US20110158753A1 - Method for planarizing unevenness of the seabed - Google Patents
Method for planarizing unevenness of the seabed Download PDFInfo
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- US20110158753A1 US20110158753A1 US12/979,602 US97960210A US2011158753A1 US 20110158753 A1 US20110158753 A1 US 20110158753A1 US 97960210 A US97960210 A US 97960210A US 2011158753 A1 US2011158753 A1 US 2011158753A1
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- fus
- seabed
- filter units
- foundation
- unevenness
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L1/00—Laying or reclaiming pipes; Repairing or joining pipes on or under water
- F16L1/12—Laying or reclaiming pipes on or under water
- F16L1/16—Laying or reclaiming pipes on or under water on the bottom
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/10—Placing gravel or light material under water inasmuch as not provided for elsewhere
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/42—Foundations for poles, masts or chimneys
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/52—Submerged foundations, i.e. submerged in open water
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D13/00—Assembly, mounting or commissioning of wind motors; Arrangements specially adapted for transporting wind motor components
- F03D13/20—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors
- F03D13/22—Foundations specially adapted for wind motors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L1/00—Laying or reclaiming pipes; Repairing or joining pipes on or under water
- F16L1/12—Laying or reclaiming pipes on or under water
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G1/00—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines
- H02G1/06—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines for laying cables, e.g. laying apparatus on vehicle
- H02G1/10—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines for laying cables, e.g. laying apparatus on vehicle in or under water
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G9/00—Installations of electric cables or lines in or on the ground or water
- H02G9/02—Installations of electric cables or lines in or on the ground or water laid directly in or on the ground, river-bed or sea-bottom; Coverings therefor, e.g. tile
- H02G9/025—Coverings therefor, e.g. tile
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0039—Methods for placing the offshore structure
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0091—Offshore structures for wind turbines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2240/00—Components
- F05B2240/90—Mounting on supporting structures or systems
- F05B2240/95—Mounting on supporting structures or systems offshore
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/72—Wind turbines with rotation axis in wind direction
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/727—Offshore wind turbines
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Paleontology (AREA)
- Mining & Mineral Resources (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Civil Engineering (AREA)
- Mechanical Engineering (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Wind Motors (AREA)
- Revetment (AREA)
Abstract
At a location where unevenness 1000 is present, the condition of a seabed 200 is investigated in advance to examine the respective numbers of large filter units 51 and small filter units 52 to be used, and the position where the large filter units 51 and the small filter units 52 are to be installed. Based on the investigation result, the small filter units 52 are installed on the bottom of the unevenness 1000. The large filter units 51 are installed on the upper surface formed by the installed small filter units 52, and are leveled so that the upper surface formed by the installed large filter units 51 becomes flush with the seabed 200.
Description
- 1. Field of the Invention
- The present invention relates to methods for planarizing unevenness of the seabed.
- 2. Description of the Background Art
- The seabed has geographical features called “unevenness” which is an uneven surface. Referring to
FIG. 16A ,unevenness 1000 as used herein refers to a portion that is recessed with respect to the surroundingseabed 200. Theseabed 200 is not flat at a location where theunevenness 1000 is present. Thus, it may not be possible to provide a structure at such a location on theseabed 200. A method that deals with the unevenness is disclosed in, e.g., Japanese Patent Publication No. 2006-322400 of unexamined applications. In Japanese Patent Publication No. 2006-322400 of unexamined applications, for installation of a foundation of an offshore wind power generation using a caisson, covering material units are positioned between a friction increasing mat provided on the lower surface of the foundation, and the surface of the seabed in order to deal with the unevenness and to increase frictional resistance. The number of covering material unit is determined corresponding to distribution of the ground level of the seabed. - According to Japanese Patent Publication No. 2006-322400 of unexamined applications, the covering material units are positioned under the foundation in the case of a structure in which the foundation has a planar bottom surface like a caisson. That is, the covering material units are positioned under the structure.
- However, the structure of Japanese Patent Publication No. 2006-322400 of unexamined applications cannot be applied to, e.g., linear structures such as submarine cables. If the covering material units are positioned only under the submarine cable, the submarine cable can move onto the unevenness where no covering units are positioned, due to the tidal currents and the like. In such a case, referring to
FIG. 16B , asubmarine cable 20 is bent over theunevenness 1000, imposing a considerable strain on thesubmarine cable 20 at bothends unevenness 1000. Thus, thesubmarine cable 20 can be damaged. One conventional possible solution to this problem is to repair the unevenness by dumping crushed stones with a tremie pipe or the like. However, the dumped crushed stones can be carried away by the influence of the tidal currents, whereby the unevenness can be restored. Another conventional possible solution is to repair the unevenness by installing a wire cylinder, a large concrete block, or the like therein. However, the wire cylinder, the large concrete block, or the like do not completely fit in the unevenness, and the part of the wire cylinder, the large concrete block, or the like, which does not fit in the unevenness, serves as resistance to the tidal currents, causing an excess flow. Such an excess flow causes a phenomenon called “scouring,” a phenomenon that the seabed is worn away and chipped off, near the part of the wire cylinder, the large concrete block, or the like serving as resistance. Thus, the unevenness can be restored. - It is an object of the present invention to provide a method for planarizing unevenness of the seabed.
- According to the present invention, a method for planarizing unevenness which is an uneven surface of a seabed includes the steps of; installing a plurality of bag-shaped filter units, each containing predetermined block objects, on the unevenness; and leveling the plurality of installed filter units so that an upper surface formed by the plurality of installed filter units becomes flush with the seabed.
- Preferably, the step of installing the plurality of filter units includes the step of locating a position where the filter units are to be installed, by using a GPS.
- According to the present invention, the plurality of bag-shaped filter units, each containing predetermined block objects, are installed on the unevenness, and the plurality of installed filter units are leveled so that the upper surface formed by the plurality of installed filter units becomes flush with the seabed. Thus, the unevenness can be turned into a substantially flat seabed.
- Preferably, the filter units include a first filter unit having a first size and a second filter unit having a second size larger than the first size, and, the step of installing the plurality of filter units includes the step of placing the second filter unit on the first filter unit.
- Preferably, the filter units have a predetermined size and the step of installing the plurality of filter units includes the step of placing crushed stones on said unevenness before placing the filter units with the predetermined size.
- Preferably, the filter units have a predetermined outer size and include a first filter unit having a first block objects with a first size and a second filter unit having a second block objects with a second size larger than the first size, and the step of installing said plurality of filter units includes the step of placing the second filter unit on the first filter unit.
- Preferably, the step of installing the plurality of filter units includes the step of placing crushed stones at the bottom of said unevenness before placing a plurality of the filter units.
- Preferably, the volume of the filter units is equal or smaller than the volume of the unevenness.
- Preferably, the filter unit includes a bag body and block objects, and when the filter unit is hung up, assuming that the height of the bag body from the closed portion to the bottom is H1 and the height of a space without the block objects is H2, the amount of block objects obtained by (H2/H1)×100 is 25-80%.
