The present invention relates to the field of guiding piles into the seafloor in such a way that they are placed at specific distances and/or orientations with respect to each other. For this purpose it is known to provide a pile guiding system.

WO2017/155402 discloses a pile guiding system that allows for a variety of placement of piles, e.g. four piles in a square arrangement or three in a triangular arrangement. The system comprises pile guiding apparatuses that each have a sleeve through which the pile passes when being driven into the seafloor. The sleeve is provided with an upper and a lower guide assembly. Each assembly comprises multiple guide mechanisms distributed about the circumference of the sleeve. Each mechanism comprises a slider, a rotatable link, and an actuator to move the slider and thereby the link between extended and retracted positions thereof. Dependent on the diameter of the pile, links of a selected lengths are placed the guiding mechanism.

In WO2017/155402, see in particular figures 1 - 3 thereof, each pile guiding apparatus is provided with a group of upper bracing connectors and a group of lower bracing connectors. Each upper group has two pairs of connectors configured for a square configuration of the pile guiding system, see figure 1 , and the lower group has two connectors for the square configuration. For this configuration the system has four brace elements, each connecting the pile guiding apparatus at one corner of the square to a pile guiding apparatus at a neighboring corner of the square. The brace elements each comprises a truss with two upper chords and one lower chord. The ends of the chords have flanges with bolt holes, just like to connectors on the sleeves. Bolts are used to connect a brace element to the sleeve. For a triangular configuration of the pile guiding system, see figure 2, each upper group of connectors has two other pairs of connectors at a different angular orientation than the pairs used for the square configuration. The lower group has another two connectors, also at a different angular orientation than the ones used for the square configuration.

A first aspect of the invention relates to the issue of providing multiple pile arrangements with a piling system, in particular multiple triangular arrangements of piles. In the pile guiding system of WO2017/155402 a smaller (or larger) triangular placing of the three piles requires the use of brace elements of different lengths. So, if it is desired to switch from one triangular configuration of the system to a triangular configuration of different dimensions, all bolts have to be loosened to disassemble the brace elements from the sleeves of the three apparatuses. Then bracing elements of a different length need to be bolted to the sleeves of the three apparatuses, so that the system is ready for operation again.

The first aspect of the invention aims to provide an improved pile guiding system or at least an alternative to the known system. For example, the first aspect of the invention aims to reduce time and effort when changing the dimensions of the triangular configuration.

According to the first aspect of the invention a pile guiding system is provided for guiding three piles into a seafloor. For example, the three piles are installed in the seafloor so that later a tripod or jacket can be mounted thereon, the tripod or jacket - for example - serving as foundation of an offshore wind turbine.

The inventive pile guiding system comprises a frame that is triangularly shaped in a top view having three vertices. At each vertex of the frame a pile guide apparatus for guiding one pile into the seafloor is provided. At least one, preferably all three, pile guiding apparatus is pivotally connected to the frame about a vertical pivot axis so as to provide a first position and a second position of the pile guiding apparatus. The pivotal pile guiding apparatus is lockable in both the first position and second position relative to the frame.

Due to the pivotal mounting of one, two, or as preferred all three, of the pile guiding apparatus(es) of the system on the triangular frame, a different dimension of the triangular pile placement can be achieved very easily. Compared to the approach in WO2017/155402 there is no need for extensive disassembly and re-assembly of the system when making this switch.

In an embodiment, at least two of the three pile guiding apparatuses are pivotally connected to the frame about a respective vertical pivot axis so as to provide a first position and a second position of the pile guiding apparatus. When the at least two apparatuses are in the first position thereof, the three apparatuses are arranged in accordance with a first circle having a first radius. When the at least two apparatuses are in the second position thereof, the three apparatuses are arranged in accordance with a second circle having a second radius, wherein the first radius is smaller than the second radius. In an embodiment, all three pile guiding apparatuses are pivotally connected to the frame about a respective vertical pivot axis so as to provide a first position and a second position of the pile guiding apparatus. Preferably, the embodiment is such that the first circle obtained when all three apparatuses are in their first position and the second circle obtained when all three apparatuses are in their second position are concentric.

In embodiments, the pile guiding system further comprises an actuation system to pivot each pivotal pile guiding apparatus relative to the frame. It is noted that pivoting of the one or more apparatuses can be done, for example, with the frame being placed on deck of a vessel such that the apparatuses are clear of the deck and thus readily pivotal relative to the frame, e.g. by the actuation system when present or by some other approach. For example, pivoting is done by temporary jacks that are not permanently integrated in the pile guiding system. Interface points for the temporary jacks may be provided on the frame and the sleeve of the apparatus.

It is noted that, preferably, the pile guiding apparatuses are detachable mounted to the triangular frame, e.g. by detaching the pivot connection to the frame. In embodiments, the system additionally comprises a square frame, seen in a top view thereon, that is configured at the four corners thereof to mount thereon the pile guiding apparatuses when detached from the triangular frame of the system as well as an extra pile guiding apparatus, preferably of identical embodiment as the ones detached from the triangular frame. This allows for the use of the pile guiding apparatuses employed in the context of the first aspect of the invention, also in conjunction with a square frame (or otherwise rectangular frame) when four piles are to be installed in the seafloor.

In an embodiment, the frame includes a location corresponding to the center of mass of the pile guiding system configured to connect to a load connector of a lifting device.

In embodiments, each pile guiding apparatus comprises:

- a sleeve having a longitudinal axis and configured to guide a pile;

- a base part that is moveably connected to the sleeve, which base part comprises a main body and a mud mat that is configured to engage with the seafloor, e.g. said mud mat being releasably connected to the main body; and

- an actuation assembly arranged between the sleeve and the base part and configured to move the base part in a direction parallel to the longitudinal axis of the sleeve and/or to pivot the base part about a pivot axis perpendicular to the longitudinal axis of the sleeve, e.g. the pivot axis being located near or at a bottom part of the sleeve. For example, as preferred, the actuation assembly comprises two pairs of hydraulic cylinders arranged at opposite sides of the sleeve, wherein one pair of hydraulic cylinders is able to pivot the base part relative to the sleeve about a first pivot axis and the other pair of hydraulic cylinders is able to pivot the base part relative to the sleeve about a second pivot axis different from the first pivot axis, the first pivot axis preferably being orthogonal to the second pivot axis.

