EP2796620B1 - Method for constructing a foundation pile for offshore constructions and foundation pile for offshore structures - Google Patents

Description

The invention relates to a method for producing a foundation pile for offshore structures. The invention further relates to a foundation pile for offshore structures and an offshore structure with a pile foundation.

Offshore structures in the context of the present invention are, for example, wind turbines, substations or drilling or production platforms.

For certain foundation types for offshore structures, in particular for offshore wind turbines, a pile foundation in the seabed is required. Common foundation types are for example so-called monopiles, jackets, tripods or tripiles. To anchor these foundations in the seabed, one or more steel piles are first driven into the seabed. For example, a steel grid structure / steel tube structure is placed on the steel piles in the case of a jacket foundation, which receives a so-called "transition piece" above the sea level. The transition piece then takes on the actual structure, for example in the form of a steel tower. The tower receives at its uppermost end the wind power generator with a rotor.

The ramming of foundation piles, also referred to as "piles", is associated with noise emissions, which are undesirable in particular because they cause damage and behavioral disturbances of marine mammals. It is therefore known and sometimes required to carry out deterrent measures and / or noise abatement measures before carrying out pile driving to ensure that no marine mammals are in the vicinity of the pile work and / or that the sound is reduced to the permitted limit.

Since the depth of penetration of the rammed steel piles and the progress of such pile work depends on the strength of the seabed, this is Setting steel piles suffers from the disadvantage that the piles of a foundation placed on several piles are not always anchored with the same depth of penetration in the seabed.

Depending on the nature of the seabed, the piles must be driven with considerable depth into the seabed, as the stability of the piles is only ensured if the piles have been driven into the ground to a sustainable soil horizon. Under certain circumstances, the actual load of the piles may be higher than the assumed load bearing requirements, which may ultimately result in the failure of a foundation pile. Under certain circumstances, the load and material fatigue caused by the piling process can exceed the predicted and calculated amount, so that the pile must either be completely abandoned or has a reduced life expectancy. The danger of a local structural failure, for example due to dents, increases with greater depth of foundation.

Connecting the underwater constructions of the foundation to the foundation piles requires potting the compound with water curable potting compounds or other expensive bonding techniques.

The piles have to be set at a specified distance, which is ensured by means of the template in the so-called "prepiling". This presupposes that the ground condition is such that all piles to be set can be driven to the given soil horizon. There are no variations with regard to the distance or the place for setting the piles.

When placing larger piles, undersea currents can lead to the seabed bottoming out in the area of the piles. In that case, further measures must be taken to prevent the bottom of the sea from being cleared. The WO 2011/147476 A1 describes a method for producing a foundation pile for offshore structures.

The invention is therefore based on the object to provide a particularly simple method for producing a foundation pile for offshore structures, which in particular is not subject to the aforementioned limitations.

The object is achieved by a method for producing a foundation pile for offshore structures according to claim 1.

As a shot channel in the context of the present invention, the displacement channel generated by the fall anchor when immersed in the sediment of the seabed is called.

The invention is based on the idea of using at least one anchor point in the seabed by means of a drop anchor and at least one anchored to the anchor anchor anchor at the anchorage on which the anchorage trunk is posted.

The fall anchor is dimensioned, for example, in terms of its mass and in terms of its geometry so that it penetrates due to its kinetic energy in free fall to a predetermined depth in the seabed. This takes in the case of this battered anchor trunk. One or more potting ground lines can be fastened to the anchor line, which are also carried along by the drop anchor. By means of this potting ground line, a curable potting compound, for example a concrete that hardens under water, is then injected under pressure into the firing channel Pressed, the anchor line at the same time serves to reinforce the Vergussmassesäule thus prepared in situ.

As a fall anchor in the context of the present invention, for example, a fall anchor is provided which has a torpedo-shaped base body with a Eindringpitze and the end is provided with a plurality of torpedo wings for the purpose of stabilization.

The torpedo body may for example be hollow and comprise one or more ballast chambers that can be filled with a ballast.

The method has in particular the advantage over conventional pile foundations that a bracing of the structure to be paid to one or more anchor lugs can be done, which naturally leaves a certain amount of space in the placement of the offshore structure, so that the setting of the foundation piles not by a template or the underwater structure of the structure is given.

In addition, the setting of piles by means of piling devices is eliminated. The process of setting the fall arrester is unique, whereas ramming piles is associated with a recurring regularly frequent sound entry into the marine environment.

As a tension element in the context of the present invention, an anchor line or an anchor chain or an anchor cable is provided.

