Linear and torsion motion vibrator

Abstract

The present invention is in the field of pile driving, wherein these piles are typically used for supporting buildings and the like. Piles can be used as support for onshore or offshore structures, such wind turbines. The present invention is in particular suited for driving piles of different sizes, which are often used in softer soils, such as sandy and clayey soils.

Description

[0001] LINEAR AND TORSION MOTION VIBRATOR

[0002] FIELD OF THE INVENTION

[0003] The present invention is in the field of pile driving, wherein these piles are typically used for supporting buildings and the like. Piles can be used as support for onshore or offshore structures, such wind turbines. The present invention is in particular suited for driving piles of different sizes, which are often used in softer soils, such as certain sandy and clayey soils.

[0004] RELATED APPLICATIONS

[0005] The present application claims the benefit of priority from Dutch Patent Application NL2037449, filed on April 12, 2024, in the name of Technische Universiteit Delft., The Netherlands.

[0006] The entire contents of the above-referenced applications and of all priority documents referenced in the Application Data Sheet filed herewith are hereby incorporated by reference for all purposes.

[0007] BACKGROUND OF THE INVENTION

[0008] The present invention is in the field of pile driving. Typically, piles are driven into the soil using hammers or weights dropping repeatedly on top of the pile. In regions with relatively soft soils, or where piles are needed as supports for man-made structures or the like, a relatively large number of piles is driven into the soil. The pile-driving process requires overcoming a large amount of shearing resistance in soil. This driving causes vibration and noise nuisance to the environment. In addition, such driving inflicts forces on the pile, which may weaken or damage the pile.

[0009] To reduce an intensity of the impacts, simultaneous excitation of vertical vibrations can used to reduce the penetration resistance. Studies, e.g. those of the present inventors, have shown that the simultaneous excitation of vertical and torsional oscillations of the pile may significantly reduces the pile resistance making it possible to abandon the use of hammers. Typically, the excitation of vertical and torsional vibrations of the pile requires the use of a shaker with at least three conventional twin-shaft vibrators. The design of such a complex vibrator is however rather bulky, expensive, and is found energy-inefficient in use. Specialized shakers are known that excite complex vibrations by mutual reduction of part of the produced centrifugal force, which leads to excessive energy consumption and more complicated construction. They also do not provide the necessary vibration shape for optimal vibratory pile penetration and extraction.

[0010] WO 2021 / 040523 Al, GB 687 603 A and JP S56 122419 A. W02021 / 040523 (Al) recites pile drivers with eccentric weights rotating around axis, for driving small- and mid-scale piles, which are often used in softer, non-cohesive, soils, such as sandy soils. Thereto a shaker is provided comprising wherein the vibrator comprises at least two groups of eccentric masses, each group i comprising at least two equal masses j, wherein the mass is attached to at least one horizontal axis, wherein horizontal axes are eccentric of the center of mass of the pile driver. GB 687 603 A recites improvements in the driving and pulling of piles, relating to arrangements for driving or withdrawing piles by imparting thereto, in addition to a succession of impulses along the axis of the pile, a series of alternating impulses in a direction perpendicular to the axis from a source unitary with the pile. Two horizontal flywheels having eccentric weights and rotated in the same direction thereby imparting oscillations at right angles to the axis of the pile, which may impart vertical oscillations. JP 856 122419 A recites a composite vibrator with a plurality of oscillating shafts, divided in pairs over upper and lower stages, each stage comprising at least two, and typically at least four eccentric masses.

[0011] GB 1066247 (A) recites a vibratory -hammer for driving members, such as piles, having a vertical and rotary action and comprising two shafts mounted on a support housing, and provided with gears and discs, the gears and discs being fitted with weights so that, upon rotation of the shafts in opposite directions, they exert a vibratory turning moment on the support housing thereby rotating it and at the same time, causing a percussive member to strike an anvil portion of the housing. The document is more concerned with driving using rotational vibration of the pile around a horizontal axis (somewhat confusingly referred to as torsion). In addition, the rotation of the respective masses is coupled and takes place at comparable frequencies.

[0012] Further background art can be found in US 20200398355 Al, and EP 0 840 191 Al. US 20200398355 Al uses a reciprocating mechanism, thus it converts the rotary motion of eccentric masses into a linear motion of the reciprocating mechanism. EP 0 840 191 Al recites an apparatus for generating a linear vibratory output force (al- so sometimes called a reciprocating output force) having a controllable amplitude. So, these documents relate to a different mechanism of driving piles.

[0013] The present invention therefore relates to an improved pile driver and a method for driving piles, which solves one or more of the above problems and drawbacks of the prior art, providing reliable results, without jeopardizing functionality and advantages.

