EP4633925A1

EP4633925A1 - Large diameter pile driving method and system

Info

Publication number: EP4633925A1
Application number: EP23833417.1A
Authority: EP
Inventors: David ROODENBURG
Original assignee: Itrec BV
Current assignee: Huisman Equipment BV
Priority date: 2022-12-16
Filing date: 2023-12-15
Publication date: 2025-10-22
Also published as: KR20250139814A; CN120677056A; WO2024126844A1; JP2025541346A; AU2023395042A1

Abstract

Pile driving a large diameter steel pile (1) vertically into the ground. Use is made of a pile driving device (10) on a top end of the pile. The pile driving device comprises a drive head assembly (20) having an annular contact face (21) resting on the top end of the pile, and an annular anvil face above the annular contact face. A steel impact weight (30) has a mass of at least 100 tonnes. The impact weight (30) is lifted by means of the lift system (60) into a desired initial height position. A quick release mechanism (70) is operated to effect quick release of the lift system so that the impact weight falls down from said initial height position onto the anvil face (22) of the drive head assembly (20). The impact weight comprises, preferably is embodied as, a tubular impact weight which is made of steel.

Description

LARGE DIAMETER PILE DRIVING METHOD AND SYSTEM.

The present invention relates to the field of pile driving a hollow and open ended large diameter steel pile vertically into the ground, the pile having a cylindrical top portion with a top portion wall thickness between an inner diameter and an outer diameter, wherein the outer diameter is at least 5 meters into the soil. The invention is in particular of benefit for driving a monopile of an offshore wind turbine into the seabed. Practical embodiments which are nowadays envisaged include monopiles having a diameter between 5 and 12 meters, and lengths between 60 and 120 meters. A monopile may weigh more than 1000 tonnes, nowadays monopiles of about 2500 tonnes (12 meter outer diameter, 120 length) are proposed.

In present day practice for installation of a monopile generally use is made of a single so- called accelerated hydraulic hammer, which is a piling driving wherein the impact weight is downwardly accelerated by gas pressure, via a hydraulic arrangement, to reach an acceleration well above 1G (the normal acceleration under gravity). These known devices allow for an acceleration up to twice the rate of a free drop, so up to 2G. Such piling devices are nowadays available in configurations that are able to deliver more than 4000kJ per blow, even up to 5500 kJ per blow, e.g. the Menck MHU 4400S, or the IQIP IQ4 or IQIP IQ6 hammer, their practical use for driving of large diameter monopiles appears to suffer from various drawbacks.

In the practically known application for driving a monopile into the seabed the single hydraulic hammer is placed centrally on a head end assembly that rests with its contact face on the top of the monopile. The head end assembly has a very robust disc-shaped portion which spreads out the blow energy from the anvil face in the center of the head end assembly to the annular contact face which has a diameter that is as large as the diameter of the top end of the monopile. This requires a very sturdy design of the head end assembly.

Another approach for driving a large diameter pile, e.g. a monopile, has been proposed in W02006/010758. Herein multiple hydraulic hammer pile driving devices are placed on top of a single monopile. Each device has its own impact weight and associated acceleration mechanism based on gas pressure, via a hydraulic arrangement acting on the impact weight. Each hammer is mounted on a section of the open top end of the pile. This approach requires an extreme synchronisation of these hammer devices which is not practical. Alternative approaches for pile driving of a large diameter pile are proposed in

W02020/153838. Herein the drop weight falls solely under the influence of gravity, so at 1G. In embodiments, the single drop weight used for driving the pile has a mass of at least 50 tonnes, e.g. 100 tonnes, or even several hundreds of tonnes. In embodiments, the drop weight is composed of a support platform on which steel weight elements are stacked. The platform is guided by vertical pylons. In embodiments, the drop weight assembly is lifted by means of a lift system which comprises multiple hydraulic lift cylinders and an associated hydraulic pump. A quick release system comprises one or more quick release valves that are opened to allow rapid discharge of hydraulic liquid from the lift cylinders. The hydraulic liquid of the one or more lift cylinders may be circulated through a heat exchanger system so as to cool the hydraulic liquid, e.g. the heat exchanger being fed with seawater for cooling the circulated hydraulic liquid in case the pile is installed into the seabed.

The present invention aims to provide an alternative pile driving device for driving a large diameter pile into the soil, e.g. a monopile into the seabed. In particular, the invention aims to provide a pile driving device of limited complexity (e.g. in view of manufacturing), high reliability, an/or easy to integrate in the entire process of monopile installation.

According to a first aspect thereof the invention proposes a pile driving method for driving a hollow and open ended large diameter steel pile vertically into the ground, the pile having a cylindrical top portion with a top portion wall thickness between an inner diameter and an outer diameter, wherein said outer diameter is at least 5 meters, e.g. a monopile of an offshore wind turbine, into the soil, e.g. into the seabed, wherein use is made of a pile driving device that is arranged on a top end of the pile, which pile driving device comprises:

- a drive head assembly having an annular contact face resting on the top end of the pile, and an annular anvil face above the annular contact face,

- a steel impact weight which has a mass of at least 100 tonnes, e.g. more than 200 tonnes, which impact weight is vertically mobile above the annular anvil face of the drive head assembly,

- a vertical guide structure configured to vertically guide the impact weight, wherein the drive head assembly is configured for energy transfer assembly between the annular anvil face and the annular contact face for the transfer of energy from the falling impact weight to the annular contact face and thereby to the pile top,

- a lift system configured to bring the impact weight into an initial height position relative to the annular anvil face of the drive head assembly,

- a quick release system adapted to effect quick release of the lift system so that the impact weight falls down from said initial height position onto the anvil face of the drive head assembly, wherein the method comprising a repeated cycle wherein:

- the impact weight is lifted by means of the lift system into the initial height position,

- the quick release mechanism is operated to effect the quick release of the lift system so that the impact weight falls down from said initial height position onto the anvil face of the drive head assembly, wherein energy from the falling impact weight is transferred by said energy transfer assembly to the contact face of drive head assembly and thereby to the top end of the pile, so that the pile is driven deeper into the soil.

According to the first aspect of the invention the impact weight comprises or is embodied as a tubular impact weight which is made of steel.

In embodiments, the tubular impact weight has an inner and outer diameter such that, in vertical projection, the tubular impact weight overlaps with the wall thickness of the top portion of the pile. This arrangements achieves that the blow energy of the falling impact weight travels vertically through the head end assembly and then into the wall thickness of the top portion of the (mono)pile. This avoids undue stresses in the path of the blow energy and allows for optimum driving efficiency.

In embodiments, an acceleration mechanism is provided which accelerates the drop weight downward at an acceleration larger than 1G, e.g. adjustable between 1G and 2G. For example, multiple accelerator devices are provided in the pile driving device which are arranged in a circular array and engage on the tubular impact weight at distributed positions. For example, each of these multiple accelerator devices is based on the acceleration known from the mentioned hydraulic hammers, e.g. as shown in US4601349. For example, each accelerator device comprises a cylinder having a cylinder body and a piston/piston rod, wherein a pressurized gas filled chamber urges the piston/piston rod downwards. Compared to the disclosure of W02006/010758 wherein each accelerated hammer device has its own impact weight, the multiple accelerator devices now engage on a common impact weight. This is beneficial in view of the synchronization of the accelerator devices as they are now mechanically coupled via the sturdy impact weight.

