Method and system for removing an off-shore foundation pile from a location

Abstract

The invention relates to a method for removing an off-shore foundation pile from a use position in which a lower part of the off-shore foundation pile has been driven into a ground, such that a longitudinal axis of the off-shore foundation pile extends upward, wherein the off-shore foundation pile is rotated around said longitudinal axis, prior to and / or during lifting of the off-shore foundation pile from the ground.

Description

[0001] Title: Method and system for removing an off-shore foundation pile from a location

[0002] The invention relates to a method for removing an off-shore foundation pile from a foundation location. The invention further relates to a system for removing an off-shore foundation pile from a foundation location.

[0003] Off-shore foundation piles, such as monopiles, for founding onshore or, especially, off-shore constructions, such as wind turbine generators or rigs have a lower end driven or otherwise positioned in the ground at a foundation location, such as for example the bottom of a sea or ocean. At the end of their economical and / or technical life span such off-shore foundation piles are decommissioned and need to be removed. Companies using such off-shore foundation piles are obliged to remove the off-shore foundation piles and restore the foundation location to the original situation if the offshore foundation pile is not replaced.

[0004] It is known in the art to remove an off-shore foundation pile by digging the pile out of the ground. This is however cumbersome, if at all possible. For example, if the off-shore foundation pile has been driven into a sea bottom or ocean bottom this may not be possible. Moreover, digging an off-shore foundation pile out of the ground will be very harmful to the environment and will be very costly.

[0005] Furthermore it is known to lift an off-shore foundation pile out of the ground, by pulling at the off-shore foundation pile in axial direction, using a hoisting device such as one or more cranes. If a lower end of an offshore foundation pile has been embedded in the ground, such as soil, it will be held in place by a combination of steel to soil friction, but also rust to soil friction, whereas rust will have formed a crust with the soil surrounding the tower, further resisting pulling the off-shore foundation pile axially out of the soil. Pulling the off-shore foundation pile out of the soil requires high forces, which moreover are hard to predict and control. When pulling axially at an off-shore foundation pile driven into soil a holding force working on the off-shore foundation pile may change, especially reduce dramatically and suddenly, for example when the pile starts moving or when the friction and other mechanical forces acting between the soil and the off-shore foundation pile inside the soil change, for example due to soil conditions at different depths. When the holding force reduces significantly the upward speed of movement of the off-shore foundation pile will increase suddenly and significantly, whereas the pulling force cannot be reduced instantly. This may have as an effect that the off-shore foundation pile may shoot out of the ground uncontrollably, which is highly dangerous. This may also have the effect that lifting vessels used may capsize due to the suddenly reduced friction and increasing speed of movement.

[0006] It has been proposed to reduce the pulling force, leading to reduced and less problematically controllable movement of an off-shore foundation pile. However, this will increase the time necessary for removal of an offshore foundation pile. Moreover, the speed and especially changes in speed of movement of the off-shore foundation pile is still difficult to control. It has further been proposed to use vibrating systems to make the pile to vibrate, releasing the off-shore foundation pile partly from the ground. However such vibration is very detrimental to life around the off-shore foundation pile, especially in a marine setting.

[0007] Accordingly there is a need for an alternative method for removing an off-shore foundation pile from the ground at a foundation location. An aim of the present disclosure is to provide for such method. An aim of the present disclosure is to provide for a method for removing an off-shore foundation pile from the ground at a foundation location which method is environmentally friendly. An aim of the present disclosure is to provide for a method for removing an off-shore foundation pile from the ground at a foundation location which is relatively safe for people, animals and installations and the like surrounding the off-shore foundation pile to be removed. An aim of the present disclosure is to provide for a method for removing an off-shore foundation pile from the ground at a foundation location which leads to relatively little disturbance of the ground from which that off-shore foundation pile is removed. An aim of the present disclosure is to provide for a system for removing an off-shore foundation pile. An aim of the present disclosure is to provide for such system with which an off-shore foundation pile can be released from a ground, such as from soil, which is an alternative to the known systems. An aim of the present disclosure is to provide for a tool suitable for use in releasing an off-shore foundation pile from a ground bound position.

[0008] With a method, system and / or tool according to the disclosure at least one of the drawbacks of the prior art can at least partly be resolved.

[0009] In an aspect a method for removing an off-shore foundation pile from a use position in which a lower part of the off-shore foundation pile has been driven into a ground, such that a longitudinal axis of the pile extends upward, comprises the step wherein the off-shore foundation pile is rotated around said longitudinal axis, prior to and / or during lifting of the off-shore foundation pile from the ground.

[0010] Surprisingly it has been found that by rotating the off-shore foundation pile around the longitudinal axis, the off-shore foundation pile can be released from the ground relatively easily, without undesired disturbance of the environment of the off-shore foundation pile. The offshore foundation pile can then be lifted out of the ground with smaller forces and in a more controllable manner.

[0011] Advantageously in a method of the disclosure the pile is rotated intermittently in a first direction and in an opposite second direction around the longitudinal axis.

[0012] The first and second direction can also be referred to as in a clockwise direction and a counter-clockwise direction or vice versa. By intermittently rotating the off-shore foundation pile the movement of the pile can be controlled securely, whereas a system for obtaining said rotations can be designed relatively easily.

[0013] In the same or further advantageous embodiments of a method of the disclosure a tool is mounted onto the off-shore foundation pile, said tool gripping an outer periphery of the off-shore foundation pile. The off-shore foundation pile is rotated by rotating said tool while gripping the off-shore foundation pile. Preferably the tool comprises a gripping piece for grippingly engaging said outer periphery, wherein the tool has at least one wing extending outward from said gripping piece. In such methods during use at least periodically a force is exerted on said at least one wing for providing a moment relative to the longitudinal axis, for rotating said off-shore foundation pile. More preferably the tool comprises at least two wings, extending in oppositely outward directions, wherein at each wing intermittently at least a pulling force is exerted, to a same side of the offshore foundation pile.

[0014] In the same or further advantageous embodiments of methods of the disclosure at least one line is, preferably at least two lines are attached to the tool for applying pulling forces to the tool. The at least one line can be connected to an anchoring provision at a position spaced apart from the tool.

[0015] An anchoring provision spaced apart from the tool, and hence from the off-shore foundation pile to be removed, can provide in an easy manner for at least one point for receiving pulling forces.

[0016] In the same or further advantageous embodiments at least one of the tool and the anchoring provision comprises at least one of a winch and a sheave system with which said at least one line is given out and taken in.

