Geological and geotechnical characterisation for offshore wind turbine foundations: A case study of the Sheringham Shoal wind farm

Le, Thi Minh Hue; Eiksund, Gudmund; Strøm, Pål Johannes; Saue, Morten

doi:10.1016/j.enggeo.2014.05.005

Cited by 50 publications

(22 citation statements)

References 20 publications

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“…Remoulded samples tested under undrained triaxial compression showed peak φ' angles around 37.5º, assuming zero cohesion. Ring shear interface tests by the Authors in the Bishop apparatus, using mild steel interfaces to represent field pile roughness (average roughness, R a ≈ 10-15µm) values, indicate residual δ ୰ ʹ angles between 30 and 31°, similar to those reported by Le et al (2014) and Ziogos et al (2016). Bishop ring shear tests carried out by Chen (2017), on samples from the test site, indicated δ ୰ ʹ angles of between 26 and 31.5° (depending on normal effective stress level) using stainless steel interfaces prepared with roughness, R a of 1.22 µm, similar to those of industrial CPT friction sleeves.…”

Section: Site Conditionssupporting

confidence: 69%

Effective stress regime around a jacked steel pile during installation ageing and load testing in chalk

et al. 2018

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This paper reports experiments with 102 mm diameter closed-ended instrumented Imperial College piles (ICPs) jacked into low- to medium-density chalk at a well-characterized UK test site. The “ICP” instruments allowed the effective stress regime surrounding the pile shaft to be tracked during pile installation, equalization periods of up to 2.5 months, and load testing under static tension and one-way axial cyclic loading. Installation resistances are shown to be dominated by the pile tip loads. Low installation shaft stresses and radial effective stresses were measured that correlated with local cone penetration test (CPT) tip resistances. Marked shaft total stress reductions and steep stress gradients are demonstrated in the vicinity of the pile tip. The local interface shaft effective stress paths developed during static and cyclic loading displayed trends that resemble those seen in comparable tests in sands. Shaft failure followed the Coulomb law and constrained interface dilation was apparent as the pile experienced drained loading to failure, although with a lesser degree of radial expansion than with sands. Radial effective stresses were also found to fall with time after installation, leading to reductions in shaft capacity as proven by subsequent static tension testing. The jacked, closed-ended, piles’ ageing trends contrast sharply with those found with open piles driven at the same site, indicating that ageing is affected by pile tip geometry and (or) installation method.

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Section: Site Conditionssupporting

confidence: 69%

Effective stress regime around a jacked steel pile during installation ageing and load testing in chalk

et al. 2018

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“…Finite Element Analyses (FEA) of the soil volume and the foundation are performed to set the basis of the macro-element model. The FEA simulate the layered soil conditions and pile dimensions found in a real wind farm (Hamre et al, 2010, Le et al, 2014. A numerical approach was selected over physical model testing because model tests are generally costly and relatively few loading paths can be considered.…”

Section: Introductionmentioning

confidence: 99%

A macro-element pile foundation model for integrated analyses of monopile-based offshore wind turbines

et al. 2018

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The design of OWTs relies on integrated load analyses tools that simulate the response of the entire OWT (including the rotor-nacelle assembly, support structure and foundation) under combined aerodynamic and hydrodynamic loading. Despite all efforts to develop accurate integrated models, these often fail to reproduce the measured natural frequencies, partly due to the current foundation modelling. This paper presents a new foundation model for integrated analyses of monopile-based OWTs. The model follows the macro-element approach, where the response of a pile and the surrounding soil is condensed to a force-displacement relation at seabed. The model formulation uses multi-surface plasticity and it reproduces key characteristics in monopile foundation behaviour that are not accounted for in current industry practice. The basic features of the model are described and its limitations are discussed. The performance of the macro-element model is compared against field test measurements and results from FEA. The comparison indicates that the macro-element model can reproduce accurately the non-linear load-displacement response and hysteretic behaviour measured in field tests and computed in FEA. This confirms that the model can simulate the pile and soil behaviour with the same level of accuracy as FEA, but with a considerable reduction in computational effort.

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“…Medium-dense to very dense sand layers are often encountered, e.g. for two recently built wind farms (Le et al, 2014;Merritt et al, 2012). Consequently, three sand densities (loose, medium and dense) were considered in this parametric study to cover a wide range of soil conditions.…”

Section: Soil Conditionsmentioning

confidence: 99%

Optimised design of screw anchors in tension in sand for renewable energy applications

et al. 2020

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The offshore deployment of floating offshore structures such as wind turbines or wave energy converters is expected to strongly increase during the next decade, to face the appetite for green energy sources. The growing size of these structures' dimensions, inducing very large mooring forces, makes the anchoring solution adopted a critical issue for the commercial success of floating marine energy farms. The upscaling of the screw anchor technology from onshore to the offshore environment has been recently proposed as an efficient way of providing a large tension capacity while their installation generates far less noise and vibrations than impact pile driving. Most of recent studies on screw anchors have focused on separated geotechnical problems such as their uplift capacity or installation requirements. This paper incorporates within a single procedure geotechnical and structural constraints to calculate the optimal anchor geometry able to maximise the uplift capacity available. Performance envelopes for screw anchors have been derived in a parametric study, covering a broad range of soil conditions as well as in a case study, representative of offshore conditions. Results show that single screw anchors are more efficient (e.g. shorter and lighter) than driven piles to sustain tension loading. The results presented in this study support the applicability of screw anchors to be used as part of the mooring system for wave energy converters. However, tension requirements for tension-leg platform wind turbines would probably require the use of group of anchors.

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Geological and geotechnical characterisation for offshore wind turbine foundations: A case study of the Sheringham Shoal wind farm

Cited by 50 publications

References 20 publications

Effective stress regime around a jacked steel pile during installation ageing and load testing in chalk

Effective stress regime around a jacked steel pile during installation ageing and load testing in chalk

A macro-element pile foundation model for integrated analyses of monopile-based offshore wind turbines

Optimised design of screw anchors in tension in sand for renewable energy applications

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