Subsea power cable geotechnical stability for offshore wind applications

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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.