A Toolbox for Optimizing Geotechnical Design of Subsea Foundations

This paper presents a toolbox for optimizing geotechnical design of subsea foundations. The geotechnical design challenge of subsea shallow foundations is to withstand greater dead and operational loads on soft seabeds without increasing the footprint size or weight. The motivation is to reduce costs associated with installation – for example eliminating the need for a heavy-lift vessel to place foundation units alone if handling limits of pipe-laying vessels are exceeded – whilst providing acceptable in-service reliability. The tools presented focus on prediction of undrained seabed response and are intended for deep water developments on fine grained seabeds, as this scenario presents a significant challenge in terms of minimizing subsea foundation footprints. The toolbox addresses optimization of geotechnical subsea foundation performance through four aspects: (i) optimizing the analysis methodology, (ii) modifying the foundation configuration, (iii) improving the site characterisation data as input to the design, and (iv) altering the basis of design. The research presented derives from a combination of physical model testing in a geotechnical centrifuge, numerical analysis and theoretical modelling. The methods, procedures and processes are presented in terms of design equations, theoretical frameworks or design charts, many of which are freely available as web-based applications. Worked examples throughout the paper demonstrate the efficiencies in terms of footprint area to be realized through adoption of these tools.