JP7345701B1 - How to remove the scour prevention unit - Google Patents

Abstract

[Problem] To provide a method for removing a scouring prevention unit, which allows the hanging part of the scouring prevention unit to be easily removed even after a long period of time has passed, and the scouring prevention unit can be easily lifted up and removed. [Solution] A scour prevention unit 10 equipped with a hanging part 25 is laid flat or stacked in multiple layers on the seabed, and a float 30 is attached to the hanging part 25 of the scour prevention unit 10. The hanging part 25 of the scour prevention unit 10 can be lifted using the float 30 floating in the water as a mark. [Selection diagram] Figure 5

Description

The present invention relates to a method for removing a scour prevention unit in which a block of filling material is enclosed in a bag body equipped with a hanging portion.

Monopile (single pile) is used as the foundation type for offshore wind power generation facilities in many cases.
In general, monopile type foundations have a large diameter foundation, so anti-scouring measures are applied to prevent the area around the foundation from being scoured by waves, currents, etc.
As one type of scour prevention work, for example, it is known that a plurality of scour prevention units are laid flat or stacked on the ground around a monopile (Patent Document 1).
The scouring prevention unit is a water-permeable structure in which a block of filling material is enclosed in a mesh bag, and functions as a mulch material and a scouring prevention material (Patent Document 2).

Offshore wind power generation facilities have a useful lifespan (approximately 30 years), and when that lifespan is reached, the power generation facility, including the anti-scouring unit, must be removed to restore the facility to its original condition.
Generally speaking, the method of removing a heavy scour prevention unit is to use a marine work boat equipped with a crane, etc., to hang a hook on a hanging rope attached to the scour prevention unit and lift it up. Adopted.

Japanese Patent Application Publication No. 2014-169625 Japanese Patent Application Publication No. 11-131447

Conventional anti-scouring units have the following problems to be solved.
<1> To remove the scour prevention unit, it is necessary to hook the hook of the crane to the hanging rope of the scour prevention unit and lift it up.
However, after a very long period of time has passed in the water or under the sea, the ropes and knitted fabrics attached to the scour prevention unit are likely to be buried in the bottom of the water or in sediments on the ocean floor, and furthermore, the deeper the water is, the worse visibility becomes.
Therefore, it is extremely difficult for a diver to visually detect the hanging portion of the scour prevention unit.
<2> For example, it is conceivable that a diver manually digs through accumulated earth and sand to find the hanging part of a buried scour prevention unit, but this would place an enormous workload on the diver.
<3> Diving time for divers to remove the scour prevention unit becomes longer.
The longer the diving time, the greater the risk to the diver (diving disease), as well as the cost of final removal of the anti-scouring unit.
<4> Conventionally, it has not been assumed that the scouring prevention unit will be easily removed after a long period of about 30 years, so proposals for techniques to deal with this are required.

The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to easily remove the hanging part of the scour prevention unit even after a long period of time has passed, and to easily remove the scour prevention unit. To provide a method for removing a scour prevention unit that can be lifted and removed.

The present invention uses a scouring prevention unit in which a blocky filling material is enclosed in a net bag body equipped with a hanging part, and the scouring prevention unit is laid flat on the bottom of the water or stacked in multiple layers. A method for removing a unit, wherein a float capable of floating under buoyancy is attached to the hanging part of the scour prevention unit, and the hanging part of the scour prevention unit is lifted using the float floating in water as a landmark. made possible.
In another form of the present invention, the float may be attached to the hanging part of the scour prevention unit via a mooring rope, or the float may be attached directly to the hanging part of the scour prevention unit. .
In another embodiment of the present invention, the hanging portion of the scour prevention unit is a hanging rope.
In another embodiment of the present invention, when the scour prevention units are stacked in multiple layers, the scour prevention units are sequentially removed from the upper layer to the lower layer.
In another embodiment of the present invention, a number corresponding to the scour prevention unit may be displayed on the float.
In another embodiment of the present invention, the float may be coated with a fluorescent paint mixed with an algaecide.

