Apparatus for controlling erosion of a seabed

Abstract

An apparatus 100 for controlling erosion of a seabed surrounding a pile or subsea foundation comprising a collar member 102 defining an internal space (104); and a web member coupled to the collar member. The web member occupies or at least partially overlays the internal space. The web member comprises: a support structure including a plurality of support elements 108; and a plurality of frond lines 110 interconnecting the plurality of support elements. Each frond line comprises an elongate anchor line (112, fig 4) and a plurality of buoyant elements (114, fig 4) extending transversely from the elongate anchor line. The support structure comprises: a main portion (116, fig 5) occupying or at least partially overlaying at least a peripheral region of the internal space; and a predetermined failure portion 118. The breaking force of the support structure in the predetermined failure portion is less than the breaking force of the support structure in the main portion.

Description

The present invention relates to an apparatus for controlling erosion of a seabed surrounding a pile or subsea foundation and a method of deploying the same. Subsea structures, such as foundation piles, can be subject to significant erosion or scour, in which flow around the structure removes sediment. This may result in the creation of scour pits in the surrounding seabed, which risks compromising the stability and integrity of the subsea structure. Current methodologies for prevention of scour include the application of a rock barrier or rock armour. This may include application of an initial campaign of small-grade rock armour, through which the foundation pile is driven during installation. Following pile installation, a secondary campaign of large grade rock is then subsequently applied. However, the rock armour is itself subject to edge scour. This may result in the development of scour pits, which overtime may result in the collapse of the rock armour. Consequently replacement, or supplementation, of the rock armour is typically required every 2 to 3 years. In addition, this method of scour protection is mostly undertaken postinstallation (i.e. once the foundation pile has been driven into the seabed). It may be a number of weeks between pile installation and application of the secondary campaign or rock armour, with separate vessels required for pile installation and rock armour application. Scour pits may develop in this time. It is an objective of the present invention to provide a more permanent solution to the problem of scour around subsea structures, such as foundation piles. According to a first aspect of the invention, there is provided an apparatus for controlling erosion of a seabed surrounding a pile or subsea foundation, the apparatus comprising: a collar member defining an internal space; and a web member coupled to the collar member, the web member occupying or at least partially overlaying the internal space, wherein the web member comprises: a support structure including a plurality of support elements; and a plurality of frond lines interconnecting the plurality of support elements, wherein each frond line comprises an elongate anchor line and a plurality of buoyant elements extending transversely from the elongate anchor line; wherein the support structure comprises: a main portion occupying or at least partially overlaying at least a peripheral region of the internal space; and a predetermined failure portion (for example a predetermined failure section, region or area, a predetermined failure line or a predetermined failure point), wherein the breaking force of the support structure in the predetermined failure portion is less than the breaking force of the support structure in the main portion, such that as a pile or subsea foundation passes (for example is driven) through the internal space of the collar member the predetermined failure portion preferentially fails to allow the pile or subsea foundation to pass through the web member. In some embodiments each support element comprises a webbing strap. In some embodiments the plurality of support elements include radial support elements, extending inwardly from the collar member towards a substantially central region of the internal space. In some embodiments the breaking force of the support elements in the predetermined failure portion is less than the breaking force of the support elements in the main portion. In some embodiments the breaking force of the support elements in the predetermined failure portion is 50% or less of the breaking force of the support elements in the main portion. In some embodiments the predetermined failure portion is a predetermined failure point comprising a connection point between support elements. In some embodiments each frond line of the plurality of frond lines extends between radial support elements of the plurality of support elements. In some embodiments frond lines are arranged as substantially parallel rows between adjacent radial support elements. In some embodiments the rows of frond lines are spaced by between 100mm and 400mm. In some embodiments the apparatus further comprises a plurality of arms, rotatably coupled to the collar member, each of the plurality of arms being rotatable between a first, deployment, position and a second, operational, position. In some embodiments in the operational position the plurality of arms are substantially coplanar with the collar member, and in the deployment position the plurality of arms are angled with respect to the plane of the collar member. In some embodiments each arm of the plurality of arms comprises a stop or restraint that prevents the corresponding arm from rotating through an angle of 90 degrees or more with respect to the plane of the collar member when rotating from the operational position to the deployment