NL2007257C2

NL2007257C2 - Method for installation of an off-shore mast or pile.

Info

Publication number: NL2007257C2
Application number: NL2007257A
Authority: NL
Inventors: Sebastiaan Gijsbertus Bemmelen
Original assignee: Bos & Kalis Baggermaatsch
Priority date: 2011-08-11
Filing date: 2011-08-11
Publication date: 2013-02-12
Also published as: WO2013022338A1

Description

NLP189744

Method for installation of an off-shore mast or pile BACKGROUND

The invention relates to a method for installation of an off-shore mast or pile.

5 An off-shore wind mill of the monopile-type comprises one straight mast or pile having a lower end that is embedded into the bottom. Around the pile an armour comprising stones or rocks is dumped onto the bottom to prevent scour around the mast. Such scour would weaken the 10 stability of the bottom around the mast.

In a known installation method the pile is driven into the bottom, whereafter a dumping vessel maneuvers around the pile to dump the armour. As the dumping vessel has be brought close to the installed pile, the maneuvering 15 of the vessel is a rather complex task, especially when the armour is build of multiple layers. In that case the subsequent layers have to be dumped quickly after each other around the pile to prevent that the first layer is already been scoured out before a final cover layer is dumped.

20 It is an object of the present invention to provide an alternative method for installation of an offshore mast or pile.

2

SUMMARY OF THE INVENTION

According to a first aspect, the invention provides a method for installation of an off-shore vertical 5 mast or pile in the bottom under water and the foundation thereof under water, wherein the lower portion of the pile extends into the bottom and the foundation comprises an armour on the bottom that surrounds the pile, which armour comprises a layer of stones or rocks, wherein the method 10 comprises the steps of placing a spacer on the bottom, which spacer comprises a circumferential wall standing upright from the bottom to define a vertically extending insertion channel for the pile, dumping the armour around the spacer, and inserting the lower portion of the pile into the bottom 15 via the insertion channel after dumping the armour.

According to the method of the invention, the spacer keeps an insertion channel free for the pile within the armour that is dumped. The armour is dumped without a dumping vessel being hampered by the presence of a pile. 20 Moreover, as the pile is not present yet, the dumped material is hardly scoured during dumping. The method according to the invention can be carried out from different or dedicated vessels, even from different contractors. The bottom is then prepared by placing the spacer and dumping 25 the armour. The pile can be inserted from another vessel or the same vessel, even days later when multiple piles of a row are inserted.

In an embodiment the spacer is left behind on the bottom after insertion of the pile into the bottom. The 30 spacer is then regarded a lost spacer, whereby for each further pile a new spacer is necessary.

In an embodiment the insertion channel of the spacer is covered by a removable cap during dumping of the armour, whereby it is prevented that rocks or stones are 35 dumped into the insertion channel.

In an embodiment thereof the cap is removed from the spacer before inserting the lower portion of the pile 3 into the bottom via the insertion channel.

In an efficient embodiment thereof the same cap is used for multiple spacers that are left behind on the bottom after insertion of the pile into the bottom.

5 In an embodiment the armour comprises a filter layer with grains on the bottom and a cover layer with stones or rocks that covers the filter layer, which stones or rocks have a diameter that is at least twice the diameter of the grains, wherein the method comprises dumping the 10 filter layer and subsequently dumping the cover layer.

In an practical embodiment the stones or rocks of the cover layer have a diameter of at least 0,40 meter.

In an embodiment thereof the cover layer is dumped immediately after dumping the filter layer, whereby the 15 vulnerable filter layer is exposed to currents in the water for only a limited time period.

In an embodiment the spacer is placed and/or the armour is dumped from a first vessel, and the pile is inserted into the bottom from another, second vessel.

20 In an embodiment the mast or pile forms part of an off-shore wind mill to be installed, wherein the wind mill comprises one vertical mast or pile and a gondola on top of the pile.

According to a second aspect, the invention 25 provides an assembly of a spacer and a cap for the spacer for off-shore installation of a vertical mast or pile of a windmill, wherein the spacer comprises a circumferential wall that defines a vertically extending insertion channel for the pile, and wherein the cap comprises an insert part 30 that is accommodated in the insertion channel and an upwardly tapering head that is connected to the insert part.

In an embodiment thereof the spacer comprises a hopper shaped catcher along the upper edge of the circumferential wall, which facilitates the insertion of the 35 lower end of the pile into the insertion channel from a vessel.