The present invention has at least one of the following effects.
<1> By attaching a float to the hanging part of the scour prevention unit, the position of the hanging part of the scour prevention unit can be determined using the float floating in the water as a landmark, so the scour prevention unit can be easily removed. Can be done.
<2> After several decades have passed after installation, algae, shellfish, etc. may adhere to the hanging rope of the anti-scouring unit or the knitted fabric of the bag, or the anti-scouring unit may become buried in accumulated soil, etc. Even if the installation environment changes due to changes in the installation environment, the hanging part of the scour prevention unit can be found using the float floating above the scour prevention unit as a landmark.
Therefore, when the useful life of the offshore wind equipment (approximately 30 years) has passed, the scour prevention unit can be removed and the equipment can be efficiently restored to its original state.
<3> It is possible to shorten the diving time by a diver when removing the scour prevention unit, thereby reducing the risk to the diver and the cost of removing the scour prevention unit.
<4> Since the float connected to the scour prevention unit continues to float and move in the sea, it is difficult for algae, shellfish, etc. to adhere to the float.
<5> When the float is attached to the hanging part of the scour prevention unit via a mooring rope, the float floats via the mooring rope, making it easier to find the float.
<6> By adjusting the length of the mooring rope, there is no need to worry about the float being buried in accumulated earth and sand.
<7> When scour prevention units are stacked in multiple stages, if the upper layer is removed, the float provided in the scour prevention unit of the next layer will float due to buoyancy.
Therefore, there is no problem even if the float is caught between the upper and lower scour prevention units, so the installation work of the scour prevention units can be carried out roughly.
<8> If a number corresponding to the scour prevention unit is displayed on the float, the number of scour prevention units can be easily managed at the time of removal.
<9> If the numbering is displayed on the float and the scour prevention units are stacked, the number of installed units for each layer can be managed by number. By being able to manage the number of scour prevention units installed for each layer, it is no longer possible to lift up the next layer's scour prevention units by mistake during removal.
<10> Applying a fluorescent paint mixed with an algae preventive to the float not only improves the visibility of the float, but also effectively prevents the float from settling due to adhesion of seaweed.
<11> By adjusting the length of the mooring rope, it can be installed without affecting the navigation of ships sailing nearby, ships conducting surveys, ships conducting inspection operations, etc.

A perspective view of a scour prevention unit used in the present invention Side view of the bag that constitutes the scour prevention unit Explanatory diagram of how to install the scour prevention unit Explanatory diagram of the scour prevention unit after stacking and installation Explanatory diagram of how to remove the scour prevention unit

The present invention will be described below with reference to the drawings.
In this example, a configuration in which a scour prevention unit 10 is installed on the seabed ground around a monopile of an offshore wind power generation facility will be described.

<1> Scour Prevention Unit Referring to FIG. 1, a scour prevention unit 10 on which the present invention is based is composed of a bag body 20 and a filling material 26 housed in the bag body 20.
In the present invention, by providing one or more floats 30 on a part of the hanging part of the scour prevention unit 10, a diver can easily find the hanging part when the scour prevention unit 10 is removed.

<2> Bag body The bag body 20 includes a mesh-like bag body 21 filled with a filling material 26, a neck rope 24 and a hanging rope 25 that are attached to the opening 23 of the bag body 21 in a circumferential manner. and.

<2.1> Bag Body The bag body 21 is a bottomed bag having an opening 23.
The bag body 21 is made of a textile knitted fabric exhibiting a mesh (knitted fabric) structure having flexibility and water permeability.
In order to reduce waste of knitted fabric, a bag body 21 manufactured according to the capacity of the filling material 26 (for example, 1 m ³ to 10 m ³ ) is used, and the bag body 21 is made according to the capacity of the filling material 26. Produced using knitted fabric with the minimum area.

