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The vertical vibration of a viscoelastic pile immersed in arbitrarily layered soil is investigated by taking the interaction among pile, pile surrounding soil (PSS) and pile end soil (PES) into account. Firstly, considering both the stratification and stress wave effect of soil, a mathematical model of the pile–soil system is established based on the fictitious soil pile (FSP) model. Then, utilizing the impedance function transfer method and Laplace transform technique, the analytical solutions of the vertical dynamic impedance of pile are derived in the frequency domain. The analytical solutions are validated by comparing them with other existing solutions. Finally, a parametric study is put forward to investigate the properties of PES on the vertical dynamic impedance of pile. The results reveal that the properties of PES have a significant effect on the vertical dynamic impedance of pile, but there is a critical influence thickness for this effect. For the cases of the PES thickness exceeding the critical influence thickness, further increase of PES thickness will not affect the dynamic behavior of the pile–soil system. [ABSTRACT FROM AUTHOR]

A new soil-pile interaction model, called 'additional soil model', is developed to investigate the influence of soil mass on the dynamic characteristics of pipe piles. The soil is divided into an inner region in the immediate vicinity of the pile and an outer region at greater distance. The soil in the inner region is assumed to be an additional mass to participate with the vibration of the pile. The viscous damping at the soil-pile interface and the radiation damping in the soil are calculated separately. An analytical solution for the vertical dynamic characteristics of pipe piles is derived based on the developed soil model. The rationality and accuracy of the additional soil model have been validated through comparison of theoretical predictions and measured driving stress waves of two full-scale steel pipe piles. The approach makes a useful improvement of soil-pile interaction modeling for dynamic applications. The main conclusions of this study include: 1) both the soil plug and the pile surrounding soil can lead to a decrease of apparent wave velocity of pipe piles; 2) the pile impedance will be underestimated if calculated without the consideration of soil mass; 3) the resonant amplitude and natural frequency of piles will be significantly overestimated if the soil mass is ignored. [ABSTRACT FROM AUTHOR]