EP2208825B1 - Method for installing an offshore foundation structure on the sea bed and offshore foundation structure - Google Patents

Description

The invention relates to a method for installing an offshore foundation structure on the seabed, which has at least three vertical support legs, wherein the support legs each have a standing in the installed state with a support leg on the seabed cladding tube, wherein the cladding tubes with their support feet on the seabed be placed and then at least partially driven into the ducts Rammpfähle be driven with piling or vibration hammers in the seabed.

The invention also relates to an offshore foundation structure having at least three vertical support legs, the support legs each having a standing with a support leg on the seabed cladding tube and an at least Having partially in the cladding tube and driven into the seabed driven pile.

It is for example off US 2,995,900 . US 3,348,382 A. or off US Pat. No. 2,940,265 A known to provide offshore foundation structures with vertical support legs. The support legs may have sheaths that are placed with a support foot on the seabed, so that the cladding tubes are located under water. To set up the structure, piles are passed through the serving as a guide, for example, arranged under water ducts after driving the ducts at the installation site and driven into the seabed. The driving in of the piles is carried out by a ram by means of piling or vibration hammers, which are attached to the piles after insertion of these into the ducts. For example, the pile hammers are raised several times and rammed for example by their own weight on a suitable ramming the piles. The piling itself is based on customary pile driving technology. The piles are thus driven successively into the seabed. The driving in by vibration ramming by means of vibration hammers is likewise known per se. In the driven state, the driven piles remain at least partially in the ducts so that they hold them. If necessary, further structures can be installed on the structure so grounded on the seabed. In addition to oil or gas drilling and production facilities, offshore wind turbines are increasingly being considered in this regard in recent years.

The known procedure is sound intensive. In particular, the sound produced during ramming under water spreads in the water with low absorption losses. This presents an undesirable effect, particularly for animals in the water near the installation site. In addition, the known procedure is time consuming. Thus, at the installation site at sea, first the ducts have to be placed under water, then the piles are inserted through the underwater ducts and then the piling or vibration hammers are installed for the ramming. Especially in offshore wind turbines, this is a problem because in a given by the weather conditions small time window a variety of offshore foundation structures for compared to oil or gas rigs smaller wind turbines to install. There is therefore little time available for the installation of a single offshore foundation structure. From JPS57193622 A, a composite pile to be buried in the ground is known, formed by connecting the ends of a tubular steel pile and a concrete pile. In the area of the frontal connection, the tubular steel pile has a circular metal end plate and the concrete pile has a metal cover. In this way damage to the composite pile should be avoided when driving the composite pile into the ground.

Based on the explained prior art, the present invention seeks to provide a method and a foundation structure of the type mentioned, in which the noise degradation during installation is reduced and the installation time is shortened.

This object is solved by the subject-matter of claims 1 and 11. Advantageous embodiments can be found in the dependent claims, the description and the figures.

For a method of the type mentioned, the invention solves the problem in that the piles are driven by protruding over the sea level ducts in the seabed. For an offshore foundation structure of the type mentioned, the invention solves the problem in accordance with the fact that the cladding protrude above the sea level in the upstanding state on the seabed.

The support legs are placed with their cladding tubes and support feet on the seabed. According to the invention, the ducts protrude beyond the sea level in this state set up on the seabed. The piles are then in the inventive method by the above sea level projecting cladding tubes driven into the seabed. This is done by means of piling hammers or vibration hammers (vibration ramming). The ramming energy generated by the Härnmern is introduced in a conventional manner via suitable Rammkonsolen in the pile to be rammed. The sea level refers to the sea level at sea level (nautical chart zero).

By the cladding tubes according to the invention protrude above the sea level, predominantly a Überwasserrammung takes place. Only at the end of the piling process may the piles with their upper side possibly fall below the sea level line. However, it is ensured by the projecting over the sea level cladding at any time, and especially when the sea level below the Rammpfahloberseite, ensures that the sound produced during the ramming arises within the cladding tube and can not enter directly into the surrounding water. The sound can spread from the cladding tube upwards into the surrounding air. Due to the poor sound transmission between the media air and water, this sound in the air, however, only significantly attenuated in the surrounding water. The sound pressure for animals living in the water is considerably reduced in this way.

The driving piles remain after driving into the seabed in a conventional manner at least over a portion of the length of the ducts in the ducts. They can remain in the cladding tubes in particular over the major part of the length. The piles thus have a much greater length than the ducts, for example, twice or three times the length.

