Multi-chain bidirectional loaded suction anchor foundation structure

Abstract

The invention provides a multi-chain bidirectional load-bearing suction anchor foundation structure which comprises an annular barrel wall, a barrel top cover plate is arranged at the top of the annular barrel wall, an in-barrel reinforcing structure is arranged in the annular barrel wall, a plurality of anchor eye units are arranged on the outer side of the annular barrel wall, and each anchor eye unit comprises anchor eye structures symmetrically arranged on the annular barrel wall. The anchor eye structure in each anchor eye unit is of a double-anchor-eye structure or a single-anchor-eye structure, and the included angles between the adjacent anchor eye structures on the annular barrel wall are equal. The invention provides a one-anchor multi-chain bidirectionally-loaded shared anchoring foundation, the bearing capacity of the anchoring foundation is effectively exerted, the cost of a mooring system is reduced, and a new choice of the anchoring foundation is provided for floating type wind power.

Description

Technical Field

[0001] The present invention relates to the technical field of marine engineering, in particular to a multi-chain bidirectionally loaded suction anchor foundation structure. Background Art

[0002] Energy is the foundation and driving force behind the progress of human civilization. Faced with the current energy crisis and increasingly severe environmental pollution, vigorously developing renewable energy has become a global consensus, with offshore wind power being a key area of ​​focus. In recent years, as offshore diving areas have become relatively well-developed and conflicting uses of the sea for shipping, fishing, and other uses have led to a sharp contraction in exploitable waters, the trend for wind power projects to expand into deeper waters is inevitable. These areas also offer the advantages of higher and more sustainable wind energy production. Compared to submersible fixed wind turbines, floating wind turbines are suitable for use in greater water depths, making them the optimal turbine type for deep offshore waters.

[0003] Unlike traditional offshore fixed wind turbine foundations, floating wind turbine platforms must be connected to seabed anchor foundations via mooring chains to achieve motion restraint. Currently, mainstream floating wind turbines generally use catenary mooring systems. The material and construction costs of these mooring systems can account for one-third of the total construction cost. This makes the design and construction of safe, reliable, and cost-effective anchor foundations a key technical challenge in the development of floating wind farms.

[0004] Existing floating demonstration projects often rely on the traditional single-line mooring scheme for offshore platforms. This involves positioning individual wind turbines via multiple radially distributed anchor chains, each of which requires a separate anchor foundation. Applying this approach directly to large-scale wind farms would result in an exponential increase in the number of anchor foundations, significantly increasing project construction costs. Therefore, developing a shared anchor foundation system has become an essential option for optimizing the layout of floating wind farm arrays.

[0005] Therefore, it is urgent to research and develop a shared anchoring foundation with "one anchor and multiple chains" that can bear bidirectional loads, effectively exert the bearing capacity of the anchoring foundation, reduce the cost of the mooring system, and provide a new option for the anchoring foundation for floating wind power. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention aims to provide a multi-chain, bidirectionally loaded suction anchor foundation structure. This invention provides a shared anchor foundation with "one anchor, multiple chains," bidirectional loading, effectively leveraging the anchor foundation's bearing capacity, reducing mooring system costs, and offering a new anchor foundation option for floating wind turbines.

[0007] An embodiment of the present invention provides a multi-chain bidirectionally loaded suction anchor foundation structure, comprising an annular barrel wall, a barrel top cover plate provided on the top of the annular barrel wall, an inner barrel reinforcement structure provided inside the annular barrel wall, and multiple groups of anchor eye units provided on the outer side of the annular barrel wall. The anchor eye units include anchor eye structures symmetrically arranged on the annular barrel wall, the anchor eye structures in each group of anchor eye units are double anchor eye structures or single anchor eye structures, and the angles between adjacent anchor eye structures on the annular barrel wall are equal.

