Scour protection device for offshore wind turbine transmission cables

Abstract

The present invention relates to the technical field of offshore wind power equipment, and in particular to a scour protection device for an offshore wind turbine transmission submarine cable, comprising a submarine cable protection stone bag group, wherein the submarine cable protection stone bag group comprises a supporting stone bag group, a limiting stone bag group and a fixed stone bag group formed by a plurality of stone bags. The supporting stone bag group is arranged in a suspended area of ​​the submarine cable and is located below the submarine cable to support the submarine cable. The limiting stone bag group is located in the suspended area and on both sides of the submarine cable to clamp the submarine cable. The fixed stone bag group comprises a suspended covering stone bag group and a ground-contacting reinforcement stone bag group. The suspended covering stone bag group is located in the suspended area and above the submarine cable to compact the submarine cable. The ground-contacting reinforcement stone bag group is located in the ground-contacting area of ​​the submarine cable and comprises a T-shaped end stone bag group. The T-shaped end stone bag group comprises a circumferentially arranged stone bag group and a compacting stone bag group arranged in a T-shape. The circumferentially arranged stone bag group extends along the circumference of the concentric circle of the pile foundation. The compacting stone bag group is arranged above the submarine cable in the extending direction of the coastal cable. The circumferentially arranged stone bag group is farther away from the pile foundation than the compacting stone bag group.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power equipment, and in particular to a scour protection device for an offshore wind turbine transmission cable. Background Art

[0002] With the continuous development of offshore wind power generation technology, the installed capacity of offshore wind turbines has been increasing year by year. The natural environment in which offshore wind turbines are located is relatively harsh. The area around the installation base of the underwater pile foundation has been subjected to long-term water erosion, and sand and soil loss has formed scouring pits, resulting in a reduction in the burial depth of the installation base of the underwater pile foundation. The submarine cables laid under the seabed are exposed or even partially suspended, which is detrimental to the structural safety of the wind turbine and the operation and maintenance of the wind farm. In order to avoid the damage caused by local scouring of the underwater pile foundation, the existing treatment method is mainly to arrange riprap and sandbags to suppress the development of local scouring pits. However, the existing technology has the following shortcomings: protective measures such as riprap and sandbags are unstable and will move under the action of water, causing secondary scouring and increasing the risk of large-scale exposure of submarine cables. Summary of the Invention

[0003] The object of the present invention is to provide a scour protection device for an offshore wind turbine transmission cable, which can improve stability, help suppress secondary scour and protect the submarine cable.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] Provided is a scour protection device for an offshore wind turbine transmission cable, comprising:

[0006] The stone bag group for protecting the submarine cable includes a supporting stone bag group, a limiting stone bag group and a fixed stone bag group formed by a plurality of stone bags. The supporting stone bag group is arranged in the suspended area of ​​the submarine cable, and the supporting stone bag group is located below the submarine cable to support the submarine cable. The limiting stone bag group is located in the suspended area. The stone bags of the limiting stone bag group are located on both sides of the submarine cable to clamp the submarine cable. The fixed stone bag group includes a suspended covering stone bag group and a ground reinforcement stone bag group. The suspended covering stone bag group is located in the suspended area and above the submarine cable to compress the submarine cable. The ground-touching reinforcement stone bag group is located in the ground-touching area of ​​the submarine cable, and the ground-touching reinforcement stone bag group includes a T-shaped end stone bag group, and the T-shaped end stone bag group includes a circumferentially arranged stone bag group and a compacted stone bag group. The circumferentially arranged stone bag group extends circumferentially along the concentric circles of the pile foundation, and the compacted stone bag group is arranged above the submarine cable along the extension direction of the submarine cable. The compacted stone bag group is vertically connected to the midpoint of the circumferentially arranged stone bag group so that the circumferentially arranged stone bag group and the compacted stone bag group are arranged in a T-shape, and the circumferentially arranged stone bag group is farther away from the pile foundation than the compacted stone bag group.

[0007] Optionally, the center of the stone bag of the fixed stone bag group is located vertically above the submarine cable.

[0008] Optionally, a group of spoiler stone bags around the pile is formed by arranging multiple stone bags, and the group of spoiler stone bags around the pile includes multiple first stone bag groups arranged along the outer wall curved surface of the pile foundation, and also includes multiple second stone bag groups arranged circumferentially along the concentric circles of the pile foundation, and the second stone bag group is close to the first stone bag group.

[0009] Optionally, the area where the spoiler stone bag group is located includes a horseshoe vortex generating area in front of the pile foundation;

[0010] And / or, the area where the group of spoiler stone bags around the pile is located includes the lateral streamline contraction area of ​​the pile foundation;

[0011] And / or, the area where the pile-surrounding spoiler stone bag group is located includes the rear vortex shedding area of ​​the pile foundation;

[0012] And / or, the vertical projection of the spoiler bag group around the pile covers part of the vertical projection of the area where the submarine cable is located.

[0013] Optionally, a backfill pit stone bag group formed by arranging a plurality of the stone bags is further included, and the backfill pit stone bag group is used to fill the pit so that the depth of the filled pit is less than a maximum preset scouring depth.

