WO2004020745A1

WO2004020745A1 - Foundation for water structures

Info

Publication number: WO2004020745A1
Application number: PCT/DE2003/002139
Authority: WO
Inventors: Helmut Schwarz; Klaus Dietz
Original assignee: Stump Spezialtiefbau Gmbh
Priority date: 2002-08-22
Filing date: 2003-06-26
Publication date: 2004-03-11
Also published as: DE10239278A1; DE10239278B4; EP1530662A1; AU2003257378A1; PL374482A1

Abstract

The invention relates to a method for the production of a foundation for water structures, especially offshore foundation structures for a wind farm. Said method comprises the following steps: lowering at least one pre-made caisson onto the foundation of the water, said at least one caisson comprising a vertically extending shank which is provided with a channel, or one such shank is produced after or during the lowering onto to the at least one caisson; drilling an anchor hole through the channel of the shank and the caisson in the foundation; constructing at least one anchor traction member in the foundation, the caisson and the channel of the shank; prestressing the at least one anchor traction member in relation to an abutment in or on the end of the shank. The invention also relates to a platform comprising said produced foundation elements.

Description

Foundation for hydraulic structures

The invention relates to a method for producing a foundation for hydraulic structures, in particular an offshore foundation for a wind turbine, and a foundation produced by the method.

Various methods are known for the foundation of hydraulic structures, such as lighthouses, boat docks and coastal protection systems or the like.

For example, a complete foundation element can be prefabricated and lowered to the bottom of the water using a transport and lifting ship and assembled there. For anchoring wind turbines, it is known to lower a steel tube with a corresponding diameter and length vertically onto the ground and to ram into the ground by a sufficient length. The tower for the wind turbine can then be mounted on the end reaching above the water level.

It is also known to prefabricate complete drilling rigs, for example for oil exploration and production, to convey them to the point of use in a floating manner, where appropriate to tilt and lower them into the vertical position and to anchor them on the ground.

However, these processes, in which complete foundation elements or hydraulic structures, including their foundation elements, are prefabricated and lowered and anchored on site, involve considerable effort, in particular in connection with the transport of the prefabricated foundation elements or hydraulic structures.

In connection with the installation of wind power plants in the offshore area, there are extreme requirements for suitable foundations. There must be procedures be developed, which make it possible to create a safe, permanent foundation with reasonable economic expenditure and controlled export security in a water depth of more than 40-60 meters. A permanent platform with appropriate dimensions must be manufactured in order to be able to accommodate a wind turbine of the order of 2 MW and more with a mast height of about 100 meters and more. As a result of the wind pressure on the wind turbine, there are extreme demands on the stability of the foundation. In particular, the foundation, which runs essentially vertically, must be able to absorb high transverse forces and dynamic loads.

The invention is therefore based on the object of creating a method for producing a foundation for hydraulic structures, in particular offshore foundation for a wind turbine, with which such a foundation can be produced with reasonable economic outlay and sufficient stability. Furthermore, the invention is based on the object of creating a platform founded in a body of water which can be produced with economically justifiable outlay and which has a high degree of stability.

The invention solves this problem with the features of claims 1 and 18, respectively.

The invention is based on the knowledge that a foundation for a hydraulic structure can also be produced in great water depths with reasonable effort and high stability if a caisson with a vertically extending shaft is lowered to the bottom of the water and there by means of an anchor partially received in the shaft is biased. The foundation element is anchored by drilling an anchor hole through a channel provided in the shaft, this channel and the interior of the caisson serving as an empty hole.

After the anchor hole has been drilled through the shaft in the subsurface, the anchor can be installed in the usual way. By biasing the at least an anchor tension member opposite an abutment in or at the upper end of the shaft, the foundation element is securely anchored and at the same time receives a stability through which high transverse forces can also be absorbed. In addition, settlement processes of the foundation element generated by the tensioning of the anchor can be waited for and only then can the hydraulic engineering structure to be founded be placed on the foundation element or produced on it.

