EP4237626A2

EP4237626A2 - Wind turbine foundation structure

Info

Publication number: EP4237626A2
Application number: EP21790834.2A
Authority: EP
Inventors: Daniel Bartminn; Artur CZARNECKI
Original assignee: Rwe Offshore Wind GmbH
Current assignee: Rwe Offshore Wind GmbH
Priority date: 2020-10-28
Filing date: 2021-10-08
Publication date: 2023-09-06
Also published as: WO2022089915A2; WO2022089915A3; KR20230095950A; JP2023549700A; TW202221198A; DE102020128325A1; US20230258158A1

Abstract

The invention relates to a wind turbine foundation structure comprising: a hollow structural element having a peripheral wall that extends in the longitudinal direction, wherein a first cable feedthrough is arranged in and penetrates the wall; a transition piece having an overlap region that projects into the hollow structural element; a transition region that projects out of the hollow structural element on the front side; and a peripheral wall that extends in the longitudinal direction, wherein a second cable feedthrough penetrating the wall is arranged in the overlap region of the wall, characterised in that the first and the second cable feedthroughs, when the hollow structural element and the transition piece are in the installed state, abut one another at least partially in an overlapping manner.

Description

Wind Turbine Foundation Structure

The subject relates to a wind turbine foundation structure. Wind power plants within the meaning of the subject can be wind turbines, transformer stations, substations, substations or the like.

Wind turbines are usually founded on hollow structural elements. The hollow structural elements are founded in the ground with an anchoring depth of between 5 m and 50 m. The hollow structural elements preferably have a length of more than 45m, in particular between 50m and 100m. In offshore installations, the hollow structure elements are founded in such a way that they have an anchoring depth of between 5m and 50m and protrude from the water surface by between 10m and 30m. The hollow structural elements are usually used at water depths between 10m and 50m. However, water depths of up to 150m can also be implemented.

The hollow structural elements have diameters between 4m and 18m, but preferably up to 12m. Traditionally, hollow structural members are formed as steel cylinders that are driven into the seabed by ramming or vibrating. The use of steel as the material for the hollow structural elements results in high costs due to their production and their high dead weight. In addition, the connection with so-called "transition pieces" on the top using grout connections or screw connections is necessary.

Transition pieces with grout connections or slip-joint connections are used in the hollow structural elements used for the foundation. The electricity produced with the help of the wind turbine is fed via an electrical cable to a substation and from there into the electrical energy supply network. The cables are either passed through the outside of the tower Ground out or inside the tower, therefore inside the transition pieces and / or the hollow structure element.

However, it may be desirable to reduce the length and thus the weight of the hollow structural elements, in particular those made of concrete, so that they no longer protrude from the water surface with the same anchoring depth. But then it happens that the transition piece (transition piece) is connected to the hollow structural element below the water surface and there is an overlapping area below the water surface.

Due to technical installation specifications, it may be necessary for the cable routed inside the hollow structural element to be routed to the outside where the hollow structural element and the transition piece intersect in the longitudinal direction. In this area, the transition piece and the hollow structural element (both of which are sometimes referred to synonymously below as a pile) are connected to one another using the so-called slip-joint method or the grout method. The two piles intersect and there is an area of overlap. It may be necessary, for example, to lead the cable out of the pole in the area of such an overlap if the cable is to be led out of the pole near the ground, in particular near the bottom of the lake. It can happen that the part of the transition piece protruding from the hollow structural element is too far from the ground and the cable, if it were routed out of the transition piece, hangs too far freely before it reaches the ground. On the other hand, the length of the overlap between the transition piece and the hollow structural element can be such that the area of the hollow structural element below the overlapping area is too close to the floor or is already integrated within the floor and the cable can therefore also not be routed out there. It may therefore be necessary to lead the cable out of the post in the overlapping area. The object of the object was therefore to provide a foundation structure in which a cable can be led out of the foundation structure near the ground. This object is achieved by a foundation structure according to claim 1.

The foundation structure in question has a hollow structural element which extends in the longitudinal direction and is formed in the longitudinal direction by a peripheral wall. The wall has two distal ends, each bounded by end faces. A first face may be a top face and a second face may be a bottom face. The top and bottom can be defined by the position of the hollow structural element in the final installed state. In the installed state, the lower end face is founded in the ground, and the upper end face protrudes from the ground.

The wall can be formed from a mineral building material.

The associated transition piece is attached to the hollow structural element, in particular being plugged on, plugged in or plugged over. The transition piece may include at least one ship landing facility with a ladder.

The transition piece can have an outside diameter that is congruent with the inside diameter of the wall of the hollow structure element. Such a pole or cylinder element can be inserted into the hollow structural element. An annular gap between the inner lateral surface of the hollow structure element and the outer lateral surface of the transition piece can be ensured by webs, spacers or the like. Concrete or mortar can be filled into this annular gap so that a permanent connection is formed between the hollow structural element and the transition piece. The transition piece is connected to the hollow structural element using a grout connection or the slip-joint method. In this case, the transition piece is inserted into the hollow structure element with an overlap area and a transition area protrudes from the hollow structure element at the end. The transition piece is preferably monolithic, tubular and extends in a longitudinal direction. In the installed state, this longitudinal direction is preferably collinear with the longitudinal direction of the hollow structural element.

