WO2015129053A1

WO2015129053A1 - Pile protection

Info

Publication number: WO2015129053A1
Application number: PCT/JP2014/055881
Authority: WO
Inventors: Takahito Ohkubo; Yukihiro SHINOMURA; Nobuyoshi Oike; Takahiko NAGAO; Kotaro Oda; Shigeru Matsuo
Original assignee: Kyowa Co., Ltd.; Sumitomo Corporation
Priority date: 2014-02-26
Filing date: 2014-02-26
Publication date: 2015-09-03

Abstract

This invention provides a scour protection method for a monopile type of foundation of an offshore wind generation facility to prevent scour from occurring. The scour protection method for the foundation of the offshore wind generation facility includes the steps of locating a site at which a monopile is to be installed, placing a plurality of bag members around the monopile installation site, and driving the monopile into the monopile installation site.

Description

DESCRIPTION

Title of Invention

SCOUR PROTECTION METHOD FOR FOUNDATION OF OFFSHORE WIND GENERATION FACILITY

Technical Field

[0001]

This invention relates to scour protection methods for foundations of offshore wind generation facilities, and more particularly to a scour protection method for a monopile type of foundation of an offshore wind generation facility. Background Art

[0002]

Conventionally, wind power generation facilities have been built in the ocean. For offshore wind power generation facilities, monopiles can be used because of their simple structure and less problematic design and construction. Such offshore wind generation facilities using the monopiles are disclosed, for example, in FIG. 8 and FIG. 10 in "Yojo fuuryoku hatsuden gijutu no genjo to shourai tenbou (The current state and future perspective of offshore wind power generation technology)" (Japan Society of Civil Engineers (JSCE), 2010 JSCE Annual Meeting Research symposium, Ken-08 material).

Citation List

Patent Literature

[0003]

[Non-Patent Literature l] Yojo fuuryoku hatsuden gijutu no genjo to shourai tenbou (The current state and future perspective of offshore wind power generation technology)" (Japan Society of Civil Engineers (JSCE), 2010 JSCE Annual Meeting Research symposium, Ken-08 material)

Summary of Invention Technical Problem

[0004]

To build a conventional offshore wind generation facility using a monopile, firstly the monopile is driven in at a predetermined location on the seabed and a wind power generation facility is mounted on the monopile. In this case, a plurality of bag-shaped scour-protection filter units are installed around the driven monopile to prevent scour from occurring.

[0005]

However, the monopile thus driven in under the sea causes a turbulent flow of ocean current, resulting in the occurrence of scour from a local flow. Solution to Problem

[0006]

This invention has been made in view of the aforementioned problem and has an object to provide a scour protection method that can prevent scour at the foundation of an offshore wind generation facility in a construction method of building the offshore wind generation facility using a monopile.

[0007]

The scour protection method for the foundation of an offshore wind generation facility according to the invention includes the steps of locating a site at which a monopile is to be installed, placing a plurality of bag members around the monopile installation site, and driving the monopile into the monopile installation site.

[0008]

Preferably, the step of placing the plurality of bag members around the monopile installation site includes a step of arranging the plurality of bag members into a ring shape whose inner circumference circumscribes the monopile installation site and has a predetermined diameter. The diameter of the inner circumference along which the bag members are arranged is greater than the outer diameter of the monopile to be installed.

[0009]

The step of placing the plurality of bag members around the monopile installation site may include a step of arranging the bag members so as to enclose the monopile in multiple horizontal tiers.

[0010]

The step of placing the plurality of bag members around the monopile installation site may include a step of stacking the bag members on top of each other.

[0011]

A scour protection method for the foundation of an offshore wind generation facility according to an embodiment of the present invention further includes a step of preparing a bag-member installation jig capable of hanging a plurality of bag members all at once. The step of placing the bag members around the monopile installation site includes a step of installing the bag members by using the prepared bag-member installation jig.

