MONO PILE FOUNDATION
The invention relates to a monopile foundation for an offshore structure, in particular for a wind turbine, with a foundation pile for supporting the structure and a foundation reinforcement adjoining the foundation pile on the outside and designed for subsequent attachment to the foundation pile, wherein the foundation reinforcement has a sleeve, a collar and at least one support, wherein the sleeve is associated with the foundation pile and the collar is held at a distance outwards from the sleeve by the at least one support, wherein the foundation pile has a foundation section for introduction into the seabed and a reinforcement section for connecting the foundation pile to the sleeve above the seabed, and wherein the collar and/or the sleeve is designed for at least partial introduction into the seabed.
Furthermore, the invention relates to a monopile foundation installation for an offshore structure, in particular for a wind turbine, with such a monopile foundation anchored in a seabed.
Furthermore, the invention relates to a method for erecting an offshore structure, in particular for a wind turbine, with such a monopile foundation.
Different variants are known for the foundation structure of offshore structures, such as wind turbines in particular.
For water depths between 4 m and 50 m, so-called monopiles in particular, i.e., individual foundation piles, have proven to be an economical solution.
This type of foundation is usually a foundation pile in the form of a steel tube with a diameter of a plurality of metres, which is rammed with its open end into the seabed or inserted into the seabed using a vibration method.
In order to ensure sufficient stability of the foundation pile that supports the in particular wind turbine, the foundation pile is usually driven into the seabed over at least approximately half its length, for instance by m-50 m.
However, this is only possible with reasonable effort in sandy or cohesive soils.
For the construction of offshore structures in places where it is to be expected that the foundation pile will hit rock when it is introduced into the seabed, additional measures have been taken to reduce the embedding length or depth of penetration of the foundation piles into the seabed without significantly impairing the rigidity of the monopile foundation.
For this purpose, a foundation reinforcement has been proposed in WO 2016/198272 A1 or also in EP 3 103 924 A1, which has a sleeve lying on the outside of the foundation pile and a collar partially embedded in the seabed.
The collar and the sleeve are held at a predetermined distance from one another by means of supports.
The foundation reinforcement thus forms a kind of base for the foundation pile received in the sleeve, which increases the rigidity of the foundation and supports the foundation pile against swaying movements on the seabed.
Therefore, the embedding length of the foundation pile in the seabed can be decreased.
The corresponding monopile foundation is erected by first driving the foundation reinforcement with the collar into the seabed.
The foundation pile is then passed through the sleeve of the foundation reinforcement, which protrudes upwards from the seabed and opposite the collar, and is driven into the seabed.
This can be done by vibration or by ramming.
After the foundation pile has been driven into the seabed, the gap between the foundation pile and the sleeve is filled in.
However, even monopile foundations that can be driven deep enough into sandy seabeds and therefore do not require foundation reinforcement can loosen over time.
A foundation pile can loosen, for example, as a result of rhythmically occurring loads that can be caused by wind and/or waves.
Alternatively or additionally, the sea current can be accelerated in the vicinity of the foundation piles, such that the seabed is eroded and depressions in the seabed, for example “scours”, are formed.
Measures must then be taken to ensure the stability of the offshore structure.
In addition, it is difficult to determine whether the foundation pile can be driven into the seabed to the desired length during founding.
Even if the seabed is in itself sandy and well suited for founding monopile foundations, it can happen that the foundation pile hits rock, for example in the form of erratics.
It is also conceivable for soils to be denser and more rigid than expected and therefore the selected installation device is not powerful enough for the installation.
This can prevent the desired embedding depth of the foundation pile in the seabed from not being reached.
Furthermore, offshore structures, such as wind turbines, are dismantled after some time.
Newer and/or larger offshore structures can then be installed at the same location if necessary.
The existing monopile foundations can only be reused to a limited extent for the installation of new offshore structures.
Often these are no longer stable enough or newer and larger offshore structures require monopile foundations with significantly higher stability than previous offshore structures.
Another problem when reusing monopile foundations can be the cabling of the monopile foundations, which can make retrofitting monopile foundations with foundation reinforcements difficult or even impossible.
It may be necessary to disassemble the corresponding submarine cables laid on the seabed and reinstall them later.
If necessary, the submarine cables must be reinstalled at a different location due to subsequently added foundation reinforcement.
Even if the submarine cables have to be removed to subsequently install foundation reinforcement, this can involve varying levels of effort depending on the existing monopile foundation.
Corresponding submarine cables can be designed, for example, as power cables or for transporting information.
In the case of wind turbines, the electrical power generated is conducted away.
When it comes to submarine cables, it should also be noted that they must be inserted into the monopile foundation at certain heights above the seabed and with certain minimum radii so that undesirable damage to the submarine cables does not occur during operation of the offshore structure, even over many years.
