Abstract: Besides the strength reduction technique in slope stability analysis using Finite Element Method (FEM), another popular FEM method is to define the factor of safety as the ratio of resisting force to the driving force along a proposed slip surface. It is observed that some unreasonable results might be occurred under this definition. This paper compares the analytic solutions on the specified slip surface of a pure clay slope with the FEM results. The results show that the Poisson's Ratio has a great influence on the factors of safety obtained with FEM approach. The factor of safety obtained from the FEM is in consistent with the analytic solution when the Poisson's Ratio is close to 0.5.

Key words: Slope Stability, Strength Reduction Technique, Limit Equilibrium Method, Factor of Safety