Suction foundation

Abstract

To provide a suction foundation capable of reducing penetration resistance even when a stringer is attached.SOLUTION: A suction foundation 100 is provided with: a foundation body 10 having a ceiling wall 11 and a side peripheral wall 12 extending downward from the ceiling wall 11 to be penetrated into the underwater ground G; and plate-like stringers 2 extending inside of the peripheral wall 12 from an inner surface 17 of the peripheral wall 12 and from an upper direction to the lower direction. A width W of the stringer 2 in a direction from the inner surface 17 of the peripheral wall 12 to the inner side of the peripheral wall 12 becomes smaller from the upper direction to the lower direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed herein relates to a suction foundation. [Background technology]

[0002] Patent Document 1 discloses a suction foundation that is installed on underwater ground. The suction foundation has a top plate and a skirt that extends downward from the outer periphery of the top plate. The skirt of the suction foundation is inserted into the ground. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7052559 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to prevent the skirt from buckling during penetration of the suction foundation, a vertical beam extending downward is sometimes attached to the inner surface of the skirt. The vertical beam increases the strength of the skirt. However, in a suction foundation with a vertical beam attached, the contact area with the ground increases compared to a suction foundation without a vertical beam attached, and there is a risk that the penetration resistance from the ground will increase.

[0005] The technology disclosed herein has been made in consideration of these points, and its purpose is to reduce the penetration resistance even when stringers are attached. [Means for solving the problem]

[0006] The suction foundation disclosed herein comprises a foundation body having a ceiling wall and a side wall extending downward from the ceiling wall and penetrating into the underwater ground, and plate-shaped vertical beams extending from the inner surface of the side wall to the inside of the side wall and from above to below, and the width of the vertical beams, which is the dimension in the direction extending from the inner surface of the side wall to the inside of the side wall, becomes smaller as it goes from above to below. Effect of the Invention

[0007] It is possible to reduce the penetration resistance even when stringers are installed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic diagram of a suction foundation in an installed state. [Diagram 2] FIG. 2 is a cross-sectional view of the peripheral side wall. [Diagram 3] FIG. 3 is a longitudinal cross-sectional view of a stringer. [Figure 4] FIG. 4 is an explanatory diagram showing the suction foundation before the penetration process. [Diagram 5] FIG. 5 is an explanatory diagram showing a state in which the foundation main body has reached the ground in the penetration step. [Figure 6] FIG. 6 is an explanatory diagram showing a state in which the foundation body is penetrated into the ground by a suction load. [Figure 7] FIG. 7 is an explanatory diagram showing the pressure distribution acting on the side peripheral wall of the suction foundation. [Figure 8] FIG. 8 is an explanatory diagram showing a shear force diagram of a cantilever beam. [Figure 9] FIG. 9 is a vertical cross-sectional view of a stringer according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Exemplary embodiments will now be described in detail with reference to the accompanying drawings.

[0010] Fig. 1 is an explanatory diagram showing a schematic diagram of a suction foundation 100 installed. The suction foundation 100 is a foundation for installing a structure on or underwater, and is sunk into underwater ground G. In the example of Fig. 1, the suction foundation 100 is a foundation for installing a wind turbine 9 on the water. The suction foundation 100 comprises a foundation body 10 and vertical beams (i.e., vertical ribs) 2 arranged inside the foundation body 10 and attached to the foundation body 10.

[0011] The foundation body 10 is formed in a container shape with a closed upper end and an open lower end. The foundation body 10 has a ceiling wall 11 and a peripheral side wall 12 that extends downward from the ceiling wall 11 and penetrates into the ground G. The ceiling wall 11 and the peripheral side wall 12 are formed of, for example, steel plates.

[0012] The ceiling wall 11 is formed in a substantially disk-like shape extending horizontally. A support pillar 13 is disposed on the ceiling wall 11. The support pillar 13 is disposed at the center of the ceiling wall 11 and extends upward from the ceiling wall 11. The wind turbine 9 is installed on the support pillar 13.

[0013] The side peripheral wall 12 is formed in a generally cylindrical shape extending in the vertical direction. The upper end of the side peripheral wall 12 is connected to the peripheral edge of the ceiling wall 11. The ceiling wall 11 and the side peripheral wall 12 define an internal space 15 of the foundation body 10.

