SPT Offshore launches its new Tri-Suction Pile Caisson concept for wind turbine foundations. The concept combines the advantages of inexpensive mono tubulars with the fast installed suction pile foundation.
In between the three (3) or potentially four (4) suction piles and the mono tubular sits the star shaped transition piece. The mono tubular has its advantages of being inexpensive to fabricate of approx. 3 times less expensive than jackets. The suction piles have their inherent advantages of fast installation (in order of 3 hours simultaneously including levelling) and the virtually noise free technique, thereby not hindered by noise restrictions and safe for our sea mammals. Furthermore, suction piles do not cause any shocks to the foundation, so that single piece installation up to the work platform is possible. From our vast experience after having installed > 500 suction piles, we also know that suction piles are significantly optimized if smaller outer diameters are being selected compared to its depth. This reduces the weight and improves its reliability and strength. Furthermore, in order to make suction piles more effective, the suction piles should be placed horizontally further apart, hence this load transfer from the mono tubular to the suction piles requires a transition piece. The transition piece can be built out of steel or concrete and we have not yet determined which material performs best. Concrete has it pros and cons, it is cheap to fabricate but is heavier for handling by a heavy lift crane vessel. Steel has the benefits of being light and simple to build and the design process is more flexible and allows a shorter fabrication schedule. On top of the suction piles and also on top or possibly inside the transition piece there is room for added ballast, which can be pre-installed or combined with rock scour protection measures after installation. Suction piles are suited for 99% of the North Sea and most shallow water areas worldwide having sandy, clayey or layered soils. We are further detailing the design right now and are working towards a demonstration in the next 12 months.