Analytical solution of lateral dynamic response of a large diameter pipe pile considering influence of axial load

The horizontal vibration model for a large diameter pipe pile subjected to axial load in viscoelastic soil is established. The potential functions are adopted to decouple the governing equations of the soil. Analytical solution of the impedance of the pipe pile is obtained based on the assumption of perfect contact between the pile and the soil. This analytical solution can be perfectly simplified to the horizontal vibration solution of pipe pile without axial load, which demonstrates the validity of the solution deduced in this study. Numerical examples are presented to analyze the influences of axial load, excitation frequencies, and pile lengths on the complex impedances, displacements and internal forces. The results show that the complex impedance resonates at the inherent frequency of the pile-soil system. The vertical loads cause the redistribution of the displacements and internal forces of the pipe pile. The maximum displacement, bending moment and shear stress are located at the upper part of the pile shaft when the vertical load is 0, however, they move to the pile bottom gradually with the increase of the vertical load. The horizontal displacement of the pipe pile varies with the frequency. The changes of rotation angle, bending moment and shear force are obvious at the lower part of the pile shaft. The influences of pile length on displacement and internal force at the middle and bottom parts of the pile are more significant than those in the other parts. The displacements located at the upper part of the pile shaft without inner soil are larger than those with inner soil.