In an embodiment, the mud mat comprises:

- a plate member with a through-hole to allow passage of a pile;

- an inner rim extending downwards from the plate member and delimiting the through-hole; and

- an outer rim extending downwards from the plate member at a distance from the outer rim, for example wherein a height of the inner rim is larger than a height of the outer rim.

In an embodiment, the mud mat comprises two or more ribs extending between the inner rim and the outer rim, e.g. radial ribs. For example, a height of the inner rim is larger than a height of the outer rim and a height of the two or more ribs gradually increases from the height of the outer rim at the outer rim to the height of the inner rim at the inner rim.

In embodiments, the mud mat includes one or more connection members to releasably connect the mud mat to the main body. Preferably, the mud mat further includes one or more alignment members to align the mud mat with a main body, for example the one or more alignment members are configured to mainly transfer horizontal loads between mud mat and main body, and wherein the one or more connection members are configured to mainly transfer vertical loads between mud mat and main body.

In embodiments, the mud mat further comprises a jet system to jet fluid downwards from the mud mat.

In embodiments, each pile guiding apparatus further comprises a noise mitigation system that is arranged on the sleeve and/or the base part and configured to provide an air bubble curtains around the sleeve and the pile while being guided by the sleeve. For example, the noise mitigation system is configured to provide air bubble curtains at different heights of the apparatus and/or the noise mitigation system is configured to provide a plurality of air bubble curtains at different distances from the sleeve.

In embodiments, each pile guiding apparatus further comprises:

- at least two individually controllable guide assemblies that are vertically spaced along the sleeve, wherein each guide assembly comprises at least two actively controllable guiding members distributed around the circumference of the sleeve, wherein each guiding member is moveable in a direction at least perpendicular to a longitudinal axis of the sleeve;

- a control system; and

- a measurement system, wherein the measurement system is configured to measure a position of the guiding members, and wherein the control system is configured to control movement of the guiding members based on an output of the measurement system.

An advantage of the apparatus with the above at least two individually controllable guide assemblies is that all guiding members are actively controlled based on their relative position to the sleeve or to the pile. This allows to easily adapt to piles having different diameters or a pile having a changing diameter over the length thereof as well as easily setting or adjusting an orientation or position of the pile. As a result thereof, an increased flexibility of the pile guiding apparatus is achieved.

In an embodiment, the measurement system is further configured to measure a force exerted by one or more guiding members on a pile. This allows the control system to control the clamping or guiding force exerted on the pile by the guide assemblies. Alternatively or additionally, the measured force may allow overload protection of a respective guiding member by configuring the control system to control the guiding members such that a force exerted by one or more guiding members does not exceed a predetermined value based on an output of the measurement system.

In an embodiment, each guide assembly comprises at least three guiding members, preferably four guiding members, e.g. arranged as two pairs of guiding members positioned at opposite sides of the sleeve, so that each pair holds and positions the pile in a distinct direction.

In an embodiment, one or more guiding members, preferably all guiding members of at least one guide assembly, have a retracted position in which the guiding member is arranged in or beyond a sidewall of the sleeve to provide an unobstructed opening or passage. In an embodiment, this only applies to the upper guide assembly, especially in case the lower guide assembly is arranged at a level a top side of a pile is unlikely to reach as desired position. This has the advantage that the lower guide assembly is able to guide the pile the entire time and that a pile driving apparatus does not have to pass the lower guide assembly.

In an embodiment, the guiding members are each provided with one or more rollers or pads to engage with a pile. In an embodiment, the control system is configured to control the guiding members such that undesired motions of the pile are dampened and/or compensated. This allows, for example, active damping of pile motion.

In an embodiment, the guiding members are moveable using an actuation system, preferably a hydraulic actuation system, wherein the actuation system comprises a passive damping system.

In an embodiment, the apparatus comprises a damping system, either active or passive.

In an embodiment, the damping system may include a valve, e.g. a pressure setting valve, for instance a proportional pressure setting valve, setting a pressure for a hydraulic cylinder at which the valve opens to allow the corresponding guiding member to move and apply damping. This valve may be adjustable to adjust said pressure.

In an embodiment, the damping system includes a valve, e.g. a proportional valve, to set a damping coefficient of the damping system or part thereof for one or more corresponding guide members.

In an embodiment, the damping system may include different damping modes and a switch, e.g. a logic valve, to switch between damping modes.

In an embodiment, the damping system or damping is only provided for the upper guide assembly of the apparatus.

In an embodiment, the measurement system and control system include at least two different connections between at least one sensor of the measurement system and the control system, so that in case one of the connections is lost, the other connection still remains functional to allow the control system to function.

In an embodiment, the control system may include two control units which are both connected to the measurement system and the guiding members, so that in case of failure of one of the control units, the other control unit can still control movement of the guiding members based on an output of the measurement system.

The first aspect of the invention also relates to a pile guiding system comprising a frame and at least two pile guiding apparatuses connected to the frame for guiding a pile into a seafloor, wherein at least one apparatus is moveably, e.g. pivotally, connected to the frame. In an embodiment, at least one apparatus is pivotable relative to the frame about a substantially vertically extending pivot axis. In an embodiment, all apparatuses except one are moveably connected to the frame. Preferably, all apparatus are moveably connected to the frame. For example, the at least one apparatus that is moveably connected to the frame has a first position and a second position, wherein, preferably, a distance between the at least two apparatus is smaller for the at least one apparatus being in the first position than for the at least one apparatus being in the second position. In embodiments, the pile guiding system comprises at least three apparatus for guiding a pile into a seafloor, wherein at least two apparatus are moveably mounted to the frame, wherein the at least three apparatus are arranged in accordance with a first circle having a first radius when the at least two apparatus are in a first position, and wherein the at least three apparatus are arranged in accordance with a second circle having a second radius when the at least two apparatus are in a second position, the first radius being smaller than the second radius. For example, the first circle and the second circle are concentric. For example, the moveable apparatus(es) are lockable in at least one position relative to the frame. For example, the system further comprises an actuation system to move the pile guiding apparatus relative to the frame.

