Patent ID: 12215004

DETAILED DESCRIPTION OF THE FIGURES

Turning toFIGS.1and2, an embodiment of an assembly1for installing a pile2in a seabed3according to a first aspect of the invention is shown. The assembly1comprises a floating vessel23with a positioning system for keeping the vessel4at an installation location6relative to the seabed3(seeFIGS.32-35). The floating vessel23in the shown embodiment is a semi-submersible vessel4. The positioning system has a positioning stiffness defined between the installation location6and the vessel4.

The positioning system can be a dynamic positioning system, wherein the floating vessel23is kept at the installation location6using a control system activating thrusters96provided below the vessel4. For a dynamic positioning system the positioning stiffness is usually programmed in the control system, wherein the thrusters96provide increasing thrust when the vessel4moves, or drifts, further away from the installation location.

The positioning system may also be a spread mooring system25deployed by a floating vessel23, wherein the positioning stiffness is defined by the tension in the mooring lines. SeeFIG.30for an assembly1with a spread mooring system25.

In case a jack-up vessel61is used, the positioning stiffness is substantially infinite, because the vessel4is standing on the seabed3with jack-up legs during installation. SeeFIG.31for an assembly1with a jack-up vessel61, wherein the complete hull of the jack-up vessel61is above a not shown waterline62.

The pile guiding system8extends above the deck85of the vessel4and/or below a keel86of the vessel4. See for exampleFIG.31, wherein the shielding wall55of the pile guiding system8extends below a keel86of the jack-up vessel61, and wherein the first guiding device10extends above the deck85.

The assembly1further comprises a pile guiding system8configured to guide the pile2during installation thereof. The pile guiding system8itself is also part of the invention. The pile guiding system8comprises a base9provided on the vessel4. A first guiding device10is connected to the base9. The first guiding device10is configured to accommodate the pile2during installation thereof.

A resilient member11provides a resilient connection between the vessel4and the pile2during installation thereof. The resilient connection allows relative motions between the pile2and the vessel4. The resilient member11has a connection stiffness.

The first guiding device10comprises the resilient member11for providing the resilient connection between the first guiding device10and the pile2. The resilient member11may also, or instead be provided between the base9and the first guiding device10and/or between the vessel4and the base9.

FIG.37is a schematic depiction of the assembly1ofFIGS.1and2. The vessel4can be seen as connected to the installation location6via a positioning system5having a positioning stiffness7. The positioning system5can be for example a DP system, a mooring system, or a jack-up system. For the jack-up system the positioning stiffness7will be substantially infinite. The pile2is connected to the vessel4via the pile guiding system8, in particular via the first guiding device10. The resilient member11in this embodiment is provided between the first guiding device and the vessel, and between the first guiding device and the pile. The pile2is presented as an inverted pendulum and can move as such until it has reached a sufficiently deep penetration depth. A dampening member73may also be provided in the assembly1or pile guiding system8to dampen the pile motions between the vessel and the pile2.

The dampening member73may be helpful during lowering the pile towards the seabed, because when the pile is suspended from a crane82it may swing or move sideways due to waves or a movement of the crane relative to the installation location. The dampening member73may limit the motions of the pile during lowering towards the seabed. InFIGS.4and5the pile is lowered towards the seabed while the pile guiding system8is in the open position52. The lowering towards the seabed may also be done while the pile guiding system is in the closed position, i.e. enclosing the pile with the first guiding device10and/or the second guiding device26. In the closed position the dampening member73, for example in the form of one or more hydraulic or pneumatic cylinders or electric motors, may dampen the motions of the pile in an effective manner. Also for the embodiment with only the first guiding device10, as shown inFIGS.1and2, the dampening member73may be advantageously used to dampen the pile motions during lowering of the pile towards the seabed.

The resilient member11is configured and intended to keep a natural period205of a pivoting movement15of the pile2about the seabed3caused by waves during installation thereof longer than a dominant wave period203of a wave spectrum200at the installation location6by providing the resilient connection with a low connection stiffness13.

This is further explained with respect to the graph as shown inFIG.36, wherein a wave spectrum200is shown for a chosen installation location6. The horizontal axis201shows the occurring wave periods. The vertical axis202shows the spectral density. The peak associated with line203shows the dominant, or governing wave period203at the installation location6. The pivoting of the pile2tends to be dictated by the waves in the period of said dominant wave period203. When a natural period205of the pivoting movement15of the pile2coincides with the dominant wave period203this can lead to resonance of the pile2motions. The dominant wave period203depends on the exact installation location, but tends to be in the range of 6-10 seconds during installation.

The pile may thus resonate because of the dominant wave period203. This is to be avoided. Assemblies or pile guiding systems of the prior art avoid resonance by keeping the natural period204of the pile motions lower than the dominant wave period203. This is achieved by providing a substantially stiff or rigid connection between the pile and the vessel. A disadvantage is that the loads between the pile guiding system and the vessel because of the first order wave forces become large, resulting in a heavy construction. In the present invention it was recognized that providing a resilient connection between pile and vessel allows the natural period205of the pile motions to move away from the dominant wave period203. This way, the pile is allowed to move relative to the vessel, or the pile guiding system, reducing the loads on the pile guiding system.