The transition piece has a peripheral wall, with a cable bushing breaking through the wall being arranged in the overlapping area. The cable suspended inside the foundation structure can be routed through the wall of the transition piece through this cable bushing.

At the same time, in order to route the cable to the outside in the overlapping area, it is also necessary to route it out of the hollow structural element. For this reason, the wall of the hollow structural element also has a cable bushing.

The cable bushings (cable feed holes) are openings breaking through the respective wall. A cable bushing can be understood to mean one or a plurality of holes which are approximately adapted to the outer diameter of the cable to be passed through. In order to enable a cable bushing through both the hollow structural element and the transition piece, it is proposed that the first and second cable bushings rest against one another in an at least partially overlapping manner when the hollow structural element and transition piece are in the assembled state. This makes it possible to feed the cable directly through the two walls without having to thread it in the annular space between the hollow structural element and the transition piece.

The transition piece is inserted into the hollow structural element that a

Angular position around the longitudinal axis of these two elements of the respective

Cable bushings is essentially the same, so that when plugged in the Cable bushings overlap each other, that is, in a projection parallel to the radius of the piles, they are at least partially on top of each other.

According to one exemplary embodiment, it is proposed that a cable is routed from the interior of the transition piece through the first and second cable bushings. When the wind turbine is assembled, not only is the foundation structure assembled, but also the tower including the turbine and wind wheel. From the generator, which is located in the nacelle, the cable runs through the tower, the transition piece and the hollow structural element to the cable bushings, where it is routed out of them .

The cable is exposed to increased stress from currents, especially in offshore installations, so that the free cable length outside the foundation structure until the cable lies on the ground should be limited. On the other hand, the cable must not be led out of the structure too close to the seabed, otherwise the minimum bending radii for transferring the cable from the horizontal to the predominantly vertical cannot be observed.

In particular, it is proposed that the cable bushing of the hollow structural element in the installed state is between 1.0 m and 5 m, preferably between 1.5 m and 3.5 m, above the seabed. This also applies in particular after the scour protection has been introduced around the foundation structure. The seabed is defined here as the vertical plane, which is specified in the planning documents as the water depth below the reference plane LAT (lowest astronomical tide - lowest water level).

According to one exemplary embodiment, it is proposed that a seal lying against the lateral surfaces be arranged circumferentially in an annular space between the inner lateral surface of the hollow structural element and the outer lateral surface of the transition piece. Particularly in the case of a grout connection, the seal should ensure that grout material does not pass through the cable glands to the outside as well as to the inside. This ensures the seal. The seal is preferably arranged circumferentially, in particular completely circumferentially, in the annular space. The seal preferably runs in a plane perpendicular to the longitudinal extent of the hollow structural element.

In the case of a grout connection, grout material is introduced into the annular space after the transition piece has been inserted into the hollow structural element. In order to prevent the grout material penetrating from above from reaching the cable bushings, it is proposed that the seal be arranged in the longitudinal direction of the hollow structural element above the cable bushing. In order to possibly prevent liquid from penetrating from the outside into the annular space via the cable bushings, a seal can be arranged below the cable bushing in the direction of the hollow structural element.

Sealing of the cable bushings can be achieved not only by a seal surrounding the annular space, but also by a seal arranged around the cable bushings according to one exemplary embodiment. In this case, a seal running around the cable bushing in a closed ring is provided in the annular space between the inner shell surface of the hollow structural element and the outer shell surface of the transition piece at a radial distance from the cable bushings. The seal is arranged around the cable bushings in such a way that it is at a radial distance from both circumferential outer edges of both cable bushings. In particular, in a projection parallel to the radius of the hollow structural element, the seal is annular, in particular circular or elliptical, placed around the cable bushings. Such a seal also prevents grout material, which is introduced into the annular space, from reaching the cable bushings and from being able to exit outwards or inwards there. The annulus is often relatively narrow, especially when a slip-joint connection is made rather than a grout connection. However, even with a grout connection, the annular gap is relatively small and only a small tolerance is allowed when inserting the transition piece into the hollow structural element. In order to prevent the seal from interfering with the insertion of the transition piece into the hollow structural element or from being damaged during insertion, it is also proposed that the seal be expandable. In particular, the seal is shaped in such a way that its volume can be increased after the assembly of the hollow structural element and transition piece. For example, the seal can be inflated, either pneumatically or hydraulically, by loading it with a filler material. Inside the seal, a volume can be reserved as a cavity. After assembly, this volume can be filled with the filling material under pressure, so that the seal closes the annular gap between the hollow structural element and the transition piece in the area of the cable bushings. Alternatively, the seal may include swellable (eg, clayey) material that swells upon contact with water.