- Still preferably, the porosity of the knitted fabric of the bag body is 45% to 90%.
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FIG. 1 is a schematic view showing a wind power generation system, a tower, and a foundation, to which a method for constructing a foundation for a wind power generation system of the first embodiment is applied. -
FIG. 2A is a schematic view showing a filter unit (FU), andFIG. 2B is a schematic view showing the state where the FU is installed on an uneven surface of the seabed. -
FIG. 3A is a side view of piles showing how FUs are located among piles,FIG. 3B is a diagram viewed from III B-III-B inFIG. 3A , andFIG. 3C is a diagram viewed from III C-III C inFIG. 3A . -
FIGS. 4A , 4B, 4C, 4D, 4E, and 4F are diagrams sequentially illustrating the method for constructing a foundation for a wind power generation system. -
FIG. 5 is a schematic view showing a tower, and a foundation, to which another method for constructing a foundation for a wind power generation system of the first embodiment is applied. -
FIGS. 6A and 6B are schematic view showing an example in which FUs are installed for an existing foundation. -
FIG. 7 is a schematic view showing a tower, and a foundation, to which a method for constructing a foundation for a wind power generation system of the second embodiment is applied. -
FIGS. 8A , 8B, 8C, 8D, 8E, 8F, 8G, and 8H are diagrams sequentially illustrating the method for constructing a foundation for a wind power generation system of the second embodiment, andFIG. 8I is a diagram viewed from position VIII I-VIII I inFIG. 8E .FIGS. 8J and 8K are diagrams showing an example in which FUs are installed for an existing foundation. -
FIGS. 9A , 9B, and 9C are diagrams sequentially illustrating a method for protecting a submarine cable for a wind power generation system, andFIG. 9D is a diagram viewed from IX D-IX D inFIG. 9C . -
FIG. 10 is a view showing how a FU covers a cable. -
FIG. 11A is a diagram showing an example in which a submarine cable is protected by using a plurality of FUs, andFIG. 11B is a diagram viewed from XI B-XI B inFIG. 11A . -
FIG. 12A is a diagram showing an example in which a submarine cable is protected by using two FUs, andFIG. 12B is a diagram viewed from position XII B-XII B inFIG. 12A . -
FIG. 13A is a diagram showing an example in which a submarine cable is protected by using a plurality of FUs, andFIG. 13B is a diagram viewed from XIII B-XIII B inFIG. 13A . -
FIGS. 14A , 14B, and 14C are diagrams sequentially illustrating a method for planarizing an uneven surface of the seabed. -
FIG. 15 is a schematic diagram showing an example of planarization of a convex uneven surface. -
FIG. 16A is a cross-sectional view showing an uneven surface, andFIG. 16B is a cross-sectional view showing an example in which a submarine cable is installed on the uneven surface. - An embodiment of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a schematic view showing a wind power generation system and a tower which are settled on a foundation to which a method for constructing the foundation for a wind power generation system according to an embodiment of the present invention is applied. Note that the present embodiment is described with respect to an example in which the wind power generation system and the tower are supported by the foundation having piles as a base.FIG. 1 shows an offshore windpower generation system 10 for generating electrical power from offshore wind energy, atower 11, abase slab portion 12 a, piles 12 b, a plurality of filter units (hereinafter referred to as the “FUs”) 50, and acable 20. Thetower 11 holds the offshore windpower generation system 10, and extends down to a level near aseabed 200 through asea surface 100. Thebase slab portion 12 a, which is made of concrete, is fixed to thetower 11 by anchor bolts, and supports thetower 11. Eachpile 12 b, which is made of a steel pipe, is provided so as to be supported by a predetermined ground, and fixes thebase slab portion 12 a on its upper end by anchor bolts to support thebase slab portion 12 a. TheFUs 50 are installed between theseabed 200 and thepiles 12 b. Thecable 20 is extended outward from thetower 11 near theseabed 200 to transmit the electricity, generated by the windpower generation system 10, to a land-based system (not shown). Note that thetower 11 extends to such a height that enables the windpower generation system 10 to efficiently receive offshore winds. Thepredetermined ground 300 in which thepiles 12 b are fixed indicates a layer of the ground called a “bearing layer” inFIG. 1 . The bearing layer is strong enough to endure the load of the wind power generation system and the tower under various conditions such as meteorological and hydrographic conditions. That is, thepiles 12 b are driven into the ground until they reach the bearing layer, and thepiles 12 b are fixed in the bearing layer. Note that the foundation in the present embodiment includes thebase slab portion 12 a and thepiles 12 b. - The structure of the
FU 50 used in the present embodiment will be described below.FIG. 2A is a schematic view showing the state where theFU 50 is suspended by a crane of a work ship or the like, andFIG. 2B is a schematic view showing the state where theFU 50 is installed on an uneven seabed. - Referring to
FIGS. 2A and 2B , a bag comprising abag body 501 knitted with synthetic fiber yarn in which a predetermined amount of block objects such as crushed stones are placed is called the FU. TheFU 50 containing the block objects 502 includes asuspension rope 503 that allows thebag body 501 to be suspended by a crane or the like, and aconnection portion 504 provided at an end of thesuspension rope 503, and connectable to the crane for suspending thebag body 501. TheFU 50 used herein has a diameter of approximately 2.5 m when installed on a flat ground and its weight is roughly 4 t. The synthetic fiber used for thebag body 501 is, e.g., polyester. Thus, thebag body 501 does not rust in the sea water, has high resistance to acidic and alkaline water, and is less likely to corrode. Note that the synthetic fiber is not limited to polyester, and may be nylon, polypropylene, polyethylene, or the like. In addition, since a yarn of a FU is synthetic resin, endocrine disrupter and heavy metal will not solve out and no adverse effect is brought about. - In the
bag body 501, the longer side N of the mesh of the net is 50 mm, and the yarn diameter M is 10 mm. It is preferable that the yarn diameter M and the longer side N of the mesh have a relation of 3≦N/M≦20 (unit to be mm). Under this relation, none of the block objects 502 described below drop out of the mesh and thebag body 501 keeps its strength longer. - It is preferable that the predetermined amount of the block objects 502 be determined so that the porosity of the knitted fabric becomes 45% to 90%. This ensures formation of porous voids in the
FU 50, thereby reducing the dragging force while the water currents at theseabed 200 are flowing through thebag body 501. Thus, no flowing water pressure is applied to theFU 50, preventing a phenomenon called “scouring,” a phenomenon that theseabed 200 is worn away. Although the porosity relates also to the size of the block objects 502 placed in thebag body 501, at the porosity of less than 45%, the flowing water pressure is applied to theFU 50, causing scouring around thebag body 501. On the other hand, at the porosity of more than 90%, the retention of the block objects 502 is reduced. - It is preferable that the
bag body 501 be formed by knitted fabric (e.g., a raschel net) having an elongation of 30% to 80%. This enables the flexibility to be ensured, and also enables thebag body 501 to follow any shape at an installation position of theFU 50, and to be maintained in a stable state for a long time after installation of theFU 50. That is, theFU 50 can be stably maintained at the installation position for a long time, regardless of whether the installation location is flat or not. - The block objects 502 contained in the
FU 50 preferably has its diameter to be 50-300 mm and specific gravity large enough to prevent theFU 50 from being dragged when theFU 50 is installed on theseabed 200. For example, the block objects 502 are crushed stones having a grain size of 100 mm and specific gravity of 2.65. Thus, theFU 50 has a weight heavy enough to be unsusceptible to buoyancy and water currents under the sea. Note that, the smaller the grain size of the block objects 502 is, the more thebag body 501 adapts to the shape of the installation location. It is preferable that the grain size of the block objects 502 be approximately about two times the longer side N of the mesh. - Next, the predetermined amount of block objects 502 to be placed in the bag is to be explained. With reference to
FIG. 2A showing a bag when it is hung up, assuming that the height of thebag 501 from theclosed portion 505 to the bottom is H1 and the height of a space without block objects 502 is H2. The predetermined amount of block objects 502 in thebag 501 is an amount that the value obtained by (H2/H1)×100 is preferably 25-80%. The reason is that when the value is less than 25%, it means that the block objects reach itsclosed portion 505 and the adaptability to the installation position is reduced and it becomes difficult to place the bag close to the desired position. When the value is more than 80%, the shape of the FU can be changed easily, less stable, and light weight against its volume, it is possible that the FU can be driven away by a tidal wave. - In addition, since the FU has a structure described above, when it is located in the seabed, the meritorious effect is brought about that preferable environment can be provided for plants and fish in the sea.