position. In some embodiments each arm of the plurality of arms comprises a first end rotatably coupled to the collar member and a second end distal from the collar member, and wherein each arm of the plurality of arms comprises connection means located at its second end for connection to lifting means. In some embodiments the apparatus further comprises a further plurality of frond lines extending between adjacent arms of the plurality of arms. According to a second aspect of the invention, there is provided a kit of parts for controlling erosion of a seabed surrounding a pile or subsea foundation, the kit comprising: an apparatus according to the first aspect of the invention; and a pile or subsea foundation of predetermined diameter. According to a third aspect of the invention, there is provided a method of deploying an apparatus for controlling erosion of a seabed surrounding a pile or subsea foundation: providing an apparatus according to the first aspect of the invention; and lowering the apparatus to a seabed such that the internal space of the collar member is positioned at the target location for a pile or subsea foundation installation operation. In some embodiments the apparatus is lowered to the seabed with the plurality of arms in the first, deployment, position, wherein once positioned on the seabed the plurality of arms rotate from the first, deployment, position, to the second, operational, position. According to a fourth aspect of the invention, there is provided a method of installing a pile or subsea foundation in a seabed, the method comprising: deploying an apparatus according to the first aspect of the invention using the method of the third aspect of the invention, performing a pile or subsea foundation installation operation, the pile or subsea foundation installation operation comprising driving or traversing a pile or subsea foundation through the internal space of the collar member and into the underlying seabed. As used herein, reference to a pile or subsea foundation may include monopiles, foundation piles (for providing foundation for an above-water structure), jacket piles, suction piles, gravity based structures and other types of seabed foundations. As used herein, a ‘collar member’ refers to a band or frame that extends around, and defines, an internal space. Preferably the collar member is substantially annular in profile or has a profile approximating an annular shape, for example a hexagonal or octagonal shape. The collar member may be constructed from a number of connected frame elements connected in series - for example six elongate frame elements consecutively connected at their ends to form a hexagonal collar. It would be understood that ‘radial’ and ‘circumferential’ directions with respect to a non-annular collar member may refer to the annular shape to which the collar member approximates or to a circular portion of the internal space defined therein. As used herein, ‘a plane of the collar member’ refers to an axial plane across the profile of the collar member. As an example, in use, a pile is driven through the internal space of the collar member in a direction normal to the axial plane of the collar member. As used herein, the term buoyant is given relative to naturally occurring expanses of water - for example seas, oceans and the like. Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 illustrates a perspective view of an apparatus for controlling erosion of a seabed. The apparatus is shown in a deployment position; Figure 2 illustrates a plan view of the collar member of the apparatus of Figure 1; Figure 3 illustrates the plan view of Figure 1, further including a support structure; Figure 4 illustrates a plan view of a frond line; Figure 5 illustrates the plan view of Figure 3, further including a predetermined failure section; Figure 6 illustrates a support element with a predetermined failure section; Figure 7 illustrates a plan view of the apparatus of Figure 1 in an operational position; Figures 8 to 10 illustrate includes a piling operation through the apparatus of Figure 1; Figure 11 illustrates a deployment operation for the apparatus of Figure 1; Figure 12 illustrates a plan view of a support structure with a predetermined failure line; and Figure 13 illustrates a plan view of a collar member including a predetermined failure point. In the drawings like reference numerals refer to like parts. An apparatus for controlling erosion of a seabed surrounding a pile or subsea foundation is described herein. Figure 1 illustrates an example apparatus 100. The apparatus 100 includes a collar member 102 defining an internal space 104. The collar member 102 is shown in isolation in Figure 2. In this example the collar member 102 provides a rigid frame made, for example, from steel. In the example of Figure 1 the collar member 102 is a regular hexagon in profile, having a perimeter formed of six sides. The collar 102 is sized so that the internal space 104 is sufficiently large so as to allow a pile or subsea foundation (of predetermined size) to pass therethrough. For example, the minimal effective diameter of the internal space 104, which in this case is the internal spacing between parallel sides of the hexagonal collar member 102, may be equal to the diameter of the pile plus an additional factor of safety. The factor of safety may account for at least the installation tolerance of the pile. A further arbitrary contingency distance may also be included within the factor of safety according to operator specification. Typical pile outer-diameters may be, for example, between 6m and 13m. Taking this lower-bound as an example, the diameter of the internal space 104 may be 8m in total, which includes 6m accounting for the pile outer-diameter, 1m installation tolerance and an additional 1m contingency distance. In this manner, a pile can pass through the internal space 104 