Furthermore, it is possible to preload the anchor not only to the working load, but to multiple, for example 1.5 times, the working load during the AI test. This not only improves the structural suitability of the

Established proven proof. Rather, any deformations caused by slippage or initial settling are safely anticipated in a short time.

According to the preferred embodiment of the invention, the length of the shaft is dimensioned such that its upper end extends to above the surface of the water even after the caisson or the entire foundation element has been lowered onto the subsoil of the water. This has the advantage that the anchor hole can be drilled from the water surface.

Instead of a complete prefabrication to reduce the transport effort, the shaft can have a tubular inner shaft element which is connected at its lower end to the caisson. The caisson has a breakthrough in continuation of the interior of the tubular inner shaft element. The tubular inner shaft element is preferably mounted in the form of shots when the caisson is lowered. The first “shot” of the inner shaft element can be formed in one piece with the caisson. The connection of the shots to one another can take place during the lowering, for example by welding or by means of releasable connecting means. The inner shaft element or the wefts can be designed as a steel tube or corresponding tube sections.

The inner shaft preferably has a diameter such that it can serve as a man pipe and / or supply pipe for the further assembly of the foundation element. For example, it is possible to supply compressed air via the inner shaft element, with the fitters having access to the caisson acting as a diving bell via the inner shaft element. For this purpose, a compressed air lock can be provided at the upper end of the inner shaft element. This enables the in-situ assessment of the subsoil and the processing of the subsoil of the water to produce a foundation horizon that is in accordance with the result of the assessment in a simple manner. For example, a layer of silt and a layer of sand below the caisson can be removed and the caisson can be lowered onto a rock layer below. If necessary, the layer serving as the foundation horizon can be injected by contact with a hardening building material or by introducing

Soil nails are stabilized.

Advantageously, prefabricated annular outer shaft elements are placed on the inner shaft element, preferably before the anchor hole is sunk into the subsurface through the channel of the shaft. The inside diameter of the

Outer shaft elements, which are preferably made of concrete, are preferably dimensioned such that the inner shaft element has a force-centering effect. The inner diameter of the outer shaft elements can also be made significantly larger than the outer diameter of the inner shaft element in order to make it easier to slide on the outer shaft elements. In this case, forced centering can be provided by providing guide and centering aids on the outer wall of the inner shaft element and / or on the inner wall of the outer shaft elements.

If the inner shaft element (preferably during the lowering of the shaft and the caissons) is mounted in the form of shots, then each shot can be made in front of the Lowering the shot in question (or the entire base element previously produced) into the water, one or more prefabricated outer shaft elements are placed. The outer shaft elements can be connected in the axial direction, for example by means of a positive fit on the joints and / or special plug-in connections and / or concrete composite.

The outer shaft elements serve to further stabilize the shaft or form the outer wall of the shaft when the inner shaft element is later removed again. The outer shaft elements are preferably prestressed so that the finished shaft can also absorb high tensile or bending tensile and / or transverse forces. The prestressing is preferably carried out using prestressing elements which are arranged on the inner wall of the outer shank elements or within the shank wall itself.

To further stiffen the shaft, the free space between the inner walls of the outer shaft elements and the outer wall of the inner shaft element can be filled with hardenable building material, for example concrete.

According to one embodiment of the invention, the caissons, preferably the caissons and the inner shaft element, can be filled with a hardenable building material, preferably concrete, while leaving out a channel. This results in a stabilization of the inner shaft element or the entire shaft. The channel has a diameter such that it is possible to produce a borehole in the subsurface through the channel.

In another embodiment, after the shaft has been built up by the outer shaft elements, preferably after the individual outer shaft elements have been braced and the base has been worked on, the inner shaft element can be removed again. For this purpose, as already indicated above, this can be composed of shots with detachable connections. Then the caissons, preferably the caissons and the inner shaft element, again with a hardening building material, preferably concrete, being filled in, leaving the channel empty.

