BASE STRUCTURE FOR OFF-SHORE WIND TURBINES AND METHOD FOR BUILDING THEREOF

Abstract

The invention relates to a base structure for an off-shore wind power installation having a plurality of base piles wherein each base pile has a driving pile which is guided in its interior at least portion-wise for anchoring in the seabed, and at least one support structure for mounting a pylon of a wind power installation, wherein the support structure connects the upper ends of the base piles together. Furthermore the base pile and the driving pile have a region of an overlap on a predetermined lengthwise portion, wherein in the overlap region of the piles the gap between the piles and in part beneath and above the overlap region the free internal cross-section of the piles are filled with a hardening filling material. The invention also relates to a method of erecting a base structure for an off-shore wind power installation and an aligning tool.

Description

The invention relates to a base structure for an off-shore wind power installation having at least a plurality of base foundation piles, wherein each base pile has a driving pile which is guided in its interior portion-wise for anchoring in the seabed, and at least one support structure for mounting the wind power installation.

The invention also concerns a method of erecting a base structure for an off-shore wind power installation.

Known base or foundation structures for hydraulic structures such as for example for off-shore wind power installations usually form the transition from the structure to the ground, in the present case the hydraulic structure to the seabed, and are intended to ensure secure anchoring in the seabed. Specifically off-shore wind power installations are increasingly being located at some distance from the coast and as a result frequently in depths of water of up to 50 meters or more. By virtue of the ambient conditions prevailing at such an installation location and the wind and wave loads which generally act on the base structure and the hydraulic structure, correspondingly high demands are made on anchorage of the base structure in the seabed and the base structure carrying the hydraulic structure itself.

EP 1 673 536 B1 describes for example a base structure for an off-shore wind power installation, having a plurality of base piles with respective driving piles which are at least portion-wise guided in the interior of the respective base piles, for anchorage in the seabed. The base structure further has at least one support structure for mounting the pylon of the wind power installation, wherein the support structure connects the upper ends of the base piles together. In that case, after piling of the driving piles, a predetermined lengthwise portion is produced, in which the driving piles are received by the base piles. To prevent relative movement between the base piles and the driving piles and thereby possibly cause loosening of the anchorage of the base structure in the seabed, an adhesive join is made in a part of the overlap region between the outside of the driving pile and the inside of the base pile. The relatively narrow adhesive join between the outside of the base pile and the inside of the driving pile means that on the one hand there is the risk that the adhesive tears and thus the driving pile is again movable relative to the base pile. In addition, it is in the region of the seabed that the highest moment caused by the wind and wave loads acts on the base and driving piles of the base structure so that the constant changes in load shortly beneath the overlap region of the piles can result in deformation and possibly bending of the walls of the driving piles, which at any event can have a detrimental effect on the anchorage thereof and thus on the operationally reliable long-term function of the base structure.

Therefore the object of the present invention is to improve a base structure of the above-indicated general kind such that deformation phenomena at the piles, by virtue of the load changes acting thereon, are avoided. The further object of the invention is to provide a method of erecting a base structure for a hydraulic structure, which can be carried out in a simplified and reliable fashion, in particular a method of erecting a base structure, by means of which the base structure can be aligned in simplified fashion.

According to the invention the object is attained by a base structure having the features of claim 1, and by a method as set forth in claim 9. Advantageous developments and configurations of the invention are recited in the claims appendant to claims 1 and 9.

In the case of a base structure for an off-shore wind power installation having at least a plurality of base piles, wherein each base pile has a driving pile guided in its interior at least in portion-wise manner for anchorage in the seabed, and at least one support structure for mounting the pylon of a wind power installation, wherein the support structure connects the upper ends of the base piles together, it is provided that the base pile and the driving pile have a region of overlap on a predetermined lengthwise portion, wherein in the overlap region of the piles, in at least portion-wise manner, the gap between the piles, and over a portion of the overlap region and in a part beneath the overlap region, the free internal cross-section of the driving pile is filled with a hardening filling material.

By means of such a strong structure around the overlap region of the base piles and the driving piles which are region-wise accommodated by the base piles, in particular buckling or kinking of the pile walls is advantageously prevented in the region of the seabed by the filling material which has portion-wise hardened within the driving pile and between the base pile and the driving pile. The filling material which extends to beneath the overlap region in the interior of the driving pile imparts thereto optimum stiffness over a predetermined part thereof, whereby the driving pile can be made up from a single-walled tube. The hardening filling material which preferably respectively extends from below to above the overlap region, such as for example concrete, advantageously produces a base structure, by means of which it is possible without any problem to guarantee an operationally reliable long-term function of the at least required period of 20 years.

Advantageously in a development of the invention it is provided that the base pile in the foot region has a guide for the driving pile, which reduces the free cross-section of the base pile at the inner peripheral surface. The use of a guide has the advantage that the driving pile is axially movably guided during the driving operation in particular at the beginning of the driving works, so that the driving pile is driven into the seabed with its center line preferably coaxially with respect to the center line of the base pile. That is intended advantageously to prevent the driving pile from running out. In that case the guide is provided approximately over half of the overlap region of the two piles in the gap between the inside of the base pile and the outside of the driving pile at least region-wise over the periphery thereof. The guide can be for example in the form of a sleeve. Preferably a plurality of plates are used, the longitudinal axes of which extend parallel to the center line of the base pile and extend radially from the inside of the base pile in the direction of the center line.