The pivoting, or oscillating movement of the pile2about the seabed3is mainly induced by the first order waves at the installation location. The forces on the pile guiding system8related to the pivoting movement15of the pile2can become considerable.

Currently available pile guiding systems solve the problem of the pivoting pile2by holding the pile2in a stiff manner, i.e. substantially no resilience in the connection between the vessel4and the pile2. This can be beneficial, because the pivoting motions of the pile2are kept minimal and no resonance of the pile2occurs. Pile stability can be provided by the positioning system. However, a disadvantage of the stiff connection is that the pile guiding system experiences high loads. The high loads have to be taken up by the pile guiding system, resulting in a heavy and cumbersome construction. With increasing pile dimensions, the loads will become higher resulting in even heavier and more cumbersome constructions.

Whereas for the currently available pile guiding systems the natural period205of the pivoting movement15of the pile2is kept lower than the dominant wave period203at the installation location, the present invention is based on the insight that the natural period205of the pivoting can be kept longer than the dominant wave period203by providing a resilient connection between the pile2and the vessel4, wherein the resilient connection has a low stiffness. When the natural period205of the pivoting movement15of the pile2is kept longer than the dominant wave period203, resonance is prevented. The pile guiding system8with a resilient pile2-vessel4connection will experience lower loads compared to the currently available pile guiding system8with stiff pile2-vessel4connections. An advantage is that the pile guiding system8according to the invention can have a less heavy and less cumbersome construction. With increasing pile dimensions, this positive effect becomes more prominent.

Hence, the resilient member11is able to prevent resonance of the pile2motions while limiting said pile2motions at the same time.

When the pile has been lowered to the seabed by the on-board crane the pile gradually becomes supported more by the seabed and less by the crane as the pile sinks into the seabed by its own weight. During a phase of installation when the pile is at least partially supported by the on-board crane82and at least partially by the seabed, A horizontal movement of the vessel, and thus of the crane, relative to the installation location may cause a horizontal movement of an upper end of the pile. The horizontal movement of the upper end follows from a horizontal force exerted on the upper end of the pile by the crane rigging lines. As the bottom end of the pile is horizontally fixed by the seabed or by for example a mudmat, the horizontal movement of the upper end of the pile causes the pile to pivot about the seabed. When the pile is positioned in and enclosed by the pile guiding system8the pile will push against the pile guiding system because of the pivoting movement. The pushing force of the pile on the pile guiding system will move the vessel further out of position. When using a pile guiding system with a relatively stiff, or rigid connection the pushing force may become higher than the positioning system can counter. In particular a Dynamic Positioning system may not be able to counter said pushing force of the pile. When this happens, control of the vessel position may be lost and the vessel might pull the pile over by providing a less stiff, or softer connection according to the invention the pile may be kept stable without pushing the vessel out of position.

When the pile has been lowered to the seabed by the on-board crane the pile gradually becomes supported more by the seabed and less by the crane as the pile sinks into the seabed by its own weight. During a phase of installation when the pile is at least partially supported by the on-board crane82and at least partially by the seabed, a situation can occur where the pile is no longer stable and could fall over. The resilient member11may prevent such an unstable situation by keeping the natural period205of the pivoting movement of the pile longer than the dominant wave period203.

The resilient member11is configured and intended to keep said natural period205longer than 1.5 times the dominant wave period203of the wave spectrum200at the installation location.

The connection stiffness is low enough to keep the natural period205of the pivoting movement of the pile2longer than the dominant wave period203, and high enough to provide stability to the pile2.

The pile guiding system8comprises a first actuator19for moving the first guiding device10relative to the base9in a first direction20.

The pile guiding system8comprises a second actuator21for moving the first guiding device10relative to the base9in a second direction22, the second direction22being perpendicular to the first direction20. See for exampleFIG.9BorFIG.10B.

The vessel4is a floating vessel23configured to float during installation of the pile2.

The pile2is intended to be installed in a predetermined, first orientation33(FIG.1). This usually is a vertical orientation, but may also be a slightly angled orientation. When the pile2during installation tilts to an orientation which is non-aligned with the predetermined, first orientation33, the pile2has to be moved back to the predetermined, first orientation33. Moving the pile2back from the non-aligned orientation32(FIG.2) to the predetermined, first orientation33can be done by moving the first guiding device10relative to the base9, or vessel4. The first actuator19and the second actuator21may be used for moving the first guiding device10towards the predetermined, first orientation33. The first guiding device10thereby exerts a first force34on the pile2in a direction35towards the predetermined orientation.

Moving the pile2back to the predetermined orientation33may also be done by moving the floating vessel23in a direction35towards the predetermined orientation. A combination of moving the first guiding device10and moving the floating vessel23is also possible.

Turning toFIGS.3to17, another embodiment of an assembly1according to the invention is shown together with a method according to the invention for installing a pile2at an installation location6.