[0014] Optionally, the backfill scouring stone bag group covers the edge area of ​​the protective submarine cable stone bag group.

[0015] Optionally, the top elevation of the backfill scour pit stone bag group is flush with the surrounding seabed;

[0016] And / or, the top elevation of the backfill pit stone bag group is at most flush with the top elevation of the protective submarine cable stone bag group.

[0017] Optionally, among the protective cable stone bag group, the pile-surrounding spoiler stone bag group and the backfill pit stone bag group, the elevations of the stone bags adjacent to each other are smoothly transitioned;

[0018] And / or, the stone bags at the edge of the protection area where the protective submarine cable stone bag group, the pile-surrounding spoiler stone bag group and the backfill pit stone bag group are located as a whole are one layer, and the stone bags inside the protection area are more than one layer.

[0019] Optionally, the vertical projection of the protection area where the protective cable stone bag group, the pile-surrounding spoiler stone bag group and the backfill pit stone bag group are located as a whole is fan-shaped.

[0020] Optionally, the stone bags at the bottom layer of the protective cable stone bag group, the pile-surrounding spoiler stone bag group, and the backfill pit stone bag group are closely arranged;

[0021] And / or, all the stone bags in the group of backfill stone bags are tightly arranged;

[0022] And / or, all the stone bags in the pile-surrounding spoiler stone bag group are tightly arranged.

[0023] Beneficial effects of the present invention:

[0024] The present invention provides a scour protection device for an offshore wind turbine transmission submarine cable, comprising a group of stone bags for protecting the submarine cable, wherein the group of stone bags for protecting the submarine cable comprises a supporting stone bag group, a limiting stone bag group and a fixed stone bag group formed by a plurality of stone bags arranged. The supporting stone bag group is arranged in the suspended area of ​​the submarine cable, and the supporting stone bag group is located below the submarine cable to support the submarine cable. The limiting stone bag group is located in the suspended area, and the stone bags of the limiting stone bag group are located on both sides of the submarine cable to clamp the submarine cable to prevent lateral movement of the submarine cable. The fixed stone bag group comprises a suspended covering stone bag group and a ground-touching reinforcement stone bag group, and the suspended covering stone bag group is located in the suspended area and above the submarine cable to compress the submarine cable, reduce the hydrodynamic amplitude of the submarine cable, and increase the stability of the stone bags below. The ground reinforcement stone bag group is located in the ground area of ​​the submarine cable. The ground reinforcement stone bag group includes a T-shaped end stone bag group. The T-shaped end stone bag group includes a circumferentially arranged stone bag group and a compacted stone bag group. The circumferentially arranged stone bag group extends along the circumference of the concentric circles of the pile foundation. The compacted stone bag group is arranged above the submarine cable along the extension direction of the submarine cable. The compacted stone bag group is vertically connected to the midpoint of the circumferentially arranged stone bag group so that the circumferentially arranged stone bag group and the compacted stone bag group are arranged in a T-shape. The circumferentially arranged stone bag group is farther away from the pile foundation than the compacted stone bag group. The T-shaped end stone bag group can avoid end scouring and sinking and instability. First of all, compared with sandbags and riprap, stone bags have better stability. And through the reasonable planning and design of the above-mentioned stone bag group, secondary scouring can be suppressed to the greatest extent, preventing large-scale exposure of the submarine cable and protecting the submarine cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a group of stone bags for flow disturbance around piles provided by an embodiment of the present invention;

[0026] Figure 2 2. It is a structural diagram of a two-layer stone bag group for flow disturbance around piles provided by an embodiment of the present invention;

[0027] Figure 3 2 is a schematic structural diagram of a rock bag group for protecting a No. 1 submarine cable and a rock bag group for protecting a No. 2 submarine cable provided by an embodiment of the present invention;

[0028] Figure 4 2 is a schematic structural diagram of a second-layer rock bag group for protecting a No. 1 submarine cable and a second-layer rock bag group for protecting a No. 2 submarine cable provided by an embodiment of the present invention;

[0029] Figure 5Schematic diagram of the structure of a three-layer stone bag group and a four-layer stone bag group for protecting No. 1 submarine cable provided by an embodiment of the present invention;

[0030] Figure 6 This is a schematic structural diagram of a layer of stone bag groups for backfilling a scouring pit provided by an embodiment of the present invention;

[0031] Figure 7 is a schematic diagram of an experimental water tank provided in an embodiment of the present invention;

[0032] Figure 8 The topographic map scanned at the beginning of the experiment provided by the embodiment of the present invention;

[0033] Figure 9 This is a topographic map scanned 2 hours after the experiment provided by the embodiment of the present invention;

[0034] Figure 10 This is a topographic map obtained after 8 hours of experimentation provided by an embodiment of the present invention.