[0014] SUMMARY OF THE INVENTION

[0015] It is an object of the invention to overcome one or more limitations of pile drivers of the prior art and methods of driving piles and at the very least to provide an alternative thereto. The present invention may be considered to relate to a vibrator causing torsional vibrations around a vertical axis, in combination with linear vertical vibration. The torsional vibrations may take place at a different, typically higher, frequency that the vertical vibrations and are considered to continuously break static friction of the pile with surrounding soil. In an exemplary embodiment, however, frequencies are substantially the same. It is noted that (providing) pile rotation is considered in comparison to torsional vibration that the two relate to qualitatively and physically rather different phenomena. During the rotation, the tangential friction force between the pile and the soil always acts in one and the same direction, hence rotation. In case of the torsional vibration, the direction of the force is alternating, hence vibration. Consequently, the local pilesoil interaction at the interface is completely different and the pile driving mechanics is completely different. In addition, a continuously rotating pile, and, therefore, a continuously rotating shaker on top of it will require implementing a swivel otherwise the hydraulic hoses (if the shaker is hydraulic) or electric cables (if the shaker is electric) will be overtwisted and eventually broken. In brief, the torsional frequency is equal to the vertical vibration frequency, and equal to the angular frequency of the pair of unbalanced rotors and equal to the angular frequency of the pair of vertical bevel gears. But the phase of vertical and torsional vibrations differ by 90 degrees, because the amplitude value of vertical vibration is generated at the vertical position of mass eccentricity in the process of rotation of unbalanced rotors, and the torsional value of vibration is generated at the horizontal position of these eccentricities. The 90 degrees phase difference implies that a maximum displacement of one type of vibration (e.g. vertical vibration or torsional vibration) always concedes with a zero displacement of the other type of vibration (e.g. torsional vibration or vertical vibration). This is found way more efficient than e.g. prior art vibrators without such a difference in phase. Even if more pairs of unbalanced rotors are used, such as two pairs of unbalance weights, there is no phase shift between the pairs of unbalance shafts when torsional and vertical vibrations are generated. The accelerations of vertical and torsional vibrations could be as large as 20g (g being the gravitational acceleration). As the coupling between the soil and the pile is broken the vertical vibration drives the pile into the soil. Vertical vibrations could be used to reduce friction in the soil and increase the pile drivability. However, the present experimental results have shown that a combination of vertical and torsional vibrations is more effective for this purpose. To excite complex vibrations, it is found necessary to use sophisticated vibration equipment. The present invention provides a constructive solution of a simple vibration exciter which may generate complex vibrations. The field of application of the present invention is the excitation of axial and torsional vibrations of piles during installation, and other cases when the combination of such vibrations is required. The invention can be used for penetration and extracting tubular piles, piles of circular crosssections with closed ends, or other driving rods. In the present invention virtually all consumed energy is used to produce an optimised form of vibrations. Also, the present linear and torsion motion vibrator is much simpler, lighter, cheaper in design, and consumes minimal power. In an embodiment the present linear and torsion motion vibrator is composed of a metal plate (base body) that, through bearings supports pairs of horizontal coaxial shafts, which may be synchronized through bevel gears. The shafts, each with an equal static moment, are aligned symmetrically relative to a (virtual) longitudinal axis of the vibrator, and are rotated in counterphase and in opposite direction. Typically the present unbalanced rotors are rigidly fixed to the respective shafts. Typically each pair of unbalance weights has the same phase in relation to the other phases of the unbalance weights. The motor may be located coaxially with the longitudinal axis of a to be driven pile and is configured to rotate the driving bevel gear, which rotates the driven bevel gears and shafts with eccentric weights at the other end of the shafts. Information on bevel gears may be found on https: / / en.wikipedia.org / wiki / Bevel_gear). The counter-rotation of unbalanced rotors in pairs induce rotation vectors of centrifugal forces. The weight eccentricities of the pairs of rotating weights are oriented in opposite directions concerning the centre of rotation when they are positioned perpendicularly to the longitudinal axis of the vibrator and pile, and then the vibrator induces torques, but the eccentricities of the rotating weights are oriented to the same direction when they are positioned parallel to the longitudinal axis of the vibrator, and in this position of the weights the vibrator induces vertical axial forces. When the vibrator shafts rotate at a given speed, the vibrator generates sinusoidal axial and torsional vibrations of the rigidly attached to vibrator pile or other bodies. Therewith the present linear and torsion motion vibrator, as shown by experimental studies, provides better drivability of tubular piles e.g. in comparison with the widely used twin-shaft exciter of vertical vibrations. In prior art, the excitation of complex vibrations is usually accompanied by the use of sophisticated equipment. The excitation of axial and torsional vibrations typically requires the application of three conventional twin-shaft vibrators or six shafts and at least six eccentric weights, whereas the excitation of the same vibrations by the present vibrator may require only two shafts and two eccentric weights. So, a new simple design of a vibrator to excite complex axial and torsional vibrations is provided. The present linear and torsion motion vibrator is much simpler to manufacture and less expensive to operate than common twin-shaft, four-shaft vibrators, and other vibrators. As mentioned, the present linear and torsion motion vibrator consumes significantly less energy in comparison with two-shaft and four-shaft vibrators, such as 20-80% less energy, in particular 30-50% less energy. In prior art vibrators almost half of the energy is consumed to generate an in view of the goal of pile driving worthless component of the periodic force, and which mutually eliminates. In the present new vibrator design, all the energy consumed is used to generate the useful periodic axial force and torque. The present vibrator provides an optimal phase shift between the vertical periodic displacement of the pile and its torsional vibration velocity. This phase shift minimizes the frictional resistance in the soil, consequently, the resistance to pile installation is minimized, and as a result, the pile penetration and extraction speed increases. As experimental studies have shown, the best drivability of tubular piles provides the simultaneous action of axial and torsional periodic vibrations of high frequency. However, in practice, vertical vibrations of low and medium frequency are traditionally generated by hydraulic motors, which are more reliable under vibration conditions but can't develop high rotation speed. This problem solves a new design of the linear and torsion motion vibrator. Since the diameter of the vibrator drive gear is larger than the diameter of the driven gears, it makes it possible to use low-frequency motors to excite high-frequency vibrations. This quality is particularly important in terms of reducing vibration fatigue and increasing the reliability of the vibrator. The possibility of using low-frequency motors to induce high- frequency vibrations presents an opportunity to use the most reliable low-frequency hydraulic motors, which are well-proven in such conditions. The present linear and torsion motion vibrator has a less negative impact on the environment, due to the use of vertical vibrations of lower intensity, which are the main source of vibration propagation in the ground and vibratory nuisance to the environment. In an exemplary embodiment of the present vibrator the controller may be adapted to control the sum of vertical forces of the groups to be cancelled. By varying angular velocity and typically by carefully selecting and balancing masses, and radius and / or distance, the sum of vertical forces is cancelled. This results in a very stable mode of operation with a minimum amount of noise.