In embodiments, the pile driving device is devoid of an acceleration mechanism, so that the impact weight drops under gravity in absence of further acceleration. Compared to the accelerated embodiment, this gravity based drop will in the inventive concept cause a relatively long duration of the energy transfer. This enhances pile driving efficiency and may contribute to a reduction of piling noise, which is of particular relevance for offshore pile driving.

Preferably, the impact weight is embodied as a tubular impact weight which is made of steel, e.g. cast, or welded from steel plates, e.g. welded of semi-circular steel plates, e.g. having a wall thickness between 10 and 20 centimetres.

In embodiments, the tubular impact weight is of circular cross-section, e.g. welded of semicircular steel plates. In other embodiments, the tubular impact weight is welded of flat plates to form a polygonal cross-section, e.g. a 16-sided or 32-sided polygon.

Preferably, the steel tubular impact weight has an inner peripheral side and an outer peripheral side with a wall thickness in between, so made of solid steel between the inner and outer peripheral side.

In an embodiment, the tubular impact weight has a lower section of a first wall thickness and an upper section of a second wall thickness, the second wall thickness being greater than the first wall thickness.

Preferably, the lift system connects to the upper portion of the tubular impact weight, e.g. lift cylinders having a piston rod of which an end is connected to the upper section of the tubular impact weight.

Preferably, the tubular impact weight is devoid of any internal bracing members extending across the opening defined by the tubular impact weight. This, e.g., avoids undue local stresses where such bracing members adjoin the tubular part. In embodiments, the tubular impact weight has an inner and outer diameter such that, in vertical projection, the tubular impact weight overlaps with the wall thickness of the top portion of the pile. This arrangements achieves that the blow energy of the falling impact weight travels vertically through the head end assembly and then into the wall thickness of the top portion of the (mono)pile. This avoids undue stresses in the path of the blow energy and allows for optimum driving efficiency.

In practical embodiments, as in the prior art, the top portion of the pile is open, just like the bottom portion.

In embodiments, the tubular impact weight is hollow and open ended, so effectively embodied as an impact weight ring of solid steel.

In embodiments, the pile driving device including the tubular impact weight has an open ended central passage, e.g. to allow for access from above through the pile driving device to the inside of the monopile. Preferably the central opening has a diameter of at least 2 meters, e.g. at least a diameter corresponding to 50%, e.g. to at least 75% of the inner diameter of the top portion of the pile. This allows for ample access from above through the pile driving device to the inside of the monopile, which can be of practical benefit.

For example, during pile driving or in a subsequent step prior to removal of the pile driving device from the (mono)pile, other activities are performed that involve accessing the inside of the pile via this central passage. For example, the central passage is used for access to the inside of the pile by one or more of: jetting equipment, soil removal equipment, drilling equipment, vibrating equipment, grouting equipment including lines related to such equipment. For example, the passage is used for access of a stone removal device, e.g. when the pile hits a sizable stone during pile driving.

For example, the central passage is used to allow drilling equipment to down to the seabed along the pile. This is especially advantageous when the pile has hit a large rock embedded in the seabed during the pile driving operation. Normally, the pile has to be lifted and removed from the installation site such that drilling equipment can be used to remove the stone or other obstruction. By having a central passage the drilling equipment can be lowered to the seabed and remove the obstruction without the need of lifting and removing the pile. For example, the central passage is used for engaging a pile lifting tool with the top portion of the pile, wherein the pile lifting tool is configured to be introduced into the central passage and then to engage of the top portion of the pile.

For example, the pile has an inward top flange, e.g. with bolt holes. Preferably, the contact face is position directly above the top portion wall of the monopile so as to avoid that the top flange is strained (too much) during the pile driving.

For example, during a pile run, if the pile driver is closed, all the air inside of the pile and pile driver is compressed as the pile runs deeper in the seabed, this increases the pressure inside of the pile and pile driver. This pressure can become high enough to lift the pile driver from the top end of the pile, this can cause significant damage to the pile driver, the pile and the surrounding structures as well as forming a danger for the crew. By having an open ended central passage, it allows the air to escape the pile and pile driver such that there is no pressure build, increasing the safety of the operation.

For example, the central passage can be used to reduce the chance of a pile run. The central passage allows for the use of a pile run prevention member which can be arranged inside of the central passage and which is configured to engage a flange at the top end of the pile.

In an embodiment, the pile run prevention member comprises a damping member which is suspended from the pile driver or, optionally a crane, and an engagement member which is suspended from the damping member and is configured to engage the inward top flange of the pile.

In an alternative embodiment, the pile run prevention member is embodied as an cable with an first and a second end, wherein the first end is suspended from the pile driver or, optionally, a crane, and wherein the second end is provided with an engagement member which is configured to engage the inward top flange of the pile, wherein during normal operation the cable is slack and when the pile is driven deeper into the ground by the pile driver the length of the cable is increased such that the cable does not exert a force on the pile, only when a pile run occurs the cable becomes taught and exerts and upwards force on the pile preventing a pile run.

In embodiments, the drive head assembly is configured to leave a portion of the inward top flange exposed. This arrangement may, in embodiments, to allow gripping of the flange by a gripper of a pile lifting tool. In embodiments, the drive head assembly has an inner diameter that is greater than the inner diameter of the inward top flange so that a peripheral portion of the flange is exposed.

In embodiments, the tubular impact weight has a wall thickness of between 10 and 20 centimetres.

In embodiments, the tubular impact weight has a height of between 4 and 12 meters, e.g. between 6 and 10 meters, wherein, preferably, the tubular impact weight has a wall thickness of between 10 and 20 centimetres.

In embodiments, the lifting means are configured to provide a vertical distance between the anvil face and the initial height of the impact weight of at most 2 meters, e.g. of about 1 meter.

In embodiments, the pile driving device has an outer housing extending coaxially about the tubular impact weight, the outer housing having an open lower end which rests on the drive head assembly.

Preferably, the outer housing is peripherally closed.

In practical embodiments, the outer housing has an open top end and has a central passage of a diameter at least corresponding to 50%, more preferably at least 75%, of the inner diameter of the top portion of the pile.

In practical embodiments, the lift mechanism comprises multiple hydraulic lift cylinders.

In embodiments, generally as disclosed in US4601349 for example, the lift cylinders are integrated with the acceleration mechanism which accelerates the drop weight downward at an acceleration larger than 1G, e.g. adjustable between 1 G and 2G.

Preferably, the hydraulic lift cylinders are arranged in a circular array above the tubular impact weight, more preferably, so as to leave open a central passage of a diameter at least corresponding to 50%, more preferably at least 75%, of the inner diameter of the top portion of the pile. In practical embodiments, the quick release system comprises one or more quick release valves that are opened to allow rapid discharge of hydraulic liquid from the lift cylinders. For example, the lift cylinders are connected to a common hydraulic discharge duct assembly that is governed by a single quick release valve, or two sets of lift cylinders are each connected to a respective common hydraulic discharge duct assembly, e.g. each controlled by a respective quick release valve. These measures may reduce any lagging of discharge of hydraulic liquid from a lift cylinder relative to one or more other lift cylinders.