- Next, the explanation is made as to the size of the FU. In the following explanation, the FU whose weight is less than 4 t, the diameter when it is set is less than 2 m, and the volume is less than 2 m3 is referred to as “a small FU”, whereas the FU whose weight is 4-20 ton, the diameter when it is set is 2 m-5 m, and the volume is 2-13 m3 is referred to as “a large FU”. The material and the diameter of the yarn, the mesh size including the longer side of the mesh, the diameter and specific weight of the block objects are same for both the small and the large FUs.
- The Table 1 below shows an example of the relation between the weight (size) of the individual FU and an effective flow rate of the tidal currents. Note that it is assumed in Table 1 that the same block objects whose diameter is 50-300 mm and specific weight is 2.65 are placed in each FU.
-
TABLE 1 Effective Flow Rate Weight of FU (t) of Tidal Currents (m/s) 2 Roughly 4.7 or less 4 Roughly 5.3 or less 8 Roughly 5.9 or less 20 Roughly 7.0 or less - As shown in Table 1, an appropriate type of FUs may be used according to the flow rate of tidal currents. For example, FUs having a weight of 4 t are used when the flow rate of the tidal currents is 5.0 m/s at the position where the FUs are to be installed. In addition, it is possible to change the weight of the FU and the size of block objects depending on the conditions of the performance at the position where FUs are set. As shown in Table 1, the larger the FU, the more effective to the flow rate of the tidal current, compared with the smaller FU.
- In the following description, the
FU 50 described above is used unless otherwise specified. - Note that, although the factors, such as the size of the
FU 50 itself, the material of the yarn, the thickness of the yarn, the grain size and the specific weight of the block objects are specified in theabove FU 50, the present invention is not limited to theFU 50 specified by these factors. TheFU 50 may be specified by various other factors. - Note that, for example, it is preferable that the FU used here is a scouring preventing material for an underwater structure disclosed in Japanese Patent No. 3,696,389.
- A method for installing the FUs according to the present embodiment will be described below.
FIG. 3A is a schematic-diagram seen from side showing an example around thepiles 12 b when FUs are set around thepile 12 b right before thebase slab portion 12 a is installed.FIG. 3B is a diagram viewed from III B-III B inFIG. 3A , andFIG. 3C is a diagram viewed from III C-III C inFIG. 3A . First, referring toFIG. 3A , theFUs 50 are installed between theseabed 200 and thepiles 12 b supporting the base slab portion at their upper ends. As shown by chain double-dashed line X inFIG. 3A , it is preferable that theFUs 50 be installed with no gap formed therebetween, until a flat surface is formed by the plurality ofFUs 50 according to the height of the heads of thepiles 12 b. This allows the bottom surface of the base slab portion to closely contact thepiles 12 b and the FUs when the base slab portion is installed, whereby thepiles 12 b, the base slab portion, and theFUs 50 are integrated together. This can increase the strength as a foundation including the base slab portion and the base, and can reduce the influence of tidal currents, including scouring. That is, this can increase the bearing force as a foundation for supporting the wind power generation system and the tower. Referring toFIG. 3B , a point O is the position where the center of the base slab portion is located when the base slab portion is installed on thepiles 12 b. The distance from the point O to the outermost position of the circumference of eachpile 12 b located farthest from the point O is R meters (hereinafter “m”). A circle P1 is a circle having its center located at the point O and having a radius of R m. In this case, it is preferable that the lowermost layer of theFUs 50 be provided in a range surrounded by a circle P2 having its center located at the point O and having a radius of about (R+W) m (seeFIG. 3C ). When W is between 4 m and 15 m, the effect that scouring is prevented and it is preferable that W=6 m. The larger the installation range of theFUs 50 is, the more the effects of theFUs 50 as described above are expected to be obtained. However, the effects of theFUs 50 substantially level off when the installation range of theFUs 50 exceeds the circle P2. Thus, from the standpoint of construction such as the number of FUs 50 to be installed and the amount of construction work, and the standpoint of the effects such as the effectiveness of theFUs 50, the installation range of the lowermost layer of theFUs 50 is preferably in the range surrounded by the circle P2 having a radius of about (R+6) m about the point O. Referring toFIG. 3C , it is preferable that, in a range S (a portion of the circle P2 other than the circle P1), theFUs 50 in the lowermost layer be arranged in two to five layers in the radial direction concentrically about the point O (FIGS. 3A and 3C show an example in which theFUs 50 are arranged in three layers in the radial direction). Arranging small FUs in a plurality of lines in the radial direction in the range S can implement higher stability than arranging large FUs in a single layer in the radial direction in the range S. Further, a group effect is provided by the plurality ofFUs 50 when theFUs 50 form a group. The group effect is the effect that a FU that is directly influenced by the water currents is supported by other FUs around the FU and a plurality of FUs forming the group can stably remain at the set location. As a result, a meritorious effect of preventing scour and so on can last for a long time. Contrary, arranging theFUs 50 in a single layer in the radial direction provides no effect of suppressing a turbulent flow that is caused when the tidal currents strike the foundation, and the foundation can be influenced by an excess flow generated by the tower. On the other hand, the above group effect levels off when theFUs 50 are arranged in six or more layers in the radial direction. - The larger the overall thickness of the
FUs 50, that is, the number of layers of theFUs 50 in the vertical direction, is, the higher effects theFUs 50 are expected to have. This is because increasing the overall thickness of theFUs 50 improves engagement between the plurality ofFUs 50. Thus, the plurality ofFUs 50 closely contact each other, are fixed together with no gap formed therebetween and decrease possibility of earth and sand being sucked out from the seabed surface. This increases the stability of the plurality of installedFUs 50, enabling the influence of the tidal currents including scouring to be reduced for a long time. On the other hand, the effect of preventing scouring substantially levels off when the overall thickness is equal to three or more layers. Thus, as described above, from the standpoint of construction such as the number of FUs 50 to be installed and the amount of construction work, and the standpoint of the effects such as the effectiveness of theFUs 50, it is preferable that the overall thickness of theFUs 50 be equal to two to three layers. - In addition, usually, one sized FUs are used to implement this embodiment, FUs whose sizes are different can be used. In this case, when FUs of different sizes are installed in two or more layers, it is preferable that the smaller FUs are set at the lower position and the larger FUs are at higher position. The reason for this installation is that the smaller FUs follow unevenness of the seabed, engagement between the installed FUs and the seabed. As a result,
