Underwater foundation

Abstract

A method of installing an underwater foundation, suitable for use in supporting or anchoring wave or tidal energy capture devices is provided. The method comprises providing a foundation unit ( 1 ) equipped with a submersible drilling rig ( 16 ); placing the foundation unit ( 1 ) on the bed ( 50 ) of a body of water at a selected location; activating the submersible drilling rig ( 16 ) to drill a plurality of pile holes ( 56 ) in the bed of the body of water; and securing the foundation unit ( 1 ) to the bed of the body of water by means of piles ( 54 ) or tendons, inserted in pile holes ( 56 ) and secured to the foundation unit ( 1 ). A foundation unit ( 1 ) and a submersible drilling rig ( 16 ) for use in the method are also provided.

1 . A method of installing an underwater foundation, suitable for use in supporting or anchoring wave or tidal energy capture devices, the method comprising:
 providing a foundation unit equipped with a submersible drilling rig that includes a drill head driver; a drill string magazine, and a transfer device for transferring drill string sections to the drill head drive;   placing said foundation unit on the bed of a body of water at a selected location;   activating said submersible drilling rig to drill a plurality of pile holes in said bed of the body of water; and   securing said foundation unit to the bed of the body of water by means of piles inserted in said pile holes, and secured to said foundation unit;   wherein the drill string sections used when drilling the pile holes, are used to form the piles and the piles are subsequently tensioned.   
     
     
         2 . A method according to  claim 1  wherein the foundation unit has air or gas filled chambers which are filled with water, or a denser filling material than water, when the unit is placed on the bed of the water body. 
     
     
         3 . A method according to  claim 1  further comprising the steps of aligning the foundation unit to a selected attitude. 
     
     
         4 . A method according to  claim 3  wherein the foundation unit is aligned by providing the unit with at least three remotely controlled or automatic jacking devices and operating the jacking devices to align the foundation unit on the bed of a body of water. 
     
     
         5 . A method according to  claim 3  wherein control of alignment makes use of at least one levelling device, which provides feedback on the attitude of the foundation unit to an operator or to an automatic system. 
     
     
         6 . A method according to  claim 1  further comprising the step of interposing a layer of a grouting compound between the base of the foundation unit and the surface of the bed. 
     
     
         7 . A method according to  claim 1  wherein the drilling rig is remotely activated or remotely controlled or automatic in operation. 
     
     
         8 . A method according to  claim 1  wherein the pile holes are drilled to a depth of up to 15 m and have a diameter of 100-150 mm. 
     
     
         9 . A method according to  claim 1  wherein the foundation unit is from 10 to 20 m 2  in area and between 50 and 100 pile holes are drilled. 
     
     
         10 . A method according to  claim 1  wherein forming of each pile is completed by injection of a suitable grouting compound into each pile hole, filling spaces between the drill string and the walls of the hole and optionally filling the drill string sections. 
     
     
         11 . A method according to claim  1  wherein the piles are secured to the foundation unit by means of nut runners screwed down a portion of the pile projecting from the top surface of the foundation unit until they contact the foundation unit and tighten against it. 
     
     
         12 . A foundation unit, for an underwater foundation suitable for use in supporting or anchoring a wave or tidal energy capture device to the bed of a body of water, said unit comprising a submersible drilling rig for drilling a plurality of pile holes in the bed of a body of water, said drilling rig comprising; a drill head driver; a drill string magazine, and a transfer device for transferring drill string sections to the drill head drive from the drill string magazine, wherein drill string sections are used to form piles and the piles are provided with securing and tensioning devices for securing and tensioning them to the foundation unit. 
     
     
         13 . A foundation unit according to  claim 12  wherein the submersible drilling rig is equipped for securing said foundation unit to the bed of the body of water by means of piles inserted in said pile holes and secured to said foundation unit. 
     
     
         14 . A foundation unit according to  claim 12  wherein the submersible drilling rig is a remotely controllable, or automatic, submersible drilling rig. 
     
     
         15 . A foundation unit according to  claim 12  wherein said submersible drilling rig comprises:
 a drill head driver, mounted on at least one extendible mounting arm, said mounting arm turning about a pivot, in use on a said foundation unit, in use of the drilling rig.   
     
     
         16 . A foundation unit according to  claim 12  further comprising air or gas filled chambers, which are filled with water, or a denser filling material than water, when the unit is placed on the bed of the water body. 
     
     
         17 . A foundation unit according to  claim 12  further comprising at least three remotely controlled or automatic lacking devices. 
     
     
         18 . A foundation unit according to  claim 12  further comprising deformable grout retention skirts provided around its periphery, or deformable grout retention tubes provided underneath the base of the unit. 
     
     
         19 . A foundation unit according to  claim 12  further comprising a stub or anchor points for attachment of a wave or tidal energy capture device. 
     
     
         20 . A foundation unit according to  claim 12  further comprising a quick connecting system for attachment of a wave or tidal energy capture device. 
     
     
         21 . A remotely controllable or automatic submersible drilling rig, said drilling rig comprising:
 a drill head drive, mounted on at least one extendible mounting arm, said mounting arm turning about a pivot, in use on a said foundation unit; a drill string magazine, and a transfer device for transferring drill string units to the drill head drive, in use of the drilling rig.   
     
     
         22 . A foundation for use in supporting or anchoring a wave or tidal energy capture device comprising:
 a foundation unit connected by a plurality of piles to the bed of a body of water; wherein the piles are secured and tensioned to the foundation unit by securing and tensioning devices.