[0008] In one embodiment, a barrel top reinforcement structure is provided on the upper portion of the barrel top cover plate, and the barrel top reinforcement structure includes:

[0009] Multiple main beams are arranged on the barrel top cover in a cross-shaped orthogonal manner, and the intersection point of each main beam is located at the center of the barrel top cover;

[0010] Multiple reinforcement beams, each reinforcement beam is arranged along the angle bisector of adjacent main beams;

[0011] Multiple layers of annular ribs are arranged at intervals along the radial direction of the barrel top cover to form an annular structure;

[0012] A plurality of radial ribs are arranged between the annular ribs of adjacent layers.

[0013] In one embodiment, a local thickened area is provided on the annular barrel wall in an area connected to the anchor eye structure.

[0014] In one embodiment, the reinforcement structure inside the barrel includes a plurality of main reinforcement plates fixedly connected to the annular barrel wall and the barrel top cover plate. The plurality of main reinforcement plates are arranged in a cross shape, and the intersection line of the plurality of main reinforcement plates is located at the axial center position of the annular barrel wall. A secondary reinforcement plate is connected between the main reinforcement plate and the local thickening area.

[0015] In one embodiment, the single anchor eye structure includes a single anchor eye plate and a single anchor eye reinforcement ring. The single anchor eye plate is arranged perpendicular to the barrel wall, and part of the eye plate penetrates the local thickened area and extends into the interior of the annular barrel wall to be connected to the reinforcement structure inside the barrel. The single anchor eye reinforcement ring is arranged at the anchor eyes on both sides of the single anchor eye plate.

[0016] In one embodiment, the double anchor eye structure includes a double anchor eye plate, double anchor eye reinforcement rings at the anchor eyes on both sides of the double anchor eye plate, and a double anchor eye reinforcement structure. The double anchor eye plate is connected to the local thickening area through the double anchor eye reinforcement structure.

[0017] In one embodiment, the double anchor eye reinforcement structure includes multiple vertical plates and multiple diagonal bracing plates. Multiple vertical plates are connected between the double anchor eye plates and the local thickening area, and the diagonal bracing plates are connected between two adjacent vertical plates.

[0018] In one embodiment, an upper portion of the main reinforcing plate close to the annular barrel wall is hollowed out to form an arc-shaped hole.

[0019] In one embodiment, a water extraction port is provided on the top cover plate of the barrel.

[0020] In one embodiment, two groups of anchor eye units are provided on the outer wall of the annular barrel wall, the anchor eye structure of one group of anchor eye units is a single anchor eye structure, and the anchor eye structure of the other group of anchor eye units is a double anchor eye structure, and the angle between adjacent anchor eye structures on the annular barrel wall is 90°.

[0021] The beneficial effects of the multi-chain bidirectionally loaded suction anchor foundation structure provided by the embodiment of the present invention are:

[0022] 1. The present invention sets a single anchor eye structure and a double anchor eye structure on the annular barrel wall, which can simultaneously suspend six anchor chains in both directions. This breaks through the traditional "one anchor and one chain" structure and forms a shared anchor foundation with multiple chains and bidirectional loads. It can effectively reduce the number of anchor foundations in floating wind farms and reduce construction costs.

[0023] 2. The double anchor eye structure provided in the present invention simultaneously suspends two anchor chains in both directions. When the two anchor chains are subjected to force simultaneously, the loads are effectively offset due to their opposite directions, thereby reducing the force on the suction anchor foundation structure. When the loads are the same, the double anchor eye structure can be regarded as a force-transmitting component. Similarly, the two single anchor eye structures arranged on both sides of the suction anchor are subjected to the same loads.

[0024] 3. The present invention suspends three anchor chains on one side of the annular barrel wall. The three anchor chains are connected to the same floating platform to share the mooring load, reducing the load on each anchor chain and thus reducing the specifications of the anchor chains. At the same time, compared with the "one anchor and one chain" structure, the multi-chain arrangement can effectively exert the bearing capacity of the suction anchor foundation.