Optionally the base pile has a bottom ring with a seal which seals off the gap relative to the driving pile, whereby on the one hand the ingress of sea water, as well as pieces of rock and mud, in particular into the gap in the region of the guide, is avoided during and after the pile driving operation. That therefore prevents unwanted fouling of the portion of the base pile and the driving pile, that is to be subsequently concrete-filled. On the other hand the seal in the region of the gap also prevents the escape of the subsequently introduced filling material. Therefore the hardening filling material always remains at the same level in the gap between the base pile and the driving pile and can accordingly involve a fixed connection to the surfaces of the respective pile walls. To produce the seal on the bottom ring, it is possible for example to use a felt or another suitable material which is suitable for preventing the entry of water or the ingress of mud. In addition, a bursting disk can be fitted on the bottom ring from below, which disk effectively closes the free cross-section of the driving pile which is preferably in the form of a tube and which is thus downwardly open, and thus already prevents the entry of sea water when lowering the construction part serving to produce the base structure, on to the seabed; the bursting disk is already destroyed by the driving pile which is preferably driven perpendicularly downwardly, when the construction part is placed on the seabed but at the latest with the beginning of the pile driving operation, and in that case the bursting disk does not represent any impediment for the pile driving operations to be performed.

Alternatively it may be advantageous not to provide a seal. Thus when the base structure is lowered from a ship on to the seabed water can pass controlledly and uniformly into the base piles. The risk of a suddenly occurring leak in a sealed base pile causing a sudden shift in the center of gravity and thus tipping of the base structure is reduced. The seal and the bursting disk can then be omitted.

The base pile preferably has an inner tube providing its inner peripheral surface and an outer tube providing its outer peripheral surface, a core material being arranged between the inner tube and the outer tube. Such a wall structure according to the invention provides a structurally advantageous possible way of forming the base piles. The sandwich structure of the pile wall on the one hand improves the stiffness of the base pile while on the other hand the amount of steel usually employed to produce the base pile can advantageously be reduced thereby. Due to the increased stiffness, both the diameter and also the overall thickness of the inner and outer tubes can be markedly minimised, which at the same time advantageously improves the economy of such base structures according to the invention by virtue of reduced production and material costs. The core material as the intermediate layer between the inner and outer tubes is in particular additionally strengthened with reinforcement which is arranged in the form of concrete reinforcing steel bars or in the form of a hollow-cylindrical lattice in the core material. It is provided in that case that the reinforcement is always completely enclosed by the core material and is arranged at a spacing relative to the inside of the outer tube and the outside of the inner tube.

It is advantageously provided in a development that the driving pile has a bulkhead which is arranged at a spacing beneath the overlap region and which closes off the free internal cross-section of the driving pile. The entry of water or mud by way of the driving pile which is of a hollow-cylindrical configuration into the interior of the base pile is avoided by means of such a bulkhead in the operation of driving the driving pile so that the free cross-section of the driving pile is filled with seabed only as far as the bulkhead. In addition the bulkhead serves as a filling limit for the filling material which is to be introduced into the driving pile head and which hardens therein and which imparts improved stiffness to the driving pile. The bulkhead is in particular a plate body which extends with its plate plane perpendicularly to the center line of the driving pile and which is sealingly connected in peripheral relationship to the inside of the wall of the driving pile, in particular being welded thereto. In that case the bulkhead is arranged approximately at a spacing beneath the end of the base pile, that corresponds to the length of the overlap of the piles.

To avoid an excessive build-up of pressure in the interior of the driving pile and thus an unnecessary counteracting force in the pile driving operation venting of air from the interior of the driving pile is to be provided. For that purpose in its pile wall beneath the bulkhead the driving pile has at least one opening. Accordingly air in the driving pile can escape in the driving operation so that the constituents of the seabed can rise up in the free cross-section of the driving pile to below the bulkhead. In that respect it is advantageous if a plurality of openings are provided beneath the bulkhead over the length of the driving pile and at the same time a plurality of openings are arranged in the pile wall at the same height level distributed around the periphery of the driving pile. In addition each opening for air venting in the wall of the driving pile can be sealed with a suitable material which dissolves for example upon contact with water and thus the openings are successively opened for air venting purposes in the longitudinal direction in the wall of the pile.

In an optional configuration, at its outside peripheral surface, the driving pile has a radially outwardly extending step as an abutment against the guide of the base pile, by means of which the driving pile is brought into contact in positively locking relationship in the longitudinal direction with in particular the plates forming the guide at the inside of the base pile and exerts a holding force perpendicularly downwardly on the base pile. The step which extends in an annular shape along the peripheral surface of the driving pile is in particular arranged in spaced relationship with the upper end of the driving pile so that there is always a given portion of the driving pile that projects freely into the base pile above the guide. That provides a gap between the outside of the driving pile and the inside of the base pile, into which gap the filling material can be introduced. The radially outwardly extending peripheral surface of the step can be at the same time in the form of a guide surface for support against the inside of the base pile. That further improves guidance for the driving pile within the base pile and at the same time advantageously prevents the driving pile from running out in the pile driving operation. The step can be in particular a flange-like ring body welded to the outer peripheral surface of the driving pile.