[0016] In a first aspect the present invention relates to a linear and torsion motion vibrator (100) for gentle monopile driving comprising at least one pair (5,6) of unbalanced rotors (i,j), wherein i is the number of an unbalanced rotor in pair j, with j e [ 1 ,n], each unbalanced rotor independently rotationally driven by at least one rotor actuator assembly RAAij in opposite rotational direction with at least one first rotational frequency 01 and first phases tpij along a coaxial axis a centre of mass of each unbalanced rotor located eccentric of at least one virtual horizontal first axis and positioned <pi j 180 degrees out of phase with respect to one and another <p2j, and located at opposite sides of the vibrator, and typically at a same distance of a vertical rotation axis of the vibrator, the first one horizontal axis being located centrally in the vibrator, that is, running through a centre of the vibrator (see e.g. figs. 1 and 3), and a controller, wherein the controller is configured for controlling each individual rotational frequency on and phase <pij. Said controller may be provided as part of the rotor actuator assembly, or, as in a further embodiment, as a rotor driver. An example thereof is given in Fig. 1, whereas fig. 3 shows a more advanced exemplary embodiment. The embodiment of fig. 1 can for instance be used for driving piles of more typical sizes, whereas the embodiment of fig. 3 is in particular suited for driving piles of very large sizes, e.g. with diameters of 3-20 m and lengths of 10-80 m. By adding more pairs, in particular with different mechanical properties, such as different masses and / or different eccentricities and / or different rotational frequencies, the present vibrator can generate a poly-harmonic signal, i.e. vibrations that contain multiple different frequencies. In general, the present vibrator may comprise a rather unlimited number of pairs of shafts. The pairs may be driven by a single motor, they can simultaneously generate poly-harmonic vibrations, such as with a required set of different vibration frequencies, which may depend on the type of elements being driven and the properties of the soil. The design of the present vibrator generates longitudinal and torsional vibrations, which may be of the same or of different frequencies, in a wide range of frequencies, such as 10, 20, 30, 40, 50, 50, 60, 70, 80, 90, 100 Hz simultaneously and more. In the case of more than one pair of unbalanced masses it is preferred to use the same rotational frequency for all pairs of unbalanced masses, or to use harmonic frequencies, that is, integer multiples of a (ground) first frequency; it is found that e.g. energy consumption of the present vibrator is therewith much lower. Likewise, a single vibration frequency can be generated, such as by huge pairs of unbalanced shafts, thereby exciting dynamic forces of very large magnitude. The present vibrator is therewith considered fundamentally different from prior art ones and can provide results unavailable to all previously known. In particular, the presence of many vibration frequencies ensures that the excitation frequency always corresponds to the optimum vibration mode of pile penetration regardless of pile type, soil type, and depth of penetration. Moreover, this entire set of frequencies may be adjusted by changing the motor shaft speed. In addition the presence of e.g. a large number of unbalanced shafts makes it possible to generate huge dynamic forces capable of exciting intense vibrations of monopiles of enormous dimensions, such as those provided under wind turbines, without any overload of the vibrator parts, fastenings, and piles. In summary, the present vibrator generates a vertical periodic force and a torsional periodic torque, under the action of which the pile is driven in a reciprocating vertical motion into the ground, under the action of the pile's own weight, and the vertical and torsional vibrations. The present vibrator may generate polyharmonic vertical and torsional vibrations of many different frequencies simultaneously. In a second aspect the present invention relates to a method of driving a monopile into a soil, comprising providing the present vibrator (100), mounting the vibrator (100) on a monopile, and driving the monopile into the soil. It has been found that surprisingly the pile can be driven into the ground using significantly less energy, and at a noise level that hardly disturbs the environment, such as < 60 dB.

[0017] Advantages of the present description are detailed throughout the description.

[0018] DETAILED DESCRIPTION OF THE INVENTION

[0019] In an exemplary embodiment the present vibrator comprises at least one rotor driver 8 rotating at a second rotational frequency 02 and configured for driving unbalanced rotors (5,6), in particular wherein the rotor driver is a hydraulic motor. So, with only one rotor driver all unbalanced weight can be driven. By carefully selecting a transmission even different rotational frequencies Oj for the respective groups of unbalanced rotors could be provided.

[0020] In an exemplary embodiment the present vibrator comprises at least two groups j>2 of unbalanced rotors, each group j comprising at least two equal unbalanced rotors i, and wherein a unbalanced rotor wij on one side is displaced 180 degrees with respect to a unbalanced rotor W2j on the other side, wherein the unbalanced rotor wij is attached to at least one horizontal axis haj, in particular comprising 3-12 pairs of unbalanced rotors, more in particular 4-9 pairs of unbalanced rotors. The present vibrator is therewith versatile in design parameters, yet remaining simple in design itself. More pairs are found to provide less fatigue, and quicker pile driving as well. With the term “equal” (or likewise “same”) it is meant that the relevant quantity has within given accuracies the same size.

[0021] In an exemplary embodiment of the present vibrator phases <pi j are equal for all groups) and wherein phases <p2j are equal for all groups). Such is for example shown in fig. 3.

[0022] In an exemplary embodiment of the present vibrator in each pair of unbalanced rotors (5,6) each unbalanced rotor is rotationally driven by the at least one rotor actuator assembly RAAij in opposite rotational direction with the same first rotational frequency © 1. In general, unbalanced rotors are configured to be driven in opposite angular rotation (with respect to the same axis); by the present design such driving is provided, automatically, by the present rotor driver 8.

[0023] In an exemplary embodiment of the present vibrator in each pair of unbalanced rotors each unbalanced rotor (i,j) is the same, in particular wherein in each pair of unbalanced rotors each unbalanced rotor has the same weight, and / or wherein in each pair of unbalanced rotors each unbalanced rotor has the same eccentricity, of mass. In the alternative the unbalanced rotors of a specific pair could be different from the unbalanced rotors from another specific pair; so, comparing a first pair of unbalanced rotors with a second pair of unbalanced rotors, the masses in the second pair may be larger or smaller than those in the first pair, the eccentricity with respect to the centre of mass of the vibrator in the second pair may be larger or smaller than that in the first pair, and the eccentricity with respect to the horizontal axis ha2 in the second pair may be larger or smaller than the horizontal axis hai in the first pair. Further, the rotational frequency ©1 may be larger or smaller than the rotational frequency ©2. So a large variety of unbalanced rotors, and design thereof, may be used, as well as a number of groups of such rotors. Typically, in view of simplicity of construction only a limited number of groups is used, such as six or eight, but the invention is not limited thereto.

[0024] In an exemplary embodiment of the present vibrator a radius of a vertical bevel gear 10 is as it is, whereas the diameters dij of coaxial horizontal first actuators 11,21 is different, such as wherein dy=i / dij=2 is >1.2, more in particular 1.3-10, even more in particular 3 -8, such as 5-6.

[0025] In an exemplary embodiment of the present vibrator, due to the difference in diameters of the driving bevel gear dlO and the at least one pair of the driven bevel gears or actuators 11 and 21 by at least 1.2 times, in in particular 1.2-10 times, such as 3-5 times larger, accordingly, the at least one first rotational frequency co i is at least 1.2 times larger than the second rotational frequency ©2, in particular 1-10 times larger, such as 3-5 times larger. Such is found to provide improved performance.

[0026] In an exemplary embodiment the present vibrator comprises at least one rotation distribution unit (RDU), wherein the at least one RDU is configured to transfer rotor driver rotation to the at least one pair of unbalanced rotors, in particular wherein the at least one RDU comprises a gear (10) connected to rotor driver 8, in particular connected through shaft 9, in particular a first bevel gear, wherein said bevel gear (10) is in rotational connection with at least one rotor actuator assembly RAAij, in particular both RAA’sij’ with equal j (on the same horizontal axis), more in particular with both RAAij’s of more than one j’s, wherein at least one rotor actuator assembly RAAij comprise a bevel gear. Alternatively, the use of cylindrically gears, belt drives, cardan shafts can be considered. Therewith a simple, yet effective, design is provided for transmission of the rotor driver to the respective pairs of unbalanced rotors.

