EP4320313A1

EP4320313A1 - Foundation structure for an offshore construction

Info

Publication number: EP4320313A1
Application number: EP22723569.4A
Authority: EP
Inventors: Volker Herwig
Original assignee: Rwe Offshore Wind GmbH
Current assignee: Rwe Offshore Wind GmbH
Priority date: 2021-04-22
Filing date: 2022-04-14
Publication date: 2024-02-14
Also published as: DE102021110351A1; WO2022223471A1

Abstract

The invention relates to a foundation pile (2) having a first end (3) and a second end (4), the foundation pile (2) having fastening means (11) at the first end (3) for fastening a superstructure (5), the foundation pile (2) being hollow and having a transverse sectional area (A) which continuously decreases in a tapering section (6) towards the second end (4).

Description

Foundation structure for an offshore structure

The invention relates to a foundation pile, in particular for an offshore structure. Furthermore, the invention relates to a corresponding offshore structure, in particular an offshore wind energy installation.

In particular, offshore structures are structures that are statically anchored in the seabed and extend over areas below and above the water surface. Foundation structures for such buildings are known in various designs and are used, for example, as supporting structures for wind turbines or platforms. If the foundation structure is designed to be statically anchored to the seabed, it can be in the form of at least one pile. Such a pole is usually hollow. Various technical components and lines can be accommodated inside the pole.

In the case of known foundation piles, the material requirement is considerable. It is therefore an object of the invention to save material compared to known foundation piles.

According to the invention, a foundation pile is presented with a first end and a second end, the foundation pile having fastening means at the first end for fastening a structure, the foundation pile being hollow and having a cross-sectional area which, in a tapering section, continuously decreases in the direction of the second end reduced.

A foundation pile is a component with which a building can be founded, i.e. anchored in the ground. The green manure pile described is preferably designed as a foundation pile for a structure, in particular special for an offshore structure. The building can have one or more foundation piles designed as described. If there is exactly one foundation pile, the foundation pile can also be referred to as a monopile. The foundation pile described can be used as a monopile, but is not limited to this option. A use of the described foundation pile with other foundation structures, for example with tripiles, is possible.

The foundation pile preferably has a round cross section, in particular a circular cross section. In the case of a circular cross-section, the foundation pile is preferably cylindrical. The foundation pile is hollow. The foundation pile preferably includes a mantle. The foundation pile is preferably made of steel. However, it is also conceivable to use a different material.

The foundation stake has a first end and a second end. The ends can also be referred to as end faces. The two ends of the foundation pile are spaced apart from each other in the axial direction. The foundation pile extends in the axial direction between the two ends.

At its first end, the foundation pile has fastening means for fastening a structure. The structure can be, for example, a tower for a wind turbine, an oil rig, a substation structure or a platform. The attachment means may include, for example, a flange, screw holes and/or a bracket. Other options for connection are plug-in connections, to which a sealing material can be added. The fact that the fastening means are arranged at the first end of the foundation pile is to be understood functionally in such a way that, via the fastening means, the structure can be mounted on the foundation pile in the axial direction at the first end of the foundation pile.

The fastening means can generally be used to distinguish between the first end and the second end. At the second end, the greening stake preferably has no fastening means as at the first end. In general, it is preferred that the first end and the second end of the foundation pile are designed differently. The distinction between the first end and the second end of the foundation pile allows an axial direction to be defined. If the foundation pile is anchored in a ground as intended, the second end of the foundation pile is in the ground, while the first end protrudes from the ground. In this respect, the first end can also be used as the upper end of the Foundation pile are referred to, while the second end can also be referred to as the lower end de or pile foot. The fasteners on the foundation pile can therefore be used to identify where the top is, even before it is installed.

If the foundation pile is part of an offshore structure, the second end of the foundation pile is anchored in a seabed. Such a foundation pile preferably extends over a section above the water surface, a section between the water surface and the seabed and a section within the seabed.

