Stability Analysis Of Complex Slope Based On Strength Reduction Method

In most slope stability analysis, method of finite-difference strength reduction is included the followding characteristic:consideration of soil constitutive relations of materials, without the need to assume the sliding surface, suitable for solving large deformation problems etc. However, method of finite-difference strength reduction is defined as numerical simulation method, its calculation results are affected by many factors. Therefor, it is important that main influence factors are summarized and discussed. From the slope failure mechanism,"double reduction coefficient method" is more in line with it than "traditional strength reduction method"."Double reduction coefficient method" would be combined with the finite difference method and applied to the stability evaluation of slope. In addition, based on the method of finite-difference strength reduction, non homogeneous soil slope and multi step slope stability whether had been had a great suitable for the results that study form homogeneous soil slopes. Based on these questions, the main achievements are obtained as follows:（1） The main influence factors of slope stability analysis based on FLAC₃D are summaried and discussed. Mainly in grid division, boundary, tensile strength, yield criterion and criterion of instability. Combined with the example, the accuracy of these factors analysis is compared and by the results that based on Morgenstern-Price method. Examples analysis are shown that:it is inadvisable that blindly pursue the fine degree of the grid, results based on the "1times mesh" mode are meet to the accuracy of the slope safety factor; calculation of boundary in the selection, calculation of boundary to include live slope effective shear strain increment area can be as long as the guarantee that the calculation results; in the instability criterion, a new failure criterion is proposed, it is called the " criterion of inflection point of feature point’s displacement", this criterion has clear physical meaning, and its results are closed with some classical methods and other several kinds of instability criterion for discriminant results, with a certain degree of rationality.（2） Slope instability should be known as a progressive failure process, it is reasonable that be adopted different reduction coefficients. In this article, a slope stability analysis program is developed based on FLAC₃D, this program is combined with "double reduction factor method" and "finite-difference principle". The program can be used to determine the excavated slope at limit equilibrium state of different folding c and ψ reduction coefficient （SRF2,SRF1）, and can be drawn out the k～（SRF1,SRF2,SRF） curve. Among them, k=SRF2/SRF1,SRF=（SRF1+SRF2）/2. Examples analysis results are shown that: curve of the lowest SRF values （i.e.SRFmin）, as the slope safety factor, is reasonable.（3） The application of finite-difference strength reduction in heterogeneous, multi step slope is discussed in this paper, specifically in the two major aspects:"Validation" and "Application about criterion of inflection point of feature point’s displacement". The example analysis are shown that:the finite-difference strength reduction method is fully applicable to the evaluation of heterogeneous, multi step slope, and its advantage is more outstanding; the "criterion of inflection point of feature point’s displacement" is equally applicable to heterogeneous, multi step slope.（4） Finally, rationality and practicability of suggestions in this paper has been proved in combination with a practical example.