Innovative decommissioning for offshore foundation systems

Aura Centre for Doctoral Training

PhD scholarships in offshore wind
energy and the environment

Innovative decommissioning for offshore foundation systems

Project Description

Worldwide and in Europe, there is a huge expansion of offshore wind, however to date little thought has been given to “what happens when we no longer need the foundations?”. Hollow steel piles (monopiles) are generally the foundation type of choice for offshore renewable energy in relatively shallow water. Their future cost-effective full removal has clear benefits and is an obvious focal point for research at present. The removal of piles can fall into two classifications i.e. “self-removal”, and removal by axial pull using standard craneage, where in the latter case significant reduction of extraction loads is required to make this a practical proposition. The term “self-removal” refers to the use of the foundation system itself without the need for heavy lifting equipment (over and above that associated with lifting the self-weight of the foundation). Three techniques appear viable under this classification: overpressure, vibration and rotation [1,2]. The first involves pressurising the void at the top of the monopile to produce an upwards traction; this is a technique already used for suction caissons. Vibration and rotation are techniques which use the movements of the pile to reduce the strength of the surrounding soils in which the pile 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 project is to develop computational models of these removal processes, to understand their effectiveness in different soil conditions and to enable prototype and full scale take up to be developed. It will allow cost-effective parametric analysis and virtual prototyping prior to expensive demonstration and risk adverse deployment. The nature of the study through computational techniques also allows not only the extraction method to be optimised but also the geometry of the piles for future designs to aid extraction whilst maintaining in-service requirements. One key objective on the way to the full model will be validation against physical modelling and field data.

For the PhD student, the scientific novelty will comprise: development of new computational techniques of much wider applicability to problems in civil and mechanical engineering; the first parametric study of monopile removal techniques and the derivation of initial guidelines for removal methods for industry.

[1] Davidson, C., Brown, M., Brennan, A., Knappett, J. 2017. Decommissioning of offshore piles using vibration. In Proceedings of the 27th International Ocean and Polar Engineering Conference, ISOPE 2017 (Vol. 2, pp. 666-673).

[2] Topham, E., McMillan, D. 2017. Sustainable decommissioning of an offshore wind farm. Renewable Energy, 102:470-480.

PG-Dip Year and PhD Research

We are seeking a candidate for this PhD scholarship with the Aura Centre for Doctoral Training in Offshore Wind Energy and the Environment; a partnership between the Universities of Durham, Hull, Newcastle and Sheffield. The successful applicant will undertake a PG-Dip training year at the University of Hull before completing their PhD research at Durham University.

Entry requirements

If you have received a First-class Honours degree or a 2:1 Honours degree and a Masters (or the international equivalents) in Engineering, Earth Science, Mathemathics or Physics, with an interest in computational methods, we would like to hear from you.

Academic Supervisors

Prof Charles Augarde, Durham University

Prof Will Coombs, Durham University

Please address any enquiries to auracdt@hull.ac.uk, do not contact the supervisors directly.

Funding

Funding is available for Home students only. The full-time Aura CDT PhD Scholarship includes fees and maintenance (£16,062 per annum, 2022/23 rate) for four years, depending on satisfactory progress. The scholarship is available from September 2022 as a full-time position (part-time study is available). You will join Cohort 4 of the Aura CDT in Hull, in the heart of the UK’s Energy Estuary – the global centre for research, innovation and development for the sector. Initially, you will study for a Postgraduate Diploma in Offshore Wind Energy and the Environment, followed by a 3-year PhD project based at Durham University.

Applications are open until 6 June 2022. Please see our instructions on How to Apply

For an informal discussion, call +44 (0) 1482 463331
or contact auracdt@hull.ac.uk