Erecting monopiles is therefore not yet possible in a satisfactory manner in all cases.
The present invention is therefore based on the object of designing and developing the monopile foundation, the monopile foundation installation and the method of the type mentioned at the outset and previously explained in more detail in such a way that the foundation of monopiles can be carried out in a more satisfactory manner.
This object is achieved with a monopile foundation according to the preamble of claim 1 in that a feed- through opening is provided in the foundation pile in the region of the reinforcement section and in that the sleeve of the foundation reinforcement is provided in the reinforcement section so as not to close the feed-through hole.
The stated object is further achieved according to claim 14 by a monopile foundation installation for an offshore structure, in particular for a wind turbine, with a monopile foundation anchored in a seabed according to any one of claims 1 to 13, wherein the foundation pile is inserted with its foundation section into the seabed, and wherein the collar and/or the sleeve is inserted at least partially, in particular fully, into the seabed.
Furthermore, the aforementioned object is achieved according to claim 15 by a method for erecting an offshore structure, in particular for a wind turbine, with a monopile foundation according to any one of claims 1 to 13
- in which an already existing offshore structure is removed from a foundation pile to support the structure and a new offshore structure is erected on the foundation pile,
- in which the foundation reinforcement is subsequently attached to the foundation pile, already partially inserted in the seabed, of the already existing offshore structure, and
- in which the collar and/or the sleeve of the foundation reinforcement is introduced, preferably via vibration, at least partially into the seabed.
If the feed-through opening for a submarine cable is provided in the region of the reinforcement section in the foundation pile, this enables an expedient and simple installation of the submarine cable, wherein the submarine cable can then be assembled in such a way that there is no risk of sustained damage to the submarine cable, even over long periods of time.
This also applies if the height of the seabed changes or an increased sea current affects the foundation pile.
The sleeve of the foundation reinforcement, which is to be subsequently assembled, is also designed so that it does not close the feed- through hole in the reinforcement section.
In this way it is achieved that the submarine cable routed through the feed-through opening does not have to be uninstalled for the purpose of subsequent installation of the foundation reinforcement.
Rather, the foundation reinforcement can be assembled later if the submarine cable is already installed.
Alternatively, partial disassembly of the submarine cable may be necessary.
However, the submarine cable can be reassembled using the same feed-through opening, and the assembly can also be carried out with relatively little effort.
Furthermore, the advantages mentioned are also achieved if, in the case of a monopile foundation, an existing foundation reinforcement is to be subsequently replaced by another, in particular by a larger, foundation reinforcement.
In order to simplify the assembly of the foundation reinforcement, the foundation reinforcement can, for example, be provided with an opening or recess in the region of the feed-through opening in the foundation pile.
The submarine cable can then be guided through this opening or recess in the foundation reinforcement on the one hand and through the feed-through opening in the reinforcement section of the foundation pile on the other hand.
It is therefore not necessary to completely disassemble the submarine cable and/or reassemble it elsewhere to assemble the foundation reinforcement.
For example, it is not necessary to lay the feed-through opening for the submarine cable in the foundation section of the foundation pile for insertion into the seabed or in the region of the offshore structure above the foundation pile or above the reinforcement section of the foundation pile in order to enable subsequent assembly of a foundation reinforcement.
The foundation pile of the monopile foundation is introduced into the seabed with its foundation section.
In addition, the collar of the foundation reinforcement is at least partially introduced into the seabed in order to support the foundation reinforcement in the seabed and to stabilise the monopile foundation.
The reinforcement section of the foundation pile above the seabed is connected to the sleeve of the foundation reinforcement.
In this case, a preferred load dissipation is achieved if the sleeve is arranged in a region above the seabed and preferably also at least partially above the collar.
The feed-through opening is also provided in the region of the reinforcement section.
The reinforcement section is not necessarily limited to the section of the foundation pile where the sleeve of the foundation reinforcement actually engages the foundation pile.
Rather, the reinforcement section can be the region of the foundation pile of the monopile foundation, which is arranged above the foundation section.
The actual offshore structure placed on the monopile foundation can then be connected above the reinforcement section.
In the case of the monopile foundation, the sleeve and/or the collar can preferably have a circular or oval cross-section.
A circular cross-section enables forces to be diverted very evenly from the foundation pile via the foundation reinforcement to the seabed.
However, in some cases there will be a dominant wave or wind direction, so that the forces introduced into the foundation pile will have a preferred direction.
In this case, it may be expedient to use a sleeve and/or a collar with an oval cross-section.
This applies in particular when the greater lengthwise extent of the oval cross-section points in the preferential direction of the forces introduced into the foundation pile.