[0035] In the picture:

[0036] 1. Pile foundation; 2. Submarine cable No. 1; 3. Submarine cable No. 2;

[0037] 4. One layer of stone bags to disrupt the flow around the piles; 5. Two layers of stone bags to disrupt the flow around the piles; 6. One layer of stone bags to protect the No. 1 submarine cable; 7. One layer of stone bags to protect the No. 2 submarine cable; 8. Two layers of stone bags to protect the No. 1 submarine cable; 9. Two layers of stone bags to protect the No. 2 submarine cable; 10. Three layers of stone bags to protect the No. 1 submarine cable; 11. Four layers of stone bags to protect the No. 1 submarine cable; 12. One layer of stone bags to backfill the scouring pit;

[0038] 13. Sand bed; 14. Gentle slope; 15. Experimental fan foundation; 16. Velocity meter; 17. Laser terrain scanner. DETAILED DESCRIPTION

[0039] Before any embodiments of the present application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the foregoing drawings.

[0040] In this application, the terms "comprises," "includes," "has," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0041] In this application, the term "and / or" describes a relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Additionally, the character " / " in this application generally indicates that the related objects are in an "and / or" relationship.

[0042] In this application, the terms "connect," "combine," "couple," and "install" may refer to direct connection, combination, coupling, or installation, or indirect connection, combination, coupling, or installation. For example, a direct connection refers to two parts or components being connected together without an intermediary, and an indirect connection refers to two parts or components being connected to at least one intermediary, with the two parts or components being connected via the intermediary. Furthermore, "connect" and "couple" are not limited to physical or mechanical connections or couplings and may include electrical connections or couplings.

[0043] In this application, it will be understood by those skilled in the art that relative terms (e.g., "about," "approximately," "substantially," etc.) used in conjunction with quantities or conditions include the values ​​and have the meaning indicated by the context. For example, the relative terms include at least the degree of error associated with the measurement of a specific value, the tolerance caused by manufacturing, assembly, use, etc. associated with a specific value. Such terms should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. Relative terms may refer to plus or minus a certain percentage (e.g., 1%, 5%, 10% or more) of the indicated value. Numerical values ​​that do not use relative terms should also be disclosed as specific values ​​with tolerances. In addition, "substantially" may refer to plus or minus a certain degree (e.g., 1 degree, 5 degrees, 10 degrees or more) on the basis of the indicated angle when expressing a relative angular position relationship (e.g., substantially parallel, substantially perpendicular).

[0044] In this application, it will be understood by those skilled in the art that the function performed by an assembly can be performed by one assembly, multiple assemblies, one part, or multiple parts. Similarly, the function performed by a part can also be performed by one part, one assembly, or a combination of multiple parts.

[0045] In the present application, the terms "upper", "lower", "left", "right", "front", "back" and other directional words are described based on the orientation and positional relationship shown in the accompanying drawings, and should not be understood as limiting the embodiments of the present application. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to the other element "upper" or "lower", but also be indirectly connected to the other element "upper" or "lower" through an intermediate element. It should also be understood that directional words such as upper side, lower side, left side, right side, front side, back side, etc. not only represent the positive orientation, but can also be understood as the lateral orientation. For example, below can include directly below, lower left, lower right, lower front and lower back, etc.

[0046] Offshore wind turbines operate in a harsh natural environment. The areas surrounding the turbine monopile foundations are subject to long-term erosion, which can easily form scour pits. This erosion and loss of soil around the monopile foundations reduces the buried depth of the monopile foundations, exposing submarine cables laid below the seabed and increasing the cable span, negatively impacting the structural safety of the wind turbines and the operation and maintenance of the wind farm. To mitigate the hazards of localized scour, existing approaches primarily focus on suppressing the formation of localized scour pits. Specifically, measures such as riprap and sandbags are deployed around the turbine pile foundations to reduce water erosion around the piles and protect the piles and cables. However, these protective measures, such as riprap and sandbags, fail to provide targeted protection for the wind turbine cables, and excessive, indiscriminate protection over large areas can result in wasted project costs. Furthermore, these protective measures lack stability and can shift under the influence of water, causing secondary scour and failing to further mitigate the risk of widespread cable exposure.

[0047] This embodiment provides a scour protection device for an offshore wind turbine cable to address the above-mentioned problem. The scour protection device is primarily used for unprotected pile foundations 1 subject to local scour, as well as pile foundations 1 and the surrounding area of ​​the cable where scour protection has been ineffective.

