Abstract: In order to analyze the mechanical characteristics of structural piles adjacent to surcharge, the formulation for calculating the lateral additional pressure under strip- trapezoidal surcharge is deduced based on the elastic solution of Boussinesq. Then the actual additional load in front of the structural piles due to lateral soil displacement is obtained by improving the theory of partial plastic deformation. Simultaneously, considering the ultimate state that soil horizontally slides around pile, the rational passive load of structural piles is determined based on the combination of the modified theory of partial plastic deformation with the computational model for the ultimate resistance of the piles surrounded by flow. On this basis, considering the yield of soil and the influence of structural loads on pile head, differential equations for free, passive and active regions of structural piles are established by using the tri-parameter Winkler elastic foundation beam model. By combining the pile discrete method with the matrix transfer method, a semi-analytical solution for passive mechanical behaviors of structural piles is obtained. The calculated results of the proposed solution are compared with the observed results and theoretical solutions in a reference, and its reliability is validated.