The foundation structure according to the invention has at least three support legs. In the case of three support legs, the foundation structure may therefore be a so-called tripode. It may in particular be a double tripode, in an upper and a lower support and Spreizkonstruktion are provided for the support legs. Tripod construction allows for thinner piles that reduce the required impact energy and pile-up time.

According to one embodiment, the ramming piles can be installed on land before the maritime installation of the foundation structure, in particular on a production site of the foundation structure. In this way, the time required for installation is reduced because the driven piles at the installation no longer need to be introduced into the ducts. The pre-assembly of the driven piles takes place in this embodiment, ie before the installation of the foundation structure and even before a transport of the foundation structure on the water to the installation site.

According to one embodiment, the ramming piles are at least partially hollow in the use of Rammhämmern and have arranged in their interior inner Rammkonsole for ramming with Rammhämmern. On this Rammkonsole the rammers can be set for driving the piles. Due to the internal hammers, the ramming contact between the hammer and the driven pile takes place within the pile, which further reduces the resulting airborne sound. Furthermore, the pile hammers or vibration hammers can be preassembled in the pile piles before the casing pipes are erected. This reduces installation time on site and at sea. In practice, reductions in installation time of one-third are possible. In addition, the equally sound-intensive set-up time at the installation site at sea is eliminated. Again, the pre-assembly of piling or vibration hammers can be done before the installation of the foundation structure or even before a transport of the foundation structure on the water to the installation site.

According to a further embodiment, the driven piles can be driven into the seabed at the same time with the ramming or vibrating hammers that the sound produced during the ramming of the individual driven piles at least partially extinguishes each other. At the same time, it does not have to be called simultaneously in terms of frequency. Rather, the driven piles are hammered clocked in the same period in the seabed that interfere with the individual ramming sound waves destructively interfere with each other. The timing in detail depends in particular on the resulting sound frequencies and the geometric conditions of the foundation structure. Thus, the hammers have the same sound frequency phase-adjusted, in particular phase-shifted, meet the piles that, depending on in particular the distance of the sound sources to each other at the location of superposition of the sound waves, a phase shift of the waves of 180 ° if possible, ie destructive interference occurs. Depending on the amplitude of the sound waves, a total mutual extinction of the resulting sound waves takes place in the theoretical ideal case. In practice, a significant reduction in noise can be achieved in this way.

The cladding tubes can each be provided with a plastic casing surrounding at least part of its length around its outer surface, for example plastic half-thirds or quarter shells arranged on the outer surface of the cladding tubes. The casing can be provided at least for the duration of the pile. Such a plastic formwork further reduces the generation of sound, on the one hand by absorbing the sound waves and on the other hand by stabilizing the piles in the cladding tubes. Thus, a large part of the sound produced during the ramming by a bulbous deformation of the driven piles in the piling and a subsequent oscillatory regression of the pile form. This vibration of the pile is by the Plastic cladding also damped. As a plastic, for example, polyurethane comes into question. After completion of the ramming, the plastic casing can be removed. For this purpose, for example, the shells can be solved after completion of the pile so that they can float and be used for reuse.

At least over part of the length of the cladding according to the invention, in each case a circumferential cavity between the Rammpfählen and the cladding tubes is formed. This cavity may be substantially over the entire length of the cladding tubes, wherein only in the upper and lower region of the cladding guide elements for guiding the ramming piles are arranged in the pile. The cavity may in particular be filled with air, at least during ramming. This can be achieved by means of appropriate seals. This air filling prevents a direct transmission of sound between the driven pile and the cladding tube and thus the at least partially surrounding the cladding water. In addition, local deformations of the pile can be allowed in this way as a result of the piling operation.

The cavity may in particular be filled with a plastic foam, at least for the duration of the ramming. Such a plastic foam improves the soundproofing. It can be permanently formed, so remain after the ramming in the cavity. In this case, for example, an otherwise open top of the cladding tube may be sealed with a head cover against the surrounding water. Such a cover can for example be screwed or welded. As a foam, for example, a polyurethane foam in question. It may be, for example, a 1- or 2-component foam. Components of a 2-component foam may be: diphenylmethane-4, 4'-diisocyanate, tris (2-chloroisopropyl) phosphate, dimethyl ether and optionally propellants. Also, the cavity for the same purpose in particular at least for the duration of ramming be filled with a granulate. Granules in this context refers to any type of particulate material. Suitable granules may be, for example: plastic granules, for example polyurethane foam balls, hollow spheres, LECA, expanded clay or an easily foamable highly air-containing granules. Such granules can be easily removed after completion of the ramming. Thus, according to a further embodiment of the cavity can be filled in particular after completion of the ramming with concrete. Such a concrete or "grout" can be introduced via suitable injection tubes, for example, from the bottom into the cavity, thereby displacing, for example, a granulate contained in the cavity during ramming. This can be collected in a suitable container. The concrete leads to an additional stabilization of the piles in the cladding and thus the overall structure in the well-founded condition.