without contacting the collar framework. A pile diameter 106 is shown in Figure 2. The apparatus 100 further includes a web member coupled to the collar member 102, the web member occupying or at least partially overlaying the internal space 104. The web member includes a support structure including a plurality of support elements or tether lines 108. The collar member 102 and support structure are shown in Figure 3. In this example the plurality of support elements 108 are radial support elements, extending inwardly from the collar member 102 towards a substantially central region of the internal space 104. In this example, the radial support elements 108 each extend across the entire cross-section of the internal space 104. That is, each radial support element 108 is attached to the collar member 102 at a first point, extends across the crosssection of the internal space 104, and is connected to the collar member 102 at a second point at an opposing side of the collar member 102 to the first point. In this example each support element 108 includes at least one section of flexible webbing strap. The webbing strap may include a woven fabric strip, although other suitable materials and structures may also be used. In this example the webbing strap is a polyester yarn of lifting / lashing grade. The web member further includes a plurality of frond lines 110 interconnecting the plurality of support elements 108. The frond lines 110 are supported by the support elements 108. An example frond line 110 is shown in Figure 4. Each frond line 110 includes an elongate anchor line 112 and a plurality of buoyant elements 114 (otherwise termed ‘fronds’ or ‘artificial seagrass’) extending transversely from the elongate anchor line 112. In this example the buoyant elements 114 include polypropylene, having a specific gravity of between approximately 0.905 and 0.91, although other suitable materials may be used. In this example the buoyant elements have a length of approximately 1250mm with a width of approximately 50mm, although other dimensions or a range of dimensions may be used. Each frond line 110 may include in excess of 100 buoyant elements per metre. For example, each frond line 110 may include between 100 and 200 buoyant elements per metre - 128 for example. Due to their buoyancy, the buoyant elements 114 assume a naturally upright position when the apparatus 100 is deployed subsea. Put another way the buoyant elements 114 extend transversely in a common direction from the anchor element 112. In doing so, the buoyant elements 114 create a viscous drag barrier that significantly reduces current velocity. The action of reducing current velocity immediately prevents seabed sediment in the immediate area of the frond lines from being scoured out and causes sediment transported across the fronded area to fall into, and collect, within the buoyant elements 114. In this example, the anchor lines 112 include flexible webbing straps. The flexible webbing straps may be superposed or folded over, with the ends of the buoyant elements 114 gripped between the superposed straps. In this example, each frond line 110 extends between radial support elements 108. Between adjacent radial support elements 108, frond lines 110 are arranged as substantially parallel rows. In the illustrated example these rows are parallel with the segment of the collar member 102 that passes between the adjacent radial support elements 108. This results in a ‘spiders-web’-like arrangement with radial support elements crossed with circumferential frond lines. The frond lines 110 are attached or connected to the support element 108 at cross-over positions. This connection may be by knotting during initial assembly. For example a frond line 110 may be fed through a loop present on a corresponding support element 108 at the cross-over point. The support element 108 may then itself be fed back through the loop, retaining the frond line 110 with respect to the support element 108. This process is then repeated for each loop along the length of each support element 108. Other means of attachment are also possible. It would be understood that with the arrangement shown, a single frond line 110 may cross-over each radial support element 108. Alternatively, each circumferential frond ring may include any number of frond lines 110 joined in series between radial support elements 108. The support structure includes a main portion 116 occupying or at least partially overlaying at least a peripheral region of the internal space 104. The support structure further includes a predetermined failure portion 118. The portions 116, 118 are shown in Figure 5 without frond lines 110 for clarity. In this example, the predetermined failure portion 118 is a predetermined failure section or area. The predetermined failure section is substantially central within the internal space 104 and surrounded by the main portion 116, the main portion 116 occupying the remainder of the internal space outside of the failure portion 118. In this example, the breaking force of the support structure in the predetermined failure portion 118 is less than the breaking force of the support structure in the main portion 116. In this example, the predetermined failure portion 118 is a region in which the breaking force of the support elements 108 is less than the breaking force of the support elements 108 in the main portion 116. In this example, the difference in breaking force of the support elements 108 in the main portion 116 and the support elements 108 in the predetermined failure portion 118 is achieved using support elements formed of discrete sections. For example, each radial support element 108 may include webbing straps 1081 having a first breaking force in the main portion 116 and webbing straps IO82 having a second, different, breaking force in the predetermined failure portion 118. These discrete