Abstract：Two-dimensional Janbu’s generalized procedure of slices is one of the rigorous methods for slope stability analysis. However，twice iterations must be carried out and the convergency problem may often be encountered in the computational process. Hence，a simplified Janbu’s method is developed in which the interslice shear forces are assumed to be zero and only once iteration is needed. Generally，the result obtained by simplified Janbu’s method is very close to that given by complete Janbu’s method，therefore the former is adopted in a number of commercial programs. It is natural to extend the 2D method to conduct 3D slope stability analysis. Compared with two-dimensional slope stability analysis，it is more difficult to conduct three-dimensional analysis，for the geometric shape of the sliding body may be asymmetric and the slope may also possess complicated slip surface，irregular boundaries，and multiple geological layers. The method proposed in this paper extends the simplified Janbu’s method for three-dimensional slope stability analysis. By setting the safety factors to be equal for discretized blocks on the same row/column and combining the geometric feature of the bottom slip surface，the local safety factor and potential sliding direction for each block can be obtained. This method extends traditional limit-equilibrium method in which only the total safety factor for a slope is given，thus it may be used to evaluate local stability and sliding direction for a slope. This proposed method may be applied to various types of potential slip surfaces，complicated geological boundaries and stratifications，water pressure，and earthquake loading.