The first aspect of the invention also relates to a method for guiding three piles into the seafloor, wherein use is made of the inventive system.

According to a second aspect of the invention, there is provided a pile guiding apparatus for guiding a pile into a seafloor, e.g. for use in the system of the first aspect of the invention, the apparatus comprising:

- a sleeve to guide a pile;

- a base part moveably connected to the sleeve; and

- an actuation assembly arranged between the sleeve and the base part and configured to move the base part in a direction parallel to a longitudinal axis of the sleeve and/or to pivot the base part about a pivot axis perpendicular to the longitudinal axis of the sleeve.

In an embodiment of the second aspect, the base part comprises a main body and a mud mat configured to engage with the seafloor. Preferably, the actuation assembly is arranged between the sleeve and the main body of the base part. In an embodiment, the mud mat is releasably connected to the main body. In an embodiment, the mud mat is a mud mat according to the third aspect of the invention as described below. In an embodiment, the pivot axis perpendicular to the longitudinal axis of the sleeve is located near or at a bottom part of the sleeve.

The second aspect also relates to a pile guiding system comprising a frame and at least two pile guiding apparatuses according to the second aspect of the invention that are connected to the frame, e.g. movably, e.g. pivotally, e.g. as described according to the first aspect of the invention.

In an embodiment, the frame is connected to the sleeve of the respective at least two pile guiding apparatuses.

In an embodiment, the actuation assembly arranged between the sleeve and the base part comprises two pairs of hydraulic cylinders that are arranged at opposite sides of the sleeve, wherein one pair of hydraulic cylinders is configured to pivot the base part relative to the sleeve about a first pivot axis and the other pair of hydraulic cylinders is configured to pivot the base part relative to the sleeve about a second pivot axis different from the first pivot axis, the first pivot axis preferably being orthogonal to the second pivot axis.

The second aspect of the invention further relates to a method for operating a pile guiding apparatus according to the second aspect of the invention, the method comprising the following steps: a. positioning the pile guiding apparatus on the seafloor; and b. orienting the longitudinal axis of the sleeve relative to the base part in accordance with a desired orientation of the pile to be guided by the sleeve.

In an embodiment, step b. only includes pivoting the base part relative to the sleeve.

In an embodiment, the pile guiding apparatus is part of a pile guiding system according to the second aspect of the invention, wherein the method comprises the step of leveling the pile guiding system by carrying out step b.

In an embodiment, step b. includes translating the sleeve relative to the base part of the apparatus.

The second aspect of the invention also relates to a method for operating a pile guiding system according to the second aspect of the invention, wherein each base part comprises a main body and a mud mat configured to engage with the seafloor, and wherein the method comprises the following steps: a. positioning the pile guiding system on the seafloor; and b. pivoting at least one of the mud mats relative to the respective sleeve in order to pressurize the topsoil of the seafloor beneath said at least one mud mat and/or lower the at least one mud mat into the seafloor.

In an embodiment, the at least one mud mat is a mud mat according the third aspect of the invention.

In an embodiment, pivoting of step b. is first carried out about a first pivot axis and subsequently about a second pivot axis perpendicular to the first pivot axis.

In an embodiment, the method further includes the step of leveling the pile guiding system by orienting the longitudinal axis of at least one sleeve relative to the corresponding base part in accordance with a desired orientation of the pile to be guided by said sleeve. Preferably, step b. is carried out prior to the leveling of the pile guiding system.

Pivoting of the step b. may be carried out such that it can be called wiggling, wobbling or rocking.

According to a third aspect thereof, the invention relates to a mud mat for a pile guiding apparatus, e.g. for application in the first aspect and/or second aspect of the invention. The mud mat comprises:

- a plate member with a through-hole to allow passage of a pile;

- an inner rim extending downwards from the plate member and delimiting the through-hole; and

- an outer rim extending downwards from the plate member at a distance from the outer rim.

In an embodiment, a height of the inner rim is larger than a height of the outer rim.

In an embodiment, the plate member has a constant thickness. Alternatively, the plate member has a thickness that increases from the outer rim to the inner rim.

In an embodiment, the mud mat further includes two or more ribs extending between the inner rim and the outer rim. As a result thereof, compartments are formed that are each delimited by the inner rim, the outer rim and two ribs. In an embodiment, in particular when the plate member has a constant thickness and the height of the inner rim is larger than a height of the outer rim, a height of the two or more ribs gradually increases from the height of the outer rim at the outer rim to the height of the inner rim at the inner rim.

In an embodiment, in particular when the plate member has a thickness that increases from the outer rim to the inner rim and the height of the inner rim is larger than a height of the outer rim, a height of the two or more ribs is constant.

In an embodiment, the plate member of the mud mat has a ring shape, preferably with a plane top surface and a conical bottom surface.

In an embodiment, the mud mat includes one or more connection members, e.g. pin connections, that are configured to releasably connect the mud mat to a main body of a base part of a pile guiding apparatus.

In an embodiment, the mud mat includes one or more alignment members that are configured to align the mud mat with a main body of a base part of a pile guiding apparatus.

In an embodiment of the mud mat, the one or more alignment members are configured to mainly transfer horizontal loads between mud mat and main body, and the one or more connection members are configured to mainly transfer vertical loads between mud mat and main body.

In an embodiment, the mud mat further comprises a jet system or part thereof to jet fluid downwards from the mud mat. The jet system may be provided at a circumference of the mud mat and/or be integrated in the plate member.

A fourth aspect of the invention relates to a pile guiding apparatus for guiding a pile into a seafloor, e.g. for application in any of the first, second, and/or third aspect of the invention, the apparatus comprising:

- a sleeve;

- at least two individually controllable guide assemblies vertically spaced along the sleeve through which the piles are guided, wherein each guide assembly comprises at least two actively controllable guiding members distributed around the circumference of the sleeve, wherein each guiding member is moveable in a direction at least perpendicular to a longitudinal axis of the sleeve; - a control system; and

- a measurement system, wherein the measurement system is configured to measure a position of the guiding members, and wherein the control system is configured to control movement of the guiding members based on an output of the measurement system.

The fourth aspect of the invention also relates to a pile guiding system comprising a frame and at least two apparatus according to the fourth aspect of the invention, preferably three or four apparatuses, connected to the frame.

