Caisson type gravity anchor and construction method thereof

Abstract

The invention discloses a caisson type gravity anchor and a construction method thereof, the caisson type gravity anchor comprises a caisson main body, the side wall of the caisson main body is provided with a water inlet hole, the water inlet hole is located below a waterline when the caisson main body is placed in the sea, and the water inlet hole is blocked by a detachable plug. The construction method of the caisson type gravity anchor is used for installing the caisson type gravity anchor and comprises the steps that S1, pre-assembling is conducted, the water inlet hole is blocked, and the sealing performance of the lower portion of the caisson body is checked and ensured; s2, positioning installation is conducted, specifically, the caisson body which is pre-assembled in the step S1 floats on the sea surface to be transported, and after the caisson body is transported to a preset position, a water inlet hole is opened to enable the caisson body to sink; and S3, backfilling operation is conducted, specifically, a high-density material is backfilled into an inner cavity of the caisson body through a conveying pipe and used for enhancing the counterweight effect of the caisson and improving the anti-pulling capacity.

Description

Technical Field

[0001] This application relates to the technical field of underwater structure construction for offshore wind power and photovoltaic technologies, and particularly relates to a caisson-type gravity anchor and its construction method. Background Art

[0002] With the development of offshore renewable energy, floating wind power and photovoltaic platforms have become important power generation methods in the deep and far sea areas. These floating structures require reliable anchoring systems to resist the actions of wind, waves, and currents in the marine environment and ensure the long-term stability of the platforms. Currently, common anchoring methods include drag anchors, suction anchors, pile anchors, and gravity anchors, etc. Among them, drag anchors and suction anchors are suitable for soft seabeds, but their anchoring efficiency may be limited in hard seabeds or complex geological conditions. Pile anchors can provide high bearing capacity, but have high construction costs and strict requirements for seabed geological conditions. As a passive anchoring system, a gravity anchor relies on the downward pressure provided by its own weight and the friction force with the seabed foundation to resist the buoyancy and external forces of the floating platform. However, traditional gravity anchors usually adopt large-volume concrete or steel structures, with complex installation processes, long construction periods, and poor adaptability in deeper waters. In addition, affected by waves and currents, conventional gravity anchors may face a greater risk of slip, affecting their long-term stability. Therefore, there are still many technical challenges in the application of existing gravity anchor structures in deep and far sea floating platforms. In order to improve the anchoring efficiency and construction convenience of the gravity anchor system, it is urgent to develop a new type of gravity anchor structure that is efficient, stable, and reliable, so as to reduce the amount of offshore operations during the construction process, lower the installation cost, and enhance the adaptability of the anchoring system in complex seabed environments, thereby providing a safer and more reliable anchoring solution for offshore floating wind power and photovoltaic platforms. Summary of the Invention

[0003] The purpose of the present invention is to provide a caisson-type gravity anchor and its construction method, and the specific technical solutions are as follows: A caisson-type gravity anchor includes a caisson main body. Water inlet holes are provided on the side wall of the caisson main body. The water inlet holes are located below the waterline when the caisson main body is placed in the sea, and the water inlet holes are blocked by detachable plugs. Anti-slip sawteeth are provided around the bottom of the caisson main body to enhance the horizontal anti-slip ability of the caisson main body. Anti-slip piles extend downward from the bottom of the caisson main body. Mounting holes are provided at the four corners of the top of the caisson main body for installing anchor chains. It also includes a cover plate that covers the caisson main body to make the caisson main body completely sealed during transportation.

[0004] A construction method for caisson gravity anchors, used for installing the above-mentioned caisson gravity anchors, includes: S1. Prefabrication and assembly, plugging the water inlet holes, inspecting and ensuring the tightness of the lower part of the caisson main body; S2. Positioning and installation, floating the caisson main body after prefabrication and assembly in S1 on the sea surface for transportation, and after arriving at the preset position, removing the cover plate and opening the water inlet holes to sink the caisson main body; S3. Backfilling operation, using a conveying pipe to backfill high-density materials into the internal cavity of the caisson main body to enhance the counterweight effect of the caisson and improve the uplift resistance. In S2, after opening the water inlet holes, a vertical pulling force is provided for the caisson main body to slowly sink and achieve precise positioning. After completing the backfilling operation in S3, riprap is thrown around the caisson main body to form a stable bottom protection layer to prevent erosion damage to the foundation caused by seabed scouring. When throwing riprap, the throwing range covers the caisson main body. Used for installing the upper caisson gravity anchor, characterized in that the prefabrication and assembly in S1 includes installing the cover plate, inspecting and ensuring the tightness of the entire caisson main body.

