EP2893086B1 - Offshore foundation, and production method - Google Patents

Description

The invention relates to an offshore foundation for a monopile of an offshore power plant, in particular wind or hydropower plant, for securing the monopile in and on the seabed and a manufacturing method for producing an offshore foundation.

From the prior art, various arrangements are known to secure offshore power plants on and in the seabed. Monopiles, tripods, jackets and gravity foundations are used to connect the power plant towers to the ground.

From the publication WO 2013/022338 A1 an offshore foundation for wind turbines is known, first positioned a placeholder element with a receptacle for a monopile later used on the ground, then sealed with an auxiliary element and then covered first with a fine-grained filter system and finally with a cover layer of large stones or rocks becomes. After the construction of the different rock layers lifting the occlusive auxiliary element takes place, so that the recording is released within the placeholder element and the monopile can be performed by this recording in the ground.

The subject matter described here relates to monopile arrangements, but may also be used for other energy plant installations.

A monopile construction consists of a cylindrical hollow pile, mostly of a metal, but recently also of fiber-reinforced plastics. The monopile is used in many European offshore wind farms near the coast and is previously only suitable for foundations in Water depths up to about 30 meters. For the use of more efficient offshore energy systems in deeper water depths monopile constructions are not economically suitable so far. Their use is still economical up to water depths of about 30 meters. Monopiles can be installed easily and quickly, often using heavy piling equipment for their erection. Monopile constructions can be costly against the Auskolkung secure and also offer a good collision protection. They are not used in stony seabeds so far.

In Germany, 80% of the possible locations for offshore energy plants have a water depth of 35 to 45 meters, so that the simple application of a monopile in a conventional configuration with a diameter of 6 to 7 meters is no longer economically feasible and also the stability can not be guaranteed.

The present invention has for its object to provide an offshore foundation for a monopile for an offshore power plant, which allows the use of monopile structures in larger water depths cost, at the same time provides sufficient Kolkschutz, regardless of a construction schedule for the energy systems or the provision of MonopileStrukturen and also can be produced without consuming Nachprofilierungsarbeiten.

Furthermore, it is a further object of the present invention to provide a manufacturing method for an offshore foundation, this manufacturing method satisfies the aforementioned device-related tasks cost.

These objects are achieved with an offshore foundation according to claim 1 and a manufacturing method for an offshore foundation according to claim 7.

By virtue of the fact that the offshore foundations exclusively consist of unbound broken stones piled up on the seabed a broadly graded mixture in the range of 1 mm to 200 mm rock size and the stones in the composite cone-shaped, at least frusto-conical, sedimented piled up, the stones are applied to the seabed punctually at the later location of the monopile and compacted only by its own weight, at least sedimented, a monopile can be driven from above into this foundation and subsequently introduced penetrating further into the seabed, but the introduction of the seabed is considerably lower than with previous foundations for monopiles necessary. Previous monopiles must be introduced significantly further into the seabed in order to ensure sufficient stability for later installed energy system can. Due to the artificial dumping of the seabed in the form of a truncated cone or a cone, the stability is now essentially provided by the foundation heaped up on the seabed. Here, in particular, the rock form is of crucial importance, since the unbound broken stones mesh particularly well with each other by the introduction and self-compression after application to the seabed or connect with each other, so that even strong movements and forces very well in the foundation and the Seabed can be initiated.

An according to the invention offshore foundation is erosion-proof against flow as well as filter-stable against the existing soil.

Due to the grain sizes used, however, the rock cone sedimented into a truncated cone can be pierced or pierced.

In particular, the material can be included in the static calculation, since the at least formed as a truncated cone offshore foundation absorbs a large part of the horizontal forces. Therefore, the calculation sole can be increased significantly, so that even deeper seabed can be considered as locations. In this regard, monopiles can be equally dimensioned be produced because the height compensation by the cone or the truncated cone takes place, resulting in a series production with only a few basic variants of the monopile and thus saves considerable costs in planning, production and storage.

The prestressing of the seafloor and the increased conical landfill already deepens the underlying seabed, which leads to consolidation. As a result, the static calculation basis can be significantly improved, since the dead weight of the frustoconical down-poured foundation significantly improves the seabed and the underlying layers statically.

The cone from the wide-graded mixture replaces an extra scouring protection extremely effectively.

Broken stones are made exclusively by breaking and are 100% broken core bank rock. In this case, in particular, the non-uniform grain shape is important. It is not cubic or even spherical beaten stones, but only broken stones.

A broken grain creates a maximum bond with each other, which leads to a permanent very good gearing together, so that the longevity of the offshore foundation is permanently guaranteed.

Since the mixture of unbound broken stones is particularly readily available, since all possible types of rock can be used for this purpose, this is an especially easy to manufacture offshore foundation for monopile structures. In addition, regardless of the subsequent monopile introduction the offshore foundation structure already be built up early. Deep rocks, such as granite or granodiorites, are preferably used.

The exclusively unbound broken stones are, in particular, natural stones which can be inexpensively transported by ship to the place of introduction or production and, for example, can be constructed correspondingly on the seabed by means of fall-pipe vessels.