The fourth aspect of the invention also relates to a method for using a pile guiding apparatus according to the fourth aspect of the invention, wherein one of the at least two guide assemblies is an upper guide assembly and another of the at least two guide assemblies is a lower guide assembly, and wherein the method comprises the following steps: a. positioning the pile guiding system on the seafloor; b. providing the guiding members of the guide assemblies in a position to allow the introduction of a pile; c. lowering a pile into the sleeve such that the pile is in between the guide members of the upper guide assembly and above the lower guide assembly; d. moving the guide members of the upper guide assembly in engagement with the pile; e. lowering the pile in between the guide members of the lower guide assembly while the pile is guided by the guide members of the upper guide assembly; and f. moving the guide members of the lower guide assembly in engagement with the pile.

In an embodiment, step d. includes a lock, e.g. a hydraulic lock, of the guiding members of the upper guide assembly. This may ensure that the guiding members remain in position even in case of power failure.

According to a fifth aspect of the invention, there is provided a pile guiding apparatus for guiding a pile into a seafloor, e.g. for use in any of the first, second, third, and/or fourth aspect of the invention, the pile guiding apparatus comprising:

- a sleeve;

- a base part to support the sleeve from the seafloor; and

- a noise mitigation system arranged on the sleeve and/or the base part for providing air bubble curtains around the sleeve and the pile while being guided by the sleeve. In an embodiment, the noise mitigation system includes hoses or conduits provided with a plurality of holes and an air supply system to provide air, preferably pressurized air, to the hoses or conduits.

In an embodiment, the noise mitigation system is configured to provide air bubble curtains at different heights of the apparatus, e.g. by arranging flexible hoses at different heights on the exterior of the sleeve and/or the base part.

In an embodiment, the noise mitigation system is configured to provide a plurality of air bubble curtains at different distances from the sleeve. In top cross-sectional view, the air bubble curtains may form concentric circles of different diameter.

It will be appreciated that features and embodiments relating to one aspect of the invention may be combined with one or more embodiments and/or features relating to one or more other aspects of the invention where appropriate. Examples thereof can for instance be found in relation to the figures and the description of the figures provided below.

Aspects of the invention will now be explained in more detail with reference to the figures, in which like parts are indicated using like reference symbols, and in which:

Fig. 1 schematically depicts a side view of a pile guiding system according to an embodiment of the invention being lifted from a vessel;

Fig. 2 schematically depicts a side view of the pile guiding system of Fig. 1 when positioned on a seafloor;

Fig. 3 schematically depicts a top view of the pile guiding system of Fig. 1 ;

Fig. 4 schematically depicts in more detail one apparatus for guiding a pile of the pile guiding system of Fig. 1 during embedding of a base part of the apparatus into the seafloor;

Fig. 5 schematically depicts the pile guiding system of Fig. 1 after being leveled;

Figs. 6-13 schematically depict different stages during a pile guiding method according to an embodiment of the invention;

Fig. 14 schematically depicts the pile guiding system of Fig. 1 after completing the pile guiding method for all piles;

Fig. 15 schematically depicts the pile guiding system of Fig. 1 being lifted from the seafloor;

Fig. 16 schematically depicts a step during a pile guiding method according to another embodiment of the invention; Fig. 17 schematically depicts a side view of a pile guiding system according to a further embodiment of the invention positioned on a seafloor;

Fig. 18 schematically depicts the pile guiding system of Fig. 17 positioned on a vessel;

Fig. 19 schematically depicts two oppositely arranged guiding members of an apparatus for guiding a pile of a pile guiding system according to an embodiment of the invention;

Fig. 20 schematically depicts a bottom perspective view of mud mat of the pile guiding system of Fig. 1 ; and

Fig. 21 schematically depicts a top perspective view of the mud mat of Fig. 20.

It is first noted that the drawings are schematic in nature and that details, which are not necessary for understanding the present invention, may have been omitted. Furthermore, the drawings provided illustrate an embodiment of the invention by way of example. Different aspects of the invention may be combined in the below description and drawings. However, it will be apparent that different aspects, embodiments and/or features may as well be used in isolation and/or various combinations as is also apparent from the appended claims.

Fig. 1 depicts a pile guiding system PGS according to an embodiment of the invention and a portion of a vessel V with a deck DE used to transport the pile guiding system PGS from and to an offshore installation site.

The pile guiding system PGS includes a frame F and connected to this frame F, three apparatus for guiding a pile, alternatively referred to as pile guiding apparatus PGA, of which only two apparatus PGA are visible in Fig. 1.

Reference is made to Fig. 3 in which the pile guiding system PGS is shown in top view. Fig. 3 clearly depicts a triangularly shaped frame F and three apparatus PGA.

The pile guiding system PGS can be used to guide three piles, e.g. foundation piles, into a seafloor in a predetermined mutual position and/or orientation as will be explained below in more detail. It is explicitly noted here that the number of piles that can be guided into the seafloor is not essential for some of the aspects of the invention and that aspects of the invention may relate to pile guiding systems being configured to guide one, two, three, four, five or more piles depending on the installation demands. A pile guiding system for three piles as depicted in Fig. 1 and 3 (and other figures as well), may be preferred as it allows to install three piles to support a structure, so that the complete construction or the structure may be statically determinate, e.g. for an offshore wind turbine foundation.

Referring again to Fig. 1, the pile guiding system PGS is transported from and to an installation site by a vessel V allowing to use the pile guiding system PGS at different offshore installation sites.

The deck DE of the vessel V may be equipped with support members SM configured to engage with the system PGS, preferably with the frame F thereof or with a respective lower portion of a corresponding apparatus PGA. The support members SM may be suitable to hold the pile guiding system PGS during transport. When the pile guiding system PGS is to be used, a crane or other lifting device may lift the pile guiding system PGS from the vessel as depicted using arrows A1.

The vessel V may include a crane to perform the operation depicted in Fig. 1 , but it is also possible that a crane on another vessel is used to lift the pile guiding system PGS from the deck DE, thereby allowing the vessel V to be embodied relatively simple, e.g. as a transport barge or other vessel.