In the present case, the cross-section is preferably arranged at least substantially in the horizontal.
In the direction in a cross-section perpendicular to the foundation pile, the sleeve and/or the collar can alternatively or additionally be of annular, cylindrical or conical design.
In this way, a very rigid foundation reinforcement will be obtained, which is also particularly suitable for dissipating the forces to the seabed.
Which shape of sleeve and/or collar is to be preferred depends on the type and direction of the forces to be dissipated, on the type of offshore structure supported by the foundation pile and, if applicable, on manufacturing and transport requirements.
In order to achieve appropriate reinforcement of the foundation pile, it is possible for the foundation reinforcement, the sleeve and/or the collar to extend circumferentially around the foundation pile over an angular range of at least 60°, preferably at least 120°, more preferably at least 180°, in particular at least 260°. Extending around the foundation pile over a smaller angular range can be sufficient if the foundation pile only has to be supported in certain directions.
The greater the corresponding angular range, the more extensively and in all the more directions the foundation pile can be supported.
Depending on the particular seabed, a larger angular range can to a certain extent complicate or even prevent introduction into the seabed.
A very stable monopile foundation for uniformly dissipating forces can be obtained if the sleeve, the collar and/or the foundation pile are designed at least substantially concentrically with one another.
In addition, a stable foundation pile that is easy to set up can be obtained if the pile takes the form of a hollow profile.
For the sake of simplicity and for better force dissipation, the corresponding hollow profile can be cylindrical or conical, depending on the particular erection site and/or depending on the particular offshore structure supported by the foundation pile.
For the sake of clarity and to avoid unnecessary repetition, the monopile foundation, the monopile foundation installation and the method are described together below, without always distinguishing in detail between the monopile foundation, the monopile foundation installation and the method.
For the person skilled in the art, however, it is clear from the context which features are particularly preferred in each case with respect to the monopile foundation, the monopile foundation installation and the method.
In many cases it will be useful for bracing reasons if the collar is at least partially introduced into the seabed to prepare the monopile foundation installation.
However, for further stiffening, for example, it may be preferred if the sleeve is also at least partially introduced into the seabed.
Under certain circumstances, for example, to facilitate the introduction of the foundation reinforcement, it may be useful if only the sleeve, but not also the collar, is at least partially introduced into the seabed.
In a first particularly preferred embodiment of the monopile foundation, the foundation reinforcement is designed to be pushed onto the reinforcement section of the foundation pile introduced in the seabed.
In this way, the subsequent assembly of the foundation reinforcement can be made considerably easier; this is particularly true if the offshore structure has not yet been assembled on the monopile foundation.
If necessary, a previous offshore structure can also have been separated from the monopile foundation, then the foundation reinforcement can simply be pushed onto the reinforcement section of the foundation pile before the new offshore structure is assembled on the foundation pile.
As a result of the foundation reinforcement that has been assembled in the meantime, the offshore structure can, if necessary, be significantly larger and heavier than the original offshore structure without jeopardising the stability of the monopile foundation.
Alternatively or additionally, the foundation pile can also be designed to be pushed through the foundation reinforcement.
Then, for example, the foundation reinforcement can first be introduced into the seabed before the foundation pile is pushed through the foundation reinforcement.
Regardless of this, the foundation pile can be pushed through the foundation reinforcement when it is introduced into the seabed in order to simplify the preparation of the foundation.
The foundation reinforcement has either already been introduced into the seabed or not yet.
However, the foundation pile can also be pushed through the foundation reinforcement without the foundation pile or the foundation reinforcement being introduced into the seabed.