As the knitting yarn for the knitted fabric of the bag body 21, for example, synthetic fiber yarn such as polyester fiber yarn, polyamide fiber yarn, polyacrylic fiber yarn, or natural fiber yarn such as cotton yarn or hemp yarn can be used alone or in combination. . In practice, a raschel net made of double knitted synthetic fiber yarns such as polyester can be used.

This knitted fabric has a hexagonal or diamond-shaped mesh 22. The mesh 22 is dimensioned to prevent the filling material 26 from slipping out.

<2.2> Rope Materials Near the opening 23 of the bag body 21, at least two rope materials, a neck rope 24 and an endless hanging rope 25, are attached in a circumferential manner.

The opening rope 24 is a rope material for closing the opening 23, and after putting the filling material 26 into the bag body 21 using a backhoe or the like, the opening rope 24 is squeezed and the filling material 26 is placed in the bag body 20. Enclose.

The hanging rope 25 is an endless rope material for lifting the scouring prevention unit 10, and the rope is inserted into the mesh of the bag body 21, and is pulled out in a loop shape from multiple locations (for example, 6 locations) on the bag body 21. The pulled out hanging rope 25 is used by being hung from a hook 50 of a crane or the like at a plurality of locations.

<2.3> Hanging Part The hanging part of the scour prevention unit 10 means a part for hanging and lifting the hook 50 of the crane.
In this example, a mode in which the hanging portion is a hanging rope 25 will be described, but the hanging portion may be a neck rope 24 or a separate rope in addition to the hanging rope 25.

<3> Filling material The filling material 26 can be, for example, natural aggregate such as cobblestone, concrete debris, fired bodies of various wastes, or the like.
When used for foundation hardening, a filling material 26 with a diameter of about 150 mm is used, but the size of the filling material 26 can be selected as appropriate depending on the intended use.

<4> Float The float 30 is a floating body for marking the position of the hanging part (hanging rope 25) of the scour prevention unit 10, and is attached in advance before the scour prevention unit 10 is installed.

<4.1> Mooring Rope The float 30 is attached to the hanging rope 25 via a mooring rope 31.
The mooring rope 31 is a highly durable rope material for connecting the hanging rope 25 and the float 30.
The total length of the mooring rope 31 is adjustable, and the total length of the mooring rope 31 is appropriately selected depending on the installation site.
The entire length of the mooring rope 31 may be long enough to prevent the float 30 from being buried in seabed sediment.

The mooring rope 31 is not essential, and it is also possible to omit the mooring rope 31 and provide the float 30 directly on the hanging rope 25.

<4.2> Float material The float 30 is made of a material that can maintain buoyancy for a long period of time, such as polyethylene (PE), ethylene-vinyl acetate copolymer resin (EVA), etc., which is waterproof and water absorbent. You can use materials that do not have
The float 30 may have either a solid structure or a hollow structure.
The float 30 is preferably made of a material that can be crushed to restore its shape.

<4.3> Buoyancy of the Float Regarding the buoyancy of the float 30, in the form in which the float 30 is indirectly attached via the mooring rope 31, a buoyancy that allows the float 30 to float independently is ensured.

In the form in which the float 30 is directly attached to the hanging rope 25, buoyancy that allows the hanging rope 25 to be lifted is ensured.
The buoyancy of the float 30 can be adjusted by selecting the material, volume, etc.

<4.4> Shape and Structure of Float The shape of the float 30 is not particularly limited and is not limited to the illustrated ellipse, but may be other three-dimensional shapes such as a sphere, a cylinder, a prism, etc.

In this example, one end of the mooring rope 31 is inserted through a through hole formed in the center of the float 30 and fixed therein, but the one end of the mooring rope 31 is not limited to a through hole, and is a part of the float 30. It is sufficient if it is connected to the section.

<4.5> Other forms of floats The visibility of the float 30 can be increased by coating the float 30 with a fluorescent color, or by applying a mixture of fluorescent paint and an anti-algae agent, it is difficult for algae to adhere to the float 30. You may also do so.

