Horizontal dynamic response of partially embedded single pile in unsaturated soil under combined loads

Abstract

In the previous unsaturated soil-pile dynamic analyses, the pile is usually treated as a completely embedded beam, which is far from the realistic condition in engineering practice. Unlike previous studies, this paper presents a coupled dynamic interaction model between the unsaturated surrounding soil and partially embedded pile under combined loads based on the three-dimensional multiphase viscoelastic continuum and one-dimensional beam theory. By utilizing the variable separation and transfer matrix methods, dynamic impedances of the pile head are derived in detail. Afterwards, the reliability of the developed solutions is verified through the comparison with the existing studies. Finally, a comprehensive parametric study is conducted to discuss the influence laws of various soil and pile shaft properties on the dynamic response of partially embedded single pile in unsaturated soils. Meanwhile, differences between the calculation results derived from Timoshenko beam (TB) and Euler-Bernoulli beam (EB) theory respectively are discussed as well. The main conclusions are drawn as follows: (1) Both the stiffness and damping factors based on EB theory are larger than that calculated by the TB theory particularly, and the two computational curves of horizontal complex impedance tend to be consistent when the slenderness ratio of pile shaft is greater than 30; (2) When the soil saturation degree increases, the stiffness factors of dynamic complex impedance gradually decrease but the damping factors increase; (3) When the embedded ratio and slenderness ratio of pile shaft increases, both the dynamic stiffness and damping factors gradually decrease; (4) Increasing in the Poisson's ratio of soil enhances the dynamic stiffness factors, but is negligible for the dynamic damping factors.