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Suction caissons (also referred to as suction anchors, suction piles or suction buckets) are a new form of offshore foundation that have a number of advantages over conventional offshore foundations, mainly being quicker to install than piles and being easier to remove during decommissioning. Suction caissons are now used extensively worldwide for anchoring large offshore installations to the seafloor at great depths. Oil and gas recovery at great depth could have been a very difficult task without the suction anchor technology, which was developed and used for the first time in the North Sea 30 years ago. The use of suction caissons/anchors has now become common practice worldwide. Statistics from 2002 revealed that 485 suction caissons had been installed in more than 50 different localities around the world, in depths to about 2000 m. Suction caissons have been installed in most of the deep water oil producing areas around the world: The North Sea, Gulf of Mexico, offshore West Africa, offshore Brazil, West of Shetland, South China Sea, Adriatic Sea and Timor Sea. No reliable statistics has been produced after 2002, but the use of suction caissons is still rising. ==Description== A suction caisson can effectively be described as an upturned bucket that is embedded in the marine sediment. This embedment is either achieved through pushing or by creating a negative pressure inside the caisson skirt: both of these techniques have the effect of securing the caisson into the sea bed. The foundation can also be rapidly removed by reversing the installation process, applying an overpressure inside the caisson skirt. The concept of suction technology was developed for projects where gravity loading is not sufficient for pressing foundation skirts into the ground. The technology was also developed for anchors subject to large tension forces due to waves and stormy weather. The suction caisson technology functions very well in a seabed with soft clays or other low strength sediments. The suction caissons are in many cases easier to install than piles, which must be driven (hammered) into the ground. Mooring lines are usually attached to the side of the suction caisson at the optimal load attachment point, which must be calculated for each caisson. Once installed, the caisson acts much like a short rigid pile and is capable of resisting both lateral and axial loads. Limit equilibrium methods or 3D finite element analyses are used to calculate the holding capacity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Suction caisson」の詳細全文を読む スポンサード リンク
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