sections may be combined into a single, continuous, webbing strap, for example through sewing as shown in Figure 6. The webbing straps in the main portion 116 and predetermined failure portion 118 may differ in at least one of material, thickness, width or weave. In general, the breaking force of the support elements 108 in the predetermined failure portion 118 is 50% or less of the breaking force of the support elements 108 in the main portion 116. Aptly, the breaking force of the support elements 108 in the predetermined failure portion 118 is 35% or less of the breaking force of the support elements 108 in the main portion 116. Aptly, the breaking force of the support elements 108 in the predetermined failure portion 118 is between 30% and 5% of the breaking force of the support elements 108 in the main portion 116. As an example, the webbing strap used in the main portion 116 may have a breaking force of approximately 6 tonne or more, whereas the webbing strap used in the predetermined failure portion 118 may have a breaking force of approximately 1 tonne. Figures 8 to 10 illustrate the use of the apparatus 100 with a driven pile 200 - that is, the pile 200 is installed through repeated impacts from a driving means, for example a piledriving hammer. As the pile 200 is driven through the internal space 104 of the collar 102 the predetermined failure portion 118 preferentially fails to allow the pile to pass through the web member. That is, the pile 200 applies a force to the web member, substantially perpendicular to the plane of the collar member 104. The flexible support members 108 are loaded in tension until the breaking force in the predetermined failure portion 118 is reached. The predetermined failure portion 118 acts as a sacrificial or ‘weak-link’ region that allows the pile to pass through the apparatus 100 unimpeded. This solution will compile all scour protection works for a pile before it has been installed and eliminates additional work post-installation. It is a concurrent activity that does not affect the design / fabrication or project timeline of the pile installation. That is, as the pile is installed it necessarily becomes protected from scour without additional mitigation works. In this example the coverage of the internal space 104 provided by the frond lines 110 is sufficient so that no matter where the pile is driven within the collar member 102, the edge of the pile engages with frond lines 110. As such, scour protection is provided right up to the pile surface. More specifically, the rows of frond lines 110 extend inwardly along the corresponding radial support elements 108 towards a central region of the internal space 104. If any gap exists between the centre point of the internal space 104 and the innermost rows of radial support elements 108, this distance is less than the radius of the pile. For example, the frond lines 110 may occupy all or most of the main section 116. In this example the rows of frond lines 110 are spaced by between approximately 100mm and 200mm, aptly approximately 150mm. This spacing is less than for known frond mats, within which frond lines may be spaced by approximately 300mm, for example. This minimises the space between the pile and the adjacent frond lines 110 post-installation accounting for the high hydrodynamic forces found at the pile interface. That is, the system allows for fronds to be abutted against the pile with a denser tuft of fronds created at the pile interface. This is shown best in Figures 9 and 10, where the pile interface region is labelled as 115. In use, the apparatus 100 is lowered to a seabed in a predetermined location, such that the internal space 104 of the collar member 102 is positioned at the target location for a pile installation operation. The apparatus 100 may be lowered with any suitable lifting means. For example the apparatus 100 may be lowered using a crane coupled to the apparatus 100 via a winching element, lifting sling or the like (as shown in Figure 11). Once deployed any attachments between the apparatus 100 and the lifting means are released, for example using an ROV. The pile can then be driven through the internal space 104 of the collar member 102 and into the underlying seabed using known methods of pile driving. More specifically, the pile is driven through the internal space 104, through the support web and into the underlying seabed. In this example the apparatus 100 includes a plurality of arms 120, rotatably coupled to the collar member 102. Each arm 120 includes a first end rotatably coupled to the collar member 102 and a second end distal from the collar member 102. Each arm 120 may be attached to the collar member 102 via a hinge or the like. In this example there are six arms 120, each positioned at a corner of the collar member 120. In this example the apparatus 100 includes a further plurality of frond lines 210 extending between adjacent arms 120 (as best shown in Figure 7). By utilising the space between the adjacent arms 120, the overall frond coverage of the apparatus 100 can be increased. In this example the further plurality of frond lines 210 are arranged as substantially parallel rows. The spacing between these rows may be, for example, 300mm. Additional weighting may be provided outwardly of the outermost row of further frond lines 210 (i.e. the row of frond lines 210 positioned closest to the second end of the corresponding arm 120). This weighting may include aggregate filled tubes or the like. In use, the additional weighting may ensure the apparatus 100 remains in-situ and also aids deployment of the arms into an operational position as described below. Each of the plurality of arms 120 is rotatable between a first, deployment, position (as shown in Figure 1) and a second, operational, position (as shown in Figure 7). In the operational position the plurality of arms 120 are substantially