GB2467842A

GB2467842A - A submerged support structure with adjustable feet secured by piling

Info

Publication number: GB2467842A
Application number: GB1002342A
Authority: GB
Inventors: Peter Leonard Fraenkel
Original assignee: Marine Current Turbines Ltd
Current assignee: Marine Current Turbines Ltd
Priority date: 2009-02-12
Filing date: 2010-02-12
Publication date: 2010-08-18
Anticipated expiration: 2030-02-12
Also published as: JP2012517545A; CN102362033B; AU2010212668A1; GB0902289D0; US20110318113A1; JP2014169621A; CN102362033A; JP5774158B2; GB201002342D0; GB2467842B; EP2396474A1; JP5572638B2; WO2010092351A1; NZ594528A; NZ618105A; RU2543835C2; KR20110124277A; RU2011137438A; CA2752288A1; CL2011001954A1

Abstract

The invention relates to a method of installing a support structure 2 required to be installed in a sea or river bed SB, involving constructing the support structure in such a manner that it is capable of being temporarily self standing on the sea or river bed prior to and throughout operations required to permanently anchor the support structure to the sea or river bed. The structure may comprise a number of adjustable support structure foot units 5 adapted to receive and locate piles (23 figure 6) which are sunk into the sea bed. Each foot unit may be adjustable such that the support structure can be set to the required level orientation relative to the seabed. The piles may be grouted in place with cementicious material.

Description

S

INSTALLING SUBMERGED SUPPORT STRUCTURES

BACKGROUND OF THE INVENTION

This invention relates to the installation of seabed (or river bed) mounted support structures that generally project above the surface of the sea (or river).

A possible application for such support structures is for the support of wind or water current driven turbines, or wave energy powered devices.

In particular the present invention relates to methods of construction of support structures and to the installation for such support structures regardless of their purpose.

Although said support structures will generally project above the surface of the sea or river in which the support structure is installed, the upper part of the support structure may be removed if desired after installation has been completed so that in such cases the remainder of the support structure i.e. a so-called fixed component may be left completely submerged.

It has been found that when providing mounting support structures, for example, for 1 5 submerged off-shore seabed mounted turbine installations a major difficulty in connection with such installatios resides in the time required for installing such an installation in that the present modes of installation involves the use of large installation vessels such as a crane-barge or jack-up barge to be present on site to complete foundation works. In practice such vessels are necessary to position the structure but lengthy installation times for such vessels not only result in very high costs per installation but also reduce the numbers of installations a given vessel can complete in a given time.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide methods of installing and the construction of support structures capable of being installed in the sea or in a river bed that generally project above the surface of the sea or river regardless of their intended purpose but which are generally intended for the support of wind or water current driven turbines, or wave energy powered devices.

It is a particular object of the invention to provide means whereby such support structures can be installed even under adverse conditions such as where there is the likelihood of strong currents or waves, with reduced attendance required for the installation vessel.

STATEMENTS OF THE INVENTION

According to a first aspect of the invention there is provided a method of installing a support structure required to be installed in a sea or river bed, involving so constructing the support structure that is capable of being temporarily self standing on the sea or river bed prior to and throughout the carrying out of operations required permanently to anchor the support structure to the sea or river bed.

Conveniently the support structure is in the form of an elongate column for supporting a submergeable water driven turbine and/or a wind driven turbine.

Preferably the installing of the support structure including the step of anchoring the structure to the sea or river bed by means of piles or similar anchoring means Preferably the support structure incorporates a plurality of anchoring positions for 1 5 cooperation with support structure support foot units, and wherein each said foot unit is adapted to receive and locate a support structure anchoring pile or like means which is driven/sunk into the sea or river bed by means supported from the support structure for enabling the handling and sinking of the piles or like means.

Conveniently the elongate column like support structure is designed so that it can be lowered to the sea or river bed and positionally adjusted to allow for any lack of flatness of the sea or river bed by adjusting the position of each individual bed engaging foot, prior to the sinking of the associated pile.

If considered necessary the method can include the step of adding additional weight to the structure In the event that the support structure during the being moved by currents, waves or wind so as to maintain installation period of the its installation is at the risk of being in insufficient frictional contact with the sea or river bed during the installation process.

