METHOD FOR EXECUTING GRAVITY OFFSHORE STRUCTURE AND THE STRUCTURE

摘要

In constructing a gravity offshore structure at an installation site having a relatively large depth of water, a footing (2) serving as a float as well is built in a dry-dock, and a cylinder (4) which constitutes an underwater substructure is built on the footing (2) in an offshore yard located at a shallow sea area. The cylinder (4) is assembled in a telescopic manner, and an upper cylinder (4C) serves as a float. Ballast water Wb is injected into the footing (2) at the installation site of a large depth of water to submerge the footing (2), and a lower cylinder is extended while the upper cylinder (4C) acts as a float. After the footing reaches the bottom of the water, a pad material is filled in the footing (2) and the cylinder (4), and an offshore superstructure is constructed on the upper portion of the cylinder (4). Since a cylindrical-shaped underwater substructure is built in a telescopic manner on the footing serving as a float as well, a structure for a large depth of water can be built with easy stability as a float even in a region where it is not possible to ensure a calm sea area of a large depth along the coast. Buoyancy and gravity are harnessed at an installation site having a large depth of water to readily extend a body and submerge a huge structure without the use of a large-scale drive apparatus.