[0014] In this example, the foundation body 10 further defines a filling space 16 into which the filling material 5 is filled when the side peripheral wall 12 penetrates into the ground G. That is, the filling space 16 is a space defined by the ceiling wall 11, the side peripheral wall 12, and the ground G. The filling space 16 is a part of the internal space 15. When the filling material 5 filled in the filling space 16 hardens, the load of the foundation body 10 may act appropriately on the ground G via the filling material 5.

[0015] A frictional force acts on the side peripheral wall 12 that penetrates into the ground G. This firmly fixes the suction foundation 100 to the ground G. In addition, when an external force acts on the suction foundation 100, negative pressure is generated inside the foundation body 10, increasing the pull-out resistance. This ensures the stability of the suction foundation 100.

[0016] A drain pipe 31 is provided in the foundation body 10. The drain pipe 31 is a pipe for forcibly draining water inside the foundation body 10. The drain pipe 31 is connected to the internal space 15 at the ceiling wall 11. A drain hole 41 is formed penetrating the ceiling wall 11. The drain pipe 31 is connected to the drain hole 41. In other words, the drain pipe 31 communicates with the internal space 15 via the drain hole 41. A valve 32 is provided at an upper portion of the drain pipe 31 (specifically, a portion above the water surface). The valve 32 switches the drain pipe 31 between open and closed.

[0017] A drainage pump 33 is connected to the drainage pipe 31. Operation of the drainage pump 33 causes water inside the foundation body 10 to be discharged to the outside of the foundation body 10 via the drainage pipe 31. The drainage pipe 31 is used when the foundation body 10 penetrates into the ground G. Draining water through the drainage pipe 31 promotes penetration of the foundation body 10 into the ground G.

[0018] A water supply pipe 34 is provided in the foundation body 10. The water supply pipe 34 is a pipe for supplying water to the inside of the foundation body 10 when the suction foundation 100 is removed. A water supply hole 42 is formed penetrating the ceiling wall 11. The water supply pipe 34 is connected to the water supply hole 42. In other words, the water supply pipe 34 communicates with the internal space 15 via the water supply hole 42. A valve 35 is provided at the upper part of the water supply pipe 34 (specifically, the part above the water surface). The valve 35 switches the water supply pipe 34 between open and closed.

[0019] A water supply pump 36 is connected to the water supply pipe 34. When the water supply pump 36 is operated, water is supplied to the inside of the foundation body 10 via the water supply pipe 34. The water supply pipe 34 is used when removing the suction foundation 100. Supplying water via the water supply pipe 34 promotes the floating of the foundation body 10 from the ground G.

[0020] The vertical beams 2 reinforce the side peripheral walls 12. Specifically, the vertical beams 2 prevent deformation such as buckling of the side peripheral walls 12 that may occur during and after the penetration of the suction foundation 100. The vertical beams 2 are plate-shaped having width, thickness, and length directions. The vertical beams 2 are formed of, for example, steel plates. The vertical beams 2 are attached to the foundation body 10 by, for example, welding.

[0021] FIG. 2 is a cross-sectional view of the side peripheral wall 12. Specifically, FIG. 2 is a cross-sectional view of the side peripheral wall 12 cut along a plane perpendicular to the axis C. FIG. 3 is a vertical cross-sectional view of the vertical beam 2. Specifically, FIG. 3 is a cross-sectional view of the vertical beam 2 cut along a plane perpendicular to the thickness direction. The vertical beam 2 extends from the inner surface 17 of the side peripheral wall 12 toward the inside of the side peripheral wall 12 and from above to below. In this example, the vertical beam 2 extends from the inner surface 17 of the side peripheral wall 12 toward the axis C of the side peripheral wall 12. An end surface 21 on one side in the width direction of the vertical beam 2 is connected to the inner surface 17 of the side peripheral wall 12. The vertical beam 2 extends from the lower surface 18 of the ceiling wall 11 to the lower end 19 of the side peripheral wall 12. In this example, the position of the lower end 25 of the vertical beam 2 is approximately coincident with the position of the lower end 19 of the side peripheral wall 12. The length direction of the vertical beam 2 is approximately parallel to the axis C. The upper end 22 of the vertical beam 2 is connected to the lower surface 18 of the ceiling wall 11. However, this is not limited to this, and the vertical beam 2 may extend from the lower surface 18 of the ceiling wall 11 to a position higher than the lower end 19 of the side peripheral wall 12. In other words, the lower end 25 of the vertical beam 2 may be located higher than the lower end 19 of the side peripheral wall 12.

