Finite element method with reduced shear strength (SSRFEM) was used to evaluated the base stability of excavations in soft clays under the undrained condition. The influence of clay undrained shear strength

conditions of pit bracing system and pit dimensions on base upheave stability of excavations were studied detailedly. The results from several limit equilibrium analysis methods for evaluating base stability of excavations were compared with the results from FEM. It shows SSRFEM is a reliable and robust method for assessing the safety factor of the base stability of excavations and limit equilibrium analysis methods only can be used on some conditions.