Geotechnical analysis of offshore pipelines and steel catenary risers

Matthew Steven Hodder

    Research output: ThesisDoctoral Thesis

    837 Downloads (Pure)

    Abstract

    As hydrocarbon developments move further offshore into deeper water, the pipelines and risers used in the transportation of oil and gas form an increasingly significant component of the development infrastructure. Offshore pipelines and risers must be designed to withstand exposure to a range of loading conditions throughout their lifetime. On-bottom pipelines laid directly on the seabed must be shown to be stable and not become overstressed when subjected to environmental and operational loads. Similarly, risers, which transport hydrocarbon products between deep water floating platforms and the seabed, are subjected to various cyclic loadings and must be shown to not suffer from fatigue damage. The interaction of the pipeline or riser with the seabed serves as boundary conditions in a structural analysis of the system. Therefore, an accurate representation of the geotechnical behaviour in a pipe-soil interaction model is critical to the assessment of structural response. This thesis investigates the interaction of cylindrical objects with soil, and its application to the analysis and design of offshore pipelines and risers. The behaviour observed during experimental investigations performed to assess the effect of various loading conditions on pipe-soil interaction response is used to develop analytical models which are appropriate for use in an integrated soil-structure interaction assessment of the pipe-soil system. The combined vertical-lateral behaviour of on-bottom pipelines is explored. An interaction model is presented which is applicable to the prediction of pipeline response when subjected to combined vertical and lateral loading on a soft clay seabed in undrained conditions. The effects of various vertical cyclic loading regimes on pipe-soil interaction in soft clay are investigated experimentally. Results from a suite of tests exploring a wide range of vertical cyclic loading conditions in the touchdown zone of a steel catenary riser are presented
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2009

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