Alternatively or additionally, the foundation reinforcement can have a plurality of, in particular two, three or four, reinforcing elements to be arranged next to one another in the circumferential direction of the foundation pile, and the sides of the reinforcing elements that are adjacent to one another in the circumferential direction can be designed for form-fitting, articulated and/or force-fitting connection to one another. This multi-part design of the foundation reinforcement enables a particularly simple and reliable retrofitting of a monopile foundation with a foundation reinforcement. Thanks to the multi- part design of the foundation reinforcement, it is possible to subsequently introduce the individual reinforcement elements from the outside and then connect the individual reinforcement elements to form a common foundation reinforcement. However, this can preferably be done in different ways in a form-fitting, articulated and/or force-fitting manner. The individual reinforcement elements are, for example, distributed in the circumferential direction around the foundation pile and are thus connected to one another in a direction perpendicular or transverse to the longitudinal axis of the foundation pile. The connection is preferably provided in such a way that the adjacent reinforcement elements are fixed or locked to one another both in the circumferential direction and in the radial direction, starting from the longitudinal axis of the foundation pile. In order to keep assembly costs low, it is particularly preferred in this connection if only two, three or four reinforcement elements are provided and joined together to form a foundation reinforcement. The foundation reinforcement is made up of reinforcement elements which are distributed around the foundation pile in the circumferential direction and are adjacent to one another in the circumferential direction. The reinforcement elements are connected to one another in a form-fitting, articulated and/or force-fitting manner on sides of the respective adjacent reinforcement elements that are adjacent to one another in the circumferential direction. Due to the multi-part design of the foundation reinforcement, the advantages of the monopile foundation and the monopile foundation installation are utilised to a particular extent when the foundation pile is inserted into the seabed with the foundation section and only then are the collars of a plurality of, in particular two, three or four, reinforcement elements successively or jointly and at least partially introduced into the seabed in the circumferential direction of the foundation pile. In this case, the foundation pile and/or the reinforcement elements can preferably be embedded using the vibration method or by pulse ramming. Alternatively, the foundation pile and/or the reinforcement elements can also be driven by water-jetting into the seabed or embedded in the seabed in some other way. Assembly effort can be further reduced if the reinforcement elements are successively positioned next to one another by at least partial introduction into the seabed and the adjacent sides of the adjacent reinforcement elements are connected to one another in a form-fitting and/or force-fitting manner. In this case, it is particularly simple and expedient if the mutually adjacent reinforcement elements are connected to one another by at least partial introduction into the seabed.
Therefore, assembly effort can also be further reduced if the reinforcement elements are already positioned relative to one another, in particular connected to one another, before they are introduced into the seabed.
If necessary, the mutually adjacent sides of the adjoining reinforcement elements can be connected to one another in a form-fitting and/or force-fitting manner.
However, it is alternatively or additionally particularly simple and expedient for mutually adjacent reinforcement elements to be connected to one another in articulated manner on the sides facing one another.
In the case of an articulated connection, it is possible, for example, to place a reinforcement element on the foundation pile and to pivot another reinforcement element about the corresponding joint in such a way that the further reinforcement element is also placed on the foundation pile.
It is particularly useful if the articulated connection or the pivot connection defines a pivot axis which is at least predominantly or at least substantially parallel to the longitudinal axis of the foundation pile.
The reinforcement elements therefore remain, if required, at least substantially in a common plane perpendicular to the longitudinal extent of the foundation pile, even when they are pivoted relative to one another.
In this way, it is easily possible to place the reinforcement elements more than 180° around the foundation pile and to do this before the reinforcement elements are introduced into the seabed.
This can namely simplify the introduction of the reinforcement elements into the seabed.
If the reinforcement elements are already firmly connected to one another before they are introduced into the seabed, whether in a form-fitting, articulated and/or force-fitting manner, it is possible to avoid the connection of the reinforcement elements to one another being accidentally not as desired on introduction into the seabed or as a result of introduction into the seabed.
In order to simplify modular construction as well as the successive introduction of the reinforcement elements into the seabed, it is expedient if each of the reinforcement elements has a sleeve element of the sleeve, a collar element of the collar and at least one support element of the support.
For example, the foundation reinforcement can also be formed by identical reinforcement elements.
The use of identical parts is not only simpler, but also involves lower manufacturing costs.
In addition, assembly of the foundation reinforcement can be simplified if the sides of the sleeve elements, collar elements and/or support elements that are adjacent to one another in the circumferential direction are designed for form-fitting, articulated and/or force-fitting connection to one another.
This also leads to an overall reduction in production costs for the foundation reinforcement.
A grout connection can be provided in order to achieve reliable support of the foundation pile on the foundation reinforcement, which allows the transmission of high forces.
For this purpose, a gap can be provided between the sleeve, in particular between the sleeve elements, and the outside of the reinforcement section of the foundation pile, which gap can then be filled in with a casting compound.
What is known as a grout, which is a special concrete or cement paste or cement mortar for filling gaps, is particularly suitable for this purpose, in particular for connecting concentric steel tubes of a wind turbine that are spaced apart from one another by a gap.
Grouts with different compositions are known on the market.
Casting compounds can also be casting mortar.
A grout is, for example, a high-strength casting concrete that is known in different compositions.
Since grout connections are known in offshore wind turbines, albeit at a different location, in particular in the connection between the foundation pile and the tower of the wind turbine above water level, the present connections are also referred to as grout connections, although in principle other casting compounds can also be considered as a grout for forming the connection, for example steel fibre concrete or cement-free bentonite suspensions.
In particular, in order to obtain a radially closed gap that can be filled with a casting compound, in particular a grout, it is advisable for at least two adjacent sleeve elements of adjacent reinforcement elements to be designed to overlap in sections in the circumferential direction.
A stable and also rigid design of the foundation reinforcement can be obtained if the at least one support, in particular the at least one support element, takes the form of a rib or strut.