A further aspect of the invention provides a support structure capable of being installed in a sea or river bed, wherein the structure is arranged to be sufficiently heavy as to be temporarily self standing on the sea or river bed by being heavy enough to be held in position by friction with the seabed, and wherein said structure incorporates a plurality of anchoring positions for cooperation with positionally adjustable sea or river bed engaging support feet units with each said unit being adapted to receive and locate a support structure anchoring pile which is driven/sunk into the sea or river bed by means supported from the support structure for enabling the handling and sinking of the piles.

In a preferred construction a temporary additional structure can be provided at the top of the support structure, for mounting/housing facilities for carrying out any operations required to sink the piles being used toi anchor the support structure to a sea or river bed.

In accordance with an further aspect of the invention there is provided a support structure capable of being installed in the sea or river bed, wherein the support structure is constructed as to be self installable structure in that it is temporarily self standing 1 5 throughout operations required permanently to anchor the support structure to the sea or river bed.

In accordance with a further aspect of the invention there is provided a support structure for installation on a sea or river bed including a plurality of anchoring positions provided with support structure support feet units, means adapted to receive and locate a predetermined number of support structure anchoring piles, and means supported from the support structure for enabling the handling and sinking of piles such that serve to anchor the support structure to the sea or river bed.

In a preferred construction each said foot unit is associated with a adjustment means for enabling the positioning of a pile in its anchoring position to be selectively adjusted.

In a preferred arrangement the support structure incorporates a facility for enabling the installation of piles serving permanently secure the support structure to the sea or river bed, in such manner as to allow support structure installation vessel involved with the installation of the support structure to leave the region of installation as soon as the support structure is positioned correctly with required pile handling equipment mounted upon it.

Conveniently, the necessary equipment may be installed ashore so that the entire self-installing support structure can be quickly lowered into the desired location whereby the delivery vessel may leave the site.

According to a still further aspect of the present invention, there is provided a jacket type support structure with at least one footing assembly on which the support structure can stand securely on the sea or river bed with the upper part of the support structure tall enough to project above the water surface.

Conveniently, in situations where it is desirable for the final support structure to be submerged, a removable upper part may be fitted which projects above the surface for the installation phase for the support structure phase and which following the installation phase is subsequently removable.

Conveniently the upper part is removed using a crane mounted upon a boat.

1 5 In a preferred construction the support structure is provided with three or four footing assemblies.

Preferably, the support structure is designed so that it can be lowered to the sea or river bed, levelled to allow for the lack of flatness of the sea or river bed to enable each footing assembly to be fixed to the sea or river bed by drilling through each such assembly, the insertion of pin-piles and the grouting said pin piles in place.

Conveniently the drilling process is carried out from a temporary structure mounted on top of the jacket of ajacket type support structure.

In the event that the support structure during the installation period of the its installation is at the risk of being moved by currents, waves or wind extra weight may be added to the temporary structure to maintain sufficient friction with the sea or river bed during the installation process, and wherein the extra weight may be removed together with the installation equipment after anchoring pin-piles have been installed so the support structure can no longer displace relative to the sea or river bed.

From the above it will be noted that the invention provides a structure capable of being installed in the sea (or in a river), which is designed to be temporarily self standing by being heavy enough to be held in position by friction with the seabed and which has facilities to support equipment needed to permanently affix it to the sea (or river) bed using pin-piles or other fixtures capable of penetrating the sea (or river) bed through tubular permanent footings integral with the jacket structure. If necessary extra weight to generate sufficient friction to prevent movement may be temporarily provided as ballast added to the structure and removed after the pin-piling operation has been completed.

Thus there is provided a structure with a jacketed base having one or more permanent tubular footings which can be drilled through from a platform mounted above water level into the sea or river bed, and into which pin-piles may be inserted and grouted into place.

In particular the structure includes temporary footings that can be adjusted for height and alignment to permit the structure to be levelled before fixing to the sea or river bed, the force for so doing being provided by hydraulic jacks, screw jacks or any other such 1 5 appropriate mechanisms.

