Dynamic Stability Analysis of Pile Foundation under Wave Load

Abstract

The main load on a pile foundation in the ocean is the wave load. Presently, few reports exist on the dynamic stability of pile foundations in the ocean. This paper investigated the dynamic stability of pile foundations under wave loads. The foundation reaction force was calculated using a double-parameter model and considering pile side soil softening under a cyclic load. By establishing the energy equation of the entire pile, the Hamiltonian principle was used to obtain the dynamic differential equations of the pile in four different situations (vertical harmonic, transverse harmonic, longitudinal and transverse harmonic, and longitudinal and horizontal harmonic loads with different frequencies). Then, the nonhomogeneous Mathieu equation was obtained by arranging the dynamic differential equations, and the parametric resonance critical frequency and instability load were obtained by solving this equation. The analytical solution was verified by comparing the results obtained by the finite-element software simulation with the analytical solution and analyzing the influence of several different factors on the critical frequency and amplitude. The research indicated that the amplitude of the pile body increases linearly with an increase of wave height, the effect of wavelength on amplitude increases nonlinearly, and the amplitude increases much rapidly with an increase of wavelength. The critical frequency calculated by the double-parameter method was lower than that calculated by the Winkler model, and the result of double-parameter model was more practical and safe.