The assembly1comprises a pile guiding system8as described in relation toFIG.1. In addition the pile guiding system8comprises a second guiding device26located at a distance27below the first guiding device10. Providing the second guiding device26above the first guiding device10is also possible.

The distance27between the first guiding device and second guiding device is at least one diameter D1as defined by the guiding opening, preferably at least two diameters D1. The distance27may also be defined in terms of pile diameters D2, wherein the distance27is at least one pile diameter D2, preferably at least two pile diameters D2, seeFIG.9B.

FIG.38is a schematic depiction of the assembly1comprising a pile guiding system8with a first guiding device10and second guiding device26. The second guiding device26is depicted as spring. The vessel4can be seen as connected to the installation location6via a positioning system5having a positioning stiffness7. The positioning system5can be for example a DP system, a mooring system, or a jack-up system. For the jack-up system the positioning stiffness7will be substantially infinite. The pile2is connected to the vessel4via the pile guiding system8, in particular via the first guiding device10and the second guiding device26. The resilient member11in this embodiment is provided between the first guiding device and the vessel, between the first guiding device10and the pile and between the pile2and the vessel via the second guiding device26. The pile2is presented as an inverted pendulum and can move as such until it has reached a sufficiently deep penetration depth. A dampening member73may also be provided in the assembly1or pile guiding system8to dampen the pile motions between the vessel and the pile2.

The first and second guiding device10,26define a guiding opening28for accommodating the pile2. Said first and second guiding devices10,26are configured to engage an outer surface29of the pile2for holding the pile2.

The guiding opening28of the pile guiding system8extends beyond a contour81of the floating vessel23in top view, see for example the top view ofFIG.10B.

The first guiding device10and second guiding device26are configured to together apply a moment30about a horizontal axis31to the pile2for reorienting the pile2from a non-aligned orientation32to a predetermined, first orientation33. Said moment30is applied by exerting a first force34and a second force36to the pile2. The first force34is exerted in a direction35towards the predetermined, first orientation33by the first guiding device10. The second force36is exerted via the second guiding device26. The direction of the second force36is opposite to the first force34. This will be further explained in relation withFIG.32.

The first guiding device10and the second guiding device26exert the respective first force34and the second force36horizontally on the pile2.

The second guiding device26may have a resilient member11for providing a resilient connection between the second guiding device26and the pile2.

The assembly1comprises a control unit (not shown) which is coupled to the pile guiding system8. The control unit comprises a sensor for measuring the orientation of the pile2during installation. When the sensor measures a non-alignment of the pile2relative to said predetermined, first orientation33the control unit is configured to move the first guiding device10towards the predetermined orientation via the first19and/or second actuator21.

The control unit may comprise a sensor for measuring the rate of change of the non-alignment, wherein the control unit comprises a PID controller which actuates the pile guiding system8to apply the moment30to the pile2based on the first orientation33as setpoint.

The control unit may or may not be coupled with the dynamic positioning system of the floating vessel23.

The first guiding device10and/or the second guiding device26comprises a plurality of engaging members41for engaging the pile2during installation. In the shown embodiments there are four engaging members41per guiding device. A different amount of engaging members41is also possible.

The engaging members41are placed at regular intervals around the circumference of the pile2, i.e. around the guiding opening28.

The engaging members41are connected to their corresponding guiding device via an engaging actuator43. The engaging members41are shown inFIGS.18and19for the second guiding device26. These may be similar for the first guiding device10. The engaging actuator43moves the engaging member41inwardly and outwardly relative to a centre44of the guiding opening28between a first, outward position45(FIG.9B), wherein the engaging members41do not engage the pile2, and a second, inward position46(FIG.9C), wherein the engaging members41engage the pile2.

The engaging member41comprises the resilient member11for providing a resilient pile2connection between the pile2and the respective guiding device.

Each engaging member41comprises a roller48. The roller48may be the resilient member11.

The resilient member11may comprise a hydraulic cylinder, a pneumatic cylinder, and/or an electric actuator.

A stiffness of the resilient member11may be adjustable via an adjusting member49. The adjusting member49is configured to decrease the stiffness to a lower stiffness during a downward50moving of the pile2into the seabed3as the stiffness of the soil increases.

Depending on the soil conditions the natural period205of the pivoting movement15of the pile2will generally decrease when the pile2penetrates deeper into the seabed3. In a sense the pile2becomes stiffer. This added stiffness influences the total stiffness of the assembly1. In order to prevent that the natural period205of the pivoting movement15of the pile2becomes too close to the dominant wave period203, it may be required that the connection stiffness is decreased. This can be achieved by decreasing the stiffness of the resilient member11.

The adjusting member49can for example be incorporated in the engaging actuator43, wherein the engaging actuator43is configured to provide different levels of resilience.

The pile guiding system8comprises an opening member51for opening and closing the guiding opening28. The opening member51is movable between an open position52(FIG.20) and a closed position53(FIG.21). The open position52allows a pile2to be positioned in the guiding opening28, seeFIGS.3to5. The open position52also allows the vessel4to move horizontally away from the pile2, as shown inFIG.17.

