Influence of vibratory pile driving on offshore wind turbine mechanical behaviour

Details

Supervisors

Rattez, Hadrien

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil des constructions, à finalité spécialisée

Abstract

enAs the offshore wind sector continues to expand, monopile foundations remain one of the most widely used support solutions for fixed-bottom wind turbines. Their design is strongly governed by soil–structure interaction, particularly under lateral loading generated by wind, waves and turbine operation. While impact driving is still the reference installation method for offshore monopiles, vibratory driving is increasingly considered as a promising alternative due to its potential advantages in terms of installation time, underwater noise reduction and operational flexibility. However, the influence of vibratory driving on the mechanical state of the surrounding soil and on the subsequent lateral behaviour of monopile foundations remains less clearly established. Since pile installation can modify the density, stress state and contact conditions around the pile, the installation process should not be considered only as a construction stage, but also as a factor that may affect the later performance of the foundation. This thesis investigates the influence of impact driving and vibratory driving on the post-installation lateral response of model monopiles in sand. The experimental work is carried out at reduced scale under controlled laboratory conditions. Particular attention is given to the preparation of the sand mass, using a pluviation procedure assessed through cone penetration tests in order to improve the repeatability of the initial soil state. The model piles are then installed using either impact or vibratory driving and subsequently subjected to monotonic lateral loading. The study focuses on the comparison of the force–displacement response, initial stiffness, moment–rotation behaviour and pile kinematics after installation. In addition to comparing the two installation methods, the influence of key parameters such as embedment ratio, impact-driving configuration and vibratory-driving frequency is investigated. By combining installation observations with post-installation lateral loading tests, this work aims to provide experimental insight into how different driving procedures may influence the mechanical behaviour of monopile foundations in sand.