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Research Studentship in Geotechnical Engineering (1)

Research Studentship in Geotechnical Engineering

Project: Numerical Modelling of Offshore Wind Turbine Foundations in Sand Accounting for Partial Drainage

4-year DPhil (PhD) studentship starting October 2021

Supervisors: Prof Orestis Adamidis, Prof Chris Martin

Offshore wind turbines (OWTs) are structures subjected to complex cyclic loading patterns from wind, sea waves and currents, and the operation of the turbine. Currently, monopiles are the most common foundations for OWTs (about 80% of OWTs in Europe), and there is a major drive to optimise their design as they reach greater depths and support larger OWTs, while satisfying criteria that ensure their safety and functionality. Regarding functionality, design codes typically require permanent rotation at the end of lifetime to be limited below a prescribed threshold. However, there is no consensus on an appropriate method to estimate this rotation yet. Any method would have to take into account the loading experienced by an OWT, as well as the complex soil response around the monopile, since it is the accumulation of strains in the soil that leads to rotation of the OWT.

Following offshore oil and gas standards, sandy soils around monopiles have typically been considered to behave in a drained way, assuming that cyclic loading is slow enough for any pressure generated in the water-filled pores between sand grains to dissipate. However, this assumption does not hold as we transition to larger diameters of monopiles, especially during a storm event, or when we consider sites with increased fines content, and thus reduced permeability, such as those found in the North Sea. Instead, partial drainage occurs during the timescale of a typical storm loading event.

The aim of this project is to examine the response of a monopile foundation under realistic drainage conditions, taking into account the complex interplay between dynamic loading and pore water pressure accumulation and dissipation. The problem will be studied using advanced 3D finite element simulations. Coupled hydromechanical, effective stress analyses will be performed, using various soil constitutive models that will be tested for their behaviour under partially drained conditions. Results will provide valuable insights on the implications of realistically modelling drainage for dynamic soil behaviour and thus for OWT performance. In particular, the validity of current assumptions will be investigated, new recommendations will be made, and the potential for further optimisation in design will be examined.

Candidates with a demonstrable aptitude for advanced finite element analysis and/or numerical modelling of geotechnical problems are sought. The successful applicant will be a member of the EPSRC Centre for Doctoral Training in Wind and Marine Energy Systems and Structures (WAMESS CDT), which is a collaboration between the Universities of Strathclyde, Oxford and Edinburgh. Further details of the WAMESS CDT programme can be found on the course page on the University’s graduate admissions website. The CDT is committed to equality, diversity and inclusion, and is keen to attract applicants from a wide variety of backgrounds.

Eligibility

This studentship is funded by the WAMESS CDT and is open to both UK and International students, although fees will only be covered at the Home/ROI rate. Further details can be found here under the “Fee Status” tab and here under the “Funding and Costs” tab.

Award Value

Course fees will be covered at the level set for Home/ROI students (currently £8290 p.a.) and a stipend (tax-free maintenance grant) will be paid at the enhanced rate applicable to WAMESS CDT students (currently £18508 p.a.).

Candidate Requirements

Prospective candidates will be judged according to how well they meet the following criteria:

  • A first class, or strong upper second class, honours degree in general engineering, civil engineering, mechanical engineering, or other relevant discipline such as physics or applied mathematics
  • Excellent mathematical and computational skills
  • Ability to undertake scientific programming (e.g. in Matlab, Python, Fortran or C/C++)
  • Strong understanding of fundamental soil mechanics, and some knowledge of design methods for offshore foundations
  • Enthusiasm to undertake the research required for a doctorate
  • Excellent written and spoken English communication skills
  • Excellent record of academic and/or professional achievement

Application Procedure

Informal enquiries are encouraged and should be addressed to Professor Orestis Adamidis (orestis.adamidis@eng.ox.ac.uk) and Professor Chris Martin (chris.martin@eng.ox.ac.uk).

Formal applications are to be made using the online Graduate Application Form that is accessible through the WAMESS CDT course page (click the “Apply” button on the “How to Apply” tab). When filling out the fields of the Graduate Application Form, please observe the following guidance.

On the “Course” tab:

  • Proposed field and title of research project: Numerical modelling of offshore wind turbine foundations in sand accounting for partial drainage

On the “Funding” tab:

  • Are you applying for an advertised studentship competition(s): Yes
  • Advertised reference code: 21ENGWAMESS_OA

Application deadline: 2 July 2021

Start date: 27 September 2021