Method for installing offshore wind turbine foundation single pile

Abstract

Offshore wind turbine foundation monolith in the seabed, the monolith having a foot end, a top end and a longitudinal axis, by rotating the monolith about the longitudinal axis, causing the monolith to rotate a plurality of times when driven into the seabed.

Description

Technical Field

[0001] The present invention relates to the field of installing an offshore wind turbine foundation monolithic pile, i.e. a hollow tubular pile with a vertical centerline, a top end and an open foot end, vertically into soil, such as the seabed. For example, the pile is a larger diameter pile with an outer diameter of at least 5 meters at the open foot end. For example, the pile is a so-called monolithic pile of an offshore wind turbine. Background Art

[0002] Practical embodiments of monolithic piles currently envisioned include monolithic piles having a diameter between 5 and 12 meters and a length between 60 and 120 meters. In embodiments, the wall thickness of the pile is greater than 10 centimeters. For example, the pile may have a mass greater than 1000 tons, such as greater than 2000 tons, or even greater than 3000 tons.

[0003] In a practical embodiment, the pile is a steel pile, for example consisting of ring segments welded end to end, each ring segment consisting of arc segments welded to each other to form a ring.

[0004] The pile may comprise, for example, a tapered or conical section between a lower pile section of larger diameter and a pile top section of smaller diameter. In another embodiment, the pile has a uniform cross section over its length. Preferably, the pile has a circular horizontal cross section over its entire length. In an embodiment, the top end of the pile is provided with a connection structure for a wind turbine tower, possibly with an interface for a transition piece, such as a flange for bolting and / or a sliding joint connection structure.

[0005] Vibratory pile hammers are well known. They typically include a system of counter-rotating eccentric counterweights driven by a hydraulic motor. Vibratory pile hammers are designed so that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. The vibratory pile hammer is positioned above the pile by an excavator or crane and is fastened to the pile by clamps and / or bolts. The vibratory hammer can drive in or out of the pile. The extraction is typically used to recover I-beams used in temporary foundation support. Hydraulic fluid is supplied to the pile driver, for example, by a pump driven by a diesel engine mounted in a trailer or truck, and is connected to the pile driver head via a hose. When the pile driver is connected to a dragline excavator, the pile driver is driven by the excavator's diesel engine. Vibratory pile drivers are typically selected to mitigate noise when the building is close to a residential or office building, or when there is not enough vertical clearance to allow the use of a conventional pile hammer (for example, when retrofitting an additional pile to a bridge column or abutment footing). The hammer can have several different vibration rates, ranging from 1200 vibrations per minute to 2400 vibrations per minute. The vibration rate selected is influenced by soil conditions and other factors such as power requirements and equipment cost. Summary of the invention

[0006] The present invention relates to a method for driving a hollow tubular pile having a vertical centerline, a top end and an open foot end (e.g., a larger diameter pile having an outer diameter of at least 5 meters at the open foot end, such as a monolithic pile of an offshore wind turbine) vertically into soil (e.g., into the seabed). The present invention also provides a monolithic pile, a system for driving a monolithic pile into the seabed, a vessel provided with such a system, and a template.

[0007] For example, it is known from WO2020 / 207903 to use a vibration force directed along the longitudinal axis of the monolithic pile to drive the monolithic pile into the soil. In addition to the vibration driving force, water can be used to remove soil from under the foundation pile. Furthermore, it is known from WO2017 / 203023 to push the soil away from under the monolithic pile in a radially outward direction. The installation process of these prior art requires a complex device to be provided at the foot end of the monolithic pile. At the end of the installation process, the device must be excavated so that it can be used to install another foundation pile. The excavation of such a complex device is difficult and time-consuming.

[0008] It is an object of the present invention to provide an improved and more particularly a more efficient monolithic pile installation process.

[0009] According to the present invention, the monolithic pile is rotated about the longitudinal axis of the monolithic pile, ie about the vertical center line of the hollow tubular pile, so that the monolithic pile is rotated multiple times during the installation process of the monolithic pile.

[0010] The monolithic pile installation process is a process of driving a monolithic pile vertically into the seabed. The pile driving force, i.e., the force driving the pile into the seabed in the axial direction, can be generated by a vibration device, an impact hammer, a pile rotator in combination with one or more spiral ribs and / or excavation blades installed on the monolithic pile.

