NL2017059B1 - Scour protector and method of arranging a scour protector on a seabed - Google Patents

Abstract

The present invention relates to a scour protector, comprising one or more than one mattress, having a state wherein said mattress is configured to float on water. Said mattress preferably comprises a compartment with at least one inlet opening, wherein said compartment is fillable with a filling medium. The mattress may comprise an accommodation dimensioned to accommodate a subsea structure in a sunken state of said mattress. The invention further relates to a method of arranging a scour protector on a seabed, comprising the steps of: floating at least one mattress on the sea surface; and sinking the at least one mattress into the sea. The mattress may be arranged in its floating state near a subsea structure, especially a monopile, that partly extends above the sea surface, wherein the part of the subsea structure that extends above the sea surface is accommodated in an accommodation of said mattress.

Description

Patent center

The Netherlands

(21) Application number: 2017059 © Application submitted: 28/06/2016 © 2017059

BI PATENT (51) Int. CL:

E02B 3/12 (2016.01) E02B 17/00 (2017.01)

© Application registered: 05/01/2018 © Patent holder (s): Pile fabrics gmbh in NETTETAL, © Request published: Germany, DE. AG Industries B.V. in Beek. © Patent granted: 05/01/2018 © Inventor (s): Herbert Fenkes in Schwalmtal (DE). Edwin Hendrik Theodoor Maria Peters © Patent issued: 26/01/2018 in Beek. © Authorized representative: ir. P.J. Hylarides et al. In The Hague.

© Scour protector and method of arranging a scour protector on a seabed © The present invention relates to a scour protector, including one or more than one mattress, having a state said mattress is configured to float on water. Said mattress preferably comprises a compartment with at least one inlet opening, said said compartment is fillable with a filling medium. The mattress may comprise an accommodation dimensioned to accommodate a subsea structure in a sunken state of said mattress.

The invention further relates to a method of arranging a scour protector on a seabed, including the steps or: floating at least one mattress on the sea surface; and sinking at least one mattress into the sea. The mattress may be arranged in its floating state near a subsea structure, especially a monopile, that partly extends above the sea surface, the part of the subsea structure that extends above the sea surface is accommodated in an accommodation or said mattress.

NL BI 2017059

This patent has been granted regardless of the attached result of the research into the state of the art and written opinion. The patent corresponds to the documents originally submitted.

Scour protector and method of arranging a scour protector on a seabed

The present invention relates to a scour protector and a method of arranging a scour protector on a seabed.

Scour is the removal by hydrodynamic forces or granular bed material in the vicinity of coastal structures, and is a specific form of the more general term erosion. Scour occurs whenever the hydrodynamic bottom shear stresses exceed the sediment critical shear stress, and is therefore typically present in fast running waters with granular soil.

Scour imposes a significant problem for subsea structures, such as monopiles, jackets and also pipelines that are arranged on the seabed, where the scour takes place on the downstream side.

For vertical piles, a hole with a depth to about twice the pile diameter may result. For pipelines lying on the seabed, the scour can lead to partial burial of these pipelines. The scour can lead to a partial burial of these pipelines, and the problems are caused when a differential scour takes place due to different soil types, possibly leaving a pipeline tension a gap.

Scour is normally prevented by the arrangement of large numbers or heavy rocks, preferably or different size, near a subsea structure. These heavy rocks must be transported to the desired location at sea, which is a logistic challenge.

Considering rocks may be arranged around a monopile foundation, this may be difficult for foundations or other types. For example, for a tripod or tri-pile foundation, it is difficult to arrange protection in the form of heavy rocks. After all, the tripod or tri-pile foundation encloses an area between the three piles where it is difficult to arrange heavy rocks.

An object of the present invention is to provide scour protection, that is improved relative to the prior art and that is least one of the above stated problems is obviated.

Such objectives as indicated above, and / or other benefits or inventive effects, are attained according to the present disclosure by the assembly of features in the appended independent device claim and in the appended independent method claim.