For example, the multiple hydraulic lift cylinders are arranged on a top portion of the outer housing, e.g. on an inward flange of the outer housing.

In an embodiment, the vertical guide structure comprises impact weight engagement members which are configured to engage the tubular impact weight, e.g. on the outside thereof, wherein preferably the impact weight engagement members are configured to engage the impact weight with a pre-load.

In practical embodiments, the vertical guide structure comprises roller assemblies, each roller assembly comprising one or more horizontal axis rollers that engage the tubular impact weight, e.g. on the outside thereof. For example, the roller assemblies are mounted to the outer housing. For example, there is a lower group of roller assemblies and a higher group of roller assemblies, with the vertically mobile impact weight being always guided by the roller assemblies of these lower and higher groups.

In embodiments, the roller assemblies are configured to press the one or more rollers against the tubular impact weight with a pre-load. This, for example, allows for accurate vertical guiding and/or for absorbing peak loads caused by rebound of the impact weight.

In embodiments, the drive head assembly comprises a resilient material cushion member, e.g. an annular resilient material cushion member, which resilient material cushion member is disposed between the anvil face and the contact face.

In embodiments, the energy transfer assembly of the drive head assembly comprises one or more spring devices and/or one or more damper devices that are effective between the anvil face and the contact face. The one or more spring devices and/or one or more damping devices are configured to lengthen the duration of the energy transfer which increases the efficiency and lowers the noise generation. In embodiments, the drive head assembly comprises multiple spring devices and/or multiple damper devices which are arranged in a circular array in the drive head assembly, e.g. embodied as integrated spring and damper devices.

In embodiments, the drive head assembly comprises multiple cylinder devices which are arranged in a circular array in the drive head assembly, each having a cylinder body, a piston, and a chamber delimited by the piston, wherein the chamber is filled with liquid and/or gas, e.g. oil, and wherein optionally the chambers of the cylinder devices are interconnected.

In an embodiment, the multiple cylinder devices are arranged in a circular array in the drive head assembly, wherein the cylinder devices are arranged between an annular anvil member forming the anvil face and a bottom member forming the contact face. The cylinder devices are made of a metal, e.g. steel or titanium.

In an embodiment, the multiple cylinder devices are evenly arranged along the circumference of and on the top flange of the pile, wherein each cylinder device is provided with an anvil member at the top end thereof and a bottom member forming the contact face between the cylinder device and the top flange of the pile.

In an embodiment, the cylinder device comprises a cylinder body, a piston, and a single chamber which is delimited by the cylinder body and the piston. Preferably, the chamber is filled with a liquid, Oil is preferably used to fill the chamber due to the relatively high elasticity of oil, e.g. compared to water.

Preferably, the piston is embodied as a hollow piston. The piston has a central cavity extending from an opening at the bottom end of the piston to a blind end at the top of the piston. The central cavity is delimited by an annular piston wall and a top wall of the piston. The central cavity forms a part of the single chamber. By using a hollow piston, the weight of the piston is reduced and the volume of liquid, e.g. oil, is increased. This leads to enhanced efficiency of the energy transfer.

In an embodiment, the bottom end of the piston wall is chamfered. During pile hammering, piston will be very quickly displaced through the oil due to the oil being compressed, this can create cavitation zones near the lower end of the piston wall, which is a cause for degradation of the oil and may reduce the efficiency of the energy transfer. By using a chamfered bottom end of the piston wall, the piston can be easier displaced through the oil, e.g. the piston wall is more hydrodynamic, this reduces the chance of cavitation zones occurring in the oil.

In an embodiment, a resiliently compressible element is arranged on top of the top end of the piston. The element being embodied to act as a cushion, e.g. a slab or disc of an elastically compressible material, or a metallic element, e.g. one or more disc springs. By providing this element on top of the piston, so as to act between the piston and the impact weight, the piston is more gradually accelerated as compared to when no such element would be present.

In embodiments, the pile driving device comprises a sleeve that extends from the head end assembly down along a top section of the pile.

In an embodiment, the pile driving device is connected to lifting tool of a crane during pile driving, wherein multiple shock absorbers are mounted to a top of the pile driving device, e.g. to the outer housing thereof, which multiple shock absorbers connected to a spreader structure, e.g. two shock absorbers connect to a spreader bar, at a top end of the shock absorbers, and wherein the spreader structure is connected to the lifting tool, e.g. via two slings.

In an embodiment, the method is performed at sea, e.g. for the installation of a monopile, wherein use is made of a vessel comprising a pile gripper device that is operated to hold the pile vertical during pile driving, e.g. a motion compensating pile gripper.

In embodiments, a vibratory device is employed in conjunction with the pile driving device.

For example, the vibratory device is configured for generating an alternating force about a vertical axis of the pile at a vibration frequency in order to vibrate the pile about the axis and to reduce friction between the pile and the soil, e.g. the seabed.

For example, the vibratory device is configured for generating vertical vibrations to drive the pile into the soil. This may be combined, in embodiments, with the vibration of the pile about the vertical axis to reduce friction between the pile and the soil, e.g. the seabed.

For example, the vibratory device is mechanically separate from the pile driving device described herein., so that the vibratory device is not or in limited manner subject to the impacts caused by the impact weight. For example, the vibratory device is configured to be mounted within the top portion of the pile, e.g. ahead of placing the pile driving device on the pile. When present, the central passage of the pile driving device may provide access to the vibratory device, e.g. in view of feeding energy to the vibratory device, e.g. for hydraulic lines that supply hydraulic liquid to motors of the vibratory device.

For example, the vibratory device is supported by means of a floating support which is configured to allow for a range of floating movement of the vibratory drive along the vertical axis in order to prevent the direct transfer of impacts exerted by the pile driving device to the vibratory drive. For example, the floating support is configured to dampen the impact forces, for example one or more resilient bodies, e.g. one or more springs or cylinders, are provided to support the vibratory drive in vertical direction.

For example, the vibratory device is connected to an inward flange of the pile and/or clamped inside the top portion of the pile, e.g. using hydraulic friction clamps, e.g. wedge clamps.

For example, the vibratory device is only connected to the pile when the pile driving device does not exert impacts on the pile. This avoids undue mechanical loads on the vibratory device.

For example, the vibratory device is used in a first stage of driving the pile into the soil and the pile driving device with the impact weight is used in a second stage of driving the pile into the soil. This may, for example, reduce the overall noise production of the installation of the (mono)pile.

For example, the vibratory device is suspended independently, so not mechanically attached to the pile driving device. For example, the vibratory device is suspended from a crane, e.g. the same crane from which the pile driving device is suspended, e.g. via the described shock absorber(s) and possibly spreader structure. Optionally, the vibratory device is suspended from the spreader structure as discussed herein, e.g. via a winch arrangement.

In an embodiment, a lower part of the impact weight comprises one or more spring devices and/or one or more damper devices that make contact with the anvil face.

