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SOURCE: Improved insitu Stiffness measurements for Offshore foundation design considering Uncertainty, Repeatability and Common sources of Error

Lead Research Organisation: University of Glasgow
Department Name: College of Science and Engineering

Abstract

The UK is the world leader in offshore wind energy; almost 40% of global capacity is installed in UK waters. A new ambitious target of 40GW of wind power by 2030 aims to produce sufficient offshore wind capacity to power every home, helping to achieve net zero carbon emissions by 2050. Offshore wind turbine (OWT) foundations, which are typically steel monopiles, contribute approximately 25% to a windfarm's capital cost. The size of OWTs is increasing rapidly and continued optimisation of foundation design is paramount. Recent research has led to significant advances through theoretical developments combined with high-quality field-testing. Despite recent advances, there remains significant uncertainty in the measurement and interpretation of key soil deformation parameters that underpin new and existing design approaches.

The central aim of SOURCE is to use rigorous measurement and interpretation in the field and laboratory to quantify and reduce material parameter uncertainty and minimise the impact on the predictive capability of OWT foundation design methods. Improved site characterisation will contribute to increased security in design, lowering capital costs, subsidies and carbon emissions and meeting the UK's ambitious new energy targets.
 
Description SOURCE delivered key insights on the acquisition, interpretation and uncertainty quantification of in situ stiffness measurements for use in offshore foundation design methods. The research programme involved (1) multi-method geophysical and geotechnical testing at three test bed sites (2) advanced laboratory testing developments and (3) algorithmic developments in signal processing and uncertainty quantification.
A core outcome of the project is a new approach to quantify uncertainty in downhole geophysical testing. The outcomes demonstrated that measurement error in downhole seismic data can be explicitly identified, modelled, and quantified, something conventional interpretation cannot do. A Bayesian framework was introduced that automatically separates true and pseudo measurement errors, producing coherent, uncertainty bounded shear wave velocity profiles even from imperfect data. This advances understanding of how acquisition errors affect V? results and offers the first practical way to estimate these errors directly from field data. Work is continuing to extend this approach to non-invasive testing.
Analysis at the chalk dominated site importantly showed that targeted test execution and data acquisition are essential in these relatively high velocity materials. Thin features such as flint bands and dissolution structures are best characterised using smaller receiver spacing or finer depth increments, and test selection should be tailored to the application. Overall, the results confirm that mass stiffness in chalk is governed by fracture networks, limiting the usefulness of laboratory element tests and reinforcing the need for in situ measurements. New practical recommendations for obtaining high-quality, application-specific measurements were outlined.
The laboratory work demonstrated that much of the long-observed frequency-dependent variability in resonant column calibration arises from drive system compliance, rather than from true physical changes in apparatus inertia or specimen behaviour. Through finite element analysis, the distribution of torsional flexibility within the drive system was quantified showing that the majority originates in the drive arms and magnet interfaces. A modified linear-elastic, two-body drive compliance model is introduced that accurately captures this behaviour. This leads to a novel calibration method that successfully removes the apparent frequency dependency of calibration parameters, enabling more reliable determination of small-strain shear modulus, particularly for stiff specimens where traditional assumptions fail. The new methodology is already being applied by industry partners in their laboratories.
The high-quality SOURCE data also underpinned the development of a data-driven Bayesian framework to transform CPT-based soil classification from deterministic chart reading into a probabilistic, multi-feature modelling problem. By training on over half a million curated data points and incorporating automated data cleaning, and multinomial Bayesian inference, it reveals how soil types can be predicted with quantified uncertainty rather than fixed boundaries. This provides new understanding of class overlap, improves interpretability of CPT data, and demonstrates, for the first time at this scale, a practical, updateable probabilistic model for global and site-specific soil classification.
Exploitation Route SOURCE generated valuable resources for researchers, including experimental protocols, curated datasets and specialised software tools, enabling replication, validation, and extension of the project's findings.
Sectors Construction

Energy
 
Description As part of the project we have developed new calibration methods for resonant column devices and a new automatic uncertainty quantification approach for downhole seismic testing. Both of these are being applied by project partners in the UK and the Netherlands. A recent paper (doi: 10.53243/ISFOG2025-504) outlines the implementation of the latter method by a major international survey company. The high quality results at the chalk dominated site have been used to recalibrate constitutive models and develop new design approaches for laterally loaded piles in chalk.
First Year Of Impact 2023
Sector Construction,Energy
Impact Types Economic
 
Description Scientific Advisor Role
Geographic Reach Europe 
Policy Influence Type Participation in a guidance/advisory committee
Impact iCRAG's research programme addresses key research challenges in applied geosciences with the overarching aim of helping to unlock Ireland's natural resources while protecting the environment. Our multidisciplinary teams are developing improved technical knowledge and innovative techniques to increase the success rate of energy, mineral and groundwater exploration. iCRAG researchers are also investigating methods to aid our understanding of Ireland's environment and how the quality of our environment can be safeguarded and protected.
URL https://www.icrag-centre.org/people/advisorycommittees/scientificadvisorycommittee/
 
Description Feasibility of novel Distributed Acoustic Sensing for geotechnical applications
Amount £4,000 (GBP)
Funding ID EP/X5257161/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 06/2024 
End 07/2025
 
Description ICURe Discover - Strataguide
Amount £2,500 (GBP)
Funding ID DSSEP25-35 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 08/2025 
End 12/2025
 
Description Application of Distributed Acoustic Sensing at SOURCE sites 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution During a steering committee meeting an idea was formed to trial Distributed Acoustic Sensing at the SOURCE sites. Distributed acoustic sensing can give more continuous and stable measurements than traditional sensors, however its use in geotechnics is not well documented. The research team and PI assessed the feasibility and constructability of the technology before contacting additional partners.
Collaborator Contribution A collaboration is underway with the University of Leeds' Institute for Applied Geoscience who have expertise in DAS technology. In late 2024 we successfully installed and tested the DAS technology at the third SOURCE site. For this work we have leveraged additional IAA funding to support a PhD student contributing to the fieldwork. The results are still under analysis but are extremely promising.
Impact TBC. Multi-disciplinary - geotechnics and earth science
Start Year 2023
 
Description Implementation of new outcomes in industry workflows 
Organisation Ocean Infinity
Country United States 
Sector Private 
PI Contribution We were contacted by survey company Ocean Infinity after they saw a conference presentation on our new method for uncertainty quantification in downhole seismic testing. We worked with them to apply the method successfully to their data showing its direct industry impact.
Collaborator Contribution The partner acquired the offshore data and provided the raw data files to us. They also attended meetings for discussion on the results and helped draft a conference paper.
Impact https://www.issmge.org/uploads/publications/132/133/ISFOG2025-504.pdf
Start Year 2024
 
Description Steering committee meetings 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Kick of meeting to commence the project in Nov 2022. Regular steering committee meetings thereafter. These have been essential in developing the research ideas, keeping the research on track and communicating early outcomes.
Year(s) Of Engagement Activity 2023,2024,2025