[0048] The scour protection device of the offshore wind turbine transmission submarine cable includes a group of stone bags to protect the submarine cable. The group of stone bags to protect the submarine cable includes a supporting stone bag group, a limiting stone bag group and a fixed stone bag group formed by arranging multiple stone bags. The supporting stone bag group is arranged in the suspended area of ​​the submarine cable, and the supporting stone bag group is located below the submarine cable to support the submarine cable. The limiting stone bag group is located in the suspended area, and the stone bags of the limiting stone bag group are located on both sides of the submarine cable to clamp the submarine cable. The submarine cable is located between the two stone bags. The limited space between the two stone bags can be used to limit the movement of the submarine cable to prevent the submarine cable from moving sideways. The fixed stone bag group includes a suspended covering stone bag group and a ground-breaking reinforcement stone bag group. The suspended covering stone bag group is located in the suspended area and above the submarine cable to compress the submarine cable, reduce the hydrodynamic amplitude of the submarine cable, and increase the stability of the stone bag below. The ground reinforcement stone bag group is located in the ground area of ​​the submarine cable. The ground reinforcement stone bag group includes a T-shaped end stone bag group. The T-shaped end stone bag group includes a circumferentially arranged stone bag group and a compacted stone bag group. The circumferentially arranged stone bag group extends along the circumference of the concentric circle of the pile foundation 1. The compacted stone bag group is arranged above the submarine cable along the extension direction of the submarine cable. The compacted stone bag group is vertically connected to the midpoint of the circumferentially arranged stone bag group so that the circumferentially arranged stone bag group and the compacted stone bag group are arranged in a T shape. The circumferentially arranged stone bag group is farther away from the pile foundation 1 than the compacted stone bag group. The T-shaped end stone bag group can avoid end scouring and sinking and instability. First of all, compared with sandbags and riprap, stone bags have better stability. And through the reasonable planning and design of the above-mentioned stone bag group, secondary scouring can be suppressed to the greatest extent, preventing large-scale exposure of the submarine cable and protecting the submarine cable.

[0049] Optionally, the coverage of the grounded area where the grounded reinforcement stone bag group is located is a coverage appropriately extended by 2-3 times the diameter of the stone bag along the buried section of the submarine cable.

[0050] Optionally, the center of the stone bag of the fixed stone bag group is located vertically above the submarine cable, that is, the center of the stone bag covers the submarine cable, which can ensure that the coverage area of ​​a single stone bag is maximized and prevent the submarine cable from jumping out of the stone bags on both sides of the limiting stone bag group.

[0051] Optionally, the scour protection device of the offshore wind turbine transmission cable also includes a pile-surrounding spoiler stone bag group formed by a plurality of stone bags, the pile-surrounding spoiler stone bag group includes a plurality of first stone bag groups arranged along the outer wall curved surface of the pile foundation 1, and also includes a plurality of second stone bag groups arranged circumferentially along the concentric circles of the pile foundation 1, and the second stone bag group is close to the first stone bag group.

[0052] Optionally, the distance between the outermost edge of the spoiler bag group around the pile and the center of the pile foundation 1 is within the range of 2D-3D, where D is the diameter of the pile foundation 1. The arrangement can be the above-mentioned circular arrangement, which does not need to be closed, and the angle of the surrounding coverage can be determined according to the degree of scouring on site.

[0053] Optionally, the design of the spoiler stone bag group around the pile can be to arrange the stone bags along the cable line. If the direction along the cable line is not along the direction of the rising and falling tides of the main tide, then the stone bags can be arranged in the direction of the rising and falling tides of the main tide to completely cover the surrounding area of ​​the pile foundation 1.

[0054] Optionally, the area where the spoiler stone bags are located includes the horseshoe vortex generation area in front of the pile foundation 1, disrupting the strong flow field structure around the cylinder and preventing the horseshoe vortex in front of the pile from fully developing. Optionally, the area where the spoiler stone bags are located includes the lateral streamline contraction area of ​​the pile foundation 1, so as to hinder the contraction of the lateral streamlines. Optionally, the area where the spoiler stone bags are located includes the vortex shedding area behind the pile foundation 1, so as to weaken the shedding of the rear tail vortex, reduce the shear stress amplification effect of the bottom bed around the pile foundation 1, and thus play a role in inhibiting the development of local scour.

[0055] Optionally, the scour protection device for the offshore wind turbine outbound cable also includes a backfill stone bag group formed by a plurality of arranged stone bags. The backfill stone bag group is used to fill the scour pit so that the depth of the filled scour pit is less than a maximum preset scour depth. The backfill stone bag group can prevent the scour pit from continuing to expand and exposing the submarine cable, reduce the scour pit depth, promote siltation and sand consolidation, and minimize the scour impact area.

[0056] Optionally, the backfilling stone bag group covers the edge area of ​​the cable protection stone bag group. The cable protection stone bag group is located along the cable line, and the backfilling stone bag group is located on both sides of the cable, so that the backfilling stone bag group can play the role of fastening the cable protection stone bag group from both sides.

[0057] Optionally, the top elevation of the backfill scouring pit stone bag group cannot be too high, and the highest elevation is flush with the surrounding seabed. Optionally, the top elevation of the backfill scouring pit stone bag group is flush with the top elevation of the protective submarine cable stone bag group.

[0058] Optionally, among the groups of stone bags for protecting submarine cables, the groups of stone bags for disturbing flow around piles and the groups of stone bags for backfilling pits, the elevations of the stone bags adjacent to each other are smoothly transitioned to prevent the stone bags from sliding away from the designed positions and thus losing their protective function.

[0059] Optionally, there is one layer of stone bags at the edge of the protection area where the submarine cable stone bag group, the pile spoiler stone bag group and the backfill pit stone bag group are located as a whole, and there is more than one layer of stone bags inside the protection area, that is, the number of layers of stone bags at the edge of the protection area is less than the number of layers of stone bags inside the protection area.

