A monopile ([ ˈmɒnəʊ paɪl ]; composed of the Greek word mónos for “alone”, “only”, “one” and the English word pile for “ pile ”) is a form of foundation for offshore structures. Mainly used Monopiles used in the construction of offshore - wind turbines in shallow waters.
A foundation with a monopile consists, according to the name, of a single, round steel pile that is rammed into the seabed by a construction ship or jack-up platform and the upper end of which protrudes from the surface of the water. The slimness and simplicity of the construction is advantageous on the one hand, since a foundation element can be manufactured and transported very inexpensively and in a space-saving manner. In addition, the intervention in the seabed is limited to a very small area, which reduces the preparatory work to a minimum. A scour protection made of loose stones, which may be necessary, is also easy to manufacture. On the other hand, slimness limits the maximum possible length. Monopiles are therefore used up to a water depth of around 20 m, with the development of larger monopiles continuing.
In order to ensure secure anchoring, the pile must generally be embedded in the ground for at least half of its length, so that pipes over 40 m in length are used. There must be no major stone obstacles in the ground over the entire length, which limits its use to sandy, not rocky soils. The diameter of monopiles is in the range of several meters. In 2003, the design-related maximum diameter was still 5 m, in 2013 piles with a diameter of 6 m could already be driven successfully - at the end of 2016 it was up to 8 m - which extends the use to areas with a water depth of up to 35 m. The mere installation of a monopile only takes about two hours.
In order to reduce the disturbance of marine animals by the noises in the water when ramming in, bubble curtains are used, which break the sound generated in the pipes and reduce the noise. In comparison to impact ramming, vibration ramming is being tested, which, in addition to reducing noise, promises less signs of fatigue in the piles as well as faster and cheaper ramming.
Another option for installing the foundation piles is by flushing. A special flushing process for the installation of offshore foundations (SIOF) was developed for this purpose.
One way to stabilize monopiles in deep waters is to brace them to the side with steel cables or chains. However, the construction loses the advantage of quick erection and is an invisible obstacle for shipping.
- Peter Quast: Foundations for offshore wind turbines. (PDF; approx. 710 kB) (No longer available online.) Grundbauingenieure Steinfeld und Partner GbR, 2003, p. 10 ff. , Archived from the original on December 11, 2013 ; Retrieved November 17, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- Foundations and foundation structures. offshore-windenergie.net, archived from the original on January 10, 2015 ; Retrieved November 17, 2013 .
- Torsten Thomas: Monopiles in XXL format . In: Schiff & Hafen , issue 9/2016, pp. 160–162
- First monopile is installed. (No longer available online.) DanTysk Offshore Wind GmbH, March 13, 2013, archived from the original on December 11, 2013 ; Retrieved November 17, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- driving of foundations could reduce costs . In: Ship & Harbor . Issue 6/2014, p. 53 .
- Gerd Holbach, Anna Loewe, Sebastian Ritz: Flushing method for the installation of offshore foundations . In: Hansa . Issue 11/2013. Schiffahrts-Verlag Hansa, 2013, ISSN 0017-7504 , p. 22-24 .