Another development provides that the driving pile is at least portion-wise provided with reinforcement on the inside of the pile wall. In particular the subsequently introduced filling material is strengthened by means of the reinforcement, while in addition its tensile strength is increased and thus the load-bearing capability of the piles is markedly improved in the region of the seabed. Specifically forces acting dynamically on the base structure can be absorbed without any problem by the reinforced component structure of the base. In particular concrete reinforcing steel in the form of bars is used as reinforcement, which are arranged on a predetermined part-circle diameter in spaced relationship with the inside of the driving pile. In place of individual bars it is also possible to use a cylindrical reinforcing cage which extends similarly to a mesh on a uniform radius around the center line of the driving pile.

A development of the invention provides that beside the base piles at least one further partial region is in the form of at least one tube portion of a bar of the lattice-like support structure which is composed of a plurality of bars. That advantageously also achieves increased strength in the lattice-like support structure which connects the upper ends together and by means of which the wind power installation is mounted and a direct connection is made between the base structure and the pylon of the wind power installation. The number of bars can be reduced, by virtue of the improved stiffness, by means of the configuration according to the invention of tube portions of the bars used in the support structure. A saving of steel material is advantageously also achieved thereby, in the region of the support structure, with at the same time improved stiffness thereof. The bars used for forming the lattice-like support structure are in particular of a cylindrical cross-section, wherein the configuration of the wall according to the invention can extend both over the entire length of a bar and also only over a given bar or tube portion.

At least one of its end regions each tube portion is provided with a bulkhead which sealingly closes off at least its internal free cross-section. That already prevents in particular the ingress of moisture into the interior of the free tube portion before assembly to constitute a support structure connecting the base piles together. Furthermore the bulkhead can additionally serve as a filling limit for a filling material introduced in the region of the node points produced in the support structure. In this connection the bulkhead can be a circular plate body which can be connected at its periphery to the inside of the inner tube, in a connection involving intimate joining of the materials involved, for example by welding.

It is further provided that each tube portion has a reinforcement projecting at its end beyond its bulkhead. The reinforcing steel which is used for example between the outer and inner tubes of the tube portion accordingly projects beyond the bulkhead into a filling space for filling material to be introduced thereinto, the filling space possibly being formed on both sides of the ends of the tube portion of the bar of the support structure. When using a hardening filling material the projecting portions of the reinforcement of the tube portion then involve a connection to the hardened filling material, that involves intimate joining of the materials involved, after the filling material has set.

At least one of its ends each tube portion has an annular connecting surface extending in a plane oriented perpendicularly to the center line of the tube portion. A respective tube portion involving the sandwich structure according to the invention accordingly always has straight ends extending perpendicularly to its center line. Each tube portion according to the invention can be connected to connecting tube portions forming the ends of a respective bar, by way of the straight ends having a respecting connecting surface at the ends. The connection of a respective individually prefabricated tube portion to a connecting tube portion of conventional nature can in that case be advantageously easily effected by means of orbital welding devices, wherein the tube portion and the connecting tube portion are in particular welded together to form a bar of the support structure.

A further development of the invention provides that each tube portion is equipped with tie elements which act parallel to its center line and which are provided for spanning over at least one node point formed in the connecting region of two component parts of the base structure. The use of tie elements in the region of a node point has the advantage that a respective tube portion according to the invention is drawn in the direction of a node point by means of the tie elements which in particular are in the form of tie bars. Welded seams in the compression region are thus exposed to reduced load changes whereby at the same time the fatigue characteristics thereof are advantageously reduced. A plurality of tie bars are used on a tube portion, the tie bars being arranged uniformly on a part-circle diameter near the tube wall of the tube portion. That always ensures an advantageous application of force in the region of the node points. The tie bars can be for example arranged with their head end at a bulkhead in a respective end region of the tube portion. The be elements which in that case are preferably in the form of tie bars also extend parallel to the center line of a respective bar of the support structure for example as far as in a tube portion of a base pile or a bar extending at an angle thereto.

There is further provided a method of erecting a base structure for a hydraulic structure, in particular for an off-shore wind power installation, in which a plurality of base piles provided with driving piles are pre-assembled with at least one support structure comprising bars to form a construction part, the pre-assembled construction part is transported to the installation location and placed with its base piles leading on the seabed, then the driving piles are driven into the seabed and a base portion anchored in the seabed is produced, and finally a hardening filling material is introduced into the base portion into at least the overlap region of the piles and thus a solid base structure is formed.

Alternatively the base structure or the base portion is welded to the support structure only after the base piles have been set in place and after pile driving of the driving piles. Preferably connecting bodies are provided for that purpose, by means of which the support structure can be connected to the base piles by means of orbital welding.