Conveniently said temporary adjustable footings may be attached either in board or outboard of the permanent footings of the jacket or concentric with the permanent footings Conveniently the structure has provision for conductor tubes to be positioned and aligned between the above water surface platform or superstructure and tubular permanent footings close to sea level, such that a drill string can be deployed from a drilling rig on the superstructure through the conductor tube and the tubular footings so as to drill a hole for foundation pin-piles or alternatively to hammer apin pile into the seabed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how to carry the same into effect reference will now be made to the accompanying drawings in which:-Figure 1 schematically illustrates the general construction of a support jacket structure involving the concepts of the invention; Figures 2A, 2B, 2C and 20 respectively illustrate to a larger scale the features of the construction of support feet involved with the structure shown in Figure 1; Figure 3A schematically illustrates a first positioning of the support feet of the structure shown in Figure 1 relative to a sea or river bed; Figure 3B schematically illustrates a further possible positioning of the support feet of the structure shown in Figure 1 relative to a sea or river bed; and Figures 4 to 10 schematically illustrate successive stages in anchoring the support jacket structure of Figure 1 to a sea or river bed using pin piles.

DETAILED DESCRIPTION OF THE DRAWINGS

1 0 Referring now to Figure 1 the support structure 1 illustrated therein includes a jacket structure 2 including an upstanding monolithic column like main body 3 supported by a support leg assembly 4 formed by four similar support foot units 5 which are equiangularly disposed around the column 3. Each foot unit 5 includes a central tubular structure formed by an inner tube SA and an outer tube SB to be considered in detail herein after 1 5 and a sea or river bed engaging foot 7 that is connected with the outer tube 5B. The outer tube forms part of the assembly 4 that is itself connected to the main body 3 of the structure 2 by way of a generally horizontal member 8 connecting with the lower end region 9 of the main body 3 of the structure 2 and an inclined member 10 connecting with the main body 3 of the structure 2 at a location above the associated horizontal member 8.

Each sea/river bed engaging foot is mounted to the lower end of the tube 58 by way of a pivotal connection arrangement 1]. that allows the foot 7 to be raised or lowered relative to the outer tube SB as required to co-operate with the profile of the sea or river bed region upon which the foot 7 is required to rest. The arrangement of the concentric tubes can be regarded as the anchorage footings for the jacket structure.

The connection arrangement 11 is such that the foot 7 is able to tilt relative to the inner tube 5A so as to be angularly disposable relative to the vertical axis of the central structure of the associated support foot structure 5 The foot 7 is also axially displaceable up and down relative to the assembly 4 thereby facilitating acceptable co-operation between the

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foot 7 and the adjacent sea or river bed SB in such manner as to enable support adjustments to be effected to ensure that the main body 3 of the jacket structure 2 is level with the body vertical.

Since it is intended that the jacket structure 2 should be firmly and securely anchored to the sea or river bed SB the support leg assemblies 4 and the support structures 6 are intended to be secured to the sea or river bed.

In the embodiment illustrated it is intended that the structure 2 is to be anchored to the sea or river bed by pin piles (not shown in Figure 1) that are positionally located by the support foot units 5.

In other words the foot units 5 have an essentially dual purpose of which one serves to provide firm support to the jacket strucrture2 during its initial installation i.e., during a positioning and anchoring process and the second of which is to facilitate the insertion of the pin piles.

For the purposes of the jacket positioning and anchoring stages of the installation 1 5 processes the upper part of the jacket mounts a temporary superstructure 12 such that the latter is located above the water level WI.

The superstructure 12 may carry means such as a crane or other forming of lifting and positioning means 13 for handling the pin piles and other elements that are required during the positioning and anchoring stages of the support structure 1. These elements can comprise a drilling rig, pile driving apparatus together with the various elements of equipment associated with hole drilling and the positioning and lowering of the pin piles.

The super structure 12 can additionally serve to receive any additional weights 14 that are considered necessary to hold the jacket in its required position during its installation that is to ensure the friction with the sea or river bed SB during installation remains effective to prevent any movement under the influence of currents waves and/or wind.

In relation to the position and anchoring of the structure 2 a further important feature which is illustrated by Figure 1 is the provision of a conductor tube 15 shown in the process of being positioned by the crane 13 to engage with the top of one of the inner tubes 5A of the foot units 5. This conductor tube 15 is intended to be clamped or held in position at the top of the inner 5A in order to provide guidance and protection during drilling and pin pile installation and grouting, as will be described hereinafter with the help of further Figures of the drawings.

