Abstract: Based on the upper-bound limit analysis of plasticity,a new combined 3-dimensional failure mechanism of bucket foundation in undrained soft clay against vertical load was established,and the limit analysis model of bucket foundation subjected to vertical load was proposed.It was verified by a comparative study with finite element solutions by use of finite element analysis software ABAQUS.For bucket foundation,a number of parametric computations were conducted.The numerical results computed by the proposed method would be helpful in engineering practices.