The closed position53of the opening member51is for example shown inFIG.6for the first guiding device10. For both the first and second guiding device26the closed position53is shown in for exampleFIGS.7-15. In the closed position53the pile2is enclosed by the pile guiding system8.

The opening member51can be moved by opening actuators88, as shown inFIGS.20and21. The opening member51comprises two arms89which can pivot about respective pivot axes between the open position52and closed position53. The opening actuators88are connected to the arms89and the frame. Each arm89comprises an engaging member41.

The second guiding device26may be movable relative to the first guiding device10in the first direction20via a third actuator (not shown) and/or in the second direction22via a fourth actuator64. InFIGS.18and19two fourth actuators64are shown for moving the second guiding device26toward and away from the vessel4, i.e. in the second direction22.FIG.19shows the second guiding device26in a position outward from the vessel4relative to the position of the second guiding device26as shown inFIG.18. The fourth actuator64can be connected to a base9or to the vessel4itself.

The second guiding device26is movable independently from the first guiding device10. Hence, the second guiding device26can move relative to the first guiding device10.

In another embodiment the second guiding device26is rigidly connected to the floating vessel23or the base9. This way, the second guiding device26remains stationary relative to the vessel4.

FIGS.22to25show another embodiment of the assembly1and pile guiding system8according to the invention. The assembly1may comprise the same features as the assembly1and pile guiding system8of the previous figures. The embodiment as shown inFIGS.20-23further comprises a shielding member54for limiting wave loads on the pile2by shielding the pile2from waves.

The shielding member54comprises a shielding wall55surrounding the second guiding device26. The shielding member54may also surround the first guiding device10.

The shielding wall55may be closed, i.e. no water can flow through the wall. It may also be possible to provide a plurality of through holes in the shielding wall55.

At a lower end56of the shielding wall55a bubble generating unit57is provided, seeFIG.23wherein a part of the shielding wall55is removed to show the bubbles generated by the bubble unit. The bubble generating unit57is provided inside an inner volume58defined by the shielding wall55and around the guiding opening28, i.e. around the pile2. The bubble generating unit forms a bubble screen59around the guiding opening28. The bubble screen59helps to reduce noise during pile2driving. Noise reduction is beneficial, because often the time window for installing piles is limited to for example daylight because of noise regulations. After daylight the maximum allowed noise is lower. With the bubble screen it is possible to reduce installation noise to within the allowed noise after daylight, extending the workability.

Turning toFIGS.26-29another embodiment of the assembly1and pile guiding system8according to the invention are shown. The assembly1comprises a vessel4and a pile guiding system8. The vessel4shown in the figures is a floating vessel23, in particular a semi-submersible vessel4. A jack-up vessel61is also possible.

The pile guiding system8comprises a main frame65. The first guiding device10and second guiding device26are connected to each other via the main frame65. The first guiding device10and second guiding device26are connected to the base frame9via the main frame65. The main frame65is freely movable relative to the base frame9in the first direction20and/or the second direction22.

Freely movable means that no actuators are required to move the main frame65relative to the base frame9. When the pile2moves relative to the vessel4, the main frame65can be moved by the pile2such that the main frame65moves freely relative to the base frame9in at least one direction20,22.

The main frame65is connected to the base frame9via an intermediate frame66. The main frame65may also be freely movable relative to the intermediate frame66. This way, the main frame65can freely move relative to the base frame9in at least two directions.

The first direction20defines a first axis69(FIG.28B). The second direction22defines a second axis70. The first direction20and second direction22are horizontal or substantially horizontal.

The main frame65is connected to the intermediate frame66via a first intermediate actuator67and/or a second intermediate actuator, one of which is shown inFIG.28B. The other intermediate actuator is provided at a distance behind the shown first intermediate actuator67. The first and second intermediate actuator are configured to rotate the main frame65relative to the intermediate frame66about a first axis69by the first intermediate actuator67and/or a second axis70by the second intermediate actuator.

When the first and second intermediate actuator both move from a retracted position to an extended position90as shown inFIG.28B, or vice versa, the main frame65pivots about the first axis69parallel to the first direction20. The main frame65pivots about a pivoting point91as shown inFIG.28B. The pivoting point91could be a ball joint.

When the first intermediate actuator67moves relative to the second intermediate actuator the main frame65pivots about the second axis70(FIG.29B). It is also possible to pivot the main frame65about another axis within the plane defined by the first axis69and second axis70by the first and second intermediate actuators. This can for example be achieved by a, in top view, triangular configuration between the first intermediate actuator67, the second intermediate actuator and the pivoting point.

The first intermediate actuator67and the second intermediate actuator extend upwards, preferably vertically, from the intermediate frame66towards the main frame65.

A resilient member11may be provided next to the first and/or second intermediate actuators, wherein the one or more resilient members11connect the main frame65to the intermediate frame66or base frame9.

A resilient member11may instead or in addition be provided on the first and/or second guiding devices10,26, similar to the embodiments as shown inFIGS.1-25. A resilient roller may serve as resilient member11.