[0027] In an exemplary embodiment the present vibrator comprises two or more RDU’s, such as wherein two or more RDUs are configured to be driven independently, in particular wherein a number of RDU’s Nrdu is equal to a number of groups of unbalanced rotors j, or an integer fraction of j; e.g. when j=6, Nrdu is one of 1, 2, 3 or 6. As such each pair of unbalanced rotors is rotated with different rotation velocity and therefore generates a different frequency of vibration, for example one vibrator with six pairs of coaxial unbalanced rotors as in FIG 3 can generate simultaneously vibrations with frequencies of 20, 40, 60, 80, 100, 120 Hz. This is considered rather novel and inventive. Such may for instance vary by mono-pile size and soil properties. In particular by activating or deactivating one of them during the pile driving process, the number of working eccentric weights can be controlled, and therefore the vibration modes can be set as required according to the pile resistance at a given moment. Such may for instance vary depending on mono-pile size and soil properties.

[0028] In an exemplary embodiment of the present vibrator each at least one rotor actuator assembly RAAij is provided on a horizontal axis haj and wherein respective unbalanced rotors are provided on the same horizontal axis haj. The respective RAA therewith provides an uncomplicated design for transmission of part of the rotor driver to the respective unbalance rotors. It may further comprise one or more bearings for supporting the horizontal axis and providing for free rotation thereof.

[0029] In an exemplary embodiment of the present vibrator a centre of mass of each individual unbalanced rotor wij is positioned at a distance Rj from the centre of mass of W2j.

[0030] In an exemplary embodiment of the present vibrator a centre of mass of unbalanced rotors may be located at a distance ej from horizontal rotation axis haj. In an exemplary embodiment of the present vibrator the distance / radius er is 1-50 cm, preferably 2-40 cm, such as 3-30 cm. In an exemplary embodiment of the present vibrator the masses of the unbalanced rotors may be 5- 5000 gr, preferably 10-1000 gr, such as 30-600 gr, e.g. 50-400 gr. For larger piles and / or heavier soils and / or stiffer soils larger masses may be used. In addition, or as alternative, angular velocities may be increased.

[0031] In an exemplary embodiment of the present vibrator horizontal axes haj concur with a central vertical axis Cm, typically within a few%, such as within 2% or even within 1%. See for instance fig. 3, schematically showing this. An improved performance, stability, etc.

[0032] In an exemplary embodiment of the present vibrator the at least one rotor actuator assembly RAAij comprises at least one first actuators (11,21) in mechanical and rotational connection with the at least one rotor driver (8), wherein each individual first actuator (11,21) is provided on an actuator axis, wherein said actuator axis is rotationally supported by respective unbalanced rotor supports (3,4), and wherein said actuator axis is a respective axis of unbalanced rotors (i,j).

[0033] In an exemplary embodiment of the present vibrator is configured to drive the at least one first actuator and the rotor driver to generate sinusoidal forces, typically with the same frequency, and providing harmonic oscillations. Essentially in this case, the harmonic oscillations consist of the sum of vertical and torsional sinusoidal oscillations of equal frequency.

[0034] In an exemplary embodiment the present vibrator comprises a base (2), on the base unbalanced rotor supports (3,4), each individual unbalanced rotor support configured to provide rotation of at least one first actuators (11,21) and unbalanced rotors (5,6).

[0035] In an exemplary embodiment the present vibrator comprises a fixator (1), in particular a clamp, configured for rigidly fixing the vibrator to the said pile. The fixator is configured for mechanically fixing a vibrator to a pile, and thus for transferring vibrational energy to the pile. The vibrator can drive piles into the soil by means of torsional vibration, in combination with vertical vibration, typically at given frequencies. No further driving means are required, such as a hammering device. Thereto the unbalanced rotators rotate at typically high speed. The vibrator, and the present method, are more rapid and less noisy. For instance, for a midsized pile of e.g. 10 m length and with a diameter of about 75 cm the pile is driven about twice as fast compared to prior art techniques. The pile may move downward with a speed of some 15 cm / second. In addition, no or less deformation of the pile is achieved, compared to an impact hammer. The energy generated by the present vibrator is mainly used for driving the pile. In an exemplary embodiment the present vibrator may comprise a receiving structure, such as a groove. Therewith the pile can be firmly attached to the present vibrator.

[0036] In an exemplary embodiment the present vibrator comprises a rotor driver support (7) for supporting the rotor driver, in particular wherein said rotor driver support is provided as a horizontal plate comprising a bearing configured for shaft 9. In an exemplary embodiment the present vibrator is configured for rotating the rotors Wij around their horizontal axis haj, such that rotors Wij each rotate at a same angular velocity Oj around said horizontal axis haj.

[0037] In an exemplary embodiment of the present vibrator a centre of rotor driver cmof the vibrator and a longitudinal axis of the monopile concur.

[0038] In an exemplary embodiment of the present vibrator at least one rotor driver (8) is each individually adapted to rotate horizontal rotation axes haj at a first rotation frequency of 10-50 Hz (600-3000 rpm), preferably at 12-30 Hz, more preferably at 15-25 Hz, such as at 16-24 Hz.

[0039] In an exemplary embodiment of the present vibrator at least one rotor actuator assembly RAAij is each individually adapted to rotate the vibrator at a torsion frequency of 10-200 Hz (600-12000 rpm), preferably at 30-150 Hz, more preferably at 50-120 Hz, such as at 70-100 Hz.

[0040] In an exemplary embodiment of the present vibrator the weights are 5-5000 gr, preferably 10-1000 gr, such as 30-600 gr.

[0041] In an exemplary embodiment of the present vibrator distance ej is 1-50 cm, preferably 2-40 cm, such as 3-30 cm.

[0042] In an exemplary embodiment of the present vibrator the vibrator is configured to adjust at least one distance of ej and Rj, in particular wherein the vibrator is configured to adjust all distances ej and Rj.

[0043] In an exemplary embodiment of the present vibrator the fixator (1) is configured to fix the vibrator outside to the monopile, inside to the monopile, over an edge of the monopile, and combinations thereof.

[0044] In an exemplary embodiment of the present method the vibrator is calibrated before driving the monopile into the soil. As such driving forces, angular velocities, and so on, can be controlled better in view of soil properties, interaction between pile and soil, and so on.

