Pile foundation capable of preventing tensioning of anchor chain and formation of seafloor trench, and implementation method thereof

Abstract

Disclosed are a pile foundation capable of preventing tensioning of an anchor chain and formation of seafloor trenches, and an implementation method thereof. The pile foundation comprises a pile body of a steel pipe pile structure, and an expandable / contractable device disposed at the top of the pile body; the expandable / contractable device comprises a spring, a limiting rod, and a bottom cover and a top cover which are fixed to the upper end of the inner wall of the pile body; one end of the spring is fixed to the bottom cover, and the limiting rod penetrates downwards through the top cover and is fixedly connected to the other end of the spring; the height between the bottom cover and the top cover is greater than the maximum working length of the spring; a fixing ring allowing an anchor chain to pass through is disposed at the upper end of the limiting rod. The present invention can significantly enhance the bearing capacity reserve of an anchoring foundation, effectively slow down or avoid formation of seafloor trenches in front of the anchoring foundation, substantially prolong the service life of the anchoring foundation, and improve the safety of an offshore floating platform anchored by the anchoring foundation.

Description

A pile foundation and implementation method thereof for preventing anchor chain from being stretched and seabed groove from being formed Technical Field

[0001] The present invention relates to the technical field of marine foundation engineering, and in particular to a pile foundation and an implementation method thereof for preventing anchor chains from being stretched and seabed grooves from being formed. Background Art

[0002] An offshore mooring system is a technology that uses multiple anchor foundations and anchor chains to secure floating platforms or ships to the seabed. It overcomes limitations in water depth and distance from shore, improving the stability and safety of offshore floating platforms. Therefore, it is widely used in offshore oil and gas production and offshore wind power. However, during the long-term service of the mooring foundation, its anchor chain will be repeatedly tightened by the wind, waves and current loads in severe weather. On the one hand, the tightened anchor chain will cause the mooring foundation to bear a large uplift load, reducing the safety of the mooring foundation. On the other hand, the anchor chain will not only swing up and down during service, but also sway from side to side. As the anchor chain is repeatedly tightened and cuts the seabed, a clear groove will gradually form in the seabed in front of the foundation. The presence of the seabed groove will change the failure mode of the mooring foundation and greatly reduce the bearing capacity of the mooring foundation. Existing design specifications do not consider the adverse effects of seabed grooves on the mooring foundation, making it difficult to ensure the safety of the mooring foundation in long-term service.

[0003] Summary of the Invention

[0004] Objectives of the invention: The first objective of the present invention is to provide a pile foundation that prevents the anchor chain on the mooring foundation from being stretched and the formation of seabed grooves; the second objective of the present invention is to provide an implementation method of the pile foundation.

[0005] Technical solution: The pile foundation for preventing the anchor chain from being stretched and the formation of seabed grooves described in the present invention includes a pile body, which is a steel pipe pile structure with a telescopic device on the top; the telescopic device includes a spring, a limit rod, and a bottom cover and a top cover fixed to the upper end of the inner wall of the pile body; one end of the spring is fixed to the bottom cover, and the limit rod passes downward through the top cover and is fixedly connected to the other end of the spring; the height between the bottom cover and the top cover is greater than the maximum working length of the spring; the upper end of the limit rod has a fixing ring for the anchor chain to pass through.

[0006] In this invention, the primary functions of the limiter rod are, on the one hand, to transmit vertical force to the spring, and, on the other hand, to limit horizontal sway of the anchor chain. The primary function of the top cover is to transmit the force limiting horizontal sway of the anchor chain to the pile foundation. The primary function of the bottom cover is to transmit the tension exerted on the spring to the pile foundation.

[0007] Furthermore, the depth of the pile body into the soil is determined according to the bearing requirements, where the vertical bearing capacity must be greater than the ultimate tension of the spring, and the horizontal bearing capacity must be able to limit the shaking of the anchor chain.

[0008] Furthermore, the pile diameter is between 0.5 and 2 m.

[0009] Furthermore, the length of the limiting rod should satisfy the requirement that, when the spring reaches its limit working length, the height of the fixing ring is slightly greater than the height of the anchor chain when it is tightened.

[0010] Furthermore, the bottom cover and the top cover are respectively connected to the inner wall of the pile body by welding; the connection between the spring and the bottom cover and the limit rod is made by welding or bolting as needed.