According to one exemplary embodiment, it is proposed that the center point of the cable entry point of the hollow structural element is offset in the longitudinal direction of the hollow structural element relative to the center point of the cable entry point of the transition piece. The distance between the centers of the cable entries is preferably smaller than an opening radius of at least one of the cable entries. In particular, the cable entry point of the transition piece is in the longitudinal direction above the cable entry point of the hollow structural element if the transition piece is inserted into the hollow structural element. If the transition piece is on the outside in the overlapping area, the center point of the cable entry opening is below the center point of the cable entry opening of the hollow structural element. The cable routed from the top of the tower to the cable entries runs in a radius from inside the tower to outside the tower. As a result, the cable not only runs out of the tower radially to the central axis of the tower, but also extends in the longitudinal direction. This is taken into account by the offset cable bushings.

In particular, it is proposed that an upper edge of the cable bushing of the transition piece is arranged above a lower edge of the cable bushing of the hollow structural element. Such an offset can be at least 0.25 m, preferably 0.5 m. However, the offset is not so great that the cable bushings no longer overlap. There is always a clearance through both cable bushings.

According to one exemplary embodiment, it is proposed that the annular space between the hollow structural element and the transition piece is at least partially grouted. To prevent; that the cable bushings are adversely affected by grout material, it is proposed that an upper edge of the grout connection is below at least a lower edge of one of the cable bushings in the longitudinal direction of the hollow structural element. The grout connection is made in such a way that it is completely below the cable bushings in the overlap area. Possibly . another grout connection is to be provided above the top edges of the higher of the two cable entry openings. In this case, surrounding grout seals are to be provided at the height of the cable entry.

The cable bushings are overlapping, possibly concentric, at least the vertical axes of the cable bushings can lie in one plane. When the tubes of the transition piece and the hollow structural element are plugged into one another, it must be ensured that the cable ducts overlap when installed. When plugging into each other, however, the cable feed holes can be twisted against each other. This is particularly problematic in offshore applications, since it is not easy to see from the installation ship and/or it is difficult to control how the pipes twist against one another due to waves. Also the rope hanging down the pipes, especially the rope on which the The transition piece is not torsionally rigid, so that the pipes can twist in relation to one another.

To prevent this, an insertion aid can be provided, for example. An insertion aid can thus be provided on a front upper edge of the hollow structure element. This insertion aid can protrude radially inwards and can be arranged on the inner lateral surface of the hollow structural element. Alternatively or cumulatively, the insertion aid can also protrude beyond the end face and thus create a

The receiving funnel form the transition piece. The insertion aid can open in the form of a groove or a funnel away from the front edge of the hollow structural element in a funnel-shaped manner in order to enable the insertion aid of the transition piece to be threaded into it. The same can also apply to the insertion aid of the transition piece. This insertion aid can protrude radially outwards. The insertion aid of the transition piece can be arranged on the lower front edge and/or the outer lateral surface of the transition piece. This insertion aid can also point in a funnel shape away from the lower front edge of the transition piece.

It is also possible for an insertion aid to extend in the longitudinal direction on the transition piece at a distance from the outer wall. The distance from the outer wall of the insertion aid can be such that the insertion aid can be slipped over the hollow structural element. An insertion aid pointing radially outwards can then be provided on the hollow structural element, so that the insertion aids do not impede the threading process as such, in particular the insertion of the transition piece into the hollow structural element.

The insertion aids can be arranged at a distance from the annular space on the outer lateral surfaces of both the transition piece and the hollow structural element. The insertion aids have the effect that a relative orientation of the azimuth angle of the hollow structural element and the transition element is defined. The azimuth angles can be specified by an angular position about the longitudinal axis of the hollow structural element and the transition piece. According to one exemplary embodiment, it is proposed that the insertion aids have projections and/or recesses which project radially inward and/or radially outward and which engage in one another.

After the cable is led out of the hollow structural element, it hangs freely in the air or in the water, especially the open sea. In order to keep the length of the freely suspended cable as short as possible, a wedge-shaped structural element can be arranged on the floor at a radial distance from the hollow structural element. This wedge-shaped structural element is only arranged in a limited angular section around the hollow structural element, unlike the scour protection, which is poured completely around the hollow structural element.

The structural element is in particular formed from a mineral building material, as is described here. The construction element can take up the freely hanging cable in the manner of a ramp and lead it to the ground. Wedge-shaped means that the structural element for the cable forms a ramp that tapers in the radial direction away from the hollow structural element. The construction element is independently inventive and can be provided in combination with the other features described here. In particular, it can

Construction element can also be used to realize a cable bushing in only the transition piece outside the overlapping area. In this case, the free cable length is higher than with a cable bushing in the overlapping area, but this can be reduced by the construction element.

To accommodate the cable and in particular to prevent the cable from being pushed away from the structural element, for example by sea currents, a recess running in the radial direction can be arranged on a surface of the structural element for receiving the cable. The radial direction relates to the hollow structure element and points radially away from there. The cable, which is led out of one or both tubes can be inserted into the recess and thus be guided to the ground in a defined guide.

According to one exemplary embodiment, it is proposed that a radially inward-pointing stop be formed on the inner lateral surface of the wall in an end region of the hollow structural element. The stop can be formed by several "ledges" formed at angular distances from one another. The stop can be formed in particular by projections pointing radially towards the inside. The stop can be partially or completely circumferential. The stop serves as a stop for the transition piece, which is inserted into the Hollow structural element is used. A suitable axial arrangement of the stop ensures an annular gap between the inner lateral surface of the hollow structural element and the outer lateral surface of the transition piece, into which concrete or grout can be filled in order to form a grout connection. Alternatively, the ledges are on the outer Lateral surface to be arranged protruding radially outwards if the transition piece is slipped over the hollow structural element.As a further alternative, the plug-in connection is designed as a slip joint.