In this way, forces in the radial direction can also be dissipated particularly reliably, in particular when the rib or strut extends in the radial direction.
The respectively adjoining support elements of adjacent reinforcement elements can also be designed for form- fitting, articulated and/or force-fitting engagement with one another, such that the adjacent reinforcement elements can be simply connected to one another.
The form-fitting interlocking of the support elements is achieved particularly easily and reliably in that one support element has at least one hook section and that the associated support element of the adjacent reinforcement element has at least one engagement section that engages in the hook section of the adjacent support element.
Furthermore, it is expedient if the adjacent sleeve elements are arranged at a distance from one another at least in the region of at least one feed-through opening in the foundation pile.
This prevents the at least one line and/or the at least one cable from being damaged by the foundation reinforcement.
This does not mean that the adjacent sleeve elements cannot be in contact with one another in sections, nor that the adjacent sleeve elements cannot be connected to one another.
However, this should then be the case in regions other than in the region of the at least one feed-through opening.
Alternatively or additionally, a recess can also be provided in the collar at the points at which cables are routed to the foundation pile.
However, configurations are also conceivable in which the adjoining reinforcement elements, sleeve elements, collar elements and/or support elements are not connected to one another.
It is also possible to dispense with a grout and/or casting compound between the sleeve and the foundation pile in the corresponding regions of the feed-through.
For example, to prevent the seabed from being washed away in the region of the monopile foundation, the support can be designed as an annular disc that at least substantially closes the radial gap between the sleeve and the collar.
Entrainment of sediment from the inner region of the collar or the formation of a scour can be prevented in this way.
For a simple modular configuration of the foundation reinforcement, the support elements can be designed as annular disc elements of the annular disc.
For additional stiffening of the foundation reinforcement, the space between the collar and the foundation pile below the annular disc can also alternatively or additionally be filled at least substantially with a casting compound, in particular with grout.
In order to achieve simple and inexpensive filling in of free spaces with grout or another casting compound, the sleeve, in particular at least one sleeve element, and/or the support, in particular a support element, can have at least one grout port for connection to a grout line and supply of grout or another casting compound.
The position of the grout port can be selected depending on which free space is to be filled with a casting compound, in particular a grout.
In order to achieve simple and cost-effective filling in of free spaces with a casting compound, in particular a grout, the foundation pile can alternatively or additionally have a grout line on the inside.
This applies in particular when the grout line is connected to the at least one grout port.
In order to simplify the installation of the foundation reinforcement without having to completely disassemble the submarine cable, the sleeve can have an elongated hole provided in the foundation pile in overlap with the feed-through opening for feeding through a submarine cable.
The submarine cable then only needs to be separated at a connection that can already be separated in order to assembly the foundation reinforcement, for example.
After the foundation reinforcement has been assembled, the submarine cable can then be guided through the elongated hole and reconnected to the corresponding connection.
In principle, it is expedient if the elongated hole is aligned at least essentially parallel to the longitudinal axis of the foundation pile.
It is not a problem if the foundation reinforcement is introduced a little further or less deeply into the seabed because, for example, the seabed in the region of the collar is softer or harder than expected.
Alternatively or additionally, the sleeve can be recessed on the circumference in the region of the feed-through opening in the foundation pile and below.
The foundation reinforcement can then be pushed over the foundation pile if the circumferential alignment is correct relative to the foundation pile and the already laid submarine cable.
The submarine cable is then held in the corresponding recess in the sleeve without being damaged.
In principle, it can be an additional option if the sleeve is closed on the circumference above the feed-through opening in the foundation pile.
This means there is no need to fear damage to the submarine cable and the monopile foundation can be reinforced as a whole.
In addition, the collar can also be recessed on the circumference at least below the feed- through opening in the foundation pile.
The foundation reinforcement can then also be pushed over the foundation pile with the correct circumferential alignment relative to the foundation pile and the already laid submarine cable, wherein the submarine cable is then received in the corresponding recess in the collar without being damaged.
If the collar is not introduced too far into the seabed, it can be useful to stiffen the foundation reinforcement itself if the collar is closed on the circumference despite the corresponding recess, namely above it.
In order to enable the assembly of the foundation reinforcement when the submarine cable has already been assembled, but not to weaken the foundation reinforcement unnecessarily, the sleeve can have an assembly section on the circumference in a region below the feed-through opening in the foundation pile that can be adjusted from an assembly position into a reinforcement position and back, wherein, at the assembly section in the assembly position, the feed-through opening in the foundation pile is freely accessible from the seabed in a direction at least substantially parallel to the longitudinal axis of the foundation pile.
In the assembly position of the assembly section, the sleeve can therefore be pushed over the feed-through opening without the submarine cable guided through the feed-through opening being damaged.
