Torsional vibration of a tapered pipe pile considering the circumferential support exerted by the external and internal soils

In this paper, the torsional vibration of a tapered pipe pile is examined considering the circumferential support exerted by both the external and internal soils. The pile-soil system is vertically segmented, with each pile segment assumed to possess a uniform cross-section. The circumferential soil support is modeled using the Voigt model. In light of new equilibrium conditions at the contact surface of consecutive pile segments following the introduction of circumferential support, an amended impedance function recursive method is established. It is then used to build an improved analytical solution to characterize the torsional vibration of the tapered pipe pile. Finally, the coupling effect of the circumferential support and pile-soil parameters on pile torsional vibration is evaluated. The results demonstrated that: (1) The circumferential soil support enhances pile dynamic stiffness and damping, consequently reducing its amplitude-frequency response; (2) The circumferential support has a more significant impact on pile torsional vibration when it originates from the external soil compared to the internal soil; (3) The influence of the circumferential soil support intensifies as the taper angle, length, internal radius, wall thickness and shear modulus of the pile increase, or as the shear moduli of the external and internal soils increase.