[0045] In an exemplary embodiment of the present method the controller changes the rotational frequency ecu of the at least one pair (5,6) of unbalanced rotors (i,j), in particular increases or decreases said rotational frequency on, or maintains said rotational frequency ecu, in particular wherein a change is a result of a feedback loop.

[0046] The invention will hereafter be further elucidated through the following examples which are exemplary and explanatory of nature and are not intended to be considered limiting of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims.

[0047] EXAMPLES

[0048] The linear and torsion motion vibrator consists of a single pair of coaxial shafts with eccentric weights or several such pairs. For the sake of clarity, the principle of vibrator operation is first described for the simplest vibrator with two coaxial shafts. The linear and torsion motion vibrator excites axial and torsional vibrations by a pair of synchronized rotation eccentric weights located symmetrically to the centre of the vibrator (Figure 1). The vibrator is connected to the pile via clamping device 1 and is clamped above the centre of the cross-section of the pile head, or other profiles, and secured with clamps. A base of vibrator 2 with supports 3 and 4 for eccentric rotating weights 5 and 6 is rigidly attached to the top of the clamping device. On top of supports 3 and 4 rests plate 7 with a support for motor 8. In the figure, plate 7 is conventionally shown transparent for better clarity. The motor with a vertical shaft 9 rotates a bevel gear 10, which transmits rotation to two bevel gears 11 and 21, on the shaft with which there are respectively eccentric weights 5 and 6, rotating by the drive in different directions with the same speed and phase of rotation. The ratio of the diameter of driving bevel gear 10 to the diameters of driven bevel gears 11 and 21 is calculated based on the initial data on the operating frequency of the motor and the required vibration frequency according to the technology used for vibratory pile driving. During operation, the vibration frequency is adjusted over a wide range by varying the motor speed. The rotational frequencies oi ando2 obtained depend in this case on the diameters dio on the one hand and du and d2i on the other hand, as 0 / 02= du / du, and 0 / 02= du d2i.

[0049] The eccentric mass m at the rotation with frequency co and eccentricity e concerning its rotation axis creates a circular vector of centrifugal force F=Mco2, M is the static moment M= me. The vector of centrifugal force of the eccentric weight 5 rotating in the positive direction F=Fieicot. The vector of centrifugal force under the action of the eccentric weight 6 rotating in the negative direction F=F2eicot.

[0050] In Figure 1, axial vibrations are excited by a pair of unbalanced rotors with an equal static moment, and located on the same axis of rotation, symmetrically relative to the longitudinal axis of the vibrator, whose shafts rotate in phase in opposite directions. The amplitude of the axial force of the vibrator at Fi=F2=Fais equal to:

[0051] F=Fae(lwt)+Fae('lwt)=2Mco2cos(cot) .

[0052] The line of the axial force passes through a point equidistant from the centres of rotation of the eccentric weights, which must concur with the longitudinal axis of the pile. At the same time, the sinusoidal torque is provided by eccentric weights 5 and 6, located at a distance R between them and rotating in opposite directions as shown in Figure 1. In this case, the sinusoidal torque around the longitudinal axis is defined as: (cot).

[0053] Thus, eccentric weights 5 and 6 during shaft rotation produce two circular vectors of centrifugal forces with amplitude value F which creates the axial periodic force and periodic torque with a phase shift of 90°. Table 1 shows the value of axial periodic forces and torsional periodic torques at characteristic phases during shafts rotation by one revolution through 90°. So as a result, the tubular pile is subjected to periodical torque T around the longitudinal axis of the present vibrator and periodical vertical force F along this axis (Table 1). Position of the unbalanced Value of periodic loads due to the generation of two rotors in characteristic centrifugal forces by two rotating unbalanced rotors phases through 90° Horizontal position I The periodic torque around the longitudinal axis is equal to amplitude value T=RMco2and is clockwise relative to this axis, and the axial periodic force along the longitudinal axis is equal to zero F=0.

[0054] Vertical position II The torsional periodic torque around the longitudinal axis is equal zero T=0, and the axial periodic force along this axis is equal to amplitude value F=2Mco2and directed upwards.

[0055] Horizontal position III The torsional periodic torque around the longitudinal axis is equal amplitude value T=-RMco2directed anti-clockwise relative to the this axis, and axial periodic force along the longitudinal axis is equal to zero F=0.

[0056] Vertical position IV The torsional periodic torque around the longitudinal axis is equal zero T=0, and axial periodic force equal to the amplitude value F=2Mco2and directed downwards along this axis.

[0057] TABLE 1 : overview of vibrator effects in view of unbalanced rotor position.

[0058] Values of periodic torque and axial periodic force at characteristic phases of vibrator shaft rotation at 90° intervals depicted in table 1.

[0059] The uniform sinusoidal torque and axial force with the constant phase shift between them, is illustrated in Figure 2. The vertical axis denotes the amplitudes of torsional vibrations and vertical vibrations, and the horizontal axis denotes time. The present vibrator creates torsional vibrations around the vertical axis of the vibrator and pile by the action of the torque (from a pair of horizontal parallel forces directed in different directions) and vertical vibrations along the longitudinal axis of the pile (vertical axis of the vibrator) by the action of the same pair of vertical parallel forces generated by unbalanced two coaxial rotors. The torsional oscillations are made around the vertical axis of the pile due to periodic clockwise and anticlockwise movement in one oscillation period, and the vertical oscillations due to periodic upward and downward movement in the same oscillation period. The frequency of both torsional, and vertical vibrations are therefore the same and equal to the rotational speed of the unbalanced rotors.

[0060] As can be seen from Table 1 and Figure 2, during one complete revolution of the shafts with eccentric weights is induced one period of sinusoidal torque and axial force with a phase shift of 90°. The vibrator generates accordingly torsional and axial vibrations with the same phase shift. This form of pile vibration provides the highest installation speed and the lowest energy consumption during pile installation, due to the phase shift between the dynamic load and the corresponding dynamic displacement, it can be stated that the maximum value of the axial vibration displacement concurs in time with the maximum value of the torsional vibration velocity (Table 2). According to the theory of soil dynamics, the friction in the soil is less the higher the vibration speed is. This ensures the highest efficiency of this pile-driving technique.