In an embodiment thereof the cap comprises an 4 abutment wall along the lower side of the head that abuts and covers the catcher, whereby it is prevented that the catcher is hit or buried by the stones or rocks that are dumped.

5 In an embodiment the spacer comprises anchor plates that extend radially outwards from the lower edge of the circumferential wall. The anchor plates are embedded under the armour to secure the spacer. The cap can be released from the secured spacer by means of a hoisting 10 device.

In an embodiment the spacer and the cap are made of steel or steel plate.

The various aspects and features described and shown in the specification can be applied, individually, 15 wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications .

20

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in 25 which:

Figure 1 schematically shows an off-shore wind farm under construction; and

Figures 2-6 show the subsequent steps during installation of the mast of the wind mills into the sea 30 bottom by means of a spacer according to the invention;

DETAILED DESCRIPTION OF THE INVENTION

35 Figure 1 schematically shows an off-shore wind farm at sea under construction. The wind farm is constructed by means of a vessel 30. The vessel 30 comprises a floating 5 hull 31, a crane 32 with a hoist cable 33 extending from the hull 31, and a grain dumping device 35 and a rock dumping device 36 that are lowered downwards from the hull 31 for locally dumping grains and rocks onto the sea bottom 10 in a 5 controlled manner.

The wind farm comprises a row of multiple identical wind mills 50, 51, 52 of the monopile type. The wind mills 50, 51, 52 each comprise one straight mast or pile 54 having a lower end 55 that is embedded into the sea 10 bottom 10. The pile 54 vertically extends though and above the seawater 20. Above the pile 4 the wind mills 50, 51, 52 comprise a gondola 53 having blades to generate electrical power in a manner that is known per se.

On the sea bottom 10 an armour 60 has been 15 provided around each of the piles 54 to protect the sea bottom 10 around the lower end 54 against scour that would occur by currents in the sea water 20. The armour 60 comprises a filter layer of fine grains 61 and a cover layer of stones or rocks 62. The construction of the armour 60 is 20 described in more detail hereafter.

Figure 2 shows a spacer 70 to be installed onto the sea bottom 10. The spacer 70 is made of steel plate and comprises a first straight cylindrical circumferential wall 71 that is dimensioned to receive and pass the lower end of 25 a pile 54, multiple anchor plates 72 radially extending from the lower edge of the first circumferential wall 71, and a hopper shaped catcher 73 along the upper edge of the first circumferential wall 71.

The spacer 70 can be temporally closed off by 30 means of a cap 80. The cap 80 is made of steel plate and comprises a second circumferential wall 81 that fits inside the first circumferential wall 71, a sidewardly extending abutment wall 82 along the upper edge of the second circumferential wall 81 that loosely fits into the catcher 35 73, and a conically shaped head 83 having its base connected to the abutment wall 82. The abutment wall 82 and the base of the head 83 are provided with ventilation holes 85. At 6 the upper side the head 83 comprises an ventilation hole 8 6 and a lifting eye 84.

The installation of the pile 54 of one of the wind mills 50, 51, 52 as shown in figure 1 is described hereafter 5 in more detail with reference to figures 2-6.

As shown in figure 2, the vessel 30 has placed a spacer 70 onto the sea bottom 10 at the place where the pile 54 will be driven into the sea bottom 10. The anchor plates 72 rest on the sea bottom 10 and keep the first 10 circumferential wall 71 above the sea bottom 10. The cap 80 is inserted into the spacer 70, wherein the abutment wall 82 is positioned inside the catcher 73. The lowering of the spacer 7 0 and the cap 80 can be combined by inserting and temporarily fixing the cap 80 into the spacer 70 on the deck 15 of the vessel 30 prior to lowering this assembly towards the sea bottom 10. The hoist cable 33 can be temporary released from the hoisting eye 8 6 or stay attached to the hoisting eye 86 during the further installation steps.

As shown in figure 3, the filter layer 61 is 20 formed by dumping a layer of grains around the spacer 70 onto the sea bottom 10 by means of the grain dumping device 35 of the vessel 30. The height of the filter layer 61 is about half the height of the first circumferential wall 71.

As shown in figure 4, the cover layer 62 is formed 25 by dumping a layer of rocks around the spacer 70 by means of the rock dumping device 36 of the vessel 30. The cover layer 62 fully covers the filter layer 61. The armour 60 substantially reaches the height of the upper edge of the catcher 73. This dumping of the rocks is performed 30 immediately after the dumping of the grains.