[0005] Aiming at the problems of difficult operation in the transportation and hoisting process of the gravity anchoring structure in the prior art, insufficient bearing capacity in the soft seabed environment, limited anti-slip ability, and being easily affected by ocean current scouring during long-term service, the present invention innovatively proposes a composite gravity anchor structure combining a caisson, an anti-sliding pile assembly and anti-sliding shear teeth, and an optimized construction and installation strategy is proposed accordingly.

[0006] In the transportation stage, the present invention makes full use of the self-floating characteristics of the caisson structure, and the anchor body can be transported to the predetermined sea area by tugboat towing, without relying on complex large-scale hoisting equipment, significantly reducing the construction difficulty and cost. In the construction stage, multiple pile legs arranged at the bottom of the caisson can actively penetrate into the seabed soil body, providing additional uplift and anti-overturning capabilities while the caisson self-weight is pressed in, significantly improving the overall anchoring stability and anti-slip performance of the anchor body.

[0007] In addition, an anti-sliding shear tooth structure arranged orthogonally is provided at the bottom of the caisson, which can effectively resist random ocean loads from different directions and further enhance the multi-directional bearing capacity. The cable or anchor chain is connected to the caisson anchor body through connection rings evenly arranged at the four corners of the top of the caisson to ensure that the anchor body is evenly stressed in the marine environment, thereby improving its long-term service stability under the action of random ocean loads. This application adopts the construction method of caisson floating transportation - precise positioning - sinking and penetration fixation - riprap for increasing counterweight. First, the initial stable positioning is realized by using the self-weight of the caisson, and then the anti-sliding piles penetrate into the seabed, effectively improving the construction accuracy and adaptability without relying on large-scale pile driving equipment.

[0008] During the insertion process of the anti-sliding piles, their symmetric layout ensures uniform structural stress, significantly suppressing the horizontal displacement and tilting risk of the caisson under external loads such as waves and tides, and ensuring that the foundation remains in a stable posture for a long time. By precisely controlling the embedment depths of the caisson and the pile legs, and implementing a riprap bottom protection measure around the caisson, the present invention effectively reduces the influence of long-term scouring, significantly enhancing the scouring resistance and service life of the structure. This structural solution combines the advantages of the rapid deployment of the caisson gravity anchor and the high load-bearing characteristics of the pile foundation, not only improving the anchoring performance, but also simplifying the construction process and reducing the total project cost. Compared with traditional single gravity or pile foundations, the present invention exhibits significant technical advantages in terms of bearing capacity, anti-sliding ability, anti-scouring performance, and construction adaptability, and is particularly suitable for new floating wind power, photovoltaic platform and other offshore engineering mooring systems in soft sedimentary environments, providing an efficient, reliable and economical anchoring solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic structural diagram of the structure without a cover plate in this application; Figure 2 It is a schematic structural diagram of the structure with a cover plate in this application; Wherein: 1 - caisson main body, 2 - anti-sliding pile, 3 - anti-slip sawtooth, 4 - mounting hole, 5 - connecting ring, 6 - connecting cable chain, 7 - anchor chain, 8 - water inlet hole, 9 - cover plate. SPECIFIC EMBODIMENTS

[0010] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0011] A caisson-type gravity anchor includes a caisson main body 1, and a water inlet hole 8 is provided on the side wall of the caisson main body 1. The water inlet hole 8 is located below the draft line when the caisson main body 1 is placed in the sea, and the water inlet hole 8 is blocked by a detachable plug. In actual use, the caisson main body 1 can be set as a reinforced concrete structure with a hollow cavity, having a large buoyancy so that the device can float on the sea surface and is transported to the installation sea area by a tugboat or a power device. The water inlet hole 8 is provided at the middle and lower part of the caisson cavity, and a blocking measure is adopted during the transportation and floating stages to prevent seawater from entering, and it is opened again during the sinking operation stage of the caisson anchor for injecting water into the cavity. The water inlet hole 8 is a hole opened at the middle and lower part of the caisson cavity, and the size is generally 50 - 200 mm (such as 50 mm, 100 mm, 150 mm, 200 mm and the interval values between any two end points).

