Three-dimensional Limit Equilibrium Analyses Of The Stability Of Saturated-unsaturated Soil Slopes

At present, limit equilibrium method is one of the major methods of three-dimensional slope stability analysis. In order to make the stability analysis more fitful in the practice of slope engineering, this paper studied the problem of the slope stability in complicated conditions thoroughly with structured programming as follows:Firstly, two of limit equilibrium methods for analysing three-dimensional slope stability were improved with a focus on the analyses of three-dimensional slope stability in complicated conditions according to engineering practice. The validity, serviceability and reliability of methods and programs were demonstrated by some examples.Secondly, the general rules of the factor of safety of simple slopes were studied by using the shear strength theory for saturated soils while considering the variations in soil parameters such as physical, mechanical index and the shape of the slopes. Then, the influences of factors including the soil layer distribution, the locations of vertical loads, the ground water level as well as the earthquake intensity on the factor of safety of complicated slopes were analyzed with the program. The three-dimensional slope stability was analyzed with conditions of anisotropy and nonlinearity of the shear strength, after which reasonable shapes of revetment for slopes were also precisely discussed.Thirdly, a particle swarm optimization (PSO) method was applied to three-dimensional slope stability analysis. Namely, a particle swarm optimization method is developed for searching for the critical slip surface corresponding to the minimum factor of safety.Finally, with the application of shear strength theory for unsaturated soils, this paper focuses on the limit equilibrium analysis of the stability of saturated-unsaturated slopes. The influences of shear strength parameters, metric suction and its distribution and changes in underground water level on the factor of safety of saturated-unsaturated soil slopes were analyzed. The factors of safety of saturated-unsaturated slopes, as a key result of the analysis of the slope stability with consideration of the effect of metric suction, were found considerably larger than that without consideration of metric suction or from traditional strength theories.The results of this study are of great theoretical significance in understanding the general rules of slope stability in complicated conditions and in the design and analysis of slope stability.