[0017] By using said winch and / or sheave system the or each wire can be tightened and released for obtaining the desired rotation of the off-shore foundation pile. In the same or further advantageous embodiments the anchoring provision is connected to a further off-shore foundation pile driven into said ground, distanced from said off-shore foundation pile engaged by the tool.

[0018] The further off-shore foundation pile can for example be an offshore foundation pile of an onshore or off shore installation, for example an off-shore foundation pile similar to the off-shore foundation pile to be removed. For example the anchoring provision can be hooked on or around or clamped to the further off-shore foundation pile, preferably at a level horizontal to the level at which the wire or wires are attached to the tool, preferably substantially the same level.

[0019] In alternative embodiments the outer periphery of the off-shore foundation pile is gripped by a gripper tool part of the tool, which gripper tool part is rotated relative to a base tool part which is anchored to said ground, adjacent a lower part of the off-shore foundation pile.

[0020] By anchoring the base tool part to the ground surrounding the part of the pile founded in the ground, such as a sea floor or ocean floor, the tool can be anchored firmly and easily, relatively close to the pile.

[0021] In advantageous embodiments the tool can be anchored to the ground using vacuum, especially vacuum cups or the like systems, making anchoring easy and practical, without large disturbance to the ground, wherein such anchoring can easily be provided for and be released and removed, preferably with the tool.

[0022] In the same or further advantageous embodiments of a method of the disclosure the tool is lowered over an upper end of the off-shore foundation pile, wherein the off-shore foundation pile is gripped preferably relatively close to the ground into which the off-shore foundation pile is founded, such as the water bottom for an offshore off-shore foundation pile. For offshore off-shore foundation piles the tool is preferably mounted to the off-shore foundation pile below the water surface. Preferably a top portion of the off-shore foundation pile and / or a transition piece and / or a platform are removed from the off-shore foundation pile prior to positioning the tool.

[0023] A tool can be used which comprises at least one ballast tank for increasing and decreasing a weight of said tool.

[0024] Such ballast tank allows easy positioning of the tool over and onto the off-shore foundation pile, for example by lifting or floating the tool, when the ballast tank or tanks is cq are relatively empty, whereas the weight of the tool can be increased for improving gripping of the tool on the off-shore foundation pile. Ballast tanks should be understood at least as, but are not limited to water tanks for receiving and releasing water, such as salt water.

[0025] During at least part of the time the off-shore foundation pile is rotated a lifting force can be applied to the off-shore foundation pile too. Thus the off-shore foundation pile can be pulled out of the ground.

[0026] In the same or further elaborations of a method of the disclosure the off-shore foundation pile is rotated around said longitudinal axis reciprocally clockwise and anti-clockwise, preferably over an angle of less than 120 degrees, such as for example less than 90 degrees. More preferably the off-shore foundation pile is rotated over less than 60 degrees, such as for example 40 degrees.

[0027] In advantageous embodiments in a method of the during at least part of the time the off-shore foundation pile is rotated a lifting force is applied to the off-shore foundation pile too, wherein the lifting force is at least partly provided by lines pulling at the tool and / or the off-shore foundation pile in a direction substantially parallel to a longitudinal axis of the off-shore foundation pile, which lines are given out and taken in using at least one constant tension winch. Thus in a practical manner a substantially constant pulling force is applied for pulling the foundation pile out of the ground. Additionally or alternatively the lifting force is at least partly provided by the tool pushing against the ground. Providing a lifting force during rotation of the foundation pile should be understood as at least including providing a lifting force between periods that the pile is rotated, for example when reversing a direction of rotation when reciprocal rotation is applied.

[0028] Preferably in a method of the disclosure the off-shore foundation pile is gripped using a tool which has at least one of a wrench like gripping profile and a wrench like closure mechanism.

[0029] In advantageous embodiments the off-shore foundation pile is gripped for rotation below a water level surrounding the off-shore foundation pile, preferably relatively close to the water bottom. Relatively close should be understood at least as, but is not limited to closer to the water bottom than to the water surface.

[0030] The disclosure is further directed to a system for use during removal of an off-shore foundation pile from the ground. In an aspect such system comprises at least a gripping tool, comprising a gripping piece defining an opening through which an off-shore foundation pile can extend. The gripping piece is designed for gripping a surface portion of the off-shore foundation pile and at least one anchoring system for anchoring the gripping tool at a location spaced apart from the foundation pile. In an aspect a system according to the disclosure comprises at least a gripping tool, at least one, preferably two wires, and at least one anchoring system. The gripping tool comprises a gripping piece defining an opening through which an off-shore foundation pile can extend. The wire or wires is cq are connected or connectable to the gripping tool, spaced apart from a center of said opening, preferably spaced apart from said opening. This should at least be understood as meaning that at least during use the wire or wires extend from the gripping tool and can exert a pulling force to the tool. The or each wire can for example be fixed directly to the tool, or can be connected indirectly, for example through a winch and / or sheave system connected to or part of the tool. The at least one anchoring system is designed for anchoring said at least one wire spaced apart from an off-shore foundation pile to be removed.

[0031] In an aspect a gripping tool according to the disclosure comprises at least a gripping piece defining an opening through which an off-shore foundation pile can extend, and at least two wing elements, extending outward, away from the opening. In embodiments each wing comprises at least one wire point from which a wire extends, said wire point being spaced apart from the opening.

[0032] In this disclosure a wire point should be understood as a last point of contact between a wire and the gripping tool or any element of or provision on and / or in a gripping tool. A wire point can for example be but is not limited to a fixed connection point, a movable connecting point or a guide element, such as a sheave, or a winch provided in or on a gripping tool.

[0033] In preferred embodiments of a gripping tool of the disclosure each of said wire points is designed for guiding a wire from a winch and / or sheave system away from the relevant wing, such that during use the said wires extend in a first direction and second direction respectively, said first direction and second direction enclosing an angle of less than 180 degrees, preferably less than 90 degrees and the wires during use extend at a same side of a vertical plane through the said two wire points.

[0034] In alternative embodiments said wing or one or preferably each of said wings can be provided with an anchoring system, such as a vacuum cup.

[0035] In embodiments the gripping tool comprises a gripper tool part and a base tool part, wherein the base tool part comprises or is connected to the anchoring system, wherein the anchoring system is designed for anchoring to the ground, spaced apart from the off-shore foundation pile, and wherein the gripper tool part is provided in a gripper piece which is part of or connected to the gripper base part, wherein the tool comprises or is connected to a drive for rotating the gripper tool part relative to the base tool part and / or the gripper piece.