The hollow structural element preferably has an embedded depth of at least 7 m. This can be sufficient to base the hollow structural element sufficiently in the ground. Tie lengths between 7m and 20m are preferred.

According to one exemplary embodiment, it is proposed that the hollow structure element be produced monolithically over at least 50% of the longitudinal extent. It is also proposed that the hollow structural element is produced monolithically in the region of its lower end up to at least 5 m above the seabed/ground floor. The monolithic part of the hollow structural element is at least partially founded in the ground.

The hollow structural element can have a longitudinal extent in which the

Upper edge of the hollow structure element when installed at least 5m above the Seabed ends and in particular no more than 2 times the outer or inner diameter of the hollow structure element, in particular less than 3 times the outer or inner diameter of the hollow structure element ends above the seabed.

The monolithic end of the hollow structure element is preferably mechanically prestressed. The compressive force generated by prestressing in the concrete is such that the tensile forces occurring when ramming and/or vibrating a monolithic pile of the same mass and dimensions are compensated by at least 70%, in particular at least 85%. The prestress is preferably that prestressing force which is determined as the net prestressing force after deducting the relaxation of the prestressing steel and/or creep and shrinkage losses in the concrete and friction losses.

The compressive force generated by prestressing in the concrete is such that the compressive force generated by prestressing during operation and/or under maximum load in a monolithic pile of the same mass and dimensions is compensated (overpressed) by at least 45%, in particular at least 65%.

According to one exemplary embodiment, it is proposed that the hollow structural element be hollow-cylindrical. The structural integrity is increased by the cylindrical shape, so that the hollow structural element can absorb higher bending moments.

According to one exemplary embodiment, it is proposed that the building material contains cement, at least in part. In particular, the building material is concrete, which is a mixture of cement, gravel, sand and water and has hardened after pouring.

For good load-bearing capacity, it has been found that the water-cement ratio (w/c) of the building material is <0.45, in particular <0.35 or <0.3. The moments and shearing forces occurring in wind turbines are adequately absorbed by the hollow structural element in particular when the building material has a strength class of at least C40/50, preferably C70/85, in particular C100/115 according to EN 206 and EN1992.

A sufficient long-term stability of the foundation structure over the service life of the wind turbine, in particular in the case of permanent penetration by water, is achieved in particular in that the building material has a pore content (air pores) of less than 5%, preferably less than 3%, in particular less than 2%. The total porosity measured with mercury pressure porosity should be P 28d <12% by volume after 28 days and P _90d <10% by volume after 90 _days .

Sufficient load-bearing capacity of the hollow structural element is achieved in particular if the building material has a cement content of at least 350 kg/m ³ , preferably more than 450 kg/m ³ , in particular more than 650 kg/m ³ .

Particularly in the case of permanent water penetration when the foundation structure is installed offshore, a sufficient service life is achieved if the building material has a porosity of P _28d <12% by volume in a mercury pressure porosimetric measurement. P _28d is a measurement over 28 days. The porosity is preferably also less than 10% by volume. At P _90d , ie a measurement over 90 days, the porosity is preferably <10% by volume, in particular <8% by volume.

According to one embodiment, it is proposed that the wall is mechanically prestressed. Cracks are suppressed by the prestressing and the surfaces are thus kept largely free of tensile stress, which is particularly advantageous in the case of fluctuating torque loads. The prestressing force is preferably 5%, in particular more than 15%, greater than the compressive strength of the wall. The prestressing force is preferably applied in the longitudinal direction For increased stability under dynamic environmental conditions, it is suggested that the building material be reinforced with metal. The metallic reinforcement is in particular a steel reinforcement. The reinforcement can be provided by fibers or reinforcing bars. Fiber reinforcement can also be achieved with carbon fibre, glass fiber or metal fibre.

The reinforcement can be such that at 90% of the measuring points, preferably at 98% of the measuring points, it has at least more than 26 mm, preferably at least more than 40 mm, of concrete cover.

The building material can be reinforced with ferritic stainless steel reinforcement. The reinforcement cannot exceed a chromium content of 18M%. The reinforcement can contain molybdenum components.

The building material can be reinforced with austenitic stainless reinforcing steel. The reinforcement can have at least 5% by mass, in particular between 5% by mass and 14% by mass, nickel and/or between 12% by mass and 22% by mass, in particular 15% by mass and 20% by mass, of chromium.

The building material can be reinforced with ferritic-austenitic stainless reinforcing steel. The reinforcement can have at least 18 M%, in particular between 15 M%-20 M% chromium and 2 M%-8 M% nickel and optionally molybdenum.