Advantageous Effects of Invention

[0012]

According to the scour protection method for the foundation of an offshore wind generation facility of the invention, a plurality of bag members are installed in advance around a site at which a monopile is to be installed and then the monopile is driven into the site, thereby preventing scour.

[0013]

In addition, since the bag members are installed in advance in a location where there are no obstacles, the installation of the bag members is easy.

Brief Description of Drawings

[0014]

FIGS. 1A and IB illustrate steps of a scour protection method for the foundation of an offshore wind generation facility according to an embodiment of the invention;

FIGS. 2A and 2B illustrate steps of the scour protection method for the foundation of the offshore wind generation facility;

FIGS. 3A and 3B illustrate steps of the scour protection method for the foundation of the offshore wind generation facility according to another embodiment;

FIGS. 4A and 4B illustrate steps of the scour protection method for the foundation of the offshore wind generation facility according to yet another embodiment;

FIGS. 5A and 5B illustrate steps of the scour protection method for the foundation of the offshore wind generation facility according to yet another embodiment;

FIGS. 6A and 6B are front views of a jig that hangs a plurality of bag members;

FIGS. 7A, 7B and 7C illustrate patterns of hanging the bag members by the jig;

FIGS. 8A and 8B illustrate other patterns of hanging the bag members by the jig;

FIGS. 9A, 9B and 9C illustrate steps of a scour protection method according to yet another embodiment, the method involving stacking the bag members on top of each other;

FIGS. 10A, 10B and IOC illustrate foundations around which the bag members can be installed according to the embodiments; and

FIGS. 11A and 11B illustrate a scour protection method involving stacking the bag members on top of each other according to yet another embodiment.

Description of Embodiments

[0015] With reference to the drawings, embodiments of the present invention will be described below.

[0016]

FIGS. 1A to 2B illustrate steps of a scour protection method for a foundation of an offshore wind generation facility according to an embodiment of the present invention. FIGS. 1A and 2A are plan views, and FIGS. IB and 2B are cross -sectional views taken along arrows IB-IB and IIB-IIB in FIGS. 1A and 2A, respectively.

[0017]

Referring to FIGS. 1A to 2B, the offshore wind generation facility in the embodiment of the invention uses a monopile as its foundation. Firstly, as shown in FIGS. 1A and IB, a site 11 at which a monopile is to be installed is located on the seabed 30. Since the monopile used herein is cylindrical, an almost circular installation site 11 is located. Secondly, bag-shaped filter units (hereinafter, referred to as "bag members") 21 are arranged in a rig shape or in multiple horizontal tiers so as to enclose the installation site 11. Therefore, the ring shape formed by the plurality of bag members 21 placed has an outer circumference that is also roughly circular.

[0018]

The bag members are made by filling bag-shaped nets of woven synthetic fiber with predetermined block objects and their shape is changed into a cone when they are hung. Subsequently, a plurality of bag members are arranged so as to enclose the firstly placed bag members. The arranged bag members are shown in FIGS. 1A and IB.

[0019]

Next, a monopile 12 is driven into the monopile installation site 11. This state is shown in FIGS. 2A and 2B. As shown in FIG. 2A, the monopile 12 is driven in so that the monopile 12 is concentric with the installation site 11. Specifically, as shown in FIG. 2A, a plurality of bag members are arranged into a ring shape that has an inner circumference with a predetermined diameter. It is preferable that the predetermined diameter of the inner circumference along which the bag members are arranged matches the outer diameter of the monopile to be installed. More specifically, it is preferable to determine the diameter of the installation site 11 in advance so that the bag members abut against the outer circumference of the monopile 12. In this embodiment, the bag members arranged at spacings abut against the monopile 12 (FIG. 2A). The number and spacing of the bag members abutting against the monopile 12 can be selected from any desired values. The cross -sectional view of FIG. 2B shows that the bag members appropriately abut on the outer circumference of the monopile 12.