[0061] Unbalanced rotor Oscillation Torsional Vertical Torsional Vertical position phase, displacement displacement velocity velocity degrees modulus modulus modulus modulus

[0062] I 0° max 0 0 max

[0063] II 90° 0 max max 0

[0064] III 180° max 0 0 max

[0065] IV 270° 0 max max 0

[0066] TABLE 2: overview of vibrator effects in view of unbalanced rotor position, torsional, vertical displacements and velocities at characteristic vibration phases.

[0067] As mentioned before, several pairs of eccentric weights can be symmetrically arranged around the perimeter of the pile ring to excite torsion and axial vibrations. In Figure 3 the vibrator contains six pairs of eccentric weights such as 1 and 3 located at the end of rotors or shafts 2 and 4 supported by bearings 5. The position of the eccentric weights and the values of the centrifugal forces correspond to the above description in Figure 1. Such vibrator excites the harmonic torque and vertical axial force with the same phase ship. The difference is that the same static moment of eccentric weight according to Figure 3 generates a six times larger amount of periodic force and torque at the same loads on the shafts, which is important from the point of view of ensuring their vibration fatigue and vibrator reliability. In case of large diameter penetration structures, e.g. monopiles of the offshore wind industry, when it is necessary to apply a large dynamic load during installation, it is possible to solve this problem by using a large number of pairs of eccentric weights located and synchronized in the above way. No additional synchronization of all shafts is required and vibrator can operate reliably, and without any overloading.

[0068] Figure 4 shows schematically a working principle. The vibrator creates torsional vibrations around the vertical axis of the vibrator and pile by the action of the torque (from a pair of horizontal parallel forces directed in different directions) in positions II and IV and vertical vibrations along the longitudinal axis of the pile (vertical axis of the vibrator) in positions I and III by the action of the same pair of vertical parallel forces generated by unbalanced two coaxial rotors. The torsional oscillations are made around the vertical axis of the pile due to periodic clockwise (iV position) and anti -clockwise movement (II position) in one oscillation period, and the vertical oscillations due to periodic upward (I position) and downward (III position) movement in the same oscillation period. The frequency of both torsional, and vertical vibrations are therefore the same and equal to the rotational speed of the unbalance shafts.

[0069] SUMMARY OF THE FIGURES

[0070] The invention is illustrated by drawings to provide a better understanding of the vibrator design and its ability to produce complex axial vibrations in the vertical direction and torsional vibrations in the horizontal plane using the pairs of eccentric weights arranged, orientated, and synchronized in a certain way. Figures 1, 2 and 3 show details of the linear and torsion motion vibrators with a pair of rotation eccentric weights and with six pairs of eccentric weights. DETAILED DESCRIPTION OF FIGURES

[0071] In the figures:

[0072] 100 vibrator

[0073] 1 clamping device

[0074] 2 base of vibrator

[0075] 3 support of the first rotation eccentric weight

[0076] 4 support of the second rotation eccentric weight

[0077] 5 first eccentric weight

[0078] 6 second eccentric weight

[0079] 7 bearing plate

[0080] 8 motor

[0081] 9 shaft of drive bevel gear

[0082] 10 drive bevel gear

[0083] 11 first driven bevel gear / actuator

[0084] 12 second driven bevel gear

[0085] I first horizontal position

[0086] II first vertical position

[0087] III second horizontal position

[0088] IV second vertical position

[0089] Cm centre of mass

[0090] Rj distance R of centre of mass mij from centre of mass n j for pair j ej distance i of mass mij from a horizontal rotation axis hai haj horizontal axis j dij diameter of a respective gear i,j

[0091] Wij mass i of group j

[0092] Oj angular velocity j

[0093] Figure 1 demonstrates the vibrator of torsional and vertical vibrations consists of a rigid base, a motor, and three bevel gears that transfer the rotation from the motor to the two eccentric weights whose shafts counterrotate about a common axis, and they are positioned, synchronized, and fazed originally. The eccentric weights are located on different sides of the pile symmetrically to its longitudinal axis. The vibrator' s center weight concurs with the longitudinal axis of the pile and exciter. When two eccentric weights of the vibrator start rotation with the same speed, two centrifugal forces are generated. Each eccentric weight induces a rotating vector of centrifugal force, the magnitude of which is determined by the value of the static moment and the square of the angular velocity of rotation. The original arrangement, direction, speed, synchronization, and in-phase rotation of eccentric weights provide the generation of the desired shape and value of the periodic torque relative to the vertical longitudinal axis and axial periodic force along this axis, as the summa of rotating vectors of centrifugal forces.

[0094] The results of the performed studies have shown that the best drivability is observed at high vibration frequencies. At the same time, hydraulic motors as more reliable under the influence of vibrations are widely used in the practice of pile driving. These motors are low- frequency and are not able to provide the necessary mode of operation at high frequency. The present invention solves this problem where the desired rotational speed and in-phase synchronization of the shafts are provided by a transmission with bevel gears. Since the diameter of the driving bevel gear is significantly larger than the diameters of the two driven gears, it is possible to develop a high-speed rotation of the eccentric weights with a low-frequency motor. That is, high-frequency vibrations are generated by a low-speed motor.

[0095] Figure 1 shows four principal positions of eccentric weights with 90° phase shift in one revolution of the vibrator shafts, which provide induction of complex vibrations of the desired shape, namely the sum of a harmonic vertical force and a torsional moment. In the first horizontal position I, the eccentric distances are oriented horizontally in opposite directions perpendicular to the shaft axis. In this position, two differently directed forces located at the same distance from the longitudinal axis of the pile create the torque relative to the longitudinal axis of the pile. The vertical force in this position is zero. In the first vertical position II, the eccentric distances are oriented vertically upwards and perpendicular to the shaft axis. In this position, two equal parallel forces located at the same distance from the longitudinal axis of the pile sum up to create an axial total force along the longitudinal axis of the pile. The torque in this position is zero. In second horizontal position III and second vertical position IV, respectively, the same maximum force and torque occur, but in opposite directions. Thus, one period of sinusoidal force and torque is induced during one revolution of the vibrator shafts. Naturally, in the process of shaft rotation with a given frequency a periodic torque and axial force of the same frequency are provided. The weight of eccentrics and eccentricity distance are assigned according to the desired value of periodic axial force and torque, which are taken based on the analysis of geological conditions, pile parameters, and vibrator shaft speed.