In an embodiment, the impact weight comprises bores which extend from the lower portion of the impact weight in the height direction of the impact weight, wherein the bores are distributed along the circumference of the impact weight. The length of the bores are between 50-90% of the height of the impact weight, preferably between 60 - 80% of the impact weight height , An elongated member, e.g. a bar or rod, is received inside of the bore and extends along the entire length of said bore, such that the lower end the elongated member extends beyond the lower portion of the impact weight and makes contact with the anvil face. Due to the length of the elongated member it acts like a spring, this causes the energy transfer to be of a longer duration increasing the efficiency and lowering the noise generation. For example, the elongated member is received in the bore with some play.

The size, shape, and material of the impact weight makes it difficult to manufacture an impact weight which comprises of only one part. To make the manufacturing process of the impact weight easier and faster the impact weight can be made out of multiple parts which are then connected to form the impact weight.

In an embodiment, the impact weight comprises two or more ring members, e.g. each made of steel, e.g. of a steel casting or welded steel, which ring members are stacked on top of each other to form the impact weight. In an embodiment, each ring member of the impact weight comprises two or more ring segments, e.g. semi-circular ring segments, e.g. more than four ring segments, which together make up the ring member.

In an embodiment, the multiple ring members, e.g. the ring segments thereof, are vertically connected to each other using vertical fasteners, e.g. bolts.

In an embodiment, the impact weight comprises two or more ring members, which are stacked on top of each other, wherein each ring member comprises two or more ring segments, wherein the ring segments of the adjoining ring members are circumferentially offset, such that the ring segments each overlap with at least two adjacent ring segments. Vertical fasteners, e.g. long bolts, can be extended through aligned holes in the ring segments in order to interconnect the ring segments and ring members to form the tubular impact weight.

In an embodiment, adjoining ring segments are welded to each other to form a ring member, with the multiple ring members being interconnected by vertical fasteners extending through aligned holes in the ring members.

When the impact weight falls down and makes contact with the anvil face of the drive head assembly, the impact weight will want to expand in the radial direction, e.g. the lower portion thereof, which causes enormous tangential stresses in the impact weight. These repeated tangential stresses acting on the impact weight can cause fatigue which could lead to damage and failure. To reduce the tangential stress the impact weight may be embodied such that the impact weight has multiple zones which provide a flexibility in tangential direction. The tangential flexibility of these zones allows the impact weight to expand more freely upon contact with the anvil face which reduces the peak tangential stress. To achieve these tangential flexible zones multiple embodiments of the impact weight are envisaged. In an embodiment, the impact weight comprises two or more ring segments, e.g. circular arc segments or quadrilateral segments, wherein adjoining segments are connected to each other by a resilient zone, which may also be called a spring zone. The resilient zone may bridge a gap between adjacent ring segments, e.g. being embodied as a folded steel component.

In an embodiment, the impact weight comprises one or more ring members each assembled of two or more ring segments, e.g. circular arc segments or quadrilateral segments, wherein the ring segments have an inner wall surface, an outer wall surface, and a wall thickness, wherein adjoining ring segments are connected to each other by a weld, e.g. a vertical weld, wherein the welds in a ring member extend alternately from the inner wall surface and the outer wall surface, and wherein each of the welds extends only partly between the inner wall surface and outer wall surface such that- at the join of ring segments - a groove extends.

The tangential stresses caused by the falling down of the impact weight can cause structural damage especially at the circumferential welds of the drop weight, these welds are usually less resistant to stress and fatigue compared to the rest of the impact weight. To reduce the stress acting on the circumferential welds the impact weight comprises of multiple quadrilateral segments that form a polygonal shape. This reduces the stress on these welds by positioning the circumferential welds further away from highly stressed areas.

For example, wherein the segments are embodied as quadrilateral segments, such that the two or more segments form a polygon, e.g. a hexadecagon comprising of 16 quadrilateral segments.

In an embodiment, the impact weight comprises a single circular segment, the segment having an inner wall surface and an outer wall surface. For example, the single circular segment has axial slots evenly distributed along the radius and height of the impact weight. The invention will now be explained with reference to the drawings. In the drawings:

Fig. 1A shows a part of a monopile and a pile driving device according to a first embodiment of the invention in vertical cross-section;

Fig. 1 B shows a part of figure 1 A on a larger scale,

Fig. 2 a top view onto the arrangement of figure 1 ,

Fig.3 the tubular impact weight of the pile driving device of figure 1 ,

Fig. 4 the outer housing of the pile driving device of figure 1 ,

Fig. 5 the head end assembly of the pile driving device of figure 1 ,

Figs 6a, b a roller assembly of the pile driving device of figure 1 ,

Fig. 7 illustrates the handling of the pile driving device of figure 1 by means of a crane,

Fig. 8a illustrates another embodiment of a head end assembly,

Fig. 8b shows an embodiment of the cylinder device,

Fig. 9 shows a part of a monopile and of a pile driving device in vertical cross-section wherein the head end assembly of figure 8a is included,

Fig. 10 schematically illustrates the application of a vibratory device,

Fig. 11 a - f show alternative embodiments of the tubular impact weight,

Fig. 12a shows an embodiment of a pile run prevention member which comprises a damping member, and

Fig. 12b shows an embodiment of a pile run prevention member embodied as a cable with a first and a second end.

With reference to figures 1A-7 a first embodiment of the invention will be described. The figures are on scale, the figures show that a monopile 1 having an outer diameter of 8 meter is driven into the seabed. The person shown in figure 1A is just shown as reference to allow to understand the size of the components shown by way of example.

The monopile 1 is a hollow and open ended large diameter steel monopile 1 that is to be driven vertically into the seabed in order to serve as a foundation for an offshore wind turbine.

The pile may have a constant diameter over its length, but can also have another design. For example, the monopile has a lower portion of a first largest diameter, a tapering portion, and a top portion 1a of a second smallest diameter. For example, the second smallest dimension is at least 5 meter, e.g. 8 meters as shown here. The monopile 1 has a cylindrical top portion 1a with a top portion wall thickness between an inner diameter and an outer diameter. For example, as shown here, the wall thickness of the top portion 1a is 8 centimetres. The top portion is open at its top end.

The pile 1 has an inward top flange 1 b, here with bolt holes, in view of connecting a wind turbine mast to the monopile 1.

As is known in the art, the monopile can be of a length between 60 and 120 meters. Diameters at the bottom end of between 8 and 12 meters are known or proposed. The weight of a monopile can be well over 1000 tonnes, e.g. between 2000 and 3000 tonnes. Wall thicknesses between 8 centimetre and 15 centimetre are known or proposed.

The figures 1 - 7 illustrate a pile driving device 10 that is configured to be arranged on the top end of the pile 1.