[0011] According to the invention, during the installation process, ie during the installation process of the monolithic pile, the monolithic pile rotates about the longitudinal axis of the monolithic pile.

[0012] A method according to claim 1 for installing an offshore wind turbine foundation monolithic pile into a seabed, the monolithic pile having a foot end, a top end and a longitudinal axis, the method comprising:

[0013] - supporting the monolithic pile in an upright position with the foot end resting on the seafloor;

[0014] - Rotating the monolithic pile about its longitudinal axis so that the monolithic pile performs multiple rotations when driven into the seabed.

[0015] Rotating the entire monolithic pile rather than, for example, vibrating the monolithic pile in a circumferential direction so that the monolithic pile performs multiple rotations while being driven into the seabed enables an improved and, more particularly, more efficient installation process.

[0016] Vibration is a type of motion in which an object moves in one direction and then moves approximately the same distance in the opposite direction.

[0017] Rotating the monolithic pile on its own during installation may result in the removal of soil beneath the foot end of the monolithic pile. This is particularly true when the monolithic pile is provided with a digging blade at the foot end of the monolithic pile.

[0018] Rotating the monolithic pile during installation can generate a piling force, i.e. a force in the axial direction of the monolithic pile. This is particularly true when the monolithic pile is provided with one or more spiral ribs on its inner and / or outer surface, the one or more spiral ribs forming a thread that engages the soil, thereby converting a circumferential force into an axial force.

[0019] Rotating the monolithic pile during installation can reduce friction between the monolithic pile and the soil. This is especially true when a vibrating device is used to rotate the monolithic pile.

[0020] In an embodiment, the method according to the invention further comprises pressing the monolithic pile into the soil using gravity, for example by providing a counterweight at the top of the monolithic pile, for example by installing a ballast tank at the top of the monolithic pile.

[0021] In an embodiment, the method according to the present invention further comprises fluidizing the soil by injecting water into the soil at the foot end of the monolithic pile, and allowing the fluidized soil to flow away from under the monolithic pile.

[0022] In an embodiment, the method according to the invention further comprises vibrating the monolithic pile in a circumferential direction.

[0023] In an embodiment, the method according to the invention further comprises vibrating the monolithic pile in an axial direction.

[0024] In an embodiment, in another method according to the invention, the frequency of the vibration is between 10 and 500 Hz.

[0025] In an embodiment, in another method according to the present invention, three or more vibration devices are used to provide the vibration, and wherein the vibration devices vibrate asynchronously, thus generating peaks (in phase and out of phase).

[0026] Vibration is a motion in which an object moves in one direction and then moves approximately the same distance in the opposite direction. The vibration device according to the present invention is configured to move the object a relatively large distance in a first direction and a relatively small distance in an opposite second direction, so that the object as a whole moves in the first direction.

[0027] The vibration device usually comprises a counter-rotating eccentric weight system driven by a hydraulic motor. In order to rotate the monolithic pile around a vertical axis, the vibration device is designed so that the vertical vibrations cancel out, while the horizontal vibrations are transmitted into the pile. According to the invention, a plurality of vibration devices are set up along the periphery of the pile to be rotated, preferably each vibration device generates a pile rotation force.

[0028] In an embodiment, in another method according to the invention, the vibration device engages the outer surface of the foundation pile and / or is mounted to the pile at the top end.

[0029] In an embodiment, in another method according to the invention, a plurality of vibrating devices are adjusted such that they produce an interference pattern including a peak producing a net circumferential displacement in the direction of rotation, thereby causing the monolithic post to rotate about the longitudinal axis of the monolithic post.

[0030] In another method according to the invention, in an embodiment, vibration is achieved by using a plurality of individual vibration devices, each of which comprises a hydraulic motor connected to a rotating eccentric mass.

[0031] In an embodiment, in a further method according to the invention, the axis of rotation of the eccentric mass is directed in a radial direction relative to the monolithic pile, so that the vibration device can generate circumferentially directed vibration forces.

[0032] In an embodiment, the vibration device according to the present invention comprises a plurality of rotating eccentric masses. The vibration device is configured so that vertical vibrations cancel, while horizontal vibrations perpendicular to a plane including the central axis of the foundation pile are transmitted into the pile. In addition, the vibration device is adjusted, i.e., the rotating eccentric weights of the vibration device are set up so as to produce an interference pattern, which includes a peak value that produces a net circumferential displacement in the direction of rotation. Therefore, the vibration device is adjusted so that it produces a net circumferential displacement in the direction of rotation.