A Kolkschutz is not necessary because the material in conical form is erosion stable at the same time. The conical shape itself offers a surprisingly simple antiskid function, so that erosion in the edge area is reduced to a minimum.

A further particular advantage is the favorable ability to be dismantled by crane or suction vessel and the complete reusability of the environmentally harmless offshore foundation material.

In the previously known foundations for offshore energy systems, a costly reworking is always necessary, which is not necessary in this case and in particular brings an advantage in consideration of the cost.

As a further advantage of the invention offshore foundation when using customary sea depths less than 30 meters, the invention leads to the fact that significantly less material must be used for the monopile, so that here an enormous savings in the production of monopile can be realized because the Monopile does not have to be driven as deep as necessary into the seabed.

Overall, therefore, an offshore foundation for monopile structures for energy systems is specified, which is essentially inexpensive to produce and in particular opens the possibility to use in simple waters over 30 meters deep simple monopile constructions for energy use.

The offshore foundation has a slope angle in the sedimented state in the range of 1: 1.5 to 1: 3, which represents a nearly ideally flown underwater body taking into account the height, stability and load characteristics.

If the unbound broken stones have a grain size of 1 to 200 mm, an optimal interlocking takes place during the introduction or the sedimentation. For this purpose, a rock mixture with optimum grain composition, according to the ideal sowing line according to or similar to the fuller parabola is applied to the seabed as an offshore foundation.

Another particular advantage is the material density of the unbound broken stones in the range of 2.3 t / m ³ to 3.8 t / m ³ , in particular 2.8 t / m ³ , as found here particularly good strength values of the foundation in test series were. For an optimal offshore foundation, the bulk density of the unbound crushed stones is in the range of 1.5 t / m ³ to 2.5 t / m ³ , in particular 1.9 t / m ³ . The unbound broken stones are erosion and / or filter stable.

When the ratio between the diameter of the monopile to be used or used and the width of the tip of the offshore foundation after sedimentation is in the range of 1: 1 to 1: 3, preferably 1: 1.5, the introduced Forces of a monopile arranged in the offshore foundation sufficiently and particularly effectively derived in the seabed.

If necessary, a supplementary scour shield may be provided in partial areas on the surface of the broken-stone offshore foundation.

• Aufschütten eines Gesteinsgemisches aus ungebundenen und gebrochenen Steinen in Form eines weit gestuften Gemisches im Bereich von 1 mm bis 200 mm Gesteinsgröße auf einem Punkt des Meeresbodens bis zur Höhe h1;
• Selbstsedimentieren des aufgeschütteten Gesteins zu einem Kegelstumpf, wenigstens einem Kegel;
• Einbringen des Monopiles direkt in und durch das Offshore-Fundament durch Einrammen, Einbohren und/oder Einrütteln, wobei der Monopile bis in den Meeresboden eingebracht wird.

The production method for an offshore foundation for and with a monopile of an offshore energy plant, in particular wind, solar or hydro power plant, for securing the monopile in and on Seabed according to one of the preceding claims, comprising the steps:

• Pouring a rock mixture of unbound and crushed stones in the form of a widely graded mixture in the range of 1 mm to 200 mm rock size on a point of the seabed up to the height h1;
• Self-sedimentation of the poured rock into a truncated cone, at least one cone;
• Introduction of the monopile directly into and through the offshore foundation by ramming, drilling and / or shaking, where the monopile is introduced into the seabed.

A conventionally produced two-layer Kolkschutz is usually not durchrammbar because the top layer consists of large rock fractions, which is why usually the first installation of a small rock as a filter layer, followed by the ramming of the monopile and only after the final coverage of the filter layer by means of a cover layer big stones. Here is clearly the high time commitment to classify as negative, since at least two times a transport ship deliver the stones to the installation site and usually with a special Einbringsystem, such as a gripper or corresponding slide systems, the top layer around the monopole and past this must be applied carefully without damaging the monopile.

The heights h1 or h2 as well as h3 and h4 of the monopile or of the offshore foundation are to be determined according to the required static calculations.

Hereinafter, an embodiment of the invention will be described in detail with reference to the accompanying drawings.

Fig. 1

eine schematische Darstellung des Ausführungsbeispiels des erfindungsgemäßen Offshore-Fundamentes.

It shows:

Fig. 1

a schematic representation of the embodiment of the invention offshore foundation.

In Fig. 1 is a schematic representation of the embodiment of the invention offshore foundation 4 shown.

The offshore foundation 4 consists of individual unbound broken natural stones of fraction 1 to 200 mm. The stones 41, which originate from surrounding as well as from distant quarries, were broken in the quarry or at a processing site and subsequently brought to the site, for example, by means of a fall-pipe ship and applied to the seabed 2.