The pile driving device 10 comprises:

- a drive head assembly 20 having an annular contact face 21 which is configured for resting on the top end of the pile 1 , and an annular anvil face 22 above the annular contact face 21,

- a steel impact weight 30 which has a mass of about 200 tonnes in the depicted example, which impact weight is vertically mobile above the annular anvil face 22 of the drive head assembly 20,

- a vertical guide structure 40 configured to vertically guide the impact weight 30, wherein the drive head assembly 20 is configured for energy transfer between the annular anvil face 22 and the annular contact face 21 for the transfer of energy from the impact weight 30 to the annular contact face 21 and thereby to the pile top 1a,

- a lift system 60 configured to bring the impact weight 30 into an initial height position relative to the annular anvil face 22 of the drive head assembly 20,

- a quick release system 70 adapted to effect quick release of the lift system 60 so that the impact weight 30 falls down from said initial height position onto the anvil face 22 of the drive head assembly 20. The pile driving device 10 is operable in a repeated cycle wherein:

- the impact weight 30 is lifted by means of the lift system 60 into the initial height position,

- the quick release mechanism 70 is operated to effect a quick release of the lift system 60 so that the impact weight 30 falls down from said initial height position onto the anvil face 22 of the drive head assembly 20, wherein energy from the falling impact weight 30 is transferred to the contact face 21 of drive head assembly and thereby to the top end of the pile, so that the pile is driven deeper into the soil.

As illustrated, the impact weight 30 is embodied as a tubular impact weight which is made of steel. The tubular impact weight is hollow and open ended.

The wall thickness of the tubular impact weight 30 is, on average, somewhat greater than the wall thickness of the cylindrical wall of the top portion 1a of the monopile 1 in order to obtain the desired weight of the impact weight 30.

The height of the tubular impact weight 30 is more than 4 meters, for example between 4 and 12 meters, e.g. between 6 and 10 meters. In the depicted embodiment, for a monopile with a top end of 8 meters diameter and an impact weight diameter of 8 meters, the height is approximately 7.5 meters.

The diameter of the tubular impact weight 30 generally corresponds to the diameter of the monopile top portion 1 a, so that the mass of the impact weight 30 is generally positioned in a vertical projection onto the cylindrical wall of portion 1 a. This allows for optimal energy transfer.

The tubular impact weight has diameter such that, in vertical projection, the tubular impact weight overlaps with the wall thickness of the top portion 1 a of the pile 1 . The tubular impact weight has a wall thickness of between 10 and 20 centimetres.

As shown here, the contact face 21 is positioned directly above the top portion wall 1 a of the monopilel so as to avoid that the top flange 1 b is strained too much during the pile driving.

It is illustrated, that the drive head assembly 20 is configured to leave a peripheral portion of the inward top flange 1b exposed, e.g. so that the bolt holes are still accessible. This arrangement may, in embodiments, to allow gripping of the flange 1 b by a gripper of a monopile lifting tool. The lifting means 60 are configured to provide a vertical distance between the anvil face 22 and the initial height of the impact weight 30 of at most 2 meters, here of about 1 meter maximum. The lifting means 60 are configured to adjust the initial height in order to adjust the energy per blow of the impact weight, e.g. up to a maximum height of 1 meters.

The pile driving device has an outer housing 50 which extends coaxially about the tubular impact weight 30. The outer housing has an open lower end that here rests on the drive head assembly 20.

The outer housing 50 is made of steel, e.g. welded.

The outer housing 50 has an open top end. Optionally a (re) movable closure is associated with the open top end of the outer housing 50, e.g. a removable lid.

The outer housing 50 is peripherally closed, e.g. to form a noise barrier. For example, not shown, sound dampening liner material is present on the side(s) of the housing to reduce emission of noise from the housing 50 while pile driving takes place.

The outer housing 50 has an open top end and has a central passage of a diameter at least corresponding to 50%, more preferably at least 75%, of the inner diameter of the top portion of the pile.

The pile driving device has an integrated lift and acceleration mechanism 60 which comprises multiple integrated lift and acceleration devices 61. These devices are distributed in a circular array, for example on a top portion of the outer housing 50, here mounted on an inward top flange 51 of the outer housing 50. For example, between 6 and 12 of the devices 61 are present on the outer housing 50. For example, the devices 2 allow for an adjustable acceleration of the drop weight of up to 2G. A greater acceleration is not excluded, yet would require an even heavier design of the pile driving device, e.g. the outer housing 50 thereof.

The devices 61 are mounted vertically on the outer housing 50.

The devices 61 each connect to an upper portion of the tubular impact weight 30.

The devices 61 has a piston and piston rod 62 that extends down from the cylinder body 63 which is affixed to the outer housing 50. The piston rods 62 have an end that is connected to the upper section of the tubular impact weight. In this example, the impact weight 30 has holes 31 along the upper rim thereof, wherein a clevis of the piston rod is fitted over the upper rim and is connected via a pin to the impact weight 30.

A lower chamber 64 defined by the piston is the hydraulic lift chamber. An upper chamber 65 defined by the piston is the pressurized acceleration chamber, e.g. filled with pressurized gas, e.g. from gas buffer 66. For example, as known in the art, a gas pressure adjusting valve assembly is provided, which allows to set the desired gas pressure and thereby the desired acceleration of the impact weight 30.

The chambers 64 of the devices 61 may be connected to a common duct arrangement 67 for feeding hydraulic liquid to the chambers 64 and/or for quick discharge of hydraulic liquid, e.g. water, from the chambers 64. For example, the common duct for multiple chambers 64, possibly all chambers 64, connects to one or more quick release valve 70 that is/are opened to allow rapid discharge of hydraulic liquid from the lift chambers 64 of the devices 61 . A hydraulic system is provided, e.g. including one or more hydraulic pumps 68, for the lift operations.

In another embodiment, the quick release is embodied in the form of an operable connector device that connects a lift cylinder to the impact weight, e.g. a mechanical latch, magnetic connector, a friction clamp, etc.

In order to ensure that the impact weight 30 accurately drops onto the anvil face in a vertical direction, the vertical guide structure 40 comprises roller assemblies 41 , 42 which are mounted on the outer housing 50. Each roller assembly 41 , 42 comprises horizontal axis rollers 43, here two per assembly, that engage the tubular impact weight, here the outer peripheral side thereof.

These assemblies 41 , 42 are configured to press the one or more rollers 43 against the tubular impact weight 30 with a pre-load. This is achieved by a biasing assembly 44 in each roller assembly.

It is illustrated that the rollers 43 have a resilient material outer lining, which engages the outer side of the steel impact weight 30. As can be best seen in figure 1A the drive head assembly 20 comprises a resilient material cushion member 23, here an annular resilient material cushion member, which resilient material cushion member 23 is disposed between the anvil face and the contact face.

It is illustrated that the drive head assembly 20 is composed of a metal ring member 24 of which the bottom side delimits the contact face 21. An open-top groove is formed in the metal ring member 24, in which the annular cushion member 23 is received.

It is illustrated that the anvil face 22 is formed by a metal anvil ring that rests on the annular cushion member 23.

It is illustrated that the cushion member 23 has a thickness of about the thickness of the impact weight 30 and a height that is at least the thickness of the member 23.

For example, a cooling arrangement is provided for the annular cushion member 23, e.g. using sprays of water, liquid cooling ducts in the head end assembly, etc.

For example, the cushion member 23 is composed of stacked layers of metal and synthetic materials, e.g. the metal facilitating the removal of heat from the cushion member 23.

For example, the cushion members 23 is composed of metallic elements, e.g. fibres, embedded in synthetic material, e.g. the metal members facilitating the removal of heat from the cushion member 23.