[0036] The invention will be further elucidated on the basis of exemplary embodiments which are represented in the drawings. The exemplary embodiments are given by way of non-limitative illustration of the invention. In the drawings schematically:

[0037] Fig. 1 shows an isometric view of an upper part of an off-shore foundation pile with a gripping tool;

[0038] Fig. 2 shows in top view an off-shore foundation pile with a gripping tool and lines, connected to an anchoring system, in fig. 2 by way of example shown as attached to a further off-shore foundation pile;

[0039] Fig. 3A and 3B show an embodiment of a system of the disclosure, in top view as shown in fig. 2 and in side view, respectively;

[0040] Fig. 4 shows in side view an off-shore foundation pile with a gripping tool and a lifting system attached to the off-shore foundation pile;

[0041] Fig. 5 shows in top view a gripping tool of the disclosure;

[0042] Fig. 5A shows a top view similar to fig. 5, for an alternative embodiment of a gripping tool of the disclosure;

[0043] Fig. 5B shows a winch as used in a system of the disclosure;

[0044] Fig. 6 shows in top view an alternative embodiment of a gripping tool according to the disclosure;

[0045] Fig. 7 shows in top view a further alternative embodiment of a gripping tool of the disclosure;

[0046] Fig. 8 - 10 show in top view further embodiments of a system of the disclosure;

[0047] Fig. 11A and B show an alternative embodiment of a system according to the disclosure, in top view and side view respectively;

[0048] Fig. 12A - C show a system according to the disclosure, for example according to fig. 11, in three consecutive steps of a method of the disclosure; Fig. 13 shows a further alternative embodiment of a system of the disclosure.

[0049] In this description embodiments of the invention will be described with reference to the drawings by way of example only. These embodiments should by no means be understood as limiting the scope of the disclosure. At least all combinations of aspects, elements and features of the embodiments shown and discussed are also considered to have been disclosed herein. In this description the same or similar elements and features will be referred to by the same or similar reference signs. The drawings are not to scale, and can show exaggerations in order to more clearly show features of the claimed invention.

[0050] In this description expressions of orientation such as top, bottom, vertical etcetera are used for convenience only and refer to the orientation of the foundation pile as seen in the accompanying drawings, especially fig. 1, 3 and 4, the pile being placed vertically in the ground.

[0051] In this description wording like substantially and generally should be understood as meaning that relatively small deviations from the feature or value they refer to are also considered to be covered, for example deviations of 20% or less, such as 15% or less or 10% or less.

[0052] In this description embodiments of an off-shore foundation pile are disclosed, the off-shore foundation pile being provided for supporting for example a platform and / or a wind turbine generator (WTG) supported on the foundation pile, directly or indirectly, preferably free of a transition piece. When performing a method of the disclosure and / or using a system, or parts thereof, according to the disclosure any such platform, WTG or the like, with any transition piece if provided, is preferably removed from the foundation pile beforehand.

[0053] In this description a foundation pile is a pile supported in and / or on the earth, for example by driving or otherwise inserting the foundation pile into a water bedding such as a sea bedding, offshore. The off-shore foundation pile is disclosed in the drawings as a monopile, for example made of metal, but could also be a pile made of different segments, and could be made of different materials, such as but not limited to concrete, or combination of materials, such as but not limited to concrete and metal. The off-shore foundation pile is preferably substantially hollow, at least over most of its height. An off-shore foundation pile can have a circular cross section, seen in top view, perpendicular to a longitudinal axis thereof, as shown by way of example for example in fig. 1 and 7, but could also have a different shape in cross section, for example polygonal, oval or the like, or combinations thereof. An off-shore foundation pile can have a diameter of several meters to more than ten meters, for example up to or above fifteen meters at its lower end, and can have a wall thickness, if made of metal, of centimeters, for example more than 4 centimeters, such as for example 8 to 10 centimeters or more. These sizes are only given by way of example and should not be considered to limit the disclosure. Off shore foundation piles as referred to in this disclosure can have a solid or tubular lower end with a substantially cylindrical or truncated conical shape, preferably substantially free of elements extending outward from said lower end, for ease of driving the pile into the ground. In this description the or an off-shore foundation pile will be referred to as foundation pile.

[0054] Referring to the drawings, the disclosure is directed to a method and system 100 for removing a foundation pile 1 from a use position offshore, in which a lower part 1A of the foundation pile 1 has been driven into a ground 2 below a water level 3, as for example schematically shown in fig. 3, 4,, 11B, 12A - C and 13, such that a longitudinal axis X - X of the foundation pile 1 extends upward, normally vertical. In a method of the disclosure the foundation pile 1 is rotated around said longitudinal axis X - X, prior to and / or during lifting of the foundation pile 1 out of and / or from the ground 2. The foundation pile 1 has an upper end IB extending above the lower part 1A, and as shown in e.g. fig. 3B and fig. 4, fig. 11B, 12A - C and 13 can extend above the water surface 3. Preferably the upper end IB is cut off such that it only marginally extends above the water surface 3 or is cut of below such water surface, such that a vessel 25 can be floated over said upper end IB, as is for example shown schematically in fig. 13.

[0055] A system 100 for use in a method of the disclosure comprises a gripping tool 4. The gripping tool 4 has a gripping piece 5 defining an opening 6 through which the upper part IB of the foundation pile 1 can extend. The gripping tool 4 can take hold of the foundation pile 1, especially a lower part 1A of the foundation pile 1, such that the foundation pile 1 can be rotated around the vertical axis X - X by rotating the gripping tool.