Of course, a plurality of tension elements / anchor cables, or anchor cables, or anchor chains can be attached to a fall anchor, although the following is a tension element in each case.

In any case, a tension element in the sense of the invention is a flexible tension element which can transmit only tensile forces, but not compressive forces.

In an advantageous variant of the method according to the invention it is provided that the potting compound is introduced over at least a partial length of the tension element in the firing channel, wherein the tension element remains in the cured potting compound. The tension element serves on the one hand the reinforcement of the potting compound, on the other hand, the bracing of the offshore structure to be built. Thus, the depth to be reached by the fall anchor depth is reduced because the required for bracing humor of the main structure of the tension element jacket friction is reduced and is supplied by the Vergussmassenkörper.

Conveniently, the tension member is provided at the side remote from the anchor anchor side with at least one float, which is arranged at a predetermined distance from the fall anchor, the distance chosen according to the planned depth of penetration of the drop anchor into the seabed and the height of the sea level above the seabed is such that the tension member and the potting grounding line connected thereto can float so that they can be captured by a supply ship.

The fall anchor is expediently provided with ballast before being dropped off, wherein the ballast mass is chosen such that the fall anchor penetrates into the seabed up to a load-bearing soil horizon.

In a particularly advantageous variant of the method, it is provided that the drop anchor is suspended from a discharge line and the dropping takes place by actuating a triggering mechanism on the discharge line. The fall anchor is struck in this case both on the discharge line as well as on one or more tension members.

In a favorable variant of the method according to the invention it can be provided that the fall anchor is introduced through a protective tube or a sheet pile wall into the seabed, wherein the protective tube or the sheet pile enclosure were previously set.

In order to facilitate penetration of the fall anchor into the seabed, provision may be made for the seabed to be fluidized beneath the protective tube or within the sheet pile enclosure prior to the fall anchor being removed by injection of compressed air or water.

Alternatively, it can be provided, for example, when using a protective tube, that the protective tube is pumped empty before dropping the drop anchor, so that the kinetic energy with which the drop anchor can penetrate into the seabed, significantly increased.

Alternatively, the protective tube, which may extend, for example, beyond the sea level, be pumped with a liquid, so that at the pipe base through the liquid column, an increased hydrostatic pressure is built up, which facilitates the penetration of the drop anchor into the seabed. The liquid column can be adjusted accordingly, for example, with regard to its specific weight. For example, can be used as a liquid barium spar solution application.

The protective tube can, for example, be flushed into the seabed to a certain depth before the drop anchor is dropped off.

The potting ground line can be provided, for example, with a plurality of outlet openings or outlet nozzles provided at a distance from one another in the longitudinal direction, so that the potting compound can penetrate uniformly over the height of the tension element into the firing channel.

It is also possible that the potting grounding line is pulled during potting. Then it is not absolutely necessary to provide several outlet openings for the potting compound. However, a pulling of the potting ground line can also be provided if a potting ground line with a plurality of distributed over the height and / or circumference arranged outlet openings for the potting compound application.

The potting grounding line can be lost at least over a subsection extending in the weft channel, i. remain in the firing channel via this section.

The object underlying the invention is further achieved by a foundation pile for offshore structures, comprising a drop anchor, at least one cast on this anchor line as tension element and a cast in situ within the seabed and extending within the seabed over a length Vergussmassesäule, wherein the anchor tube extends over a partial length within the Vergussmassäule and at least to the sea level. The foundation pile according to the invention may comprise at least one protective casing which extends only over a partial length of the casting-mass column.

Alternatively, the foundation pile may be provided with a sheet piling enclosure extending over a partial length of the potting column.

The object underlying the invention is finally achieved by an offshore structure with a pile foundation, comprising a plurality of sinker sunk in the seabed and above the drop anchor extending, in-situ grouted Vergussmassesäulen, wherein the building is covered by anchor lugs, which are posted on the drop anchors.

Appropriately, the anchor lugs each extend through a Vergussmassäule or in this approximately longitudinally.

The offshore structure according to the invention may for example comprise a monopile, which has been constructed in a conventional manner and which comprises a bracing over a plurality of anchoring lugs.

The offshore structure according to the invention comprises a pile foundation formed according to the invention, the pile foundation being carried out by the method according to the invention.

The invention will be explained below with reference to an embodiment shown in the drawings.