It is important to note that generally in practice the conductor tube 15 will be lowered into position and guided by wire cables (not shown) attached to the top of the jacket foot unit inner tube 5A and threaded through a pair of eye bofts' (not shown) near the base of the conductor tube 15. In this way the cables will guide the conductor tube 15 accurately into position.

The mechanisms for effecting such adjustment will be described in more detail herein after and may not necessarily be positioned as shown in the Figures of this Application. It should be noted that the jacket structure 2 can mount/carry other forms of structure to that as shown. For example, a lattice framework or a multiplicity of vertical columns.

Reference will now be made to Figures 2A -2D which illustrate the construction of the feet 1 5 units S in greater detail and to a larger size.

In particular these Figures 2A -2D show as has been previously mentioned that the adjustable feet units 5 may be used for levelling the structure 1 after it has been lowered by a crane-barge or other transport vessel to the sea (or river) bed SB. In the embodiment used to illustrate the principles involved it can be seen that there are two hydraulic rams or jacks 16 provided upon each foot unit 5 that can be operated from above the surface either together or differentially so as to raise or lower the foot 7 or to incline it at an angle.

The Figures 2A-2D illustrate how both vertical and angular adjustment may be obtained and then fixed by pressurising the rams or jacks 16. The upper ends 17 of the rams or jacks 16 are pivotally connected to a bracket 18 mounted to the leg unit outer tube SB whilst the lower ends 19 of the rams or jacks are pivotally connected to the inner tube 5A connected to the associated leg unit foot 7.

As may be noted from Figures 2A and 2B differential operation of the rams or jacks 16 appropriately tilts the associated leg unit foot 7. The tilt is schematically indicated by the tilt angle indication arrows TA.

As may be seen from Figures 2C and 2D the rams or jacks 16 can be operated to raise or lower the leg unit foot 7 relative to the remainder of the leg unit 5. The vertical adjustment is schematically indicated by the arrows VA.

It will be understood that tilting can be combined with the height adjustment as is enabled by the construction of the leg assembly.

In practice, other forms of adjustment may be used such as screw jacks (either electrically or hydraulically activated), inflatable bags (inflated with liquid or gas) or indeed any convenient device capable of applying the necessary forces may be used. If necessary more than two such rams or jacks 16 may be provided so as to share the loads. It will be shown that said lifting or jacking devices only require to be functional for the duration of the installation process and may either be abandoned (i.e. sacrificial) or recovered for re-use on other projects afterwards.

Referring now to Figures 3A and 3B these Figures 3 illustrate how the adjustable foot units need not necessarily be located at positions concentric with the footings 5D of the 1 5 support structure 2 the case of Figure 2. As can be seen from Figures 3A and 3B the foot units S can either be mounted on footings 5D located within the spread of the assembly 4 as shown in Figure 3A or they can be mounted on outrigger structures outside the foot units 5 as shown in Figure 3B. The former arrangement is considered to be more economical with materials while the latter is possibly more stable as a structure. By positioning the adjustable foot units 5 separately from the jacket structure footings 5D moe space is made available for the drilling and pin-pile installation and additionally this arrangement simplifies the structure of the footings.

It will be noted that in the embodiments shown in Figures 3A and 38 the foot units S are effectively totally separate from the arrangement of Figure 1 in which the tubes 5A and SB form footings for the structure and which are additionally intended to receive the conductor 15. In the case of the embodiments of Figures 3A and 3B the foot units 5 each incorporate an inner element SE depending from the associated horizontal bar 11 and an concentric outer tubular element SF.

Referring now to Figures 4 to 10 which disclose successive stages in the anchoring of a jacket support structure 2 as shown in the previous Figures by means of pin piles. Thus Figure 4 illustrates a first stage in the procedure for permanently fixing the jacket footings to the sea (or river) bed (SB) Whilst Figure 4 represents by way of example an embodiment in which the adjustable feet units 5 are concentric with the footings SB of the support structure 1. It should be noted that since as explained in the previous paragraph said adjustable foot units 5 may also be employed separately from the jacket structure 2 in which case they would not be visible n Figure 4.