[0056] The gripping tool 4 can take hold of the foundation pile 1 for example by clamping the gripping tool 4 onto an outer surface 7 of the foundation pile 1, for example as schematically shown in fig. 7 or fig. 11A or fig. 11B. The gripping tool 4 to that end can for example function like a wrench or pliers, having two gripper portions pivotably connected to each other and provided with grip enhancing profiles for engaging the surface 7. Alternatively or additionally a gripping tool 4 according to the disclosure can comprise one or more locking elements 23, for example pistons 24 or claws 24, which can be forced into said opening 6 for forcibly engaging said outer surface 7. The locking elements 23 can for example be hydraulically or pneumatically or electrically powered. As schematically shown in fig. 11A and fig. 11B, the locking elements can be or comprise wedges 23A, which can be driven for example in horizontal direction (fig. 11A) and / or in vertical direction (fig. 11B) for locking. The wedges 23A are here shown in pairs, wherein for example one of the wedges of each pair can be fixedly connected to one of the pile 1 and the gripping piece 5, whereas the other wedge of the pair can be movable in a known manner, for example but not limited to hydraulically or pneumatically or electrically (not shown), for wedging the gripping piece 5 into a locked position relative to the pile 1. Additionally or alternatively the gripping tool can engage and take a hold of the foundation pile in a different manner, for example by being welded to the surface 7, or by pistons or claws engaging in openings in the foundation pile 1, which openings can for example be specifically formed for that purpose. In embodiments additionally or alternatively the gripping tool can be forced onto the foundation pile, especially onto a lower part 1A of the foundation pile 1, such that frictional force allows rotation of the foundation pile 1 by rotation of the gripping tool 4, for example by using wedges 23A or the like as described. As shown the gripping tool can be provided with ballast tanks 21 or the like, for increasing weight, at least after placement, in order to increase a holding force and / or maintain the tool in a position close to or at the lower part 1A of the foundation pile, at or close to the ground 2.

[0057] The opening 6 of the gripping piece 5 can have friction increasing elements for engaging the surface 7 and / or elements cutting into the surface 7, such as for example but not limited to teeth 6 A, wedges 23 A, or the like, for improving grip on the surface 7 and hence on the foundation pile 1. Such elements 6A, 23A are by way of example shown in fig. 7 and fig. 11 - 13, and can obviously be used in any suitable configuration in this and the other embodiments.

[0058] In this application gripping should be understood at least as encompassing any way in which the tool can engage a foundation pile 1 such that by rotation of the tool 4 or part of the tool 4 the foundation pile 1 can be rotated around said longitudinal axis X - X.

[0059] Fig. 1 shows an isometric view of a gripping tool 4 mounted on a lower part 1A of a foundation pile 1, especially below a truncated conical upper part IB of the foundation pile 1. The opening 6 of the gripping piece 5 has been slid over the upper part IB of the foundation pile 1, for example by lifting the tool 4 over the top of the foundation pile 1 and lowering it. In alternative embodiments a top end 22 of the pile 1 is removed to such extends that for example a tool 4 and / or a vessel 25 can be floated over the pile 1, such that the tool 4 can be lowered over the pile 1. Two wires 8 are connected to the gripping tool 4, which will be described further.

[0060] In the embodiment of fig. 1 the gripping tool 4 has two wings 9 extending outward from the gripping piece 5. A wire 8 extends from and / or is connected to each of said wings 9, at a position spaced apart from the gripping piece 5. In this disclosure a wire 8 should be understood as any element suitable for exerting a pulling force to the gripping tool 4, such as but not limited to a line, chain, shingle, towing line or the like or a combination thereof. Were reference is made to line this should be understood as meaning that it can also be more than one line. Through the or each line 8 a pulling force F can be exerted to an end 10 of the relevant wing 9 spaced apart from the gripping piece 5 or at least spaced apart from the opening 6 and at least spaced apart from the axis X - X, such that a moment can be exerted on the foundation pile 1 through the gripping tool 4. As will be discussed the lines 8 can be part of a single line.

[0061] As can for example be seen in fig. 2 and figs. 3 and 8 - 10, in a system 100 according to the disclosure the or each line 8 is or are connected to an anchoring system 11. The anchoring system 11 is, during use, spaced apart from the foundation pile 1, for example over a distance L. The anchoring system 11 is anchored at at least one fixed position. In the embodiments shown in fig. 2 and fig. 3 the anchoring system 11 is anchored to a further foundation pile 101 at a distance L of the foundation pile 1 to be removed. Thus pulling forces F can be exerted by the lines 9, which will be borne by the said further foundation pile 101 through the anchoring system 11.

[0062] In fig. 2 and 3 the anchoring system 11 is formed by or comprises a hook-like construction 12, with a slot 13 in which the further foundation pile 101 is received, such that the anchoring construction engages part of the periphery of the further pile 101. The pulling forces F pull the hook-like construction onto the further foundation pile 101. Preferably the hook-like element 12 is held substantially in the same position at the further pile 101, for example by said pulling forces and / or by friction and gravity. By using a slot 13 the hook-like element can be slid around the further pile 101, even when for example a platform, a WTG and / or a transition piece is or are present on said further pile 101. It will be clear that the anchoring system 11 such as said hook-like construction 12 can be connected to the further pile in a different manner, additionally or alternatively, for example by clamping, for example in a manner similar to the gripping tool 4.

[0063] Preferably the or each wire 8 is connected to the anchoring system 11, for example to a hook-like element 12, at a position such that a main direction of a pulling force F exerted in said wire 8 crosses close to or through the further foundation pile 101, if used, such that substantially no torque is transferred to said further foundation pile, when used for anchoring the or each wire 8.

[0064] As can be seen especially in fig. 3B and 4, and also in fig. 11, 12 and 13, the gripping tool 4 and the anchoring system 11 are preferably mounted at a position below the water surface 3, preferably closer to the ground 2 than to the water surface 3, seen in vertical direction. Preferably the gripping tool 4 and the anchoring system 11 are provided close to or at the bottom 2, the gripping tool 4 gripping the foundation pile 1 at the first part 1A, close to the ground. In this way it can be ensured that minimal to no twist will occur in the foundation pile, nor bending. By gripping the foundation pile 1 close to the ground 2, it can be ensured that maximum rotation of the part of the foundation pile extending into the ground 2 is achieved. Moreover, by providing the gripping tool 4 and the anchoring system 11 and thus the wires 8 well below the water surface 3, safety is increased.

[0065] Fig. 4 shows a gripping tool 4 mounted on a foundation pile 1 to be removed, whereas a lifting wire 20A of a crane 20 is connected to an upper end IB of the foundation pile 1. In fig. 4 by way of example a ballast tank 21 is shown in the gripping tool 4, which can be used for pushing the gripping tool 4 down firmly by filling the ballast tank 21, for example using water such as sea water. Whereas when the ballast tank or tanks 21 is or are emptied, the gripping tool 4 can be lifted and displaced more easily, for example by making it float. Similarly the anchoring system 11 can be provided with one or more ballast tanks. As can be seen the wires 8 preferably extend horizontally, the gripping tool 4 and the anchoring system being provided at the same horizontal level.