Figur 1:

zeigt eine Seitenansicht eines Monopile-Fundaments eines Offshore-Bauwerks nach dem Stand der Technik,

Figur 2:

zeigt eine entsprechende Ansicht eines Offshore-Bauwerks, welches nach der Erfindung gegründet ist,

Figur 3:

zeigt eine Draufsicht der Ansicht gemäß Figur 2,

Figur 4:

zeigt eine Darstellung eines Fallankers gemäß der Erfindung,

Figuren 4a bis 4c:

zeigen den Fallanker gemäß Figur 4 jeweils in der Oberansicht mit einem, vier oder fünf Ankertrossen und

Figuren 5, 5a, 5b:

das Absetzen des Fallankers nach dem erfindungsgemäßen Verfahren.

Show it:

FIG. 1:

shows a side view of a monopile foundation of an offshore structure according to the prior art,

FIG. 2:

shows a corresponding view of an offshore structure, which is founded according to the invention,

FIG. 3:

shows a plan view of the view according to FIG. 2 .

FIG. 4:

shows a representation of a drop anchor according to the invention,

FIGS. 4a to 4c:

show the fall anchor according to FIG. 4 each in the upper view with one, four or five anchor tubes and

FIGS. 5, 5a, 5b:

the settling of the fall anchor according to the inventive method.

It is first referred to FIG. 1 showing a monopile 1 of the prior art. On the monopile 1, a transition piece 2 is mounted with a platform 3 and a connection structure, not shown. The transition piece 2 is referred to in the prior art as a so-called "transition piece".

The monopile 1 according to the invention has a relatively large diameter and was placed in the seabed 4 either by ramming or flushing.

The FIG. 2 shows in direct comparison to the FIG. 1 an offshore structure according to the invention also comprising a monopile 1, a transition piece 2 and a platform 3.

However, the monopile 1 according to the invention is shorter and slimmer than the monopile 1 according to the prior art. The former is guyed over four anchor lugs 5, each of which is posted to a foundation pile 6 in the seabed 4. More precisely, each anchor line 5 is fastened to a drop anchor 7 and extends through a potting column 8 which is arranged above the drop anchor 7 and which has been cast in situ in the seabed. The Vergussmassäule 8 has been created without permanent formwork and without standpipe, as will be explained below. Accordingly, the Vergussmassäule 8 has no regular outer contour.

The FIG. 3 shows a plan view of the arrangement according to FIG. 2 ,

An embodiment of the fall arrester 7 is in FIG. 4 shown. The fall anchor 7 is a drop anchor in the sense of the preceding statements. This comprises a torpedo-shaped base body 9, which has a Eindringpitze 10 at its leading end and its trailing end is provided with four guide vanes 11.

At the trailing in the direction of fall / rear end of the base body 9 an anchor tube 5 is posted, which is arranged concentrically to a Vergussmasseleitung 12.

In the illustrated example, an extra concentric arrangement of Vergussmasseleitung and the anchor tube 5 is provided such that the anchor tube 5 extends within the Vergussmasseleitung 12, alternatively, of course, can be provided to move one or more Vergussmasseleitungen 12 parallel to the respective anchor line 5.

Of course, can be connected to a drop anchor 7 more anchor lugs 5, as in the Figures 4b and 4c is hinted at. These figures show each, as well as FIG. 4a , A plan view of the fall anchor 7 according to FIG. 4 ,

In the method according to the invention, it is provided to shoot the fall anchor 7 by utilizing a certain drop height and fall energy into the seabed 4, wherein the fall anchor 7 carries along the anchor line 5 and the potting ground line 12. Then, a potting compound, for example concrete, is pressed under pressure into the shot channel 7 produced by the drop anchor 7 in the subsoil 4, so that the in FIG. 2 above the drop anchor 7 extending Vergussmassesäule 8 results. As potting compound is a concrete or anchor mortar into consideration. Hardens the potting compound, this results in the FIG. 2 illustrated foundation pile 6, from which the anchorage trunk 5 is led out. The settling of the drop anchor 7 is in the Figures 5, 5a and 5b shown relatively simplified.

The drop anchor 7 hangs on a crane 13, which is placed on a provisionally already established platform 3. The platform 3 may be part of the offshore structure to be anchored.

The drop anchor 7 is struck on the one hand on the anchor line 5, on the other hand suspended from a discharge line 14.

It should be noted that of course the drop anchor 7 can be started by a ship.

With a protective tube 15 is designated, whose diameter is slightly larger than that of the fall anchor 7. The protective tube was only slightly washed into the subsoil 4 and extends well above sea level 16.