So that the sleeve does not remain permanently weakened after the foundation reinforcement has been assembled below the feed-through opening, it may be expedient if the assembly section is connected in the reinforcement position to two sleeve elements located opposite on the circumference, in particular if the sleeve closes on the circumference between the two sleeve elements located opposite on the circumference.
The sleeve can thus be stiffened into the reinforcement position by adjusting the assembly section after the foundation reinforcement has been assembled, without this affecting the guidance of the submarine cable.
In order to enable the assembly of the foundation reinforcement when the submarine cable has already been assembled, but not to weaken the foundation reinforcement unnecessarily, alternatively or additionally the collar can have an assembly section on the circumference that can be adjusted from an assembly position into a reinforcement position and back, wherein the assembly section in the assembly position forms an opening in the collar freely accessible from the seabed in a direction at least substantially parallel to the longitudinal axis of the foundation pile.
The already laid submarine cable can then be received in this opening in the collar formed by the assembly section in the assembly position, without the submarine cable being damaged during subsequent assembly of the foundation reinforcement.
So that this opening does not lead to a sustainable and permanent weakening of the collar and thus the foundation reinforcement, the assembly section can preferably be connected to two circumferentially opposite collar elements in the reinforcement position.
As a result, if necessary, the collar is then closed on the circumference between the two circumferentially opposite collar elements, which leads to a considerable stiffening of the foundation reinforcement.
The assembly section can be arranged above the submarine cable and, in the installed state, above the seabed.
Alternatively or additionally, the assembly section of the collar can also be provided below the submarine cable and, if necessary, at least partially inserted into the seabed in the installed state.
In the latter case, the assembly section of the collar is preferably adjusted from the assembly position to the reinforcement position before the collar is introduced into the seabed.
In order to enable the adjustment of the assembly section of the sleeve and/or the collar in a structurally simple manner and to be able to bring it about easily, it is expedient if the assembly section of the sleeve and/or the assembly section of the collar is designed to be pivotable, foldable and/or collapsible for adjustment from the assembly position to the reinforcement position and back.
The assembly section can thus be handled easily.
Regardless of this, it is also preferred if the assembly section of the sleeve and/or the assembly section of the collar in the assembly position is fixed to at least one circumferentially adjacent sleeve element, a circumferentially adjacent collar element and/or a circumferentially adjacent support element.
Such a fixing leads to a sustainable and pronounced stiffening of the foundation reinforcement and thus of the monopile foundation.
It can be expedient not only from a construction point of view, but also for reasons of stiffening the foundation reinforcement, if at least one support or at least one support element is designed in such a way that it can receive the already laid submarine cable when assembling the foundation reinforcement.
This can be done by at least one support or at least one support element having a cable receptacle extending at least substantially radially to the foundation pile, in particular formed as a recess in the support or as a channel in the support or the support element, for receiving the submarine cable extending through the feed-through opening in the foundation pile.
In this case, it makes sense in terms of construction if the cable receptacle is freely accessible from the seabed in a direction at least essentially parallel to the longitudinal axis of the foundation pile.
The foundation reinforcement can then be pushed onto the foundation pile, even if the submarine cable has already been assembled.
Particularly in cases where a recess or opening is provided in the foundation reinforcement to receive or feed through the already laid submarine cable, it may be expedient to compensate for the resulting weakening of the foundation reinforcement.
This can preferably be done by providing a stiffening element connected to the at least two adjacent support elements in the circumferential direction between at least two adjacent support elements and in the radial direction between the sleeve and the collar.
This stiffening element is therefore primarily added to the stiffening of the foundation reinforcement, wherein the stiffening element can, for example, increase the region moment of inertia of the foundation reinforcement.
The use of the stiffening element can be particularly useful if the sleeve between the at least two adjacent support elements has a smaller extension, at least essentially parallel to the longitudinal axis of the foundation pile, than the adjoining regions of the sleeve.
This smaller extension can then be used to feed through the submarine cable.
The weakening of the sleeve there is then, if necessary, compensated for adjacently by the stiffening element.
It can be structurally simple and functionally expedient in connection with the stiffening element if the extension of the sleeve between the at least two adjoining support elements relative to the adjoining regions of the sleeve is in each case at least substantially parallel to the longitudinal axis of the foundation pile at least substantially smaller by an amount that at least substantially corresponds to the extension of the stiffening element at least substantially parallel to the longitudinal axis of the foundation pile.
For example, the stiffening element can have at least substantially the dimensions or the region of the part of the sleeve that has been recessed adjacent to the sleeve in order to enable the submarine cable to be fed through or received.
This ensures, for example, that the weakening of the sleeve is compensated for by the reinforcement of the foundation reinforcement by the reinforcing element.