The channel can be produced by means of a tubular element, for example a steel or plastic tube, which is introduced into the area of the shaft and the caisson, which is filled with the hardening building material. The annular space surrounding the tubular element is then filled with the hardening building material. This can be done by using the contractor procedure. The concrete is here by means of a feed line in the lower region of the foundation element, i. H. inserted in the lower area of the caisson and pushes the water or residual water in it upwards.

A work platform can be placed on the upper end of the shaft to produce the anchor. This enables the appropriate equipment, in particular a drilling platform, to be picked up in a simple manner.

The work platform can preferably be attached to the upper end of the shaft so that the upper end of the shaft is freely accessible. This way you can access the top

At the end of the shaft, a head plate is placed on the shaft, which serves as an abutment for prestressing the armature or the at least one tension member of the armature.

Of course, however, an abutment can also be provided in the uppermost region of the shaft, against which the armature can be prestressed.

According to the invention, it proves advantageous to have a support for a hydraulic structure

To use platform, which is anchored to the water bottom by means of three such foundation elements. Such a tripod creates an optimal compromise between the effort involved in the manufacture of such a platform and stability. The platform itself can either be prefabricated and connected to the green by means of connecting structures on the underside of the platform. application elements that ensure a positive fit. Of course, however, the platform can also be manufactured in the usual way on site and connected to the foundation elements, for example by concreting using appropriate formwork, if appropriate using suitable prefabricated parts.

Further embodiments of the invention result from the subclaims.

The invention is explained in more detail below on the basis of an exemplary embodiment shown in the drawing. The drawing shows:

Figure 1 is a schematic sectional view through a foundation element which is assembled and lowered in sections;

Figure 2 is a schematic sectional view of a lowered foundation element in the phase of processing the foundation horizon.

3 shows a section along the line A-A in Fig. 2;

Figure 4 is a schematic sectional view of the fully assembled foundation element in the phase of drilling the anchor hole.

Fig. 5 is a section along the line B-B in Fig. 4;

Fig. 6 is a schematic sectional view of the foundation element in the phase of anchor installation;

Fig. 7 is a section along the line C-C in Fig. 6;

Fig. 8 is a schematic partial sectional view of the finished hydraulic structure; Fig. 9 is a sectional view taken along the line DD in Fig. 8 and

Fig. 10 is a schematic partial sectional view of a further embodiment of a finished hydraulic structure.

Fig. 1 shows schematically in section or in side view a jack 1, with which a foundation element 3 for a hydraulic structure 5 (Figures 8 and 9) can be manufactured or assembled. The foundation element 3 comprises a caisson 7, which can have a pot-shaped structure, for example. The underside of the cylindrical wall can be designed in a cutting-like manner in order to allow the caisson to easily penetrate into a soft surface 9 of the water. As shown in FIG. 1, the subsoil can consist of a rocky subsoil 9a, the upper edge of which forms the foundation horizon for the foundation element 3. A sandy layer 9b and above it a silt layer 9c can be present on the rocky ground 9a.

The jack-up platform can be temporarily anchored to the subsurface by means of several stilts 11 and projects above the water level W.

The lifting island 1 has a crane device 13 with a mobile crane truck 15 on which a lifting plate 17 which can be raised and lowered vertically is arranged. By means of the lifting plate 17, mounting parts (not shown) mounted on the lifting island 1 for producing the foundation element can be moved from a storage position into the mounting position shown in FIG. 1. In addition, the lifting plate 17 is used for floating mounting and for lowering the part of the foundation element 3 that has already been assembled.

As shown in FIG. 1, the foundation element 3 can be composed of individual wefts for an inner shaft element 19 and an outer shaft element 21. Fig. 1 shows that the caisson 7 has an opening in its upper, horizontally running wall for receiving a first shot of the inner shaft element 19. This first part of the inner shaft element 19 can also be preassembled due to the required sealing between the inner shaft element and the caisson. The same applies to the first shot of the outer shaft element 21, which can also be formed in one piece with the caisson 7.