FUs 50 maintain in a stable state for a long time after installation. Further, since the top surface of set smaller FUs is smoother than that of the seabed, the large FUs are stably located on the small FUs. Thus, flow rate of the tidal current can be effectively reduced. - Further, installing the
FUs 50 around theseabed 200 having thepiles 12 b driven therein increases the lateral pressure applied to the underground part of eachpile 12 b from the surrounding ground. Thus, a gap is less likely to be formed between eachpile 12 b, and the ground and the bearing layer which surround the underground part of thepile 12 b. This can suppress a moment that is generated near theseabed 200 in eachpile 12 b. Further, since a plurality of FUs installed serves as a part of the foundation, the size of the foundation can be compact. - As described above, since the plurality of
FUs 50 are installed between theseabed 200 and each pile 12 b, a gap is less likely to be formed between eachpile 12 b, and the ground and the bearing layer which surround the underground part of thepile 12 b. This can suppress a moment that is generated near theseabed 200 in thepile 12 b, and can prevent scouring that occurs around eachpile 12 b. As a result, the bearing force and the durability of the foundation having thepiles 12 b as a base can be improved. - A method for constructing a foundation for a wind power generation system according to the present embodiment will be described below.
FIGS. 4A through 4F are diagrams sequentially illustrating construction of the foundation for the wind power generation system. First, at a location where the wind power generation system is to be installed, the condition of theseabed 200 and the condition of the tidal currents near theseabed 200 are investigated in advance to examine the size of the FUs, the number of FUs 50 and the position where theFUs 50 are to be installed (FIG. 4A ). Next, based on the investigation result, thepiles 12 b as a base of the foundation are provided so as to be supported by the bearing layer (FIG. 4B ). Then, as described above, a plurality ofFUs 50 are installed in close contact with each other between theseabed 200 and each pile 12 b (FIG. 4C ). At this time, a flat surface is formed by the plurality ofFUs 50 according to the height of the heads of thepiles 12 b. Then, a formwork 12 e for thebase slab portion 12 a is installed on the upper ends of thepiles 12 b (FIG. 4D ). At this time, the bottom surface of the formwork 12 e and the upper ends of thepiles 12 b are fixed to each other. Then, concrete is placed in the formwork 12 e to form thebase slab portion 12 a (FIG. 4E ). Then, thetower 11 is fixed to the upper end of thebase slab portion 12 a (FIG. 4F ). - According to the above method, the
piles 12 b are provided so as to be supported by the bearing layer, the plurality ofFUs 50 are installed between theseabed 200 and each pile 12 b, and thebase slab portion 12 a is provided on the upper ends of thepiles 12 b. This prevents scouring from occurring for a long time, since influence of the tidal current is decreased around the foundation on the sea bed and protect theseabed 200 near thepiles 12 b. In addition, this increases the lateral pressure that is applied to the underground part of eachpile 12 b from the surrounding ground. Thus, a gap is less likely to be formed between eachpile 12 b. As a result, both the bearing force and the durability of the foundation are increased. Further, since a plurality of FUs installed serves as a part of the foundation, the size of the foundation can be compact In addition, since the net yarn of the FUs is made of synthetic fiber and FUs are porous, endocrine disrupter and heavy metal will not solve out and it is possible to provide biotope for seaweeds and fish. Further, the foundation can be made compact, since the FUs work as a par of foundation. - Next, the alternate embodiment is described. In this embodiment, as shown
FIG. 5 , a space is provided between the upper portion of the FUs and thebase slab portion 12 a. Since the other portion is the same as above described embodiment, the explanation thereof will not be reiterated. - In this alternate embodiment, similar to the above described embodiment, it is possible to prevent scouring from occurring for a long time, since influence of the tidal current is decreased around the foundation on the
sea bed 200 and to protect theseabed 200 near thepiles 12 b. In addition, since the lateral pressure is increased that is applied to the underground part of eachpile 12 b from the surrounding ground, a gap is less likely to be formed between eachpile 12 b. - Next, further alternate embodiment is described. In this embodiment the FUs are installed in a foundation of an existing wind power generation system.
FIGS. 6A and 6B are diagrams showing this embodiment.FIG. 6A shows an existing wind power generation system to which this embodiment is applied. As shown inFIG. 6A , space is formed between thefoundation surrounding seabed 200.FIG. 6B shows a state where a plurality ofFUs 50 are installed between the piles, serving as the base of the foundation and theseabed 200. In this embodiment, similar to the above embodiment, scouring can be prevented from occurring for a long time, since influence of the tidal current is decreased around the foundation on the sea bed and protect theseabed 200 near thepiles 12 b. In addition, this increases the lateral pressure that is applied to the underground part of eachpile 12 b from the surrounding ground. Thus, a gap is less likely to be formed between eachpile 12 b. In this embodiment, the FUs are installed around the deformed concave portion of the seabed which might be formed by scouring, for example. The present invention may be applied to the seabed which is not deformed. - In this alternate embodiment, the same meritorious effect is brought about as described above.
- In the first embodiment, an example is described in which one type of FUs are installed. However, the present invention is not limited to this, and two kinds of FUs, one is a large FU and the other is a small FU, may be used. In this case, large FUs and small FUs are installed overlapped. In addition, when FUs are installed in three layers, at first small FUs are installed in one layer at the bottom, and then, two layers of large FUs are installed on the small FUs as described above. Thus, in addition to the effect described in
FIG. 3 , effects are obtained that FUs remain stably longer period and rate of tidal current can be effectively reduced. - A plurality of FUs may be installed in which different kinds of block objects are placed. For example, at first a first FUs including block objects having small size, and then a second FUs including block objects having large size. Thus, the first FUs prevents earth and sand from being sucked out from the seabed surface, follow the unevenness of the seabed. Further, engagement between the plurality of
FUs 50 are improved and FUs remain stably for a long time due to the fact that the plurality ofFUs 50 closely contact each other and are fixed together with no gap formed therebetween. In addition, since the second FUs having large sized block objects faces the tidal current, FUs are located stably and decrease current speed of the tidal current effectively. - In addition, since “the size of FUs” has nothing to do with “the grain size of the block object filled in the FUs”, a synergetic effect is brought about by the large FUs including block objects having large size compared with the effect brought about by large FUs including small sized block objects, and small FUs including large sized block objects. For example, the large FUs including large sized block objects more stably maintain themselves than the small FUs including large sized block objects and the large FUs including small sized block objects.