Thus Figure 4 in fact illustrates the stage at which the conductor tube 15 has been lowered into the inner tube 5A of the tubular structure of the jacket foot unit 5 until its tower end rests on the sea (or river) bed. SB Once in this position it is clamped at the top end (not shown in Figure 4) to the temporary superstructure 12 (not shown in Figure 4).

Figure 5 illustrates how a drill string 21 can be lowered through the thus positioned conductor tube 15 and driven by a drilling rig (not illustrated in Figure 1 or 5) but mounted on the superstructure 12 located above the conductor tube 15. Whilst, normally a rotary drill 22 will be used, it is also possible to hammer drive a pile (not shown) through the conductor tube 15 tube into the sea bed SB if the ground conditions of the sea or river bed are suitable. The hammer (not shown) can be dropped through the conductor tube 15.

Cuttings arising from such operations can be flushed out using water pumped through the drill string but this is not illustrated.

Figure 6 shows how, after the drilling operation is completed, a pin-pile 23 can be lowered through the conductor tube 5 suspended on a cable 24. Said cable also carries grout hoses which are not illustrated but which are necessary for subsequent operations yet to be described.

Cementitious grout may be be pumped through grout hoses (not shown) attached to the pin pile 23 which guide the cementitious material into and through bores (not shown) within the pin pile so as to emerge from the base of the pin pile thereby to fill the concentric void arising from the drilling between the pin-pile and the drilled seabed with a grout infilling. Sufficient grout is pumped into the void so as completely to fill the void to the level of the seabed SB as is schematically illustrated at 25 in Figure 7.

Completion of this grout filing operation can be confirmed using a sensor or sensors at seabed level (not illustrated) which will react to the emergence of grout 15 from below.

Figure 8 shows that after the grout injected through the pin-pile to form the grout filling 25 has set, the conductor 15 is lifted a short distance until it is only engaged with the jacket inner tube SA by a small amount, sufficient to hold it in place despite currents or waves. In the Figure the lower end of the conductor 15 is indicated at 26 The small mount may be of the order of 200 or 300mm but other levels, of engagement may be used to Suit the conditions.

Figure 9 shows how more grout can then either be injected through grout hoses connected to drillings (not shown) in the top part of the pin-pile or directly into the annular void between the pin-pile 24 and the interior of the footing inner tube 5A. This annular void is filled with cementitious grout 26 until it reaches the level of the base of the conductor tube 15. This level can be calculated from the volume of grout needed to fill a space of known i 5 dimensions or sensors can be used to detect when the correct level is reached.

The hoses and lowering cable 24 are then disconnected from the pin pile 23 and raised back to the superstructure work platform 12 on top of the structure. The separation of hoses and cables can be accomplished by various means which are not illustrated. For example the couplings can be split and held together by a pin which can be withdrawn by either pulling a cable from above the surface of the sea or energising an electrical solenoid, by divers or Remotely Operated Vehicles (ROVs) may also be used to undertake the disconnection. There are also a number or proprietary products specially designed to permit remote controlled separation of cable and hose connections which may be used for this purpose.

Figure 10 shows the completed footing after the conductor tube 15 and all cables and hoses have been detached. It can be seen that the pin-pile 23 is now securely grouted into both the ground and the footing tube and provides a means to carry much larger shear or up-lift forces between the structure and the seabed. The surface area of the pin-pile is designed to be sufficient to carry the loads at low enough stress levels to avoid delamination of the grout.

At this stage the adjustable feet 7 are either abandoned and left in situ or provision maybe made to detach and remove them for reuse. Finally the temporary superstructure 12, the crane 13 and associated equipment, the conductor tube(s) 15 and any other tools, together with any ballast 14 added for stability during drilling can be removed by a vessel with a crane. A smaller and less costly vessel may be used for this purpose than the one needs to bring and position the entire jacket structure 2. The second vessel may also bring other equipment needed for completion of the installation, such as wind or tidal turbines, above surface housings or decks, etc. Alternatively if the jacket structure 2 is required to be entirely submerged a detachable upper portion may at this stage be removed or replaced io with specialised equipment.