[0025] 4. The anchor eye structure of the present invention is an integral forging. A reinforcement ring is provided at the anchor eye, and a local thickened area is provided on the annular barrel wall in the area connected to the anchor eye structure. At the same time, it is connected to form a whole through the reinforcement structure inside the barrel, which can effectively prevent the anchor eye structure from being damaged under long-term cyclic loads and ensure the overall strength and rigidity of the suction anchor foundation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 A schematic diagram of the three-dimensional structure of the suction anchor foundation structure provided by an embodiment of the present invention;

[0028] Figure 2A perspective view of a suction anchor base structure provided by an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of the three-dimensional structure of the internal reinforcement structure provided by an embodiment of the present invention;

[0030] Figure 4 A top view of a suction anchor foundation structure provided by an embodiment of the present invention;

[0031] Figure 5 A side view of a suction anchor foundation structure provided by an embodiment of the present invention;

[0032] Figure 6 for Figure 5 Top view of the CC section;

[0033] Figure 7 for Figure 4 Front view of the AA section;

[0034] Figure 8 for Figure 4 Front view of the middle BB section;

[0035] Figure 9 A schematic diagram of the three-dimensional structure of a single anchor eye structure provided by an embodiment of the present invention;

[0036] Figure 10 A schematic diagram of the three-dimensional structure of a double anchor eye structure provided by an embodiment of the present invention;

[0037] FIG11( a ) is a schematic diagram of the suction anchor foundation structure provided by an embodiment of the present invention completing self-weight penetration;

[0038] FIG11( b ) is a schematic diagram of the suction anchor foundation structure provided by an embodiment of the present invention completing negative pressure penetration;

[0039] FIG11( c ) is a schematic diagram showing the completion of the construction of the suction anchor foundation structure provided by an embodiment of the present invention.

[0040] Figure numerals: 1. Annular barrel wall; 11. Local thickening area; 2. Barrel top cover plate; 21. Water suction port; 3. Barrel top reinforcement structure; 31. Main beam; 311. Lifting ear; 32. Reinforcement beam; 33. Annular rib; 34. Radial rib; 4. Barrel internal reinforcement structure; 41. Main reinforcement plate; 411. Quarter-circular hole; 42. Secondary reinforcement plate; 43. Arc-shaped hole; 5. Single anchor eye structure; 51. Single anchor eye plate; 52. Single anchor eye reinforcement ring; 6. Double anchor eye structure; 61. Double anchor eye plate; 62. Double anchor eye reinforcement ring; 63. Double anchor eye reinforcement structure; 631. Vertical plate; 632. Diagonal support plate. DETAILED DESCRIPTION

[0041] To help those skilled in the art better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the drawings are for illustrative purposes only and are not to be construed as limiting the present invention. To better illustrate the present embodiments, certain components in the drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of actual products. It is understandable that certain well-known structures and their descriptions may be omitted from the drawings. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present invention.

[0042] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0043] like Figure 1 、 Figure 2 、 Figure 5 As shown, a multi-chain bidirectionally loaded suction anchor foundation structure includes an annular barrel wall 1. The annular barrel wall 1 is a steel thin-walled barrel structure. The top of the annular barrel wall 1 is provided with a barrel top cover plate 2 for sealing, and the bottom is open. To ensure the strength and rigidity of the suction anchor foundation structure during operation, an internal barrel reinforcement structure 4 is provided in the annular barrel wall. A plurality of groups of anchor eye units are provided on the outer side of the annular barrel wall 1. The anchor eye units include anchor eye structures symmetrically arranged on the annular barrel wall 1. The anchor eye structures in each group of anchor eye units are single anchor eye structures 5 or double anchor eye structures 6, and the angles between adjacent anchor eye structures on the annular barrel wall 1 are equal.

[0044] In this embodiment, two groups of anchor eye units are provided on the outer wall of the annular barrel wall 1, wherein one group of anchor eye units is two single anchor eye structures 5 symmetrically arranged on the annular barrel wall 1, and the other group of anchor eye units is two double anchor eye structures 6 symmetrically arranged on the annular barrel wall 1. The two groups of anchor eye units are respectively arranged at the barrel wall at a distance of two-thirds of the barrel length from the barrel top cover plate 2, and the angle between adjacent anchor eye structures is 90°.

