On the selection of an appropriate consolidation coefficient for offshore geotechnical design

David White, Jinbo Chen, Susan Gourvenec, Conleth O’Loughlin

    Research output: Chapter in Book/Conference paperConference paper

    1 Citation (Scopus)

    Abstract

    This paper addresses the selection of an appropriate consolidation coefficient for the analysis of drainage beneath foundations and pipelines in offshore geotechnical design. An emerging trend in the design of subsea infrastructure is the consideration of ‘whole life’ effects – namely the changes in soil properties and geotechnical capacity over the operating life. Seabed pipelines that undergo repeated thermal expansion and contraction cause shearing and consolidation in the underlying soil, leading to significant changes in the available seabed friction. Also, foundations that are either fixed or designed to slide on the seabed, are subjected to intermittent loads interspersed with periods of consolidation. These also cause a change in seabed strength and geotechnical capacity. To assess the time over which these effects occur, and therefore their influence on the response and the reliability of the system, it is necessary to perform consolidation calculations, using an appropriate consolidation coefficient. This paper presents observed operative consolidation coefficients drawn from recent model testing measurements and numerical analyses. It is shown that the consolidation rate can vary by more than an order of magnitude for the same soil profile under different loading conditions, due to the differences in stiffness and permeability. Meanwhile, design parameters are commonly drawn from one-dimensional oedometer compression tests. This compendium of data highlights the potential variation in consolidation coefficient for different loading types and through the ‘whole life’ of infrastructure. A key conclusion is that consolidation effects generally occur faster than is commonly assumed, meaning that changes in strength and stiffness – that are commonly beneficial in design – may be more readily relied on than is done so in current practice.

    Original languageEnglish
    Title of host publicationOffshore Technology; Offshore Geotechnics
    Place of PublicationUSA
    PublisherThe American Society of Mechanical Engineers (ASME)
    ISBN (Electronic)9780791858769
    DOIs
    Publication statusPublished - 11 Nov 2019
    EventASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2019 - Glasgow, United Kingdom
    Duration: 9 Jun 201914 Jun 2019

    Publication series

    NameProceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE
    Volume1

    Conference

    ConferenceASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2019
    CountryUnited Kingdom
    CityGlasgow
    Period9/06/1914/06/19

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  • Cite this

    White, D., Chen, J., Gourvenec, S., & O’Loughlin, C. (2019). On the selection of an appropriate consolidation coefficient for offshore geotechnical design. In Offshore Technology; Offshore Geotechnics (Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE; Vol. 1). The American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/OMAE2019-95800