A base structure can be produced in a simplified but at the same time reliable fashion by means of the method steps according to the invention and the specifically implemented sequence thereof. Pre-assembly of the base piles and the driving piles respectively accommodated therein with the support structure to afford a finished construction part is preferably still effected on land so that this ensures relatively accurate pre-assembly. The finished construction part is then lifted on to a floating platform and transported by means thereof to the predetermined installation location. The still relatively light construction part with its piles and the support structures is then lifted with a lifting apparatus, for example a floating crane, off the platform in one piece, and lowered with its base piles facing perpendicularly downwardly until the base piles contact the seabed. After the lowering operation the driving piles are successively driven into the seabed with a slender pile driver, thereby providing for firm anchorage of the construction part and thus producing a base portion. Finally a hardening material such as for example concrete is introduced into at least the overlap region of the piles. Preferably the filling material is introduced both into the free cross-section of the driving pile in a portion beneath the overlap region of the piles, into a region above the overlap region, so that at the same time the filling material also runs into the gap above the guide of the base pile between the driving pile and the base pile. After hardening of the filling material, that affords a base structure which is so strong and firm that it carries without any problem the dynamic fluctuating loads of wind and waves that act on the base structure.

In a development of the invention it can be provided that after the pile driving operation the hardening filling material is also introduced into a gap between an inner tube and an outer tube of a respective base pile and thereafter the upper ends of the base piles are closed. Subsequent introduction of the filling material between the inner and outer tubes, in contrast to an operation of introducing the filling material which has already been effected in the pre-assembly stage, as a core material between the inner and outer tubes, gives the advantage that the construction part is of lower inherent weight and can thus be easily lifted and aligned upon being loaded on to a floating platform and in the operation of placing it on the seabed.

In a preferred development of the method or in a further aspect of the invention the aforementioned object is attained by a method of erecting a base structure for an off-shore wind power installation, in which a plurality of and preferably three base piles equipped with driving piles are pre-assembled with at least one support structure consisting of bars to afford a construction part, the pre-assembled construction part is transported to the installation location and placed with its base piles leading on the seabed, then the driving piles are driven into the seabed and a base portion anchored in the seabed is produced, wherein the method comprises the step of: aligning the base portion in such a way that a central axis of a central mounting for mounting the pylon of a wind power installation is oriented substantially vertically. A filling material is preferably introduced after the alignment operation. Preferably alignment of the base portion or the base structure is effected in such a way that an angular deviation between the central axis of the central mounting and a vertical line is less than 2°, preferably less than 1°, preferably less than 0.5°. The pylon of an off-shore wind power installation is received in the central mounting. Wind power installations have a high pylon which can exceed 100 m. It is therefore necessary for the base structure to be aligned substantially vertically so that the angular deviations are slight. It is only in that way that a wind power installation can be securely and reliably installed by means of the base structure. When driving the driving piles into the seabed it happens that the latter subsides at places so that the base structure set in place thereon is not exactly vertically oriented. Previous methods therefore provide that the central mounting at the upper end of the support structure is to be subsequently adapted to the base structure. Such adaptation includes in particular the production of special connecting flanges which compensate for the angular inaccuracies. It will be noted however that this is highly complicated and expensive and requires additional operating steps and material. That also results in additional connecting locations between the base structure and the wind power installation to be mounted thereon, which can later lead to fatigue of the base structure. Complicated and expensive measures of that kind, such as in particular the production of connecting flanges, are eliminated by the base portion or base structure being appropriately aligned.

Preferably the alignment operation includes displacing at least one, preferably two of the three, base piles relative to the driving pile by means of an aligning ram arranged completely within and/or above the base pile. Such an aligning ram is preferably in the form of or has an aligning device. If the base structure has three base piles, as is particularly preferred, it can be suitably aligned by displacement of two of the three base piles relative to the corresponding driving piles. The base piles are accordingly displaced along the driven-in driving piles by a difference so that the lifted base piles are then no longer standing on the sea bottom. The aligning ram, by means of which the corresponding base pile is lifted, is in that case arranged completely within and/or above the base pile. It can be arranged substantially in the base pile and can project out of the base pile at an upper side thereof. The base piles extend from the seabed or shortly above the seabed to a position above the surface of the sea. Because the aligning ram is arranged substantially within and/or above the base pile, it is not exposed to any flow or any pounding by the waves so that the operation of positioning such a ram and operating thereon are substantially simplified.

In a preferred development the method further includes the step of: introducing the aligning ram from an upper and of the base pile, which is above the surface of the sea, into the base pile, contacting a ram head of the aligning ram with the driving pile, bringing a support device of the aligning ram into engagement with the base pile, and extending a portion of the aligning ram to displace the base pile relative to the driving pile. After the base structure with the base piles has been placed on the seabed and the driving piles have been at least partially and preferably completely driven thereinto, the aligning ram is introduced into the base pile from the upper open end thereof. In that case the aligning ram is preferably introduced into the base pile with its ram head leading. The ram head has a contact portion, with which it comes into contact with the driving pile to be supported thereagainst. That is advantageous as the ramming pile is stationary and does not yield after having been driven in, so that it forms an advantageous support point for the aligning ram. The aligning ram further has a support device which is adapted to come into contact with the base pile. The base pile can be supported against the aligning ram by means of the support device. For that purpose the base pile preferably has a support portion which for example can be in the form of a radially inwardly projecting shoulder. After the ram head has come into contact with the driving pile and the support device has been brought into engagement with the base pile the aligning ram or at least a portion thereof is extended in such a way that the base pile is displaced relative to the driving pile upwardly with respect to a conventional installation direction. Extension is preferably effected hydraulically. For that purpose the aligning ram preferably has at least one hydraulic cylinder, by means of which the base pile is lifted or displaced relative to the driving pile. The hydraulic cylinders can be for example in the form of part of the support device so that the base pile is supported on the hydraulic cylinders. As an alternative to the hydraulic cylinders it is also possible to use screw spindles, toothed rack drives, cable arrangements and the like.

