The three-dimensional stability analysis of the high sand-gravel slope on the right bank of Dashimen hydro-junction project is carried out by means of the finite element strength reduction method based on the deformation stability and control theory. The three-dimensional stability state of slope is quantified by the variation curve of plastic complementary energy with strength reduction coefficient based on minimum plastic complementary energy principle. The safety factor of slope under critical stability state is determined. Through the evolution of the unbalanced force with the strength reduction coefficient, the failure mode and position under the given safety factor of the slope are determined, which could provide scientific basis and guidance for the treatment and reinforcement of the slope engineering. The results show that the high sand-gravel slope of the right bank of Dashimen hydrojunction project is in a stable state, and the global landslide will not occur. The finite element strength reduction method based on the deformation stability and control theory provides a set of practical and effective analysis theory and method for the three-dimensional stability analysis of the slope.

1. Introduction

Stability analysis is indispensable for slope engineering and reinforcement design. It has important guiding significance for determining whether the slope is stable or not, the reinforcement force needed and the reinforcement scheme after the slope is unstable. At present, the three-dimensional stability analysis of slope has not been well solved. The traditional limit equilibrium method is still widely used in engineering because it is relatively simple and has accumulated a lot of experience in practice. However, the biggest problem of limit equilibrium method is that it needs to presuppose the position of sliding surface and determine the shape of slider, and ignores the influence of stress and strain behavior of material.

With the rapid development of computer technology, finite element method has been widely used in slope stability analysis. It can deal with any geometric shape and simulate various material properties. Matsui and San (Matsui and San, 2008) first proposed a strength reduction method based on Mohr-Coulomb (M-C) criterion. The strength reduction method of elastic-plastic finite element has great advantages over the traditional limit equilibrium method. It can automatically search the most dangerous critical failure surface without presupposing the failure mode (Griffiths and Lane, 1999; Zienkiewicz, 1975).

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