- Note that the above embodiment is described with respect to an example in which the
base slab portion 12 a is formed by providing the formwork 12 e for thebase slab portion 12 a on the upper ends of thepiles 12 b, and placing concrete into the formwork 12 e. However, the present invention is not limited to this, and a concretebase slab portion 12 a, which has been fabricated in advance, may be provided on the upper ends of thepiles 12 b. - In addition, although the steel pile is used in this embodiment, the concrete pile may be used.
- The second embodiment will be described below. In the second embodiment, a wind power generation system is supported by a foundation having a caisson as a base.
FIG. 7 is a cross-sectional view showing a wind power generation system, a tower, and a foundation to which a method for constructing a foundation for a wind power generation system according to the present embodiment is applied.FIG. 7 shows an offshore windpower generation system 10, atower 11, abase slab portion 12 a, acaisson 12 c, a plurality ofFUs 50, and apower transmission cable 20. Thetower 11 retains the offshore windpower generation system 10, and extends down to a level near theseabed 200 through thesea surface 100. Thebase slab portion 12 a, which is made of concrete, is fixed to thetower 11 by anchor bolts, and supports thetower 11. Thecaisson 12 c, which is made of concrete, is fixed in the excavatedseabed 200, and supports thebase slab portion 12 a on its upper end. The plurality ofFUs 50 are installed between theseabed 200 and thecaisson 12 c. Thepower transmission cable 20 is extended outward from thetower 11 near theseabed 200 to transmit the electricity, generated by the windpower generation system 10, to a land-based ground system (not shown). Note that the foundation in the present embodiment includes thebase slab portion 12 a and thecaisson 12 c, and thecaisson 12 c is formed by placing concrete into a formwork. TheFUs 50 used in the present embodiment are similar to those of the above embodiment. - A method for constructing a foundation for a wind power generation system according to the second embodiment will be described below.
FIGS. 8A through 8H are diagrams sequentially illustrating construction of the foundation for the wind power generation system.FIG. 8I is a diagram viewed from position VIII I-VIII I inFIG. 8E . First, at a location where the wind power generation system is to be installed, the condition of theseabed 200 and the condition of the tidal currents near theseabed 200 are investigated in advance to examine the size and the number of FUs 50 and the position where theFUs 50 are to be installed (FIG. 8A ). Next, based on the investigation result, theseabed 200 is excavated to the depth at which thecaisson 12 c, which is a base of the foundation, is fixed by theseabed 200, thereby forming ahole 13 for installing theformwork 12 d for thecaisson 12 c therein (FIG. 6B ). At this time, an open cut method (open cut mining) may be used. The size of the drilledhole 13 is large enough to support the windpower generation system 10, thetower 11, thebase slab 12 a and thecaisson 12 c to be provided therein. Then, a plurality ofFUs 50 are installed flat on the bottom surface of the drilled hole 13 (FIG. 8C ). At this time, it is preferable that the small FUs are installed. By this, thesmall FUs 50 follow unevenness of the seabed and gaps to be formed between a plurality of FUs can be made small. As a result, when thecaisson 12 c, thebase slab portion 12 a, and the like are installed above theFUs 50, a plurality of FUs, thecaisson 12 c, thebase slab portion 12 a can maintain their locations stable. In addition, when a gap formed between FUs is large, the gap can be reduced by using large FUs or by using both large FUs and small FUs. In addition, there is no limitation as to the number of layers of FUs to be stacked. The more the number of layers, the more effect is obtained that earth and sand are prevented from being sucked out from the seabed surface and that thecaisson 12 c and thebase slab portion 12 a can maintain their stable state. - Then, the
formwork 12 d for forming thecaisson 12 c is installed on the FUs 50 installed on the bottom surface of the hole 13 (FIG. 8D ). Note that theformwork 12 d can be regarded as a part of thecaisson 12 c described below. Then, a plurality ofFUs 50 are installed in close contact with each other so as to fill the gap between theseabed 200 and theformwork 12 d for thecaisson 12 c as a base, that is, between theformwork 12 d for thecaisson 12 c and the drilled hole 13 (FIG. 8E ). At this time, it is preferable that the FUs 50 in the lowermost layer be arranged in two to five columns in the radial direction in a range of width L from the outer circumferential edge of the drilled hole 13 (a portion of a circle P4 other than a circle P3 inFIG. 8I ). It is preferable that L is approximately 6 m. It is also preferable to install the plurality ofFUs 50 so that theFUs 50 having an overall thickness of three layers closely contact the circumference of theformwork 12 d for thecaisson 12 c. Then, concrete is placed into theformwork 12 d to form thecaisson 12 c (FIG. 8F ). Then, the bottom surface of a formwork for thebase slab portion 12 a is fixed to the upper end of thecaisson 12 c by anchor bolts, and concrete is placed into the formwork for thebase slab portion 12 a to form thebase slab portion 12 a (FIG. 8G ). Then, thetower 11 is fixed to thebase slab portion 12 a (FIG. 8H ). - According to the above method, the
seabed 200 is first excavated so that thecaisson 12 c can be supported therein. Then, the plurality ofFUs 50 are installed flat on the bottom surface of the drilledhole 13. Theformwork 12 d for thecaisson 12 c is installed, and the plurality ofFUs 50 are installed between theseabed 200 and theformwork 12 d for thecaisson 12 c. Concrete is then placed into theformwork 12 d to form thecaisson 12 c, and thebase slab portion 12 a is provided on the upper end of thecaisson 12 c. Since influence of the tidal current is decreased near the foundation on theseabed 200, scouring can be suppressed for a long time and theseabed 200 near thecaisson 12 c can be protected. As a result, the bearing force and the durability of the foundation can be improved. Further, since installed FUs serve as a part of the foundation, the foundation can be compact. In addition, since the net yarn of the FUs is made of synthetic fiber and FUs are porous, endocrine disrupter and heavy metal will not solve out and it is possible to provide biotope for seaweeds and fish. - Next, an alternate embodiment is described. In this embodiment the FUs are installed in a foundation using the caisson of an existing wind power generation system.
FIGS. 8J and 8K are diagrams showing this embodiment.FIG. 8J shows an existing wind power generation system to which this embodiment is applied. As shown inFIG. 8J , space is formed between thefoundation surrounding seabed 200.FIG. 8K shows a state where a plurality ofFUs 50 are installed between thecaisson 12 c, serving as the base of the foundation and theseabed 200. Since the other portion of constructing the foundation is the same as above described embodiment, the explanation thereof will not be reiterated. In this embodiment, the FUs are installed around the deformed concave portion of the seabed which might be formed by scouring, for example. The present invention may be applied to the seabed which is not deformed. - In this alternate embodiment, the same meritorious effect is brought about as described above.