[0060] Optionally, the vertical projection of the protection area where the submarine cable protection stone bag group, the pile surrounding spoiler stone bag group and the backfill pit stone bag group are located as a whole is fan-shaped, ensuring the maximum coverage of the area along the submarine cable.

[0061] Optionally, the bottom layer of the stone bags protecting the submarine cable stone bag group, the pile surrounding spoiler stone bag group and the backfill pit stone bag group are arranged tightly to ensure that the bottom foundation will not loosen, which is conducive to fixing the position of the upper stone bags.

[0062] Optionally, all the stone bags in the backfill pit stone bag group are closely arranged so that adjacent stone bags can provide lateral resistance support to each other to prevent the slope from sliding.

[0063] Optionally, all the stone bags in the spoiler stone bag group around the pile are tightly arranged to prevent the slope from sliding.

[0064] Optionally, the filling volume of each stone bag group can be adjusted based on actual conditions while ensuring stability, and the filling opening can be tightened after filling for ready use. Optionally, the maximum mesh size of the stone bag is between 5 cm and 10 cm. Optionally, each stone bag is equipped with a lifting structure to facilitate secondary installation and removal.

[0065] like Figures 1-6 As shown in the figure, in order to illustrate how to reasonably arrange stone bags around pile foundations 1 with different scouring degrees, the No. 1 submarine cable 2 in the figure represents a submarine cable with severe scouring degree, specifically, the submarine cable span distance is greater than the design specification, and there are scouring pits along the submarine cable. The No. 2 submarine cable 3 is a submarine cable with a slight scouring degree but is strongly affected by hydrodynamics. Specifically, the submarine cable span length is less than the design specification, and there is only a short span at the wind turbine submarine cable outlet. However, under the action of hydrodynamics, the submarine cable has a large movement amplitude and is prone to fatigue damage.

[0066] The scour protection device for the offshore wind turbine transmission cable No. 1 submarine cable 2 includes a first-layer stone bag group 4 and a second-layer stone bag group 5 for pile disturbance arranged around the pile foundation 1, as well as a first-layer stone bag group 6 for protecting the No. 1 submarine cable, a second-layer stone bag group 8 for protecting the No. 1 submarine cable, a third-layer stone bag group 10 for protecting the No. 1 submarine cable, and a fourth-layer stone bag group 11 for protecting the No. 1 submarine cable, and also includes a first-layer stone bag group 12 for backfilling the scour pit.

[0067] The first-layer stone bag group 4 for perforating the pile flow is arranged in a circular pattern around the pile foundation 1, and three arc-shaped stone bag groups are arranged radially, with a coverage range of 2-2.5 times the diameter of the pile foundation 1 axially. The second-layer stone bag group 5 for perforating the pile flow is arranged above the first-layer stone bag group 4 for perforating the pile flow, close to the outer wall of the pile foundation 1. The second-layer stone bag group 5 for perforating the pile flow includes two arc-shaped stone bag groups, and both the circular coverage range and the radial coverage range are smaller than the first-layer stone bag group 4 for perforating the pile flow. The upper-layer stone bags are stacked alternately with the lower-layer stone bags, and the upper-layer stone bags cover the gaps of the lower-layer stone bags. Both the first-layer stone bag group 4 for perforating the pile flow and the second-layer stone bag group 5 for perforating the pile flow are located below the submarine cable. The stone bags in the second-layer stone bag group 5 for perforating the pile flow corresponding to the submarine cable position can support the submarine cable from below, and the stone bags on both sides can provide lateral support to the two stone bags to prevent displacement and failure.

[0068] The first-layer stone bag group 6 for protecting submarine cable No. 1 is arranged in close contact with the first-layer stone bag group 4 for disturbing flow around piles. The first-layer stone bag group 6 for protecting submarine cable No. 1 is located in the area where the submarine cable is located and on the side of the first-layer stone bag group 4 for disturbing flow around piles away from the pile foundation 1. The three innermost stone bags of the first-layer stone bag group 6 for protecting submarine cable No. 1 close to the pile foundation 1 are located below the submarine cable to support the submarine cable, and belong to the supporting stone bag group. The two stone bags close to the innermost three stone bags of the first-layer stone bag group 6 for protecting submarine cable No. 1 are located on both sides of the submarine cable to fix the submarine cable, and belong to the limiting stone bag group. The two stone bags close to the middle of the two stone bags are arranged in a single row of stone bags, both located above the submarine cable, and are used to compress and fix the submarine cable, and belong to the fixing stone bag group. The four stone bags farthest from the pile foundation 1 of the first-layer stone bag group 6 for protecting submarine cable No. 1 are arranged in a "T" shape, and belong to the T-shaped end stone bag group, which is used to prevent the end from being scoured, sinking and becoming unstable.

[0069] The second-layer stone bag group 8 protecting the No. 1 submarine cable is arranged in a triangular pattern, with more stone bags near the pile foundation 1 and fewer stone bags away from the pile foundation 1. The second-layer stone bag group 8 protecting the No. 1 submarine cable is arranged closely to the second-layer stone bag group 5 around the pile, with the three innermost stone bags belonging to the support stone bag group, the two middle stone bags belonging to the limit stone bag group, and the outermost stone bag belonging to the fixed stone bag group.

