Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications

Jonathan A. Knappett (Lead / Corresponding author), Michael J. Brown, Andrew J. Brennan, Lewis Hamilton

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    This paper investigates the compressive behaviour of screw piles in sands and the key design parameters which control this. These types of foundation elements have typically been used as screw anchors onshore (i.e. for their tensile capacity), but there is increasing interest in their potential use as compression piles for supporting offshore marine renewable energy (MRE) devices (e.g. wind and tidal turbines) in deeper water. For such foundation applications, the compressive capacity is as important as the tensile capacity and is not well understood, particularly in cohesionless soils which are a likely seabed condition in MRE applications. A 1-g laboratory study was initially conducted on small scale model screw piles in sand beds of various relative density between 25 – 88%. These experiments were used to validate a Finite Element (FE) model having a stress-dependent constitutive model, making it useful for future up-scaling of the pile size for field applications. Following validation, the FE model was used to conduct a parametric study on the effects of flange spacing ratio (s/Dflange) and flange to shaft diameter ratio (Dflange/Dshaft). By using a validated FE model for this study, it was possible to observe the failure mechanisms (through the shear strain distribution) within the soil and correlate these with the pile capacity. This information was then used to comment on the most optimal (cost-effective) pile design for supporting compressive loads. This study represents a key step towards producing design tools appropriate for the design of screw piles in MRE applications.
    Original languageEnglish
    Title of host publicationProceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations
    PublisherDeep Foundations Institute
    Number of pages10
    VolumeIC-2014
    Publication statusPublished - 2014
    EventDFI/EFFC 11th International Conference on Piling and Deep Foundations - Stockholm Fair, Stockholm, Sweden
    Duration: 21 May 201423 May 2014
    https://www.regonline.com/builder/site/default.aspx?EventID=1221506

    Conference

    ConferenceDFI/EFFC 11th International Conference on Piling and Deep Foundations
    CountrySweden
    CityStockholm
    Period21/05/1423/05/14
    Internet address

    Fingerprint

    Piles
    Sand
    Flanges
    Soils
    Shear strain
    Constitutive models
    Anchors
    Turbines
    Costs
    Water
    Experiments

    Keywords

    • Screw piles
    • Renewable energy foundations
    • Renewable resource
    • Sand

    Cite this

    Knappett, J. A., Brown, M. J., Brennan, A. J., & Hamilton, L. (2014). Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications. In Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations (Vol. IC-2014). [1904] Deep Foundations Institute.
    Knappett, Jonathan A. ; Brown, Michael J. ; Brennan, Andrew J. ; Hamilton, Lewis. / Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications. Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations. Vol. IC-2014 Deep Foundations Institute, 2014.
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    title = "Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications",
    abstract = "This paper investigates the compressive behaviour of screw piles in sands and the key design parameters which control this. These types of foundation elements have typically been used as screw anchors onshore (i.e. for their tensile capacity), but there is increasing interest in their potential use as compression piles for supporting offshore marine renewable energy (MRE) devices (e.g. wind and tidal turbines) in deeper water. For such foundation applications, the compressive capacity is as important as the tensile capacity and is not well understood, particularly in cohesionless soils which are a likely seabed condition in MRE applications. A 1-g laboratory study was initially conducted on small scale model screw piles in sand beds of various relative density between 25 – 88{\%}. These experiments were used to validate a Finite Element (FE) model having a stress-dependent constitutive model, making it useful for future up-scaling of the pile size for field applications. Following validation, the FE model was used to conduct a parametric study on the effects of flange spacing ratio (s/Dflange) and flange to shaft diameter ratio (Dflange/Dshaft). By using a validated FE model for this study, it was possible to observe the failure mechanisms (through the shear strain distribution) within the soil and correlate these with the pile capacity. This information was then used to comment on the most optimal (cost-effective) pile design for supporting compressive loads. This study represents a key step towards producing design tools appropriate for the design of screw piles in MRE applications.",
    keywords = "Screw piles, Renewable energy foundations, Renewable resource, Sand",
    author = "Knappett, {Jonathan A.} and Brown, {Michael J.} and Brennan, {Andrew J.} and Lewis Hamilton",
    year = "2014",
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    booktitle = "Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations",
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    Knappett, JA, Brown, MJ, Brennan, AJ & Hamilton, L 2014, Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications. in Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations. vol. IC-2014, 1904, Deep Foundations Institute, DFI/EFFC 11th International Conference on Piling and Deep Foundations, Stockholm, Sweden, 21/05/14.

    Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications. / Knappett, Jonathan A. (Lead / Corresponding author); Brown, Michael J.; Brennan, Andrew J.; Hamilton, Lewis.

    Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations. Vol. IC-2014 Deep Foundations Institute, 2014. 1904.

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

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    T1 - Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications

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    AU - Brown, Michael J.

    AU - Brennan, Andrew J.

    AU - Hamilton, Lewis

    PY - 2014

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    N2 - This paper investigates the compressive behaviour of screw piles in sands and the key design parameters which control this. These types of foundation elements have typically been used as screw anchors onshore (i.e. for their tensile capacity), but there is increasing interest in their potential use as compression piles for supporting offshore marine renewable energy (MRE) devices (e.g. wind and tidal turbines) in deeper water. For such foundation applications, the compressive capacity is as important as the tensile capacity and is not well understood, particularly in cohesionless soils which are a likely seabed condition in MRE applications. A 1-g laboratory study was initially conducted on small scale model screw piles in sand beds of various relative density between 25 – 88%. These experiments were used to validate a Finite Element (FE) model having a stress-dependent constitutive model, making it useful for future up-scaling of the pile size for field applications. Following validation, the FE model was used to conduct a parametric study on the effects of flange spacing ratio (s/Dflange) and flange to shaft diameter ratio (Dflange/Dshaft). By using a validated FE model for this study, it was possible to observe the failure mechanisms (through the shear strain distribution) within the soil and correlate these with the pile capacity. This information was then used to comment on the most optimal (cost-effective) pile design for supporting compressive loads. This study represents a key step towards producing design tools appropriate for the design of screw piles in MRE applications.

    AB - This paper investigates the compressive behaviour of screw piles in sands and the key design parameters which control this. These types of foundation elements have typically been used as screw anchors onshore (i.e. for their tensile capacity), but there is increasing interest in their potential use as compression piles for supporting offshore marine renewable energy (MRE) devices (e.g. wind and tidal turbines) in deeper water. For such foundation applications, the compressive capacity is as important as the tensile capacity and is not well understood, particularly in cohesionless soils which are a likely seabed condition in MRE applications. A 1-g laboratory study was initially conducted on small scale model screw piles in sand beds of various relative density between 25 – 88%. These experiments were used to validate a Finite Element (FE) model having a stress-dependent constitutive model, making it useful for future up-scaling of the pile size for field applications. Following validation, the FE model was used to conduct a parametric study on the effects of flange spacing ratio (s/Dflange) and flange to shaft diameter ratio (Dflange/Dshaft). By using a validated FE model for this study, it was possible to observe the failure mechanisms (through the shear strain distribution) within the soil and correlate these with the pile capacity. This information was then used to comment on the most optimal (cost-effective) pile design for supporting compressive loads. This study represents a key step towards producing design tools appropriate for the design of screw piles in MRE applications.

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    KW - Renewable energy foundations

    KW - Renewable resource

    KW - Sand

    M3 - Conference contribution

    VL - IC-2014

    BT - Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations

    PB - Deep Foundations Institute

    ER -

    Knappett JA, Brown MJ, Brennan AJ, Hamilton L. Optimising the compressive behaviour of screw piles in sand for marine renewable energy applications. In Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations. Vol. IC-2014. Deep Foundations Institute. 2014. 1904