Fig. 1 only depicts a load connector LC of a crane connected to the frame F of the pile guiding system PGS. Other parts, such as cables and the crane are omitted from the drawings as they are considered to be known to the person skilled in the art. In order to keep the pile guiding system PGS substantially level during lifting by the crane, the load connector LC may be connected to the frame F at a location LO, see also Fig. 3, corresponding to the center of mass of the pile guiding system PGS.

Fig. 2 depicts the pile guiding system PGS after being lowered into a body of water and positioned on a seafloor SF. As is common, the seafloor SF may not form a plane surface parallel to the horizontal, so that initially the pile guiding system PGS may be positioned on the seafloor SF in an inclined orientation as shown in Fig. 2.

Fig. 4 depicts one of the pile guiding apparatus PGA in more detail after being positioned on the seafloor SF as shown in Fig. 2. The pile guiding apparatus PGA is connected to the frame F of which a part is visible in Fig. 4. The pile guiding apparatus PGA includes a sleeve SL and a base part BP moveably connected to the sleeve SL. In this embodiment, the base part BP is connected to the sleeve SL using four hydraulic cylinders C1-C4 of which only hydraulic cylinders C1-C3 are visible in Fig. 4. Hydraulic cylinder C1 and hydraulic cylinder C3 are arranged at opposite sides of the sleeve SL as are hydraulic cylinder C2 and hydraulic cylinder C4. The hydraulic cylinders C1-C4 are in this embodiment evenly distributed around the sleeve SL.

In Figs. 1 and 2, all hydraulic cylinders C1-C4 are in a retracted position. Extending one or more hydraulic cylinders in a direction parallel to a longitudinal axis of the sleeve SL allows to move the base part BP in a direction parallel to the longitudinal axis of the sleeve SL and/or to pivot the base part BP about a pivot axis perpendicular to the longitudinal axis of the sleeve SL.

The base part BP is formed by a main body MB and a mud mat MM. The hydraulic cylinders C1-C4 are connected to an upper side of the main body MB while the mud mat MM is connected, preferably, releasably connected to a lower side of the main body MB.

Figs. 20 and 21 depict the mud mat MM in more detail. Fig. 20 depicts a bottom perspective view of the mud mat MM and Fig. 21 depicts a top perspective view of the mud mat MM.

The mud mat MM in this embodiment has a ring-shaped plate member PM defining a through-hole TH to allow a pile guided in the sleeve SL to pass the mud mat MM. Extending downwards from the plate member PM and delimiting the through-hole TH is an inner rim IR. Extending downwards from the plate member PM at its circumference is an outer rim OR. Extending between the inner rim IR and the outer rim OR are radial ribs RR forming compartments CO below the plate member PM that are delimited by the inner rim IR, the outer rim OR and two radial ribs RR. As can be seen in side views, e.g. Fig. 1 or 2, a height of the inner rim IR is larger than a height of the outer rim OR (when measured from a top surface TS of the plate member to an underside of the respective inner rim IR or outer rim OR). When the plate member PM has a constant thickness, a height of the radial ribs RR gradually increase from the height of the outer rim OR at the outer rim OR to the height of inner rim IR at the inner rim IR. However, as in this embodiment, a thickness of the plate member PM may increase from the outer rim OR to the inner rim IR, preferably such that a height of the radial ribs RR is constant and thus the height of each compartment CO is constant over its entire area. Hence, as shown in this embodiment, the plate member PM preferably has a planar top surface TS and a conical bottom surface BS.

An advantage of the mud mat MM of Figs. 20 and 21 is that when the pile guiding system PGS is positioned on the seafloor SF as shown in Fig. 2, the inner rim IR will first make contact with the seafloor SF and help to fixate the horizontal position of the mud mat MM. A further advantage of the inner rim IR is that it is avoided that mud or soil is pushed towards the through-hole TH where it could be in the way of a to be guided pile and a pile driving apparatus such as a hammer. The conical shape of the bottom surface BS helps in pushing the mud or soil outwards where it cannot do harm.

When the mud mat MM is lowered further into the seafloor SF after the initial contact with the inner rim IR, the muddy topsoil of the seafloor SF gets trapped by the outer rim OR in the compartments CO formed by the inner rim IR, outer rim OR and the radial ribs RR. This may ensure an equal load distribution below the mud mat MM.

As mentioned earlier, the mud mat MM may be releasably connected to the main body MB, for instance using pin connections PC as shown in Fig. 21. In order to limit the horizontal loads applied to the pin connections PC, alignment members AM may be provided to cooperate with respective members on the main body MB allowing to transfer horizontal loads between the main body MB and the mud mat MM. The pin connections PC can then be designed for mainly vertical loads.

The abovementioned possibility to pivot the base part BP, i.e. the mud mat MM, about a pivot axis near or at the bottom part of the sleeve perpendicular to the longitudinal axis of the sleeve SL may be used to carry out one or more of the following operations, namely:

1. compensating for an inclined seafloor SF thereby allowing to properly orient the longitudinal axis of the sleeve SL;

2. pressurizing the muddy topsoil trapped in the compartments CO; and

3. lowering the mud mat into the seafloor.

Although it is possible that compensation for an inclined seafloor SF may be carried out by pivoting the base part only, e.g. when the pile guiding system PGS includes a single apparatus PGA, compensation may have to be combined with leveling of the entire pile guiding system in case of a pile guiding system PGS including at least two apparatus PGA, so that a combination of pivoting and translating the base part BP may be required for at least one pile guiding apparatus PGA as shown in Fig. 5 in which the base part BP of the left pile guiding apparatus PGA is translated as well as pivoted while the base part BP of the right pile guiding apparatus PGA only needed to pivot.

Pressurizing the muddy topsoil in the compartments CO may be obtained by pivoting, e.g. wiggling, the mud mat MM relative to the pile guiding apparatus PGA so that alternately one side of the mud mat MM will be pushed deeper in the seafloor SF thereby pressurizing the muddy topsoil trapped in the compartments and pre-loading the deeper ground layers. Pivoting is preferably carried out in different directions so that the muddy topsoil in all compartments CO is equally pressurized thereby applying an evenly distributed load to the deeper ground layers.

Lowering the mud mat MM into the seafloor may be a result obtained during pressurizing the muddy topsoil, but may alternatively provide more stability and/or allow to reach other layers in the seafloor for support purposes.