[0045] In this embodiment, Figure 4 and Figure 6 As shown, three anchor chains can be connected to the left and right sides of the annular barrel wall 1. During operation, the suction anchor is loaded in both directions. Figure 4 The double anchor eye structure 6 on one side of the middle annular barrel wall 1 is connected to an anchor chain on the left and right sides respectively. When the two anchor chains are subjected to force at the same time, the loads can offset each other, thereby reducing the force on the suction anchor foundation. In special circumstances, when the loads on the two anchor chains are the same, the double anchor eye structure 6 is only equivalent to a force transmission component, and the suction anchor does not directly participate in the load bearing. Similarly, the single anchor eye structure 5 on the left and right sides of the annular barrel wall 1 is loaded in the same way; the three anchor chains on each side of the annular barrel wall 1 are connected to the same floating platform and jointly bear the mooring load, which can greatly reduce the load in a single anchor chain and reduce the specifications of the anchor chain. At the same time, the "one anchor multiple chains" type fully mobilizes the bearing capacity of the suction anchor.

[0046] The barrel top cover plate 2 is a thin plate structure. To ensure that it is not damaged or buckled during construction and operation, a barrel top reinforcement structure 3 is provided on the barrel top cover plate 2. The barrel top reinforcement structure 3 includes:

[0047] A plurality of main beams 31 are arranged on the barrel top cover plate 2 in a cross-shaped orthogonal manner, and the intersection of the main beams 31 is located at the center of the barrel top cover plate 2; a plurality of reinforcing beams 32 are arranged along the angle bisector of adjacent main beams 31;

[0048] Multiple layers of annular ribs 33 are arranged at intervals along the radial direction of the barrel top cover plate 2 to form an annular structure; multiple radial ribs 34 are arranged between adjacent layers of annular ribs 33.

[0049] In this embodiment, if Figure 4 As shown, four main beams 31 are arranged perpendicular to each other in a cross shape, and the intersection of the four is located at the center of the barrel top cover plate 2; four reinforcing beams 32 are respectively arranged at the angle bisectors of the angle between two adjacent main beams 31; two layers of annular ribs 33, each layer includes eight annular ribs 33, forming an octagonal annular structure; radial ribs 34 are arranged between two radially adjacent annular ribs 33, and their extended lines pass through the center of the barrel top cover plate 2. There are a total of 8 radial ribs 34.

[0050] In order to facilitate the lifting of the suction anchor foundation during construction, the ends of the four main beams 31 are respectively provided with lifting ears 311, and the lifting ear reinforcement rings are arranged on both sides. Figure 5 shown.

[0051] In order to ensure the strength and rigidity of the anchor eye structure under load, a local thickened area 11 is provided on the annular barrel wall 1 in the area connected to the anchor eye structure. The local thickened area 11 is provided in a rectangular shape.

[0052] like Figure 7 and Figure 8 As shown, in this embodiment, the inner reinforcement structure 4 of the barrel includes four main reinforcement plates 41 fixedly connected to the annular barrel wall 1 and the barrel top cover plate 2. The four main reinforcement plates 41 are arranged in a cross shape, and the intersection line of the four main reinforcement plates 41 is located at the axial center position of the annular barrel wall 1. A secondary reinforcement plate 42 is connected between the main reinforcement plate 41 and the local thickening area 11. Specifically, a secondary reinforcement plate 42 is arranged on both sides of the connection between the local thickening area 11 and the main reinforcement plate 41 inside the annular barrel wall, one end of which is connected to the local thickening area 11, and the other end is connected to the main reinforcement plate 41. The three form a triangular stable structure.

[0053] In this embodiment, in order to prevent the generation of local stress concentration, a quarter-circular hole 411 is opened at the intersection of the main reinforcement plate 41, the annular barrel wall 1 and the barrel top cover plate 2. Figure 7 shown.