[0020]

Description will be made about some states in which the plurality of bag members abuts against the monopile 12. FIGS. 3A and 3B illustrate a monopile 12 driven in so as to abut against parts of the bag members as shown in FIG. 2A and are cross-sectional views as with FIG. 2B. In this case, with reference to FIGS. 3A and 3B, the bag members 21a are destroyed at the moment when the monopile 12 hits the bag members 21a, and the block objects in the bag members 21a are left inside the monopile 12 and the bag members 21a lose their shape (FIG. 3A). Then, a plurality of bag members 22, 23 are stacked on the bag members 21a that enclose the monopile 12 as the first layer (FIG. 3B).

[0021]

The arrangement of the bag members is not limited to this, and the bag members can be installed as shown in FIG. 4A and 4B. Referring to FIG. 4A, a plurality of bag members 21 are installed in advance at a constant distance from the installation site in which a monopile 12 is to be driven. After the monopile 12 is driven in, a plurality of bag members 24, 25 are installed in the gap between the bag members 21 and monopile 12 (FIG. 4B). [0022]

In the embodiments described above, when a monopile 12 is used as a foundation of an offshore wind generation facility, firstly an installation site 11 of the monopile 12 is located, a plurality of bag members 21 are placed around the monopile installation site 11, and then the monopile 12 is driven into the monopile installation site 11.

[0023]

Consequently, scour, which has hitherto occurred, can be prevented. In addition, since in the conventional practices a monopile is firstly driven in, the monopile becomes an obstacle for the bag members to be installed; however, the embodiments make it easy to provide scour protection due to the absence of the obstructive monopile.

[0024]

Although the bag members 21 provided around the monopile 12 basically form only a single layer, except for the case shown in FIG. 3B, in the above embodiments, it is preferable to stack the bag members 21 on top of each other in layers around the monopile 12 from the viewpoint of scour protection. FIGS. 5A and 5B show an example of a stack of bag members. FIGS. 5A and 5B illustrate steps subsequent to the steps shown in FIGS. 2A, 2B and FIGS. 4A, 4B in the scour protection method for the foundation of the offshore wind generation facility.

[0025]

Referring to FIGS. 5A, 5B, in this embodiment, bag members 22 of the second layer are stacked on bag members 21 of the first layer around a monopile 12.

[0026]

In this embodiment, a single layer of bag members 22 are provided along the outer circumference of the monopile 12 as a stack of the bag members.

[0027] Alternatively, a plurality of layers of bag members can be arranged to form a pyramid shape with a monopile 12 at the center.

[0028]

Next, the method for installing a plurality of bag members around a monopile 12 will be described. FIG. 6A is a front view of a bag-member installation jig that is used to place the plurality of bag members 21 all at once.

[0029]

Referring to FIG. 6A, a bag-member installation jig 50 includes a jig body 51 that is a single rod-like member made of shaped steel or the like, suspension-rope attachments 52a, 52b mounted on upper parts of the jig body 51 to attach suspension ropes 55, 56, respectively, and bag-member hangers 53a to 53c mounted on lower parts of the jig body 51 to hang bag members 21. As shown in FIG. 6A, the suspension ropes 55, 56 have hanging sections 55a, 55b and 56a, 56b, respectively, on the opposite ends. The hanging sections 55b, 56b at the upper ends are hung on a hook 57 of a crane or the like.

[0030]

The bag-member hangers 53a to 53c are arranged at predetermined spacings. The spacing between the bag-member hangers is selected such that the bag members 21 are placed adjacent to each other as shown in FIG. lA or 2A through a single moving operation of the jig body 51.

[0031]

In addition, the hanging members 54a to 54c connected with the bag-member hangers 53a to 53c hang the bag members 21 with hooks 58 with an automatic releasing device. The hooks 58 with an automatic releasing device make it easy to release the bag members 21 after being installed adjacent to each other.