According to one exemplary embodiment, it is proposed that the upper end face be reinforced with metal, in particular that a metallic reinforcement protrudes from the upper end face. Over the top will do that

Established hollow structural element in the ground, in particular rammed or vibrated. This means that the mechanical load on the top face of the foundation itself is very high. In order to withstand these mechanical loads and in particular to prevent damage, metallic reinforcement of the end face is preferred. If a circumferential ridge is provided that protrudes from the front face, the foundation tool, either the Vibration tool or the ramming tool rest on this reinforcement and not directly on the building material of the hollow structure door element. Since a metallic reinforcement is considerably more ductile than a mineral building material, this prevents damage when founding.

According to one exemplary embodiment, it is proposed that the density of the reinforcement in an end region of the hollow structural element is greater on its upper and/or lower end face than in a central region of the hollow structural element. The mechanical load on the end faces is higher than in a central area, especially during the foundation. The foundation tool, in particular a ramming tool or a vibration tool, acts on the top face. The hollow structural element is rammed into the ground on the underside end face and the underside end face has to displace the ground. The reinforcement is larger on these two end faces, ie the density of the reinforcement is increased compared to a central area.

For a landing platform or an installation platform, an apron pointing radially outwards can be formed on the outer lateral surface of the wall in an end region of the hollow structural element. The skirt can be partially or fully wraparound. In particular, the skirt is spaced apart from the upper face in the axial direction.

For increased stability, it is suggested that the building material is sealed, in particular with a sealing foil. Such a sealing film can be, for example, an aluminum butyl sealing film.

Another aspect that can be combined with all of the features described here can be a cable routing within a landing platform (boat landing). A boat landing platform can be provided on the transition piece, in particular as an at least partially encircling platform pointing radially outwards. This platform is attached to the transition piece. The platform is protected by so-called fender Pipes protected from impacts by ships docking The fender pipes are attached to the transition piece at a radial distance from the latter, in particular welded. Together with the transition piece, the fender tubes span an area within which the landing platform is at least partially arranged.

It is now possible to provide these tubes not only for protection against impact from berthing ships, but also as cable ducts. For example, it is possible to extend the fender tubes, which are otherwise limited in length, beyond the hollow structural element. As mentioned, the fender tubes are in a radial condition to the outer surface of the transition piece. It is proposed that this radial distance is greater than the radial distance of the outer wall of the hollow structural element from the outer wall of the transition piece. Thus, when assembling the fender tubes or when assembling the transition piece together with the fender tubes, it is ensured that the fender tubes do not strike the hollow structural element.

The fender tubes run on the outside of the hollow structural element. In particular, the fender tubes are arranged in an overlapping area, extending beyond the hollow structural element in the direction of the ground. A cable lowered from the tower can be routed out of the tower above the fender tubes and routed in the fender tubes to the bottom outlet. At the lower outlet of the fender tubes, the cable can then be laid freely hanging or routed on the floor.

In addition or as an alternative, it is possible for ladder stiles on the landing platform to be used as grout lines. Such ladder stiles are hollow tubes which are arranged on the landing platform. The distance between the ladder rails and the transition piece is less than the distance between the fender tubes. In particular, the ladder rails can be guided up to the joint between the hollow structural element and the transition piece. The grout material can be fed into the annular gap between the hollow structural element and the transition piece via the ladder rails. For this purpose, the ladder rails can be provided with funnels on the top, for example, in order to be able to fill in the grout material particularly easily.

The object is explained in more detail below with reference to a drawing showing exemplary embodiments. Show in the drawing:

1 shows a wind turbine with a wind turbine foundation structure;

2 shows a schematic view of an overlapping area;

Figure 3 is a view of overlapping cable entries;

4a shows a sectional view through a cable bushing;

4b shows a sectional view through a cable bushing;

5 shows cable bushings with a radial seal;

6a shows a wind turbine with a cable led out;

6b shows a cable on a construction element;

7 shows a boat landing platform;

Fig. 8a, b Examples of insertion aids.

Fig. 1 shows a wind turbine 2, which is founded offshore. All statements made here apply to offshore foundation structures as well as to onshore foundation structures. The wind turbine 2 is founded in a seabed 6 via a wind turbine foundation structure. A hollow structural element 4 is founded in the seabed with an embedded length 4a. The hollow structural member 4 is connected to a transition piece 10, for example via a grout connection or a slip-joint connection, which is conventionally known. The transition piece 10 protrudes above the water surface 8.

A wind turbine 12 is arranged here by way of example on the transition piece 10, but a substation, a transformer station or the like can also be provided. In order to establish the hollow structural element 4 , it is rammed or vibrated into the seabed 6

As shown schematically and greatly simplified in FIG. 2, the transition piece 10 is inserted into the hollow structural element 4 with an overlapping region 10b. The transition piece 10 protrudes from the hollow structure element 4 with a transition area 10a.

The hollow structure element 4 is formed in particular as a monopile. The hollow structure element 4 has a wall 4c. The wall 4c is formed in particular from concrete

The transition piece 10 is also designed as a hollow structural element and its wall 10c is preferably made of steel.

A connection between the hollow structure element 4 and the transition piece 10 takes place in the so-called grout joint or slip joint.

The grout-joint process is presented here as an example. However, the statements on the cable bushings apply equally to slip-joint connections. In the grout-joint method, an annular space (annular gap) 14, which is shown greatly enlarged in FIG. 2, between the hollow structural element 4 and the transition piece 10 is filled with a grout (mortar). This method is known per se.

