Abstract：The failure of landslide/slope belongs to the category of failure mechanics. When the stress and strain of failure surfaces reach the limited state and the shear strengths are fully utilized，the slope failure occurs at the same time，which is the failure criterion of slope failure mechanics. Usually，the soil does not reach the limited state completely when there is interaction between soil and support structure，instead，some soil is in the elastic state and some soil is in plastic limited state. This stress state is not the design state. The design method of limited state is adopted in geotechnical engineering for many years，which utilizes the soil shear strength fully and assume the soil to reach the plastic limited state completely，so that a safe and economic structure is made. This principle should be followed when the internal forces of support structure is calculated by FEM，and the lateral earth pressure computed by FEM should be equal to the earth pressure by traditional limited equilibrium method. Under this condition，the interaction between the soil and support structure is considered. According to this principle，the shear strength reduction FEM is adopted to analyze the interaction between soil and support pile with prestressed cable. The thrust distribution in landslide and internal forces of support pile are obtained with the c-tanj reduction. Through a series of case studies，the applicability of proposed method is clearly exhibited.