coplanar with the collar member 102. That is, with the collar member 102 positioned on the seabed, the arms 120 extend from the collar member 102 along the seabed. In the operational position the second end of each arm 120 is directed away from the collar member 102. In the operational position the arms 120 provide stability to the apparatus 100. In the deployment position the plurality of arms 120 are angled with respect to the plane of the collar member 102. That is, the arms 120 are not parallel with respect to the plane of the collar member 102 but extend from the collar member 102 at an angle therefrom. In this example, the arms 120 extend from the collar member 102 in a generally perpendicular direction with respect to the plane of the collar member 102. In general, the arms 120 each extend from the collar member 102 at the same angle. In this example each arm 120 includes connection means located at its second end for connection to lifting means. For example a lifting eye may be positioned at the second end of each arm 120 for connection to the winching element or lifting sling. In this manner the apparatus 100 may be lowered via a six-legged lifting sling attached to the eye, for example. In use, the apparatus 100 is lowered to the seabed with the arms 120 in the deployment position (see Figure 11). A secondary installation collar or frame may be used for lowering the system to the seabed. Once positioned on the seabed, the arms 120 can then rotated to their operational position. By configuring the apparatus 100 with both deployment and operational positions, the apparatus 100 is easier to transport. In addition, by folding the arms 120 away during deployment the cross-section of the apparatus 100 is minimised, which ensures the apparatus 100 can be quickly and accurately placed on the seafloor. In some examples, each of the plurality of arms 120 includes a stop or restraint that prevents the corresponding arm 120 from rotating through an angle of 90 degrees or more with respect to the plane of the collar member 102 when rotating from the operational position to the deployment position. This stop or restraint may be built into the hinged connection between the arm 120 and the collar member 102 or may be a separate element. In use, the stop or restraint allows the arms 120 to easily move from their deployment position to their operational position with little, or no, operator input. That is, in the deployment position the centre of mass of each arm 120 remains outside the collar member 102. As such, once the lifting means are disconnected from the arms 120, the arms 120 will fall to their operational position due to gravity. This allows the apparatus 100 to be deployed and taken to an operational position with a single lift. In this example each arm 120 has a length that may be approximately equal to the diameter of the pile and may be up to three times to the diameter of the pile, preferably one to two times the diameter of the pile. This ensures considerable frond coverage surrounding the pile without causing significant issues with apparatus transit and lifting. Various modifications to the detailed arrangements as described above are possible. For example, although a driven pile is described above the apparatus may be used with any of monopiles, foundations pile, jacket piles, suction piles, gravity based structures and other types of seabed foundations. As an alternative (or an addition) to the predetermined failure section 118, the support structure may include at least one predetermined failure point 122 (as shown in Figure 13) or at least one predetermined failure line 124 (as shown in Figure 12). As illustrated, these may be substantially central within the internal space. The predetermined failure line 124 may include a connection line between support elements 108. For example, in the illustrated example, the radial support elements 108 extend to a generally central position within the internal space 104 and are connected via the failure line 124. The failure line 124 may, for example, be a webbing strap. Specifically the webbing strap may be the same as webbing strap IO82 described in previous examples. The predetermined failure line 124 may be passed through loops at the end of the support elements 108 or conversely the loops may be constructed around the failure line 124. The predetermined failure point 122 may include a connection point between support elements 108. For example, in the illustrated example, the radial support elements 108 extend to a central position within the internal space 104 where they are connected via the failure point 122. This failure point 122 may, for example, be a shear pin or the like. In this case, as a pile is driven through the internal space 104 of the collar member 102 the predetermined failure point(s) 122 preferentially fails to allow the pile to pass through the web member. In general, the breaking force of the predetermined failure point 122 may be 50% or less of the breaking force of the support elements 108 in the main section 116. Aptly, the breaking force of the predetermined failure point 122 is 35% or less of the breaking force of the support elements 108 in the main section 116. Aptly, the breaking force of the predetermined failure point 122 is between 30% and 5% of the breaking force of the support elements 108 in the main section 116. It will be clear to a person skilled in the art that features described in relation to any of the embodiments described above can be applicable interchangeably between the different embodiments. The embodiments described above are examples to illustrate various features of the invention. Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, compounds, chemical moieties or groups described in 5 conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at 10 least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 15

