Impact of scour on lateral resistance of wind turbine monopiles: an experimental study

Li, Qiang; Askarinejad, Amin; Gavin, Kenneth

doi:10.1139/cgj-2020-0219

Cited by 15 publications

(5 citation statements)

References 27 publications

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“…The experiments were performed using the beam centrifuge at Delft University of Technology [12,13] with a centrifugal acceleration rate of 100× g. An open-ended steel pipe pile with outer diameter of D = 1.8 m and wall thickness of t = 3 cm in prototype size was modelled. The pile had an embedded length of L = 9 m, as well as a slenderness ratio (L/D) of 5, which is widely used in offshore foundations [14,15].…”

Section: Centrifuge Modelling 21 Model Pile and Soil Characterisationmentioning

confidence: 99%

Influence of Scour Protection on the Vertical Bearing Behaviour of Monopiles in Sand

Li,

Wang,

Gavin

et al. 2024

Water

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Extensive studies have been performed on the effectiveness of scour protection against scour erosion progression. But there is little research to date evaluating the effect of scour protection on vertical resistance behaviour of monopile foundations. This paper investigates the influence of scour protection on the vertical loading behaviour of monopiles installed in sand using centrifuge tests and finite element analysis (FEA). Four scour protection widths (1D, 2D, 3D, 4D; where D is the pile diameter) and three scour protection thicknesses (1 m, 2 m, 3 m) were modelled on a pile with a slenderness ratio (L/D) of five. In the FEA, the scour protection mechanism was modelled using two strategies, namely the ‘stress method’ by applying stress and the ‘material method’ by applying virtual material on the seabed surface around the pile. Outcomes between these two strategies were compared, and the contact coefficient δ used in the ‘material method’ for describing the contact effectiveness of the overlaying scour protection material with the pile structure was introduced, providing a more scientific and accurate calculation reference for engineering applications. The results indicated that the vertical capacity of monopiles could be increased by 5% to 23% by adopting the scour protection measure, depending on the scour protection width and scour protection thickness.

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Section: Centrifuge Modelling 21 Model Pile and Soil Characterisationmentioning

confidence: 99%

Influence of Scour Protection on the Vertical Bearing Behaviour of Monopiles in Sand

Li,

Wang,

Gavin

et al. 2024

Water

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“…p-y curves can be derived from bending moment profiles, where p is derived by double differentiation of the moment profile, and y at discrete locations is obtained by double integration of the moment profile, see Li et al (2020a) for procedure. The rotation point is assumed at 0.7L along the pile (Fan et al, 2017, Chortis et al, 2020.…”

Section: Influence Of Vertical Loading On P-y Curves For Monopilesmentioning

confidence: 99%

Experimental and numerical investigation of the effect of vertical loading on the lateral behaviour of monopiles in sand

Gavin

Askarinejad

et al. 2022

Can. Geotech. J.

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The influence of combined loading on the response of monopiles used to support offshore wind turbines (OWTs) is investigated in this paper. In current practice, resistance of monopiles to vertical and lateral loading is considered separately. As OWT size has increased, the slenderness ratio (pile length, L, normalised by diameter, D) has decreased, and foundations are tending towards intermediate footings with geometries between those of piles and shallow foundations. Whilst load interaction effects are not significant for slender piles, they are critical for shallow footings. Previous research on pile load interaction has resulted in conflicting findings, potentially arising from variations in boundary conditions and pile slenderness. In this study, monotonic lateral load tests were conducted in a geotechnical centrifuge on vertically loaded monopiles in dense sand. Results indicate that for piles with L/D = 5, increasing vertical loading improved pile initial stiffness and lateral capacity. A similar trend was observed for piles with L/D = 3, when vertical loading was below ≈ 45% of the pile’s ultimate vertical capacity. For higher vertical loads considered, results tended towards the behaviour observed for shallow footings. Numerical analyses conducted show that changes in mean effective stress are potentially responsible for the observed behaviour.

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“…The shapes of common types of scour holes are illustrated in Figure 1, where α denotes the scour slope angle, Wt denotes the top scour width, Wb denotes the bottom scour width, Ds denotes the scour depth and z denotes the depth below the original mudline. [22]). Some previous works on the effect of scour on monopiles are detailed herein.…”

Section: Introductionmentioning

confidence: 99%

Scour Effect on the Lateral Bearing Behaviour of Monopiles Considering Different Slenderness Ratios

Li,

Wang,

Gavin

et al. 2024

Water

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Scour leads to the loss of soil around monopile foundations for offshore wind turbines, which affects their structural safety. In this paper, the effect of scour on the lateral behaviour of monopiles was extensively investigated using finite element analysis, and calibration and comparison were undertaken using centrifuge tests. Piles with three slenderness ratios, i.e., 3, 5 and 8, were studied by keeping the diameter constant and varying the embedment length. Three scour types (local narrow, local wide and global) and four scour depths (0.5D, 1D, 1.5D and 2D; D signifies the pile diameter) were considered in this investigation. The results indicate that the lateral resistance of the pile is the greatest in the case of local narrow scour, followed by that in the cases of local wide scour and global scour. When the scour depth is larger than 1D, the influence of the scour type on the pile lateral bearing behaviour is insignificant. The influence of the scour type and scour depth on the pile lateral bearing behaviour is broadly similar for piles with slenderness ratios of 3, 5 and 8. However, the piles featured with smaller embedment lengths show a larger decrease rate in their lateral capacity, which means the effect of scour should cause more concern on small slenderness ratio monopiles.

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Impact of scour on lateral resistance of wind turbine monopiles: an experimental study

Cited by 15 publications

References 27 publications

Influence of Scour Protection on the Vertical Bearing Behaviour of Monopiles in Sand

Influence of Scour Protection on the Vertical Bearing Behaviour of Monopiles in Sand

Experimental and numerical investigation of the effect of vertical loading on the lateral behaviour of monopiles in sand

Scour Effect on the Lateral Bearing Behaviour of Monopiles Considering Different Slenderness Ratios

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