- Note that the above embodiment is described with respect to an example in which the
caisson 12 c is formed by placing concrete, and then, the formwork for forming the base slab portion is installed thereon. However, the present invention may use a formwork capable of forming both the caisson and the base slab portion by placing concrete therein. - Note that the above embodiment is described with respect to an example in which the
caisson 12 c is formed by installing theformwork 12 d onto the FUs installed on the bottom surface of the drilledhole 13, and placing concrete into the installedformwork 12 d. However, thecaisson 12 c, which has been fabricated in advance, may be installed onto theFUs 50 installed on the bottom surface of the drilledhole 13. - Note that the above embodiment is described with respect to an example in which one type of FUs are installed. However, the present invention is not limited to this, and two kinds of FUs, one is a large FU and the other is a small FU, may be used. For example, in the case where it is necessary to follow unevenness of the seabed, small FUs are preferably used. On the other hand, when it is necessary to prevent reduce speed of the tidal current, large FUs are used. In addition, a plurality of FUs including different kinds of block objects depending on the conditions required. Thus, the similar effect is brought about as described in the first embodiment.
- The third embodiment will be described below with respect to an installation method of the FUs. A method for protecting a submarine cable for a wind power generation system will be described in the present embodiment.
FIGS. 9A through 9C are diagrams sequentially illustrating the method for protecting a submarine cable for a wind power generation system,FIG. 9D is a diagram viewed from line IX D-IX D inFIG. 9C andFIG. 10 is a diagram showing conditions when a FU is installed. Note thatFUs 50 used in the present embodiment are similar to those of the above embodiment. - First, at a location where the
submarine cable 20 is to be installed, the condition of theseabed 200 and the condition of the tidal currents near theseabed 200 are investigated in advance to examine the size and the number of FUs 50 and the position where theFUs 50 are to be installed (FIG. 9A ). Next, thesubmarine cable 20 is installed on the seabed 200 (FIG. 9B ). Then, anFU 50 is installed so as to cover thesubmarine cable 20 installed on the seabed 200 (FIG. 9C ). - At this time, with reference to
FIG. 10 , conditions required are explained.FIG. 10 is a diagram showing the cross section perpendicular to the direction which the submarines cable elongates. More specifically, assuming the center point of the cable section is Q and its radius is r (m), the point above the cable which is located at the distance D1 (m) from the top surface of thecable 20 is T1, the points which is located at the distance D2 (m) from the side surface of thecable 20 are T2 and T3, and equal two lower angles formed by a isosceles triangle made by points T1, T2 and T3 are θ. In addition, when block objects placed in the FUs are fallen from upper position to the ground, a conical shaped mountain is naturally formed by the block object. It is assumed that the angle is defined as φ formed by the inclined side of the mountain and the ground. It is preferable that the FU cover the hatched isosceles triangle shown inFIG. 10 in which D1≧0.5 m, D2≧1.0 m, and θ≦φ. At this time, normally φ is 45 degrees or less. It is preferable that θ is 30 degrees or less. InFIG. 10 , the dotted line shows the cross section of the FU satisfying the above described conditions. - Since the submarine cable is fully covered by the FU stably, the
submarine cable 20 is fixed so as not to move by the influence of the tidal currents around it (seeFIG. 9D ), and can be protected from, e.g., anchors of ships, rolling stones carried by the tidal currents, and the like. - According to the above method, the
FUs 50 are installed so as to cover thesubmarine cable 20. Thus, thesubmarine cable 20 is fixed by theseabed 200 and theFUs 50, and can be prevented from moving by the influence of the tidal currents around it and the like. This can prevent generation of friction between theseabed 200 and thesubmarine cable 20, and can prevent scouring near the installedsubmarine cable 20 for a long time. As a result, thesubmarine cable 20 can be protected for a long time. - Note that the above embodiment is described with respect to an example in which a submarine cable is newly installed. However, the
FU 50 may be installed so as to cover an existing submarine cable. - Note that the above embodiment is described with respect to an example in which one
FU 50 is installed. However, it is more preferable to install a plurality ofFUs 50. The use of the plurality ofFUs 50 increases the weight for fixing thesubmarine cable 20, enabling thesubmarine cable 20 to be fixed firmly. In addition, as described in the first embodiment, the group effect is obtained and the cable can be fixed stably by installing a plurality of FUs. - Next, some of examples in which the
submarine cable 20 is fixed by a plurality ofFUs 50 will be described below.FIG. 11A shows an example in which a plurality ofFUs 50 are continuously arranged in line in the direction in which thesubmarine cable 20 extends (hereinafter referred to as the “extending direction of thesubmarine cable 20”), andFIG. 11B is a diagram viewed from XI B-XI B inFIG. 11A .FIG. 11A shows only a part of installed FUs.FIG. 12A shows an example in which twoFUs 50 are arranged side by side with thesubmarine cable 20 interposed therebetween, andFIG. 12B is a diagram viewed from position XII B-XII B inFIG. 12A . Note that, in this case as well, a plurality ofFUs 50 may be continuously arranged in two lines along the extending direction of thesubmarine cable 20.FIG. 13A shows an example in which thesubmarine cable 20 is fixed by using a multiplicity ofFUs 50, andFIG. 13B is a diagram viewed from position XIII B-XIII B inFIG. 13A . In any case, theFUs 50 are installed so as to cover thesubmarine cable 20, whereby thesubmarine cable 20 is fixed by theseabed 200 and theFUs 50, and can be prevented from moving by the influence of the tidal currents around it. This can prevent generation of friction between theseabed 200 and thesubmarine cable 20, and can also prevent scouring near the installedsubmarine cable 20 for a long time. As a result, thesubmarine cable 20 can be protected for a long time. In the above embodiment, a plurality of FUs are continuously arranged. It is possible to install continually a plurality FUs in an extending direction of thesubmarine cable 20. For example, by installing continually a plurality FUs at the position where thecable 20 is likely to be moved by the tidal current, it is possible to minimize quantity of work and amount of FUs to be used. - Note that, in the above embodiment, even if scouring occurs around the
FUs 50 provided to protect thesubmarine cable 20, theFUs 50 follow thedeformed seabed 200, and thus, repairs can be made by, e.g., merely providing theFUs 50 over the recessed portion of theseabed 200 by the amount corresponding to the amount of the recess. Thus, repairs can be easily made at low cost. - Note that it is preferable that the method for protecting a submarine cable for a wind power generation system according to the above embodiment be applied to the case where the water depth to the
seabed 200 is about 3 m or more. - Note that the above embodiment is described with respect to an example in which a submarine cable is protected by covering the cable with FUs. At this point, the submarine cable includes ones of telephone lines, the optical fibers and so on. This method can be applied to the cases where the submarine long objects such as long tubes and pipelines for the gas, the oil and so on.