The stiffness of the resilient members11may be chosen such that the natural period205of the pivoting movement15of the pile2remains longer than the dominant wave period203.

The first intermediate actuator67may comprise a first resilient member11and the second intermediate actuator may comprise a second resilient member11. The resilient function can be integrated in the actuators.

The upwardly or vertically extending intermediate actuators67and/or resilient members11result in an embodiment wherein the loads are taken up mainly vertically by the vessel4. A vessel4can handle vertical loads better than horizontal loads. Horizontal loads have to be actively countered by thrusters96of the vessel4, whereas vertical loads can be countered by the buoyancy of the vessel4.

The pile guiding system8is configured to apply the moment30to the pile2by rotating the main frame65about the first axis69with the first intermediate actuator67and/or the second axis70with the second intermediate actuator. This way the first guiding device10exerts a first force34on the pile2and the second guiding device26exerts the opposite, second force36on the pile2.

In all embodiments a dampening member may be provided for dampening the motions between the pile2and the vessel4. The dampening function may be integrated in one or more of the actuators.

The dampening member73is useful when during installation the pile reaches a penetration depth at which the pile become stable by itself, i.e. wherein the pile does not need to be held in order to remain standing upright. There comes a point during installation wherein the natural period of the pile motions will move from natural period205towards natural period204, as indicated inFIG.36with arrow206. That is because the behaviour of the pile will become stiffer with increasing penetration depth. The pile motions will have to go through the dominant wave period. In order to guide this process without incurring resonance the pile motions can be dampened by the dampening member. Providing negative stiffness for bringing the natural period205to natural period204is also possible

The main frame65comprises an opening member51for opening and closing the guiding opening28. The opening member51is in the form of a door which can pivot about a door pivot axis92.

A counterweight93may be provided at an end194of the main frame65. This may provide a restoring force for keeping the main frame65upright, thereby keeping the pile2upright. The counterweight is located at or near the intermediate actuators67, at a distance from the pivoting point91.

The pile guiding system8as described in relation toFIGS.3-30is also suitable to assist in keeping the floating vessel23at an installation location6during installation of a pile2into a seabed3at the installation location. The pile guiding system8comprises a base9via which the pile guiding system8is connected to the vessel4.

The first guiding device10connected to the base9and the first guiding device10is configured to hold the pile2during installation thereof. The first guiding device10is movable relative to the base9in a horizontal plane and configured to be kept substantially stationary relative to the installation location6during installation of the pile2.

A first actuator19and a second actuator21connected to the first guiding device10can move the first guiding device10relative to the base9in the horizontal plane for keeping the first guiding device10substantially stationary relative to the installation location6during installation of the pile2.

A second guiding device26is provided and located at a distance27below the first guiding device10. The second guiding device26may instead be located above the first guiding device10. The second guiding device26is connected to the floating vessel23or to the base9.

The second guiding device26is an effective add-on to existing pile guiding systems which have only the first guiding device10, because the second guiding device26provides an anchoring effect between the seabed3and the vessel4via the pile2when the vessel4moves away from the installation location. The anchoring effect reduces the power required by the dynamic positioning system or spread mooring positioning system for keeping the floating vessel23at the installation location.

The second guiding device26comprises a resilient member11for providing a resilient connection between the pile2and the second guiding device26during installation thereof.

The first guiding device10is movable relative to the second guiding device26in the horizontal plane.

The first guiding device10may be configured to rigidly hold the pile2while moving relative to the vessel4, or base9.

The second guiding device26is substantially rigidly connected to the floating vessel23or to the base9and configured to remain stationary relative to the vessel4or to the base9.

When the vessel4moves away from position, the second guiding device26will engage the pile2. The vessel4thus pushes the pile2via the second guiding device26with the previously described second force36. Because the first guiding device10remains stationary relative to the installation location, the pushed pile2experiences a first force34exerted by the first guiding device10, which is similar to the first force34as previously described. The combination of the first guiding device10and the second guiding device26thus helps in preventing the vessel4from moving away. This will work when the bottom end of the pile2is horizontally fixed and increases with increasing penetration depth of the pile2into the seabed3.

Operation

The assembly1and the pile guiding system8according to the invention comprising a first guiding device10and a second guiding device26have multiple applications.

A first application relates to a method wherein the pile guiding system8comprises a resilient member11for keeping the natural period205of the pivoting moment30of the pile2longer than the dominant wave period203at the installation location.

The method comprising the steps of providing an assembly1according to the invention at an installation location. The method comprises positioning the pile2in an upright orientation74in the pile guiding system8, as shown inFIGS.3and4. A lifting tool94is connected to the pile2and a crane82lifts and positions the pile2in the pile guiding system8. The opening members51are in the open position52so that the pile2can be positioned in the guiding opening28defined by the first and second guiding devices10,26.

A next step is lowering the pile2to the sea bed, as shown fromFIG.4toFIG.5. The opening member51is still in the open position52. It is also possible to lower the pile2to the seabed3with the opening member51in the closed position53. During lowering the pile towards the sea bed the dampening member73may dampen the pile motions.

