Numerical Modeling of the Monotonic Lateral Behavior of XL and XXL Monopiles in Kaolin

Abstract

Monopiles are the favored foundation type for offshore wind turbines due to a relatively simple design and installation process. This paper investigates using coupled three-dimensional finite-element analysis the load-deformation behavior of extra-large (XL) and extra-extra-large (XXL) monopiles in low-shear strength overconsolidated kaolin clay subjected to monotonic lateral loading at varying load eccentricities. The subloading tij constitutive model, robustly calibrated using data from centrifuge tests carried out by the authors, has been adopted in these analyses. For the 16 cases analyzed, a detailed discussion is provided on the behavior of XL/XXL monopiles, including their mode of deformation, lateral capacity, deflection, rotational stiffness, bending moment and shear force, and the response of the clay in terms of soil resistance and excess pore pressure. It is also demonstrated that the p-y method is inaccurate in designing monopiles in this size range.