[0022] 2, a plurality of, specifically, three or more, vertical beams 2 are attached to the inner surface 17 of the side peripheral wall 12. Preferably, five or more vertical beams 2 are attached to the inner surface 17 of the side peripheral wall 12. In this example, nine vertical beams 2 are attached to the inner surface 17 of the side peripheral wall 12. The multiple vertical beams 2 are arranged at equal intervals in the circumferential direction of the side peripheral wall 12.

[0023] As shown in FIG. 3, the width W of the vertical beam 2, which is the dimension in the direction extending from the inner surface 17 of the side peripheral wall 12 to the inside of the side peripheral wall 12, becomes smaller from the top to the bottom. In other words, the vertical beam 2 has a tapered shape in the direction from the top to the bottom. More specifically, at least in the portion of the vertical beam 2 that penetrates into the ground G, the width W becomes smaller from the top to the bottom. In this example, the width W becomes smaller from the top to the bottom over the entire vertical direction of the vertical beam 2. In other words, the rate of change of the width W in the direction from the top to the bottom is negative.

[0024] More specifically, the first derivative of the rate of change of the width W in the direction from top to bottom is positive. In other words, the "first derivative of the rate of change of the width W" is the second derivative of the function W=f(L) when the distance from the lower surface 18 of the ceiling wall 11 is L. That is, the positive first derivative of the rate of change of the width W means that the shape of the inner edge 23 of the vertical beam 2 is a downwardly convex curve when the side peripheral wall 12 is the horizontal axis in FIG. 3. The inner edge 23 refers to the edge closer to the axis C of the side peripheral wall 12 among both ends of the vertical beam 2 in the width direction. It is preferable that the first derivative of the rate of change of the width W is positive and constant. More specifically, the shape of the inner edge 23 of the vertical beam 2 is a quadratic or higher curve. More preferably, the shape of the inner edge 23 of the vertical beam 2 is a cubic or higher curve.

[0025] Next, a method for installing the suction foundation 100 will be described. Fig. 4 is an explanatory diagram showing the suction foundation 100 before the penetration step. Fig. 5 is an explanatory diagram showing the state in which the foundation body 10 has reached the ground G in the penetration step. Fig. 6 is an explanatory diagram showing the state in which the foundation body 10 has penetrated into the ground G by the suction load.

[0026] First, as shown in Fig. 4, the foundation body 10 without the wind turbine 9 installed is towed to the installation site. Then, penetration of the foundation body 10 into the ground G begins. More specifically, the foundation body 10 sinks to the seabed due to its own weight or ballast load. As shown in Fig. 5, the lower end 19 of the side peripheral wall 12 penetrates to a certain extent into the ground G due to the own weight or ballast load of the foundation body 10.

[0027] Next, the drainage pump 33 is operated to forcibly drain the water in the internal space 15 of the foundation body 10 through the drain hole 41 and the drain pipe 31 to the outside of the foundation body 10. At this time, the valve 35 is closed and the valve 32 is open. A pressure difference occurs between the inside and outside of the foundation body 10 due to the forced drainage. A suction load due to the pressure difference acts on the foundation body 10, and the side peripheral wall 12 is further penetrated into the ground G. In this way, as shown in FIG. 6, the foundation body 10 penetrates into the ground G. After this, the filling space 16 is filled with the filling material 5 (see FIG. 1) by a filling pump (not shown). The filling material 5 is grout, mortar, or the like. After the installation of the suction foundation 100 is completed, the windmill 9 is installed on the foundation body 10. In detail, the windmill 9 is installed on the support 13.

[0028] Next, a method for removing the suction foundation 100 will be described. A service period is set for the suction foundation 100. After the service period has elapsed, the suction foundation 100 is removed. The suction foundation 100 is removed, for example, when the wind turbine 9 has been detached from the foundation main body 10.

