Dynamic vertical and rocking impedances of a strip foundation in offshore engineering

Abstract

This paper proposes a coupled fluid half-space - strip foundation - poroelastic half-space vibration model to study how dynamic water pressure caused by strip vibration affects foundations operating offshore. Both vertical and rocking vibrations are considered. The governing equations of the problem are obtained using the Biot’s theory and proper boundary conditions at the seawater - seabed interface. The solution of the strip vibration problem is obtained by an integral equation method. The results are expressed in terms of dual integral equations that are converted into Fredholm integral equations and solved numerically. Selected numerical results for the vertical and rocking dynamic impedance functions are examined based on different poroelastic materials and exciting frequencies. The results show that for a rigid strip foundation, the presence of a seawater half-space can increase amplitude of the dynamic vertical impedance, but decrease amplitude of the dynamic rocking impedance.