Ballasted driven pile

Abstract

A driven pile anchor suitable for securing a tendon of a tension leg platform to the seafloor is supplemented with added weight. The pile may be a conventional driven friction pile installed with an underwater pile hammer. A load frame is added to the individual pile to accommodate ballast weights. Pre-manufactured ballast weights are placed on the frame to increase the holding power of the pile anchor system. The ballast weights may be secured solely by gravity connections, thereby simplifying their installation. In a second embodiment, the pile is intentionally plugged and installed with the plug intact. Pre-manufactured ballast weights are then placed inside the pile and may be held in place by gravity. In a third embodiment, the pile is a conventional driven friction pile installed with an underwater pile hammer. The pile is initially open but subsequently evacuated and intentionally plugged near its pile tip. Pre-manufactured ballast weights are placed inside the pile to increase its holding capacity. The first embodiment may be practiced in conjunction with either the second or third embodiment. The first embodiment may be retrofitted to existing, driven-pile anchor systems.

1 . A method for installing a driven-pile anchor in the seafloor comprising:
 setting a closed-end, tubular pile in the seafloor;   driving the pile to design penetration depth;   placing one or more pre-manufactured ballast weights in the central cavity of the tubular pile.   
   
   
       2 . A method as recited in  claim 1  wherein the closed-end, tubular pile comprises a metal cap on a first end thereof. 
   
   
       3 . A method as recited in  claim 1  wherein the closed-end, tubular pile comprises a metal partition proximate a first end thereof. 
   
   
       4 . A method as recited in  claim 1  wherein the closed-end, tubular pile comprises a grout plug at a first end thereof. 
   
   
       5 . A method as recited in  claim 1  wherein driving the pile comprises impacting the pile with an underwater, mechanical hammer. 
   
   
       6 . A method as recited in  claim 1  wherein driving the pile comprises jetting. 
   
   
       7 . A method as recited in  claim 1  wherein driving the pile comprises drilling. 
   
   
       8 . A method as recited in  claim 7  wherein the pile comprises a drill bit at a first end thereof. 
   
   
       9 . A method as recited in  claim 8  wherein the drill bit closes a first end of the closed-end pile. 
   
   
       10 . A method as recited in  claim 1  wherein the pre-manufactured ballast weights comprise a lifting padeye at a first end and a recess at an opposing second end sized to receive the lifting padeye of a ballast weight stacked below it within the central cavity of the tubular pile. 
   
   
       11 . A method as recited in  claim 1  wherein the pre-manufactured ballast weights comprise iron ore. 
   
   
       12 . A method as recited in  claim 11  wherein the iron ore comprises hematite. 
   
   
       13 . A method as recited in  claim 1  wherein the pre-manufactured ballast weights comprise concrete. 
   
   
       14 . A method as recited in  claim 13  wherein the concrete is reinforced concrete. 
   
   
       15 . A method as recited in  claim 1  wherein the pre-manufactured ballast weights comprise barite. 
   
   
       16 . A method for installing a driven-pile anchor in the seafloor comprising:
 setting a tubular pile in the seafloor, the pile having a first, lower end and a second, upper end;   driving the pile to design penetration depth;   removing the soil plug from the central cavity of the tubular pile;   setting a plug proximate the first end of the pile;   placing one or more pre-manufactured ballast weights in the central cavity of the tubular pile.   
   
   
       17 . A method as recited in  claim 16  wherein removing the soil plug comprises jetting with a water jet. 
   
   
       18 . A method as recited in  claim 16  wherein removing the soil plug comprises drilling. 
   
   
       19 . A method as recited in  claim 18  wherein removing the soil plug comprises drilling with an auger. 
   
   
       20 . A method as recited in  claim 16  wherein setting a plug comprises setting a grout plug. 
   
   
       21 . A method as recited in  claim 16  wherein the pre-manufactured ballast weights comprise a lifting padeye at a first end and a recess at an opposing second end sized to receive the lifting padeye of a ballast weight stacked below it within the central cavity of the tubular pile. 
   
   
       22 . A method as recited in  claim 16  wherein the pre-manufactured ballast weights comprise iron ore. 
   
   
       23 . A method as recited in  claim 22  wherein the iron ore comprises hematite. 
   
   
       24 . A method as recited in  claim 16  wherein the pre-manufactured ballast weights comprise concrete. 
   
   
       25 . A method as recited in  claim 24  wherein the concrete is reinforced concrete. 
   
   
       26 . A method as recited in  claim 16  wherein the pre-manufactured ballast weights comprise barite. 
   
   
       27 . A method for increasing the pull-out resistance of a pile anchor in the seafloor comprising:
 placing a load frame having a plurality of weight-receiving receptacles on the pile;   inserting pre-manufactured ballast weights in the weight-receiving receptacles.   
   
   
       28 . A method as recited in  claim 27  wherein the pile anchor comprises a tubular pile having a first, lower section of larger diameter and second, upper section of smaller diameter and a shoulder joining the first section and the second section and the load frame is configured to bear against the shoulder. 
   
   
       29 . A method as recited in  claim 27  wherein the weight-receiving receptacles are substantially tubular and the ballast weights are substantially cylindrical. 
   
   
       30 . A method as recited in  claim 29  wherein the ballast weights have a padeye on a first end and a conical or frusto-conical section on an opposing second end. 
   
   
       31 . A method as recited in  claim 30  wherein the ballast weights are placed in the load frame by lowering on a cable attached to the padeye. 
   
   
       32 . A method as recited in  claim 29  wherein the ballast weights comprise a flange proximate the upper end thereof which flange bears against the weight receptacle when the ballast weight is fully inserted in the receptacle. 
   
   
       33 . A method as recited in  claim 32  wherein the flange comprises a beveled lower surface. 
   
   
       34 . A method as recited in  claim 33  wherein the weight receptacle comprises flared upper end configured and sized to engage the beveled lower surface on the flange of the ballast weight. 
   
   
       35 . A method as recited in  claim 27  wherein the pre-manufactured ballast weights comprise iron ore. 
   
   
       36 . A method as recited in  claim 35  wherein the iron ore comprises hematite. 
   
   
       37 . A method as recited in  claim 27  wherein the pre-manufactured ballast weights comprise concrete. 
   
   
       38 . A method as recited in  claim 37  wherein the concrete is reinforced concrete. 
   
   
       39 . A method as recited in  claim 27  wherein the pre-manufactured ballast weights comprise barite. 
   
   
       40 . A method as recited in  claim 27  wherein an upward force applied to the load frame is not transmitted to the pile.