The specific structure of the hook 58 with an automatic releasing device will be shown in FIG. 6B. Referring to FIG. 6B, the hook 58 is attached to a hanging part 54d provided at each lower end of the hanging members 54a to 54c and has a hook portion 59c that can rotate about a pivot 59b. Once the bottom of the bag member 21 abuts against the seabed or a destination, the hook portion 59c rotates downward as indicated by an arrow in FIG. 6B and releases the engagement with the bag member 21 hung on the hook portion 59c.

[0032]

Next, some patterns of hanging the bag members by the bag-member installation jig 50 will be described. FIGS. 7A, 7B, 7C and FIGS. 8A, 8B illustrate patterns of hanging bag members by the bag-member installation jig 50. FIGS. 7A and 7B include plan views and front views, respectively, showing hanging patterns of a plurality of bag members to be installed in line, and FIG. 7C includes front views showing the arrangements of the installed bag members. In this description, four patterns are shown from the left.

[0033]

The first pattern includes four bag members placed in a first layer and three bag members placed in a second layer over the first layer. In the second pattern, four bag members are contiguously placed in the first layer. In the third pattern, three bag members are placed in a first layer with a space therebetween and two bag members are placed over the spaces, respectively, in a second layer over the first layer. The two bag members in the second layer also have a space between them. In the fourth pattern, one bag member is first placed horizontally, and then the next bag member is placed so as to overlap the left edge of the firstly- placed bag member. Consequently, two bag members lean on the adjacent bag members so that their right edges overlap the adjacent bag members.

[0034]

FIG. 8A and FIG. 8B include plan views and front views, respectively, each showing a hanging pattern to install a plurality of bag members not in a line, but in a predetermined shape. In this description, five patterns are shown from the left. [0035]

The first pattern is a square pattern with four bag members placed on each side. The second pattern has two rows of four bag members adjacent to each other. The third pattern has two rows of four bag members placed densely adjacent to each other. The fourth pattern is in a ring shape with twelve bag members placed adjacent to each other. The fifth pattern is in a fan shape with six bag members placed on the inner arc and eight bag members placed on the outer arc, the inner and outer arcs being adjacent to each other.

[0036]

As shown in FIG. 8A, the respective jig bodies 51 may be provided with beams that connect necessary parts to make it possible to hang the individual bag members.

[0037]

Using these different jigs depending on need enables installation of the plurality of bag members in a required pattern in one operation.

[0038]

Next, yet another embodiment of the present invention will be described. Each of FIGS. 9A, 9B, 9C illustrates a step in a method for installing bag members according to the embodiment of the invention. FIG. 9A shows the first step, and corresponds to FIG. 2A in the previous embodiment. In FIG. 9A, bag members 21 are arranged adjacent to each other at spacings along the outer circumference of a monopile 12. In other words, the plurality of bag members 21 are arranged in a layer around the monopile 12. In this embodiment, bag members of the second layer are installed. The bag members of the second layer are displaced from the bag members 21 of the first layer. An exemplary arrangement of the bag members 23 of the second layer is shown in FIG. 9B. In FIG. 9A, six bag members are arranged around the monopile 12 at spacings so as to form a hexagon having a longitudinal axis in X direction (direction indicated by an arrow in FIG. 9A), whereas in FIG. 9B six bag members are arranged around the monopile 12 at spacings so as to roughly form a circle having a longitudinal axis in Y direction (direction indicated by an arrow in FIG. 9B). The arrangement of the stacked bag members is not limited to this and can be anything if only the stacked bag members are displaced from each other vertically.

[0039]

The vertically displaced bag members are shown in a plan view of FIG. 9C. In this case as shown in FIG. 9C, the bag members in an upper layer are arranged on gaps between the bag members in a lower layer.

[0040]

The bag members stacked in the aforementioned manner are kept in close contact and therefore are preferable as scour protection.