However, there is a problem with grout joints and slip joints if a cable 16, which is routed down from the wind turbine 12 inside the transition piece 10, is to be routed to the outside in the upper lap area 10b, i.e. through the wall 10c of the transition piece 10 and the wall 4c of the hollow structural element 4. For this purpose, cable bushings are to be provided in both walls 4c, 10c. These must be aligned with each other and the

Hollow structure elements 4, 10 must not be rotated in relation to one another. In addition, in the case of a grout connection, the grout material must not leak out of the cable bushings.

Suitable measures such as insertion aids, alignment aids or the like can align the hollow structural elements 4, 10 with one another.

To guide the cable 16 through, the cable bushings are aligned so that they overlap with one another, as shown in FIG. 3 . It can be seen in FIG. 3 that the transition piece 10 is inserted into the hollow structural element 4 . On the bottom side of the transition piece 10 , this is mounted in the hollow structural element 4 on stops 18 pointing inwards. The hollow structural element 4 is aligned with the transition piece 10 in such a way that the cable bushings 20a, 20b overlap.

The cable bushing 20a on the transition piece 10 breaks through the wall 10c. The cable bushing 20b on the hollow structural element 4 breaks through the wall 4c.

The cable bushing 20a on the transition piece 10 can be offset in the longitudinal direction with respect to the cable bushing 20b of the hollow structural element 4 . This However, offset is preferably smaller than a radius of at least one of

Cable bushings 20a, b, in any case smaller than the diameter of the smallest of the cable bushings 20a, b.

The cable bushings 20a, b are aligned with one another in their angular position relative to the longitudinal axis of the hollow structural element 4 and the transition piece 10 . The cable 16 can be passed through the cable bushings 20a, b.

Such a cable bushing is shown in FIG. 4a. In this case, the transition piece 10 is inserted into the hollow structural element 4 and lies on the stops 18 which point radially inward. The cable 16 is guided within the transition piece 10 into the overlapping area 10b. In the overlapping area 10b, the cable bushings 20a, b are aligned with one another, so that the cable 16 can be passed through the two walls 4c, 10c.

As already explained at the outset, the annular space 14 is filled with filling material 22 in the case of a grout connection. The filling material 22 is introduced into the annular space 14 after the transition piece 10 has been inserted into the hollow structural element 4 .

In order to prevent the filling material 22 from escaping at the cable bushings 20a, b, a circumferential seal 24 is proposed. The seal 24 is arranged circumferentially in the annular space 14 and seals the annular space 14 vertically.

Another cable bushing is shown in FIG. 4b. Here, the hollow structural element 4 is inserted into the transition piece 10 and lies on the stops 18, which point radially outwards.

In contrast to FIGS. 3 and 4a, the transition piece 10 is mounted on the bottom on the hollow structural element 4 on stops 18 pointing radially outwards. That Hollow structural element 4 is aligned with the transition piece 10 so that the

Cable bushings 20a, 20b overlap each other.

The cable bushing 20a on the transition piece 10 can be offset in the longitudinal direction with respect to the cable bushing 20b of the hollow structural element 4 . However, unlike in FIG. 4a, this offset is such that the cable bushing 20b lies below the cable bushing 20a.

As already explained at the outset, the annular space 14 is filled with filling material 22 in the case of a grout connection. The filling material 22 is introduced into the annular space 14 after the hollow structural element 4 has been inserted into the transition piece 10 .

A further possibility of sealing the cable bushings 20a, 20b is shown in FIG. Again, the transition piece 10 is in this

Inserted hollow structural element 4 and the cable bushings 20a, 20b overlap. In Fig. 5 a complete overlap is shown. A seal 24 is provided in the annular space 14 radially surrounding the cable bushing 20a, 20b. The seal 24 thus does not run horizontally around the annular space 14, but instead runs radially around the cable bushings 20a, b. Such a seal 22 also prevents filling material 22 from penetrating into the cable bushing 20a, b.

A further possibility of protecting the cable from damage is shown in FIG. 6a. It can be seen here that the hollow structure element 4 is provided with a scour protection 26 on the seabed 6 . The scour protection 26 is placed around the hollow structural element 4 all the way around on the sea floor 6 . The cable 16 is in the manner shown through the cable bushing 20a, b from the wind turbine 2 led out. A wedge-shaped construction element 28 is proposed in order to prevent the free length of cable outside the wind turbine 2 from becoming too long and thus the cable 16 being subjected to excessive mechanical stress due to currents.

The structural element 28 is only arranged in an angular section around the wind turbine 2, unlike the scour protection 26, which is completely circumferential. The structural element 28 is such that it has a lower construction height radially to the wind turbine 2 with an increasing radius. As a result of this wedge shape, the cable 16 can be picked up away from the seabed 6 at a greater height and guided to the seabed 6 in a mechanically stabilized manner.

6b shows a schematic plan view of a structural element 28. The scour protection 26 is all around the hollow structural element 4. The structural element 28 is provided in only a limited angular section around the hollow structural element 4. FIG. A groove 28a can be provided on the surface of the construction element 28 facing away from the seabed 6 . The groove 28a can also be referred to as a recess or the like. The cable 16 can be inserted into this groove 28a so that it is fixed on the structural element 28 and cannot be pushed down from the structural element 28 in particular by sea currents. The construction element 28 with all its features can be independently inventive and freely combined with all the features described here.