[0066] Fig. 5 shows an embodiment of a gripping tool 4. The gripping tool 4 has the gripping piece 5 with the opening 6 and wings 9 extending in opposite directions away from the opening 6 to the ends 10. In this embodiment each wire 8, also referred to as first wire 8A and second wire 8B, is connected to a first winch 14A and a second winch 14B respectively, the winches 14 provided in and / or on the gripping tool 4, and is guided around a pully or sheave 15. With the first winch 14A the first wire 8A can be pulled in and given out, whereas with the second winch the second wire 8B can be pulled in and given out.

[0067] As can be seen for example in fig. 5 each of said two sheaves or pullies 15 forms a wire point 16, a first contact point between the wire 8 and the gripping tool 4. Each wire point 16 is designed for transferring the pulling force F to the gripping tool 4 and for guiding the relevant wire 8A, 8B from the relevant winch 14 and / or sheave system 15 away from the relevant wing 9, such that during use the said wires 8A, 8B extend in a first direction Si and second direction S2 respectively. Said first direction Si and second direction S2 preferably enclose an angle B of less than 180 degrees, preferably less than 90 degrees. In the embodiment of e.g. fig. 5 the wires 8 during use extend at a same side of a vertical plane V through the said two wire points 16, during use coinciding with or parallel to the line Pcand the vertical axis X - X. As can be seen in for example fig. 9 and 10, wires 8 can also extend in opposite directions. In fig. 5 the gripping tool 4 is shown in a mid-position, indicated by center line Pc. In fig. 5 the foundation pile 1 is shown in striped lines, inside the opening 6 of the gripping tool 4. The ends 16 of the wires 8A, 8B are connected to the anchoring system 11, such as the hook-like construction 12. Thus by giving out the first line 8A and at the same time pulling in the second line 8B, the gripping tool 4 will be rotated, around the center of the opening 6, which during use will coincide with the axis X - X, in fig. 5 in clock wise direction, for example to a rotated position indicated by the line Pi. On the other hand by giving out the second line 8B and at the same time pulling in the first line 8A, the gripping tool 4 will be rotated, around the center of the opening 6, in fig. 5 in counter-clock wise direction, for example to a rotated position indicated by the line P2. By repeatedly alternately giving out and pulling in the lines 8A, 8B the gripping tool 4 will be reciprocally rotated and, when engaged properly with a foundation pile 1, will reciprocally or intermittingly rotate the foundation pile 1 around the longitudinal axis X - X, for example over an angle a in clockwise and counter-clockwise directions.

[0068] Fig. 5A shows an alternative embodiment, in which the winch 14 is provided on the anchoring device 11, whereas ends of the wires 8A, 8B are attached to wire points 16 at the gripping tool 4. Each wire 8A, 8B can be attached to a separate winch 14, or they can for example be attached to the same winch, as for example shown in fig. 5B, wherein the wires 8A, 8B are wound on the winch such that if the first wire 8A is being given out, the other wire 8B is pulled in and vice versa. In such embodiment the wires 8A and 8B can be part of or formed by a continuous single wire 8 or combination of wires 8.

[0069] Fig. 6 shows a further alternative embodiment of a system 100 of the disclosure, wherein a continuous wire 8 forms the wires, or at least wire segments 8 A and 8B. The wires 8 A, 8B each again have an end attached to the anchoring system 11 such as the hook-like construction 12. In this embodiment the gripping tool 4 comprises a winch 14, here shown, by way of example only, at an extension central to the tool 4 between the wings 9, and behind the opening 6 seen from a side of the wires 8A, 8B and the anchoring system 11. The winch 14 can for example be similar to that as schematically shown in fig. 5B, wherein the wire 8 is wound around a drum 17 of the winch 14. The wire 8 is guided along sheaves or pullies 15 at or near ends 10 of the wings 9. Similar to fig. 5 and 5 A, by rotating the winch drum 17 the wire 8A will be pulled in, whereas the wire 8B will be given out, or vice versa. This will rotate the gripping tool 4 and hence the foundation pile 1 gripped by the gripping tool 4 reciprocally.

[0070] It will be understood that where reference is made to wire 8A and wire 8B these can be parts of, especially segments or ends of a continuous wire 8, wherein giving out or pulling in a wire 8A, 8B should be understood as at least as encompassing increasing the distance between a wire point 16 and the anchoring system 11 or decreasing the distance between a wire point 16 and the anchoring system 11 respectively, such that the gripping tool 4 is rotated.

[0071] Fig. 7 shows an alternative embodiment of a gripping tool 4, similar to that of any one of e.g. fig. 1 - 6, wherein the gripping tool 4 comprises a first tool-part 4A and a second tool part 4B, pivotally connected to the first tool part 4A through a pivot 18. As is shown in fig. 7 by broken lines, the second tool part 4B can be pivoted away from the first tool part 4A, opening the opening 6 such that the gripping tool 4 can be mounted to and / or removed from a foundation pile 1 easily, for example in a substantially horizontal direction, for example using a vessel. The tool parts 4A, 4B can be locked around the foundation pile 1 by a lock 19. Preferably gripping elements 6A such as teeth are provided in the opening 6. Preferably the wire or wires 8 extend from a side of the gripping tool 4 facing away from the side where the pivot 18 is, such that by exerting a pulling force by one of the wires 8, the gripping tool will be pulled more firmly to a closed position, locking the gripping tool firmer onto the foundation pile 1.

[0072] Fig. 8 shows schematically an embodiment of a system 100 of the disclosure, wherein the anchoring system 11 comprises two anchoring constructions 12, like the hook-like constructions 12 as discussed before, each anchored to a separate further foundation pile 101. The wires 8A and 8B are thereby anchored to said separate further foundation piles 101.

[0073] Fig. 9 shows schematically an embodiment of a system 100 of the disclosure, wherein a system 100 of for example any one of fig. 1 - 7 is mirrored, such that an anchoring system 11 is provided on opposite sides of the foundation pile 1. Fig. 10 shows schematically an embodiment of a system 100 of the disclosure, wherein a system 100 of for example fig. 8 is mirrored, such that two anchoring systems 11 are provided on opposite sides of the foundation pile 1. By increasing the number of anchoring points the forces exerted on each anchoring point, such as but not limited to further foundation pile 101, can be reduced and / or the total pulling forces can be increased, whereas pulling directions can be optimized.

