Method for manufacturing a gravity based foundation for an offshore installation, and gravity based foundation.

摘要

The invention concerns a gravity based foundation for an offshore installation and a method of its manufacturing. The foundation comprises a caisson of concrete and a hollow shaft. The 5 caisson has a bottom slab, a roof and a side wall extending between the bottom slab and the roof. The caisson is of hollow construction. The roof having a passage for the shaft, the shaft extending with its lower part through the passage into the caisson and is supported on a shaft support provided on the slab. The shaft support has embedded tensioning bars vertically projecting from the upper side of the shaft support. The shaft has a flange at its lower part, 10 which is provided with passages. The shaft is mounted on the shaft support by means of the tensioning bars extending through the bolt passages. The method comprises the steps: — providing a concrete bottom slab, — providing a full-length formwork defining at least part of the shaft support and having a vertical length corresponding to the vertical length of the shaft support, and arranging 15 the full-length formwork onto the bottom slab, — providing a slip formwork defining the side wall and having a vertical height smaller than the vertical length of the full-length formwork, and arranging the slip formwork onto the bottom slab, — providing the tensioning bars and mounting the tensioning bars in a fixed position to 20 the full-length formwork, and — concrete pouring of the side wall and shaft support while raising the slip formwork.