[0033] The present invention also provides a method for installing an offshore wind turbine foundation monolithic pile into a seabed, the monolithic pile having a foot end, a top end and a longitudinal axis, wherein the method comprises:

[0034] - supporting the monolithic pile in an upright position with the foot end resting on the seafloor;

[0035] - rotating the monolithic pile about its longitudinal axis by vibrating the monolithic pile in a circumferential direction, so that the monolithic pile performs a plurality of rotations when being driven into the seabed,

[0036] wherein three or more vibration devices are used to provide the vibrations, and wherein the vibration devices vibrate asynchronously so as to produce peaks (in phase and out of phase), and

[0037] Preferably, the monolithic pile is provided with an excavating blade at the foot end for removing soil from underneath the foundation pile, and / or the monolithic pile is provided with one or more spiral ribs at the inner surface and / or outer surface for providing threads on the corresponding inner surface and / or outer surface of the monolithic pile, so that the monolithic pile can be screwed into the seabed and / or soil is removed in an axial direction away from the foot end of the monolithic pile.

[0038] Preferably, the method further comprises pressing the monolithic pile into the soil using gravity, for example by providing a counterweight at the top of the monolithic pile, for example by installing a ballast water tank at the top of the monolithic pile, and / or the method further comprises fluidizing the soil by injecting water into the soil at the foot end of the monolithic pile, and allowing the fluidized soil to flow away from under the monolithic pile.

[0039] When the monolithic pile is driven into the seabed, the monolithic pile is rotated about the longitudinal axis by vibrating the monolithic pile in the circumferential direction, so that the monolithic pile rotates multiple times. The monolithic pile is preferably supported by a pile holder installed on a vessel or a template installed on the seabed.

[0040] The present invention also provides a method for installing an offshore wind turbine foundation monolithic pile into a seabed, the monolithic pile having a foot end, a top end and a longitudinal axis, wherein the method comprises:

[0041] - supporting the monolithic pile in an upright position with the foot end resting on the seafloor;

[0042] - rotating the monolithic pile about its longitudinal axis by vibrating the monolithic pile in a circumferential direction, so that the monolithic pile performs multiple rotations when being driven into the seabed,

[0043] wherein the vibration is achieved by using a plurality of separate vibration devices, each vibration device comprising a hydraulic motor connected to a rotating eccentric mass, and wherein the plurality of vibration devices are adjusted so that they produce an interference pattern including peaks that produce a net circumferential displacement in the direction of rotation, thereby causing the monolithic pile to rotate about the longitudinal axis of the monolithic pile, and

[0044] Preferably, the monolithic pile is provided with an excavating blade at the foot end for removing soil from underneath the foundation pile, and / or the monolithic pile is provided with one or more spiral ribs at the inner surface and / or outer surface for providing threads on the corresponding inner surface and / or outer surface of the monolithic pile, so that the monolithic pile can be screwed into the seabed and / or soil is removed in an axial direction away from the foot end of the monolithic pile.

[0045] Preferably, the method further comprises pressing the monolithic pile into the soil using gravity, for example by providing a counterweight at the top of the monolithic pile, for example by installing a ballast water tank at the top of the monolithic pile, and / or the method further comprises fluidizing the soil by injecting water into the soil at the foot end of the monolithic pile, and allowing the fluidized soil to flow away from under the monolithic pile.

[0046] When the monolithic pile is driven into the seabed, the monolithic pile is rotated about the longitudinal axis by vibrating the monolithic pile in the circumferential direction, so that the monolithic pile rotates multiple times. The monolithic pile is preferably supported by a pile holder installed on a vessel or a template installed on the seabed.

[0047] The present invention also provides a monolithic pile column for an offshore wind turbine foundation, the monolithic pile column having a foot end, a top end and a longitudinal axis, wherein the monolithic pile column is configured to rotate about the longitudinal axis of the monolithic pile column during installation of the monolithic pile column in the seabed, wherein:

[0048] - the monolithic pile is provided with a digging blade at the foot end for removing soil from underneath the foundation pile, and / or wherein the monolithic pile is provided with one or more spiral ribs at the inner surface and / or outer surface for providing threads to the respective inner surface and / or outer surface of the monolithic pile so that the monolithic pile can be screwed into the seabed and / or soil is removed in an axial direction away from the foot end of the monolithic pile;

