The role of fabric anisotropy on cyclic ratcheting of offshore sands under generalised loading conditions

Project Description:

This PhD scholarship is offered by 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 and will continue their PhD research at Durham University.

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The Project

The use of advanced numerical methods to analyse the performance of offshore wind turbines (OWTs) under environmental loads led recently to improved design methodologies [1] that reduce the construction cost significantly. However, the accurate OWT-monopile-soil interaction modelling is still an ongoing research challenge, mainly due to the lack of a well-established theory for the mechanical response of soils under generalised loading conditions. The aim of the project is the development of a novel constitutive framework that includes the complexity of soil’s microstructure (fabric) and its effect on soil’s mechanical response during generalised cyclic loading. The model will be applied in high-fidelity, 3D, hydro-mechanically coupled FE analysis of OWT-monopile-soil interaction, for a more accurate analysis of the long-term performance of OWTs, that can lead to a more cost-effective design practice.

In the state-of-the-art OWT design guidelines the assumed loading paths that are imposed on the soil around OWTs are significantly simplified. Those assumptions affect both the experimental programs that are used to generate data for the soil’s mechanical response, as well as the accuracy of the mathematical models that are used to describe it; they are accurate only for those simplified loading paths. This greatly affects the accuracy of the 3D FE analysis and as an extension the accuracy of the simplified design tools that are calibrated based on the output of the numerical analysis, since generalised loading conditions are encountered during the long lifetime of OWTs.

There is recent experimental evidence that soils exhibit drastically different deformation characteristics when generalised loading conditions are encountered, especially during cyclic ratcheting with high number of cycles [2]. This is attributed to fabric anisotropy, the combined effect of the loading direction and the microstructure characteristics of the granular assembly (particle orientation etc). Currently there is a lack of a constitutive theory that considers fabric anisotropy effectively for generalised loading both in monotonic and cyclic ratcheting conditions [2].

The target of this project is the development of a novel soil constitutive framework that considers the effect of fabric anisotropic in cyclic loading and ratcheting of sands. Moreover, the new framework will be used in hydro-mechanically coupled, 3D, FE analysis with the aim to produce data and evidence for new and more efficient design tools for OWTs.

References:

[1] Pisa design model, Burd et al. (2020), (Link)

[2] 3D-informed laboratory soil testing, Cheng et al (2021), (link)

For more information visit www.auracdt.hull.ac.uk. If you have a direct question about the project, you may email auracdt@hull.ac.uk or the project supervisor.

Training and Skills

You will be trained and develop skills in scientific computing and programming for data analysis and visualisation (e.g. Python). Moreover, you will be trained on algorithmic developments using open source computer languages (e.g. C++) for development and application of FE analysis for engineering problems. Finally, you will develop skills on scientific writing, research presentation and communication.

Entry requirements

This PhD research project is suitable for applicants with a background in Engineering, Earth Science or Physics. If you have received a First-class Honours degree OR a 2:1 Honours degree and a Masters OR a Distinction in a Masters Degree, with any Undergraduate Degree, in one of the above subjects, (or the international equivalents,) we would like to hear from you.

If your first language is not English, or you require Tier 4 student visa to study, you will be required to provide evidence of your English language proficiency level that meets the requirements of the Aura CDT’s academic partners. This course requires academic IELTS 7.0 overall, with no less than 6.0 in each skill.

Funding

The Aura CDT is funded by the EPSRC and NERC, allowing us to provide scholarships that cover fees plus a stipend set at the UKRI nationally agreed rates, circa £17,668 per annum at 2022/23 rates (subject to progress).

Eligibility

Research Council funding for postgraduate research has residence requirements. Our Aura CDT scholarships are available to Home (UK) Students. To be considered a Home student, and therefore eligible for a full award, a student must have no restrictions on how long they can stay in the UK and have been ordinarily resident in the UK for at least 3 years prior to the start of the scholarship (with some further constraint regarding residence for education). For full eligibility information, please refer to the EPSRC website. Please note, we have already allocated all our places for International Students to this cohort, so please do not apply unless you are a Home student.

How to apply

Recruitment is open until 16 April 2023 for Aura CDT PhD Scholarships beginning study in September 2023.

Applications are made via the University of Hull admissions system.

If you have not applied with the University of Hull before, you will need to set up an account to enable you to track the progress of your application and upload supporting documents.

With your application, you need to upload copies of the following supporting evidence:

• complete transcripts (and final degree certificate(s) where possible). If your qualification documents are not in English, you will need to supply copies of your original language documents as well as their official translation into English.
• A completed Supplementary Application Form (please upload when asked to add Personal Statement).

Guidance on completing your Supplementary Application Form: The Aura Centre for Doctoral Training is committed to generating a diverse and inclusive training programme. As part of our inclusive practices, the Centre adopts a process of assessing applications purely based on skills and attributes and does not consider any personal details. As such we ask applicants to remove any personal details from the Supplementary Form which is used by the Panel to assess and select applicants for interview. The form asks for details of your education, training and employment history as well as some specific questions about your motivations and research experience and interests. It is very important that you do not include any personally identifying information.

Applicants must:

Remove all personal references in their application. Specifically, do not include the following details: Names, age, country, sex, gender, religion, disability, race, sexual orientation

Complete all sections of the form in font and size Calibri 11pt

Indicate your interest in applying to a maximum of two Research Projects (you may apply for one or two, but no more than two)

Once fully completed, you should upload the form when asked for your Personal Statement, as part of your application through the University of Hull student application portal using the links below. (You will also be asked for your degree transcripts during the application process). Please do not send your form directly to the Aura CDT.

Application links:

Apply for a full-time PhD Scholarship with the Aura CDT.

Apply for a part-time PhD Scholarship with the Aura CDT.