Suction structure and suction structure penetration method

Abstract

To provide a suction structure and a suction structure penetration method that can reduce the penetration resistance of a skirt portion without disturbing the water bottom ground.SOLUTION: A suction structure 10 with a cylindrical skirt portion 13 is penetrated into the waterbed ground by utilizing the pressure difference between the inside and outside of the skirt portion 13 caused by drainage. The suction structure 10 comprises a lubricant injection mechanism 2 including a lubricant injection port 22 formed on an outer peripheral surface near a bottom end of the skirt portion 13. In a penetration method of the suction structure 10, the lubricant injection mechanism 2 is used to inject lubricant L between the outer peripheral surface of the skirt portion 13 and the waterbed ground, thereby reducing the penetration resistance of the skirt portion 13.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a suction structure capable of reducing the penetration resistance when penetrating the underwater ground and a method for penetrating the suction structure.

Background Art

[0002] As a kind of method for constructing a foundation structure in water, the suction method is known (see, for example, Patent Document 1). In the suction method, a suction structure is used which includes a top plate portion connected to an upper structure such as an offshore windmill and a cylindrical skirt portion extending integrally downward from the top plate portion. With the tip of the skirt portion penetrated into the underwater ground, water is discharged from the region defined by the top plate portion, the skirt portion, and the underwater ground, a suction load is applied, and the suction structure is sunk to a predetermined depth.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when penetrating the suction structure, the penetration resistance of the skirt portion may exceed the penetration force during the process and the penetration may become impossible (the structure may get stuck). If the penetration becomes impossible, the penetration has to be abandoned, the suction structure has to be completely pulled out, and a penetrable location has to be found and penetrated again.

[0005] Patent Document 1 proposes a technique of injecting high-pressure gas toward the underwater ground in contact with the skirt portion to reduce the penetration resistance. However, the method of injecting high-pressure gas or water toward the underwater ground may disrupt the underwater ground and there is a risk that the supporting force after penetration may decrease.

[0006] The present invention has been made in view of such a situation, and an object thereof is to provide a suction structure and a suction structure penetration method that can solve the above-described problems and reduce the penetration resistance of the skirt portion without disturbing the underwater ground.

Means for Solving the Problems

[0007] The suction structure of the present invention is a suction structure including a cylindrical skirt portion, and includes a lubricant injection mechanism formed on an outer peripheral surface near a lower end of the skirt portion and injecting a lubricant between the outer peripheral surface and the underwater ground. Furthermore, in the suction structure of the present invention, the lubricant injection mechanism may include a filter portion that prevents the inflow of sediment into the lubricant injection port. Furthermore, in the suction structure of the present invention, the filter portion may be a check valve including a lid portion 31 biased in a direction to close the lubricant injection port 22. The suction structure penetration method of the present invention is a suction structure penetration method of penetrating a suction structure including a cylindrical skirt portion into an underwater ground using a pressure difference between the inside and outside of the skirt portion due to drainage. The suction structure includes a lubricant injection mechanism including a lubricant injection port formed on an outer peripheral surface near a lower end of the skirt portion, and injects a lubricant between the outer peripheral surface of the skirt portion and the underwater ground using the lubricant injection mechanism to reduce the penetration resistance of the skirt portion. Furthermore, the lubricant used in the suction structure penetration method of the present invention may be a base material having a specific gravity greater than that of water, being water-soluble, and being biodegradable. Furthermore, the lubricant used in the suction structure penetration method of the present invention may be a PAG-based base material.

Effects of the Invention

[0008] According to the present invention, there is an effect that the penetration resistance of the skirt can be reduced without disturbing the underwater ground by injecting the lubricant L using the lubricant injection mechanism 2.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0010] Next, embodiments for carrying out the present invention (hereinafter simply referred to as "embodiments") will be specifically described with reference to the drawings.