[0074] Fig. 11 - 13 disclose alternative embodiments of a system 100 of the disclosure. In these embodiments the gripping tool 4 comprises at least a gripper tool part 26, and a base tool part 27. The base tool part 27 comprises or is connected to an anchoring system 11. The anchoring system 11 is designed for anchoring to the ground 2, preferably spaced apart from the offshore foundation pile 1. The gripper tool part 26 is provided in a gripper piece 5 which is part of or connected to the base tool part 27, wherein the tool 4 comprises or is connected to a drive 28 for rotating the gripper tool part 26 relative to the base tool part 27 and / or the gripper piece 5.

[0075] In fig. 11A and B in top view and side view an embodiment of a system 100 is shown,, comprising a tool 4 lowered over a pile 1, to a position close to or on the ground 2. In this embodiment a tool base part 27 is provided, having two wings 10 extending from a central gripping piece 5, which comprises the gripper tool part 26. The gripper tool part 26 has the opening 6 through which the pile 1 extends. Inside the opening 6 locking elements 23 are provided, here shown, by way of example, as wedges 23A to be wedged between an inner surface 28 of the opening 6 and the outer surface 7 of the pile 1. In fig. 11A the wedges are shown in a position in which they can be brought to engage each other in horizontal direction, in fig. 11B in vertical direction. In embodiments multiple pairs of wedges 23A can be provided, some of which may have a horizontal direction for engagement, and some a vertical direction, in order to lock the tool 4 to the pile both in horizontal, rotational direction and in vertical direction. In embodiments wedges 23A can be provided having different angles for engagement, or all the same.

[0076] The gripper tool part 26 in these embodiments is shown comprising a ring shaped portion 29, extending around the opening 6, which has an outer peripheral surface 30 which is provided with teeth 31, like a sprocket wheel. In fig. 11A only a limited number of teeth 31 is shown. It will be clear that teeth can be provided over a larger part of the circumference, or even the complete circumferential outer surface 30, depending on for example the angle a over which the gripper tool part 26 needs to be rotated. The ring shaped portion 29 is provided in the gripper piece 5, such that the ring shaped portion 29 can rotate within the gripper piece 5 around a virtual axis 32. The axis 32 preferably extends parallel to the longitudinal axis X - X of the pile 1, more preferably coinciding therewith. In or on the base tool part 27 at least one drive 33 is provided, for rotating the gripper tool part 26, especially the ring shaped part 29 thereof around said axis 32. In the embodiments shown the drive 33 comprises at least one sprocket wheel 34, engaging the teeth 31 and designed to be driven by a motor 35, schematically shown in fig. 11 - 13. The motor 35 can for example be an electrical, hydraulic or pneumatic motor. It will be clear that any suitable means can be provided for rotating the gripper tool part 26 relative to the base part 27.

[0077] In these embodiments the anchoring system 11 comprises vacuum cups 36 extending from the wings 10 of the base tool part 27. Vacuum cups 36 as such are known in off-shore applications for securing objects. In this embodiment two such sups 36 are shown. It will be clear that any suitable number can be used, for example more than two, such as for example 3 or 4 or more. Suction cups are also known as suction anchors or suction caissons or similar wording. The cups 36 have an open lower end 37 with which they initially rest on the ground 2, as schematically shown in fig. 11B en 12A. In the embodiments shown the tool 4 is provided with at least a vacuum pump 38 for providing sub-atmospheric pressure inside the cups 36, such that the cups 36 are forced into the ground 2, as schematically shown in fig. 12B. In such position the cups 36 anchor the tool 4 to the ground, preventing the tool, especially the tool base part 27 from rotating around the axis X - X.

[0078] It will be clear that the base tool part 27 can also be anchored to the ground 2 in a different manner, additionally or alternatively, for example by using drill anchors, spuds, or similar anchoring means to be driven into the ground. Alternatively or additionally the tool 4 can be anchored by using for example box anchors or wire anchors or the like, which can for example be used in a manner similar to fig. 8 - 10, wherein the wires 8 can be anchored to the ground by anchors known in the art.

[0079] Fig. 12A - C schematically show three phases of a method according to the disclosure, using a system 100 as shown in fig. 11A and / or fig. 11B. In fig. 12A the tool 4 is shown, having been lowered over a pile 1, the cups 36 resting on the ground 2. The pile 1 has not yet been gripped by the gripper tool part 26. In this position a sub-atmospheric pressure, also referred to as a vacuum, is created in the cups 36, such that the vacuum cups 36 are pulled into the ground, lowering the tool base part 27 closer to the ground 2, as shown in fig. 12B. In this position the gripping tool part 26 can be operated in order to firmly grip the pile 1, as previously described. To this end for example the wedges 23A can be wedged firmly between the inner wall 28 of the opening 6 and the outer surface 7 of the pile 1.

[0080] When brought into the position of fig. 12B the tool gripper part 26 can be rotated relative to the gripper base part 27, continuously in one direction (clockwise or counter clockwise) or reciprocally (alternatingly in clockwise and counterclockwise directions) around the axis X - X.

[0081] In advantageous embodiments the system 100 further comprises at least one pusher, for pushing at least part of the tool base part 27 with the tool gripper part 26 upward, away from the ground 2, while firmly gripping the pile 1. Thus the tool 4 can aid in pulling the pile 1 out of the ground 2. In embodiments the or each pusher 39 can be provided by the vacuum cups 36. By introducing, in the position as shown in fig. 12B, air or water or another fluid under pressure into the vacuum cups 363, the inner volume of the cups 36 will again expand, pushing the tool base part 27 of the tool 4 upward. Additionally or alternatively other pushers 39 can be provided, such as for example on or more jacks 40 as schematically shown in fig. 12C.

[0082] Fig. 13 shows schematically a system 100 similar to that as for example disclosed in fig. 11 and 12, with a vessel 25 floated over the pile 1. In this embodiment the tool 4 is connected to the vessel 25 by wires 41, connected to winches 42, preferably constant tension or constant force winches 42. In fig. 13 the suction cups 36 or elements of the anchoring system 11 have been brought to rest on the ground 2. The anchoring system 11 can then be operated in order to anchor the tool base part 27 into the ground 2, for example by suction cups 36 as disclosed in fig. 12B. Then, after gripping the pile 1 as described, the pile 1 can be rotated around the axis X - X, while tension is provided on the wires 41 by the winches 42. Thus during rotation of the pile 1 the tool 4 or at least the tool gripper part 25 can be pulled up by the wires 41, pulling the pile 1 out of the ground 2. If constant tension winches 42 or constant force winches 42 are used, a constant tension and / or force can be provided in the wires 41, preventing largely that the pile 1 will suddenly shoot out of the ground 2 uncontrollably. In embodiments of a method of the disclosure, after pulling the tool with the pile 1 upward over a predetermined distance, the tool 4, especially the tool gripper portion 26 can be repositioned relative to the pile 1, especially be lowered along the pile 1, preparing for a next step in pulling the pile 1 further out of the ground 2. Instead of, or in addition to, pulling the tool base part 27 upward, the system can be designed to pull the tool gripper part 26 upward relative to the tool base part 27, for pulling the pile 1 from the ground 2, for example step wise.

