Chapter 5: Improving the lateral capacity of monopiles in submarine clay

The offshore wind sector in the European Union is undergoing phenomenal growth, with forecasts indicating its installed capacity in the year 2020 to be 40 GW, representing an eight-fold increase from its current capacity of 5 GW (EWEA, 2013). Due to their ease of fabrication and installation, monopiles are currently the most popular type of foundation for supporting offshore wind turbines in shallow to medium-depth waters of up to 30 m. Monopiles are driven open-ended tubular steel piles, 4–6 m in diameter, with an embedded length to diameter ratio of 4–8. With offshore wind farms increasingly being located further away from the shore and wind turbines increasing in size, larger monopiles are required to withstand the corresponding structural and environmental loads. However, they would be impractical to install using current offshore technology. Therefore, it is vital that an improvement in monopile lateral capacity is investigated using hybrid features that are feasible to construct and install.