The inventive method and the foundation structure according to the invention are particularly suitable for the installation of offshore wind turbines. Accordingly, it can be provided that a wind turbine is installed on the foundation structure or is installed after completion of the ramming. Especially with wind turbines consists, as explained above, a large time pressure during installation. In particular, often a variety of systems must be installed, with the sound attenuation should be kept to a minimum. Especially with such offshore structures, the invention is advantageous.

Fig. 1

eine erfindungsgemäße Offshore-Gründungsstruktur in einer teilweise geschnittenen Seitenansicht,

Fig. 2

eine bei der Gründungsstruktur aus Fig. 1 vorgesehene Transportführung in einer Draufsicht,

Fig. 3

ein Stützbein der in Fig. 1 dargestellten Gründungsstruktur gemäß einem ersten Ausführungsbeispiel in einem Querschnitt,

Fig. 4

ein Stützbein der in Fig. 1 gezeigten Gründungsstruktur gemäß einem zweiten Ausführungsbeispiel in einem Querschnitt,

Fig. 5

ein Stützbein der in Fig. 1 gezeigten Gründungsstruktur gemäß einem dritten Ausführungsbeispiel in einem Querschnitt, und

Fig. 6

ein Stützbein der in Fig.1 gezeigten Gründungsstruktur gemäß einem vierten Ausführungsbeispiel in einem Querschnitt.

An embodiment of the invention will be explained in more detail with reference to figures. It show schematically

Fig. 1

an inventive offshore foundation structure in a partially sectioned side view,

Fig. 2

one at the founding structure Fig. 1 provided transport guide in a plan view,

Fig. 3

a support leg of in Fig. 1 illustrated foundation structure according to a first embodiment in a cross section,

Fig. 4

a support leg of in Fig. 1 shown foundation structure according to a second embodiment in a cross section,

Fig. 5

a support leg of in Fig. 1 shown foundation structure according to a third embodiment in a cross section, and

Fig. 6

a support leg of in Fig.1 shown foundation structure according to a fourth embodiment in a cross section.

Unless otherwise indicated, like reference characters designate like items throughout the figures. In Fig. 1 an offshore foundation structure 10 according to the invention is shown. In the example shown, the offshore foundation structure 10 has three vertical support legs 12. The support legs 12 each consist of a support leg 14 and also serve as a cladding tube 18 for the later to be installed and rammed piles 44 .. The support legs 14 are in a conventional manner trained as so-called mud-mats. The foundation structure 10 further has a central tube 20 which is connected to the support legs 12 via an upper support and expansion structure 22 ("upper bracing") and a lower support and expansion structure 24 ("lower bracing"). The central tube 20 has at its upper end a tower flange 26. On the tower flange 26, the tower 30 of a wind turbine shown schematically at 28 is installed in the illustrated example. The wind turbine 28 has an on the tower 30 arranged machine house 32 with a rotor 34 which carries the rotor blades, of which in Fig. 1 only one is shown at 36 Below the tower flange 26 has the Central tube 20 a secured by a railing 38 access 40 for an operator in the interior of the central tube and thus the interior of the wind turbine 28. By the central tube 20 16 extending submarine cable 42 are passed through the seabed for connection to the electrical unit of the wind turbine 28.

The foundation structure 10 is based on guided by the ducts 18 Rammpfähle 44 in the seabed. These are in a conventional manner by means of in Fig. 1 not shown piling or vibration hammers rammed through the ducts 18 into the seabed 16, as shown in Fig. 1 is shown only for the right pile pile 44. The in Fig. 1 Rammpfahl shown on the left 44, however, is shown in its position before driving into the seabed 16. In this state, the pile pile 44 projects out of the cladding tube 18. The piles are coated on their outer surface with a lubricant. They are about twice as long as the ducts 18.