[0096] Figure 2 shows the variation in time of periodic torque and axial force provided by the vibrator and measured accordingly. In Figure 2 (1) is periodic torque, and (2) is axial force. As can be seen from the figure, the phase shift between the torque and the axial force is 90°. The vibrator generates torsional and vertical vibrations respectively. Naturally, there is a phase shift between sinusoidal dynamic loads and displacements, which still does not significantly change the phase shift between torsional and vertical vibration. This means that the vibration analysis performed in Tables 1 and 2 allows us to state that in phase, the maximum vertical displacement of the pile under action of vertical longitudinal forces concurs with the maximum torsional vibration velocity. As stated earlier, the torsional vibration reduces the friction resistance in the soil, so it reduces the resistance to pile penetration and extraction. The greatest drivability occurs when maximum value of downward displacement of the pile vibration concurs with maximum value of its torsional velocity. This phase shift ensures that the pile is penetrated in the best possible way, i.e. with the lowest soil resistance (internal friction in soil), the lowest energy consumption and the highest penetration rate. This is explained by the fact that with this form of oscillation, the maximum amplitude of the vertical oscillation concurs in time with the maximum velocity of the torsional oscillation. The theory indicates that the higher the oscillation velocity is, the lower the ground friction is. Therefore, this form of pile vibration provides the least resistance to vibratory driving. Consequently, the vibrator with this form of vibration provides the best drivability, the lowest energy consumption, the lowest value of vertical vibrations, which are a source of negative environmental impact.

[0097] Figure 3 shows the linear and torsion motion vibrator with six pairs of unbalanced rotors, in particular exemplary eccentric weights.

[0098] In Figure 3:

[0099] 1 first eccentric weight W11 of the first pair of shafts

[0100] 2 first shaft of the first pair of shafts

[0101] 3 second eccentric weight W21 of the first pair of shafts

[0102] 4 second shaft of the first pair of shafts

[0103] 5 bearings rings of shafts.

[0104] The linear and torsion motion vibrator with six pairs of eccentric weights has a similar principle arrangement as in Figure 1. The purpose of this illustration is to demonstrate the use of several pairs of eccentric weights to achieve the goal. A very large dynamic load on a largesized pile can be generated by medium-sized synchronized single-shaft vibrators, which are more reliable in vibro-installation. In addition, depending on the characteristics of the soils and the depth of the pile, the required number of vibrators can be switched on to avoid excessive vibratory action and energy consumption. The respective pairs of eccentric weights, and likewise the present unbalanced rotors (i,j), may be located at different distances per pair of unbalanced rotors wherein j is equal to one and another and i is 1 or 2. Adjustment of frequencies of excited vibrations may be provided by connecting the necessary diameters of drive bevel gears, and changing the motor shaft speed. Simultaneous excitation of a rather unlimited number of vibrations, with different frequencies and amplitudes, in a wide range from low-frequency to high-frequency vibrations, is found to guarantee selection of the optimal pile penetration mode. Typically, and in general, the frequencies are synchronized. As numerous experimental studies have shown, it is the required frequency and amplitude of vertical and torsional vibrations that ensure that pile penetration is carried out at the required speed to the required depth. In general, since the frequency and amplitude requirements depend on the properties of the pile, of the soil, and of the depth of penetration, the present poly-harmonic vibrator is able to fulfil a wide range of requirements, to reduce the energy consumption, and the environmental impact compared to traditional vibrators. The present generation of vertical and torsional vibrations of monopiles, which may be of enormous dimensions, by means of an unlimited number of eccentric weights of a given size, synchronized in the proposed manner and rotating by means of a single motor, provides the development of an rather unlimited magnitude of the required dynamic forces, with a maximum efficiency. The present design is found to provide the best way to achieve high pile penetration rates with the lowest energy consumption, while minimizing environmental impact.

[0105] Figure 4 shows torsion and vertical movements of the vibrator during one revolution of the pair of coaxial unbalanced rotors turning in different directions. It shows dynamic loading and movements of vibrator with a pile during one revolution of two coaxial unbalanced rotors with four positions (I, II, III and IV) after 90 degrees at which the vertical dynamic force and dynamic torque reach the amplitude value (maximum absolute value). The torsional and vertical displacements change in time accordingly. As a result, torsional and vertical axial vibration is generated at a predetermined frequency.

[0106] In Figure 4:

[0107] I, II, III and IV - four positions of the two coaxial unbalanced rotors, rotated in different directions of 0, 90, 180, 270 degrees from the initial position of the two eccentric weights upwards. Fl and F2- vectors of centrifugal forces of the rotating eccentric weights W1 and W2 respectively.

[0108] Fig. 5 shows an embodiment of a prior art document. WO 2021 / 040523 Al, e.g. fig. 2, shows two horizontal axels that are not located centrally of the vibrator, but eccentric. In addition, the masses ml,l and ml, 2 on the axis hal rotate in the same direction; which is also the case for the masses on axel ha2.

Claims

CLAIMS1. A linear and torsion motion vibrator (100) for gentle monopile driving comprising at least one pair (5,6) of unbalanced rotors w(i,j) configured for rotating on at least one same horizontal axis haj, wherein in a pair j unbalanced rotors w(i,j) i=l,2 are equal, each unbalanced rotor w(i,j) independently rotationally driven by at least one rotor actuator assembly RAAij in opposite rotational direction with at least one first rotational frequency co i and first phases c ij, a centre of mass of each unbalanced rotor located eccentric of at least one virtual horizontal first axis of the vibrator and configured to be initially positioned c ij 180 degrees out of phase with respect to one and another <p2j, and wherein in a pair unbalanced rotors w(i,j) are located at opposite sides of the vibrator, and a controller, wherein the controller is configured for controlling each individual rotational frequency ecu and phase c ij, characterized in that the linear and torsion motion vibrator is configured to provide both vertical movement and torsional movement of the said monopile having the same frequency co i and wherein vertical movement and torsional movement are 90 degrees out of phase, and wherein the at least one first one same horizontal axis haj being located centrally in the vibrator2. The linear and torsion motion vibrator according to claim 1, comprising at least one rotor driver (8) rotating at a second rotational frequency co 2 and configured for driving unbalanced rotors (5,6), in particular wherein the rotor driver is a hydraulic motor.

3. The linear and torsion motion vibrator according to any of claims 1-2, comprising at least two groups j>2 of unbalanced rotors, each group j comprising at least two equal unbalanced rotors i=l ,2, and wherein an unbalanced rotor wij on one side of the vibrator is configured to be initially displaced 180 degrees with respect to a unbalanced rotor W2j on the other side of the vibrator, wherein the unbalanced rotor wij is attached to at least one horizontal axel haj, in particular comprising 3-12 pairs of unbalanced rotors, more in particular 4-9 pairs of unbalanced rotors, and / or wherein phases cpij are equal for all groups) and wherein phases c 2j are equal for all groups).