If at least one support or at least one support element has a cable guide for guiding the submarine cable in the direction of the feed-through opening, the submarine cable can be guided via the cable guide to the feed-through opening of the foundation pile or in its vicinity.
This prevents the submarine cable from being kinked or otherwise damaged.
The submarine cable can also be laid reproducibly and protected from the effects of significant external forces.
It is particularly useful if the cable guide has a trough-like, in particular U- shaped or V-shaped, cross-section transverse to the submarine cable to be guided, in which the submarine cable can be received at least in sections.
This can be easily achieved in terms of design if the cable guide is at least essentially formed by the shoulder, i.e. for example the upper edge, of the support or the support element and two laterally adjoining flank elements.
These flank elements can then extend upwards from the shoulder of the support or support element, if necessary obliquely upwards.
In order to be able to better fill the gap between the foundation pile and the sleeve with a casting compound, such as grout, in order to be able to improve the stability of the monopile foundation installation and the dissipation of the forces, it is expedient, if necessary, if a coolant line is associated with the sleeve adjacent to the recess in the sleeve.
The coolant line is preferably designed so that seawater can be frozen out in a gap between the reinforcement section of the foundation pile and the sleeve of the foundation reinforcement and in a region adjacent to the recess, so that the ice locally seals the gap.
In a first particularly preferred embodiment of the method it is provided that, in the circumferential direction of the foundation pile, the collars of a plurality of, in particular two, three or four, reinforcing elements are at least partially introduced into the seabed, preferably via vibration, so that the reinforcing elements are then at least partially through the Insertion into the seabed, in particular one after the other, or before at least partial insertion into the seabed, positioned next to one another so that the mutually adjacent sides of the adjacent reinforcing elements, preferably by at least partial insertion into the seabed or before at least partial insertion into the seabed, are connected to one another in a form-fitting, articulated and/or force-fitting manner and that the reinforcement section of the foundation pile above the seabed is connected to the sleeve of the foundation reinforcement.
In this way, a monopile foundation can be simply and efficiently retrofitted with a foundation reinforcement whenever this is indicated for the respective reasons in the individual case.
Furthermore, it is possible to connect the sides of the sleeve elements, collar elements and/or support elements each adjacent to one another in the circumferential direction to one another, preferably through the at least partial introduction into the seabed or before the at least partial introduction into the seabed, in a form-fitting, articulated and/or force- fitting manner.
In this way, the respective reinforcing elements can be connected particularly expediently.
The at least two adjacent sleeve elements of adjacent reinforcement elements can be positioned overlapping in sections in the circumferential direction, in particular to form a closed sleeve in the radial direction.
This favours connection to the foundation pile and thus support of the foundation pile.
This allows the modular structure to be simplified, as well as the insertion of the reinforcing elements one after the other into the seabed.
If the sleeve, in particular the sleeve elements, is/are connected to the outside of the reinforcement section of the foundation pile, which is spaced apart by a gap, via a casting compound, in particular grout, introduced into the gap, a durable connection can be achieved and large forces can be dissipated.
Alternatively or additionally, adjacent sleeve elements can be arranged at a distance from one another in the region of at least one feed-through opening in the foundation pile.
This ensures that submarine cables, for example, can be fed through into or out of the foundation pile easily and without damage.
Irrespective of this, adjoining support elements of adjacent reinforcement elements can each be joined in a form-fitting manner, in particular via at least one hook section and at least one engagement section, in order to enable simple and moreover functional joining.
The space between the collar and the foundation pile below the annular disc is preferably at least substantially filled with a casting compound, in particular a grout, in order to further stiffen the foundation reinforcement and/or to enable dissipation of greater forces from the foundation pile into the seabed.
Alternatively or additionally, a casting compound, in particular a grout, can be supplied via a grout port in the sleeve, in particular in at least one sleeve element, and/or in the support, in particular in at least one support element.
In this way, the corresponding free space can be filled in very easily, reliably and quickly.
This is the case in particular when the casting compound, in particular the grout, is fed in via a grout line.
The latter can run outside the foundation pile.
However, it may be preferred for the grout line to run inside the foundation pile.
This simplifies connecting the grout line and protects it from external damage.