At reference numeral 46, the sea level is shown at normal zero (nautical chart zero). At reference numeral 48, the sea level is shown at a so-called century wave.

To install the offshore foundation structure 10 on the seabed 16, the sheaths 18 are first connected on land via the support and expansion structure 22, 24 with the central tube 20 and provided with the support legs 14. Subsequently, the Rammpfahle 44 are also preassembled in the cladding tubes 18 on land, so that this as in the left driven pile 44 in Fig. 1 shown, protrude from the ducts 18. One in the in FIG. 2 shown star-shaped transport guide 52 of a lattice structure holds at its three outer ends 54 each have a driven pile 44 for the transport, as shown schematically in FIG Fig. 1 is shown. Via a hook 56 and an associated eyelet 58, which is arranged centrally on the transport guide 52, the structure 10 can be lifted with the pre-assembled pile piles 44 and deposited on the seabed 16. Of course, the transport guide 52 and the hook 56 are removed prior to installation of the wind turbine 28. They are in Fig. 1 shown for illustrative purposes only.

In Fig. 1 It can be seen that the cladding tubes 18 protrude in standing up on the seabed 16 state with their topsides 50 above the sea level 46 at normal zero. Now the ramming piles 44 by means of in Fig. 1 Not shown ramming or vibration hammers driven into the seabed 16, while the sound deterioration is minimized for in the surrounding the installation site water living animals, as explained above. The pile piles are thereby driven simultaneously with the piling or vibration hammers in the seabed 16, that extinguished each other at the ramming sound respectively at least partially by destructive interference.

In Fig. 3 is a cladding tube 18 of in Fig. 1 shown foundation structure with a pre-assembled pile pile 44 shown in more detail. Between the driven pile 44 and the cladding tube 18, a circumferential cavity 60 is formed substantially over the entire length of the cladding tube 18. Only in the upper and lower regions of the cladding tube 18 are annular ram guides 62 arranged to guide the driven pile 44 during ramming Fig. 3 shown embodiment, this cavity 60 is filled at least during the ramming with air, ensured by the installation of sealing lips or similar sealing elements. Fig. 3 It can also be seen that the driven pile 44 is hollow at least in its upper region and has a ramming surface 64 arranged in its interior in the illustrated embodiment Example, formed by the top of a striking ring 64 has. The impact ring 64 is supported by brackets 66 on the pile wall. Also in Fig. 3 To reduce the installation time and at the same time to avoid sound-intensive set-up time at sea, the pile hammers or 68 are already on land before a transport of the foundation structure 10 to the installation on the Water pre-assembled in the ducts. The driving of the ramming piles 44 in the seabed 16 is carried out using commercially available piling or vibration technology, wherein in the case of ramming the ramming energy is introduced via the impact rings 64 in the pile. In this way, the piles 44 are successively driven into the seabed.

In Fig. 4 is shown a further embodiment, which is largely in Fig. 3 shown embodiment corresponds. In addition to the in Fig. 3 shown embodiment is in the embodiment according to Fig. 4 over a portion of the length of the cladding tube 18, a plastic casing 70, formed by two arranged on the outer surface of the cladding plastic half-third or third-quarter shells 72, respectively. In the example shown are polyurethane half-shells 72. These shells 72 lead to a further reduction of the sound produced during the ramming. They may, for example, have a thickness of 50 mm. By a bulbous design of these shells 72, as shown schematically at reference numeral 74, the absorption of the resulting sound can be improved. The plastic shells 72 are released after completion of the ramming of the cladding tubes 18 so that they can float on their own and be reused.

In Fig. 5 a further embodiment of a support leg is shown, which is largely the in Fig. 3 corresponds to support leg shown. Unlike the in Fig. 3 shown support leg is in the embodiment according to Fig. 5 However, the cavity 60 filled with a plastic granules 76, which in the detail in Fig. 5 is shown in more detail. The granules 76 are filled into the cavity 60 prior to ramming. It may be, for example, polyurethane foam balls. After completion of the ramming is injected via suitable injection tubes 78 from the bottom into the cavity 60 concrete ("grout") in the cavity 60, wherein the granules 76 is displaced into a provided at the upper end of the cavity 60 annular receptacle 80. In this way, during the ramming or vibration process, the sound-absorbing properties of the granules can be used. After completion of the ramming, the compressed concrete improves the local stability of the foundation structure during operation.