[0049] and / or

[0050] - the monolithic pile is provided with one or more fluidizing ducts extending in the longitudinal direction of the monolithic pile for guiding a fluidizing fluid, such as water, to the foot end of the monolithic pile, and preferably a plurality of fluidizing fluid nozzles are provided along the periphery of the foot end of the monolithic pile, the plurality of fluidizing fluid nozzles being used to distribute a jet of the fluidizing fluid at the foot end of the monolithic pile during installation of the monolithic pile;

[0051] and / or

[0052] - the monolithic stud is configured to be engaged by a stud rotator, for example the monolithic stud is provided with radially extending teeth to cooperate with drive teeth of a stud rotator and / or the monolithic stud is provided with a seat for one or more vibration devices at the top end of the monolithic stud.

[0053] In another embodiment, the monolithic pile has a diameter of at least 8 meters, for example a diameter of 10 meters, preferably a diameter of 12 meters.

[0054] In another embodiment, the monolithic pile has a length of at least 30 meters, for example a length of more than 40 meters.

[0055] In another embodiment, the monolithic pile is provided with a plurality of digging blades at the foot end, the digging blades being mounted to the bottom surface or flange of the monolithic pile, the flange being mounted to the bottom end of the monolithic pile, wherein the digging blades extend at an angle to the outer periphery of the monolithic pile to force the soil away from below the monolithic pile in a radial direction.

[0056] In another embodiment, the excavating blades extend alternately inwardly and outwardly relative to the periphery of the monolithic pile so that soil is pushed inwardly and outwardly during installation.

[0057] The present invention also provides a monolithic pile column for an offshore wind turbine foundation, the monolithic pile column having a foot end, a top end and a longitudinal axis, wherein the monolithic pile column is configured to rotate about the longitudinal axis of the monolithic pile column during installation of the monolithic pile column in the seabed, wherein:

[0058] - the monolithic pile is provided with an excavating blade at the foot end for removing soil from underneath the foundation pile, and / or wherein the monolithic pile is provided with one or more spiral ribs at the inner surface and / or outer surface for providing threads on the corresponding inner surface and / or outer surface of the monolithic pile, so that the monolithic pile can be screwed into the seabed and / or soil is removed in an axial direction away from the foot end of the monolithic pile.

[0059] The present invention also provides a single pile installation system, the system comprising:

[0060] - a monolithic pile support for supporting a monolithic pile in an upright position, wherein the foot end of the monolithic pile is located on the seabed, such as a pile holder mounted on a vessel or a template mounted on the seabed;

[0061] - a monolithic pile rotator for rotating a monolithic pile about a central axis during installation of the monolithic pile, wherein, for example, the monolithic pile driver comprises a plurality of vibration devices mounted on a top end of the monolithic pile or on one or more drivers configured to engage an outer surface of the monolithic pile and exert a circumferential pile rotation force on the outer surface.

[0062] In another embodiment, the mounting system further comprises:

[0063] A pile driver for generating an axial pile driving force, such as a hydraulic impact hammer or one or more vibrating devices.

[0064] In another embodiment, the mounting system further comprises a monolithic pile according to the present invention.

[0065] The present invention also provides a single pile installation system, the system comprising:

[0066] - a monolithic pile support for supporting a monolithic pile in an upright position, wherein the foot end of the monolithic pile is located on the seabed, such as a pile holder mounted on a vessel or a template mounted on the seabed;

[0067] - a monolithic pile rotator for rotating the monolithic pile around a central axis during installation of the monolithic pile, wherein the pile rotator comprises a plurality of vibration devices mounted on a top end of the monolithic pile for rotating the monolithic pile around a longitudinal axis by vibrating the monolithic pile in a circumferential direction, and wherein the plurality of vibration devices are adjusted so that they generate an interference pattern including a peak value for generating a net circumferential displacement in the rotation direction, thereby rotating the monolithic pile around the longitudinal axis of the monolithic pile.

[0068] The present invention also provides a single pile installation system, the system comprising:

[0069] - a monolithic pile support for supporting a monolithic pile in an upright position, wherein the foot end of the monolithic pile is located on the seabed, such as a pile holder mounted on a vessel or a template mounted on the seabed;

[0070] - a monolithic pile rotator for rotating the monolithic pile around a central axis during installation of the monolithic pile, wherein the monolithic pile rotator comprises a plurality of vibration devices mounted on a top end of the monolithic pile for rotating the monolithic pile around a longitudinal axis by vibrating the monolithic pile in a circumferential direction, and wherein the plurality of vibration devices are adjusted so that they generate an interference pattern including a peak value generating a net circumferential displacement in the rotation direction, thereby rotating the monolithic pile around the longitudinal axis of the monolithic pile.