The foundation pile serves in particular to absorb the load of the structure and to introduce it into the ground. In the case of an offshore structure, the foundation pile is exposed to considerable transverse forces and moments due to wind, wave and current-induced loads. The foundation pile described is able to withstand such loads. Comparatively little material is required for the foundation pile. This is possible because the foundation pile has a cross-sectional area that continuously decreases in a tapering section towards the second end. The tapering section is preferably located within the ground when the foundation pile is installed. This design is particularly efficient in that comparatively little material is required for a certain stability of the foundation pile. This is based on the finding that from a strength point of view it is not necessary to maintain a large cross-sectional area in the direction of the second end of the foundation pile, since the shear forces and moments acting on the foundation pile decrease in the direction of the second end. The tapered portion is oriented toward the second end. This means that the foundation pile tapers in the taper section when viewed in the axial direction starting from the first end. This taper of the pile proves to be advantageous because material is saved. In this respect, tapering the pile is advantageous from an economic and technical perspective.

The fact that the cross-sectional area in the tapered section decreases continuously means that the cross-sectional area of the tapered section is at every point of the taper portion is greater than at a location subsequent toward the second end. That is, when viewed in the axial direction from the first end to the second end, the cross-sectional area always decreases within the neck portion. The taper section has a finite extent. It is therefore not sufficient that the cross-sectional area suddenly decreases at a step. In that case, a taper section with zero extent could be defined at best. However, such a section should not be understood here as a tapering section. The narrowing section particularly preferably has an axial extent in the range from 0.5 to 5 m, in particular in the range from 1 to 3 m. Overall, the foundation pile preferably has an axial extent of at least 10 m, in particular at least 20 m, particularly preferably at least 40 m. Overall, the foundation pile preferably has an axial extent of at most 100 m, in particular at most 80 m, particularly preferably at most 50 m.

The fact that the taper is towards the second end means that the cross-sectional area decreases in the taper section when viewed from the first end to the second end. It is not necessary for the cross-sectional area to decrease beginning at the first end and/or up to the second end. This would be the case if the taper section extends to the first end and/or to the second end, which is possible but not required.

The taper section is preferably spaced from the first end and the second end of the foundation pile. At locations outside of the taper section, the cross-section of the foundation pile can be of any type. However, it is preferred that the cross-sectional area is constant outside the tapering section. However, it is also preferred that the foundation pile has a widening section between the first end and the narrowing section, in which the cross-sectional area of the foundation pile increases continuously in the direction of the second end. Starting from the first end, the cross-sectional area can, for example, constantly have a first value, increase continuously to a second value in the widening section, remain constant at the second value, decrease continuously to a third value in the narrowing section and remain constant at the third value until the second end. The first value and the third value are preferably identical. In the case of an offshore construction, the widening section is preferably arranged below the attacking waves in order to increase the rigidity of the foundation pile in the area of the seabed. The expansion section preferably has an axial extension in the range from 0.5 to 5 m, in particular in the range from 1 to 3 m.

The narrowing section is preferably arranged in a half of the foundation pile which adjoins the second end of the foundation pile. This means that the taper portion is located entirely between the second end and the center of the foundation pile, it being possible but not necessary for the taper portion to extend to the second end and/or to the center of the foundation pile. The narrowing section is particularly preferably arranged in a third of the foundation pile adjoining the second end of the foundation pile.

In the assembled state, the tapering section is preferably located within the floor. The rejuvenation only takes place below the surface of the ground, where particularly large forces and moments can act on the foundation pile. Due to the tapering, the stability is affected particularly little in this case.

If present, the widening section is preferably arranged in a half of the foundation pile adjoining the first end of the foundation pile. This means that the flared portion is located entirely between the first end and the center of the foundation pile, it being possible, but not required, for the flared portion to extend to the first end and/or to the center of the foundation pile.

