Template for and method of installing a plurality of foundation elements in an underwater ground formation

Abstract

A template for use in installing a plurality of foundation elements, in particular anchor piles, relative to one another in an underwater ground formation is provided. The template includes a plurality of guides for the foundation elements, which guides are fixed relative to one another by means of a frame. At least one of the guides includes a sound-insulating sleeve for surrounding a foundation element during driving.

Claims

1. A removable, reusable template for use in installing a plurality of foundation elements relative to one another in an underwater ground formation, comprising a plurality of guides for the foundation elements, wherein the guides are fixed relative to one another by a frame, wherein at least one of the guides comprises a sound-insulating double wall construction sleeve having at least one air chamber configured to render the template buoyant, the sleeve configured to surround a foundation element during driving, and wherein the guides are configured to be placed on the underwater ground formation during use, the sound-insulating sleeve being tubular, and extending upwardly and surrounding the foundation element from the underwater ground formation to above the water level.

2. The template according to claim 1, wherein all of the guides comprise a sound-insulating sleeve, said sleeves extending parallel to each other.

3. The template according to claim 1, wherein the sleeve is movable from one guide to another guide.

4. The template according to claim 1, comprising three guides.

5. The template according to claim 1, wherein a wall of the sleeve is made of a composite material.

6. The template according to claim 1, wherein the sleeve comprises one or more guide elements on its inner wall.

7. The template according to claim 6, wherein the one or more guide elements are at least near the bottom of the sleeve and in its upper half of the sleeve.

8. The template according to claim 6, wherein the one or more guide elements comprise a noise damping material.

9. The template according to claim 1, wherein sleeve reduces the noise input from the driving by at least 10 dB.

10. The template according to claim 1, wherein the sleeve reduces the noise input from the driving by at least 15 dB for frequencies lower than 1000 Hz.

11. The template according to claim 1, wherein the buoyancy of the template is at least 60%.

12. The template according to claim 1, wherein the buoyancy of the template is at least 80%.

13. The template of claim 6, wherein the guide elements are axially separated from each other so as to provide a guide length to guide the foundation element during driving.

14. The template of claim 1, wherein the sleeve is configured to stand erect and have an inner wall spaced apart from the foundation element during driving.

15. A method of installing a plurality of foundation elements, relative to one another in an underwater ground formation, comprising: placing a template comprising a plurality of guides for the foundation elements and at least one tubular sound-insulating sleeve having a double wall construction on the underwater ground formation, the sound-insulating sleeve engaging the underwater ground formation and supporting itself upon the underwater ground formation so as to extend upwardly and surround the foundation element from the underwater ground formation to above a water level, next inserting a foundation element into the at least one sound-insulating sleeve and driving the foundation element into the underwater ground formation, lifting the template over ends of the installed foundation elements extending above the underwater ground formation, placing a jacket over the ends of the installed foundation elements and securing the jacket to the foundation elements; wherein, at least during driving, the at least one sound-insulating sleeve fully surrounds the foundation element with the double wall construction from the underwater ground formation to above the water level.

16. The method according to claim 15, wherein all of the guides comprise a sound-insulating sleeve and a foundation element is placed in each of the sleeves and driven into the underwater ground formation.

17. The method according to claim 15, wherein, after driving a first foundation element into the underwater ground formation, the sleeve is moved to another guide or the template is rotated and placed with another of the guides over the installed foundation element and a second foundation element is placed in the sleeve and driven into the underwater ground formation.

18. The method according to claim 15, wherein, at least during driving, the clearance between the foundation element and the sleeve is in excess of 30 cm.

19. The method according to claim 15, wherein water is removed from the sleeve such that, at least during part of driving, at least a driver is separated from an inner wall of the sleeve by air.

20. The template according to claim 1, wherein the outer diameter of the sleeve is smaller than the inner diameter of the at least one of the guides.

21. The method according to claim 15, wherein the outer diameter of the at least one sound-insulating sleeve is smaller than the inner diameters of the plurality of guides.

22. A removable, re-usable template for use in installing a plurality of foundation elements relative to one another in an underwater ground formation, comprising: a plurality of guides for the foundation elements, wherein the guides are fixed relative to one another by a frame, wherein at least one of the guides comprises a sound-insulating sleeve configured to surround a foundation element during driving, and wherein the guides are configured to be removably placed on the underwater ground formation during use, the sound-insulating sleeve engaging the underwater ground formation and having a double wall cylinder construction supporting itself upon the underwater ground formation so as to extend upwardly and surround the foundation element from the underwater ground formation to above the water level, the double wall construction comprising at least one chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a system for installing a foundation element comprising a first template according to the present invention.

(2) FIG. 2 is perspective view of a tripod installed by means of a template according to the present invention.

(3) FIG. 3 is a perspective view of a second template according to the present invention.

(4) FIG. 4 is a schematic illustration of a pile having guide elements.

(5) It is noted that the Figures are schematic in nature and that details, which are not necessary for understanding the present invention, may have been omitted.

