Submersible foundation and systems and methods for manufacturing and using the same

Abstract

A precast concrete gravity-base foundation is provided that is both floatable and submersible in water, and is suitable for mounting the shaft of an offshore wind turbine. The foundation comprises a bottom slab, four cylinders positioned at each corner, a centrally located cylinder, and a top slab covering each of the corner cylinders and having a central opening that receives the top portion of the centrally located cylinder. The foundation's configuration and positioning of the corner cylinders provide maximum stability, and once the corner cylinders are filled with sand, stone, or the like, the corner cylinders further bolster the overall mass and stability of the foundation. The foundation is produced on land, rolled onto a submersible jack-up barge, and transported to either a predetermined storage location or an installation site. The foundation's buoyancy and versatile storage options allow contractors to work year-round with fewer ships, cranes, equipment, and workers at the job site, making it a valuable addition to the offshore wind industry.

1 . A method, comprising:
 forming a precast concrete gravity-base foundation for supporting a structure in a body of water, said foundation further comprising a foundation bottom surface and a foundation top surface, each of said foundation bottom surface and said foundation top surface defining multiple outer corners, said foundation further comprising a plurality of hollow cylinders, wherein one of said plurality of hollow cylinders is positioned at each said outer corner, and one of said plurality of hollow cylinders is centrally positioned on said foundation;   positioning said foundation on a floating barge;   transporting said barge and said foundation to a submersion site in a body of water; and   removing said foundation from said barge at said submersion site for storage or service installation of said foundation.   
     
     
         2 . The method of  claim 1 , wherein a top of each of said plurality of hollow cylinders positioned at each said outer corner is closed by said foundation top surface, and wherein said one of said plurality of hollow cylinders centrally positioned on said foundation extends through said foundation top surface. 
     
     
         3 . The method of  claim 2 , wherein each of said foundation top surface and said foundation bottom surface further comprise surface halves that are joined together by a closure pour over a series of steel members embedded in each said half. 
     
     
         4 . The method of  claim 2 , wherein each said outer corner of said foundation top surface and said foundation bottom surface defines a curve, and wherein a portion of an outer wall of each of said plurality of hollow cylinders positioned at each said outer corner is vertically aligned with said curve. 
     
     
         5 . The method of  claim 1 , wherein each said foundation bottom surface further comprises a planar concrete slab with a plurality of unitarily formed concrete ring mats extending upward from a top face of said planar concrete slab, each said concrete ring mat having a ring mat top flat face that receives a bottom flat edge of one of said plurality of hollow cylinders. 
     
     
         6 . The method of  claim 5 , wherein each said concrete ring mat is affixed to one of said plurality of hollow cylinders through a first section of rebar embedded in cement inside of a corrugated metal sleeve positioned inside of said concrete ring mat, and a second section of rebar embedded in an outer wall of one of said plurality of hollow cylinders that attaches to said first section of rebar at a rebar coupler. 
     
     
         7 . The method of  claim 1 , wherein the step of forming a precast concrete gravity-base foundation further comprises the steps of:
 positioning a mandrel on a platform that is moveable across a floor of a production facility;   assembling a rebar cage around said mandrel on said platform;   casting a cylinder about said rebar cage on said platform;   removing said mandrel from said casted cylinder; and   moving said casted cylinder to casted cylinder storage at said production facility.   
     
     
         8 . The method of  claim 7 , wherein said mandrel further comprises a partially collapsible cylindrical mandrel having a first gusset, a second gusset, and a hydraulic cylinder affixed to each of said first gusset and said second gusset and operative to cause said first gusset and said second gusset to partially collapse inward into an interior of said mandrel upon retraction of a piston of said hydraulic cylinder, and further operative to cause said first gusset and said second gusset to form a portion of an outer cylindrical wall of said mandrel upon extension of said piston. 
     
