A method to quantify the beneficial effect of scour protection on lateral behaviour of monopiles for offshore wind turbines

• Published in: Ocean engineering 2024-09, Vol.307, p.118196, Article 118196
• Main Authors: Li, Q., Prendergast, L.J., Gavin, K.G., Askarinejad, A., Wang, X.Q.
• Format: Article
• Language: English
• Subjects: Centrifuge tests; Finite element analyses; Lateral loading behaviour; Monopiles; Scour protection; Slenderness ratios
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2024.118196

To mitigate against scour hole formation, scour protection can be placed around offshore wind turbine monopiles. Few studies have considered the beneficial effect of this geotechnical reinforcement measure on the foundation lateral resistance. The contribution of scour protection to lateral resistance of monopiles in sand is investigated in this paper using centrifuge tests and finite element analyses. Multiple scour protection widths and thicknesses are modelled around a monopile, to identify the most effective scour protection properties at mitigating lateral displacements. Two methods for modelling scour protection effects (one using material, the other using direct overburden pressure) are compared. The lateral response of monopiles with different slenderness ratios under various scour protection widths and overburden pressures are simulated. Results suggest that pile lateral displacements reduce by up to 41% when scour protection with width 2D (D, pile diameter) and applied overburden pressure of 30 kPa is used, compared to no scour protection, for a given test case. A method to modify design approaches to consider the beneficial contribution of scour protection on pile lateral behaviour using an envelope diagram is proposed, which provides relationships for scour protection properties and various monopile slenderness ratios. •Influence of scour protection on lateral monopile behaviour is investigated•Two methods to model scour protection are used, “material method” and “stress method”•Multiple protection widths and thicknesses are modelled to understand optimum properties•“Material method” provides more benefit to pile lateral resistance than “stress method”•A method to reduce pile length taking the beneficial influence of scour protection into account is demonstrated