[0071] - an offshore wind turbine foundation monolithic pile, the monolithic pile having a foot end, a top end and a longitudinal axis, wherein the monolithic pile is configured to rotate about the longitudinal axis of the monolithic pile during installation of the monolithic pile in the seabed, wherein

[0072] - the monolithic pile is provided with a digging blade at the foot end for removing soil from underneath the foundation pile, and / or wherein the monolithic pile is provided with one or more spiral ribs at the inner surface and / or outer surface for providing threads to the respective inner surface and / or outer surface of the monolithic pile so that the monolithic pile can be screwed into the seabed and / or soil is removed in an axial direction away from the foot end of the monolithic pile;

[0073] and / or

[0074] - the monolithic pile is provided with one or more fluidizing ducts extending in the longitudinal direction of the monolithic pile for guiding a fluidizing fluid, such as water, to the foot end of the monolithic pile, and preferably a plurality of fluidizing fluid nozzles are provided along the periphery of the foot end of the monolithic pile, the plurality of fluidizing fluid nozzles being used to distribute a jet of the fluidizing fluid at the foot end of the monolithic pile during installation of the monolithic pile;

[0075] and / or

[0076] - the monolithic pile is configured to be engaged by a pile rotator for rotating the monolithic pile around a central axis during installation of the monolithic pile, wherein the pile rotator comprises a plurality of vibration devices mounted on a top end of the monolithic pile for rotating the monolithic pile around a longitudinal axis by vibrating the monolithic pile in a circumferential direction, and wherein the plurality of vibration devices are adjusted so that they generate an interference pattern including a peak value that generates a net circumferential displacement in the rotation direction, thereby rotating the monolithic pile around the longitudinal axis of the monolithic pile.

[0077] The present invention also provides a template configured to support a monolithic pile in an upright position and / or provided with a monolithic pile rotator for rotating the monolithic pile about a longitudinal axis during installation of the monolithic pile.

[0078] In another embodiment, the template is mounted on the sea floor to support the monolithic pile in an upright position and / or to support pile rotation means.

[0079] The invention also provides a vessel, such as a jack-up vessel, provided with a system according to the invention.

[0080] The present invention also provides a single-body pile rotator, which is installed on the top of a single-body pile for an offshore wind turbine, and is used to rotate the single-body pile around the central axis of the single-body pile during the installation of the single-body pile, wherein the single-body pile rotator includes a plurality of vibration devices, and the plurality of vibration devices are adjusted so that the plurality of vibration devices generate interference patterns, and the interference patterns include peak values ​​of net circumferential displacement generated in the rotation direction, thereby causing the single-body pile to rotate around the longitudinal axis of the single-body pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Other objects, embodiments and details of the monolithic pile and method according to the present invention will become apparent from the following description, wherein the present invention is further illustrated and explained based on a number of exemplary embodiments with reference to the accompanying drawings.

[0082] In the accompanying drawings,

[0083] Figure 1 A side view showing a cross section of a monolithic pile according to the present invention, the monolithic pile being provided with a plurality of vibrating devices at its top end;

[0084] Figure 2 Shows Figure 1 Bottom view of a single pile column;

[0085] Figure 3 a partial cross-sectional side view showing a close-up of the monolithic pile of claim 1;

[0086] Figure 4 A partial bottom view showing a close-up of the monolithic pile of claim 1;

[0087] Figure 5 shows the interference pattern of the vibrating device which results in periodic peaks in the torsional force exerted on the monolithic pile;

[0088] Figure 6 An interference pattern of a vibrating device is shown, which interference pattern causes periodic peaks in the torsional force exerted on the monolithic pile, which causes the monolithic pile to rotate;

[0089] Figure 7 A perspective view of another monolithic pile according to the present invention is shown, the monolithic pile having a plurality of vibration devices disposed at its top end and a yoke for supporting the monolithic pile;

[0090] Figure 8 Shown in Figure 7 A close-up of the multiple vibrating devices at the top of the monolithic pile; and

[0091] Fig. 9 The interference pattern of the vibrating device is shown, which results in periodic peaks in the torsional force exerted on the monolithic pile. DETAILED DESCRIPTION

[0092] Figure 1 The side view of a cross section of a monolithic pile 1 according to the invention is shown. The monolithic pile 1 is provided with a plurality of vibrating devices 2 at its top end 3. In the embodiment shown, four vibrating devices are provided, three of which are located at the top of the pile 1. Figure 1 In the embodiment shown, the rotation axis 7 of the eccentric mass 8 is directed in radial direction relative to the monolithic pile, so that the vibration device can generate circumferentially directed vibration forces.