Next the pile2is installed into the seabed3, seeFIGS.13and14. The opening members51are in the closed position53. A pile driving tool87, e.g. a hammer, is attached to a top of the pile2via a crane82. The pile driving tool87drives the pile2into the seabed3to a target depth.

When the pile2has reached its target depth, the pile2driving tool is removed from the top of the pile2.FIGS.15to17show the next steps of removing the pile driving tool and moving the opening members51to the open position52and moving the vessel4away from the installed pile2(FIG.17B).

The natural period205of the pivoting moment30of the pile2during installation is kept longer than the dominant wave period203at the installation location6by the pile guiding system8.

During installation of the pile2the natural period205of the pivoting movement15of the pile2during installation is kept longer than the dominant wave period203at the installation location6by adjusting the connection stiffness13of the resilient member11. This is shown inFIGS.9to12, wherein the pile2pivots relative to the vessel4.

The second guiding device26in theFIGS.9to12is rigidly connected to the vessel4. Hence, the second guiding device26remains stationary. The second guiding device26comprises resilient members11for keeping the natural period205of the pivoting movement15of the pile2longer than the dominant wave period203. For the method it is also possible that the second guiding device26is movable relative to the vessel4and/or relative to the first guiding device10.

InFIG.9the pile2is in a substantially vertical position. This is the desired and predetermined, first orientation33in which orientation the pile2is to be installed. The engaging members41are moved from a non-engaging position (FIG.9B) to an engaging position (FIG.9C) wherein the engaging member41engage the pile2.

FIG.10shows the pile2in a pivoted position, i.e. non-aligned position32. The first guiding device10has moved in the first direction20.1relative to the base9.FIG.10Bshows the two resilient members11in the form of first actuators19between the base9and the first guiding device10being moved inwardly and outwardly by the pressure of the pile2, respectively. The resilient members11provided in the engaging member41are moved inward. The diametrically opposing engaging members41may be idle at this point. They do not have to contact the pile2as shown inFIG.10B.

FIG.11shows a pivoting movement15of the pile2in a direction20.2opposite to the direction20.1inFIG.10B.

FIG.12shows the pile2being pivoted away from the vessel4. The second actuators21, and/or resilient members11, between the intermediate frame66and the first guiding device10allow the first guiding device10to move outwardly together with the pile2.

The resilient member11allows relative motions between the pile2and the pile guiding system8, as shown inFIGS.9-12. This leads to lower loads on the vessel4compared to a pile guiding system8according to the prior art in which the pile2is more rigidly held.

The pile guiding systems8as described in relation toFIGS.22-25andFIGS.26-29are also suitable to perform the above described method. A positioning system can be a dynamic positioning system, a spread mooring system25, or a jack-up system95.

A second application relates to a method of installing a pile2into a seabed3with a floating vessel23, wherein a moment30is applied to the pile2for reorienting a pile2from a non-aligned orientation32to a predetermined orientation.

The method comprises the steps:a) providing the floating vessel23and a pile guiding system8connected to said floating vessel23via a base frame9at an installation location, wherein the pile guiding system8comprises a guiding opening28for accommodating the pile2during pile installation,b) positioning the pile2in the guiding opening28of the pile guiding system8, seeFIGS.3and4,c) lowering the pile2to the sea bed, seeFIG.5,d) fixing a bottom end of the pile2to the seabed3in a horizontal direction (not shown),e) moving the pile2downwards into the seabed3in a predetermined, first orientation33, in particular a vertical orientation, by exerting a downward force on the pile2, seeFIGS.13and14,

When during at least step e) or after step d) the pile2becomes non-aligned with the predetermined first orientation33, the pile2is reoriented from a second non-aligned orientation32back to the predetermined first orientation33by applying a moment30about a horizontal axis31on the pile2with the pile guiding system8.

For the installation of wind turbines the first orientation33will generally be a vertical orientation, or a substantially vertical orientation.

Step b) can be performed by an on board crane82provided on the floating vessel23.

Step b) can also be performed by an upending device (not shown) for upending the pile2from a substantially horizontal orientation on deck85to the upright orientation74.

Step e) can be performed by a hammering tool87, for example a vibrating hammering tool87. Other known tools are also possible.

During step d) the bottom end of the pile2can be fixed in the horizontal direction by allowing the bottom end of the pile2to penetrate the sea bed by using self-weight of the pile2. The pile2will penetrate itself into the seabed3, thereby fixing the bottom of the pile2in a horizontal plane. It is also possible to fix the bottom end of the pile2by positioning the bottom end of the pile2in a retaining device (not shown). The retaining device is located on the seabed3at the installation location6and configured to prevent horizontal movements of the bottom end of the pile2. A known retaining device is for example a mudmat.

