Innovative decommissioning for offshore foundation systems

Project Description:

This Research Project is part of the the EPSRC CDT in Offshore Wind Sustainability and Resilience’s Offshore wind energy geotechnics Cluster.

With the expansion of offshore wind comes the unavoidable question of what happens when we no longer need the foundations? So that we may minimise long term liability, and operate in a sustainable manner, a cradle to grave approach needs to be considered – one that reaches right back to the development of systems that allow for both maximum performance during the lifetime of the turbine, as well as its cost-effective removal at end of life.

At present removal is broadly categorised into three methods: overpressure (pressurising the void at the top of the monopile to produce an upwards traction), vibration and rotation (which both utilise movements of the pile to reduce the strength of surrounding soils into which it is embedded). While some exploratory work has been carried out by contractors to date, none of these techniques have yet to be studied in detail at the scale of a typical offshore monopile.

The aim of this PhD project is to develop computational models of these removal processes, to understand their effectiveness in different soil conditions, and to enable the development of prototype and full scale take-up to be developed. In doing so, a cost-effective parametric analysis will be granted, and virtual prototyping prior to expensive demonstration and risk adverse deployment. The nature of this study though computational techniques will not only allow for extraction methods to be optimised, but also the geometry of piles for future designs to aid extraction whilst maintaining in-service requirements.

The novelty of this project is found in its aims to:
(i) Develop new computational techniques of much wider applicability to problems in civil and mechanical engineering;
(ii) First parametric study of monopile removal techniques;
(iii) Derivation of initial guidelines for removal methods for industry.