Another independent aspect of the invention, which can be combined with all of the aspects described here, but which can also be independently inventive, is shown in FIG. A boat landing platform 30 can be arranged on the transition piece 10 . The boat landing platform 30 is above the water surface 8. A ladder 32 and fender tubes 34 are arranged on the boat landing platform 30. The ladder 32 can be attached directly to the platform 30 be attached. Rails 32a can be provided as tubes on the ladder. The spar 32a can have a funnel-shaped opening 32b on one side. This funnel-shaped opening can be formed to receive filling material 22 . Filling material 22 can be guided through the spar 32a as far as the annular gap 14 . The spar 32a can be shaped in such a way that its lower opening 32c is shaped into the annular gap 14 or towards the annular gap 14 . As a result, filling material 22 can be filled into annular gap 14 via spar 32a in order to form a grout connection.

Alternatively or in addition to the cable routing with the cable bushings 20a, b, the cable 16 can also be routed within the fender tube 34. The fender tube 34 is preferably attached directly to the transition piece 10 . The fender tube can be guided from the boat landing platform to below the water surface 8. The fender tube 34 can be arranged at a distance 34a from the transition piece 10, this distance 34a being greater than the difference in the radius between the hollow structural element 4 and the transition piece 10. Around the fender tube 34 on the hollow structural element 4 lead past, this is further away from the transition piece 10 than the radius of the hollow structure element 4 is greater than the radius of the transition piece 10.

8a shows a possible insertion aid. A projection 40 pointing radially outwards is provided on the bottom side of the transition piece 10 . An alignment aid 42 is provided on a front edge 4d of the hollow structure element 4 . The alignment aid 42 can be shaped in such a way that it tapers away from the front edge 4d. The alignment aid can also have a groove into which the projection 40 can engage, as can be seen in the middle image.

In the area of the stop 18 , a receptacle 44 can be arranged on the inner lateral surface of the hollow structural element 4 , pointing radially inwards. In this recording, in the joined state, as can be seen in the right picture, the Projection 40 lie. This ensures an angular alignment between the hollow structure element 4 and the transition piece 10 .

8a on the left shows a cross section through transition piece 10 and hollow structure element 4 on the one hand in the non-joined state and on the other hand in the joined state. On the right the individual steps of joining are shown from left to right.

In FIG. 8b, the receptacle 44 and the projection 42 are formed in accordance with FIG. 8a. These serve to align the transition piece 10 and the hollow structure element 4 at the correct angle.

In contrast to FIG. 8 a , the insertion aid is formed on an outer lateral surface of the transition piece 10 . A rod-shaped element 50 can extend in the longitudinal direction of the transition piece 10 towards the bottom of the transition piece 10 at a radial distance from the outer lateral surface of the transition piece 10 .

Correspondingly, a receptacle 52 can be provided on the hollow structure element 4 on the front edge 4d. The receptacle 52 can extend from the front edge 4d in the longitudinal direction of the hollow structural element 4 and have a groove or opening. In this groove or opening, the rod-shaped element 50 can engage during insertion, so that the transition piece 10 in the.

Hollow structural element 4 can be introduced. The receptacle 52 can be a sleeve or a tube, for example, which accommodates the rod-shaped element 50 . The receptacle 52 can have a radially widening opening in order to facilitate insertion of the rod-shaped element 50 . When the rod-shaped element 50 is inserted into the receptacle 52, the radial position between the transition piece 10 and the hollow structural element 4 is defined by the receptacle 52. As a result, these two elements can be aligned with one another and, in particular, their longitudinal axes can be aligned with one another, in particular aligned essentially collinearly with one another. Reference List

2 wind turbine

4 hollow structural element

4a binding length

4b outstanding length

4c wall

4d face edge

6 seabed

8 water surface

10 transition piece

10a transition area

10b overlap area

10c wall

14 annulus

16 cables

18 stop

20a, b cable bushing

22 filler

24 seal

26 scour protection

28 construction element

28a groove

30 landing platform

32 conductors

32a Holm

32b opening

32c opening

34 fender tube

40 lead 42 alignment aid 44 receptacle 50 rod-shaped element 52 receptacle

Claims

P a t e n t claims 1. Wind power plant foundation structure comprising, a hollow structural element with a circumferential wall extending in the longitudinal direction, wherein a first cable bushing that breaks through the wall is arranged in the wall, a transition piece with an overlap area that protrudes into the hollow structural element and a transition area that protrudes at the front protruding from the hollow structural element and a circumferential wall extending in the longitudinal direction, with a second cable bushing breaking through the wall being arranged in the overlapping area in the wall, characterized in that the first and the second cable bushing in the assembled state of the hollow structural element and transition piece at least partially overlap one another issue.

2. A wind turbine foundation structure according to any one of the preceding claims, characterized in that a cable is routed from inside the transition piece through the first and second cable bushings.

