| Weak layer is an important factor leading to landslide in surface coal mine,how to evaluate the non-homogeneous slope stability with weak layer is a technical problem to be solved in surface coal mine.The traditional limit equilibrium method is based on the static equilibrium equation and moment equilibrium equation to solve the stability factor.It is complicated for the calculation process because of the established equation belongs to the statically indeterminate problem and it needs to introduce a large number of assumptions.Compared to the limit equilibrium method,the limit analysis method seeks for the deformation and failure mechanism of slope rock and soil by constructing the static permissible stress field and the kinematically admissible velocity field.And the theoretical basis is rigorous and the derivation process is rigorous.Especially for the problem of three-dimensional homogeneous slope stability,no need to establish a large number of equilibrium equations and the calculation process of this method is simple and results is accurate.At the present stage,it has gave a good solution to analysis the stability of the homogeneous slope,but there are relatively few studies on the non-homogeneous slope with weak layer,so it is difficult to apply it into engineering practice.In order to solve the problem of evaluating the stability of the non-homogeneous slope with weak layer in surface coal mine,the failure mechanism were constructed of the two-dimensional and three-dimensional non-homogeneous slope with weak layer wich meets the speed separation requirements based on the principle of plastic mechanics;The calculation method of external force power and internal energy dissipation rate of non-homogeneous slope with weak layer in rectangular coordinate system were proposed with the method of coordinate transformation and least-square fitting;The method of finding the most dangerous slip surface and caculating the slope stability factor was proposed based on the upper limit analysis theorem and strength reduction principle,it converts the problem of slope stability analysis into a multi-constrained nonlinear optimization problem,and a calculation program was writed,which broadens the scope of application of the upper limit analysis method;The quantitative relationship between the length-to-height ratio of the sliding body and the three-dimensional stability of the non-homogeneous and long slope with weak layer was revealed by inserting the tensile block at the location of the axial surface.The research results were applied to the engineering practice of the southern slope of the Shenglidong’er surface coal mine,and the reliability of the calculation method was verified.The results show that the failure mechanism of the non-homogeneous slope with weak layer is composed of a combination logarithmic helix and weak layer line in the two-dimensional state.Under the three-dimensional condition,the failure mechanism is formed by curved cone and weak layer.The error rates of the slope stability calculation is less than 10%between the method of the two-dimensional upper limit analysis and the classical residual thrust method,and the error rate between the three-dimensional upper limit analysis method and numerical simulation with JSlope3D is also less than 10%;The three-dimensional slope stability decreases with the increase of the length of the inserted block,until the length of the inserted block reaches 500m,the slope stability does not change significantly with the increase of the insertion block length.At this time,the three-dimensional slope stability is approximately equal to the two-dimensional slope stability.The results show that the length-to-height ratio of southern slope is greater than 4.3 in Shenglidong’er surface coal mine,the spatial effect of the slope can be neglected,and the slope stability can be evaluated by the two-dimensional analysis method.There are 33 figures,13 tables and 184 references in this paper. |
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