Furthermore, by assigning numbers to the floats 30 and laying them, it is possible to easily manage the number of scour prevention units 10 when installing and removing them.

[From installation to removal of scour prevention units]
A series of operations from manufacturing the scour prevention unit 10 to installation and removal of the scour prevention unit 10 will be explained.

<1> Fabrication of scour prevention unit After the filling material 26 is put into the bag body 21, the opening rope 24 is squeezed and the filling material 26 is enclosed in the bag body 20 to manufacture the scour prevention unit 10.
Since the manufacturing process of the scour prevention unit 10 is well known, detailed explanation will be omitted.
In the present invention, the float 30 is attached to the hanging portion of the scour prevention unit 10.

<2> Installation work of scour prevention unit The installation work of the scour prevention unit will be explained with reference to FIG. 3.
A single scour prevention unit 10 or a plurality of scour prevention units 10 are laid on the seabed 40.
When installing the scour prevention unit 10, the hanging rope 25 is pulled out in a loop from multiple locations (for example, 6 locations) on the bag body 21, and the multiple locations of the pulled out hanging rope 25 are hung on hooks 50 of a crane or the like. Stop.

When the scour prevention unit 10 is placed on the seabed 40, the float 30 connected to the hanging rope 25 floats directly above.
When stacking the scour prevention units 10, the float 30 provided in the next layer (lower layer) scour prevention unit 10 may be sandwiched between the scour prevention units 10 in the upper and lower layers.

The float 30 functions as follows when the scour prevention unit 10 is installed.
A float 30 is floating just above the previously installed scour prevention unit 10, and indicates the position of the installed scour prevention unit 10.
Therefore, even at a site with deep water and poor visibility, a separate scour prevention unit 10 can be easily installed in a short time adjacent to the installed scour prevention unit 10 using the float 30 as a landmark.

<3> During installation of scour prevention unit FIG. 4 shows a state in which a long period of time has passed after the scour prevention unit 10 was installed.
If a long time passes after installation, algae, shellfish, etc. may adhere to the hanging rope 25 of the scouring prevention unit 10 and the knitted fabric of the bag body 21, or the scouring prevention unit 10 may become buried in the covering layer 41 of accumulated earth and sand. do.
Since the float 30 connected to the hanging rope 25 of the scour prevention unit 10 is floating and movable in the sea, algae, shellfish, etc. are difficult to adhere to, and there is no fear that the main body of the float 30 will be buried in the coating layer 41.

<4> Removal of scour prevention units As described above, even after a long period of time, some of the floats 30 connected to the installed scour prevention units 10 float away from the scour prevention units 10.
Even if the entire scour prevention unit 10 is covered with the covering layer 41, the float 30 floats in the sea through the mooring rope 31 extending from the covering layer 41.
Therefore, the hanging rope 25, which is the hanging part of the scour prevention unit 10, can be found using the float 30 floating in the sea as a landmark.

Even if sediments are rolled up and suspended when a diver touches the bottom or leaves, the position of the hanging rope 25 can be specified using the floating float 30 as a landmark.

As shown in FIG. 5, the hanging rope 25 is manually let out using the float 30, a hook 50 of a crane or the like is hooked to the hanging rope 25, and the scour prevention unit 10 is removed.

The task of finding the float 30 can be performed not only by a diver but also by using a robot such as an underwater drone.
Similarly, the work of hooking the hook 50 to the hanging rope 25 can be performed not only by a diver but also by using a work robot.

After removing the upper scouring prevention unit 10, the adjacent scouring prevention units 10 on the left and right sides are also removed in the same manner.

By removing the upper layer scour prevention unit 10, the upper surface of the next layer scour prevention unit 10 is exposed.
The float 30 floats because the upper surface of the scour prevention unit 10 of the next layer is exposed.
Using the floating float 30 as a clue, a hanging rope 25 is found, a hook 50 of a crane or the like is hung thereon, and the scour prevention unit 10 of the next layer is removed.