Subsequently, as shown in figure 5, the cap 80 is raised from the sea bottom 10 in direction A by means of the hoist cable 33, leaving the spacer 70 permanently behind on the sea bottom 10. The spacer 70 is kept on its position by 35 the anchor plates 72 that are embedded under the armour 60. As shown in figure 6, the cap 80 is subsequently removed, whereafter the lower end 54 of the pile 51 is inserted in 7 direction B into the insertion channel that is formed by the catcher 73 and the first circumferential wall 71. After insertion the pile 51 is driven into the sea bottom 10 in direction B in a manner known per se. The cap 80 is used 5 again for the next pile 51.

The cap 80 can be removed directly after the dumping of the armour 60, whereby the spacer 70 is ready to receive the pile 54. The pile 54 can then be installed immediately after removal of the cap 80 or some days later, 10 for example together with other piles 54 in the same row. Alternatively the cap 80 remains installed on the spacer 70 until short before the insertion of the pile 54, which has the advantage that it is ensured that insertion channel of the spacer 70 is kept free from obstacles.

15 The installation of the spacer 70 and the dumping of the armour 60 can be carried out by the vessel 30 as shown. The insertion of the pile or piles 54 can be carried out by the same vessel 30 or by a different, second vessel that is equipped for drilling piles. The second vessel can 20 be from a different contractor than the first vessel 30. The installation of the spacers 70 and the dumping of the armour 60 can be carried out by dedicated vessels as well.

It is to be understood that the above description is included to illustrate the operation of the preferred 25 embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the spirit and scope of the present invention.

Claims

1. Method for the installation of an offshore vertical mast or pole in the bottom under water and the foundation thereof under water, wherein the lower part of the pole extends into the bottom and the foundation comprises a protection on the bottom that the pole surrounds, which protection comprises a layer of stones or rocks, the method comprising the steps of placing a spacer on the bottom, which spacer comprises a circumferential wall that rises from the bottom to form a vertically extending insert channel for the pole, pouring the protection around the spacer and introducing the lower part of the pole through the insert channel after pouring the protection.

2. Method as claimed in claim 1, wherein the spacer holder remains on the bottom after the pile has been brought into the bottom.

3. Method as claimed in claim 1 or 2, wherein the insertion channel of the spacer is covered with a removable cap during pouring.

4. Method as claimed in claim 3, wherein the cap is removed from the spacer prior to bringing the pole into the bottom via the insert channel.

5. Method as claimed in claim 4, wherein the same cap is used for several spacers 25 that remain after the pile has been brought into the bottom.

6. Method as claimed in any of the foregoing claims, wherein the protection comprises a filter layer with gravel or ground grains on the bottom and a cover layer with stones or boulders covering the filter layer, which stones or boulders have a diameter which is at least twice the diameter of the is gravel or milled grains, the method comprising pouring the filter layer and then pouring the cover layer.

Method according to claim 6, wherein the stones or boulders of the cover layer have a diameter of at least 0.40 meters.

8. Method as claimed in claim 6 or 7, wherein the cover layer is poured immediately after pouring of the filter layer.

9. Method as claimed in any of the foregoing claims, wherein the spacer is placed and / or the protection is poured from a first ship, and wherein the pole is brought into the bottom from another, second ship.

10. Method as claimed in any of the foregoing claims, wherein the mast or pole forms a part of an off-shore windmill to be installed, wherein the windmill comprises one vertical mast or pole and a gondola on the top side of the pole.

11. Assembly of a spacer holder and a cap for the spacer for offshore installation of a vertical mast or pole, the spacer comprising a circumferential wall forming a vertically extending insert channel for the pole, and wherein the cap an insert part comprises opening in the insert channel and an upwardly tapered head connected to the insert.

12. Assembly as claimed in claim 11, wherein the spacer comprises a funnel-shaped catcher along the upper edge of the circumferential wall.

An assembly according to claim 12, wherein the cap comprises a stop wall along the underside of the head that abuts and covers the catcher.

Assembly as claimed in any of the claims 11-13, wherein the spacer comprises anchor plates which extend radially outwards from the lower edge of the circumferential wall.

15. Assembly as claimed in any of the claims 11-14, 35, wherein the spacer and the cap are made of steel or steel plate. o-o-o-o-o-o-o-