Research Studentship - Geotechnical Engineering

3.5-year D.Phil. studentship

Project: An element level investigation of the partially drained response of sand around offshore wind turbine foundations

Supervisor: Prof Orestis Adamidis

The rapid upscaling of offshore wind turbines requires significantly larger monopile foundations embedded in sandy soils. Emerging evidence indicates that these large-diameter foundations operate under partially drained conditions during cyclic wave loading, a regime that lies between the classical drained and undrained assumptions used in current design practice. Understanding and modelling soil behaviour in this partial drainage regime is now a critical challenge in offshore geotechnical engineering. Particularly important is the small-strain accumulation under cyclic loading, which governs monopile rotation and is tightly limited by design standards. This studentship forms the experimental core of a wider project which aims to improve modelling for offshore soils irrespective of drainage conditions. The successful candidate will develop and execute an advanced experimental programme to characterise the cyclic behaviour of offshore-representative sands under a range of drainage conditions.

Research objectives

The studentship will address the following objectives: 

1. Development of High-Resolution Strain Monitoring for Triaxial Testing 

Accurate measurement of small strains (<0.1%) is essential for offshore foundation design but remains technically challenging due to compliance and bedding artefacts in conventional instrumentation. The successful candidate will develop and implement fibre optic strain sensing on the membrane of triaxial specimens, which will deliver a strain field across the circumference of the specimen. This effort will include optimisation of the fibre attachment and configuration to minimise measurement interference. Benchmark tests will be run against local LVDT instrumentation. Finally, a reliable protocol for small-strain cyclic soil testing. This work will represent a significant methodological advancement for laboratory geomechanics and will be supported by an industry partner that is a specialist on fibre optic sensing.

2. Experimental Database on Cyclic Soil Behaviour Under Variable Drainage 

The main objective of the studentship is to develop a comprehensive experimental database that characterises the behaviour of sandy soils across a range of drainage conditions and stress paths of relevance for soils around offshore foundations. Standard laboratory testing enforces either constant pore pressure (drained) or constant pore volume (undrained) conditions. However, soils around offshore foundations experience partially drained behaviour, where pore pressure evolves during loading cycles. The successful candidate will design and implement controlled “delayed drainage” triaxial tests using bespoke permeability filters. Following this, the candidate will perform monotonic and cyclic loading tests across a range of confining pressures, cyclic amplitudes, initial stress ratios, and drainage intensities. The fibre-optic strain monitoring protocol developed for the first objective will be used for these experiments, which will form the bulk of the planned testing. A series of complementary tests with controlled volumetric strains during cycling will also be carried out. A subset of experiments will be repeated for sandy soils with a two different contents of non-plastic fines. The final dataset will be made publicly available following the completion of the doctorate and serve as a reference benchmark for advanced constitutive model development and testing, for the wider research community.

3. Updated constitutive model calibration protocols

Using the compiled experimental data, selected advanced constitutive models developed for cyclic loading of sands will be assessed, including bounding surface plasticity and hyperplasticity models. It is expected that updated calibration protocols will need to be proposed to improve performance. Given that advanced partially drained triaxial testing is difficult to specify for industry projects, a simple shear testing campaign will be performed, based on which a minimum set of simple shear tests that are required for reliable advanced model calibration will be proposed.

The research will be conducted in a newly updated, temperature-controlled geotechnical laboratory at the University of Oxford, with the final suite of simple-shear experiments taking place at the laboratory facility of an industrial partner in Southampton.

Eligibility 

This studentship is funded through the Department of Engineering Science and is open to Home students (full award – home fees plus stipend).

Award Value

Course fees are covered at the level set for Home students. The stipend (tax-free maintenance grant) is the UKRI minimum stipend for the first year, and at least this amount for a further two and a half years.

Candidate Requirements

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

• A first class or strong upper second-class undergraduate degree with honours (or equivalent) in Engineering, Applied Mathematics or Physics
• Excellent English written and spoken communication skills 

The following skills are desirable but not essential: 

• Previous study in Geotechnical Engineering or Structural Engineering 
• Ability to program in Matlab or Python 
• Previous experience in experimental geomechanics

Application Procedure

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

Candidates must submit a graduate application form and are expected to meet the graduate admissions criteria. Details are available on the course page of the University website.

Please quote 26ENGCI_OA in all correspondence and in your graduate application.

Application deadline: noon on 14 April 2026

Start date: October 2026