[0083] In the embodiment of fig. 13 the pile 1 can be pulled upward, along the axis X - X, for example hanging from the wires 41. In embodiments additional to or alternative to the wires 41 being connected to the tool base part, a further gripping tool can be connected to the pile 1, above the tool 4, wherein the wires 41 are connected to said further gripping tool, such that the pile 1 can be pulled upward relative to the tool 4.

[0084] It will be appreciated that a vessel 25 as schematically disclosed in fig. 13 can also be used with embodiments according to fig. 1 - 12, for providing at least part of the lifting force needed for lifting the pile 1 out of the ground 2. This can increase safety and reduce cost for not needing a floating crane or at least having to have a smaller load on such crane, reducing the risk of for example capsizing of such crane.

[0085] In embodiments according to fig. 11 - 13 again ballast tanks 21 can be provided, for example in wings 10. Instead of or in addition to ballast tanks, floating tanks can be provided for making the tool 4 or parts thereof float on or in water.

[0086] In a method of the disclosure a foundation pile 1 can be removed from a use position in which a lower part 1A of the foundation pile 1 has been driven into a ground 2, such that a longitudinal axis X - X of the foundation pile 1 extends upward, for example using a system 100 as discussed. In such method the foundation pile 1 is rotated around said longitudinal axis X - X, prior to and / or during lifting of the foundation pile 1 out of and / or from the ground 2, for example by using a floating crane 20 as shown in fig. 4 and / or a vessel 25 as schematically shown in fig. 13, providing a lifting force. The foundation pile 1 is preferably rotated intermittently in a first direction and in an opposite second direction around the longitudinal axis X - X. However, the foundation pile could be rotated continuously in a single direction, for example by providing a ratchet mechanism in the gripping tool 4.

[0087] It has been found that by rotating the foundation pile 1 in the ground, preferably reciprocally, prior to and / or during at least part of the lifting of the pile out of the ground 2, the lower part 1A of the foundation pile 1 releases more easily from the ground, in a more evenly manner. Peak lifting forces to be exerted upward on the foundation pile 1 can be reduced compared to lifting without said rotation, whereas it can be ensured that the foundation pile will release from the ground in a more evenly fashion.

[0088] In a method of the disclosure preferably the foundation pile is rotated around said longitudinal axis X - X reciprocally clockwise and anticlockwise, preferably over an angle of less than 120 degrees between extreme positions, i.e. between lines Pi and P2 in fig. 2 - 11, such as for example less than 90 degrees. In advantageous embodiments the foundation pile is rotated over an angle of less than 60 degrees, such as for example 40 degrees. In embodiments the angle a over which the foundation pile 1 is rotated can be changed during lifting, for example increased from a relatively small angle to a larger angle when holding forces, such as frictional forces between the lower part 1A of the foundation pile 1 and the ground 2 have been reduced by rotation of the foundation pile 1.

[0089] Preferably at least any structure supported by or on the foundation pile, such as a tower, WTG, platform or the like is removed prior to rotation of the foundation pile, especially prior to positioning of the gripping tool 4. In embodiments of a method of the disclosure a top end portion 22 of the foundation pile 1 is removed prior to rotation of the foundation pile, especially prior to positioning of the gripping tool 4, for example to above or, preferably, below the water level 3.

[0090] Advantageously the foundation pile 1 is gripped using a gripping tool 4 which has at least one of a wrench like gripping profile and a wrench like closure mechanism, as for example schematically shown in fig. 7 or 11.

[0091] In the embodiments disclosed, the foundation pile 1 is shown as an off-shore foundation pile. Preferably the foundation pile 1 is gripped for rotation below a water level 3 surrounding the foundation pile 1. Preferably the foundation pile 1 is gripped close to the ground, whereas the anchoring system 11 is preferably provided at substantially the same level as the gripping tool 4, such that in embodiments using one or more wires 8, the wire or wires 8 extend(s) substantially horizontally during pulling, or directly in the ground.

[0092] The invention is by no means limited to the embodiments disclosed herein by way of example only. Many amendments can be made within the concept of the disclosure, including combinations of some or all of the features of the methods and structures as disclosed.

[0093] For example, in the drawings in the embodiments of figs. 1 - 10 the or each anchoring system is disclosed as a hook-like element, connected to a further foundation pile. It will be clear that such system can have any suitable configuration. For example an anchoring system can be a traditional anchor at the ground 2, or a vessel, such as a tow tug, of combinations thereof. In stead of a hook-like construction an anchoring system or provision can be designed differently, for example for clamping onto a further foundation pile, or for mounting in a different way, for example but not limited to bolting or welding the anchoring construction or part thereof to a further foundation pile. In the embodiments shown the gripping tool has two wings, extending in opposite directions from a center piece. A gripping tool can however also have a different configuration, for example with three or four wings, and can for example be substantially circular or oval. A gripping tool can be provided with a ratchet mechanism, such that the foundation pile can be rotated over larger angels, for example 180 degrees or more, such as for example up to or above 360 degrees.

Claims

Claims1. Method for removing an off-shore foundation pile from a use position in which a lower part of the off-shore foundation pile has been driven into a ground, such that a longitudinal axis of the off-shore foundation pile extends upward, wherein the off-shore foundation pile is rotated around said longitudinal axis, prior to and / or during lifting of the off-shore foundation pile from the ground.

2. Method according to claim 1, wherein the off-shore foundation pile is rotated intermittently in a first direction and in an opposite second direction around the longitudinal axis.

3. Method according to claim 1 or 2, wherein a tool is mounted onto the off-shore foundation pile, said tool gripping an outer periphery of the offshore foundation pile, wherein the off-shore foundation pile is rotated by rotating at least part of said tool while gripping the off-shore foundation pile.

