Method for establishing a foundation in a seabed for an offshore facility and the foundation according to the method

摘要

A foundation according to the invention for offshore facilities, preferably at shallow depths, has a substantially bell-shaped bottom part (1) of steel plate with a central cavity (21) and peripheral pressure tight chambers (25) which are separated by bulk-heads (23). The foundation is brought down into seabed or lake bottom (10) consisting of sand. After placing on the bed, according to the invention there is created underpressure in the chambers (25) so that a water current occurs through the bed layer around lower rims (17, 19) of the bottom part. Thereby the bed material is fluidised under the rims (17, 19), and the foundation sinks down into the bed by its dead load. The fluidization may be varied along different parts of the rims (17, 19) by providing different pressures in different chambers (25) whereby the foundation may be righted during the bringing down and thereby compensate for uneven bed etc. By the invention, the use of heavy concrete caissons may be avoided, and allowance is made for environmental demands regarding removal of the foundations after use as the foundation according to the invention weighs considerably less and is easier to remove.