[0093] The vibrations are provided by four vibration devices 2, wherein the vibration devices vibrate asynchronously, thus producing peaks (in phase and out of phase).

[0094] The plurality of vibrating devices 2 are adjusted such that they generate an interference pattern comprising peaks producing a net circumferential displacement in the direction of rotation, thereby causing the monolithic stud 1 to rotate about the longitudinal axis 10 of the monolithic stud 1 .

[0095] Figure 2 Shows Figure 1 Bottom view of the single pile column. Figure 4 A close-up of the bottom end is shown, depicting a plurality of digging blades 4. The digging blades 4 extend alternately inwardly and outwardly relative to the periphery of the monolithic pile 1, so that soil is pushed inwardly and outwardly during installation. Thus, rotating the monolithic pile on itself during installation enables soil beneath the foot end of the monolithic pile to be removed.

[0096] Figure 3 A close-up, partially sectional side view of the monolithic pile of claim 1 is shown, depicting the excavating blade 4 and a portion of the fluidizing conduit 5. Only a portion of the fluidizing conduit is shown. The fluidizing conduit 5 extends in the longitudinal direction of the monolithic pile and is used to guide a fluidizing fluid, such as water, to the foot end of the monolithic pile. In the preferred embodiment shown, a plurality of fluidizing fluid nozzles 6 are provided along the periphery of the foot end of the monolithic pile for distributing a jet of the fluidizing fluid at the foot end of the monolithic pile during installation of the monolithic pile, see Figure 4 .

[0097] Therefore, in the preferred embodiment shown, the monolithic pile 1 has a foot end 9, a top end 3 and a longitudinal axis 10, wherein the monolithic pile is configured to rotate around the longitudinal axis of the monolithic pile during installation of the monolithic pile in the seabed, and the monolithic pile is provided with an excavation blade 4 at the foot end for removing soil from under the foundation pile.

[0098] Furthermore, the monolithic pile 1 is provided with a fluidizing conduit 5 extending in the longitudinal direction of the monolithic pile for guiding a fluidizing fluid, such as water, to a foot end 9 of the monolithic pile, and a plurality of fluidizing fluid nozzles 6 are provided along the periphery of the foot end 9 of the monolithic pile for distributing a jet flow of the fluidizing fluid at the foot end of the monolithic pile during installation of the monolithic pile.

[0099] Furthermore, the monolithic pile 1 is configured to be engaged by a pile rotator 11. In the illustrated embodiment, the pile rotator 11 comprises a plurality of vibrating devices 2 located at the top of the monolithic pile. The plurality of vibrating devices are adjusted so that they produce an interference pattern including peaks that produce a net circumferential displacement in the direction of rotation, thereby causing the monolithic pile to rotate about the longitudinal axis of the monolithic pile. Figure 5 An example of such an interference pattern is shown in .

[0100] Figure 7 Another monolithic pile 21 provided with a pile rotator 31 is shown.

[0101] The monolithic pile extends along a central axis between a top end 23 and a bottom end 29. The monolithic pile 21 is provided with a plurality of spiral ribs 33 at the outer surface so as to provide a thread to the outer surface of the monolithic pile so that the monolithic pile can be screwed into the seabed. In the embodiment shown, the monolithic pile is provided with two spiral ribs intertwined with each other. In alternative embodiments, the foundation pile can be provided with a single spiral rib, or with three or more intertwined spiral ribs.