In the assembled state, the widening section is preferably located outside the floor. The widening takes place above the surface of the ground, where particularly large forces and moments can act on the foundation pile. The expansion particularly strengthens the stability in this case. The narrowing section and the optional widening section are defined solely by the progression of the cross-sectional area. It is conceivable that in the case of a foundation pile, different sections can be identified as a narrowing section or different sections as a widening section. It is not necessary, but preferred, for the narrowing section and/or the widening section to be formed by a respective separate component. This simplifies the manufacture of the foundation pile. The individual components are vorzugswei se connected to each other, in particular welded, before the green manure pile formed in this way is transported to its destination.

If the taper section is spaced from the first end of the foundation pile, the cross-sectional area of the foundation pile is preferably at least as large at any point between the first end and the taper section as at the end of the taper section which faces the first end of the foundation pile. If the taper section is spaced from the second end of the foundation pile, the cross-sectional area of the foundation pile is preferably at least as large at any point between the second end and the taper section as at the end of the taper section which faces the second end of the foundation pile. If the taper portion is spaced apart from the first end and the second end of the foundation pile, the cross-sectional area of the foundation pile between the first end and the taper portion is preferably greater than that between the second end and the taper portion.

In the case of a circular cross-section, the foundation pile has a diameter that continuously decreases in the tapering section towards the second end. The diameter is preferably in the range of 3 to 15 m at each point of the foundation pile. If the foundation pile is used as a monopile, the foundation pile preferably has a diameter of at least 3 m, in particular at least 5 m and/or at most 15 m. in particular of a maximum of 10 m. If the foundation pile is used as part of a tripod, the Foundation pile preferably has a diameter of at least 1 m, in particular at least 3 m and/or at most 10 m, in particular at most 8 m.

During the installation of the foundation pile, soil loosening within the foundation pile and compaction of the soil outside of the foundation pile can occur at the level of the taper section. It is possible to compensate for this by filling in the foundation pile in order to achieve a high load-bearing capacity.

In a preferred embodiment, the necked portion of the foundation pile is spaced from the second end of the foundation pile, the cross-sectional area of the foundation pile being constant between the necked portion and the second end.

Between the narrowing section and the second end of the foundation pile is preferably cylindrical. This makes production easier. Because the tapered section does not extend to the second end, a particularly large amount of material can be saved, particularly if the cross-sectional area of the foundation pile does not increase again between the tapered section and the second end.

In a further preferred embodiment, the foundation pile is conical in the taper section.

In this embodiment, the foundation pile has straight edges in the taper portion when viewed in a longitudinal section. This configuration is particularly easy to manufacture. It is particularly preferred that the tapering section is formed by a cone as a separate component. If the foundation pile also has a widening section, this is also preferably formed by a cone as a separate component. The foundation pile can be formed by connecting two cones to one another via a cylindrical component and attaching a respective additional cylindrical component to the outside of the two cones. The cones can be identical in design, but oriented in opposite directions. In a further preferred embodiment, a ratio between the square root of the cross-sectional area of the foundation pile and a wall thickness of the foundation pile at any point of the foundation pile is at most 170, in particular at most 135. The wall thickness of the hollow foundation pile can vary depending on the local

Vary cross-sectional area, but is preferably always designed so that buckling of the foundation pile is prevented. In principle, a smaller wall thickness is sufficient for a small cross-sectional area. In the present embodiment, the square root of the cross-sectional area is at most 170 times the wall thickness, in particular at most 135 times. In this respect, the cross-sectional area is limited relative to the wall thickness, which makes sense for static reasons.

In the case of a circular cross-section, the square root of the cross-sectional area corresponds to the diameter of the foundation pile, up to a constant factor of around 0.9. In the case of a circular cross section, it is preferred that the ratio between the diameter of the foundation pile and the wall thickness of the foundation pile is at most 150, in particular at most 120. However, since a circular cross-section is not mandatory, the more general definition using the square root of the cross-sectional area is also considered.