Said object is achieved with the scour protector according to the present invention, including one or more than one mattress, having a state said said mattress is configured to float on water.

Said object is furthermore achieved with the method of arranging a scour protector on a seabed according to the present invention, including the steps of floating at least one mattress on the sea surface, and sinking the least one mattress into the sea.

In the following description preferred out of the present invention are further elucidated with reference to the drawing, in which:

Figure 1 is a perspective view of a monopile or a wind turbine, where a scour protector is arranged on the seabed;

Figure 2 is a side view of a monopile or a wind turbine that experiences scour;

Figure 3 is a side view of a monopile or a wind turbine that is provided with a scour protector according to the invention;

Figures 4 and 5 show cross-sectional side views of successive steps or providing and floating a mattress or a scour protector on the sea surface next to a monopile;

Figure 6 shows a top view of a scour protector according to the present invention;

Figures 7 and 8 show cross-sectional side views or successive steps of sinking (figure 7) a scour protector, and arranging said scour protector on the seabed (figure 8);

Figure 9 shows a cross-sectional side view of a scour protector after being arranged on the seabed;

Figure 10 shows three successive steps how the situation or Figure 9 is obtained after some time;

Figure 11 shows a cross-sectional side view of a mattress or the scour protector according to the present invention;

Figure 12 shows a further preferred embodiment of the top surface of the mattress or the scour protector is provided with a various or outlet opening; and

Figures 13-15 show cross-sectional side views or successive steps or arranging a scour protector according to an alternative embodiment on a seabed.

The scour protector 1 according to the invention, comprises one or more than one mattress 2, and has a state said said mattress 2 is configured to float on water (figure 5). In this floating state, the one or more than one mattress 2 may be arranged at a desired position, and possibly connected to further mattresses 2.

In figure 1, a scour protector 1 including four connected mattresses 2 is arranged on the seabed 66 and around a subsea structure 50. The subsea structure 50 is a monopile 52 that supports a wind turbine 54. Said monopile has a cable guide 56 through which and electricity cable 58 is guided to the seabed 66. And electricity cable 58 is, similar to a pipeline, also vulnerable to scour, and may be protected by a further scour protector 1 '. For the sake of simplicity, the further scour protector 1 'shown in figure 1 comprises a single mattress 2, but the skilled person will understand that multiple mattresses 2 may be connected with each other and form a chain of mattresses 2 that may be arranged over an electricity cable 58 or a (not shown) pipeline.

When the scour protector 1 is arranged on the seabed 66 as shown in figure 1, it provides protection against scour, so that a scour hole 66 as shown in figure 2 may be prevented. Over time, the scour protector 1 will experience a small-scale scour effect near its edges 8, and because the mattresses 2 are preferably substantially flexible, these edges 8 of the mattress 2 will be buried to some extent, as shown in figure 3. This process will be further elucidated using figures 9 and 10. Once the situation shown in figure 3 has been obtained, the scour protector 1 offers optimum scour protection to the subsea structure 50.

Although the mattress 2 may be floating if it is made of a mass density lower than the mass density of water, it may also be float because air or another fluid has been introduced into the mattress 2. For the latter situation, said mattress 2 comprises a compartment 10 with at least one inlet opening 12.

The mattresses 2, which are preferable made of textile, may be transported in a coiled state, i.e. in the form of a roll. When the mattress 2 is filled with air, it automatically expands and will uncoil into an elongate rectangular shape. Once filled with air, the mattress 2 floats on the sea surface 64 and may be arranged near a subsea structure 50, such as monopile 52, that partly extends above the sea surface 64. The part of the subsea structure 50 that extends above the sea surface 64 is accommodated in an accommodation 28 or said mattress 2. The accommodation 28 is dimensioned to accommodate a subsea structure 50 in a sunken state of said mattress 2. As shown in figure 1, also the cable guide 56 is accommodated in accommodation 28.