Preferably the method further includes the step of: introducing filling material through a passage in the aligning ram into the driving pile and/or the overlap region between the driving pile and the base pile. The aligning ram is arranged in the base pile in the aligning procedure and the lifted base pile is supported at the aligning ram which is supported on the driving pile. For finally fixing the displaced positions of the base pile and the driving pile relative to each other it is preferable for filling material to be introduced at least into the intermediate space between the driving pile and the base pile, preferably also into the interior of the driving pile, and into a portion beneath the overlap region and above the overlap region between the driving pile and the base pile. Because the aligning ram has a passage through which filling material can be introduced, it is advantageously guided to the required locations. Additional tubes, hoses and the like can be eliminated. That further simplifies erection of the base structure.

In a further preferred embodiment of the invention it has the step of: closing, preferably air-tightly sealing, the upper open end of at least one base pile by means of a closure device. Beforehand, preferably the aligning ram and further tools and components disposed in the base pile are removed therefrom. Closing the upper open end of the base pile and in particular air-tight sealing thereof, prevents water and in particular oxygen-rich water from being able to penetrate into the interior of the base pile and prevents air exchange from occurring between a space inside the base pile and a surrounding atmosphere. That therefore prevents further oxygen being passed into the space inside the base pile, whereby it is possible to prevent oxidation of the inside surface of the base pile. That improves the service life of the base structure. In addition further anti-corrosion measures can be eliminated in that way. Such a closure device preferably has a head cover for closing the upper end of the base pile and a sealing material, for example concrete, for sealing off the head cover with respect to the base pile.

The above-described method of erecting a base structure uses an aligning ram which is preferably of the following configuration: the aligning ram has a ram tube, a ram head connected to the ram tube and a support device. The ram tube forms the passage for feeding the filling material. The ram head has a contact surface for coming into contact with the base pile. Preferably the ram head has a centering projecting so that the ram head and thus the aligning ram are fitted in centered relationship on the driving ram even in the event of less accurate introduction of the aligning ram into the base pile. The driving pile can be easily damaged at the upper end by the pile driving operation. It is therefore particularly advantageous for the ram head to have a centering projection so that the ram head is placed in centered relationship on the driving pile even in the case of a damaged driving pile. The support device is preferably arranged at an upper end of the aligning ram, preferably adjacent to the upper end of the base pile at the ram tube or a ram body. The support device is preferably arranged in height-adjustable or position-adjustable relationship on the ram tube or a ram body. The support device preferably has one or more hydraulic cylinders adapted to come into contact with a support portion of the base pile in order to displace it relative to the ram head, the ram tube and/or the driving pile. Hydraulic cylinders are particularly preferred as high loads can be carried thereby and exact displacement of the base pile relative to the driving pile even by short distances is possible. Preferably the aligning ram, in particular the ram tube and/or the ram head, has guide surfaces and/or guide openings for guiding filling material. Filling material can be introduced in specifically targeted fashion into a gap between the driving pile and the base pile, into the interior of the driving pile and/or into a portion above and below the overlap region, by means of such guide surfaces and/or guide openings. A base pile and therewith also a base structure can be easily aligned and oriented by such an aligning ram. The aligning ram is re-usable, it is employed only as a tool. It can also be carried on a fitting ship and can be employed when required, that is to say in the event of a base structure being set up in inadequately oriented relationship. As the aligning ram is let down from above the surface of the sea into the interior of the base pile and operation is necessary only at the upper and of the aligning ram, there is no need for complicated and expensive diver interventions. That provides that erecting the base structure can be effected substantially less expensively and faster.

Embodiments of the invention showing further inventive features are illustrated in the drawing in which:

FIG. 1 shows a view of a base structure according to the invention,

FIG. 2 shows a view of a portion of a base pile used for anchorage in the seabed and the driving pile guided therein, in section,

FIG. 3 shows a view of a base pile with a driving pile with an aligning ram arranged in the interior of the base pile,

FIG. 4 shows a view of the upper end of a base pile in a closed condition,

FIG. 5 shows a detail view of a portion from FIG. 4, and

FIG. 6 shows a fully sectioned overall view of a base pile.

