A Poroelastic Solution for Dynamics of Laterally Loaded Offshore Monopiles

Abstract

In this study, a rigorous poroelastodynamic solution is proposed for monopiles which accounts for 3D (three dimensional) dynamic interaction of the soil and pile. The dynamic Biot's theory is used to model the soil, while Timoshenko beam is used to model the monopile. The perfect contact conditions between the soil and monopile are realized by decomposing the pile's horizontal translation to radial, hoop and vertical displacements. Correspondingly, 3D radial, hoop and vertical stresses on the pile surface are used to formulate the governing equations of the interaction problem. Using the integral equation methods, the governing differential equations are reduced to coupled integral equations, which are solved numerically. Selected numerical results for coupled lateral and rocking dynamic impedances together with the 3D dynamic contact stresses at the soil-pile interface are studied for different pile and poroelastic material parameters and frequencies of excitation. The distributed soil reaction force and moment along the pile are also obtained by integrating the 3D radial, hoop and vertical stresses along the circumference of the pile at the soil-pile interface. Finally, bending moment, shear force, horizontal translation and rocking rotation of the monopile are obtained based on the classical dynamic Timoshenko beam theory.