[0070] Three layers of rock bags 10 are placed close to pile foundation 1 to protect Cable No. 1. Three rows of rock bags are arranged sequentially along the cable. Each row includes two rock bags, one on each side of the cable to secure it. The six rock bags in this three-layer group 10 are position-limiting, with one additional rock bag, located on the outermost side, serving as a fixed rock bag.

[0071] One of the stone bags in the four-layer stone bag group 11 protecting the No. 1 submarine cable is located in the gap between the three outermost stone bags in the three-layer stone bag group 10 protecting the No. 1 submarine cable and covers the submarine cable. It belongs to the suspended covering stone bag group of the fixed stone bag group.

[0072] A layer of stone bag groups 12 are arranged on both sides of the scouring area on both sides of the No. 1 submarine cable 2. The layer of stone bag groups 12 are arranged on both sides of the layer of stone bag groups 6 protecting the No. 1 submarine cable, and the arrangement is a horizontal and tight arrangement.

[0073] The scour protection device for the offshore wind turbine outbound cable, cable No. 2, includes a first-layer rock bag group 7 and a second-layer rock bag group 9. The first-layer rock bag group 7 is positioned closely against the pile foundation 1. The three inner rock bags near the pile foundation 1 are the supporting rock bag group, the three rock bags farther from the pile foundation 1 are the T-shaped end rock bag group that secures the cable, and the two middle rock bags are the limiting rock bag group, securing the cable from both sides. The second-layer rock bag group 9 is positioned closely against the pile foundation 1 in a triangular arrangement, with more rock bags near the pile foundation 1 and fewer away from it. The inner rock bags are the limiting rock bag group, while the outer rock bags are the suspended covering rock bag group that secures the cable. Optionally, the number of layers and arrangement of the stone bag group for protecting the submarine cable are arranged according to the on-site status of the submarine cable. If the span is small, the end can be directly protected by a "T" shape anti-scour protection after being fixed at the submarine cable touchdown point.

[0074] Optionally, the number of layers and arrangement of the stone bag group for protecting the submarine cable are selected according to the on-site status of the submarine cable. If the span height of the submarine cable is small, there is no need to provide inner support with three stone bags. Instead, an arrangement of two stone bags limiting and one stone bag covering can be directly adopted.

[0075] Optionally, if the flow field around the pile foundation 1 is not sufficient to cause scouring around the pile foundation 1 , the group of flow-disturbing stone bags around the pile may not be arranged.

[0076] Alternatively, if there are no scouring holes or the scouring holes are shallow along the submarine cable line, no stone bag group may be deployed to backfill the scouring holes. If the scouring holes are deep, multiple layers of stone bag groups may be deployed to backfill the scouring holes, with the top elevation of the stone bag group not exceeding the topmost layer of the cable protection stone bag group.

[0077] It's understandable that in practical applications, the cable's configuration must first be determined to determine whether the span exceeds a preset value. A layer of cable protection stone bags is then deployed. In cases of severe scouring, a layer of pile-surrounding stone bags and a layer of backfill stone bags are then deployed. The stone bag closest to pile foundation 1 provides support for the cable and adjacent stone bags. The next innermost stone bag secures the cable and its touchdown point. The outermost stone bags cover the cable, and a T-shaped end stone bag group is placed on the outermost side to provide "T"-shaped anti-scouring protection.

[0078] By installing a first-layer stone bag group 4 and a second-layer stone bag group 5 around the pile to disrupt the flow field around pile foundation 1, the flow field around pile foundation 1 is disrupted, preventing further scouring. By installing a first-layer stone bag group 6 for protecting cable No. 1, a second-layer stone bag group 8 for protecting cable No. 1, a third-layer stone bag group 10 for protecting cable No. 1, a fourth-layer stone bag group 11 for protecting cable No. 1, a first-layer stone bag group 7 for protecting cable No. 2, and a second-layer stone bag group 9 for protecting cable No. 2, the cable affected by scouring is effectively protected, limiting the cable's motion and reducing the risk of fatigue damage. By backfilling existing scouring pits with a first-layer stone bag group 12, the terrain along the cable line is relatively flat. Furthermore, the stone bags increase the roughness of the seabed. The gaps between the stone bags create a porous structure, reducing bottom-level flow velocity, promoting sediment deposition, and preventing further scouring.