On the caisson 3 and the first shots of the inner shaft element 19 and the outer shaft element 21, in the assembly phase shown in FIG. 1, a further shot was placed in each case. Joining the shots for the inner shaft element

19 can be made by means of detachable connections, which, however, must have sufficient tightness in order to be able to apply compressed air to the inner shaft element later. The shots of the outer shaft element 21 can be assembled by means of a concrete composite and additionally connected by means of corresponding prestressing elements 23. In the embodiment of the method for assembling the foundation element 3 shown in FIG. 1, the prestressing elements 23 simultaneously serve for the floating mounting of the respectively prefabricated part of the foundation element 3 on the lifting plate 17 of the crane device 13.

The lifting island 1 also has a clamping device 25, with which the uppermost shot of the foundation element 3 which has been preassembled until then can be held in a clamping manner on the lifting island 1. In the clamped phase, the lifting plate 17 can be detached from the foundation element 3 and a new shot can be put on for the inner shaft element 19 or the outer shaft element 21. In this case, the weft for the inner shaft element 19 is preferably first placed and then the additional weft for the outer shaft element 21 is placed. Each outer shaft element 21 can have radially inwardly extending projections 27 in the region of the upper end, which act as abutments for tensioning serve the biasing elements 23. In any case, the uppermost shot for the outer shaft element 21 should have such projections 27 in order to ensure a continuous bracing in the final state. to enable all shots for the outer shaft element 21. The lower abutment for the prestressing elements 23 is formed by the horizontally running wall of the caisson 7, as can be seen in FIG. 1.

For the placement of the shots for the outer shaft element 21, guide and centering projections 29 extending radially outward can be formed on the outer wall of the shots for the inner shaft element 19. The upper edges of the guide and centering projections 29 are designed to run obliquely downwards, so that when the first shot is placed for the outer shaft element 21, centering takes place first and then guidance is carried out over the vertical regions of the guide and centering projections 29.

In the upper left section of FIG. 2 it is shown schematically that after the foundation element 3, which has been prefabricated up to this phase, has been completely lowered onto the ground, an airlock 31 can be connected to the upper end of the inner shaft element 19. In this way, it is possible to apply compressed air to the entire interior of the inner shaft element 19 and the caisson 7 in such a way that all the water is pressed out of this interior. In this way it is possible to let assembly personnel descend via the airlock 31 via the interior of the inner shaft element 19 into the interior of the caisson 7.

In this way, an in-situ assessment of the subsoil can be carried out and, at the same time, loose or soft soil material in the interior of the caisson is removed by means of a flushing pipe and a pump and pumped to the surface.

If the caisson then sits on the final foundation horizon, for example on the rocky subsoil 9a shown in FIG. 1, this can be examined by the ground staff for its nature and load-bearing capacity. If the floor does not meet the requirements for the load-bearing capacity, appropriate processing can be carried out, as shown in FIG. 2. Here, a device for the manufacture of ground seams was placed over the inner shaft element (still pressurized with compressed air). gel 33 brought into the interior of the caisson 7. The pegs can be introduced, for example, along an imaginary circle at equidistant intervals, as shown in FIG. 3.

FIG. 2 shows a further possibility for producing the foundation element, wherein a pontoon 35 is used which can carry a crane device 13 'floating on the water surface. Of course, the pontoon can also be designed as a stilt pontoon. With such stilts pontons can be installed up to a water depth of approx. 30 meters.

Fig. 4 shows an assembly phase in which the foundation element 3 has already been manufactured except for its anchoring in the underground. For this purpose, after removing the airlock 31, starting from the assembly phase shown in FIG. 2, the inner shaft element 19 was first removed. This can be done by loosening the lower end of the inner shaft element 19 at the point of connection with the caisson and dismounting and pulling upwards in shots.

If the lowermost “shot” of the inner shaft element is connected in one piece or not detachably to the caisson 7, pulling out and dismantling of the inner shaft element 19 after releasing the shot of the

Inner shaft element 19 take place.

By disassembling the inner shaft element, it can be reused, as a result of which the foundation element 3 can be produced more cost-effectively.