Although not explicitly shown in the figures, the step of figures 4 and 5 is preferably executed when the monopile 52 is installed and only extends for a limited height above the sea surface 64. Thus, in figures 4 and 5, the wind turbine 54 may not have been arranged yet.

According to an alternative method, the scour protector 1 may be arranged on the seabed 66, said scour protector 1 having an accommodation dimensioned to accommodate a subsea structure 50. This subsea structure 50, for instance a monopile 52 may be arranged through said accommodation after the scour protector has been arranged on the seabed 66. As this (not shown) method puts high demands on the exact positioning of the scour protector 1 and aligning the subsea structure 50 with the accommodation of said subsea structure 50, it is preferred to arranged the scour protector 1 around and / or against a subsea structure 50 that is already arranged on the sea bed 66.

It is furthermore noted that the accommodation 28 of the mattress 2 of the scour protector 1 according to the invention, also allows this scour protector 1 to be arranged easily around piles or other types of foundations, such as a tripod or tri-pile foundation.

In order to obtain the scour protector 1 as shown in figure 1, couples or mattresses 2 are connected with at least one mattress connector 26 when they are floating on the sea surface 64. Each mattress 2 preferably comprises multiple mattress connectors 26.

After the step of floating one or more than one mattress 2 on the sea surface 64, and eventually connecting multiple mattresses 2 with mattress connectors 26 in order to obtain an assembled scour protector 1 (figure 6), the next step is sinking the at least one mattress 2, ie the scour protector 1, into the sea (figure 7).

The mattresses 2 comprise a compartment 10 with at least one inlet opening 12, said said compartment 10 is fillable with a filling medium 42 that has a mass density equal to or lower than the mass density of water. In figure 7, the compartment 10 or the mattress 2 is filled with water as filling medium 42. When water is introduced from vessel 46 through a filling conduit 48 and through the inlet opening 12 into compartment 10, the air 40 inside said compartment 10 is compressed and leaves compartment 10 through outlet opening 14. Outlet opening 14 may comprise a valve 16, that is preferably a pressure valve.

The filling medium 42 may also include water with suspended particles in order to increase the mass density of this suspension, and vary the sinking process.

In an alternative embodiment, shown in figure 12, multiple outlet opening 14 or said compartment 10 are arranged on a top surface 4 or said mattress 2, said multiple outlet opening 14 including valves 16 configured for evenly releasing fluid 40, 42 out of the compartment 10 or said mattress 2.

When water as filling medium 42 replaces the air as filling medium 40 inside compartment 10, the weight of the mattress 2, and consequently the weight of the scour protector 1, increases, and the mattress 2, and consequently the scour protector 1, will sink into the sea (figure 7).

Once the scour protector 1 has reached the seabed 66, a preferred step or further increasing the weight or at least one mattress 2 or said scour protector 1 may be executed. This step comprises at least partially replacing the filling medium 42 water in said compartment 10 with a further filling medium 44 that has a higher mass density than the filling medium 42 used for sinking said mattress 2. Said further filling medium 44 preferably comprises sand.

When sand as filling medium 44 replaces the water as filling medium 42 inside compartment 10, the weight of the mattress 2, and consequently the weight of the scour protector 1, increased further, and the mattress 2, and consequently the scour protector 1, will be arranged even more secure on the seabed 66 (figure 8).

Preferably, in figure 8, compartment 10 is only partially filled with sand as the further filling medium 42, maintaining flexibility of said mattress 2. Flexibility of the mattress 2 provides increased scour protection, as will be explained using figures 9 and 10.

In figure 9, the edges 8 of the mattress 2 of the scour protector 1 also experience a scour effect, as already shortly described above. This scour effect can be seen in figure 10, where a small scour hole 70 is formed adjacent the edge 8 or mattress 2. When this scour hole 70 grows, the edge 8 of the mattress 2 will fall into the scour hole 70. This falling into the scour hole 70 or the edge 8 of the mattress 2 is possible due to the flexibility of the mattress 2.