To simplify the creation of a monopile installation, the foundation reinforcement can be pushed onto the reinforcement section of the foundation pile and/or the foundation pile can be pushed through the foundation reinforcement. This can be done before the foundation reinforcement and foundation pile have been introduced into the seabed. In many cases, however, it will be preferred or given that the foundation reinforcement or foundation pile has already been introduced into the seabed. The foundation reinforcement can then very easily be pushed onto the reinforcement section of the foundation pile in order to introduce it into the seabed, or the foundation pile can be inserted through the foundation pile when it is inserted into the seabed. In order to reliably fill the gap between the foundation pile and the sleeve, it may be useful if a coolant is passed through at least one cooling line. If necessary, sea water can be frozen into ice, on the one hand, in a gap between the reinforcement section of the foundation pile and the sleeve of the foundation reinforcement and, on the other hand, in a region adjacent to the recess. The recess is then more or less sealed, so that the casting compound or the grout cannot escape from the recess while the casting compound or the grout has not yet hardened. For this purpose, it is useful if the at least one coolant line is assigned to a recess in the sleeve. The invention is explained in more detail below on the basis of drawings depicting merely exemplary embodiments. In the drawing:
Fig. 1 shows an offshore wind turbine with a first monopile foundation according to the invention and a first monopile foundation installation according to the invention in schematic side view,
Fig. 2 shows a detail of the offshore wind power plant in the region of the monopile foundation installation in perspective view,
Fig. 3 shows a schematic representation of the method for producing the monopile foundation and the monopile foundation installation from Fig. 1 in a schematic representation,
Fig. 4 shows a detail of the monopile foundation installation in plan view,
Fig. 5 shows the detail of the offshore wind power plant from Fig. 1 in horizontal sectional view, Figs. 6A-B show a detail of a second monopile foundation according to the invention and a second monopile foundation installation according to the invention in an assembled position and in a position during production, each in perspective view,
Fig. 7 shows a detail of a third monopile foundation according to the invention and a third monopile foundation installation according to the invention in perspective view,
Fig. 8 shows a detail of a fourth monopile foundation according to the invention and a fourth monopile foundation installation according to the invention in perspective view,
Fig. 9 shows a detail of a fifth monopile foundation according to the invention and a fifth monopile foundation installation according to the invention in a perspective view.
Fig. 10 shows a detail of a sixth monopile foundation according to the invention and a sixth monopile foundation installation according to the invention in perspective view,
Fig. 11 shows a detail of a seventh monopile foundation according to the invention and a seventh monopile foundation installation according to the invention in perspective view,
Fig. 12 shows a detail of a eighth monopile foundation according to the invention and a eighth monopile foundation installation according to the invention in perspective view,
Fig. 13 shows a detail of a ninth monopile foundation according to the invention and a ninth monopile foundation installation according to the invention in perspective view, and
Fig. 14 shows a further detail of an eighth monopile foundation according to the invention and an eighth monopile foundation installation according to the invention, each according to Fig. 12 in a perspective view.
Fig. 1 shows an offshore wind power plant W that includes a monopile foundation installation 1 with a monopile foundation 2. The monopile foundation installation 1 comprises a foundation pile 3 and a foundation reinforcement 4. Both the foundation pile 3 and the foundation reinforcement 4 are partially embedded in the seabed M. The foundation pile 3 is formed by a steel tube which is open at the bottom and which extends upwards above sea level S. The illustrated, and in this respect preferred, foundation pile 3 comprises a foundation section GA for introduction into the seabed and a reinforcement section VA for reinforcing the foundation pile 3 with the foundation reinforcement 4. The tower structure T of the wind turbine W, which carries the nacelle G and the rotor R, is placed on the upper end of the foundation pile 3. In the region of the reinforcement section VA of the foundation pile 3, a feed-through opening (not shown in detail) is provided for feeding through a submarine cable 43, which is laid outside the monopile foundation 1 on the seabed M.
In Fig. 2 the monopile foundation installation 1 is shown in detail, wherein for the sake of clarity the monopile foundation 1 is shown in such a way that the feed-through opening of the reinforcement section VA of the foundation pile 3 and the submarine cable are concealed by the foundation pile.
First, the foundation reinforcement 4 will be explained in more detail.
The foundation reinforcement 4 is provided on the outside adjacent to the foundation pile 3 and circumferentially around the foundation pile 3. The foundation pile 3 is surrounded by a sleeve 5 of the foundation reinforcement, wherein, in the illustrated, and in this respect preferred, monopile foundation installation 1, the annular gap 6 between the sleeve 5 and the foundation pile 3 is filled with a casting compound 7, in particular in the form of a grout or special concrete, to ensure a flush and firm connection of the foundation reinforcement 4 to the foundation pile 3. The sleeve 5 is connected to the collar 9 of the foundation reinforcement 4 via a support 8. The support 8 is here formed by a row of support elements 10 emerging from the sleeve 5 and pointing radially outwards in a star shape, which engage with the collar 9 with their outer ends.
In the case of the monopile foundation installation 1 shown and in this respect preferred, the collar 9 is designed as an at least substantially cylindrical steel casing, which has been driven into the seabed M with its lower end.
For greater clarity, the seabed M has been omitted from Fig.