An example of pivoting the mud mat MM is shown in Fig. 4 in which the hydraulic cylinder C3 has been extended more than the hydraulic cylinder C1 at the opposite side thereby pushing the right side of the mud mat MM deeper into the seafloor FL than the left side. By subsequently operating the hydraulic cylinders C1 and/or C3 such that the hydraulic cylinder C1 is extended more than the hydraulic cylinder C3, the left side is pushed deeper into the seafloor FL. The same can be done using the hydraulic cylinders C2 and C4 to wiggle the mud mat MM in a perpendicular direction.

An advantage of the compartments CO and in particular pressurizing the muddy topsoil in the compartments CO or lowering the mud mat MM into the seafloor is that the resistance is significantly increased, thereby fixating the pile guiding system PGS to the seafloor SF. An advantage thereof may be that the pile guiding system PGS will follow movement of the piles guided by the pile guiding system PGS and the seafloor SF during an earthquake. This way the piles are not subjected to the inertial loads that would occur when the pile guiding system PGS would be able to slide freely thereby minimizing the chance that the pile guiding system PGS and/or piles are damaged during an earthquake.

As shown in Fig. 5, the hydraulic cylinders of each pile guiding apparatus can be used to level the pile guiding system PGS in which the frame F extends substantially parallel to the horizontal and/or the longitudinal axes of the sleeves SL extend substantially parallel to the vertical. Once the pile guiding system PGS has been positioned on the seafloor SF, the load connector LC may be retracted to leave the pile guiding system PGS behind and use the crane for other purposes, e.g. handling piles to be guided by the pile guiding system PGS. In Fig. 5, the load connector LC is depicted in two positions, namely a position in which the load connector LC is still connected to the frame F and a position in which the load connectors is retracted as also indicated using arrows A2. Fig. 5 further depicts the situation that the right most mud mat MM has been pressed/lowered into the seafloor, for instance as a result of the abovementioned wiggling of the mud mat MM, prior to the leveling of the pile guiding system PGS, and that the left most mud mat MM will not be lowered/pressed into the seafloor SF or will be lowered/pressed into the seafloor after leveling.

Referring to Fig. 3 again, one or more pile guiding apparatus, in this case all three, are moveably, in particular pivotally, connected to the frame F. The triangular frame has three vertices, as done any triangle, and at each vertex a pile guiding apparatus is pivotally mounted.

In the example of Fig. 3, each pile guiding apparatus PGA are pivotably mounted to the frame F to allow a rotation about a respective pivot axis VPA that in use extends substantially vertically.

Connected to the pile guiding apparatus PGA, e.g. to the sleeve thereof, is a locking plate LP. In the exemplary embodiment two holes HL are provided allowing to lock a position of the pile guiding apparatus PGA relative to the frame F in two distinct positions. For example, a locking pin is used. One of the two distinct positions puts a center of the pile guiding apparatus PGA in a position at a distance R1 from the center of mass as shown for the top pile guiding apparatus in Fig. 3, while the other of the two distinct positions puts a center of the pile guiding apparatus PGA in a position at a distance R2 from the center of mass as shown for the bottom right pile guiding apparatus in Fig. 3. The bottom left pile guiding apparatus PGA is shown in both positions simultaneously.

Figs. 6 - 13 depict different stages during a pile guiding method according to an embodiment of the invention which can be carried out by using a pile guiding system PGS as depicted in Figs. 1 - 5. The steps are depicted for a single pile guiding apparatus PGA, but they can be repeated for every pile guiding apparatus PGA of the pile guiding system PGS when necessary. For simplicity reasons, the method is depicted for a non-inclined seafloor SF and cross-sectional views of the pile guiding apparatus PGA.

Fig. 6 depicts a pile guiding apparatus PGA connected to a frame F and supported from a seafloor SF using a base part BP that is moveably connected to a sleeve SL using two hydraulic cylinders C1 , C3. The sleeve SL is provided with an upper individually controllable guide assembly UGA and a lower individually controllable guide assembly LGA vertically spaced along the sleeve through which the piles are guided.

In this embodiment, the upper guide assembly UGA comprises four actively controllable guiding members UGM evenly distributed around the circumference of the sleeve SL of which two guiding members UGM are visible in Fig. 6.

Each guiding member UGM is moveable in a direction at least perpendicular to a longitudinal axis LAS of the sleeve LS between a retracted position as shown in Fig. 6, 7 and 13, in which the guiding member UGM allows the free passage of a pile PI and/or a pile driving apparatus PDA through the sleeve SL, and an operational position as shown for instance in Figs. 7-12, in which the guiding members UGM engage with a pile PI.

In this embodiment, the guiding members UGM comprise rollers or wheels to minimize friction between the guiding members UGM and the pile PI when the guiding members UGM are in the operational position.

Each guiding member UGM is moveable using a hydraulic cylinder HC that is configured to rotate an intermediate member IM holding the guiding member UGM.

Fig. 6 depicts one of the first steps in the pile guiding method in which a pile PI is introduced into the sleeve SL past the upper guide assembly UGA. While doing so, the pile PI may be held by a crane. It is preferred that the pile PI is initially held above the lower guide assembly LGA until the guiding members UGM of the upper guide assembly UGA are moved to the operational position as shown in Fig. 7.

Fig. 7 depicts a top portion of the pile guiding apparatus PGA including the upper guide assembly UGA. The guiding members UGM and thus also the intermediate members IM and the corresponding hydraulic cylinders HC are shown both in the retracted position and the operational position.

Fig. 19 depicts a schematic representation of a guide assembly GA in general, which may be the upper guide assembly UGA or the lower guide assembly LGA of Figs. 6-13. Shown in Fig. 19 are a sleeve SL, two oppositely arranged guiding members GM, corresponding hydraulic cylinders HC and a pile PI. Provided is a measurement system, in this case comprising a sensor per guiding member GM, to measure a position of the guiding members GM. Shown in Fig. 19 are a first sensor SE1 to measure a position X1 of the left guiding member GM and a second sensor SE2 to measure a position X2 of the right guiding member GM. An output of the measurement system is provided to a control system CS configured to control movement of the guiding members GM based on the output of the measurement system.

