Hibiki Project Mock-up Trial

The Hibiki Project Mock-Up Trial was conducted in 2023 at the Hibikinada trial site in Kitakyushu City Fukuoka Prefecture as part of the technical preparation for Japan’s future offshore wind developments. The trial aimed to evaluate installation procedures and material performance for monopile foundations, With SikaGrout®-9500 selected for its high durability and suitability for demanding offshore environments. By replicating real site conditions the mock-up allowed project teams to optimize processes confirm product reliability and gather essential data before full-scale project execution.

For the grouting of the connection between the wind turbine substructure (jacket) and the foundation pile (steel pipe pile), the grouting area (jacket leg/sleeve and steel pipe pile) was simulated on land using actual dimensions. Grouting is carried out using the actual materials used in this work (mixing plant, pump, etc.) and tests are conducted to confirm the filling, pressurisation, and construction of the grouting material.

The Hibiki Project took place during the hot weather months of June to September 2024. To prepare, additional trials were conducted before the offshore campaign, during which both the grout and mixing water were chilled, ensuring the material was mixed and pumped within the required temperature limits.

Sika supplied 54 MT of SikaGrout®-9500 and 1.6 MT of SikaGrout®-9000 for the mock-up trial. SikaGrout®-9500 is a high-performance, cement-based grouting material designed for ultra-high strength and exceptional fatigue durability in offshore wind turbine installations. This product is widely used for grout connections in wind turbine foundations, including the interfaces between transition pieces and monopiles, as well as within steel jacket structures.

The purpose of the trial was to measure the behaviour of the SikaGrout®-9500 grouting material from storage in a chilled warehouse to transit from the warehouse to installation in hot temperatures. The technique of chilling dry grout powder before mixing has been successfully applied in previous onshore wind turbine installations.

At 28 days, the overall compressive strength of the trial material exceeded the minimum requirements. However, the effect of the chilled grout powder was less than anticipated when compared with onshore grouting.