[0011] Furthermore, when the spring limit tension of a single pile foundation does not meet the bearing capacity requirement, a plurality of pile foundations are arranged side by side, and the lengths of the limit rods on the plurality of pile foundations increase successively in the direction away from the anchor foundation.

[0012] By setting up multiple pile foundations under the anchor chain in the landing section, on the one hand, the left and right swing of the anchor chain is restricted, effectively reducing the width of the seabed trench; on the other hand, when the trench expands to a certain extent, the first pile foundation close to the anchor foundation will bear the downward cutting force of the anchor chain, preventing further expansion of the trench.

[0013] Furthermore, the length of each limiting rod is determined according to the angle formed between the anchor chain and the seabed when the anchor chain is tightened and the spacing between the limiting rods.

[0014] Furthermore, the ultimate tension of the spring is determined according to actual conditions and needs to satisfy the requirement that the sum of the ultimate tensions of the springs of the plurality of pile foundations is greater than the upward component of force when the anchor chain is tightened.

[0015] The implementation method of the pile foundation for preventing the anchor chain from being stretched and the formation of seabed grooves described in the present invention includes: after the mooring foundation is installed, the pile foundation is driven below its anchor chain until the depth of the pile foundation in the soil reaches the design requirement, and then the anchor chain of the bed section is passed through the fixing ring.

[0016] Furthermore, when there are multiple pile foundations, the designed number of pile foundations are laid in sequence below the anchor chain at a set interval, with the length of the limiting rods on each pile foundation gradually increasing in the direction away from the anchor foundation; when the depth of the multiple pile foundations into the ground reaches the design requirement, the anchor chain of the implantation section is passed through each fixing ring in sequence.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0018] The present invention utilizes a spring in combination with a limit rod. Under the action of the spring, the limit rod can automatically retract after being pulled up. At the same time, the limit rod is not allowed to be fully pulled up, and has a very high pull-out bearing capacity. The present invention uses the pile foundation below the anchor chain in the landing section to, on the one hand, limit the left and right swing of the anchor chain, effectively reducing the width of the seabed groove. On the other hand, when the groove expands to a certain extent, the pile foundation close to the mooring foundation will bear the force of the anchor chain cutting downward, preventing the groove from further expanding. Therefore, the present invention can significantly increase the bearing capacity reserve of the mooring foundation, effectively slow down or avoid the formation of seabed grooves in front of the mooring foundation, and greatly increase the service life of the mooring foundation and the safety of the offshore floating platform anchored thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a schematic structural diagram of a pile foundation for preventing anchor chain ripping and seabed groove formation, provided by an embodiment of the present application;

[0020] FIG2 is a schematic diagram of the ultimate working state of multiple pile foundations in an embodiment of the present application. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] The reference numerals in Figures 1 and 2 are as follows: 1, pile body; 2, telescopic device; 20, bottom cover; 21, spring; 22, limit rod; 23, top cover; 24, fixing ring; 25, anchor chain; 26, angle.

[0023] As shown in Figure 1, an embodiment of the present application provides a pile foundation that prevents anchor chain ripping and seabed groove formation. The pile foundation comprises a pile body 1, which is a steel pipe pile structure with a telescoping device 2 mounted on top. The diameter of the pile body 1 ranges from 0.5 to 2 meters, selected based on the difficulty of construction. The depth of the pile body 1 buried in the ground is determined by the bearing capacity requirements, with the vertical bearing capacity required to exceed the ultimate tension of the spring 21 and the horizontal bearing capacity required to limit the swaying of the anchor chain 25.

[0024] The telescopic device 2 includes a spring 21, a limiting rod 22, and a bottom cover 20 and a top cover 23 welded to the upper end of the inner wall of the pile body 1. One end of the spring 21 is welded to the bottom cover 20, and the limiting rod 22 extends downward through the top cover 23, with its lower end welded to the other end of the spring 21. The height between the bottom cover 20 and the top cover 23 is greater than the maximum working length of the spring 21. The upper end of the limiting rod 22 has a steel ring-shaped fixing ring 24 for the anchor chain 25 to pass through. The length of the limiting rod 22 is such that when the spring 21 is at its maximum working length, the height of the fixing ring 24 is slightly greater than the height of the anchor chain 25 when it is taut.