In order to apply the moment30the first guiding device10and the second guiding device26engage an outer surface29of the pile2for holding the pile2. The moment30is then applied to the pile2by exerting a first force34to the pile2via the first guiding device10in a direction35towards the first orientation33, and exerting a second force36opposite to the first force34to the pile2via the second guiding device26. The first force34and the second force36together constitute the moment30.

The first force34is exerted on the pile2by moving the first guiding device10relative to the base frame9by the first actuator19and/or second actuator21in the direction of the predetermined, first orientation33.

The first force34and the second force36act substantially horizontally on the pile2.

The first force34which the first guiding device10exerts on the pile2can be a predetermined force. The magnitude of said predetermined force is based on the deviation of the pile2from the predetermined first orientation33. When the deviation of the pile2becomes larger, the predetermined force becomes greater, and vice versa.

In order to measure the orientation, and thereby the deviation of the pile2from the predetermined first orientation33a control unit (not shown) is provided which is coupled to the pile guiding system8. The control unit comprises a sensor (not shown) for measuring the orientation of the pile2during installation. When during step e) or after step d) the sensor measures a non-alignment of the pile2with the predetermined first orientation33the control unit actuates the pile guiding system8to apply the moment30to the pile2.

The control unit may comprise a sensor (not shown) for measuring the rate of change of the non-alignment. The control unit then further comprises a PID controller (not shown) which actuates the pile guiding system8to apply the moment30to the pile2based on the first orientation33as set point.

During at least step e) or after step d), or after step d) the first actuator19and/or the second actuator21may be configured to keep the first guiding device10substantially stationary relative to the installation location6in a plane defined by the first direction20and the second direction22while moving the first guiding device10relative to the floating vessel23. This helps in keeping the vessel4in position, i.e. at the installation location.

The floating vessel23comprises a positioning system configured to keep the floating vessel23within a predetermined area. The first guiding device10is movable relative to the floating vessel23over the predetermined area via the first actuator19and/or the second actuator21.

The positioning system can be a dynamic positioning system, or a spread mooring system25.

In the embodiment where the second guiding device26is rigidly connected to the floating vessel23during the reorientation the first guiding device10applies the first force34to the pile2and the second guiding device26exerts the second force36on the pile2. The second guiding device26in this case passively exerts the second force36on the pile2, because the first guiding device10pushes the pile2against the second guiding device26. In a sense the pile2exerts the second force36on the second guiding device26. Because action is reaction, the second guiding device26exerts the second force36on the pile2in the direction opposite to the first force34exerted by the first guiding device10.

In the embodiment where the second guiding device26is movable relative to the first guiding device10via a third actuator63and/or a fourth actuator in the first direction20and/or second direction22, respectively, during the reorientation the second guiding device26moves in the opposite direction of the first guiding device10. Compared to the embodiment where the second guiding device26is rigidly connected to the floating vessel23, this embodiment allows the second guiding device26to actively exert the second force36on the pile2.

Prior to step b) the opening member51is in the open position52, and wherein after step d) the opening member51is in the closed position53.

Prior to step b) the engaging members41may be in a first, outward position45, i.e. a non-engaging position (FIG.9A). When the pile2is positioned in the guiding opening28the engaging members41are then moved radially inward to their second, engaging position46(FIG.9B) by respective engaging actuators43for engaging the outer surface29of the pile2. The engaging members41are preferably moved to their engaging position once the opening member51is in its closed position53enclosing the pile2.

During step e) the engaging members41are placed at regular intervals around the circumference42of the pile2.

When step e) has finished, the engaging member41are moved back to their first position.

When the pile2has reached its target depth, i.e. when step e) has finished, the opening member51is moved to the open position52. This way, the vessel4is able to move away from the pile2.

Each engaging member41may comprise a resilient member11for providing the resilient pile2connection between the pile2and the respective guiding device.

When during step e) the pile2is driven deeper and deeper into the seabed3this will generally have an effect on the stiffness of the pile2, i.e. the pile2will act stiffer. This has an effect on the pile motions and the natural period205thereof. In order to allow the natural period205of the pile motions to remain longer than the dominant wave period203the resilient member11is adjustable via an adjusting member49. The adjusting member49can decrease the stiffness to a lower stiffness during the downward50moving of the pile2into the seabed3when the stiffness of the soil, and thus the pile2increases. This can be done based on predetermined soil calculations, wherein for each penetration depth a connection stiffness is predetermined.

The method can also be performed by an embodiment as described in relation toFIGS.26to29, wherein the first guiding device10and the second guiding device26are connected to each other via a main frame65. The main frame65is connected to the base frame9and freely movable relative to said base frame9in a first direction20and/or a transverse, second direction22.

The main frame65is rotatable relative to the intermediate frame66about a first axis69by the first intermediate actuator67and/or a transverse, second axis70by the second intermediate actuator. During step e) or after step d) the first intermediate actuator67and/or the second intermediate actuator keep the main frame65substantially stationary relative to the pile2while moving the main frame65relative to the floating vessel23.

The pile guiding system8with the main frame65applies the moment30to the pile2by rotating the main frame65about the first axis69with the first intermediate actuator67and/or the second axis70with the second intermediate actuator68, see alsoFIG.33.

