Intermediate Offshore Foundations

Intermediate foundations are used as anchors for floating platforms and ancillary structures, foundations for steel jackets, and to support seafloor equipment and offshore wind turbines. When installed by suction, they are an economical alternative to piling, and also may be completely removed. They are usually circular in plan and are essentially rigid when laterally loaded. Length to diameter embedment ratios, L/D, generally vary between 0.5 and 10, spanning the gap between shallow and deep foundations, although these are indicative boundaries and the response, rather than the embedment ratio, defines an intermediate foundation. The first chapters introduce foundation types; compare shallow, intermediate and deep foundation models and design; define unique design issues that make intermediate foundations distinct from shallow and deep foundations, as well as list their hazards that mainly occur during installation. Later chapters cover installation, in-place resistance and in-place response, and miscellaneous design considerations. There is no general agreement as to which design methods/models are appropriate, so models should only be as accurate as the data. Therefore, several reasonably accurate models are provided together with comprehensive discussion and advice. Example calculations and over 200 references are also included. This is the first book dedicated to the geotechnical design of intermediate foundations, and it will appeal to professional engineers specialising in the offshore industry.

1.Introduction2.Offshore Foundation Types and Mode of Operation3.Loads4.Marine Geology5.Loading Conditions and Soil Drainage6.Hazards, Uncertainties and Risk Minimisation7.Investigation Programs8.Design Basis9.Installation, Retrieval and Removal 10.In-Place Resistance11.In-Place Response12.Miscellaneous Design Considerations

The late Steve Kay was an independent Geotechnical Consultant with thirty-three years’ experience as a Principal Engineer with Fugro, and over forty-five years as a geotechnical specialist, mainly in the oil and gas industry, both with contractors and consultants. His expertise was in shallow and intermediate (caisson, bucket, can) foundation design, with extensive worldwide experience in offshore, nearshore and land engineering. He gave suction foundation courses, master classes and wrote the commercially available software package CAISSON_VHM. Susan Gourvenec is Royal Academy of Engineering Chair in Emerging Technologies in Intelligent & Resilient Ocean Engineering, and Professor of Offshore Geotechnical Engineering at the University of Southampton, UK. Susan is currently Convenor of the International Standardisation Organisation (ISO) committee responsible for developing industry standards for marine soil investigation and offshore geotechnical design. Susan co-authored Offshore Geotechnical Engineering (CRC Press, 2011) and co-edited the proceedings of the inaugural and second International Symposia on Frontiers in Offshore Geotechnics (ISFOG). Elisabeth Palix has eighteen years’ experience in offshore geotechnics. She spent twelve years working for Fugro Geoconsulting before joining EDF Renouvelables, where she is working on design and installation aspects of offshore projects. Elisabeth is also a member of the TC 209 (ISSMGE) and has been involved in several geotechnical R&D projects (e.g. SOLCYP, SOLCYP+, PISA, Unified CPT-based methods). Etienne Alderlieste is a Senior Geotechnical Researcher/Consultant for Deltares, where he is working on installation and in-place capacity of intermediate and shallow offshore foundations. Before joining Deltares, Etienne worked as Senior Geotechnical Engineer at SPT Offshore, where he designed suction foundations for the oil, gas and offshore wind industry. He also installed and reinstalled numerous single-suction anchors and several jacket structures with suction foundations worldwide.