[0025] The ultimate tension of spring 21 is determined based on actual conditions and must ensure that the sum of the ultimate tensions of spring 21 across multiple pile foundations is greater than the upward force component when the anchor chain 25 is tightened. Referring to Figure 2 , in this embodiment, three pile foundations are disposed beneath the anchor chain 25 of the mooring foundation. The lengths of the limiting rods 22 on these three pile foundations increase sequentially as they move away from the mooring foundation. Specifically, the length of each limiting rod 22 is determined based on the angle 26 formed between the anchor chain 25 and the seabed when tightened, as well as the spacing between the limiting rods 22. Angle 26 can be roughly determined using inverse trigonometric functions based on the connection point between the anchor chain 25 landing point and the floating platform when tightened, as well as the depth from sea level to the seabed.

[0026] The present application also provides an implementation method of the pile foundation for preventing the anchor chain from being stretched and the formation of seabed grooves, including:

[0027] Referring to Figure 2 , after the mooring foundation is installed, three pile foundations are driven in sequence below its anchor chain 25 at predetermined intervals, with the length of the stop rods 22 on each pile foundation increasing gradually as it moves away from the mooring foundation. When the three pile foundations reach the designed depth, the anchor chain 25 of the implantation section is sequentially threaded through each retaining ring 24, completing the installation.

Claims

1. A pile foundation for preventing the anchor chain from stretching and the formation of seabed grooves, comprising a pile body (1), characterized in that, The pile body (1) is of a steel pipe pile structure, and a telescopic device (2) is provided at the top; the telescopic device (2) includes a spring (21), a limiting rod (22), and a bottom cover (20) and a top cover (23) fixed to the upper end of the inner wall of the pile body (1); one end of the spring (21) is fixed to the bottom cover (20), the limiting rod (22) passes downward through the top cover (23) and is fixedly connected to the other end of the spring (21); the height between the bottom cover (20) and the top cover (23) is greater than the ultimate working length of the spring (21); a fixing ring (24) for the anchor chain (25) to pass through is provided at the upper end of the limiting rod (22).

2. The pile foundation according to claim 1, characterized in that, The penetration depth of the pile body (1) is determined according to the bearing requirements, wherein the vertical bearing capacity needs to be greater than the ultimate tensile force of the spring (21), and the horizontal bearing capacity needs to be able to limit the sway of the anchor chain (25).

3. The pile foundation according to claim 1, characterized in that, The diameter of the pile body (1) is between 0.5 and 2 m.

4. The pile foundation according to claim 1, characterized in that, The length of the limiting rod (22) should be such that when the spring (21) is at its ultimate working length, the height of the fixing ring (24) is slightly greater than the height when the anchor chain (25) is taut.

5. The pile foundation according to claim 1, characterized in that, The bottom cover (20) and the top cover (23) are respectively welded to the inner wall of the pile body (1); the connection modes between the spring (21), the bottom cover (20), and the limiting rod (22) are welded or bolted according to needs.

6. The pile foundation according to any one of claims 1 to 5, characterized in that, When the ultimate tensile force of the spring of a single pile foundation does not meet the bearing capacity requirements, a plurality of the pile foundations are arranged side by side, and the lengths of the limiting rods (22) on the plurality of the pile foundations increase sequentially along the direction away from the mooring foundation.

7. The pile foundation according to claim 6, characterized in that, The length of each limiting rod (22) is determined according to the angle (26) formed by the anchor chain (25) when it is taut and the seabed and the spacing between the limiting rods (22).

8. The pile foundation according to claim 6, characterized in that, The ultimate tensile force of the spring (21) is determined according to the actual situation, and it is required that the sum of the ultimate tensile forces of the springs (21) of the plurality of the pile foundations is greater than the upward component force when the anchor chain (25) is taut.

9. An implementation method of a pile foundation for preventing the anchor chain from stretching and the formation of seabed grooves, characterized in that, Including: After the mooring foundation is installed, the pile foundation according to any one of claims 1 to 8 is driven under its anchor chain (25) until the penetration depth of the pile foundation reaches the design requirement, and then the touchdown section of the anchor chain (25) is inserted into the fixing ring (24).

10. The implementation method according to claim 9, characterized in that, When there are a plurality of the pile foundations, at a set spacing under the anchor chain (25), the pile foundations are driven in sequence in the direction away from the mooring foundation in such a way that the lengths of the limiting rods (22) on each pile foundation increase gradually; after the penetration depths of the plurality of the pile foundations reach the design requirements, the touchdown section of the anchor chain (25) is inserted into each fixing ring (24) in sequence.

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