Torsional complex impedance of pipe pile considering pile installation and soil plug effect

Torsional vibrations of pipe pile are more complicated compared to solid pile. In actual engineering, pile surrounding soil may be strengthened or weakened due to different pile installation methods, which is regarded as pile installation effect. At the same time, soil plug effect which describes the interaction between the soil plug and pile wall is also non-negligible in bearing analysis. Along the model of inhomogeneous medium, this paper subdivides the inhomogeneous soil region into certain sub-zones whose shear complex stiffness are derived by virtue of continuity conditions and plain strain model. To study the influence of soil plug effect, the additional mass model is raised and utilized in this paper. In this model, the pile-soil plug system is vertically split into infinite sections, and each pipe pile section and soil plug section is connected by distributed Voigt model. The analytical solution of torsional complex impedance is acquired and compared with results obtained from former studies to verify its rationality. Finally, a parametric research is presented to exhibit the influence of the pile installation and soil plug effect on the torsional complex impedance of pipe pile head. •The present solutions can take both the pile installation effect and soil plug effect into consideration.•The torsional complex stiffness transfer model is proposed to model the inhomogeneity of soil in the radial direction.•The additional mass model is introduced and improved to model the soil plug effect.