[0012] Anti-slip sawteeth 3 are provided around the bottom of the caisson main body 1 to enhance the horizontal anti-slip ability of the caisson main body 1. In actual use, the anti-slip sawteeth 3 can be set as a serrated structure evenly and continuously arranged on the bottom surface of the caisson main body 1, and are divided into two groups arranged orthogonally, and can be integrally cast with the caisson main body 1 by reinforced concrete. This anti-slip sawtooth 3 structure can effectively enhance the horizontal anti-slip ability of the bottom of the caisson anchor body and improve the overall stability of the anchoring system. Through the orthogonal arrangement of the shear teeth, the caisson main body 1 can resist random ocean loads from different directions at the same time, significantly improving its multi-directional bearing performance.

[0013] Anti-slip piles 2 are provided extending downward from the bottom of the caisson main body 1. In actual use, the anti-slip piles 2 can be set as a steel-made hollow structure and pre-embedded at the bottom of the caisson main body 1 during the casting of the caisson main body 1. When the caisson main body 1 sinks to the seabed surface during the construction process, the anti-slip piles 2 can be inserted into the seabed soil to further improve the vertical and horizontal bearing capacities. The number of anti-slip piles 2 is 4 - 8. Each pile leg can be inserted into the seabed soil under the action of the self-weight of the box body during the structural installation process to prevent the caisson from sliding or overturning. The pile leg diameter is generally 300 - 600 mm (such as 300 mm, 400 mm, 500 mm, 600 mm and the interval values between any two end points); the wall thickness range is 10 - 50 mm (such as 10 mm, 30 mm, 50 mm and the interval values between any two end points). The specific length, pipe diameter and wall thickness need to be determined through numerical simulation analysis in combination with the characteristics of the seabed soil, the designed penetration depth and the bearing capacity requirements.

[0014] Installation holes 4 are provided at the four corners of the top of the caisson main body 1 for installing the anchor chain 7. In actual use, the installation holes 4 can be connected to an integral steel connecting ring 5, and the connecting ring 5 is pre-embedded at the four corners of the top of the caisson main body 1 for connecting the mooring anchor chain 7. Four connecting cables 6 are connected to the installation holes 4 through the connecting ring 5, and converge into a bundle at the other end and are connected to the anchor chain 7. This connection method can make the four corners of the top of the caisson body evenly stressed, effectively improving the overall stability and long-term service performance of the anchor body under the action of random ocean direction loads. The connecting cable 6 can be selected from cast iron cables or fiber-reinforced polymer composite cables.

[0015] It also includes a cover plate 9 that covers the caisson main body 1 to make the caisson main body 1 completely airtight during transportation. In actual use, the cover plate 9 can be set as an impermeable airtight plate, which can be made of the same material as the caisson anchor main body, or other waterproof plates can also be selected, and is covered on the top of the caisson main body 1 to ensure the watertightness of the caisson cavity.

[0016] A construction method for a caisson gravity anchor is used to install the above-mentioned caisson gravity anchor, including: S1. Pre-assembly: Plug the water inlet hole 8, and check and ensure the tightness at the lower part of the caisson body 1. Specifically, complete the prefabrication and assembly work of the caisson body 1 and the anti-sliding pile 2 on shore, and check the structural integrity and anti-corrosion treatment of all connection joints. Ensure that the installation direction of the anti-sliding pile 2 is vertical, the lengths are consistent, and the overall structure is kept horizontal. Install the connecting ring 5, the connecting cable chain 6 and the anchor chain 7 on the installation hole 4. Completely cover the caisson body with the cover plate 9. Closely block the water inlet hole 8 with a waterproof plug. Connect the free end of the anchor chain 7 to the installation ship deck or the anchor buoy.

[0017] S2. Positioning and installation: Float the caisson body 1 after pre-assembly in S1 on the sea for transportation. After arriving at the preset position, remove the cover plate and open the water inlet hole 8 to sink the caisson body 1. After opening the water inlet hole 8, provide a vertical pulling force for the caisson body 1 to slowly sink it for accurate positioning. Specifically, float the caisson anchor structure on the sea and transport it to the designated sea area by a tugboat or other power devices. Use the hoisting mechanism on the installation ship to remove the cover plate 9 and pull out the plug of the water inlet hole 8 to allow seawater to continuously flow into the cavity of the caisson body 1. When enough seawater enters the caisson body 1, the whole anchor body structure starts to sink. At this time, it is necessary to use the hoisting rope on the installation ship to connect the anchor chain 7 and provide a certain upward pulling force, so that the caisson gravity anchor slowly sinks at a uniform speed until the bottom of the caisson body 1 evenly contacts the seabed surface. At this time, the anti-sliding pile 2 is inserted into the seabed under the action of the caisson weight to maintain the stability of the structure. The insertion depth of the pile legs is usually controlled within 0.5 - 1.0 m (such as 0.5 m, 0.75 m, 1.0 m and the interval values between any two end points), specifically depending on the local geological conditions and the structural bearing design.

