For evaluation of the Zishui Bridge of Xiang-Qian Railway Line

a method which uses the finite element method to calculate and analyse compressive stress of the foundation base and displacement of the pier top in influences of different scouring degrees

is presented. The method adopts an approach of changing support pattern of the foundation base to simulate the undercutting of foundation base. This method not only reveals the ultimate undercutting area when maximum compressive stress is equal to allowable compressive stress of the foundation base

but also offers the undercutting area of the foundation base for invalidation of the basement which results from the intense variation for different deformation and stress considering the factor of maximum transverse longitudinal and vertical displacement. A powerful reference is presented for the stability analysis of the scoured pier.