[0011] Referring to FIG. 1, the suction structure 10 is a foundation for installing an upper structure 11 such as an offshore windmill on the seabed ground. FIG. 1 shows a state during the penetration of the suction structure 10 into the seabed ground. The seabed ground may be the ground of the sea, or the ground of a lake, a river, etc.

[0012] The suction structure 10 is a cup-shaped housing having a top plate portion 12 connected to the upper structure 11 and a skirt portion 13 integrally extending downward from the top plate portion 12.

[0013] The skirt portion 13 is a cylindrical body integrally extending downward from the outer peripheral edge of the lower end of the top plate portion 12. In the present embodiment, the top plate portion 12 is disk-shaped and the skirt portion 13 is cylindrical. Note that the skirt portion 13 is configured in a shape corresponding to the shape of the top plate portion 12. When the top plate portion 12 is a polygon such as a rectangle, the skirt portion 13 is configured in a polygonal cylindrical shape.

[0014] The suction structure 10 is provided with a lubricant injection mechanism 2. The lubricant injection mechanism 2 includes a lubricant transport pipe 20, a lubricant inlet 21, and a lubricant injection port 22. The lubricant transport pipe 20 is a pipe that transports the lubricant L toward the lower end of the skirt portion 13. The lubricant inlet 21 is an inlet for introducing the lubricant L into the lubricant transport pipe 20. The lubricant injection port 22 is formed on the outer peripheral surface near the lower end of the skirt portion 13, and is an opening for injecting the lubricant L transported by the lubricant transport pipe 20 between the outer peripheral surface and the underwater ground.

[0015] The lubricant injection mechanism 2 is used when the penetration resistance of the skirt portion 13 exceeds the penetration force by suction during penetration and penetration becomes impossible, or when it is assumed in advance that the penetration resistance of the skirt portion 13 exceeds the penetration force by suction. The lubricant L needs to be environmentally friendly without floating on the water surface or the like. As the lubricant L, a PAG (polyalkylene glycol)-based base material having a specific gravity greater than that of water, water solubility, and biodegradability can be used.

[0016] As shown in FIG. 2, a plurality of lubricant injection ports 22 are evenly formed along the outer periphery of the skirt portion 13. FIG. 2 shows the arrangement of the lubricant transport pipe 20 provided on a quarter circumference of the skirt portion 13, and five lubricant transport pipes 20 and five lubricant injection ports 22 are connected to one lubricant inlet 21. Therefore, 20 lubricant injection ports 22 are formed over the entire circumference of the skirt portion 13.

[0017] The slip material injection mechanism 2 may be provided with a filter section that prevents the inflow of sediment into the slip material inlet 22 without impeding the injection of the slip material L. The filter section can be composed of, for example, a non-woven fabric having a porous structure. Also, the filter section may be composed of a check valve 30 as shown in FIG. 3. The check valve 30 includes a lid portion 31 biased in a direction to close the slip material inlet 22 as shown in FIG. 3(a), and prevents the inflow of sediment into the slip material inlet 22. When injecting the slip material L, as shown in FIG. 3(b), a gap is formed between the lid portion 31 and the slip material inlet 22 due to the pressure of the slip material L, and the slip material L is injected through the gap between the lid portion 31 and the slip material inlet 22. Since the slip material L is guided in the circumferential direction of the skirt portion 13 by the lid portion 31, the slip material L can be efficiently injected between the outer peripheral surface of the skirt portion 13 and the underwater ground.

[0018] The number of the slip material inlets 21 and the slip material inlets 22 and the number of the slip material transport pipes 20 can be appropriately set according to the size of the suction structure 10 and the injection amount of the slip material. If the slip material can be injected over the entire circumference of the skirt portion 13, the slip material inlets 22 may be formed at the same depth as shown in FIG. 2, or may be formed at different positions (for example, in a staggered pattern) vertically.