4. The linear and torsion motion vibrator according to any of claims 1-3, wherein in each pair of unbalanced rotors (5,6) each unbalanced rotor is rotationally driven by the at least one rotor actuator assembly RAAij in opposite rotational direction with the same first rotational frequency co 1.

5. The linear and torsion motion vibrator according to any of claims 1-4, wherein in each pair of unbalanced rotors each unbalanced rotor w(i,j) is the same, in particular wherein in each pair of unbalanced rotors each unbalanced rotor has the same weight, and / or wherein in each pair of unbalanced rotors each unbalanced rotor has the same eccentricity.

6. The linear and torsion motion vibrator according to any of claims 3-4, wherein the weights in the second pair of unbalanced rotors are larger or smaller than those in the first pair of unbalanced rotors, and / orwherein the eccentricity with respect to the centre of mass of the vibrator in the second pair of unbalanced rotors is larger or smaller than that in the first pair of unbalanced rotors, and / or wherein the eccentricity with respect to the horizontal axis ha2 in the second pair of unbalanced rotors is larger or smaller than the horizontal axis hai in the first pair of unbalanced rotors, and / or wherein the rotational frequency ©i is larger or smaller than the rotational frequency ©2.

7. The linear and torsion motion vibrator according to any of claims 2-6, wherein the at least one first rotational frequency co 1 is at least 1.2 times larger than the second rotational frequency ©2, in particular 2-10 times larger.

8. The linear and torsion motion vibrator according to claim 2 and any of claims 3-7, comprising at least one rotation distribution unit (RDU), wherein the at least one RDU is configured to transfer rotor driver rotation to the at least one pair of unbalanced rotors, in particular wherein the at least one RDU comprises a gear (10) connected to rotor driver (8), in particular connected through shaft (9), in particular a first bevel gear, wherein said bevel gear (10) is in rotational connection with at least one rotor actuator assembly RAAij, wherein at least one rotor actuator assembly RAAij comprise a first actuator (11,21), such as a second bevel gear.

9. The linear and torsion motion vibrator according to any of claims 1-8, wherein a diameter of a vertical first bevel gear is dio, and diameters du, and d2i, respectively, of coaxial horizontal first actuators (11,21) are different from one and another, in particular wherein dij=i / dij=2 is >1.2, more in particular 1.3-10, even more in particular 3 -8, such as 5-6, and / or comprising two or more RDU’s, in particular wherein a number of RDU’s Nrdu is equal to a number of groups of unbalanced rotors j, or an integer fraction of j.

10. The linear and torsion motion vibrator according to any of claims 1-9, wherein each at least one rotor actuator assembly RAAij is provided on a horizontal axel haj and wherein respective unbalanced rotors are provided on the same horizontal axel haj, and / or wherein a centre of mass of each individual unbalanced rotor wi j is positioned at a distance Rj from the centre of mass of rotor W2j, and / or wherein horizontal axes haj concur with a central vertical axis Cm.

11. The linear and torsion motion vibrator according to claim 2 and any of claims 3-10, wherein the at least one rotor actuator assembly RAAij comprises the at least one first actuators (11,21) in mechanical and rotational connection with the at least one rotor driver (8), wherein each individual first actuator (11,21) is provided on an actuator axel, wherein said actuator axel is rotationally supported by respective unbalanced rotor supports (3,4), and wherein said actuator axis is a respective axel of unbalanced rotors (i,j).

12. The linear and torsion motion vibrator according to any of claims 7-11, configured to drive the at least one first actuator (11,21) and the rotor driver (8) to generate harmonic vibrations.

13. The linear and torsion motion vibrator according to any of claims 7-12, wherein first bevel gear (10) and at least one rotor actuator assembly RAA are to drive the at least one actuator and the rotor driver to generate harmonic vibrations.

14. The linear and torsion motion vibrator according to any of claims 1-13, comprising a base (2), on the base unbalanced rotor supports (3,4), each individual unbalanced rotor supportconfigured to provide rotation of at least one first actuators (11,21) and unbalanced rotors (5,6).

15. The linear and torsion motion vibrator according to any of claims 1-14, comprising a fixator (1), in particular a clamp, configured for rigidly fixing the vibrator to the said pile.

16. The linear and torsion motion vibrator according to any of claims 1-15, comprising a rotor driver support (7) for supporting the rotor driver, in particular wherein said rotor driver support is provided as a horizontal plate comprising a bearing configured for shaft (9).

17. The linear and torsion motion vibrator according to any of claims 1-16, configured for rotating the rotors wy around their horizontal axis haj, such that rotors wy each rotate at a same angular velocity Oj around said horizontal axis haj.

18. The linear and torsion motion vibrator according to claim 2 and any of claims 3-17, wherein a centre of rotor driver (8) cmof the vibrator and a longitudinal axis of the monopile concur, and / or wherein at least one rotor driver (8) is each individually adapted to horizontally rotate axels haj at a first rotation frequency of 10-50 Hz (600-3000 rpm), preferably at 12-30 Hz, more preferably at 15-25 Hz, such as at 16-24 Hz, and / or wherein at least one rotor actuator assembly RAAij is each individually adapted to rotate the vibrator at a torsion frequency of 10-200 Hz (600-12000 rpm), preferably at 30-150 Hz, more preferably at 50-120 Hz, such as at 70-100 Hz and / or wherein the weights are 5-5000 gr, preferably 10-1000 gr, such as 30-600 gr, and / or wherein distance / radius ej is 1-50 cm, preferably 2-40 cm, such as 3-30 cm, and / or wherein the vibrator is configured to adjust at least one distance of ej and Rj, in particular wherein the vibrator is configured to adjust all distances of ej and Rj, and / or wherein the fixator (1) is configured to fix the vibrator outside to the monopile, inside to the monopile, over an edge of the monopile, and combinations thereof.

19. A method of driving a monopile into a soil, comprising providing a vibrator (100) according to any of claims 1-18, mounting the vibrator (100) on a monopile, and driving the monopile into the soil.

20. The method according to claim 19, wherein the vibrator is calibrated before driving the monopile into the soil.

21. The method according to claim 19 or 20, wherein the controller changes the rotational frequency ecu of the at least one pair (5,6) of unbalanced rotors (i,j), in particular increases or decreases said rotational frequency on, or maintains said rotational frequency on, in particular wherein a change is a result of a feedback loop.

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