After dismantling the inner shaft element 19, a shuttering tube 35 was introduced into the inner space of the outer shaft element 21. The shutter pipe 35 can be made of plastic, for example. The shuttering pipe 35 extends to the foundation horizon. The cavity surrounding the shuttering tube 35 within the outer shaft element 21 or the caisson 7 was then filled with a hardening building material 37, for example concrete. After the building material 37 had hardened, the tensioning elements 23 were prestressed with respect to the top of the hardened building material 37. The tensioning elements 23 can be designed in the usual way, for example as

Prestressing strands that run in plastic pipes that are filled with corrosion protection.

After the annular space or the interior of the outer shaft element 21 has been filled with the hardening building material 37, the foundation element 3 is already adequately connected to the foundation horizon. In this state, an assembly platform or work platform 39 can be placed on the foundation element. This situation is shown in FIG. 4 based on the finished building to be produced in FIGS. 8 and 9, in which a tripod consists of three foundation elements 3 and a platform 41 placed thereon.

After the work platform 39 has been set up, an anchor hole 45 can be drilled into the subsurface below the foundation horizon through the channel within the shutdown tube 35 by means of a drilling device 43 located on the platform. The channel within the foundation element 3 serves as an empty hole.

After the anchor hole has been made, the anchor can also be installed, likewise from the work platform 39, using an appropriate device, for example a crane. For this purpose, as shown in FIG. 6, the tension element can be pulled off a drum with a correspondingly large radius. The tension element 47 can be a steel anchor strand, for example. This is in the borehole 45th

(Fig. 4) introduced and anchored in this by pressing in the usual way. The cavity within the shuttering tube 35 above the foundation horizon can be filled with corrosion protection, for example cement suspension. After mounting the anchor, the working platform 39 can be removed and the final platform 41 can be placed on the foundation elements 3, as shown in FIGS. 8 and 9. The platform 41 can either be placed on the tripod of the foundation elements 3 as a prefabricated component, for example in a form-fitting manner, or else can be produced in a conventional manner, if appropriate using prefabricated components, on the upper ends of the foundation elements 3.

As shown in FIG. 8, the tensioning of the tension elements 47 of the anchors can take place at the upper end relative to the platform 41 as an abutment. The actual hydraulic structure, for example the tower 49 of a wind turbine, can be mounted on the platform 41.

In the further embodiment of a hydraulic structure in the form of a wind power plant shown in FIG. 10, the tower 49 of the wind power plant is mounted on a platform which is analogous to that by means of foundation elements 3 in the form of a tripod

Figures 8 and 9 is anchored to the ground. In contrast to the embodiment described in FIGS. 1 to 9, the platform 41 is however not above the water level W, but rather just above the subsurface in the water. However, the foundation elements can largely be produced as described above. For example, a pressure lock can also be used under water during the manufacture or assembly of the foundation elements 3. The platform 41 is preferably largely prefabricated in order to avoid the more complex production under water.

This embodiment has the advantage of significantly shorter foundation elements, and the anchors can be correspondingly shorter. Due to their lower height or length, the foundation elements can also be largely prefabricated without the problem of transporting the foundation elements to the installation site. For example, the foundation elements can be prefabricated except for the filling with the hardening building material 37, possibly together with the inner shaft element 19. If the subsoil is not processed from the caisson, the entire foundation element can also be prefabricated, apart from the installation of the anchor. In this case, only the caisson or part of it cannot yet be filled with hardenable building material. After the foundation element has been placed on the prepared foundation horizon, this part can be filled with hardenable building material via the channel or the shuttering tube 35, and the connection to the foundation horizon can thus be established. Prefabrication and assembly of an entire tripod with platform is also possible in this way.

The method according to the invention for producing a foundation element enables the simple and inexpensive construction or assembly of a foundation element even in great water depths, while at the same time ensuring sufficient stability for absorbing high transverse forces. The invention is not limited to the exemplary embodiments presented above. It is of course readily possible for a person skilled in the art to create further embodiments which have other combinations of features which have been described above in connection with the two embodiments shown in the drawing.