Reference 1 (FIG. 1) denotes a base or foundation structure for an off-shore wind power installation, which has three vertically extending base piles 2, 3 and 4 and a support structure 5 having a plurality of bars 6, 7, 8 and a central mounting 9 for the pylon of a wind power installation (not shown). The base piles 2, 3, 4 stand on the seabed 10, driving piles 11, 12, 13 fixedly connected thereto projecting out of same for anchorage in the seabed. The base piles 2, 3, 4 are arranged parallel to each other. To ensure secure anchoring the driving piles 11 through 13 have a portion which is driven into the seabed and which approximately corresponds to the depth of water at the installation location. The support structure 5 connects at the same time the upper or free ends of the base piles 2, 3, 4 together above the water line 14 so that forces acting on the base structure 1 or the wind power installation, due to wind and wave loads, are advantageously distributed to all three base piles 2 through 4 and their driving piles 11 through 13. In addition, provided at a predetermined depth of water above the seabed 10 is a second support structure 15 having bars 16, 17, 18, which advantageously fixes the three base piles 2 through 4 relative to each other during movement to the installation location or during the pile driving operation. Both the base piles 2 through 4 and the driving piles 11 through 13 and also the posts or bars 6 through 8 of the support structure 5 are preferably of a cylindrical configuration.

The central axis 9a of the central mounting 9 is exactly vertically oriented. If after the base structure has been set up the central axis 9a involves a deviation relative to the vertical, which exceeds a predetermined deviation (for example 1 degree), it is preferable for the base structure to be aligned by means of an aligning ram 100 (see FIG. 3) as described hereinafter.

FIG. 2 shows a partial view of one of the base piles 2 through 4 with one of the driving piles 11 through 13 accommodated therein in section and is intended in particular to more clearly show the structure thereof. Each of the base piles 2 through 4 has a wall of a plurality of layers 19, 20, 21 of different materials. Introduced between the inner, preferably metallic layer 19 and the outer metallic layer 20 is an intermediate layer 21 of a core material such as for example concrete. In its foot region each base pile 2 through 4 has a guide 22 for the driving pile, that reduces its free cross-section at the inner peripheral surface, whereby the driving piles are prevented from running out during the pile driving operation. In that arrangement the guide is formed by means of four plates 23, 23′ which are arranged at the inner layer 19 of a base pile and which extend at an angle of 90 degrees relative to each other at the inside of the inner layer in the longitudinal direction and extend radially inwardly. To provide a stable end position for the driving piles 11 through 13 in a respective base pile 2 through 4 provided at the outside of each driving pile at a predetermined spacing beneath the upper end is an annular abutment 24 which comes to lie on the upper ends of the plates 23, 23′ of the guide 22 so that portions of the two piles provide relative to each other an overlap region 25 of a predetermined length. The abutment 24 can equally be omitted.

Provided at the underside of each base pile there is also a bottom ring 26 having a seal for sealing off the guide gap relative to the driving pile. That seal can also be omitted depending on the respective use. It is not required for the invention. Each driving pile 11 through 13 has a delimited driving pile head 27 delimited by a bulkhead 28 which is arranged at a spacing from its upper end, that approximately corresponds to double the length of the overlap region 25, closing off the free internal cross-section thereof. Both the driving pile head 27 above the bulkhead 28 and also the gap 29 between the outside of the driving pile and the inside of the base pile as well as the part of the base pile above the overlap region 25 are filled with a hardening filling material 30. To improve the tensile strength of the filling material 30, a reinforcement 31 of for example bars is arranged at least portion-wise on the inside of the driving pile wall. Each driving pile 11 through 13 also has beneath the bulkhead 28 at least one opening 32 in its pile wall for advantageous air venting during the operation of driving the pile into the seabed 10.

FIG. 3 illustrates a base pile 2 set up on the seabed 10, together with driven-in driving pile 11 and an aligning ram 100 which has been introduced into the base pile 2. Identical or similar elements are denoted by the same references. In that respect reference is directed in its entirety to the foregoing description.

In this embodiment which substantially serves to illustrate the aligning ram 100 the base pile 2 is in the form of a single-layer, single-walled based pile. Preferably however it is in the form of a multi-layer or sandwich pile, in accordance with the foregoing description. At its lower end (with respect to FIG. 3) the base pile 2 has a bottom ring 26 forming a support surface for the base pile 2. In that case the bottom ring 26 forms a radial enlargement of the base pile 2 so that it can sink less severely into the seabed 10. The bottom ring 26 is supported in relation to the base pile 2 by means of stiffening plates 34. In the case of a multi-layer base pile the stiffening plates 34 can be fixed to the outer layer, or also to the inner layer, and can extend outwardly through a slot in the outer layer.

Guide plates 23 for guiding the driving pile 11 in the pile driving operation are arranged at the lower end of the base pile 2, directed radially inwardly. In addition later, when introducing filling material 30, the guide plates 23 form a reinforcement for making a better connection between the base pile and the filling material 30 and thus also the driving pile. In addition arranged both on the base pile 2 and also on the driving pile 11 are reinforcing bars 33 which are also referred to as shear keys. In this embodiment the driving pile 11 does not have any abutment for abutting against the guide plates 23 as in that way the base pile 2 can be later displaced more easily relative to the driving pile 11 to align the base structure 1.