The drop anchor 7 is inserted into the upper end of the protective tube 15, then the drop anchor 7 is separated from the discharge line 14 or dropped with the discharge line 14 by utilizing its kinetic energy. The fall anchor 7 drops through the protective tube 15 and penetrates into the subsoil 4, wherein it simply entrains only the attached to this anchor tube 5 and the Vergussmasseleitung 12.

At the distal end of the anchor tube 5, a float 17 is attached, which allows floating of the anchor tube 5. The anchor pipe 5 can be picked up in this way by a supply ship and, for example, attached to the offshore structure and stretched.

The drop anchor 7 may have been provided with appropriate ballast prior to discharge, which is why the main body 9 of the drop anchor 7 may be provided with corresponding chambers.

The mass of a drop anchor may be between about ten and one hundred tons, such as a drop anchor may, for example, have a length of up to twenty meters and a diameter of up to one meter.

LIST OF REFERENCE NUMBERS

1

monopile

2

Transition piece

3

platform

4

Subsoil

5

anchor lines

6

foundation pile

7

case anchor

8th

Vergussmassesäule

9

base body

10

indenting

11

vanes

12

Vergussmasseleitung

13

crane

14

shedding strand

15

thermowell

16

Sea level

17

float

Claims (18)

1. Method for producing a foundation pile (6) for offshore structures, comprising the following method steps:

   - supplying and arranging a drop anchor (7) at a predetermined height above the seabed (4),

   - fastening at least one anchor cable (5) to the drop anchor,

   - fastening at least one casting material line (12) to the anchor cable (5),

   - dropping the drop anchor such that it penetrates into the seabed on account of its kinetic energy, and

   - introducing a curable casting material into the shot channel produced by the drop anchor upon penetration into the seabed.
2. Method according to Claim 1, characterized in that the casting material is introduced into the shot channel at least over a part of the length of the tension element, wherein the anchor cable remains in the cured casting material.
3. Method according to either of Claims 1 and 2, characterized in that the tension element is provided with at least one float (17) which is arranged at a predetermined distance from the drop anchor, wherein the distance is selected according to the planned penetration depth of the drop anchor into the seabed and according to the height of the sea level (16) above the seabed.
4. Method according to one of Claims 1 to 3, characterized in that, prior to dropping, the drop anchor is provided with ballast, wherein the ballast mass is selected such that the drop anchor penetrates into the seabed down to a load-supporting subsoil horizon.
5. Method according to one of Claims 1 to 4, characterized in that the drop anchor is suspended on a drop string (14) and dropping is effected by actuating a release mechanism on the drop string.
6. Method according to one of Claims 1 to 5, characterized in that the drop anchor is brought into the seabed through a protective tube (15) or through a sheet piling enclosure.
7. Method according to Claim 6, characterized in that, prior to dropping the drop anchor, the protective tube is water-jet-driven into the seabed.
8. Method according to either of Claims 6 and 7, characterized in that the seabed within the protective tube or within the sheet piling enclosure is fluidized by injecting compressed air or water prior to dropping the drop anchor.
9. Method according to Claim 6, characterized in that the protective tube is pumped empty prior to dropping the drop anchor.
10. Method according to one of Claims 1 to 9, characterized in that at least one casting material line having a plurality of outlet openings for the casting material that are provided at a distance from one another in the longitudinal direction is used.
11. Method according to one of Claims 1 to 10, characterized in that the casting material line is drawn during the casting operation.
12. Method according to one of Claims 1 to 11, characterized in that the casting material line is lost at least over the subportion extending in the shot channel.
13. Foundation pile (6) for offshore structures, produced according to a method according to one of Claims 1 to 12, wherein the foundation pile comprises a casting material column (8) cast in situ within the seabed (4) and extending within the seabed (4) over a length, and wherein the anchor cable (5) extends within the casting material column (8) and at least up to the sea level (16).
14. Foundation pile according to Claim 13 having a protective casing which extends over a part of the length of the casting material column (8).
15. Foundation pile according to Claim 13 having a sheet piling enclosure which extends over a part of the length of the casting material column (8).
16. Offshore structure having a pile foundation comprising a plurality of foundation piles according to one of Claims 13 to 15 which are sunk in the seabed (4) and cast-in-situ casting material columns (8) extending above the drop anchors (7) of the foundation piles, wherein the structure is braced by means of anchor cables (5) which are fixed to the drop anchors (7).
17. Offshore structure according to Claim 16, characterized in that the anchor cables (5) extend through the casting material columns.
18. Offshore structure according to either of Claims 16 and 17, characterized in that it comprises a monopile (1) and bracing by means of a plurality of anchor cables (5).

Images