In a further preferred embodiment, the tapering portion is spaced from the first end and from the second end, wherein the

Foundation pile has a wall thickness which is greater in at least one section between the first end and the narrowing section than in at least one section between the second end and the narrowing section.

With this design, material can be saved by reducing the wall thickness where this is possible due to the narrowing. Particularly in this embodiment, it is preferred that the cross-sectional area of the foundation pile is larger in at least one section between the first end and the narrowing section than in at least one section between the second end and the narrowing section. It is particularly preferred that the wall thickness is greater at any point between the first end and the tapered section than at any point between the second end and the tapered section.

In a further preferred embodiment, the foundation pile has a widening section between the first end and the narrowing section, in which the cross-sectional area of the foundation pile increases continuously in the direction of the second end, the narrowing section and the widening section being arranged at a distance from one another, and wherein the foundation pile has a wall thickness. The wall thickness of the foundation pile is greater between the widening section and the narrowing section than at the second end.

In the present embodiment, when the flare portion is spaced apart from the first end, the wall thickness between the first end and the flare portion can be prevented from being oversized. Due to the narrowing of the cross section of the foundation pile in the narrowing section, the cross-sectional area at the second end can be smaller than between the narrowing section and the widening section. In this way, material can be saved. Preferably, the wall thickness between the tapering section and the widening section is between 5 and 15 cm and at the second end between 3 and 12 cm. The wall thickness between the narrowing section and the widening section is preferably 1 to 5 cm greater than at the second end.

Furthermore, it is preferred that the wall thickness between the widening section and the narrowing section is greater than at the first end. In this way, further material can be saved. The wall thickness at the first end is preferably between 3 and 12 cm. The wall thickness between the narrowing section and the widening section is preferably 1 to 5 cm greater than at the first end.

Within an area with a constant cross-sectional area, a constant wall thickness is recommended, as this is easier to implement from a manufacturing point of view and therefore advantageous. This applies in particular between the tapered section and the second end if the tapered section is arranged at a distance from the second end.

In a further preferred embodiment, the foundation pile has a coating which adjoins the first end but not the second end.

In order to protect the foundation pile from corrosive influences and thus increase its service life, the foundation pile is partially coated. The coating is preferably only provided at points where an environment prevails that requires anti-corrosion measures and the coating is therefore technically sensible. Such an environment is not to be expected below the sea floor due to a lack of sufficient oxygen supply. Corrosion can also occur there due to certain bacteria, but the coating used here is not suitable for preventing this corrosion. The application of a coating up to the second end of the foundation pile is therefore not technically sensible and is therefore not provided according to the present embodiment. This has the advantage that the uncoated area can also serve as an indicator for identifying the first and second end of the foundation pile. In the assembled state, the tapered section is preferably located within the floor. Therefore, it is preferable that the coating does not extend into the neck portion. The coating is preferably formed over the entire surface. In particular, the coating preferably extends over the full circumference of the foundation pile and/or, starting axially from the first end, over at least one third, in particular over at least half of the foundation pile.

As an alternative wording, the foundation pile of the present embodiment can be described as being coated in a first portion adjacent the first end and uncoated in a second portion adjacent the second end.

In a further preferred embodiment, the foundation pile is anchored in a seabed. In this embodiment, the foundation pile is viewed in its assembled state. The taper section is preferably located within the seabed. If present, the expansion section is preferably arranged outside the seabed. With the usual water level, the expansion section is preferably arranged between the water surface and the seabed.

The foundation pile is preferably anchored in the seabed in such a way that the narrowing section is arranged in an upper half of the part of the foundation pile which is located in the seabed. This means that the taper section is entirely between the seabed and the center of the seabed part of the foundation pile, it being possible, but not required, for the taper section to extend to the seabed and/or to the center of the seabed part of the foundation stake is enough. Preferably, the foundation pile is anchored to the seabed such that the neck portion is spaced from the seabed. The foundation pile is particularly preferably anchored in the seabed in such a way that the narrowing section is arranged in an upper third of that part of the foundation pile which is located in the seabed.

