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The reliability theory based analysis is more advanced and reasonable compared with the traditional methods for slope stability analysis. Limit equilibrium method is usually used to evaluate the stability of a slope. In this paper, a new reliability analysis method is obtained based on JC method and multi sliding surface method which a new limit equilibrium method developed by Huang. Then, this new method is applied for a wharf slope. The sliding surface get from the safety factor is not the same as that from reliability index though they are close to each other. The safety factor or reliability index get from Fellenius method is smaller than that from other method. The safety factor or reliability index get from multi sliding surface method is close to that from Bishops method. The reliability index can be more reasonable after the standard deviation of the soil property index is deduced with random field theory.

Uniform safety factors are normally assumed in slope stability analysis and this assumption can influence the rationality of the analysis. New analysis methods were obtained based on Fellenius, Bishop and multi sliding surface method to study a failed slope of a port in southern China. The calculation results show that the safety factors of soft soil layers will be overestimated and the safety factors of hard soil layers will be underestimated if soil mass of slope vary widely in the strength. For the failed slope in this paper, the factors obtained with normal methods will be overestimated because of the hard soil layer of this slope.

On the basis of the limit equilibrium method and the physical significance of Coulomb’s yield criteria, extremum conditions of yield functions is established, which will be the fundamental equations for the limit analysis of soil mass. Once the stress equation along a sliding surface is available, the normal stress on the sliding surface can be obtained, a new limit analysis method, generalized limit equilibrium method (GLEM), can be established. With the generalized limit equilibrium method, an analysis method to solve the problem of slope stability can be obtained without introducing any other assumptions or simplified conditions but the sliding surface. With this algorithm, any discretionally possible sliding surface can be trial calculated and the least value of the calculated results of different sliding surfaces is taken as the safety factor. As long as a selected sliding surface is close to the true sliding surface, the derived safety factor will be approximate to the genuine solution to a problem of slope stability.