Small-scale experimental study on hydraulic extraction of offshore monopiles

Details

Supervisors

Rattez, Hadrien

Faculty

Ecole polytechnique de Louvain

Degree label

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

Abstract

Offshore wind farms are entering a phase of innovation where decommissioning is becoming as relevant as installation. In the sandy soils of the North Sea, at water depths of up to 40 m, monopile foundations represent the dominant solution for supporting turbine structures. However, their removal at end-of-life remains technically and economically challenging due to their large embedment depths. Current industrial practice typically relies on partial extraction, leaving large volumes of high-quality steel in the seabed, affecting future site reuse and raising concerns about long-term environmental impacts. This master thesis investigates an emerging full-removal technology based on hydraulic overpressure applied inside the monopile. The method consists in pressurizing a sealed pile filled with water in order to generate an upward force capable of overcoming soil resistance. Despite its conceptual simplicity, the underlying mechanisms governing pile–soil interaction under internal pressurization remain insufficiently understood. To bridge this gap, the first small-scale experimental framework for hydraulic monopile extraction was developed at the LEMSC laboratory of UCLouvain. A series of 1g model tests at 1:100 scale were performed on a monopile embedded in sand under controlled hydraulic overpressure loading scenarios. The results provide a deeper understanding into failure mechanisms governing pile uplift under pressurized conditions. Beyond the experimental findings, this work establishes the first operational experimental setup for hydraulic monopile extraction at the LEMSC laboratory and demonstrates the feasibility of hydraulic extraction at reduced scale.