Claims

1. An apparatus for controlling erosion of a seabed surrounding a pile or subsea foundation, the apparatus comprising:a collar member defining an internal space; anda web member coupled to the collar member, the web member occupying or at least partially overlaying the internal space, wherein the web member comprises:a support structure including a plurality of support elements; anda plurality of frond lines interconnecting the plurality of support elements, wherein each frond line comprises an elongate anchor line and a plurality of buoyant elements extending transversely from the elongate anchor line;wherein the support structure comprises:a main portion occupying or at least partially overlaying at least a peripheral region of the internal space; anda predetermined failure portion, wherein the breaking force of the support structure in the predetermined failure portion is less than the breaking force of the support structure in the main portion, such that as a pile or subsea foundation passes through the internal space of the collar member the predetermined failure portion preferentially fails to allow the pile or subsea foundation to pass through the web member.

2. An apparatus according to claim 1, wherein each support element comprises a webbing strap.

3. An apparatus according to any preceding claim, wherein the plurality of support elements include radial support elements, extending inwardly from the collar member towards a substantially central region of the internal space.

4. An apparatus according to any preceding claim, wherein the breaking force of the support elements in the predetermined failure portion is less than the breaking force of the support elements in the main portion.

5. An apparatus according to claim 4, wherein the breaking force of the support elements in the predetermined failure portion is 50% or less of the breaking force of the support elements in the main portion.

6. An apparatus according to any of claims 1 to 3, wherein the predetermined failure portion is a predetermined failure point comprising a connection point between support elements.

7. An apparatus according to claim 3, wherein each frond line of the plurality of frond lines extends between radial support elements of the plurality of support elements.

8. An apparatus according to claim 7, wherein frond lines are arranged as substantially parallel rows between adjacent radial support elements.

9. An apparatus according to claim 7, wherein the rows of frond lines are spaced by between 100mm and 400mm.

10. An apparatus according to any preceding claim, wherein the apparatus further comprises a plurality of arms, rotatably coupled to the collar member, each of the plurality of arms being rotatable between a first, deployment, position and a second, operational, position.

11. An apparatus according to claim 10,wherein in the operational position the plurality of arms are substantially coplanar with the collar member, andwherein in the deployment position the plurality of arms are angled with respect to the plane of the collar member.

12. An apparatus according to claim 11, wherein each arm of the plurality of arms comprises a stop or restraint that prevents the corresponding arm from rotating through an angle of 90 degrees or more with respect to the plane of the collar member when rotating from the operational position to the deployment position.

13. An apparatus according to any of claims 10 to 12, wherein each arm of the plurality of arms comprises a first end rotatably coupled to the collar member and a second end distal from the collar member, and wherein each arm of the plurality of arms comprises connection means located at its second end for connection to lifting means.

14. An apparatus according to any of claims 10 to 13, wherein the apparatus further comprises a further plurality of frond lines extending between adjacent arms of the plurality of arms.

15. A kit of parts for controlling erosion of a seabed surrounding a pile or subsea foundation, the kit comprising:an apparatus according to any preceding claim; and a pile or subsea foundation of predetermined diameter.

16. A method of deploying an apparatus for controlling erosion of a seabed surrounding a pile or subsea foundation:providing an apparatus according to any of claims 1 to 14; andlowering the apparatus to a seabed such that the internal space of the collar member is positioned at the target location for a pile or subsea foundation installation operation.

17. A method according to claim 16, wherein the apparatus provided is the apparatus of any of claim 10 to claim 14, wherein the apparatus is lowered to the seabed with the plurality of arms in the first, deployment, position, wherein once positioned on the seabed the plurality of arms rotate from the first, deployment, position, to the second, operational, position.

18. A method of installing a pile or subsea foundation into a seabed, the method comprising:deploying an apparatus according to any of claims 1 to 14 using the method of claim 16,performing a pile or subsea foundation installation operation, the pile or subsea foundation installation operation comprising driving or traversing a pile or subsea foundation through the internal space of the collar member and into the underlying seabed.

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