[0054] like Figure 6 and Figure 9 As shown, the single anchor eye structure 5 includes a single anchor eye plate 51 and a single anchor eye reinforcement ring 52. The single anchor eye plate 51 is arranged perpendicular to the barrel wall, and part of the eye plate passes through the local thickened area 11 and extends into the interior of the annular barrel wall 1 and is connected to the barrel internal reinforcement structure 4. The single anchor eye reinforcement ring 52 is arranged at the anchor eyes on both sides of the single anchor eye plate 51.

[0055] like Figure 10 As shown, the double anchor eye structure 6 comprises a double anchor eye plate 61, double anchor eye reinforcement rings 62 at the anchor eyes on both sides of the double anchor eye plate 61, and a double anchor eye reinforcement structure 63. The double anchor eye plate 61 is connected to the local thickening area 11 on the annular barrel wall 1 via the double anchor eye reinforcement structure 63. Both the single anchor eye structure 5 and the double anchor eye structure 6 are integrally cast.

[0056] The dual-anchor eye reinforcement structure 63 comprises multiple vertical plates 631 and multiple diagonal bracing plates 632. The vertical plates 631 connect the dual-anchor eye plate 61 to the locally thickened section 11, and diagonal bracing plates 632 connect between adjacent vertical plates 631. Specifically, the present invention includes three vertical plates 631, corresponding to the primary reinforcement plate 41 and secondary reinforcement plate 42 connected to the thickened section 11 of the barrel wall.

[0057] In this embodiment, if Figure 3 As shown, the inner reinforcement structure 4, the local thickened area 11, the two single anchor eye structures 5 and the two double anchor eye structures 6 are connected to form a whole, ensuring that the anchor eye structure is not damaged under the load of the anchor chain.

[0058] like Figure 3 and 7 As shown, the main reinforcing plate 41 is trapezoidal in shape as a whole, and the bottom is designed with an acute angle. In order to reduce the amount of engineering work while ensuring structural safety, an arc-shaped hole 43 is hollowed out at the upper part of the main reinforcing plate 41 near the annular barrel wall.

[0059] In this embodiment, a water pumping port 21 is opened on the barrel top cover plate 2, and a water pumping device is connected through the water pumping port 21, so that the suction anchor foundation structure can continue to pump water after its own weight is completed, forming a negative pressure between the inside and outside of the annular barrel wall, so that the suction anchor foundation structure can complete the sinking under the action of the negative pressure.

[0060] As shown in FIG11 , the specific construction method of this embodiment is as follows:

[0061] After the multi-chain bidirectionally loaded suction anchor foundation structure is completed on land, it is transported as a whole to the designed installation location at sea by a transport ship. After the six anchor chains are connected to the corresponding anchor eye structures and the anchor chains are straightened, a crane is used to lift the suction anchor foundation structure above the water surface to ensure that the suction anchor is perpendicular to the water surface.

[0062] The suction anchor foundation structure is released until it contacts the seabed surface, and then the release speed is slowed down so that the suction anchor foundation structure penetrates the seabed to a certain depth under the action of its own weight, as shown in Figure 11(a).

[0063] After the gravity penetration is stable, the valve of the pumping device is opened to continuously pump water, forming a negative pressure between the inside and outside of the annular barrel wall. Under the action of the negative pressure, the suction anchor foundation structure continues to penetrate the seabed until the barrel top cover 2 is flush with the seabed surface. Then the pumping valve is closed to form a negative pressure inside the annular barrel wall. During the penetration process, the anchor chain also penetrates below the seabed surface, as shown in Figure 11(b).

[0064] After the suction anchor foundation structure is sunk, the six anchor chains are tensioned in sequence to form an anti-catenary segment on the seabed, and the other end of the anchor chain is connected to the floating wind turbine on the sea level, as shown in Figure 11(c).