[0079] The scour protection device for the offshore wind turbine transmission cable is designed to specifically protect against seabed erosion and cable exposure caused by scour around the wind turbine's pile foundation 1 by providing three groups of protective stone bags, namely, a group of stone bags for spoiling the flow around the pile, a group of stone bags for protecting the cable, and a group of stone bags for backfilling the scour pit. Due to the wrapping effect of the net bag on the outer layer of the stone bag, the stability of the stone bag is greater than the stability of a single stone when throwing stones. The close arrangement of the stone bags on the same layer in the stone bag group can utilize the mutual support between the stone bags, thereby increasing the stability of a single stone bag. The close arrangement of the stone bags can also increase the roughness of the seabed, which is beneficial to reducing the flow rate of the bottom water flow and playing a role in promoting siltation and sand fixation. Compared with the protection methods such as throwing stones and sandbags in the prior art, the scour protection device for the offshore wind turbine transmission cable can effectively limit the movement of the cable under the action of water, and can especially effectively prevent the cable buried under the seabed from being exposed due to scour, thereby reducing the risk of damage to the cable due to secondary exposure. Moreover, the scour protection device of the offshore wind turbine's external submarine cable avoids the waste and redundancy of engineering costs caused by large-scale, non-targeted excessive protection such as riprap and sandbags, thereby reducing costs and increasing efficiency.

[0080] In order to enable those skilled in the art to better understand the technical solution of this embodiment, the following will be explained in conjunction with the experiments carried out to discuss the effectiveness of the scour protection device for the offshore wind turbine transmission cable proposed in this embodiment.

[0081] The experimental water tank is 30m long and 1.5m wide. The physical experiment section is arranged in the middle of the water tank with a total length of 10m. The core experiment section is as follows Figure 7As shown, the experimental section has a sand bed 13 with a height of 0.6 m and a length of 6 m. Sand bed 13 is made of washed quartz sand. Furthermore, upstream and downstream of the core experimental section, silt layers with a height of 0.2 m and a length of 2.0 m were laid, respectively. This ensures sufficient silt supply along the incoming flow during physical experiments. A 1:15 gentle slope 14 was also established at both ends of the experimental section to ensure a smooth transition of incoming flow into the core experimental section. The experimental wind turbine foundation 15 is made of a smooth-surfaced plexiglass tube with a diameter D of 0.15 m. The water depth was set to 0.9 m. The experimental coordinate system defines the flume's longitudinal direction as the y-axis, with the initial water flow flowing from the negative to the positive y-axis. The water depth direction is defined as the z-axis, with its zero point located at the initial sand bed plane and the direction from the bottom of the water to the surface as the positive z-axis direction. During the experiment, the velocity outside the boundary layer is measured in real time by a velocity meter 16 , and the scour depth and scour extension range around the experimental wind turbine foundation 15 are measured in real time by a laser terrain scanner 17 .

[0082] The experiment adopted the principle of similarity in flow intensity. To preserve the asymmetry of the scour intensity between the upstream and downstream sides of the piles, the flow was unidirectional. Based on calculations based on on-site hydrological conditions, the average flow velocity in the laboratory section was 0.55 m / s. At this velocity, the shear stress on the sand bed 13 in the experimental section was approximately three times the critical starting shear stress of the sediment, thus characterizing the scour type as a moving bed.

[0083] The initial layout of the experimental terrain is as follows: Figure 8 Before the scouring experiment began, the sand bed 13 was leveled and the submarine cables were buried. Cable 1 (2) was located in the negative y-axis region, and Cable 2 (3) was located in the positive y-axis region. Both cables extended from the wind turbine to the seabed. Most of the cable model was buried below the seabed, with no large area exposed.

[0084] Subsequently, riprap protection was arranged according to the results of on-site terrain survey. The riprap protection at this time was a traditional riprap protection method, that is, the riprap was unevenly distributed and higher than the surrounding seabed.

[0085] The topography after 2 hours of scouring is as follows Figure 9As shown in the figure. Under unidirectional flow, scour primarily occurs in the direction away from the pile, exposing Cable 2 (3) and forming a long overhang. Slight scour occurs in the direction facing the pile, exposing Cable 1 (2) only slightly, without forming a long overhang. While the impact of scour is relatively minor, there is still a risk of continued exposure, requiring scour protection to ensure its safety. The negative impact of scouring the cables surrounding the pile foundation cannot be ignored, necessitating appropriate scour protection measures. The experimental results above demonstrate that using traditional riprap methods—those with uneven riprap distribution above the surrounding seabed—can lead to severe edge scour, forming a larger scour pit in the direction away from the pile, exposing a larger area of ​​the cable and forming a long overhang. This leads to severe vibration under the action of the current, increasing the risk of cable damage.

[0086] At this time, the stone bags are arranged according to the arrangement method of the scour protection device of the offshore wind turbine transmission cable in the embodiment above, and then the scour is continued for 6 hours. Figure 10 As shown in the figure, the topographic map was obtained after 8 hours of experiment.

[0087] The experimental results show that: Submarine Cable 1 No. 2, which had previously been slightly scoured, was reburied under the influence of the stone bags that slowed the water flow. It is now safe in place. The stone bags located above the riprap pile remain stable, and a small amount of silt accumulates between the stone bags. Due to the support between the stone bags, there is no risk of the stone bags sliding. Submarine Cable 2 No. 3 is stable in place. Due to the support and fixation of the stone bags, Submarine Cable 2 No. 3 no longer vibrates due to the influence of the water flow after treatment. Sediment continues to accumulate in the area along the cable, and some stone bags are completely buried by sediment. This indicates that the area along the cable has been effectively protected, and has been transformed from a dangerous in-place state to a safe in-place state. In areas where scour pits have formed, the seabed elevation has risen due to the significant effect of the stone bags that backfill the scour pits to promote siltation and fix sand. The area around the cable is also effectively protected.