[0029] In the suction foundation 100, by operating the water supply pump 36, water is supplied to the internal space 15 of the foundation body 10 via the water supply pipe 34 and the water supply hole 42. At this time, the valve 32 is closed and the valve 35 is open. The pressure of the water supply acts between the ceiling wall 11 and the filling material 5, and a force acts on the foundation body 10 in a direction to float up. This promotes the floating of the foundation body 10 from the ground G. The suction foundation 100 can be removed without vibration or noise.

[0030] In such a suction foundation 100, since the width W of the vertical beam 2 becomes smaller from the top to the bottom, the penetration resistance from the ground G can be reduced more than when the vertical cross-sectional shape of the vertical beam 2 is simply rectangular (for example, the vertical beam 2 is an H-shaped steel). In detail, the vertical beam 2 whose width W becomes smaller from the top to the bottom can reduce the contact area between the vertical beam 2 and the ground G at the time of penetration, compared to a vertical beam whose width W does not become smaller from the top to the bottom. As a result, the penetration resistance from the ground G can be reduced. In addition, since the width W of the vertical beam 2 becomes smaller from the top to the bottom, the amount of components can be reduced more than when the vertical cross-sectional shape of the vertical beam 2 is simply rectangular. In addition, since the vertical beam 2 is plate-shaped, the amount of welding between the foundation body 10 and the vertical beam 2 can be reduced more than when the vertical beam 2 is an H-shaped steel. If the vertical beam 2 is an H-shaped steel, welding between the flange and the web is required, so the amount of welding may increase.

[0031] Furthermore, even if the foundation body 10 is tilted with respect to the vertical direction during penetration of the suction foundation 100, the tilt can be self-repaired. In detail, when the foundation body 10 is tilted with respect to the vertical direction, the width W of the vertical beam 2 becomes smaller from the top to the bottom, so that the cross-sectional area of ​​the portion of the vertical beam 2 that penetrates deeply into the ground G is larger than the cross-sectional area of ​​the portion of the vertical beam 2 that penetrates shallowly into the ground G. The cross-sectional area is a cross section on a horizontal plane. Therefore, the penetration resistance of the portion of the vertical beam 2 that penetrates deeply into the ground G is larger than the penetration resistance of the portion of the vertical beam 2 that penetrates shallowly into the ground G. In other words, the portion of the vertical beam 2 that penetrates deeply into the ground G is less likely to penetrate into the ground G, and the portion of the vertical beam 2 that penetrates shallowly into the ground G is more likely to penetrate into the ground G. As a result, the tilt is self-repaired.

[0032] In addition, the first derivative of the rate of change of the width W in the direction from top to bottom is positive, i.e., the shape of the inner edge 23 of the vertical beam 2 is a downward convex curve, so that the effect of suppressing the deformation of the side wall 12 by the vertical beam 2 can be efficiently realized while reducing the penetration resistance. FIG. 7 is an explanatory diagram showing the pressure distribution acting on the side wall 12 of the suction foundation 100. As described above, in the penetration process of the suction foundation 100, a pressure difference occurs between the inside and outside of the foundation body 10 due to the forced drainage of the water in the internal space 15. As shown in FIG. 7, a substantially uniform pressure distribution occurs in the vertical direction in the part of the side wall 12 that is not penetrated into the ground G, and a pressure distribution that decreases from top to bottom can occur in the part of the side wall 12 that is penetrated into the ground G. In this way, a larger pressure can act on the side wall 12 at the upper part. FIG. 8 is an explanatory diagram showing a shear force diagram SFD (Shear Force Diagram) when a load P that decreases from top to bottom acts on the cantilever beam B. In the example of FIG. 8, the rate of decrease of the load P in the direction from top to bottom is constant. Here, the cantilever beam B is regarded as the side peripheral wall 12. When the load P that decreases from top to bottom acts on the cantilever beam B, a shear force distribution that decreases from top to bottom and forms a downward convex curve when the vertical direction is the horizontal axis acts on the cantilever beam B. In the example of FIG. 8, the downward convex curve is a quadratic curve. By making the shape of the inner end edge 23 of the vertical beam 2 a downward convex curve in correspondence with this shear force distribution, the effect of suppressing the deformation of the side peripheral wall 12 by the vertical beam 2 can be efficiently realized while reducing the penetration resistance. In particular, by making the shape of the inner end edge 23 of the vertical beam 2 a quadratic or higher curve, it can be more effectively corresponded to the above-mentioned shear force distribution, and therefore the effect of suppressing the deformation of the side peripheral wall 12 by the vertical beam 2 can be more efficiently realized.