[0019] When the suction structure 10 is a concrete structure and the skirt portion 13 has a predetermined thickness, the slip material transport pipe 20 can be piped inside the skirt portion 13 as shown in FIG. 1. When the suction structure 10 is made of steel or the like and the skirt portion 13 has no predetermined thickness, the slip material transport pipe 20 cannot be piped inside the skirt portion 13. In this case, the slip material transport pipe 20 may be piped on the outer circumference of the skirt portion 13 as shown in FIG. 4(a), or may be piped on the inner circumference of the skirt portion 13 as shown in FIG. 4(b). Considering the penetration resistance, it is desirable to pipe the slip material transport pipe 20 inside the skirt portion 13. Therefore, in the case of a steel suction structure 10, the slip material transport pipe 20 is preferably piped inside the skirt portion 13 having a double pipe structure as shown in FIG. 4(c).

[0020] Next, an example of the penetration method of the suction structure 10 will be described. The installation of the suction structure 10 first involves allowing the skirt portion 13 to penetrate into the underwater ground by applying its own weight with the skirt portion 13 touching the bottom of the underwater ground. When the entire tip of the skirt portion 13 has penetrated into the underwater ground, the interior of the skirt portion 13 becomes a defined region A defined by the top plate portion 12 (lower surface), the skirt portion 13 (inner peripheral surface), and the water bottom surface X.

[0021] The suction structure 10 is provided with a drain pipe 14 that communicates with the defined region A. The drain pipe 14 is used for draining the water within the defined region A (skirt portion 13). By draining the water within the defined region A (skirt portion 13) through the drain pipe 14 using a drainage pump 15, the pressure within the defined region A (skirt portion 13) decreases. The suction structure 10 utilizes the internal and external pressure difference (suction) of the skirt portion 13 as a penetration force to penetrate the skirt portion 13 until the tip reaches the target depth within the underwater ground.

[0022] When the penetration resistance of the skirt portion 13 exceeds the penetration force due to suction, the suction structure 10 cannot penetrate the tip of the skirt portion 13 until it reaches the target depth within the underwater ground and becomes unable to penetrate (stuck).

[0023] When the penetration resistance of the skirt portion 13 exceeds the penetration force due to suction, the penetration resistance of the skirt portion 13 is reduced by injecting a lubricant L using the lubricant injection mechanism 2. The lubricant L is introduced from a lubricant supply device consisting of a pump or the like into the lubricant transport pipe 20 through the lubricant input port 21. The lubricant L introduced into the lubricant transport pipe 20 is injected between the outer peripheral surface of the skirt portion 13 and the underwater ground through the lubricant injection port 22 to reduce the penetration resistance of the skirt portion 13.

[0024] Simultaneously with the injection of the lubricating material L or after the injection, the drain pump 15 is used to drain the water in the defined area A (skirt portion 13) through the drain pipe 14. Due to the drainage, the pressure in the defined area A (skirt portion 13) decreases. The internal and external pressure difference (suction) of the skirt portion 13 due to the drainage also acts as a negative pressure on the underwater ground in the skirt portion 13. Therefore, as shown in FIG. 5, an infiltration flow is generated due to the suction from the underwater ground around the skirt portion 13 toward the underwater ground in the skirt portion 13. The lubricating material L injected between the outer peripheral surface of the skirt portion 13 and the underwater ground infiltrates between the inner peripheral surface of the skirt portion 13 and the underwater ground due to the infiltration flow caused by the suction, further reducing the penetration resistance of the skirt portion 13. When the penetration resistance of the skirt portion 13 by the lubricating material L is lower than the penetration force by the suction, the penetration of the suction structure 10 can be continued.

[0025] As described above, the present embodiment is a suction structure 10 including a cylindrical skirt portion 13, and includes a lubricating material injection mechanism 2 formed on the outer peripheral surface near the lower end of the skirt portion 13 and including a lubricating material injection port 22 for injecting the lubricating material L between the outer peripheral surface and the ground. With this configuration, the suction structure 10 of the present embodiment can reduce the penetration resistance of the skirt without disturbing the underwater ground by injecting the lubricating material L using the lubricating material injection mechanism 2.