For example, as shown, the annular cushion member 23 has vertical sides that are higher than the thickness of the cushion member, which facilitates removal of heat from the cushion member.

Removal of heat from the cushion member may serve to extend the operational life of the member 23.

It is illustrated that the pile driving device 1 comprises a sleeve 80 that extends from the head end assembly 20 down along the top section 1a of the pile 1.

A shown, the entire pile driving device 10 is embodied such that access is possible to the inside of the monopile 1 , even during pile driving. A central passage 90 effectively extends from above through the lower end of the device 10 and has a diameter of at least 2 meters, more preferably at least 50%, more preferably at least 75% of the diameter of the pile 1 .

For example, as shown, the passage 90 has a diameter at least corresponding to the diameter of the opening defined by the inward flange 1 b of the pile.

As preferred, the flange 1 b remains accessible via this passage 90.

Due to the central passage 90 of significant cross-section, here over 75% of the diameter of the monopile, other equipment can be employed during the pile driving, e.g. a jetting system which requires passage of significant high pressure jet lines via passage 90 into the inside of the monopile 1. The housing 50 may be configured to provide support for such additional equipment. Also, in embodiments, the flange 1 b may be used to provide support for additional equipment involved in pile driving, e.g. jetting equipment, vibrating equipment, etc.

The significant passage 90 may also be of benefit when the pile driving device 10 is stored, e.g. on deck of a vessel, e.g. allowing to place a hydraulic power unit associated with the pile driving device 10 inside the passage 90 in the stored arrangement.

As can be best seen in figure 7, the pile driving device 1 can be configured to be connected to lifting tool of a crane during pile driving. Shock absorbers 90 are mounted to a top of the pile driving device, here to the outer housing 50 thereof, which multiple shock absorbers connected to a spreader structure 100, here two shock absorbers connect to a spreader bar, at a top end of the shock absorbers. The spreader structure is connected to the lifting tool, e.g. a crane hook, here via two slings 101.

With reference to figures 8 and 9 a different version of the pile driving device and method of the invention will be discussed. Herein components that correspond to components shown in the figures 1 - 7 are denoted with the same reference numeral.

In figures 8 head end assembly 20’ is shown. This assembly 20’ has multiple cylinder devices 200 which are arranged in a circular array in the drive head assembly 20’. For example, between 20 and 60 cylinder devices 200 are present in the assembly 20’. For an 8 meter diameter pile driving device as shown, the number may be around 40.

The cylinder devices 200 are arranged between an annular anvil member 210 forming the anvil face 22 and a bottom member 215 forming the contact face 21. Each cylinder device has a cylinder body 201 , here all integrated in a steel annular head end body 202 that forms all cylinder bodies. Each cylinder device 201 has a single acting piston and piston rod assembly 203, and a chamber 204 delimited by the piston. The chambers 204 are all completely filled with a liquid in this example, e.g. with water. The volume of liquid is, preferably, adjustable. In an embodiment, all chambers 204 are interconnected.

For example, each piston of a device 200 has a diameter of between 20 and 50 centimeters.

The multiple cylinders devices 200 having a chamber that is filled with liquid, e.g. water, effectively act as springs for the impact of the impact weight 30 onto the anvil face 22. Herein, the liquid pressure may rise to an enormous value, e.g. to above 400 bars, e.g. approximately 600 bars.

In an embodiment, schematically shown in figure 8b, the cylinder device comprises a cylinder body 203b, a piston 203a and a single chamber 203c which is delimited by the cylinder body 203b and the piston 203a. The chamber 203c being filled with a liquid, e.g. an oil.

The piston 203a is embodied as a hollow piston. The hollow piston has a central cavity extending from an opening at the bottom end of the piston, wherein the central cavity is delimited by an annular downward extending piston wall 203d. The central cavity forms a part of the single chamber.

The bottom end of the piston wall 203d is, as preferred, chamfered.

A resilient element 203e, e.g. a solid compressible material element and/or a metallic resilient element, is arranged on top of the top end of the piston 203a.

In an embodiment, in view of the enormous maximum pressure that occurs within the chambers 204, leakage of liquid along the piston and piston rod assembly could be allowed instead of attempting to prevent leakage by a complex sealing arrangement. Herein, it is envisaged that a replenishment circuit for liquid to the chambers 204 is provided, e.g. of water, which feeds liquid to the chambers 204 so as to compensate for leakage. For example, leakage in the order of 1 liter per chamber 204 per blow is envisaged. In particular when the liquid is water, the leakage is not objectionable from an environmental perspective. If the liquid is an oil, as preferred for its elasticity, the leaked oil is to be collected, e.g. collected via one or more gutters, and fed to the replenishment circuit. In an embodiment, the annular anvil member 210 is absent, so that the totality of the piston tops form the annular anvil face on which the steel impact weight 30 drops.

In an embodiment, the cylinder devices 200 are arranged at the lower end of the impact weight 30, preferably each device 200 with the piston thereof extending downward. Herein, for example, the impact weight 30 is either embodied as a single tubular ring segment or the impact weight 30 comprises multiple ring segments 32, wherein the one or more cylinder devices 200 are arranged at the lower end of each ring segment 32.

In figure 7 it is also shown that the outer housing 50 rests on the top of the head end assembly 20’, so effectively on a part that is integral with or formed by the annular anvil member 210.

The sleeve 80 extends from the outer housing 50 downwards, about the head end assembly 20”and down along an upper portion 1a of the monopile 1.

Upon an impact of the impact weight 30 the head end assembly 20’ transfers the blow with some spring action to the cylindrical wall of the top end of the monopile. As shown, in embodiments, the contact surface 22 is arranged vertically above this cylindrical wall so that energy is transferred vertically from the impact weight 30 into this wall without undue loads of the flange 1 b.

In embodiments, as illustrated in figure 10, the system further comprises a vibratory device 300.

The figure 10 shows that the vibratory device 300 is suspended independently, so not mechanically attached to the pile driving device 10.

Preferably, the passage 90 is dimensioned such that the device 300 can be moved through the passage 90, e.g. for removal thereof without needing to remove the device 10 from the pile 1.

Preferably, the vibratory device has a clamping mechanism operable to clamp the device 300 to the pile 1 , e.g. with hydraulically operated clamps 306 that cause a friction fit with the inside of the pile 1. One or more rotating excenter mass units 307, as known in the art, cause the vibrations that are desired.

The vibratory device 300 is mechanically separate from the pile driving device 10 and can be selectively disconnected from the pile 1 as well, so that the vibratory device 300 is not or in limited manner subject to the impacts caused by the impact weight 30.

The figure 10 shows that the vibratory device 300 is suspended from a crane, here via cables 301e.g. the same crane from which the pile driving device is suspended, e.g. via the described shock absorber(s) 90 and possibly spreader structure 100.

Optionally, the vibratory device 300 is suspended from the spreader structure 100, e.g. via a winch arrangement.

For example, the vibratory device 300 is configured for generating an alternating force about a vertical axis of the pile at a vibration frequency in order to vibrate the pile about the axis and to reduce friction between the pile and the soil, e.g. the seabed.

For example, the vibratory device 300 is configured for generating vertical vibrations to drive the pile into the soil. This may be combined, in embodiments, with the vibration of the pile about the vertical axis to reduce friction between the pile and the soil, e.g. the seabed.