[0041]

As with the other embodiments, the number of layers is not limited to two and can be three or more, or the bag members can be stacked in a pyramid shape.

[0042]

According to the embodiments described above, in order to build an offshore wind generation facility with a monopile, a plurality of bag members are installed before the monopile is driven in. Therefore, the scour protection method for the foundation of the offshore wind generation facility according to the embodiments can provide scour protection even at locations where scour-protecting bag members could not be installed after the foundation was built.

[0043]

The examples are shown in FIGS. 10A, 10B and IOC. As shown in FIGS. 10A to IOC, in a conventional case of a jacket foundation 13 (FIG. 10B) and a tripod foundation 14 (FIG. IOC), once they are set up, it is impossible to install scour-protecting bag members in areas inside the foundations 13, 14. However, the embodiments adopting previous installation of bag members make it possible to provide scour protection even in the case of the above foundations.

[0044]

Next, yet another embodiment of the present invention will be described. FIGS. 11A and 11B illustrate a method for installing a plurality of bag members around a monopile according to the embodiment of the invention.

[0045]

In advance, a plurality of bag members 21 attached with a string 27 along the outer circumference of a monopile 12 are prepared. The monopile 12 with the bag members 21 attached thereto is transported to a predetermined installation site by a barge 71 with a crane 70 as shown in FIG. 11A. Then, as shown in FIG. 11B, the monopile 12 is driven into the seabed so that the bag members 21 are installed at the predetermined site on the seabed. Consequently, the monopile 12 and bag members 21 are installed by a single operation so as to fill the gaps between the bag members 21 and monopile 12 and between the bag members 21.

[0046]

As described above, this embodiment enables simultaneous installation of a plurality of bag members 21 and a monopile 12.

[0047]

In the above -described embodiments the contents of the bag members are predetermined block objects! however, this is merely an example and can be crushed stone, tires, or the like. Alternatively, more preferable contents are something having a greater specific gravity, such as iron sludge and iron ore.

[0048]

Although the embodiments of the present invention have been described with reference to the figures, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the above illustrated embodiments within the same scope as, or an equivalent scope to, the present invention.

Industrial Applicability

[0049]

The scour protection method for the foundation of the offshore wind generation facility according to the present invention can prevent scour from occurring and therefore is advantageously used as a scour protection method for a monopile type of foundation of an offshore wind generation facility.

[0050]

11 installation site

12 monopile

21,22,24,25 bag members

30 seabed

50 bag-member installation jig

51 jig body

Claims

A scour protection method for a foundation of an offshore wind generation facility comprising the steps of

locating a site at which a monopile is to be installed.^*

placing a plurality of bag members around the monopile installation site; and

driving the monopile into the monopile installation site. [2] The scour protection method for the foundation of the offshore wind generation facility according to claim 1, wherein

the step of placing the plurality of bag members around the monopile installatio site includes step; of arrangin the plurality of bag members into a rin shape whose inner circumference circumscribes the monopile installation site and has a predetermined diameter, and the predetermined diameter of the inner circumference along which the plurality of bag members are arranged is greater than the outer diameter of the monopile to be installed.

The scour protection method for the foundation of the offshore wind generation facility according to claim 1 or 2, wherein

the step of placing the plurality of bag members around the monopile installation site includes a step of placing the plurality of bag members so as to enclose the monopile in multiple horizontal tiers.

The scour protection method for the foundation of the offshore wind generation facility according to ay one of claims 1 to 3, wherein

the step of placing the plurality of bag members around the monopile installation site includes a step of stacking the plurality of bag members on top of each other.

The scour protection method for the foundation of the offshore wind generation facility according to any one of claims 1 to 4, further comprising a step of

preparing a bag-member installation jig capable of hanging the plurality of bag members all at once, wherein

the step of placing the plurality of bag members around the monopile installation site includes a step of installing the plurality of bag members by using the prepared bag-member installation jig.