The edges 8 of mattress 2 are preferably tapered, so that the scour protector 1 is more aerodynamic and less susceptible for fluid flow. Furthermore, tapered edges 8 increase the flexibility of said edges 8, contributing to the effect shown in figure 10.

In the state shown in figure 9, at least one of the inlet opening 12 and outlet opening 14 are left open, which also contributes to the flexibility of the scour protector 1.

In figure 11, mattress 2 comprises a bottom 6 and a top surface 4 with a connector 18 arranged in between, said connector 18 having a predetermined length defining the thickness of the mattress 2 when in use. When the compartment 10 of the mattress 2 is filled with a filling medium 40, 42, 44, one or more than one connector 18 prevent bulging out of the scour protector

1.

Although the connectors 18 may be theoretically rigid bars, it is preferred that the connectors are capable of being rolled up together with the mattress 2. As flaps could interfere with certain types of filling medium, especially sand, it is preferred that the connectors are strings

20. The strings 20 may contain one or more than one fiber 22, and preferably a variety of fibers

22. If said fibers 22 comprise glass fibers, this adds to the weight of the scour protector 1.

The strings 20 of the connector 18 are preferably included in a bundle, and multiple connectors 18 are arranged in a pattern in the compartment 10 of the mattress 2, in this pattern leaves channels 24 for said filling medium, which is especially advantageous for the further filling medium 44 that preferably comprises sand.

According to an alternative embodiment, shown in figures 13-15, the mattress 2 is again preferably made of textile, including the top surface 4 comprising pores 5, and the bottom surface 6 comprising pores 7. Due to the pores 5, 7 , the top and bottom surfaces 4, 6 are permeable for water and air.

In the figure 13, the mattresses 2 of the scour protector 1 are preferably continuously pressurized with air, that partly escapes from the compartments 10 of the mattresses 2 through the pores 5, 7, as can be seen in figure 13. It is noted that substantially continuous pressurizing means that a substantial continuous overpressure has been maintained, but the skilled person will understand that small interruptions in pressurizing will not negatively influence the floatability of the mattress 2.

When the mattresses 2 are assembled to form a scour protector 1, and said scour protector 1 has been positioned in the desired position, pressurizing or the compartment 10 with air is stopped. Although the filling conduit 48 that introduced the air as filling medium 40 into the compartment 10 may be disconnected, it may also remain connected (as shown in figure 14) so that it can be used in a later step for filling the compartment 10 of the mattress 2 with a further filling medium 44, eg sand.

In figure 14, water enters the compartment 10 through the pores 7 in the bottom surface 6 of the mattress 2. The pores 7 function as inlet opening 12, and the water as filling medium 42 replaces the air as previous filling medium 40. The air is released from the compartment 10 through the pores 5 in the top surface 4 of the mattress 2. the pores 5 in the top surface 4 function as outlet opening 14, and further outlet opening 14 including pressure relief valves 16 may also be arranged in the top surface 4. Due to the water replacing the air in the compartment 10, the weight of the mattress 2 increases and the mattress 2 starts to sink into the sea.

Once the scour protector 1 has reached the seabed 66, a preferred step or further increasing the weight or at least one mattress 2 or said scour protector 1 may be executed. This step comprises at least partially replacing the filling medium 42 water in said compartment 10 with a further filling medium 44 that has a higher mass density than the filling medium 42 used for sinking said mattress 2, similar to figure 8.

Preferably, said further filling medium 44 comprises sand with seeds of water plants. The water plants 72, such as sea weed, may grow through the pores 5 in the top surface 4 of the mattress 2. In addition to providing underwater flora and contributing to underwater life, the plants 72 also influence the flow of water around the subsea structure 50. The water flow is reduced, and therefore contributors to the scour protection.

Although they show preferred embodiment of the invention, the above described are only intended to illustrate the invention and not to limit in any way the scope of the invention. Applied claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of claims and are in no way limiting the scope of claims. Furthermore, it is particularly noted that the skilled person can combine technical measures or the different expenses. The scope of the invention is therefore defined solely by the following claims.