Typically, a pile PI with a known diameter will be introduced into the sleeve SL. Based on a known diameter of the sleeve SL and a desired position of the pile PI within the sleeve SL, the control system CS is able to calculate the desired position of the guiding members GM to engage the pile PI. Hence, for the situation in Fig. 19, the control system CS may determine that the left guiding member GM has to travel a distance Y1 towards the pile PI and that the right guiding member GM has to travel a distance Y2 towards the pile PI to allow both guiding members GM to engage with the pile PI.

The measurement system may further be configured to measure a force applied between the pile PI and the guiding member GM. Shown in Fig. 19 are a third sensor SE3 to measure a force applied between the pile PI and the left guiding member GM and a fourth sensor SE4 to measure a force applied between the pile PI and the right guiding member GM. The third and fourth sensor SE3, SE4 may for instance be embodied as strain gauge on the respective guiding member GM or other part connected thereto.

An advantage of measuring a force applied between the pile PI and a respective guiding member GM is that it can be determined whether the guiding member GM is actually engaging with the pile PI and that it can be determined what a value of a corresponding clamping force is. Tolerances in the diameter of the sleeve SL and/or the pile PI may result in the control system CS having difficulties to determine the desired position of the guiding members. Additional information in the form of said forces will make it easier for the control system to correctly position the guiding members GM to position the pile PI within the sleeve SL, but will also make it possible to monitor undesired situations in which the applied forces reach a level above a predetermined maximum force having the risk of damage to the pile PI and/or pile guiding system PGS. The control system CS may thus comprise an overload protection protocol allowing to control movement of the guiding members to keep said forces below the predetermined maximum force and prevent damage to the pile PI and/or pile guiding system PGS. In an embodiment, the control system CS may be configured to keep a longitudinal axis LAS of the sleeve SL aligned with a longitudinal axis LAP of the pile PI, i.e. X1 + Y1 = X2 + Y2, at least during the steps depicted in Figs. 6-8. Alternatively or additionally, the position of the guiding members may be locked during one or more steps, so that even in case of power failure, the pile remains guided.

Referring back to Figs. 6 - 13, there may be a difference between the lower guide assembly LGA and the upper guide assembly UGA, e.g. in guiding range, clamping force and/or controlling speed. The lower guide assembly LGA may for instance be mainly used to only center or position the pile PI near the seafloor SF. The upper guide assembly UGA may for instance be mainly used to set an orientation of the pile PI relative to the sleeve SL.

Fig. 7 depicts both the situations that the upper guiding members UGM are in the retracted position and in the operational position. With the upper guiding members UGM in the operational position, a position of the pile PI within the sleeve SL can be controlled before the pile PI is lowered into the lower guide assembly LGA thereby minimizing the risk of damaging the pile PI and/or lower guide assembly LGA.

Fig. 8 depicts in more detail the lower guide assembly LGA while the pile PI is being lowered in between four actively controllable guiding members LGM evenly distributed around the circumference of the sleeve SL of which two guiding members LGM are visible in Fig. 8.

Each guiding member LGM is moveable in a direction at least perpendicular to the longitudinal axis LAS of the sleeve SL between a retracted position as shown in Fig. 6, 8 and 13, in which the guiding member LGM allows a free passage of a pile PI and/or a pile driving apparatus PDA through the sleeve SL, and an operational position as shown for instance in Figs. 9, 11 and 12, in which the guiding members LGM engage with a pile PI.

In this embodiment, the guiding members LGM comprise pads, preferably low-friction pads, to engage with the pile PI in the operational position. The guiding members LGM are provided on a respective arm AR that is pivotable about a respective pivot axis PA to be moveable between the retracted and the operational position. To move an arm AR about a respective pivot axis PA, an actuator (not shown) may be provided, e.g. a hydraulic cylinder. A difference between the upper guide assembly UGA and the lower guide assembly LGA is that the moving range of the guiding members LGM is smaller than the guiding members UGM, with the consequence here that the guiding members UGM have a retracted position in which the guiding members UGM are arranged in or beyond a sidewall of the sleeve to provide an unobstructed opening or passage while the guiding members LGM have a retracted position in which the guiding members LGM are arranged on the inside of the sidewall of the sleeve SL. As a result thereof, a pile PI introduced into the sleeve SL is able to come into contact with the guiding members LGM even when in the retracted position. However, contact can be avoided by using the upper guide assembly UGA that already starts guiding the pile PI before the pile PI is lowered in the lower guide assembly LGA.

Fig. 9 depicts the pile PI being lowered into the lower guide assembly LGA and the guiding members LGM being positioned in the operational position in engagement with the pile PI, so that the pile PI is now guided by both the upper guide assembly UGA and the lower guide assembly LGA.

With the pile being guided by both the upper guide assembly UGA and the lower guide assembly LGA, the position and/or orientation of the pile PI can be set to a desired position and/or orientation, e.g. parallel to the vertical or having a specific inclination. The pile PI can then be lowered into the seafloor, initially due to the weight of the pile PI itself. The position of the guiding members UGM and/or LGM may be locked during self-penetration.

Fig. 10 depicts the situation in which the pile PI has been driven in the seafloor due to its own weight, but cannot be lowered without further aid. To this end, a pile driving apparatus PDA is arranged on the pile PI. The pile driving apparatus PDA may use a moveable mass that is moved up and then released to apply an impulse to the pile PI. The moveable mass may be a rigid mass, but can also be a body of water.

Fig. 11 depicts a pile guiding apparatus PGA while guiding a pile PI into the seafloor during driving of the pile PI into the seafloor with the pile driving apparatus PDA. As the impulse applied by a moveable mass of the pile driving apparatus PDA may cause undesired vibrations in the water that may have a negative influence on sea life.

In this embodiment, the pile guiding apparatus PGA comprises a noise mitigation system configured to provide one or more air bubble curtains ABC around the sleeve SL and the pile PI. The noise mitigation system may for instance include perforated flexible hoses arranged at different heights on the exterior of the sleeve SL. The air bubble curtains ABC are then formed by supplying air to the hoses using e.g. a compressor. The air bubble curtains ABC form a barrier for the vibrations caused by the pile driving apparatus PDA thereby damping the vibrations and reducing the negative influence on surrounding sea life. To increase the damping effect, a plurality of air bubble curtains ABC at different distances from the sleeve SL may be formed as shown in Figs. 11-13. In top cross-sectional view, the air bubble curtains ABC may form (look like) concentric circles with different diameters.