The central passage of the pile driving device also provides access to the vibratory device, e.g. in view of feeding energy to the vibratory device, e.g. for hydraulic lines that supply hydraulic liquid to motors of the vibratory device.

For example, the vibratory device 300 is only connected to the pile 1 when the pile driving device 10 does not exert impacts on the pile. This avoids undue mechanical loads on the vibratory device.

For example, the vibratory device 300 is used in a first stage of driving the pile into the soil and the pile driving device 10 with the impact weight 30 is used in a second stage of driving the pile 1 into the soil. This may, for example, reduce the overall noise production of the installation of the (mono)pile.

Figure 11 a shows a longitudinal cross section of an embodiment of the impact weight 30, wherein the impact weight comprises five ring members 30a - 30e, which are stacked on top of each other to form the impact weight 30. Each ring member 30a - 30e comprises multiple ring segments 32. The ring segments 32 of adjacent ring members 30a-30e are not vertically aligned such that the ring segments overlap with at least two vertically adjacent ring segments. Vertical fasteners 33, e.g. bolts, are used to connect the adjacent ring members and adjacent ring segments to each other.

Figure 11 b shows a transverse cross section of the impact weight 30, wherein the ring segments 32 are each semi-circular, such that the ring members 32 form a ring member of a tubular impact weight. Each ring segment is provided with multiple, here three, holes 34. When ring members are stacked onto one another, the holes 34 align, and a vertical fastener 33 can be inserted through a set of aligned holes. For example, the fastener 33 is a long bolt.

Figure 11 c shows an alternative embodiment of the impact weight 30, wherein the impact weight 30 comprises three ring segments 32 which are connected to each other using resilient zones 35 or spring zones 35, which bridge the small distance between the adjacent ring segments 32. For example, the resilient zones 35 are embodied as steel components, e.g. welded components, e.g. with a folded section of which an example is shown here. It is illustrated that each resilient zone 35 has an inward folded section, but other configurations are also contemplated.

Figure 11 d shows an alternative embodiment of the impact weight 30, wherein the impact weight 30 comprises multiple segments 32. The ring segments have an inner and an outer wall surface and a wall thickness. Adjoining ring segments are connected to each other by welds, here vertical welds. The welds extend alternately from the inner wall surface and the outer wall surface. Each weld does not extend through the wall thickness of the ring segments, but extends only partly between the inner and outer wall surface. As a result alternating vertical grooves are formed. As explained, this alternating arrangement of partial welds reduces tangential peak stresses in the impact weight.

Figure 11 e shows an alternative embodiment of the impact weight 30, wherein the impact weight is provided with evenly distributed axial slots 37, the slots being spaced in tangential direction.

Figure 11f shows an embodiment of the impact weight 30, wherein the impact weight comprises sixteen ring segments 32 which are each embodied as a quadrilateral segment, such the connected ring segments 32 form a hexadecagon. Here the ring segments are welded to each other, but other arrangements (as discussed herein) are also possible. The 16 sided polygonal cross-section may be seen as an approximation of the circular designs. In another embodiment, in view of the diameter of the weight 30, a 32-sided polygonal crosssection is also practical, for example.

Figure 11 g shows a cross section of an alternative embodiment of the impact weight 30, wherein the impact weight 30 comprises bores 38 which extend from the lower portion of the impact weight 30 in the height direction of the impact weight, wherein the bores are distributed along the circumference of the impact weight 30. The length of the bores is between 50-90% of the height of the impact weight, preferably between 60-80% of the impact weight height. An elongated member 39, e.g. of steel, e.g. a solid steel rod, is received inside of the bore and extends along the entire length of the bore, such that the lower end the elongated member 39 extends beyond the lower portion of the impact weight and makes contact with the anvil face. It is envisaged that the elongated members 39 act as axial springs, e.g. having radial play in the respective bore. In embodiments, as illustrated, each elongated member 39 may have a foot that is configured to come into contact with the anvil face.

Figure 12a shows the pile run prevention member 400 which comprises a damping member

401 which is suspended from the pile driver or, optionally a crane. The engagement member

402 is suspended from the damping member 401 and engages the inward top flange 1 b of the pile 1 .

Figure 12b shows an alternative embodiment of the pile run prevention member 400, wherein the pile run prevention member is embodied as a cable 403 with an first and a second end, wherein the first end is suspended from the pile driver, and wherein the second end is provided with an engagement member 402 which is configured to engage the inward top flange of the pile 1 b. As shown, during pile driving the cable is slack 403.

Claims

C L A I M S

1 . Pile driving method for driving a hollow and open ended large diameter steel pile vertically into the soil, the pile having a cylindrical top portion with a top portion wall thickness between an inner diameter and an outer diameter, wherein said outer diameter is at least 5 meters, e.g. a monopile of an offshore wind turbine, e.g. into the seabed, wherein use is made of a pile driving device that is arranged on a top end of the pile, which pile driving device comprises:

- a drive head assembly having an annular contact face resting on the top end of the pile and an annular anvil face above the annular contact face,

- a steel impact weight which has a mass of at least 100 tonnes, e.g. more than 200 tonnes, which impact weight is vertically mobile above the anvil face of the drive head assembly,

- a vertical guide structure configured to vertically guide the impact weight, wherein the drive head assembly is configured for energy transfer between the anvil face and the contact face for the transfer of energy from the falling impact weight to the annular contact face and thereby to the pile top,

- a lift system configured to bring the impact weight into an initial height position relative to the anvil face of the drive head assembly,

- a quick release system adapted to effect a quick release of the lift system so that the impact weight falls down from said initial height position onto the anvil face of the drive head assembly, wherein the method comprises a repeated cycle wherein:

- the impact weight is lifted by means of the lift system into an initial height position,

- the quick release mechanism is operated to effect the quick release of the lift system so that the impact weight falls down from the initial height position onto the anvil face of the drive head assembly, wherein energy from the falling impact weight is transferred to the contact face of drive head assembly and thereby to the top end of the pile, so that the pile is driven deeper into the soil, wherein the impact weight comprises, preferably is embodied as, a tubular impact weight which is made of steel, e.g. having a wall thickness between 10 and 20 centimetres.

2. Pile driving method according to claim 1 , wherein the impact weight is embodied as a tubular impact weight which is made of steel, e.g. having a wall thickness between 10 and 20 centimetres, e.g. wherein the tubular impact weight has a height of between 4 and 12 meters, e.g. a height of between 6 and 10 meters.

3. Pile driving method according to claim 1 or 2, wherein the tubular impact weight has diameter such that, in vertical projection, the tubular impact weight overlaps with the wall thickness of the top portion of the pile.

4. Pile driving method according to one or more of the preceding claims, wherein multiple accelerator devices are provided in the pile driving device which are arranged in a circular array and engage on the tubular impact weight at distributed positions.

5. Pile driving method according to one or more of the preceding claims, wherein the pile driving device is configured so that the tubular impact weight falls under gravity (1G) only, e.g. the pile driving device being devoid of one or more accelerator devices for the impact weight.

