Observations of the Effects of a Clay Layer on Suction Bucket Installation in Sand

AbstractSuction buckets are becoming established as a viable foundation solution for offshore wind turbines. In sand, suction-induced seepage flow reduces effective stresses at the skirt tips, which decreases penetration resistance. However, layered seabeds are often encountered in areas of offshore...

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Bibliographic Details
Published in:Journal of geotechnical and geoenvironmental engineering 2020-05, Vol.146 (5)
Main Authors: Ragni, Raffaele, Bienen, Britta, O’Loughlin, Conleth D, Stanier, Samuel A, Cassidy, Mark J, Morgan, Neil
Format: Article
Language:English
Subjects:
Buckets
Centrifuge model
Centrifuges
Clay
Deformation
Flow
Installation
Ocean floor
Offshore
Offshore energy sources
Offshore operations
Penetration
Penetration resistance
Perspex
Sand
Seepage
Suction
Technical Papers
Turbine engines
Turbines
Uplift
Wind effects
Wind farms
Wind power
Wind turbines
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Summary:AbstractSuction buckets are becoming established as a viable foundation solution for offshore wind turbines. In sand, suction-induced seepage flow reduces effective stresses at the skirt tips, which decreases penetration resistance. However, layered seabeds are often encountered in areas of offshore wind farm development. The effect of the presence of a clay layer on the suction-induced seepage flow in the sand layer is not well understood. Therefore in this study, the effects of a clay layer on suction bucket installation in dense sand was investigated. This was achieved by analyzing images of a half-bucket installed against a Perspex window. The images were captured during tests performed in a geotechnical centrifuge, such that the stress levels are realistic and relevant to field conditions. Installations in sand-over-clay were unproblematic and characterized by deformation of the sand-clay interface, with no clear interruption of the seepage flow. Installations in clay-over-sand were also successful. Uplift of the clay plug was identified as the mechanism to transfer suction to the underlying sand, creating seepage flow and thus facilitating further skirt penetration rather than terminating the installation.
ISSN:1090-0241
1943-5606
DOI:10.1061/(ASCE)GT.1943-5606.0002217