Claims

claims

1. A method for producing a foundation for hydraulic structures, in particular an offshore foundation for a wind turbine, which comprises the following steps:

a) lowering at least one prefabricated caisson (7) onto the subsoil of the water;

b) wherein the at least one caisson (7) has a vertically extending shaft (21, 35, 37) with a channel, or such a shaft is produced on the at least one caisson after lowering or during lowering;

c) drilling an anchor hole (45) through the channel of the shaft (21, 35, 37) and the caisson (7) into the ground (9a);

d) Installation of at least one anchor tension member (47) in the subsurface (9a)

Caissons (7) and the channel of the shaft (21, 35, 37);

e) preloading the at least one anchor pulling member (45) with respect to an abutment in or at the upper end of the shaft (21, 35, 37) or a component mounted on the shaft.

2. The method according to claim 1, characterized in that the length of the shaft (21, 35, 37) is dimensioned such that its upper end extends beyond the water surface.

3. The method according to claim 1 or 2, characterized in that the shaft (21, 35, 37) comprises a tubular inner shaft element (19), which is preferably mounted in the form of wefts when lowering the caisson (7).

4. The method according to claim 3, characterized in that the inner shaft element (19) has such a diameter that it can serve as a man pipe and / or supply pipe.

5. The method according to claim 4, characterized in that compressed air is fed to the caisson (7) after lowering via the inner shaft element (19), so that the caisson can be used as a diving bell for processing the subsurface (9) for the production of a foundation due to start-up can.

6. The method according to any one of claims 3 to 5, characterized in that an outer shaft element is placed on the inner shaft element (19), which preferably consists of prefabricated, annular shots.

7. The method according to claim 6, characterized in that the inner diameter of the outer shaft element (21) is dimensioned such that the inner shaft element (21) acts positively centering, or that guide and centering aids are provided on the outer wall of the inner shaft element or the inner wall of the outer shaft element.

8. The method according to any one of claims 6 or 7, characterized in that the inner shaft element (19) is mounted during the lowering in the form of shots and one or more prefabricated shots of the outer shaft element (21) are placed on each shot before lowering the relevant shot ,

9. The method according to any one of claims 6 to 8, characterized in that the outer shaft element (21) or the shots of the outer shaft element are biased, preferably using biasing elements (23) which are provided on the inner wall of the outer shaft element (21).

10. The method according to any one of claims 6 to 9, characterized in that the free space between the inner walls of the outer shaft element (21) and the outer wall of the inner shaft element (19) is filled with hardenable building material.

11. The method claim 10, characterized in that the caissons (7), preferably the caissons and the inner shaft element (19), is filled with a hardening building material (37), preferably concrete, while leaving out the channel.

12. The method according to any one of claims 6 to 9, characterized in that the

Inner shaft element (19) is removed after mounting the outer shaft element (21) and that the caisson (7), preferably the caisson and the outer shaft element, is filled with a hardening building material (37), preferably concrete, while leaving out the channel.

13. The method according to claim 11 or 12, characterized in that the channel is produced by means of a tubular element (35) which is introduced in the region of the shaft and the caisson (7), the annular space surrounding the tubular element (35) with the hardening building material (37) is filled.

14. The method according to any one of the preceding claims, characterized in that a working platform (39) is placed on the shaft (21, 35, 37) for producing the anchor.

15. The method according to any one of the preceding claims, characterized in that a head plate is placed on the shaft (21, 35, 37) as an abutment for prestressing the armature or that the abutment is formed by the hardening building material (37) with which the shaft was filled while leaving the channel empty.

16. The method according to any one of the preceding claims, characterized in that the anchor is biased to the required working load.

17. The method according to any one of the preceding claims, characterized in that the anchor is biased for testing or settlement purposes to a multiple of the required working load, preferably 1.5 times the working load.

18. Platform with foundation elements for anchoring the platform in a body of water, which are produced by the method according to one of the preceding claims, characterized in that at least three foundation elements (3) produced by the method according to one of claims 1 to 17 are provided.

19. Platform according to claim 18, characterized in that the platform (41) is placed on the foundation elements (3) by means of a positive connection.