From the above it will be noted that the proposals of the invention provides a structure capable of being installed in the sea (or in a river), which is designed to be temporarily self standing by being heavy enough to be held in position by friction with the seabed and which has facilities to support the equipment needed to permanently affix it to the sea (or 1 river) bed using pin-piles or other fixtures capable of penetrating the sea (or river) bed through tubular permanent footings integral with the jacket structure. If necessary extra weight to generate sufficient friction to prevent movement may be temporarily provided as ballast added to the structure and removed after the pin-piling operation has been completed.

In particular the structure includes temporary footings that can be adjusted for height and alignment to permit the structure to be levelled before fixing to the seabed, the force for so doing being provided by hydraulic jacks, screw jacks or any other such appropriate mechanisms.

Claims

CLAIMS1. A method of installing a support structure required to be installed in a sea or river bed, involving so constructing the support structure that is capable of being temporarily self standing on the sea or river bed prior to and throughout the carrying out of operations required permanently to anchor the support structure to the sea or river bed.
2. A method as claimed in claim 1, in which the structure is in the form of an elongate column for supporting a submergeable water driven turbine and/ora wind driven turbine.
3. A method as claimed in claim 1 or 2, and including the step of anchoring the structure to the sea or river bed by means of piles or similar anchoring means
4. A method as claimed in claim 3, and wherein the support structure incorporates a plurality of anchoring positions for cooperation with support structure support foot units, and wherein each said foot unit is adapted to receive and locate a support structure anchoring pile or like means which is driven/sunk into the sea or river bed by means supported from the support structure for enabling the handling and sinking of the piles or like means.
5. A method as claimed in claim 4, and wherein each said foot unit is positionally adjustable relative the sea or river bed in such manner that the support structure can be set to a required level and orientation relative to the sea or river bed.
6. A method as claimed in claim 5, wherein the support structure is designed so that it can be lowered to the sea or river bed, levelled by the adjustment means to allow for any lack of flatness of the sea or river bed by adjusting the position of each individual bed engaging foot, prior to the sinking of the associated pile.
7. A method as claimed in claim 5 or 6,, and including the step of grouting with cementicious material each individual pile in the position into which it has been inserted.
8. A method as claimed in any one of the preceding claims 4 to 8,and including the provision of a temporary structure provided at the top of the support structure, and wherein the operations required to sink the piles is carried Out from the temporary structure..
9. A method as claimed in claim 1, and including the step of adding additional weight to the structure In the event that the support structure during the g moved by currents, waves or wind so as to maintain installation period of the its installation is at the risk of being in insufficient frictional contact with the sea or river bed during the installation process.
10. A method as claimed in claim 9, and including the step of removing after the anchoring piles have been installed any additional weight together with any equipment involved in installation of the support structure such that the support structure can no longer displace relative to the sea or river bed.
11. A support structure capable of being installed in a sea or river bed, wherein the structure is arranged to be sufficiently heavy as to be temporarily self standing on the sea 1 5 or river bed by being heavy enough to be held in position by friction with the seabed, and wherein said structure incorporates a plurality of anchoring positions for cooperation with positionally adjustab'e sea or river bed engaging support feet units with each said unit being adapted to receive and locate a support structure anchoring pile which is driven/sunk into the sea or river bed by means supported from the support structure for enabling the handling and sinking of the piles.
12. A support structure as claimed in claim 11, wherein the structure is in the form of an elongate column for supporting a submergeable turbine.
13. A support structure as claimed in claim 10 or 11, and including a temporary additional structure at the top of the support structure, and wherein facilities are provided at the temporary structure for carrying out any operations required to sink the piles.
14. A support structure as claimed in claim 13, wherein the temporary structure is arranged to be able to carry additional weight whereby in the event that the support structure during the installation thereof is at the risk of being moved by currents, waves or wind so as to maintain sufficient friction with the sea or river bed during the installation process appropriate additional weight can be the added to the temporary to maintain acceptable friction of the support structure with the sea or river bed.
15. A support structure as claim 11, and including temporary footings that can be adjusted for height and alignment to permit the structure to be levelled before fixing to the sea or river bed, the force for so doing being provided by hydraulic jacks, screw jacks or any other such component.
16. A method of installing a support structure required to be installed in a sea or river bed substantially as herein before described with reference to the accompanying drawings.
17. A support structure capable of being installed in a sea or river bed substantially as herein before described with reference to the accompanying drawings.