[0102] The monolithic pile 21 is engaged at its top end by a pile rotator 31. The pile rotator 31 comprises four vibrating devices 22 set up in an annular frame. The pile rotator 31 is also provided with a clamping device 34 on the bottom side for engaging the top end of the foundation pile to secure the pile rotator to the pile. The pile rotator is also provided with a yoke 32 for lifting the pile rotator using a crane and for supporting the monolithic pile in an upright position when the pile rotator is clamped on the top end of the monolithic pile. It is proposed that the yoke is preferably configured so that the pile rotator and therefore the foundation pile can be rotated relative to the hook of the crane supporting the pile rotator. Therefore, during installation, i.e., when the foundation pile is screwed into the seabed, in addition to or as an alternative to the pile holder or base plate, the crane can be used to support the foundation pile.

[0103] In a preferred embodiment, the vibrating device and the gripping device of the pile rotator are hydraulically operated. In another embodiment, the hydraulic power source is connected to the pile rotator via pipes, which enable the power source to be set up, for example, on a vessel adjacent to the foundation pile on which the pile rotator is arranged.

[0104] It is proposed that, before the pile rotator starts to rotate the pile, the weight of the monolithic pile forces its bottom end into the seabed, thereby forcing the spiral ribs to engage the seabed.

[0105] In order to screw the pile into the seabed, a pile rotator 31 is used to rotate the monolithic pile around its longitudinal axis. The rotation of the pile combines with the spiral ribs that engage the seabed, similar to a screw forcing the pile into the seabed. Therefore, the monolithic pile performs multiple rotations when being driven into the seabed.

[0106] In the embodiment shown, the pile rotator is provided with four individual vibrating devices 22, which are set up along the periphery of the annular frame of the pile rotator. The vibrating devices 22 are adjusted so that they produce an interference pattern including peaks that produce a net circumferential displacement in the direction of rotation, thereby causing the monolithic pile 1 to rotate about the longitudinal axis 10 of the monolithic pile 1.

[0107] Figure 5 The interference pattern of the vibration device is shown. The figure shows the output of the torsional force generated by two vibration devices vibrating asynchronously, and their combined output.

[0108] Fig. 9 The interference pattern of the vibration device is shown. The figure shows the output of the torsional force generated by the four rotating eccentric weights, levels 1-4, and the combined output, level 5. In this figure, the combined output shows two main peaks of torsional force, which produces a net circumferential displacement in the direction of rotation, thus rotating the monolithic pile 1 about its longitudinal axis in the direction of rotation.

[0109] exist Fig. 9 In FIG, two main peaks of torsional force are shown, i.e., two pile rotation forces.

[0110] Figure 6 Another alternative interference pattern of the vibrating devices is shown. In this configuration, the vibrating devices combine to produce a sawtooth cycle with a predominantly torsional force in one direction which causes the monolithic pile to self-rotate.

Claims

1. A method for installing an offshore wind turbine foundation monolithic pile into a seabed, the monolithic pile having a foot end, a top end and a longitudinal axis, the method comprising: - supporting the monolithic pile in an upright position with the foot end resting on the seafloor; - Rotating the monolithic pile about its longitudinal axis so that the monolithic pile performs multiple rotations when driven into the seabed.

2. The method according to claim 1, wherein: The method further includes pressing the monolithic pile into the soil using gravity, for example by providing a counterweight at the top of the monolithic pile, for example by installing a ballast tank at the top of the monolithic pile.

3. The method according to claim 1 or 2, wherein: The method further includes fluidizing the soil by injecting water into the soil at the foot end of the monolithic pile, and allowing the fluidized soil to flow away from under the monolithic pile.

4. The method according to one or more of the preceding claims, wherein: The method further includes vibrating the monolithic pile in an axial direction.

5. The method according to one or more of the preceding claims, wherein: The method further includes vibrating the monolithic pile in a circumferential direction.

6. The method according to claim 5, wherein: The frequency of the vibration is between 10 Hz and 500 Hz.

7. The method according to claim 5 or 6, wherein: Three or more vibration devices are used to provide the vibrations, and the vibration devices vibrate asynchronously, thereby generating peak values ​​(in phase and out of phase).

8. The method according to any one of claims 5 to 7, wherein: The vibrating device engages the outer surface of the foundation pile and / or is mounted to the pile at the top end.

9. The method according to any one of claims 5 to 8, wherein: The plurality of vibrating devices are adjusted such that the plurality of vibrating devices produce an interference pattern including a peak that produces a net circumferential displacement in the direction of rotation, thereby causing the monolithic post to rotate about a longitudinal axis of the monolithic post.

10. The method according to any one of claims 5 to 9, wherein: The vibration is achieved by using a plurality of separate vibration devices, each comprising a hydraulic motor connected to a rotating eccentric mass.