The aligning ram 100 has a ram tube 118, a ram head 106 and a support device 105. At its lower end, with respect to FIG. 3, the ram head 106 has a centering projection 117 for centeredly contacting the ram head 106 by means of the contact surface 119 with the upper end of the driving pile 11. The centering projection 117 is of a substantially frustoconical shape. The aligning ram 100 can thus be used for different diameters of driving pile tubes. Even if the upper and of the driving ram 11 is damaged, bent or caused to stick out by the pile driving operation the ram head 106 can be brought into contact in centered relationship with the driving pile 11. At its upper end the ram tube 118 has a filling material inlet 112 arranged above the surface of the sea. Filling material can be easily introduced into the interior of the driving pile 11 from above the surface of the sea through the ram tube 118 which also forms a ram body. That can be clearly seen from FIG. 3.

The support device 105 is arranged on the ram tube 118 in the proximity of the upper end of the base pile 2. In this embodiment it comprises support portions 107 which are height-adjustably fixed to the ram tube and hydraulic cylinders having a lower part 108 and an upper part 109. The base pile 2 is supported on the upper part 109 of the hydraulic cylinder. For that purpose at the upper end the base pile 2 has an upper plate 111 which is releasably fixed thereto and which is arranged on the base pile by means of a support ring 110. That upper plate 111, after the aligning operation, can be removed together with the support ring 110 from the base pile 2 and can be used again for aligning another further base pile. The overall procedure for mounting the support device 105, the support ring 110 and the upper plate 111 is effected above the surface of the sea and therefore does not require the use of divers. The hydraulic cylinder parts 108, 109 do not come into contact with sea water and therefore do not have to have any special corrosion protection.

The aligning operation can then take place as follows: an aligning ram 100 is let down into two of the three base piles 2, 3, 4, the ram head 106 of the aligning ram resting exactly on the upper end of the driving piles 11, 12, 13 by virtue of the conical centering projection 117. Conical centering is effective even if the head of the driving pile 11, 12, 13 should have been slightly damaged by the pile driving operation.

The support device 105 is then assembled in the finished condition so that the base pile 2, 3, 4 can be supported by means thereof on the aligning ram 100. The hydraulic cylinders 108, 109 are extended by pressure actuation after fitment of all components. The force produced by them acts on the aligning ram 100. The fact of the ram head 106 being supported on the driven-in driving pile 11, 12, 13 provides that the base structure or base piles, together with the support construction, is lifted at that location. The use of two aligning rams 100 provides that the base structure whose base piles correspond to the corners of a triangle is lifted at two of the corner points and can thus be exactly vertically aligned.

As soon as the desired position has been reached concrete 30 is introduced in a suitable amount through the ram tube 118 and laterally thereof. The concrete 30 which is introduced through the opening of the ram tube 118 will fix the driving pile 11, 12, 13 in position after setting and will seal off the interior of the base pile 2, 3, 4 to prevent the ingress of seabed which has possibly been washed up, from the interior of the base pile 2, 3, 4.

The very highly fluid concrete which flows laterally along the ram tube 118 slides off at the outside of the ram head 116 by way of the inclined surface 120 and thus flows into the intended position in the intermediate space between the base pile 2, 3, 4 and the driving pile 11, 12, 13. After the concrete has set the aligning ram 100 and the upper plate 111 are removed together with the support device 105.

After alignment of the base piles 2 and removal of the aligning ram 100 from the base pile 2 and preferably also removal of the upper plate 111 and the support ring 110, it is advantageous to close the upper end of the base pile 2. A closure device 150 is illustrated in FIGS. 4 and 5. Accordingly the closure device 150 substantially has a head cover 150 which is of a substantially plate-shaped configuration and is of a radius which very substantially corresponds to or is somewhat larger than the radius of the base pile 2. As can be seen from the detail view in FIG. 5 a seal holding ring 55 is arranged for the sealing device 150 in outward relationship at the upper end of the base pile 2, forming an annular passage for sealing material 54. Arranged on the head cover 50 is an annular axial projection 56 which engages into the annular passage of the seal holding ring 55. The seal holding ring 55 is filled around the projection 56 with sealing material 54 which closes off the space inside the base pile 2 with respect to the environment. In addition the head cover 50 is screwed to the base pile 2 by means of screws 53. The screws 53 are also sealed off with sealing material 54 which is supported by a second seal holding ring 55. Sealing rings 51 are further arranged between the head cover 50 and the base pile 2 for additional safeguard purposes. That therefore affords air-tight closure of the space inside the base pile 2 with respect to the environment, which can outlast the entire service life of the base structure and which permanently closes off the space inside the base pile 2 in relation to exchange of air with the environment.

FIG. 6 shows a full section of a base pile 402. Identical or similar reference numerals are denoted by reference numerals increased by 400, in that respect reference is directed in its entirety to the foregoing description. The base pile 402 is in the form of a sandwich pile and has an inner tube forming the inner layer 419 and an outer tube forming the outer layer 420. A respective sandwich connection 450a, 450b is arranged at each of the axial ends of the inner and outer tubes 419, 420 respectively. The sandwich connection 450a, 450b has a ring flange 452a, 452b which is shaped conically in cross-section and which connects the inner and outer tubes 419, 420 together. On the other side the ring flange 452a, 452b is connected with a tube connection 451a, 451b which is in the form of a solid tube. Arranged in the intermediate space between the tubes 419, 420 are reinforcing bars 433 which extend along the longitudinal axis and which extend through openings in the ring flanges 452a, 452b. Those reinforcing bars 433 are also connected to the connecting tubes 451a, 451b.

