Subsea power cable geotechnical stability for offshore wind applications

Offshore wind is already making considerable contributions to the transition towards zero-carbon and the shift to renewable energy. This is particularly relevant for the UK, whose location enables large scale offshore installations, and whose policy framework and research initiatives have placed it on top of offshore capacity in Europe. The further development of offshore wind is dependent on improving reliability and cost-effectiveness and ensuring resilience via technology development, design optimisation and risk mitigation. Besides, increasing sectoral energy interdependencies, ageing nearshore infrastructure and re-powering potential, deep-water wind farm projects and more extreme weather events, make the development and maintenance of the offshore wind infrastructure extremely critical. This is in reference to all parts of a wind farm, including the subsea power cabling system responsible for transferring power and data between the wind turbines and the shore.
For most current offshore wind applications, the wind turbines and offshore power substations are bottom fixed, and are linked with each other and with the onshore substations through arrays of static power cables either laid on the seabed or buried/rock dumped for protection and they are connected to the offshore units via tube interfaces. The environmental conditions and the geohazards impose loading and movement on the cables and may affect their effective embedment and bearing capacity. Current geotechnical design is based on technology transfer from pipeline design, not taking into account the differences in geometry, configuration and loadings and overlooking dynamic behaviour. In addition, current research focuses on new foundation designs and floating wind applications, failing to draw attention to the importance of the transmission system reliability and cost-effectiveness in the long term.
The main objectives of this project are to identify the research gaps and uncertainties in the current pipeline design knowledge transfer, study the geotechnical behaviour of embedded static cables and propose findings that can inform and optimise the future industry practices. This includes the study of power cable -flow-seabed interactions to acquire a better understanding of the geotechnical stability, kinematics at failure, embedment loss, interface loading, and applications to integrated structural modelling for accurate cable performance estimations. As a side project, marine clayey sediment erosion is explored in relation to geohazards and potential effects to cable embedment and therefore the geotechnical stability and structural performance.

The primary impact of the FIBE2 CDT will be the benefit to society that will accrue from the transformative effect that FIBE2 graduates will have upon current and future infrastructure. The current FIBE CDT has already demonstrated significant impact and FIBE2 will extend this substantially and with particular focus on infrastructure resilience. There will be further impacts across academic research, postgraduate teaching, industry-academia partnering and wider society. Our CDT students are excellent ambassadors and their skills and career trajectories are inspirational. Their outputs so far include >40 journal and conference papers, contributions to a CIRIA report, a book chapter and >15 prizes (e.g. Cambridge Carbon Challenge, EPSRC Doctoral Prizes, best presentation awards). Our students' outreach activities have had far reaching impacts including: Science Festival activities and engineering workshops for school girls. Our innovative CDT training approaches have shifted the culture and priorities in academia and industry towards co-creation for innovation. Our FIBE CDT features in the EPSRC document 'Building Skills for a Prosperous Nation'. Our attention to E&D has resulted in 50% female students with the inspirational ethos attracting students from wide ranging educational backgrounds.

FIBE2 CDT will build on this momentum and expand the scope and reach of our impact. We will capitalise on our major research and training initiatives and strategic collaborations within academia, industry and government to train future infrastructure leaders to address UK and global challenges and this will have direct and significant technical, economic and social impacts for UK infrastructure, its associated stakeholders and civil society at large.

As well as the creation of cohorts of highly skilled research cohorts with cross-disciplinary technical skills, further specific impacts include:

-a transformational cross-disciplinary graduate training and research approach in infrastructure with depth and breadth.

-new forms of Industry-University partnerships. Co-creation with industry of our training and research initiatives has already led to new forms of partnerships such as the I+ scheme, and FIBE2 will further extend this with the 'employer model' variant and others.

-skilled research-minded challenge-focused graduates for UK employers who will derive significant benefit from employing them as catalysts for enterprise, knowledge exchange and innovation, and thus to business growth opportunities.

-enhanced global competitiveness for industrial partners. With our extensive network of 27 industry partners from across all infrastructure sectors who will actively shape the centre with us, we will deliver significant impact and will embrace the cross-disciplinary research emergeing from the CDT to gain competitive advantage.

-support for policy makers at the highest levels of national and local government. The research outcomes and graduates will contribute to an evidence-based foundation for improved decision-making for the efficient management, maintenance and design of infrastructure.

-world-class research outcomes that address national needs, via the direct engagement of our key industrial partners. Other academic institutions will benefit from working with the Centre to collectively advance knowledge.

-wider professional engagement via the creation of powerful informal professional networks between researchers, practitioners, CDT alumni and CDT students, working nationally and internationally, including some hosted by FIBE2 CDT industry partners.

-future generations of infrastructure professional inspired by the FIBE2 CDT's outreach activities whereby pupils, teachers and parents gain insight into the importance of infrastructure engineering.

-the generation of public awareness of the importance of a resilient infrastructure to address inevitable and often unexpected challenges.