Method and associated apparatus

Abstract

Provided is a method of installing a Gravity Based Structure (GBS). The method involves installing a substructure at a position to be below the GBS, the substructure providing a foundation upon which to support the GBS when installed, and installing the substructure to define at least an annular support region for the GBS. The method further involves installing the GBS above the substructure with the annular support region therebelow, and pre-installing the substructure in advance of the GBS, with the GBS being installed above the substructure subsequent to the substructure's installation.

What is claimed is: 
     
         1 . A method of installing a Gravity Based Structure (GBS), the method comprising;
 installing a substructure at a position to be below the GBS, the substructure providing a foundation upon which to support the GBS when installed, the method comprising installing the substructure to define at least an annular support region for the GBS; and   installing the GBS above the substructure with the annular support region therebelow;   wherein the method comprises pre-installing the substructure in advance of the GBS, with the GBS being installed above the substructure subsequent to the substructure's installation.   
     
     
         2 . The method of  claim 1 , wherein the substructure comprises at least one skirt element, the skirt element comprising a vertically-oriented cylinder with a central longitudinal axis of the cylinder being vertically oriented when installed, each cylinder comprising an open central portion for accommodating foundation material therein when installed. 
     
     
         3 . The method of  claim 2 , wherein the skirt element comprises at least one of: a metal cylinder and a concrete cylinder. 
     
     
         4 . The method of  claim 2 , wherein the substructure comprises a plurality of skirt elements and the method comprises arranging the plurality of skirt elements circumferentially to define the annular support region for the GBS. 
     
     
         5 . The method of  claim 4 , wherein each of the plurality of skirt elements is individually installed, the substructure being installed incrementally. 
     
     
         6 . The method of  claim 4 , wherein the method comprises simultaneously installing the plurality of skirt elements. 
     
     
         7 . The method of  claim 2 , wherein, at least during installation, the skirt element is open at its upper end, the upper end being below the GBS when installed. 
     
     
         8 . The method of  claim 2 , wherein the skirt element is enclosed at an upper end, the upper end being below the GBS when installed. 
     
     
         9 . The method of  claim 8 , wherein the substructure comprises a plurality of skirt elements and each skirt element is enclosed at an upper end by a respective end wall; the method comprising enclosing the skirt element prior to installation of the skirt element. 
     
     
         10 . The method of  claim 8 , wherein the substructure comprises a plurality of skirt elements and the plurality of skirt elements is enclosed at their respective upper ends by a common end wall, the common end wall being configured to correlate to the arrangement of the skirt elements when installed. 
     
     
         11 . The method of  claim 8 , wherein the skirt element is enclosed at the upper end by a concrete end wall. 
     
     
         12 . The method of  claim 1 , wherein the method comprises providing the substructure below the GBS such that the substructure falls within a footprint of the GBS when installed; and wherein a central axis of the substructure is vertically aligned with a central axis of the GBS when installed. 
     
     
         13 . The method of  claim 1 , wherein installing the substructure comprises inserting or lowering the substructure at least partially into the formation below; and
 wherein the method comprises installing the substructure using one or more of: vibration, piling, oscillation, pumping, suction.   
     
     
         14 . The method of  claim 1 , wherein the method comprises:
 transporting the substructure to the location for installation separately from the GBS;   providing a gap between the substructure and the GBS thereabove; and   providing a gravel bed between a top of the substructure and a bottom of the GBS, the gravel bed being applied after installation of the substructure and prior to the installation of the GBS.   
     
     
         15 . The method of  claim 1 , wherein the method comprises connecting the substructure to the GBS subsequent to installing the substructure. 
     
     
         16 . The method of  claim 1 , wherein the substructure effectively comprises one or more stiffeners such that the method comprises providing an improved stiffness of foundation for the GBS, the improved stiffness being relative to the formation prior to the installation of the substructure; and
 wherein the method comprises providing a consistent stiffness of support around at least the annular support region for the GBS, the consistent stiffness of support being provided at least partially by a consistency of stiffness of the substructure.   
     
     
         17 . A substructure for supporting a GBS, the substructure providing a foundation upon which to support the GBS when installed, wherein the substructure comprises at least an annular support region to define an annular support for the GBS when installed; and
 wherein the substructure comprises a pre-installed substructure configured to be installed in advance of the GBS.   
     
     
         18 . The substructure of  claim 17 , wherein the substructure comprises a plurality of substructure elements, the plurality of substructure elements arranged circumferentially when installed to define the annular support region for the GBS; and
 wherein the plurality of substructure elements comprises a plurality of skirt elements, the skirt elements each comprising a vertically-oriented cylinder, with a central longitudinal axis of the cylinder being vertically oriented when installed, each cylinder comprising an open central portion for installation for accommodating foundation material therein when installed;   wherein each skirt element comprises a cylinder, the cylinder being configured for insertion into the formation when installed, such that the open central portion is filled with formation and an upper end of each skirt element is adjacent an upper surface of the formation.   
     
     
         19 . An installation comprising the GBS and the substructure of  claim 17 . 
     
     
         20 . The installation of  claim 19 , comprising a gap between the substructure and the GBS thereabove, the gap comprising a gravel bed between a top of the substructure and a bottom of the GBS.