4. Method according to claim 3, wherein the tool comprises a gripping piece for grippingly engaging said outer periphery and wherein the tool has at least one wing extending outward from said gripping piece, wherein during use at least periodically a force is exerted on said at least one wing for providing a moment relative to the longitudinal axis, for rotating said off-shore foundation pile.

5. Method according to claim 4, wherein the tool comprises at least two wings, extending in oppositely outward directions, wherein at each wing intermittently at least a pulling force is exerted in a first direction, to a same side of the off-shore foundation pile.

6. Method according to any one of claims 3 - 5, wherein at least one, preferably at least two lines are attached to the tool for applying pulling forces to the tool.

7. Method according to claim 6, wherein the at least one line is, at a position spaced apart from the tool, connected to an anchoring provision.

8. Method according to claim 6 or 7, wherein at least one of the tool and the anchoring provision comprises at least one of a winch and a sheave system with which said at least one hne is given out and taken in.

9. Method according to claim 7 or claim 8 dependent on claim 7, wherein the anchoring provision is connected to a further off-shore foundation pile driven into said ground, distanced from said off-shore foundation pile engaged by the tool.

10. Method according to claim 3, wherein the outer periphery is gripped by a gripper tool part of the tool, which gripper tool part is rotated relative to a base tool part which is anchored to said ground, adjacent a lower part of the off-shore foundation pile.

11. Method according to claim 10, wherein the tool is anchored to the ground by at least suction.

12. Method according to claim 10 or 11, wherein the tool is anchored to the ground by at least anchors driven into the ground.

13. Method according to any one of the claims 3 - 12, wherein the tool is lowered over an upper end of the off-shore foundation pile, preferably after removal of a top portion of the off-shore foundation pile and / or a transition piece and / or a platform, wherein the off-shore foundation pile is gripped by said tool, preferably near a lower end of said off-shore foundation pile.

14. Method according to any one of claims 3 - 13, wherein the tool comprises at least one ballast tank for increasing and decreasing a weight of said tool.

15. Method according to any one of the preceding claims, wherein during at least part of the time the off-shore foundation pile is rotated a lifting force is applied to the off-shore foundation pile too.

16. Method according to claim 15, wherein the lifting force is at least partly provided by lines pulling at the tool and / or the off-shore foundation pile in a direction substantially parallel to a longitudinal axis of the offshore foundation pile, which lines are given out and taken in using at least one constant tension winch.

17. Method according to claim 15 or 16, where in the lifting force is at least partly provided by the tool pushing against the ground.

18. Method according to any one of the preceding claims, wherein the off-shore foundation pile is rotated around said longitudinal axis reciprocally clockwise and anti-clockwise, preferably over an angle of less than 120 degrees, such as for example less than 90 degrees, more preferably less than 60 degrees, such as for example 40 degrees.

19. Method according to any one of the previous claims, wherein the off-shore foundation pile is gripped using a tool which has at least one of a wrench like gripping profile and a wrench like closure mechanism.

20. Method according to any one of the preceding claims, wherein the off-shore foundation pile is gripped using a tool comprising wedge shaped elements for gripping, especially clamping the off-shore foundation pile.

21. Method according to any one of the preceding claims, wherein the off-shore foundation pile is gripped for rotation below a water level surrounding the off-shore foundation pile, especially near the ground into which the off-shore foundation pile is founded.

22. Method according to any one of the preceding claims, wherein a vessel is floated directly above and / or around an upper end of the off-shore foundation pile to be removed, wherein the vessel provides a pulling force in upward direction to the off-shore foundation pile, preferably through wires pulled by winches, especially constant force winches.

23. System for use during removal of an off-shore foundation pile from a ground, the system comprising at least:a gripping tool, comprising a gripping piece defining an opening through which an off-shore foundation pile can extend, the gripping piece being designed for gripping a surface portion of the off-shore foundation pile; at least one anchoring system for anchoring the gripping tool at a location spaced apart from the foundation pile.

24. System according to claim 23, wherein the system further comprises: at least one wire, preferably at least two wires, connected to or connectable to the gripping tool, spaced apart from a center of said opening, preferably spaced apart from said opening, and the anchoring system is for anchoring said at least one wire spaced apart from an off-shore foundation pile to be removed.

25. System according to claim 24, wherein the gripping tool comprises said gripping piece and at least two wings extending outward from said gripping piece, wherein one said at least one wire extends from and / or is connected to each of said wings, spaced apart from the gripping piece.

26. System according to claim 24 or 25, wherein at least one of the gripping tool and the anchoring system comprises at least one of a winch and a sheaving system.

27. System according to any one of claims 24 - 26, wherein the anchoring system is designed for mounting the anchoring system on an offshore foundation pile, especially for hooking around a periphery of such offshore foundation pile.

28. System according to claim 23, wherein the gripping tool comprises a gripper tool part and a base tool part, wherein the base tool part comprises or is connected to the anchoring system, wherein the anchoring system is designed for anchoring to the ground, spaced apart from the off-shore foundation pile, and wherein the gripper tool part is provided in a gripper piece which is part of or connected to the tool base part, wherein the toolcomprises or is connected to a drive for rotating the gripper tool part relative to the base tool part and / or the gripper piece.

29. System according to claim 28, wherein the gripping tool and / or the anchoring system comprises at least one pusher for pushing the foundation pile upward, away from said ground.

30. System according to claim 28 or 29, wherein the anchoring system comprises vacuum cups for anchoring to the ground.

31. Gripping tool, especially for use in a method according to any one of claims 1 - 22 or for forming a system according to any one of claims 23 - 30, wherein the gripping tool comprises at least a gripping piece defining an opening through which an off-shore foundation pile can extend, and at least two wing elements, extending outward, away from the opening32. Gripping tool according to claim 31, wherein each wing comprises at least one wire point from which a wire extends, said wire point being spaced apart from the opening.

33. Gripping tool according to claim 32, wherein each of said two wire points is designed for guiding a wire from a winch and / or sheave system away from the relevant wing, such that during use the said wires extend in a first direction and second direction respectively, said first direction and second direction enclosing an angle of less than 180 degrees, preferably less than 90 degrees and the wires during use extend at a same side of a vertical plane through the said two wire points.

34. Gripping tool according to claim 31, wherein at least one of said wings, preferably at least to wings comprise an anchoring portion, especially a suction cup, for anchoring to ground, especially a sea bed.

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