New interaction model for vertical dynamic response of pipe piles considering soil plug effect

A soil–pile interaction model is developed to better represent the actual behavior of pipe piles undergoing dynamic testing. To correctly investigate the dynamic interaction mechanism of the pipe piles, the developed model introduces an additional mass to account for the soil plug. The governing equations of motion for the soil–pile system subjected to small deformations and strains are established considering plane strain conditions for the soil and one-dimensional wave propagation in the pile. The analytical solution of the vertical dynamic response of the pipe pile in the frequency domain is then obtained by employing a Laplace transform and transfer function technique. The corresponding quasi-analytical solution in the time domain for the pipe pile subjected to a vertical semi-sinusoidal exciting force is subsequently derived by means of a Fourier transform. A parameter sensitivity analysis of the additional mass model is carried out to determine the approximate range of the parameter values. Utilizing the developed solution, a parametric study is performed to illustrate the influence of the properties of the soil–pile system on the vertical dynamic response of the pipe pile. Finally, the validity of the additional mass model is validated by conducting a set of model tests, based on which the concept of “apparent wave velocity of pipe pile” (AWVPP) is also proposed.