By applying a cone-shaped landfill foundation 4 has formed the height h1, which has subsequently a time, for example, several months or even years, preferably about a year, self-compacting. A waiting period is not mandatory. During this self-compression or during the introduction, the individual fractions of the applied rock 41 interlock with one another in such a way that an almost monolithic block is created. During the sedimentation or the Aufschüttens and self-compression, the originally poured base is wider and the height h1 when introduced reduced to the height h2. This still forms a flattened upper truncated cone area. The slope ratio at the slope is about 1: 1.5 to 1: 3.

Following the sedimentation of the rock 41 to the monolithic offshore foundation 4, the monopile 1 is driven from the top into the frusto-conical offshore foundation 4 by ramming or drilling. Here, the ramming / drilling takes place into the seabed 2 into, but only a smaller penetration depth h3 in the seabed 2 is needed, as a total of the total length h4, namely h3 plus h2, the monopile 1 is anchored positively and securely, said All introduced into the monopile 1 forces are transmitted to the seabed 2. By introducing the monopile, the offshore foundation becomes wider at its tip by the shaking / piling process.

As a further advantage of the offshore foundation according to the invention when using customary sea depths of less than 30 meters, the invention results in significantly less material having to be used for the monopile 1, so that an enormous savings potential can be realized in the production of the monopile 1 here.

In this embodiment, the diameter of the monopile 1 is about 6 meters. The head region of the offshore foundation is in this case designed such that laterally about 4 meters of material around the monopile 1 are present circumferentially.

Below are some examples of the offshore foundation listed in a table: Height h1 [m] Height h2 [m] Base width Ø (slope 1: 2) [m] Amount of rock [t] 8th 4.3 32 3900 10 6.3 40 8000 12 8.3 50 15,000

Overall, it can be clearly seen from this exemplary embodiment that approximately half of the monopile 1 is arranged in the offshore foundation 4 and seabed 2, with only less than 30% of the total length of the monopile 1 being introduced into the seabed 2.

With this surprisingly simple trained offshore foundation 4 so cost deeper sea regions can be achieved with water depths between 30 and 50 meters for monopile use, as well as conventional sea depths below 30 meters, the monopile production costs are reduced by the quasi raising the seabed. Similarly, stony seabeds 2, which are suitable with a lesser useful layer for the recovery of a monopile 1 at the surface, can be used, since only one Fraction of the usually necessary length of the monopile 1 must be introduced into the seabed 2.

LIST OF REFERENCE NUMBERS

1

monopile

2

Seabed

3

water surface

4

piled foundation

41

broken stone

h1

Height of the poured foundation upon introduction of the bulk material

h2

Height of the poured and then sedimented foundation

h3

Penetration depth of monopile in the seabed

h4

Total length of monopile anchorage

Claims (7)

1. An offshore foundation (4) for a monopile (1) of an offshore energy installation, in particular a wind or water power energy installation, to secure the monopile in and to the sea bed (2) using rocks, characterized in that the offshore foundation (4) is composed solely of loose, crushed stones (41) heaped up on the sea bed (2), which stones (41) are in the form of a widely graduated mixture in the range from 1 mm to 200 mm of rock size,
   and the stones (41) collectively are arranged settled, heaped up in a cone shape, at least in the shape of a truncated cone,
   wherein the stones (41) on the sea bed (2) are applied selectively at the subsequent site of the monopile (1) and are compacted, at least settled, solely through their own weight.
2. An offshore foundation (4) according to claim 1, characterized in that the offshore foundation (4) has an angle of slope in the range from 1:1.5 to 1:3.
3. An offshore foundation (4) according to claim 1 or 2, characterized in that the material apparent density of the loose, crushed stones (41) lies in the range from 2.3 t/m³ to 3.8 t/m³ and the bulk density of the loose, crushed stones (41) lies in the range from 1.5 t/m³ to 2.5 t/m³, in particular is 1.9 t/m³.
4. An offshore foundation (4) according to any one of the preceding claims, characterized in that the loose, crushed stones (41) are stable with regard to filtration, at least stable with regard to erosion.
5. An offshore foundation (4) according to any one of the preceding claims, characterized in that the ratio between the diameter of the monopile (1) which is to be used or has been used and the width of the top of the offshore foundation (4) is in the range from 1:1 to 1:3, preferably 1:1.5.
6. An offshore foundation (4) according to any one of the preceding claims, characterized in that additionally an additional cover layer of crushed stones (41) of the particle size up to 600 mm is provided in partial regions at the surface of the offshore foundation (4).
7. A manufacturing method for an offshore foundation (4) for and with a monopile (1) of an offshore energy installation, at least a wind, solar or water power energy installation, to secure the monopile (1) in and to the sea bed (2) according to any one of the preceding claims, having the steps:

   - heaping up of a rock mixture of loose and crushed stones (41) in the form of a widely graduated mixture, in the range from 1 mm to 200 mm rock size, on a point of the sea bed (2) to the height h1;

   - self-settling of the heaped-up rocks (41) to form a truncated cone, at least a cone;

   - introduction of the monopile (1) directly into and through the offshore foundation (4) though driving in, drilling in and/or embedment by vibration,

   wherein the monopile is introduced (h3) into the sea bed (2).

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