Installation of suction piles underwater

Abstract

Suction failure due to a piping effect when installing a suction pile underwater is mitigated by laying at least one substantially impermeable mat on the seabed. An entrance of a piping channel extending under a skirt of the pile from a seabed location to a suction chamber of the pile is identified. The mat is laid to cover the entrance to restrict or block a flow of water entering the piping channel.

1 - 21 . (canceled) 
     
     
         22 . A method of mitigating suction failure due to a piping or seepage effect when installing a suction pile underwater, the method comprising identifying an entrance of a bypass channel that extends under a skirt of the pile from a seabed location to a suction chamber of the pile, and laying a substantially impermeable mat having a pliant, flexible body at the seabed location to cover the entrance and so restrict or block a flow of water entering the bypass channel, wherein a radially inner side of the mat lies against and extends partially up a side of the skirt. 
     
     
         23 . The method of  claim 22 , wherein the laid mat extends across the seabed beyond the entrance of the bypass channel to define an annular or part-annular peripheral sealing interface between the mat and an underlying area of the seabed around that entrance. 
     
     
         24 . The method of  claim 22 , comprising forcing the laid mat against the seabed under suction applied to the mat via the bypass channel. 
     
     
         25 . The method of  claim 22 , comprising overlapping or abutting two or more mats to cover the entrance of the bypass channel. 
     
     
         26 . The method of  claim 22 , wherein the laid mat conforms pliantly to contours of the seabed. 
     
     
         27 . The method of  claim 22 , comprising abutting the laid mat with the pile. 
     
     
         28 . The method of  claim 22 , comprising suspending suction in response to appearance of the bypass channel and then resuming suction after laying the mat on the seabed. 
     
     
         29 . The method of  claim 22 , comprising storing, transporting and/or lowering the mat to the seabed in a compact configuration and then opening the mat out into a wider and/or longer deployment configuration underwater before laying the mat on the seabed. 
     
     
         30 . The method of  claim 29 , comprising unrolling or unfolding the mat from the compact configuration into the deployment configuration. 
     
     
         31 . The method of  claim 22 , comprising supporting the mat on the pile and deploying the mat from the pile when laying the mat on the seabed. 
     
     
         32 . The method of  claim 31 , comprising deploying the mat from the pile while a portion of the mat remains attached to the pile. 
     
     
         33 . The method of  claim 32 , comprising lowering the mat relative to the pile to a seabed level and then deploying the mat from the pile. 
     
     
         34 . The method of  claim 33 , comprising deploying the mat by pivoting the mat from the pile. 
     
     
         35 . The method of  claim 31 , comprising preliminarily lowering the pile through water toward the seabed with the mat stowed on the pile. 
     
     
         36 . The method of  claim 22 , comprising lifting the mat from the seabed after resuming or completing installation of the pile. 
     
     
         37 . The method of  claim 22 , comprising leaving the mat on the seabed after completing installation of the pile. 
     
     
         38 . The method of  claim 37 , comprising using the mat to mitigate scouring of the seabed during operational use of the pile. 
     
     
         39 . The method of  claim 38 , comprising supporting anti-scour features on the mat, those features being one or more of: dumped rocks; dumped bags of granular material; or fronds upstanding from the mat. 
     
     
         40 . The method of  claim 22 , comprising encircling the pile with the mat or with an array of such mats. 
     
     
         41 . The method of  claim 22 , comprising laying the mat or a plurality of such mats to cover a minor angular segment of the seabed around a central longitudinal axis of the pile.