In another application a method is provided for assisting to keep a floating vessel23at an installation location6during installation of a pile2into a seabed3at the installation location. The method comprises the steps:a) providing the floating vessel23and a pile guiding system8comprising a first guiding device10and a second guiding device26connected to said floating vessel23at the installation location,b) positioning the pile2in the guiding opening28of the pile guiding system8, seeFIGS.3and4,c) lowering the pile2to the sea bed, seeFIG.4toFIG.5,d) fixing a bottom end of the pile2to the seabed3in a horizontal direction,e) keeping the first guiding device10substantially stationary relative to the installation location,
wherein when the vessel4moves away from the installation location6the second guiding device26assists in moving the floating vessel23back to the installation location6by a force induced by the pile2on the second guiding device26in a direction35towards the installation location.

An advantage of this method is that when the floating vessel23comprises a dynamic positioning system for keeping the vessel4within a predetermined area, a control unit that may be provided for controlling the first guiding device10does not have to be coupled with the dynamic positioning system of the floating vessel23.

The method for moving the non-aligned pile2back to the predetermined, first orientation33is schematically shown inFIG.32for a pile guiding system8as shown inFIGS.3to25. Said method is schematically shown inFIG.33for a pile guiding system8comprising a main frame as shown inFIGS.26-29.

FIG.32Ashows the pile2in the predetermined, first orientation33. The vessel4is positioned at the installation location6. The pile2is horizontally fixed in the soil, i.e. the seabed3. The first guiding device10and the second guiding device26are in a begin position, i.e. at the installation location.

FIG.32Bshows the pile2in a tilted position, i.e. the non-aligned position32. The first guiding device10and the second guiding device26are still in the begin position. The pile2engages the first guiding device10which results in a pushing away of the vessel4.

FIG.32Cshows the pile2in the non-aligned position32and the vessel4in a position away from the installation location. The vessel4has been moved due to the force of the pile2on the first guiding device10as shown inFIG.32B.

In order to move the pile2back to the predetermined, first orientation33the first guiding device10is moved towards the installation location. The right side of the first guiding device10thereby exerts the first force34on the right side of the pile2. The movement of the first guiding device10relative to the second guiding device26results in the exertion of the second force36on the pile2. The second force36is exerted on the left side of the pile2with a left side of the second guiding device26. First force34and the second force36together constitute the moment30applied on the pile2. The pile2will be moved back to the predetermined, first orientation33. In addition, the floating vessel23will also be moved back towards the installation location.

FIG.33schematically shows the pile2and the vessel4in the same position as shown inFIG.32C. The moment30is however applied via vertical forces via resilient members and/or third and fourth actuators67,68instead of via horizontal forces, i.e. vertical forces are exerted on the vessel4, while the forces exerted on the pile2are horizontal forces.

FIG.34schematically shows an example of an assembly1comprising a floating vessel23and a pile guiding system8having only a first guiding device10and not a second guiding device26. When the pile2tilts, the vessel4is pushed away from the installation location. In order to move the pile2back to the predetermined, first orientation33, the vessel4has to provide all the force via its thrusters96.

FIG.35schematically shows the pile guiding system8and the method for assisting in keeping the vessel4at the installation location. InFIG.35the vessel4is shown in a position away from the installation location. The bottom end of the pile2is horizontally fixed in the seabed3. In order to move the vessel4back to the installation location, the first guiding device10is kept stationary relative to the installation location. When the vessel4moves the second guiding device26moves with it. When the vessel4, and thus the second guiding device26move beyond a predetermined position this will result in the second force36on the second guiding device26which is exerted by the pile2. The second force36is exerted on a left side of the second guiding device26with a left side of the pile2. The first guiding device10exerts the first force34. This will keep the vessel4at the installation location, or at least prevents the vessel4to move beyond a predetermined position. The invention reduces the amount of power required by the thrusters to keep the vessel4at the installation location.

When the pile2has reached a penetration depth at which it is stable, the pile guiding system8is also suited to act as a pile holding device, or pile anchoring device. The pile guiding system8may be kept connected to the stable pile while other actions are performed on the pile, for example the placement of a wind turbine. The connected pile guiding system8, or then pile holding or pile anchoring system, may aid or even replace the positioning system of the vessel4for keeping the vessel in position. The pile therefore takes up at least a part of the loads. The use of the resilient member is beneficial as it reduces the loads on the system and the resilient member may be actively tuned for the vessel its surge and sway periods to be longer than the predominant wave periods. This works for the pile guiding system8with the first guiding device10and second guiding device26, but also for the pile guiding system8with only the first guiding device10. So instead of the resilient member11being configured to keep the natural period205of the pivoting movement of the pile about the seabed caused by the waves during installation thereof longer than the dominant wave period203of the wave spectrum200at the installation location, the resilient member11for the pile anchoring system is configured to keep the surge and sway periods of the vessel longer than the predominant wave period by providing the resilient connection with a low connection stiffness13.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms “a” or “an”, as used herein, are defined as one or more than one. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.