[0033] In addition, in the suction foundation 100, nine vertical beams 2 are attached to the inner surface 17 of the side peripheral wall 12, so that deformation such as buckling of the side peripheral wall 12 can be effectively suppressed. Furthermore, the nine vertical beams 2 are arranged at equal intervals in the circumferential direction of the side peripheral wall 12. This prevents the interval between two adjacent vertical beams 2 in the circumferential direction of the side peripheral wall 12 from becoming excessively wide, and more effectively suppresses deformation such as buckling of the side peripheral wall 12. If the nine vertical beams 2 are arranged unevenly in the circumferential direction of the side peripheral wall 12, the interval between two adjacent vertical beams 2 in the circumferential direction may be larger than the interval between two adjacent vertical beams 2 in another circumferential direction.

[0034] FIG. 9 is a vertical cross-sectional view of a vertical beam 202 according to a modified example. FIG. 9 corresponds to FIG. 3. The vertical beam 202 differs from the vertical beam 2 in the shape of the inner edge 223. In this example, the first derivative of the rate of change of the width W is zero (i.e., the rate of change of the width W is constant). That is, the shape of the inner edge 223 is substantially linear (i.e., a linear curve). The vertical cross-sectional shape of the vertical beam 202 is substantially triangular. Since the shape of the inner edge 223 of the vertical beam 202 is substantially linear, the cross-sectional area can be made larger than when the shape of the inner edge 223 is a downwardly convex curve as shown in FIG. 3. As a result, deformation such as buckling of the side peripheral wall 12 can be more effectively suppressed.

[0035] Other Embodiments As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. are appropriately performed. In addition, it is also possible to combine the components described in the above embodiment to form a new embodiment. In addition, among the components described in the attached drawings and detailed description, not only components essential for solving the problem but also components that are not essential for solving the problem in order to exemplify the technology may be included. Therefore, the fact that these non-essential components are described in the attached drawings and detailed description should not immediately be taken to mean that these non-essential components are essential.

[0036] For example, the shape of the foundation body 10 is not limited to a substantially cylindrical shape. The foundation body 10 can be formed into any shape as long as it has a ceiling wall and side walls and is open at the bottom. For example, the foundation body 10 may be formed into a rectangular tube shape, such as a substantially rectangular or pentagonal cross section. The foundation body 10 may also be formed into a dome shape with a curved ceiling wall.

[0037] The material of the foundation body 10 is not limited to a steel plate, and may be any material, for example, concrete. When the material of the foundation body 10 is concrete, the vertical beam 2 covered with concrete may be attached to the foundation body 10.

[0038] The foundation body 10 does not need to define the filled space 16 when the side peripheral wall 12 is inserted into the ground G. That is, the side peripheral wall 12 and the vertical beam 2 may be inserted into the ground G in their entirety.

[0039] Furthermore, the structure installed on the suction foundation 100 is not limited to the wind turbine 9. The structure may be a wind observation tower, a caisson, etc. The foundation body 10 does not necessarily need to be provided with the support pillars 13.

[0040] As long as the vertical beam 2 extends from the inner surface 17 of the side peripheral wall 12 toward the inside of the side peripheral wall 12, it does not have to extend toward the axis C of the side peripheral wall 12. As long as the vertical beam 2 extends from the top to the bottom, the longitudinal direction of the vertical beam 2 does not have to be parallel to the axis C. As long as the width W of the vertical beam 2 decreases from the top to the bottom, the shape of the inner edge 23 of the vertical beam 2 is not limited. For example, the shape of the inner edge 23 may be stepped. Furthermore, the width W of the vertical beam 2 may be constant for a predetermined distance downward from the upper end 22 of the vertical beam 2. That is, the vertical beam 2 may include a portion whose width W is constant in the vertical direction. Specifically, the width W of the portion of the vertical beam 2 that exists in the filling space 16 (i.e., the portion that does not penetrate into the ground G) may be constant in the vertical direction. This makes it possible to more effectively suppress deformation such as buckling of the side peripheral wall 12 without reducing the penetration ability of the suction foundation 100 into the ground G.