The base pile 402 is placed on the seabed 10. Arranged in the interior of the base pile 402 is a driving pile 411 which has a bulkhead 428 in the proximity of its head end, and two air vent openings 432 arranged under the bulkhead 428. The upper region of the driving pile 411 is filled with concrete 430a. Preferably the concrete 430a is introduced to a height which approximately corresponds to twice the diameter of the driving pile 411. Concrete 430b is also introduced in the intermediate space between the driving pile 411 and the base pile 402 in order to form a fixed solid connection between the two piles 402, 411.

Claims

1. A base structure for an off-shore wind power installation having at least a plurality of base piles wherein each base pile (2, 3, 4) has a driving pile which is guided in its interior at least portion-wise for anchoring in the seabed, and at least one support structure for mounting a pylon of a wind power installation, wherein the support structure connects the upper ends of the base piles together,

characterised in that the base pile (2, 3, 4) and the driving pile (11, 12, 13) have a region of an overlap on a predetermined lengthwise portion, wherein in the overlap region (25) of the piles the gap (29) between the piles and in a part beneath and above the overlap region (25) the free internal cross-section of the piles (2, 3, 4, 11, 12, 13) are filled with a hardening filling material (30).

2. A base structure as set forth in claim 1 characterised in that the base pile (2 through 4) has a bottom ring (26), preferably with a seal which seals off the gap (29) relative to the driving pile (11, 12, 13).

3. A base structure as set forth in one of claims 1 and 2 characterised in that the base pile (2 through 4) has an inner tube providing its inner peripheral surface and an outer tube providing its outer peripheral surface, wherein a core material is arranged between the inner tube and the outer tube.

4. A base structure as set forth in one of claims 1 through 3 characterised in that the driving pile (11 through 13) has a bulkhead (28) which is arranged at a spacing beneath the overlap region (25) and which closes off the free internal cross-section of the driving pile (11, 12, 13).

5. A base structure as set forth in claim 4 characterised in that the driving pile (11 through 13) in its pile wall beneath the bulkhead (28) has at least one opening (32) for air venting.

6. A base structure as set forth in one of claims 2 through 5 characterised in that the bottom ring (26) extends radially beyond the base pile (2, 3, 4) and is connected thereto by support struts (34).

7. A base structure as set forth in one of claims 1 through 6 characterised in that the driving pile (11 through 13) is provided at least portion-wise on the inside of the pile wall with reinforcement (31).

8. A method of erecting a base structure for an off-shore wind power installation, in which a plurality of and preferably three base piles (2, 3, 4) provided with driving piles (11, 12, 13) are pre-assembled with at least one support structure (5, 15) comprising bars (6, 7, 8, 16, 17, 18) to form a construction part, the pre-assembled construction part is transported to the installation location and placed with its base piles (2 through 4) leading on the seabed (10), than the driving piles (11 through 13) are driven into the seabed (10) and a base portion anchored in the seabed (10) is produced,

characterised in that finally a hardening filling material (30) is introduced into the base portion into at least the overlap region (25) of the piles and a portion above and below the overlap region and thus a solid base structure (1) is formed.

9. A method as set forth in the classifying portion of claim 8 or as set forth in claim 8 characterised by the step:

aligning the base portion in such a way that a central axis of a central mounting (9) for mounting the pylon of a wind power installation is oriented substantially vertically,

wherein a filling material (30) is introduced preferably after the alignment operation.

10. A method as set forth in claim 9 characterised in that the alignment operation includes:

displacing at least one, preferably two of the three, base piles (2, 3, 4) relative to the driving pile (11, 12, 13) by means of an aligning ram (100) arranged completely within and/or above the base pile (2, 3, 4).

11. A method in particular as set forth in claim 10 or at least one of preceding claims 9 through 11 and further including the steps:

introducing the aligning ram (100) from an upper end of the base pile (2, 3, 4), which is above the surface of the sea, into the base pile (2, 3, 4),

contacting a ram head (106) of the aligning ram (100) with the driving pile (11, 12, 13),

bringing a support device (105) of the aligning ram (100) into engagement with the base pile (2, 3, 4), and

extending a portion of the aligning ram (100) to displace the base pile (2, 3, 4) relative to the driving pile (11, 12, 13).

12. A method as set forth in claim 11 characterised in that extension of the aligning ram (100) is effected hydraulically.

13. A method as set forth in one of claims 11 and 12 and further including the step:

introducing filling material (30) through a passage (112) in the aligning ram (100) into the driving pile (11, 12, 13) and/or the overlap region.

14. A method as set forth in one of claims 8 through 13 characterised by the step:

closing, preferably air-tightly sealing, the upper open end of at least one base pile (2, 3, 4) by means of a closure device (150).

15. An aligning tool including

an aligning ram (100) with a ram tube (118), a ram head (106) connected to the ram tube for coming into contact with a driving pile (11, 12, 13), and a support device (105) for supporting a base pile (2, 3, 4).