[0065] According to the description and drawings of the present invention, those skilled in the art can easily manufacture or use the multi-chain bidirectionally loaded suction anchor foundation structure of the present invention, and can produce the positive effects described in the present invention.

[0066] Unless otherwise specified, in the present invention, if there are terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" indicating orientation or positional relationships, they are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the orientation or positional relationship in the present invention are only used for illustrative purposes and cannot be understood as limiting the present invention. For those skilled in the art, the specific meanings of the above terms can be understood in conjunction with the accompanying drawings and according to specific circumstances.

[0067] Unless otherwise specified or limited, the terms "disposed," "connected," and "connected" in this disclosure should be interpreted broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal connections between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on the specific circumstances.

[0068] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A multi-chain bidirectionally loaded suction anchor foundation structure, characterized by: It includes an annular barrel wall, a barrel top cover plate is arranged on the top of the annular barrel wall, an inner barrel reinforcement structure is arranged inside the annular barrel wall, and multiple groups of anchor eye units are arranged on the outer side of the annular barrel wall. The anchor eye units include anchor eye structures symmetrically arranged on the annular barrel wall. The anchor eye structures in each group of anchor eye units are double anchor eye structures or single anchor eye structures, and the angles between adjacent anchor eye structures on the annular barrel wall are equal.

2. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 1, characterized in that: The top of the barrel is provided with a barrel top reinforcement structure on the upper portion of the barrel top cover plate, and the barrel top reinforcement structure includes: Multiple main beams are arranged on the barrel top cover in a cross-shaped orthogonal manner, and the intersection point of each main beam is located at the center of the barrel top cover; Multiple reinforcement beams, each reinforcement beam is arranged along the angle bisector of adjacent main beams; Multiple layers of annular ribs are arranged at intervals along the radial direction of the barrel top cover to form an annular structure; A plurality of radial ribs are arranged between the annular ribs of adjacent layers.

3. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 1, characterized in that: A local thickened area is provided in the area where the annular barrel wall is connected to the anchor eye structure.

4. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 1, characterized in that: The reinforcement structure inside the barrel includes multiple main reinforcement plates fixedly connected to the annular barrel wall and the barrel top cover plate. The multiple main reinforcement plates are arranged in a cross shape, and the intersection line of the multiple main reinforcement plates is located at the axis of the annular barrel wall. Reinforcement plates are connected between the main reinforcement plates and the local thickening area.

5. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 3, characterized in that: The single anchor eye structure includes a single anchor eye plate and a single anchor eye reinforcement ring. The single anchor eye plate is arranged perpendicular to the barrel wall, and part of the eye plate penetrates the local thickened area and extends into the interior of the annular barrel wall to be connected to the reinforcement structure inside the barrel. The single anchor eye reinforcement ring is arranged at the anchor eyes on both sides of the single anchor eye plate.

6. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 3, characterized in that: The double anchor eye structure comprises a double anchor eye plate, double anchor eye reinforcement rings at the anchor eyes on both sides of the double anchor eye plate, and a double anchor eye reinforcement structure. The double anchor eye plate is connected to the local thickening area through the double anchor eye reinforcement structure.

7. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 6, characterized in that: The double anchor eye reinforcement structure includes multiple vertical plates and multiple diagonal bracing plates. The multiple vertical plates are connected between the double anchor eye plates and the local thickening area, and the diagonal bracing plates are connected between two adjacent vertical plates.

8. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 4, characterized in that: The upper portion of the main reinforcing plate is hollowed out near the annular barrel wall to form an arc-shaped hole.

9. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 1, characterized in that: A water extraction port is provided on the barrel top cover.

10. The multi-chain bidirectionally loaded suction anchor foundation structure according to claim 1, characterized in that: Two groups of anchor eye units are arranged on the outer wall of the annular barrel wall. The anchor eye structure of one group of anchor eye units is a single anchor eye structure, and the anchor eye structure of the other group of anchor eye units is a double anchor eye structure. The angle between adjacent anchor eye structures on the annular barrel wall is 90°.

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