[0026] Furthermore, according to the present embodiment, the lubricating material injection mechanism 2 includes a filter portion for preventing the inflow of sediment into the lubricating material injection port 22. With this configuration, the lubricating material injection port 22 is not clogged with sediment, so that the injection of the lubricating material L can be reliably performed.

[0027] Furthermore, according to the present embodiment, the filter portion is a check valve 30 including a lid portion 31 biased in a direction to close the lubricating material injection port 22. With this configuration, the injected lubricating material L is guided in the circumferential direction of the skirt portion 13 by the lid portion 31, so that the lubricating material L can be efficiently injected between the outer peripheral surface of the skirt portion 13 and the underwater ground.

[0028] Moreover, the present embodiment is a suction structure body penetration method for penetrating a suction structure body 10 provided with a cylindrical skirt portion 13 into the seabed ground by using the internal and external pressure difference of the skirt portion 13 due to drainage. The suction structure body 10 includes a lubricant injection mechanism 2 including a lubricant injection port 22 formed on the outer peripheral surface near the lower end of the skirt portion 13. The lubricant L is injected between the outer peripheral surface of the skirt portion 13 and the seabed ground by using the lubricant injection mechanism 2 to reduce the penetration resistance of the skirt portion 13. With this configuration, the suction structure body penetration method of the present embodiment can reduce the penetration resistance of the skirt without disturbing the seabed ground by injecting the lubricant L using the lubricant injection mechanism 2.

[0029] Furthermore, in the present embodiment, the lubricant L is a base material (for example, a PAG-based base material) having a specific gravity greater than that of water, being water-soluble, and being biodegradable. With this configuration, the suction structure body penetration method of the present embodiment can prevent environmental pollution by the lubricant L without the lubricant L floating on the water surface or the like. Since the lubricant L is biodegradable, a decrease in the supporting force after penetration can be prevented.

[0030] As described above, the present invention has been described based on the embodiment. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications are possible in combinations of each of these constituent elements and the like, and such modifications are also within the scope of the present invention.

Explanation of Reference Numerals

[0031] 2 Lubricant injection mechanism 10 Suction structure body 11 Upper structure 12 Top plate portion 13 Skirt portion 14 Drain pipe 15 Drain pump 20 Lubricant transport pipe 21 Lubricant inlet 22 Lubricant injection port 30 Check valve 31 Lid portion A Drawn area L Lubricant Bottom surface of X water

Claims

1. A suction structure having a cylindrical skirt portion, characterized in that it comprises a lubricant injection mechanism formed on the outer peripheral surface near the lower end of the skirt portion and including a lubricant injection port for injecting a lubricant between the outer peripheral surface and the bottom ground. The suction structure according to claim 1, characterized in that the lubricant injection mechanism comprises a filter portion for preventing the inflow of sediment into the lubricant injection port.

2. The suction structure according to claim 2, characterized in that the filter portion is a check valve having a lid portion biased in a direction to close the lubricant injection port.

3.

4. A method for penetrating a suction structure having a cylindrical skirt portion into the bottom ground by using the internal and external pressure difference of the skirt portion due to drainage, characterized in that the suction structure comprises a lubricant injection mechanism including a lubricant injection port formed on the outer peripheral surface near the lower end of the skirt portion, and the lubricant is injected between the outer peripheral surface of the skirt portion and the bottom ground by using the lubricant injection mechanism to reduce the penetration resistance of the skirt portion.

5. The method for penetrating a suction structure according to claim 4, characterized in that the lubricant is a base material having a specific gravity greater than that of water, being water-soluble and biodegradable.

6. The method for penetrating a suction structure according to claim 5, characterized in that the lubricant is a PAG-based base material.

7. The method for penetrating a suction structure according to claim 6, characterized in that the lubricant is a PAG-based base material. ​

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