3. Wind turbine foundation structure according to one of the preceding claims, characterized in that the cable bushing of the hollow structural element in the installed state between 1.0m and 5m, preferably between 1.5m and 3.5m above the

Seeboden lies

4. Wind turbine foundation structure according to one of the preceding claims, characterized in that in an annular space between the inner lateral surface of the hollow structural element and the outer lateral surface of the transition piece, a seal lying against the lateral surfaces is arranged circumferentially, in particular that in the longitudinal direction of the hollow structural element a seal is above and/or a seal is arranged below the cable bushing.

5. Wind turbine foundation structure according to one of the preceding claims, characterized in that in an annular space between the inner surface of the hollow structural element and the outer surface of the transition piece at a radial distance from the cable bushings around the

Cable bushings ongoing seal is arranged, in particular that the seal encloses the cable bushing in a circular or elliptical manner.

6. Wind turbine foundation structure according to one of the preceding claims, characterized in that

- That the seal is expandable in such a way that the volume of the seal can be increased after the assembly of the hollow structural element and transition piece, in particular that the seal is loaded pneumatically or hydraulically with a filling material.

7. Wind turbine foundation structure according to one of the preceding claims, characterized in that the center point of the cable entry of the hollow structural element is offset in the longitudinal direction of the hollow structural element to the center point of the cable entry point of the transition piece, the distance between the center points being smaller than an opening radius of at least one of the cable entries.

8. Wind turbine foundation structure according to one of the preceding claims, characterized in that the annular space between the hollow structural element and the transition piece is at least partially greyed, with an upper edge of the grout connection being below at least a lower edge of one of the cable bushings in the longitudinal direction of the hollow structural element.

9. Wind turbine foundation structure according to one of the preceding claims, characterized in that insertion aids arranged on an upper front edge of the hollow structural element interact with insertion aids arranged on a lower front edge of the transition piece in such a way that a relative orientation of the azimuth angle of the hollow structural element and transition piece is defined.

10. Wind turbine foundation structure according to one of the preceding claims, characterized in that the insertion aids are interlocking projections and recesses projecting radially inwards and radially outwards.

11. Wind turbine foundation structure according to one of the preceding claims, characterized in that a wedge-shaped structural element is arranged at a radial distance from the hollow structural element, the structural element tapering away from the hollow structural element,

12. Wind turbine foundation structure according to one of the preceding claims, characterized in that a recess running in the radial direction for receiving the cable is arranged on a surface of the structural element

13. Wind turbine foundation structure according to one of the preceding claims, characterized in that a radially inward-pointing stop is formed on the inner lateral surface of the wall in an end region of the hollow structural element. 14. Wind turbine foundation structure according to one of the preceding claims, characterized in that the hollow structural element is hollow-cylindrical 15. Wind turbine foundation structure according to one of the preceding claims, characterized in that the hollow structural element consists at least in parts of a mineral

building material is shaped and/or that the building material contains at least some cement and/or that the water/cement ratio (w/c) of the building material is less than 0.45, in particular less than 0.35 or less than 0.3, and/or that the building material has a strength class of at least C40/50

C70/80, in particular C100/115 according to EN 206 and EN 1992 and/or that the building material has a pore content (air pores) of less than 5%, preferably less than 3%, in particular less than 2%, and/or that the Building material has a cement content of at least 350 kg/m ³ , preferably more than 450 kg/m ³ , in particular more than 550 kg/m ³ , in particular up to

600lg/m ³ , and/or that the building material has a porosity P _28d less than 12 vol%, in particular less than 10 vol% and P _90d less than 10 vol%, in particular less than 8 vol% in a mercury pressure porosimetric measurement preceding claims, characterized in that that the wall is mechanically prestressed, in particular with a prestressing force of more than 5%, in particular more than 15% of the compressive strength of the wall, the prestressing force preferably being applied in the longitudinal direction.

17. Wind turbine foundation structure according to one of the preceding claims, characterized in that the building material is metallically reinforced. and/or that the reinforcement (at 98% of all measuring points) has a concrete cover of not less than 26mm, preferably not less than 40mm and/or that the building material is reinforced with ferritic stainless steel reinforcement, the chromium content of which does not exceed 18M% and possibly contain molybdenum components and/or that the building material is reinforced with austenitic stainless reinforcing steel, which contains at least 5%, in particular with 8% up to 14M% nickel and with 12M%-22M%, in particular 15% - 20% chromium, and/or that the building material is reinforced with ferritic-austenitic reinforced with stainless steel reinforcement containing at least 18M% chromium and 2%-8% nickel and possibly molybdenum.

18. Wind turbine foundation structure according to one of the preceding claims, characterized in that the upper end face of the hollow structural element is metallically reinforced, in particular that a metallic reinforcement protrudes from the upper end face, in particular protrudes completely circumferentially from the upper end face and/or that the density the reinforcement in an end region of the hollow structure element is larger on its upper and/or lower end face than in a central region of the hollow structure element.

19. Wind turbine foundation structure according to one of the preceding claims, characterized in that that on the outer surface of the wall in an end area of the

Hollow structural element is formed a collar pointing radially outwards 20. Wind turbine foundation structure according to one of the preceding claims, characterized in that the building material is sealed, in particular with a sealing film.