[0041] There is no limitation on the number of vertical beams 2. When multiple vertical beams 2 are attached to the inner surface 17 of the side peripheral wall 12, the multiple vertical beams 2 do not have to be arranged at equal intervals in the circumferential direction of the side peripheral wall 12.

[0042] The technology of the present disclosure can be summarized as follows.

[0043] [1] The suction foundation 100 comprises a foundation body 10 having a ceiling wall 11 and a side wall 12 extending downward from the ceiling wall 11 and penetrating into the underwater ground G, and plate-shaped vertical beams 2, 202 extending from the inner surface 17 of the side wall 12 to the inside of the side wall 12 and from above to below, and a width W of the vertical beams 2, 202, which is the dimension in the direction extending from the inner surface 17 of the side wall 12 to the inside of the side wall 12, becomes smaller from above to below.

[0044] According to this configuration, the width W of the vertical beam 2,202 becomes smaller from top to bottom, so that the penetration resistance from the ground G can be reduced more than when, for example, the width W is constant (i.e., the vertical cross-sectional shape of the vertical beam 2,202 is rectangular).

[0045] [2] In the suction foundation 100 described in [1], the first derivative of the rate of change of the width W in the upward-to-downward direction is positive.

[0046] According to this configuration, the shape of the vertical beams 2, 202 can be made to correspond to the shear force distribution that may occur in the side peripheral wall 12. This makes it possible to efficiently suppress the deformation of the side peripheral wall 12 by the vertical beams 2 while reducing the penetration resistance.

[0047] [3] In the suction foundation 100 described in [1] or [2], the shape of the inner edge 23, 223 of the vertical beam 2, 202 is a curve of degree 2 or higher.

[0048] According to this configuration, the shape of the vertical beams 2, 202 can be made to correspond to the shear force distribution that may occur in the side wall 12, so that the effect of suppressing deformation of the side wall 12 by the vertical beams 2 can be achieved more efficiently.

[0049] [4] In the suction foundation 100 described in any one of [1] to [3], three or more vertical beams 2, 202 are attached to the inner surface 17 of the side wall 12.

[0050] According to this configuration, deformation such as buckling of the side peripheral wall 12 can be effectively suppressed.

[0051] [5] In the suction foundation 100 described in any one of [1] to [4], the three or more vertical beams 2, 202 are arranged at equal intervals in the circumferential direction of the side peripheral wall 12.

[0052] According to this configuration, the distance between two circumferentially adjacent vertical beams 2, 202 of the side peripheral wall 12 is prevented from becoming excessively wide, and deformation of the side peripheral wall 12, such as buckling, can be suppressed more effectively. [Explanation of symbols]

[0053] 100 Suction Basics 10. Basic Body 11 Ceiling Wall 12 Side wall 17 Inner surface of side wall 2,202 stringers 23,223 Inner edge G. Ground W width

Claims

1. A foundation body having a ceiling wall and a side wall extending downward from the ceiling wall and penetrating into the underwater ground; A plate-shaped longitudinal beam extending from the inner surface of the side peripheral wall toward the inside of the side peripheral wall and from above to below, A suction foundation in which the width of the vertical beam, which is the dimension extending from the inner surface of the side wall to the inside of the side wall, becomes smaller from top to bottom.

2. In the suction foundation according to claim 1, A suction basis in which the first derivative of the rate of change of the width in the top-to-bottom direction is positive.

3. In the suction foundation according to claim 1 or 2, A suction foundation in which the shape of the inner edge of the vertical beam is a quadratic or higher curve.

4. In the suction foundation according to claim 1 or 2, A suction foundation in which three or more of the vertical beams are attached to the inner surface of the side peripheral wall.

5. In the suction foundation according to claim 4, A suction foundation in which the three or more vertical beams are equally spaced circumferentially around the side peripheral wall.

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