As described above, since the hanging rope 25 of the scour prevention unit 10 can be easily found using the floating float 30 as a landmark, when the offshore wind power equipment is restored to its original state due to equipment removal due to the expiration of its service life, Even if the scour prevention unit 10 has many layers, it can be easily removed from the upper layer.

At the time of removal, the position of the hanging rope 25 can be clearly grasped through the float 30.
As a result, the diver can place himself in a safe position (a position where he will not be caught by the crane's hook) and guide the crane's hook 50 to sling, thereby improving work safety.
By being able to discover the position of the hanging rope 25 early, the diving time for the diver can be shortened, the risk of diving disease is reduced, and work safety is improved.
When a series of underwater operations are performed by a diver, the diving time can be significantly shortened, so the work efficiency is significantly improved and the cost for removing the scour prevention unit 10 can be reduced.

[Other usage methods]
Other installation sites for anti-scouring units will be explained below.

<1> Work to reload the scour prevention unit The float 30 can also be utilized in the work to reload the scour prevention unit 10.
If the scour prevention unit 10 is damaged or deformed due to ocean currents, tides, etc. in the sea, use the float 30 connected to the hanging part of the scour prevention unit 10 as a guide to remove the suspension rope 25 of the scour prevention unit 10. Since the position can be specified, reloading (repair/renovation) work of the scour prevention unit 10 can be performed quickly.
The float 30 can be used to quickly reload (repair/renovate) the scour prevention unit 10, not only in the sea, but also when the scour prevention unit 10 is damaged or deformed due to rising water or rapid changes in river flow. can be done.

<2> Float numbering By numbering and installing the floats 30, the number can be easily managed when the scour prevention unit 10 is removed.
Furthermore, by assigning numbers to the floats 30 and installing the scour prevention units 10, the number of installed units for each layer can be managed by numbers.
By being able to manage the installation number, it is possible to prevent the scouring prevention unit 10 of the next layer from being pulled up by mistake during removal.

<3> Other applicable works for the scour prevention unit The above describes the form in which the scour prevention unit 10 is installed on the seabed ground around the monopile of an offshore wind power generation facility, but the scour prevention unit 10 is explained below. It can be applied to various types of construction work.

a) Foot protection work around bridge piers.
b) Foot protection work for port facilities (breakwaters, seawalls).
c) Temporary cofferdam (scouring prevention work) for river construction.
d) Temporary construction work that requires removal.
e) Emergency temporary construction work for disaster recovery, etc.

10...Scouring prevention unit 20...Bag body 21...Bag body 22...Mesh 23...Opening part 24...End squeezing rope 25...Hanging Rope (hanging part)
26... Filling material 30... Float 31... Mooring rope 40... Seabed 41... Covering layer

Claims (7)

A method for removing a scouring prevention unit that is placed flat on the bottom of water or stacked in multiple layers, using a scouring prevention unit that is made of a net bag with a hanging part and filled with a block of filling material. And,
A float capable of floating under buoyancy is attached to the hanging part of the scour prevention unit,
The hanging part of the scour prevention unit can be lifted using the float floating in the water as a mark,
How to remove the scour prevention unit. 2. The method for removing a scour prevention unit according to claim 1, wherein the float is attached to a hanging portion of the scour prevention unit via a mooring rope. 2. The method for removing a scour prevention unit according to claim 1, wherein the float is directly attached to a hanging part of the scour prevention unit. 4. The method for removing a scour prevention unit according to claim 1, wherein the hanging portion of the scour prevention unit is a hanging rope. 2. The method for removing a scour prevention unit according to claim 1, wherein when the scour prevention units are stacked in multiple layers, the scour prevention units are sequentially removed from the upper layer to the lower layer. 2. The method for removing a scour prevention unit according to claim 1, wherein a number corresponding to the scour prevention unit is displayed on the float. 2. The method for removing a scour prevention unit according to claim 1, wherein the float is coated with a fluorescent paint mixed with an anti-algae agent.

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