     
         9 . The method of  claim 7 , wherein said step of assembling a rebar cage around said mandrel on said platform further comprises:
 moving said mandrel and said platform to a position between separate halves of a rebar tower;   closing said separate halves of said rebar tower about said mandrel on said platform; and   repeatedly vertically moving a work platform that extends about said mandrel along a height dimension of said mandrel while setting portions of said rebar cage about said mandrel.   
     
     
         10 . The method of  claim 9 , further comprising the steps of:
 opening said separate halves of said rebar tower;   moving said rebar cage and said mandrel on said platform from between said separate halves of said rebar toward to a casting position at said production facility located between separate halves of a concrete casting machine;   closing said separate halves of said concrete casting machine about said rebar cage and said mandrel on said platform to perform said step of casting said cylinder;   opening said separate halves of said concrete casting machine; and   moving said casted cylinder and said platform from between said separate halves of said concrete casting machine on said platform to a mandrel extraction location in said production facility to perform said step of removing said mandrel from said casted cylinder.   
     
     
         11 . The method of  claim 7 , wherein the production facility is adjacent to a body of water, and said floating barge is positioned at a bulkhead immediately adjacent to an exit from said production facility immediately prior to said step of positioning said foundation on said floating barge. 
     
     
         12 . The method of  claim 11 , wherein said floor of said production facility extends from a cylinder casting zone to said exit from said production facility, wherein said casting zone is configured to carry out said steps of (i) positioning the mandrel on the platform, (ii) assembling the rebar cage around said mandrel on said platform; (iiI) casting the cylinder about said rebar cage on said platform; and (iv) removing said mandrel from said casted cylinder. 
     
     
         13 . The method of  claim 12 , said production facility further comprising:
 a cylinder storage zone between said cylinder casting zone and said exit from said production facility, said cylinder storage zone storing a plurality of cylinders cast at said cylinder casting zone;   a foundation assembly zone between said cylinder storage zone and said exit from said production facility; and   a slab assembly zone adjacent to said foundation assembly zone.   
     
     
         14 . The method of  claim 12 , wherein the step of forming a precast concrete gravity-base foundation further comprises the steps of:
 assembling separate halves of said foundation bottom surface to form said foundation bottom surface;   assembling separate halves of said foundation top surface to form said foundation top surface;   positioning said foundation bottom surface on blocking on said floor of said production facility in alignment with said exit of said production facility;   affixing said plurality of hollow cylinders to said bottom slab; and   affixing said foundation top surface to each one of said plurality of hollow cylinders positioned at each said corner.   
     
     
         15 . The method of  claim 14 , wherein said step of positioning said foundation on a floating barge further comprises:
 positioning a plurality of extensible rail carts below said precast concrete gravity-base foundation between said blocking;   extending each of said extensible rail carts to engage a bottom surface of said foundation;   moving said rail carts and said foundation through said exit of said production facility and onto said barge;   retracting each of said extensible rail carts to lower said foundation onto dunnage blocks on a deck of said barge; and   returning said extensible rail carts to said foundation assembly zone.   
     
     
         16 . The method of  claim 1 , wherein said step of removing said foundation from said barge at said submersion site further comprises the steps of:
 submersing said barge and said foundation to a depth at which said barge separates from said foundation and said foundation floats with a portion of said foundation remaining above a surface of the water.   
     
     
         17 . The method of  claim 16 , further comprising the step of moving said submerged barge away from an area underneath of said foundation, and submersing said foundation to a seabed floor at said submersion site. 
     
     
         18 . The method of  claim 17 , wherein said step of submersing said foundation further comprises the step of filling each of said plurality of hollow cylinders positioned at each said outer corner with a sufficient amount of material to reduce a buoyancy of said foundation to cause said foundation to sink to said seabed floor. 
     
     
         19 . The method of  claim 18 , wherein said step of filling each of said plurality of hollow cylinders further comprises pumping sea water into each of said plurality of hollow cylinders positioned at each said outer corner. 
     
     
         20 . The method of  claim 16 , wherein said step of submersing said barge further comprises pumping seawater into an interior of said barge.