As a further aspect of the invention, an offshore structure is presented, which comprises a foundation pile and a structure, the structure being mounted on the foundation pile at a first end of the foundation pile, the foundation pile being anchored to a seabed at a second end, and wherein the foundation pile is hollow and has a cross-sectional area that continuously decreases in a taper portion toward the second end.

The advantages and features of the foundation pile described are applicable and transferable to the offshore structure and vice versa. The offshore structure has one or more foundation piles, which are preferably designed like the foundation pile described above.

In a preferred embodiment, the offshore structure is an offshore wind turbine. In a further preferred embodiment, the offshore structure is an offshore substation.

Particularly preferred embodiments are described below, to which, however, the invention is not limited. In particular, the invention is not limited to monopiles that serve as the foundation structure of an offshore wind turbine. The combination of several foundation piles according to the invention as a multi-pile foundation structure (eg as a tripile) is also possible. In addition, a pile designed according to the invention can also serve as a foundation structure for other structures offshore and onshore. They show: FIG. 1: a schematic side view of an embodiment of an offshore structure according to the invention,

Fig. 2: a schematic side view of a further embodiment of an offshore structure according to the invention,

3a: a schematic cross-sectional representation of the foundation pile from FIG. 1 above the narrowing section,

FIG. 3b: a schematic cross-sectional representation of the foundation pile from FIG. 1 below the narrowing section.

1 shows a schematic view of an offshore structure 1. The illustrated embodiment is an offshore wind turbine 12 with a foundation pile 2 designed as a monopile. The offshore wind turbine 12 has a structure 5, which has a tower 13 and a gondola 14 and a rotor 15 attached to the outside of this. The rotor 15 is set in motion by the wind. The mechanical energy absorbed in this way is transmitted to a generator (not shown) inside the gondola 14 via a shaft-hub connection. This converts the mechanical energy into electrical energy. The electrical cal energy is discharged via cables through the tower 13 of the wind turbine 12 down. When using several wind turbines 12 in an environment, as is usual with offshore wind farms, the electrical lines are together and collected in an offshore converter station, for example, before the energy is fed into the local power grid.

The foundation pile 2 shown in FIG. 1 comprises a first end 3 and a second end 4. The first end 3 is characterized in that fastening means 11 for fastening the structure 5 are provided on this end. The foundation pile 2 has at each point a circular cross-sectional area A, which is shown in Fig. 3a and 3b. The foundation pile 2 comprises cylindrical and conical sections. In order to increase the rigidity of the offshore structure 1 in the area of the attacking waves, the foundation pile 2 below the water surface 8 has a larger cross-sectional area A than in the adjacent area above. This is achieved by a conical widening section 16 .

Below the expansion section 16 there is a wide rer cylindrical tower section. This protrudes beyond the seabed 9 into the seabed 10 .

Below this cylindrical section, in the direction of the second end 4 of the foundation pile 2, there is a tapering section 6, in which the cross-sectional area A of the foundation pile 2 decreases continuously in the direction of the second end 4. In the embodiment shown in FIG. 1 , a cylindrical area follows underneath, which extends to the second end 4 of the foundation pile 2 and encloses the second end 4 .

The foundation pile 2 is partially hen with a full-surface coating 7 verse. This extends from the first end 3 of the foundation pile 2 to the area within half of the seabed 10, but not to the second end 4. The coating 7 protects the foundation pile 2 from corrosion.

