Novel Installation and Extraction methods for Foundations of Offshore Wind Turbines

The widespread deployment of offshore wind turbines in Belgium and Europe requires the use of fast,  low-cost and reliable installation methods. While impact pile driving is predominantly used for offshore foundations, vibratory pile driving provides an interesting alternative, commonly used in onshore applications. Vibratory driving induces increased pore water pressures that liquefy the soil, allowing for pile installation and removal using a relatively small surcharge force. As a result, vibratory driving represents an economic and more sustainable alternative to impact pile driving. However, it is unclear how the use of vibratory driving affects the mechanical properties of the soil during installation in offshore conditions, and consequently the mechanical response of the structure throughout its lifetime. This is important, since the lateral soil stiffness strongly affects the fatigue lifetime of the wind turbine. The objective of the present project is to develop a better understanding of the soil-structure interaction  during the installation and operational use of the foundation. Semi-analytical and numerical models will be developed and calibrated using cyclic triaxial tests in conditions characteristic for offshore environments. The results of the models will be compared to reduced scale experiments of impact and vibratory driving for the installation and the extraction, but also the mechanical behavior of the pile subjected to cyclic loading under wind and wave loading. The developed methodology will be applied to actual case studies, aiming at a characterization of the soil-pile interaction and providing design guidelines