximal level and vertical displacement of the ground surface obviously decrease; in composite rock formations, the sinking and the level displacement of the rock which is soft in the upper part and rigid in the lower part is smaller than the opposite type. (5)The influence of the rock formations: with the increase of the gradient of the hill, the sinking basin will not lie exactly over the mining subsidence, but gradually moves towards the direction of the lower . (6)The influence of setting coal columns: the setting of reasonable coal columns plays an evident role in the control of the sinking of the buildings. The larger the size of the columns, the better. When setting the safe coal columns, the curvature of the ground surface is positive, the smaller the size of the columns and the bigger the curvature, which can cause the buildings to distort, the more disadvantageous to the buildings. But if the size of the columns is not large enough, which will cause more damage than not setting the coal columns; with the size of the secure columns continuing to enlarge, the curvature also decreases. (7)he influence of the filling of the mining subsidence: the filling of the coal layers after being mined in time will have an obvious effect on diminishing the surface sinking and the level distortion. After the mining subsidence is filled in, the range of the sinking basin doesn't change evidently, and the shape of the basin becomes more smooth. 5. On the basis of the above research about the influencing factors, this thesis gives some preliminary improving measures: 1.adopting the method of filling mining subsidence; 2. eliminating the influence of the verge of the mine ; 3.excavation in harmony.