Additionally or alternatively, the upper and/or lower guide assembly, in this embodiment only the upper guide assembly, may be put in damping mode during actively driving the pile PI into the seafloor SF using the pile driving apparatus PDA to dampen and/or compensate for undesired motions of the pile PI.

In Fig. 12, the pile driving apparatus PDA has driven the pile PI to a depth in the seafloor SF such that the pile driving apparatus enters or is about to enter the sleeve SL. The pile driving apparatus PDA in Fig. 12 is just above the upper guide assembly UGA. Typically, the pile driving apparatus PDA is not able to pass the upper guide assembly UGA with the guiding members UGM in the operational position. Further, with the pile PI being driven that far into the seafloor, the effect of guiding the pile PI had diminished so that the guiding members UGM can be retracted to the release position. The pile driving apparatus PDA is then able to drive the pile PI into the seafloor to a situation in which the pile driving apparatus PDA is just above the lower guide assembly LGA as depicted in Fig. 13. As in this example, Fig. 13 depicts the final depth of the pile PI, the guide members LGM of the lower guide assembly LGA can also be moved to the release position. It is noted here that because the pile driving apparatus PDA does not have to be moved past the lower guide assembly LGA, the retracted position of the guide members LGM does not have to allow the passage of the pile driving apparatus per se and thus the moving range of the guiding members LGM does not have to be as large as the moving range of the guiding members UGM.

As mentioned before, the above procedure can be repeated for other pile guiding apparatus PGA of the pile guiding system, also when the pile guiding system PGS is on an inclined surface as shown in Figs.2, 4, 5 and Figs. 14 and 15.

Fig. 14 depicts the situation that the guiding function of the pile guiding system PGS has been fulfilled and the pile guiding system PGS can be removed from the seafloor. To this end, the load connector LC is lowered from a vessel and connected to the frame F. In fig. 14, the load connector LC is depicted in two position, namely a position in which the load connector LC is in a retracted position and a position in which the load connector LC is connected to the frame F as also indicated using arrows A2’. Connecting the load connector LC to the frame allows to lift the pile guiding system PGS from the seafloor SF. As mentioned above in relation to Fig. 4, the mud mat may be partially lowered into the seafloor for increased resistance and/or stability. This may make lifting the pile guiding system PGS after guiding the piles PI harder. To aid in lifting the pile guiding system PGS, the mud mats MM may be provided with a jetting system allowing to jet fluid downwards from the mud mat MM as indicated by arrows A3 in Fig. 15 thereby pushing the mud mat MM and thus the entire pile guiding system upwards from the seafloor SF thereby decreasing the load on the mud mats MM and/or the load connector LC. Fig. 15 further depicts the pile guiding system PGS after being lifted from the seafloor SF.

Fig. 16 depicts a seafloor SF with two piles PI. The left pile PI has already been driven into the seafloor SF to a desired depth. The right pile PI has partially been driven into the seafloor SF and needs to be driven further. This situation may be caused by the procedure described above being interrupted for some reason and retrieving the pile guiding system PGS early for some reason, e.g. caused by weather conditions, operational conditions such as maintenance or repair and/or other circumstances such as an earthquake. To finish the installation of the piles PI, it is possible to use the pile guiding system PGS again as is shown in Fig. 16.

In the example of Fig. 16, the base parts BP are prepositioned in a position in conformity with the seafloor, so that the pile guiding system PGS remains level also after engaging with the seafloor SF to prevent interference with the piles PI. This is different from the process described in relation to Figs. 2, 4 and 5, where the pile guiding system PGS is initially lowered onto the seafloor SF and is leveled only after engagement with the seafloor SF, which is possible there as there are no piles PI present to interfere with.

Further, the guiding members of the lower LGA and upper UGA guide assemblies are positioned in their respective release positions allowing to position the sleeves SL over the piles PI. Once a pile PI has entered a lower guide assembly LGA, the corresponding guiding members may be moved to the operational position to start guiding the pile PI relative to the pile guiding system PGS. Once the pile guiding system PGS has been lowered on the seafloor SF, the process can be resumed and finished, at least for the pile PI on the right.

Fig. 17 depicts a pile guiding system PGS according to another embodiment of the invention. Fig. 17 depicts a seafloor SF, a body of water BWwith a water line WL shown as a solid line for a quiet water surface and as a dashed line for a wavy water surface. The pile guiding system PGS includes at least two pile guiding apparatus PGA connected to each other via a frame F. Each pile guiding apparatus PGA comprises a sleeve SL to guide a pile, and a base part BP moveably connected to the sleeve SL to support the sleeve SL from the seafloor SF. The base part BP is pivotable about a pivot axis PAX using a corresponding hydraulic cylinder HC arranged between the sleeve SL and the base part BP as part of an actuation assembly.

The frame F is connected to a load connector LC with a floating body FB using one or more cables CA. The floating body FB ensures that the load connector LC at least partially extends above the waterline WL for connection to a lifting device, e.g. a crane, on a vessel, while the pile guiding system PGS is on the seafloor SF. An advantage thereof is that it is easier to retrieve the pile guiding system PGS from the seafloor SF.

Preferably, the floating body FB is provided below the waterline WL even in case of waves, so that the cross-sectional area at the waterline WL is relatively small and thus waves have a minimal effect on the load connector LC.

Fig. 18 depicts the pile guiding system PGS and the load connector LC with the floating body FB on a deck DE of a vessel VE. This may be possible due to sufficient length of the cables CA.

Although the above description talks about clamping the pile PI, it is very well possible that guiding the pile PI is carried out with minimal or no clamping at all, meaning that for a pair of guiding members, there is either a force present between the pile and one of the guiding members or between the pile and the other one of the guiding members, but not simultaneously. It is also possible that there is no force present for a certain period of time. Although the above description talk about a mud mat as part of a base part and connected to a main body, the mud mat may alternatively be referred to as foot or sea floor support. Hence, the term mud mat may be replaced by such other wording where appropriate.