DETAILED DESCRIPTION

(6) FIG. 1 shows a system for installing a jacket 1 in an underwater ground formation, e.g. a seabed 2, by means of anchor piles 3. In this example, the jacket 1 comprises a central cylinder 4 and a plurality of hollow cylindrical support members or feet 5 connected to the central cylinder 4 by means of a frame 6 and arranged in a pattern, i.c. a triangle (when seen from the top). The central cylinder has a circular cross-section, a diameter of five meters, and is intended to serve, after installation of the jacket on the seabed, as the foundation of a wind turbine. The anchor piles 3 have a circular cross-section, an outer diameter of two meters and a length of 50 meters.

(7) The system further comprises an hydraulic driver 7, e.g. an IHC Hydrohammer S-500 or S-800, connected to a power pack on board of a surface vessel, such as a jack-up barge or floating barge 8. The driver 7 comprises a driver sleeve 9 for securely mounting the driver 7 on an anchor pile 3 and an anvil (hidden from view by the driver sleeve) for transmitting impact energy from the driver 7 to the anchor pile 3. The barge 8 comprises a crane (not shown) to lift and manipulate the anchor piles, the driver, the jacket, et cetera.

(8) The system further comprises a template 10 for positioning and driving a plurality of anchor piles in the seabed in a predetermined pattern corresponding that of the support members of the jacket. The template comprises a plurality of guides 11 for the piles which guides are fixed relative to each other by means of a frame 12. In the embodiment shown in FIG. 1, each guide 11 comprises a sound-insulating sleeve 11A, made of e.g. steel, for surrounding a pile during driving to reduce noise input from the driver into the surrounding water. The pattern of the centrelines of the sleeves corresponds to that of the support members of the jacket, i.e. in this example the sleeves are arranged in a triangle.

(9) Each sleeve has a circular cross-section, is double walled, and has an inner diameter of three meters. The double wall provides one or more chambers for air or a porous material and renders the template buoyant at least to some extent.

(10) In general, to reduce or substantially avoid excessive penetration of the template into the seabed under its own weight and to facilitate removal of the template after the anchor piles have been installed, it is preferred that buoyancy, i.e. the weight of the displaced water, is at least 60% preferably at least 80% of the weight of the template. In an embodiment, buoyancy is variable, e.g. through a system of valves, compressors or pumps, and (ballast) chambers that enable letting in and expelling water.

(11) The inner wall of the sleeve is provided with a plurality of guide elements (hidden from view), in this example two sets of guide wheels made of a noise damping material, such as rubber, and arranged in a ring along the (inner) circumference of the sleeve, both near its bottom and somewhere in its upper half, in this example at a few meters from it upper rim. Separating the sets of guide elements in the axial direction provides a substantial guiding length and thus further increases stability of the piles during driving.

(12) In general, it is preferred that, once the template is in place, the sound-insulating sleeves extend from the ground formation to above the water level. The upper rim of each of the sleeves can be provided with a detachable extender, to adjust the effective length of sleeve to the depth of the water at the location where the foundation elements are to be installed.

(13) Installation of a jacket is carried out for instance as follows. The template is lifted from the deck of the barge and lowered into the sea until it rests in a vertical position on the seabed. Alternatively, the template is afloat or resting on the seabed near the barge and the template is lifted and/or towed to the envisaged site from there. Once in place, each of the anchor piles is lifted over the template and lowered into one of the sleeves and onto the seabed and, if required by the circumstances, allowed to penetrate the seabed to some extent under its own weight.

(14) Then, the driver is lifted from the deck of the barge and placed on top of the first anchor pile and this pile is driven into the seabed to a depth which corresponds to, e.g., 95% of its length, with the upper end of the anchor pile extending typically from 1 to 6 meter above the seabed. During part of the driving the driver is inside the sleeve and, if the sleeve is flooded, under water. When driving of the first anchor pile is completed, the driver is lifted, removed from the first sleeve, and placed onto the second anchor pile. This process is repeated until all anchor piles are installed in the seabed.

(15) Subsequently, the driver is placed back on deck and the template is lifted and either placed on deck or rendered buoyant, e.g. by emptying ballast chambers, and left afloat or placed aside on the seabed. In the latter two instances, the template needs to be lifted only a few meters, i.e. just high enough to safely clear the upper ends of the installed anchor piles.

(16) With the template now out of the way, the jacket is placed with its support members over the anchor piles and secured to the same, e.g. by grouting or welding, and the installation of the jacket is completed, as shown in FIG. 2.

(17) FIG. 3 is a perspective view of a second template 10 according to the present invention comprising a plurality of guides, i.c. hollow cylinders 11 having flared ends, and a single sleeve 11A. The sleeve 11A is in most respects identical to the sleeve described above, except that it is removable from the guides. To this end, the outer diameter of the sleeve 11A is slightly smaller than the inner diameter of the cylinders 11.

(18) After the first pile has been installed, the sleeve is lifted over the end of the installed pile and moved to the next position. At this position, a second pile is placed in the sleeve and driven into the seabed. This process is repeated until all anchor piles are installed in the seabed. Placing and securing the jacket is performed in the way as described above.

(19) It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

(20) The invention is not restricted to the embodiment described above and can be varied in numerous ways within the scope of the claims.