- Next, the fourth embodiment will be described below with respect to the installation method of the FUs. In the fourth embodiment, a method for planarizing an uneven surface of the seabed will be described in this embodiment. Basically, one sized FUs are used to planarize uneven surfaces. In the following an embodiment is described wherein two kinds of FUs whose sizes are different.
-
FIGS. 14A through 14C are diagrams sequentially illustrating the method for planarizing an uneven surface of the seabed. The large FUs and the small FUs described in the first embodiment are used. It is herein assumed that it has been determined based on the investigation that these FUs are suitable for planarization in this embodiment. The block objects placed in the large and small FUs are those having diameter of 50-300 m and specific weight of 2.65. As to other points, there is no difference between the large and small FUs. - First, the condition of an
uneven surface 1000 of theseabed 200 is investigated in advance to examine the respective numbers of large FUs 51 andsmall FUs 52 to be used, and the position where the large FUs 51 and thesmall FUs 52 are to be installed (FIG. 14A ). Then, based on the investigation result, thesmall FUs 52 are installed on the bottom of the recess of the uneven surface 1000 (FIG. 14B ). At this time, it is preferable to install thesmall FUs 52 so that the upper surface formed by thesmall FUs 52 becomes as flat as possible. Then, thelarge FUs 51 are installed on the upper surface formed by thesmall FUs 52, and are leveled so that the upper surface formed by thesmall FUs 52 becomes flush with the seabed 200 (FIG. 14C ). Based on the description of the above embodiments, using a plurality of different types of FUs, such as the large FUs 51 and thesmall FUs 52, improves engagement between the plurality of different types of FUs, and the plurality of different types of FUs closely contact each other. Thus, the different types of FUs are integrated firmly, increasing the stability of the large FUs 51 and thesmall FUs 52 installed in the recess of theuneven surface 1000. Thus, the influence of the tidal currents can be reduced. Moreover, thelarge FUs 51 are installed so that the upper surface formed by thelarge FUs 51 becomes as flush with theseabed 200 around the recess of theuneven surface 1000 as possible. - It is preferable to install the FUs in ascending order of weight. In this case, the
large FUs 51 are installed on the upper surface formed by thesmall FUs 52. Thus, the small FUs follow the bottom of theuneven surface 1000 and it is possible to make the upper surface of the small FUs flat. In addition, by the large FUs installed on the flat small FUs, the whole FUs can be stable. - In this embodiment, since the small FUs are installed on the bottom surface of the
uneven surface 1000, the large FUs are installed on the small FUs and the top surface of the installed large FUs are leveled so that the upper surface formed by thesmall FUs 52 becomes flush with theseabed 200. Thus, the large FUs 51 and thesmall FUs 52 engage with each other, whereby a highly integrated, substantiallyflat seabed 200 having no gap between the FUs can be formed. As a result, the uneven surface can be turned into a substantially flat, firm seabed. - Note that the above embodiment is described with respect to an example in which the concave uneven surface is leveled. However, the present invention is not limited to this, and this method can be applied to an example in which the convex uneven surface is leveled.
FIG. 15 is a diagram showing this example. With reference toFIG. 15 , in this method, at first, thesmall FUs 52 are installed around the convex uneven surface similar to the above embodiment. Then alarge FUs 51 are installed on thesmall FUs 52. After the large FUs are installed, the top surface of the installed large FUs are leveled so that the upper surface formed by thesmall FUs 52 becomes flush with theseabed 200. As a result, it is possible to planarize the convex uneven surface against the seabed. - Note that the above embodiment is described with respect to an example in which two types of FUs, which are the large FUs 51 and the
small FUs 52. However, the present invention is not limited to this, and only one type of FUs may be used. That is, theuneven surface 1000 may be plarnized by leveling one type of FUs so that the upper surface formed by the FUs becomes flush with theseabed 200. A plurality of types of FUs, containing different types of block objects from each other, may be used to planarize theuneven surface 1000. For example, FUs containing block objects having 100 mm diameter and FUs containing block objects having 200 mm diameter are used. In this case, FUs containing block objects having small diameter prevents earth and sand from being sucked out from the seabed surface and follow the unevenness of the seabed. Further, two kinds of FUs having different sized block objects, engage with each other, and can be integrated with no gap therebetween. It is preferable to install the FUs in ascending order of the grain size of the block objects. In this case, since the FUs with small grain size follow the shape ofuneven surfaces 1000 and it is possible to form a flat surface on the upper surface of the small FUs and the whole FUs are stably installed since the large FUs are installed on the flat surface of the small FUs. - The method for planarizing the uneven surface of the seabed according to the above embodiment may be applied together with, e.g., a barge vessel for dumping crushed stones. In this case, the
uneven surface 1000 of theseabed 200 may be planarized as follow. First, crushed stones are dumped from the barge vessel to the bottom of the recess of the uneven surface. After a desired amount of crushed stones is dumped, the large FUs 51 and thesmall FUs 51, for example, are installed as described in the above embodiment by using the method for planarizing the uneven surface of the seabed. This enables the uneven surface to be efficiently planarized at low cost. - Note that the above embodiment is described with respect to an example in which the
uneven surface 1000 is planarized. After the uneven surface is planarized, a submarine cable for a wind power generation system may be installed so as to extend on the planarized uneven surface, or an underwater structure may be installed on the planarized uneven surface. As described in the above embodiment, the submarine cable may be fixed and protected by using the FUs. - Note that, in the above described first to fourth embodiments, the position where the
FUs 50 are to be installed may be located by a global positioning system (GPS). For example, a work ship for installing theFUs 50 on theseabed 200, and a tow body for submerging to investigate the condition under the sea according to signals received from the work ship are applied to the above embodiment. The tow body includes: a bathymetric sonar for radiating sound waves in a fan-shaped radiation pattern to the seabed, and receiving reflected waves from the seabed to measure the depth to the seabed; an oscillation sensor for measuring and correcting the tilt of the bathymetric sonar associated with oscillation of the tow body; a water pressure sensor for measuring an accurate water pressure to keep track of a change in water depth of the tow body; and a transponder for calculating the distance to the work ship and the azimuth of the tow body. The work ship includes: an operation apparatus for operating the tow body; a GPS positioning apparatus for keeping track of the position of the work ship; and a GPS azimuth sensor for keeping track of the azimuth of the work ship; an undersea positioning system for receiving sound waves from the transponder of the tow body, and measuring the position of the tow body; dedicated software for analyzing data obtained from the tow body, based on the respective positions of the tow body and the work ship; and a tow winch connected to the tow body and the cable, for controlling movement of the tow body. First, the operation apparatus in the work ship is operated to submerge the tow body under the sea. The submerged tow body obtains data regarding the condition of the seabed by using the bathymetric sonar, while transmitting its own position and condition to the work ship by the oscillation sensor, the water pressure sensor, and the transponder. The obtained data regarding the seabed is transmitted to the work ship to keep track of the condition of the seabed by the dedicated software of the work ship. The position where the FUs are to be installed is located by the obtained data from the tow body, the GPS positioning apparatus, and the GPS azimuth sensor. This enables the FUs are to be accurately installed at a desired position. For example, the position where the FUs are to be installed may be located and recorded by the GPS positioning apparatus in the investigation that is conducted in advance, and the FUs may be installed based on the recorded data. - Note that, in the above described first to fourth embodiments, the
FUs 50 may be installed by suspending eachFU 50 by a crane or the like. In this case, theFUs 50 may be installed by automatically releasing theconnection portion 504 of eachFU 50 from the crane when theFU 50 is moved to a predetermined installation position. This reduces, e.g., labor and danger of divers who give instructions and assist in working on the seabed, in the operation of releasing eachFU 50 from the crane. - Note that, in the above described first to fourth embodiments, the plurality of installed FUs may be connected by connection members such as a rope, a chain, or the like. This enables the stability between the plurality of
FUs 50 to be maintained for a long time, whereby the bearing force and durability of the foundation can further be improved. - Note that, in the above described first to fourth embodiments, the
FUs 50 may be installed one by one, or more than one FUs 50 may be installed simultaneously. - Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiments within a scope that is the same as, or equivalent to, the present invention.