Fig. 2 shows a schematic view of a further embodiment of an offshore structure 1 with a foundation pile 2. From the rotor 15 of the wind turbine 12 to the beginning of the tapering section 6, this embodiment is identical to the embodiment from Fig. 1. The embodiment according to Fig. 2 under differs from the embodiment of FIG. 1 in terms of the design of the Tapering section 6. This is formed in FIG. 2 as a cone, which is significantly longer than in FIG. The cone that forms the tapering section 6 extends over 60 to 80% of the area of the foundation pile 2 that protrudes into the seabed 10 . Fig. 3a shows a cross-sectional view of the foundation pile 2 from Fig. 1 above the narrowing section 6 and below the widening section 16.

FIG. 3b shows a cross-sectional representation of the foundation pile 2 from FIG. 1 below the narrowing section 6. A cross-sectional area A and a wall thickness d are shown. The cross-sectional area A refers to the entire cross-section of the foundation pile 2, including the wall.

The wall thickness d, depending on the local cross-sectional area A, has a minimum dimension for each point of the foundation pile 2 . The ratio between the square root of the cross-sectional area A and the wall thickness d does not exceed a value of 170, in particular 120. In the present embodiment of a cylindrical or conical foundation pile, there are only circular cross-sectional areas A, so that the ratio between a diameter D and the wall thickness d can also be specified. This is a maximum of 150, in particular a maximum of 120.

reference list

1 offshore structure

2 foundation stake 3 first end

4 second end

5 construction

6 taper section

7 coating 8 water surface

9 seabed

10 seabed

11 fasteners

12 wind turbine 13 tower

14 gondola

15 rotors

16 expansion section A cross-sectional area d wall thickness

Claims

Expectations

1. foundation pile (2) with a first end (3) and a second end (4), wherein the foundation pile (2) at the first end (3) fastening means (11) for fastening a structure (5), wherein the foundation pile (2) is hollow and a

Has cross-sectional area (A) that continuously decreases in a tapering section (6) towards the second end (4).

2. A foundation pile (2) according to claim 1, wherein the taper portion (6) is spaced from the second end (4) and wherein the cross-sectional area (A) of the foundation pile (2) is between the taper portion (6) and the second end (4) is constant.

3. foundation pile (2) according to any one of the preceding claims, wherein the green manure pile (2) in the tapering portion (6) is conical.

4. Foundation pile (2) according to one of the preceding claims, wherein at each point of the foundation pile (2) a ratio between the root of the cross-sectional area (A) of the foundation pile (2) and a wall thickness (d) of the foundation pile (2) at most is 170.

5. Foundation pile (2) according to one of the preceding claims, wherein the narrowing section (6) is arranged at a distance from the first end (3) and from the second end (4), and the foundation pile (2) has a wall thickness ( d) which is larger in at least one section between the first end (3) and the tapered section (6) than in at least one section between the second end (4) and the tapered section (6).

6. Foundation pile (2) according to one of the preceding claims, wherein the foundation pile (2) has a widening section (16) between the first end (3) and the narrowing section (6), in which the cross-sectional area (A) of the Foundation pile (2) continuously enlarged in the direction of the second end (4), the narrowing section (6) and the widening section Section (16) are spaced apart, and wherein the foundation pile (2) has a wall thickness (d) between the widening section (16) and the narrowing section (6) is greater than at the second end (4).

7. Foundation pile (2) according to one of the preceding claims, wherein the foundation pile (2) has a coating (7) which is adjacent to the first end (3) but not to the second end (4).

8. Foundation pile (2) according to one of the preceding claims, wherein the foundation pile (2) is anchored to the second end (4) in a seabed (10).

9. Offshore structure (1) comprising a foundation pile (2) and a structure (5), wherein the structure (5) at a first end (3) of the foundation pile (2) is mounted on the foundation pile (2), wherein the Foundation pile (2) is anchored with a second end (4) in a sea bed (10), and wherein the foundation pile (2) is hollow and has a cross-sectional area (A) which in a tapering section (6) continuously in Reduced towards the second end (4).

10. Offshore structure (1) according to claim 9, wherein the offshore structure (1) is a wind turbine (12).

2

Figure 3a