Claims (28)

Conclusions An erosion protector, comprising one or more than one mattress, comprising a state in which the mattress is configured to float on water. Erosion protector according to claim 1, wherein the mattress comprises a compartment with at least one inlet opening, the compartment being fillable with a filling medium that has a density equal to or less than the density of water. The erosion protector according to claim 2, wherein the compartment of the mattress further comprises at least one outlet opening. Erosion protector according to claim 3, wherein a plurality of outlet openings of the compartment are arranged on an upper surface of the mattress, the plurality of outlet openings comprising valves which are adapted to uniformly divert fluid out of the compartment of the mattress. Erosion protector according to one of the preceding claims, wherein the mattress is substantially flexible. Erosion protector according to one of the preceding claims, wherein the mattress is made of textile. An erosion protector according to any one of the preceding claims, wherein the mattress comprises a lower and upper surface with a connection arranged between them, the connection having a predetermined length which defines the thickness of the mattress during use. The erosion protector of claim 7, wherein the connection is a cord. The erosion protector of claim 8, wherein the cord comprises one or more than one fiber, and preferably a plurality of fibers. The erosion protector of claim 9, wherein the fibers comprise at least glass fibers. The erosion protector according to any of claims 8-10, wherein the cords are arranged in a pattern that releases channels for the filling medium. 12. Erosion protector according to any one of the preceding claims, wherein the mattress comprises a mattress connection that connects pairs of mattresses during use. Erosion protector according to any one of the preceding claims, wherein at least one mattress comprises an accommodation which has dimensions for being able to accommodate a subsea construction in a sunken state of the mattress. Erosion protector according to one of the preceding claims, wherein at least one outer edge of the mattress is chamfered. Erosion protector according to any of the preceding claims, wherein the upper surface comprises pores and the lower surface comprises pores, the pores making the mattress permeable to water and air. A method of applying an erosion protector to a sea bed, comprising the steps of: - floating at least one mattress on the sea surface; and - sinking the at least one mattress into the sea. 17. Method as claimed in claim 16, comprising the step of applying a mattress near a subsea structure, in particular a monopile, which partially extends above the sea surface, wherein the part of the subsea construction that extends above the sea surface in a accommodation of the mattress is accommodated. A method according to claim 16 or 17, comprising the step of connecting pairs of mattresses to at least one mattress joint when they float on the sea surface. A method according to any of claims 16-18, comprising the step of filling a filling medium in a compartment of the mattress, whereby the weight of the mattress increases and the at least one mattress is sunk into the sea. The method of claim 19, wherein the filling medium comprises water. A method according to any of claims 16-20, wherein the mattress comprises an upper surface and a lower surface with pores, wherein the pores make the mattress permeable to water and air; - wherein the step of floating the at least one mattress on the sea surface comprises pressurizing a compartment of the at least one mattress with air as filling medium; and - wherein the step of sinking the at least one mattress into the sea allows water as filling medium to enter the compartment through the pores in the bottom surface and the release of air from the compartment through the pores and / or outlet openings in the upper surface, includes. The method of any one of claims 16 to 21, further comprising the step of further increasing the weight of the at least one mattress when the erosion protector is disposed on the seabed. A method according to claim 22, comprising the step of at least partially replacing the filling medium in the compartment with a further filling medium that has a higher density than the filling medium used for sinking the mattress. The method of claim 22, wherein the further fill medium comprises sand. The method of claim 24, wherein the sand comprises seeds of aquatic plants. 26. Method as claimed in any of the claims 23-25, comprising the step of only partially filling the compartment with a further filling medium, whereby flexibility of the mattress is retained. A method according to any of claims 23-26, comprising the step of leaving at least one of the inlet opening and the outlet opening open after the step of at least partially replacing the filling medium in the compartment with a further filling medium . A method according to any of claims 16-27, comprising the step of applying an erosion protector according to any of claims 1-15. αΠ 2/7 3/7 CM 4/7