IE63671B1 - Method for making foundation for a jackable platform and means for carrying out the method - Google Patents

Description

- 2 The present invention relates to a method for making a foundation for a jackable platform on a sea bottom. The platform comprises a preferably buoyant or self-floating deck, and a plurality of legs upon which the deck can be jacked up and/or down, the platform for moving or relocation preferably being floated on the self-floating deck structure such that the deck, when the platform has been installed, is jacked up to a position above the sea surface.

The present invention relates further to a means for making a foundation for a jackable platform of the before-mentioned type.

Existing platforms of the type described above possess inherent limitations in that the platform legs have limited length and strength. If such a platform operates in larger depths than it is built for, the legs must be replaced and/or reinforced by a substantial amount. Such an operation is both time consuming and expensive, since the mountings and/or the jack means on the deck and the deck structure must also be modified.

The present invention proposes to reduce the above-mentioned shortcomings and facilitate a simple adaption of existing jackable platforms for larger depths. According to the present invention there is provided a method of increasing the working depth of a jackable platform, the platform comprising a deck structure and a plurality of legs upon which the deck can be jacked up and/or down, comprising the steps of providing the lower end of at least one leg with one or more downwardly suspended pipe elements before relocation of the platform, the pipe element(s) being movable relative to said leg, and after lowering said leg to bring the pipe element(s) into engagement with the seabed, filling the pipe element(s) wholly or partly with sand, gravel or the like material thereby to form a foundation, said leg being brought to rest on said filling material whereby said leg of the platform is founded on the sea bottom in an elevated position.

The invention also provides a jackable platform having means for providing a foundation for the platform on a sea bottom, which platform comprises a deck structure, and a plurality of legs upon which the deck can be jacked up and/or down, so that when the platform has been installed, the deck can be jacked up to a position above the sea level, wherein the foundation means comprises a pipe element movably suspended at the lower end of at least one of the jackable legs of the platform, the diameter of said pipe element being larger than the cross section of the jackable leg at the bottom of the same.

Upon submersion of the legs the pipe shaped element(s) will contact the sea bottom first and partly penetrate the same. Thereafter gravel or the like is supplied to the internal space in the pipe shaped element or elements up to a predetermined level, whereafter the legs are further lowered until the same rest firmly on the supplied layer of gravel or the like in at least one of the said pipe elements, and/or is being pressed down into the same.

Thereafter the self-floating platform deck is jacked up to a desired level above the sea surface. At least one pipe element can with advantage be suspended on the legs while the platform is located near the shore preferably in a protected area, the platform then being towed out to the installation site with the at least one pipe element suspended on the legs. The said at least one pipe element can for instance be suspended on the legs by means of chains, cables or the like.

The upper and/or lower parts of the pipe elements should be open or at least partly open and the pipe elements can with advantage be conical having a larger lower diameter than upper diameter.

The pipe elements are movably suspended in relation to the platform legs. The pipe elements can further be mutually connected and spaced with reinforcement elements. The lower ends of the pipe elements can further be provided with a penetrating edge or a skirt body which is adapted to be pressed down into the sea bottom.

For further description of the present invention reference is made to the accompanying drawing which shows an embodiment of a platform in accordance with the invention.

The figure shows a jackable platform 5 comprising a buoyant or self-floating deck structure 6, and at least three legs 1. The self-floating deck can in conventional manner be jackable up and/or down on the legs 1, alternatively the legs 1 can be jacked up and/or down relative to the deck structure 6.

The length of the said legs 1 will impose a limitation on the water depth in which the flat platform can operate. In order to increase this depth pipe elements 2 are provided at the lower part of the legs 1 which may be given a cylindrical or conical shape. The pipe elements 2 may be realised in the shape of open, reinforced pipe, for instance made of steel or concrete. The lower part 3 of the pipe elements 2 can be especially adapted in order to obtain a controlled penetration of the sea bottom 6 at the site of location, and they are otherwise designed for constituting a foundation for the legs 1 of the platform.

The foundation is established by locating the pipe elements 2 in a vertical position on the sea bottom, whereafter they are filled and packed with gravel, sand or the like suitably graded material 4 up to a desired level in the pipe element. ί The platform is installed in the following fashion : » The required number of pipe elements are produced ashore and are thereafter submerged and located on the sea bottom on a selected mounting site the pipe elements being positioned with a mutual distance and relationship which corresponds to the mutual distance and relationship of the legs 1 on the platform. The platform 5 is thereafter floated into position above the pipe elements such that the legs are situated straight above each pipe element which are now positioned on the sea bottom. The pipe elements are thereafter attached to the legs in suitable fashion for instance with chains, cables or the like.

Thereafter the legs and thereby also the pipe elements are lifted or jacked up from the bottom. In this position the platform is then towed out to the predetermined operational site, in which site the pipe elements are correctly positioned on the sea bottom by submerging the legs such that the lower ends of the pipe elements arrive in contact with the sea bottom.

The pipe elements are thereafter filled with sand, gravel or the like material. If necessary the filling material is compacted, for instance by moving the legs up and down. In order to facilitate the filling of gravel or the like down into the pipe elements, the platform legs can be released from the pipe elements and jacked up in a suitable degree. ’ The legs are thereafter lowered down onto the foundation whereafter the deck is jacked up to a position above the sea surface. At the bottom ends of the legs can be mounted suitable footings 8 which may be attached to the pipe elements .

When the platform is to be moved or relocated, the method or 5 procedure is reversed. When the pipe elements are lifted up, the gravel or the like will pour out through the lower opening in the pipe elements and remain on the sea bottom.

Claims (9)

1.

2.

3. A method of increasing the working depth of a jackable platform, the platform comprising a deck structure and a plurality of legs upon which the deck can be jacked up and/or down, comprising the steps of providing the lower end of at least one leg with one or more downwardly suspended pipe elements before relocation of the platform, the pipe element(s) being movable relative to said leg, and after lowering said leg to bring the pipe element(s) into engagement with the seabed, filling the pipe element(s) wholly or partly with sand, gravel or the like material thereby to form a foundation, said leg being brought to rest on said filling material whereby said leg of the platform is founded on the sea bottom in an elevated position. A method in accordance with claim 1, wherein at least one pipe element is suspended below a leg by means of chains, wires or the like. A jackable platform having means for providing a foundation for the platform on a sea bottom, which platform comprises a deck structure, and a plurality of legs upon which the deck can be jacked up and/or down, so that when the platform has been installed, the deck can be jacked up to a position above the sea level, wherein the foundation means comprises a pipe element movably suspended at the lower end of at least one of the jackable legs of the platform, the diameter of said pipe element being larger than the cross section of the jackable leg at the bottom of the same.

4. A platform in accordance with claim 3, wherein the or each pipe element is entirely or partly open at the upper and/or lower end thereof.

5. A platform in accordance with claim 3 or 4, wherein the or each pipe element is conical with a larger diameter at the lower end than at the upper end.

6. A platform in accordance with claim 3 to 5, wherein pipe elements are mutually inter connected by means of reinforcing elements.

7. A platform in accordance with claim 3 to 6, wherein the or each pipe element is provided at the lower end thereof with an edge or a skirt body for penetrating the sea bottom.

8. A method of increasing the working depth of a jackable platform substantially as herein described with reference to the accompanying drawing.

9. A jackable platform having means for providing a foundation for the platform on a sea bottom substantially as herein described with reference to the accompanying drawing.