In Fig. 6 a further embodiment of a support leg of the foundation structure 10 according to the invention is shown. Again, this support leg largely corresponds to the in Fig. 3 shown support leg. In contrast to Fig. 3 is however in the in Fig. 6 shown example, the cavity 60 filled with a pre-ramming and after ramming remaining plastic foam 82, for example, a polyurethane foam filled. Separate driving guides are not required. In order to seal the remaining after the ramming plastic foam 82 against the environment and in particular against water, the cladding tube 18 according to Fig. 6 at its top a head cover 84 which can be screwed or welded, for example, after completion of the ramming with the cladding tube 18.

With the invention, the noise degradation in the installation of offshore foundation structures can be significantly reduced while minimizing the time required to install at sea. In addition, a shortening of the installation time itself also means a reduction of Sound impairment over time. This is a not to be overlooked side-effect, if you have to consider eg the installation of 50 or more wind turbines per wind farm and an annually available installation time window.

Claims (14)

1. A method for installing an offshore foundation structure (10) on the ocean floor (16) having a least three vertical support legs (12), wherein the support legs (12), in an installed state, each have a sleeve (18) standing with a support foot (14) on the ocean floor (16), wherein the sleeves (18) with their support foot (14) are set up on the ocean floor (16), and then driven piles (44) running at least partially in the sleeves (18) are driven into the ocean floor (16) with pile or vibratory drivers (68),
   wherein the driven piles (44) are driven into the ocean floor (16) by means of the sleeves (18) extending above the sea level (46), characterized in that a peripheral cavity (60) is formed by seals between the driven piles (44) and the sleeves (18) at least over part of the length of the sleeves (18), wherein the cavity (60) is filled with air or a plastic foam or granules, at least while driving.
2. The method according to claim 1, characterized in that the driven piles (44) are installed on land before installation at sea of the foundation structure (10), especially on a production site for the foundation structure (10).
3. The method according to one of claims 1 or 2, characterized in that the driven piles (44) are designed at least partially hollow when pile drivers are used, and the pile drivers (68) for driving in the driven piles (44) are each placed on an inner driving bracket (64) arranged in the interior of the driven piles (44).
4. The method according to one of the prior claims, characterized in that the pile or vibratory driver (68) is pre-mounted in the driven piles (44) before setting up the sleeves (18).
5. The method according to one of the prior claims, characterized in that the driven piles (44) are driven simultaneously into the ocean floor (16) with the pile or vibratory drivers (68) such that the sound arising while driving the individual driven piles (44) is at least partially mutually extinguished.
6. The method according to one of the prior claims, characterized in that the sleeves (18), at least for the duration of driving, are each provided with a plastic shell (72) surrounding their outer surface over at least part of a length, in particular plastic half, third or quarter shells (72) arranged on the outer surface of the sleeves (18).
7. The method according to claim 6, characterized in that the plastic shell (72) is removed after the completion of driving.
8. The method according to one of the prior claims, characterized in that the granules (76) are removed after the conclusion of driving.
9. The method according to one of the prior claims, characterized in that the cavity (60) is filled with concrete after the conclusion of driving.
10. The method according to one of the prior claims, characterized in that a wind power plant (28) is installed on the foundation structure (10) after the conclusion of driving.
11. An offshore foundation structure having at least three vertical support legs (12), wherein the support legs (12) each have a sleeve (18) standing with a support foot (14) on the ocean floor (16) and a driven pile (44) running at least partially in the sleeve (18) and driven into the ocean floor (16),
    wherein the driven piles (18) extend above sea level (46) in a state standing on the ocean floor (16), characterized in that a peripheral cavity (60) is formed by seals between the driven piles (44) and the sleeves (18) at least over part of the length of the sleeves (18), wherein the cavity (60) is filled with air or a plastic foam or granules.
12. The foundation structure according to claim 11, characterized in that the driven piles (44) are designed at least partially hollow when pile drivers are used, and possess an inner driving bracket (64) arranged in their interior for driving with pile drivers (68).
13. The foundation structure according to one of claims 11 or 12, characterized in that the sleeves (18) are each provided with a plastic shell (72) surrounding their outer surface over at least part of their length, in particular plastic half, third or quarter shells (72) arranged on the outer surface of the sleeves (18).
14. The foundation structure according to one of claims 11 to 13, characterised in that a wind power plant (28) is installed on the foundation structure (10).

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