6. Pile driving method according to one or more of the preceding claims, wherein the tubular impact weight is hollow and open ended, e.g. wherein the tubular impact weight has a central passage of a diameter of at least 2 meters, e.g. at least 50% or at least 75% of the inner diameter of the top portion of the pile.

7. Pile driving method according to one or more of the preceding claims, wherein the pile has an inward top flange, e.g. with bolt holes, and wherein the drive head assembly is configured to leave a portion of the inward top flange exposed, e.g. wherein the drive head assembly has an inner diameter that is greater than the inner diameter of the inward top flange so that a peripheral portion of the flange is exposed., e.g. to allow gripping of the flange by a gripper of a pile lifting tool.

8. Pile driving method according to one or more of the preceding claims, wherein the tubular impact weight has a wall thickness of between 10 and 20 centimetres.

9. Pile driving method according to one or more of the preceding claims, wherein the lifting means are configured to provide a vertical distance between the anvil face and the initial height of the impact weight of at most 2 meters, e.g. of about 1 meter.

10. Pile driving method according to one or more of the preceding claims, wherein the pile driving device has an outer housing extending coaxially about the tubular impact weight, the outer housing having an open lower end resting on the drive head assembly and wherein, preferably, the outer housing is peripherally closed.

11 . Pile driving method according to one or more of the preceding claims, wherein the lift mechanism comprises multiple hydraulic lift cylinders, and wherein, preferably, the quick release system comprises one or more quick release valves that are opened to allow rapid discharge of hydraulic liquid from the lift cylinders.

12. Pile driving method according to one or more of the preceding claims, wherein the vertical guide structure comprises roller assemblies, each roller assembly comprising one or more horizontal axis rollers that engage the tubular impact weight, and wherein the roller assemblies are configured to press the one or more rollers against the tubular impact weight with a pre-load.

13. Pile driving method according to one or more of the preceding claims, wherein the pile driving device is connected to lifting tool of a crane during pile driving, wherein multiple shock absorbers are mounted to a top of the pile driving device, e.g. to the outer housing thereof, which multiple shock absorbers connected to a spreader structure, e.g. two shock absorbers connect to a spreader bar, at a top end of the shock absorbers, and wherein the spreader structure is connected to the lifting tool, e.g. via two slings.

14. Pile driving method according to one or more of the preceding claims, wherein the method is performed at sea, e.g. for the installation of a monopile, and wherein use is made of a vessel comprising a pile gripper device that is operated to hold the pile vertical during pile driving, e.g. a motion compensating pile gripper, e.g. the vessel being in floating condition.

15. Pile driving system for driving a hollow and open ended large diameter steel pile vertically into the soil, the pile having a cylindrical top portion with a top portion wall thickness between an inner diameter and an outer diameter, wherein said outer diameter is at least 5 meters, e.g. a monopile of an offshore wind turbine, e.g. into the seabed, wherein the system comprises a pile driving device that is configured to be arranged on a top end of the pile, which pile driving device comprises:

- a drive head assembly having an annular contact face configured for resting on the top end of the pile, and an annular anvil face above the annular contact face,

- a vertical guide structure configured to vertically guide the impact weight, wherein the drive head assembly is configured for energy transfer between the anvil face and the contact face for the transfer of energy from the falling impact weight to the contact face and thereby to the pile top,

- a quick release system adapted to effect quick release of the lift system so that the impact weight falls down from said initial height position onto the anvil face of the drive head assembly, wherein the pile driving device is operable in a repeated cycle wherein:

- the quick release mechanism is operated to effect a quick release of the lift system so that the impact weight falls down from said initial height position onto the anvil face of the drive head assembly, wherein energy from the falling impact weight is transferred to the contact face of drive head assembly and thereby to the top end of the pile, so that the pile is driven deeper into the soil, wherein the impact weight comprises, preferably is embodied as, a tubular impact weight which is made of steel, e.g. having a wall thickness between 10 and 20 centimetres.

16. Pile driving system according to claim 15, wherein the impact weight is embodied as a tubular impact weight which is made of steel, e.g. having a wall thickness between 10 and 20 centimetres, e.g. wherein the tubular impact weight has a height of between 4 and 12 meters, e.g. a height of between 6 and 10 meters.

17. Pile driving system according to claim 15 or 16, wherein multiple accelerator devices are provided in the pile driving device which are arranged in a circular array and engage on the tubular impact weight at distributed positions.

18. Pile driving system according to claim 15 or 16, wherein the pile driving device is configured so that the tubular impact weight falls under gravity (1G) only, e.g. the pile driving device being devoid of one or more accelerator devices for the impact weight.

19. Pile driving system according to one or more of claims 15 - 18, wherein the tubular impact weight has diameter such that, in vertical projection, the tubular impact weight overlaps with the wall thickness of the top portion of the pile.

20. Pile driving system according to claim 15 - 19, wherein the tubular impact weight has a central passage of a diameter of at least 2 meters, e.g. at least corresponding to 50% or 75% of the inner diameter of the top portion of the pile.

21 . Pile driving system according to one or more of claims 15 - 20, wherein the pile driving device has an outer housing extending coaxially about the tubular impact weight, the outer housing having an open lower end resting on the drive head assembly, and wherein the outer housing is preferably peripherally closed, and wherein, preferably, the outer housing has an open top end and having a central passage of a diameter at least corresponding to 50%, more preferably at least 75%, of the inner diameter of the top portion of the pile.

22. Pile driving system according to one or more of claims 15 - 21 , wherein the lift mechanism comprises multiple hydraulic lift cylinders, and wherein, preferably, the quick release system comprises one or more quick release valves that are opened to allow rapid discharge of hydraulic liquid from the lift cylinders.

23. Pile driving system according to one or more of claims 15 - 22, wherein the vertical guide structure comprises roller assemblies, each roller assembly comprising one or more horizontal axis rollers that engage the tubular impact weight, e.g. wherein the roller assemblies are mounted to the outer housing, and wherein the roller assemblies are configured to press the one or more rollers against the tubular impact weight with a pre-load.

24. Pile driving system according to one or more of claims 15 - 23, wherein the energy transfer assembly of the drive head assembly comprises one or more spring devices and/or one or more damper devices that are effective between the anvil face and the contact face.

25. Pile driving system according to one or more of claims 15 - 24, wherein the drive head assembly comprises multiple spring devices and/or multiple damper devices which are arranged in a circular array in the drive head assembly, e.g. embodied as integrated spring and damper devices.

26. Pile driving system according to one or more of claims 15 - 25, wherein the drive head assembly comprises multiple cylinder devices which are arranged in a circular array in the drive head assembly, each having a cylinder body, a piston, and a chamber delimited by the piston, wherein the chamber is filled with liquid, e.g. oil.

27. Pile driving system according to one or more of claims 15 - 26, wherein the pile driving device comprises a sleeve that extends from the head end assembly down along a top section of the pile.

28. Pile driving system according to one or more of claims 15 - 27, wherein the system further comprises a vibratory device.

29. Pile driving system according to claim 28, wherein the vibratory device is configured for generating an alternating force about a vertical axis of the pile at a vibration frequency in order to vibrate the pile about the axis and to reduce friction between the pile and the soil, e.g. the seabed.