[0088] In summary, the scour protection device for the offshore wind turbine transmission cable of this embodiment is proven to be effective and can be applied in actual engineering projects. It has important reference significance and engineering value for protecting submarine cables in the event of secondary scour caused by traditional riprap methods.

[0089] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. The scour protection device for the offshore wind turbine transmission cable is characterized by: include: The stone bag group for protecting the submarine cable includes a supporting stone bag group, a limiting stone bag group and a fixed stone bag group formed by a plurality of stone bags. The supporting stone bag group is arranged in the suspended area of ​​the submarine cable, and the supporting stone bag group is located below the submarine cable to support the submarine cable. The limiting stone bag group is located in the suspended area. The stone bags of the limiting stone bag group are located on both sides of the submarine cable to clamp the submarine cable. The fixed stone bag group includes a suspended covering stone bag group and a ground reinforcement stone bag group. The suspended covering stone bag group is located in the suspended area and above the submarine cable to compress the submarine cable. The ground reinforcement stone bag group The reinforcement stone bag group is located in the ground contact area of ​​the submarine cable, the ground contact reinforcement stone bag group includes a T-shaped end stone bag group, the T-shaped end stone bag group includes a circumferentially arranged stone bag group and a compacted stone bag group, the circumferentially arranged stone bag group extends along the circumference of the concentric circle of the pile foundation (1), the compacted stone bag group is arranged above the submarine cable along the extension direction of the submarine cable, the compacted stone bag group is vertically connected to the midpoint of the circumferentially arranged stone bag group, so that the circumferentially arranged stone bag group and the compacted stone bag group are arranged in a T-shape, and the circumferentially arranged stone bag group is farther away from the pile foundation (1) than the compacted stone bag group.

2. The scour protection device for offshore wind turbine outbound cable according to claim 1 is characterized in that: The centers of the stone bags of the fixed stone bag group are located vertically above the submarine cable.

3. The scour protection device for offshore wind turbine outbound submarine cable according to claim 1 is characterized in that: The invention also includes a pile-surrounding flow-disturbing stone bag group formed by arranging a plurality of the stone bags, wherein the pile-surrounding flow-disturbing stone bag group includes a plurality of first stone bag groups arranged along the outer wall curved surface of the pile foundation (1), and a plurality of second stone bag groups arranged along the circumference of the concentric circles of the pile foundation (1), wherein the second stone bag group is close to the first stone bag group.

4. The scour protection device for offshore wind turbine outbound cable according to claim 3 is characterized in that: The area where the pile-surrounding spoiler stone bag group is located includes the horseshoe vortex generating area in front of the pile foundation (1); And / or, the area where the group of spoiler stone bags around the pile is located includes the lateral streamline contraction area of ​​the pile foundation (1); and / or, the area where the pile-surrounding spoiler stone bag group is located includes the rear vortex shedding area of ​​the pile foundation (1); And / or, the vertical projection of the spoiler bag group around the pile covers part of the vertical projection of the area where the submarine cable is located.

5. The scour protection device for offshore wind turbine outbound submarine cable according to claim 3 or 4, characterized in that: It also includes a backfill pit stone bag group formed by arranging multiple stone bags, and the backfill pit stone bag group is used to fill the pit so that the depth of the filled pit is less than the maximum preset scouring depth.

6. The scour protection device for offshore wind turbine outbound cable according to claim 5, characterized in that: The backfill pit stone bag group covers the edge area of ​​the protective submarine cable stone bag group.

7. The scour protection device for offshore wind turbine outbound cable according to claim 5, characterized in that: The top elevation of the backfill scour pit stone bag group is at most flush with the surrounding seabed; And / or, the top elevation of the backfill pit stone bag group is at most flush with the top elevation of the protective submarine cable stone bag group.

8. The scour protection device for offshore wind turbine outbound cable according to claim 5, characterized in that: The elevations of the adjacent stone bags in the cable protection stone bag group, the pile surrounding spoiler stone bag group and the backfill pit stone bag group are smoothly transitioned. And / or, the stone bags at the edge of the protection area where the protective submarine cable stone bag group, the pile-surrounding spoiler stone bag group and the backfill pit stone bag group are located as a whole are one layer, and the stone bags inside the protection area are more than one layer.

9. The scour protection device for offshore wind turbine outbound submarine cable according to claim 5, characterized in that: The vertical projection of the protection area where the protective cable stone bag group, the pile-surrounding spoiler stone bag group and the backfill pit stone bag group are located as a whole is fan-shaped.

10. The scour protection device for offshore wind turbine outbound cable according to claim 5, characterized in that: The stone bags at the bottom of the protective cable stone bag group, the pile-surrounding spoiler stone bag group and the backfill pit stone bag group are closely arranged; And / or, all the stone bags in the group of backfill stone bags are tightly arranged; And / or, all the stone bags in the pile-surrounding spoiler stone bag group are tightly arranged.

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