Vertical elastic dynamic impedance of a large diameter and thin-walled cylindrical shell type foundation

This paper studies the vertical vibration of a large diameter and thin-walled cylindrical shell type foundation embedded in a fully saturated porous seabed in contact with a seawater half-space. The solution of the coupled fluid-shell foundation-soil vibration problem is obtained using the ring-load Green's functions for both the shell and the layered fluid-seabed half-space. By considering the fully coupled boundary conditions at the shell-soil interface, the shell vibration problem is reduced to Fredholm integral equations. Through an analysis of the corresponding Cauchy singular equations, the intrinsic singular characteristics of the problem are rendered explicit. With the singularities clear, an effective numerical method involving the Gauss-Chebyshev method is developed to solve the governing Fredholm equations. Selected numerical results for the dynamic contact load distributions, displacements, and dynamic impedance functions are examined based on different shell lengths, soil materials, shell properties, and frequencies of excitation. Moreover, the results are analysed for cases in which there is and is no fluid overlying seabed to examine the effect of fluid.