[0018] S3. Backfilling operation: Use a conveying pipe to backfill the inner cavity of the caisson body 1 with high-density materials to enhance the caisson counterweight effect and improve the anti-pulling ability. Specifically, use the gravel conveying pipeline or sandbag throwing on the installation ship to throw gravel or high-density gravel materials into the inner cavity of the caisson body 1. The filling materials should meet certain particle size and density requirements to enhance the caisson counterweight effect and improve the anti-pulling ability. It is recommended to use underwater conduit feeding and backfill layer by layer until the entire inner cavity is filled.

[0019] After the backfilling operation in S3 is completed, riprap is placed around the caisson main body 1 to form a stable bottom protection layer to prevent erosion damage to the foundation caused by seabed scouring. When placing the riprap for bottom protection, the riprap range covers the caisson main body 1. It is used for installing the upper caisson type gravity anchor, and is characterized in that the pre-assembly in S1 includes installing the cover plate 9, inspecting and ensuring the overall sealing of the caisson main body 1. Specifically, to further improve the anti-scouring performance of the structure, it is necessary to carry out the riprap operation for bottom protection around the outside of the caisson gravity anchor. The riprap range should cover the caisson edge area. Well-graded anti-scouring stones are selected and placed in layers to form a stable bottom protection layer to prevent erosion damage to the foundation caused by seabed scouring. The riprap range should cover 0.5 to 1 times the caisson length of the extension around the caisson, and the thickness is adjusted according to the seabed scouring prediction results, usually not less than 0.5 m. After the caisson backfilling and bottom protection are completed, adjust the length and tension of the anchor chain 7 to make it reach the designed pre-tightening state to ensure the balance of the platform mooring force. Subsequently, set up the positioning buoy at the end of the anchor chain 7 and record the installation data to complete the installation operation of the entire anchoring system.

Claims

1. A caisson-type gravity anchor, characterized in that, It includes a caisson main body (1). An inlet hole (8) is provided on the side wall of the caisson main body (1). The inlet hole (8) is located below the waterline when the caisson main body (1) is placed in the sea, and the inlet hole (8) is blocked by a detachable plug.

2. The caisson gravity anchor according to claim 1, characterized in that, Anti-slip sawteeth (3) are provided around the bottom of the caisson main body (1) to enhance the horizontal anti-slip ability of the caisson main body (1).

3. The caisson gravity anchor according to claim 1, wherein, Anti-slip piles (2) extend downward from the bottom of the caisson main body (1).

4. The caisson gravity anchor according to claim 1, wherein, Mounting holes (4) are provided at the four corners of the top of the caisson main body (1) for mounting an anchor chain (7).

5. The caisson gravity anchor according to claim 1, characterized in that, It further includes a cover plate (9). The cover plate (9) covers the caisson main body (1) to make the caisson main body (1) completely sealed during transportation.

6. A construction method for a caisson gravity anchor, which is used to install the caisson gravity anchor as described in claims 1-5, characterized in that, It includes: S1. Pre-assembly: Block the inlet hole (8), check and ensure the tightness of the lower part of the caisson main body (1); S2. Positioning and installation: Float the caisson main body (1) completed in pre-assembly in S1 on the sea surface for transportation. After arriving at the preset position, remove the cover plate (9) and open the inlet hole (8) to make the caisson main body (1) sink; S3. Backfilling operation: Use a conveying pipe to backfill high-density materials into the internal cavity of the caisson main body (1) to enhance the counterweight effect of the caisson and improve the anti-pulling ability.

7. The construction method of the caisson gravity anchor according to claim 6, characterized in that, In S2, after opening the inlet hole (8), a vertical pulling force is provided for the caisson main body (1) to make the caisson main body (1) sink slowly to achieve precise positioning.

8. The construction method of the caisson gravity anchor according to claim 6, characterized in that, After completing the backfilling operation in S3, riprap is carried out around the caisson main body (1) to form a stable riprap layer to prevent erosion damage to the foundation caused by seabed scouring.

9. The construction method of the caisson gravity anchor according to claim 8, wherein, When carrying out riprap, the riprap range covers the caisson main body (1).

10. The caisson gravity anchor construction method according to claim 6, which is used for installing the caisson gravity anchor according to claim 5, is characterized in that, The pre-assembly in S1 includes installing the cover plate (9), checking and ensuring the overall tightness of the caisson main body (1).

Images