11. The method according to any one of claims 5 to 10, wherein: The rotation axis of the eccentric mass is directed in a radial direction relative to the monolithic pile, so that the vibration device can generate a circumferentially directed vibration force.

12. A monolithic pile column for an offshore wind turbine foundation, the monolithic pile column having a foot end, a top end and a longitudinal axis, wherein: The monolithic pile is configured to rotate about a longitudinal axis of the monolithic pile during installation of the monolithic pile in the seabed, wherein - the monolithic pile is provided with a digging blade at the foot end for removing soil from underneath the foundation pile, and / or wherein the monolithic pile is provided with one or more spiral ribs at the inner surface and / or outer surface for providing threads to the respective inner surface and / or outer surface of the monolithic pile so that the monolithic pile can be screwed into the seabed and / or soil is removed in an axial direction away from the foot end of the monolithic pile; and / or - the monolithic pile is provided with one or more fluidizing ducts extending in the longitudinal direction of the monolithic pile for guiding a fluidizing fluid, such as water, to the foot end of the monolithic pile, and preferably a plurality of fluidizing fluid nozzles are provided along the periphery of the foot end of the monolithic pile, the plurality of fluidizing fluid nozzles being used to distribute a jet of the fluidizing fluid at the foot end of the monolithic pile during installation of the monolithic pile; and / or - the monolithic stud is configured to be engaged by a stud rotator, for example the monolithic stud is provided with radially extending teeth to cooperate with drive teeth of a stud rotator and / or the monolithic stud is provided with a seat for one or more vibration devices at the top end of the monolithic stud.

13. The monolithic pile according to claim 12, wherein: The monolithic pile has a diameter of at least 8 meters, for example a diameter of 10 meters, preferably a diameter of 12 meters.

14. The monolithic pile according to claim 12 or 13, wherein: The monolithic pile has a length of at least 30 meters, for example a length of more than 40 meters.

15. A monolithic pile according to any one of claims 12 to 14, wherein: The monolithic pile is provided with a plurality of digging blades at the foot end, the digging blades being mounted to the bottom surface or flange of the monolithic pile, the flange being mounted to the bottom end of the monolithic pile, wherein the digging blades extend at an angle to the outer periphery of the monolithic pile to force the soil away from below the monolithic pile in a radial direction.

16. A monolithic pile according to any one of claims 12 to 15, wherein: The excavating blades extend alternately inwardly and outwardly relative to the periphery of the monolithic pile so that soil is pushed inwardly and outwardly during installation.

17. A single pile installation system, the system comprising: - a monolithic pile support for supporting a monolithic pile in an upright position, wherein the foot end of the monolithic pile is located on the seabed, such as a pile holder mounted on a vessel or a template mounted on the seabed; - a monolithic pile rotator for rotating the monolithic pile around a central axis during installation of the monolithic pile, wherein, for example, the monolithic pile rotator comprises a plurality of vibration devices mounted on a top end of the monolithic pile or on one or more rotators, the one or more rotators being configured to engage an outer surface of the monolithic pile and exert a circumferential pile rotation force on the outer surface.

18. The system of claim 17, wherein: The mounting system further comprises: A pile driver for generating an axial pile driving force, such as a hydraulic impact hammer or one or more vibration devices.

19. The system according to claim 17 or 18, wherein: The mounting system further comprises a monolithic pile according to one or more of claims 12 to 16 .

20. A template configured to support a monolithic pile in an upright position and / or provided with a monolithic pile rotator for rotating the monolithic pile about a longitudinal axis during installation of the monolithic pile.

21. The base plate according to claim 20, wherein: A template is provided which is mounted on the sea floor to support the monolithic pile in an upright position and / or to support the pile rotation means.

22. A vessel, such as a jack-up vessel, provided with a system according to any one of claims 17 to 19.

23. A monolithic pile rotator, mounted on a top end of a monolithic pile for an offshore wind turbine, for rotating the monolithic pile around a central axis of the monolithic pile during installation of the monolithic pile, wherein: The single pile rotator comprises a plurality of vibration devices, The plurality of vibrating devices are adjusted such that the plurality of vibrating devices produce an interference pattern including a peak that produces a net circumferential displacement in the direction of rotation, thereby causing the monolithic post to rotate about a longitudinal axis of the monolithic post.

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