Claims (9)
1. A method for planarizing unevenness which is an uneven surface of a seabed, comprising the steps of
installing a plurality of bag-shaped filter units, each containing predetermined block objects, on said unevenness; and
leveling said plurality of installed filter units so that an upper surface formed by said plurality of installed filter units becomes flush with said seabed.
2. The method according to claim 1 , wherein
said step of installing said plurality of filter units includes the step of locating a position where said filter units are to be installed, by using a GPS.
3. The method according to claim 1 , wherein
said filter units include a first filter unit having a first size and a second filter unit having a second size larger than said first size, and;
said step of installing said plurality of filter units includes the step of placing said second filter unit on said first filter unit.
4. The method according to claim 1 , wherein
said filter units have a predetermined size and;
said step of installing said plurality of filter units includes the step of placing crushed stones on said unevenness before placing said filter units with the predetermined size.
5. The method according to claim 1 , wherein
said filter units have a predetermined outer size and include a first filter unit having a first block objects with a first size and a second filter unit having a second block objects with a second size larger than said first size and;
said step of installing said plurality of filter units includes the step of placing said second filter unit on said first filter unit.
6. The method according to claim 1 , wherein
said step of installing said plurality of filter units includes the step of placing crushed stones at the bottom of said unevenness before placing a plurality of said filter units.
7. The method according to claim 1 , wherein
the volume of said filter units is equal or smaller than the volume of said unevenness.
8. The method according to claim 1 , wherein
said filter unit includes a bag body and block objects, and;
when said filter unit is hung up, assuming that the height of said bag body from the closed portion to the bottom is H1 and the height of a space without said block objects is H2, the amount of block objects obtained by (H2/H1)×100 is 25-80%.
9. The method according to claim 8 , wherein
the porosity of the knitted fabric of said bag body is 45% to 90%.
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US13/753,942 US8657529B2 (en) | 2009-12-29 | 2013-01-30 | Method for planarizing unevenness of the seabed |
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EP09180856.8A EP2348215B1 (en) | 2009-12-29 | 2009-12-29 | Method for planarizing unevenness of the seabed |
EP09180856.8 | 2009-12-29 |
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US13/753,942 Continuation US8657529B2 (en) | 2009-12-29 | 2013-01-30 | Method for planarizing unevenness of the seabed |
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US20110158753A1 true US20110158753A1 (en) | 2011-06-30 |
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US13/753,942 Active US8657529B2 (en) | 2009-12-29 | 2013-01-30 | Method for planarizing unevenness of the seabed |
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US13/753,942 Active US8657529B2 (en) | 2009-12-29 | 2013-01-30 | Method for planarizing unevenness of the seabed |
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US (2) | US20110158753A1 (en) |
EP (1) | EP2348215B1 (en) |
JP (1) | JP5315567B2 (en) |
DK (1) | DK2348215T3 (en) |
ES (1) | ES2427192T3 (en) |
PL (1) | PL2348215T3 (en) |
PT (1) | PT2348215E (en) |
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CN103382919A (en) * | 2012-05-02 | 2013-11-06 | 韩国海洋科学技术院 | Scouring control cover of seaborne wind power foundation |
CN103898913A (en) * | 2014-03-20 | 2014-07-02 | 河海大学 | Inner geotextile bag sleeve valve pipe grouting construction method |
US20150136670A1 (en) * | 2013-05-06 | 2015-05-21 | Seatower As | Gravity-based structure |
US20150325987A1 (en) * | 2014-05-12 | 2015-11-12 | Gwave Llc | Submarine Cable System |
US9944353B2 (en) | 2012-06-04 | 2018-04-17 | Gwave Llc | System for producing energy through the action of waves |
US9976535B2 (en) | 2005-11-07 | 2018-05-22 | Gwave Llc | System for producing energy through the action of waves |
US20190177942A1 (en) * | 2016-08-02 | 2019-06-13 | Esteyco Sap | System for installing anti-scouring material in a self-floating marine foundation, and associated methods and uses of said system |
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US11332902B2 (en) * | 2018-02-09 | 2022-05-17 | Sumitomo Corporation | Scour prevention unit and scour prevention method |
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- 2009-12-29 PT PT91808568T patent/PT2348215E/en unknown
- 2009-12-29 DK DK09180856.8T patent/DK2348215T3/en active
- 2009-12-29 EP EP09180856.8A patent/EP2348215B1/en active Active
- 2009-12-29 PL PL09180856T patent/PL2348215T3/en unknown
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2010
- 2010-12-24 JP JP2010287432A patent/JP5315567B2/en active Active
- 2010-12-28 US US12/979,602 patent/US20110158753A1/en not_active Abandoned
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CN103382919A (en) * | 2012-05-02 | 2013-11-06 | 韩国海洋科学技术院 | Scouring control cover of seaborne wind power foundation |
US9944353B2 (en) | 2012-06-04 | 2018-04-17 | Gwave Llc | System for producing energy through the action of waves |
US11313098B2 (en) * | 2013-05-06 | 2022-04-26 | Seatower As | Gravity-based structure |
US20150136670A1 (en) * | 2013-05-06 | 2015-05-21 | Seatower As | Gravity-based structure |
CN105308243A (en) * | 2013-05-06 | 2016-02-03 | 海塔有限公司 | A gravity-based structure |
CN103898913A (en) * | 2014-03-20 | 2014-07-02 | 河海大学 | Inner geotextile bag sleeve valve pipe grouting construction method |
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US10683628B2 (en) * | 2016-08-02 | 2020-06-16 | Esteyco S.A. | System for installing anti-scouring material in a self-floating marine foundation, and associated methods and uses of said system |
US20190177942A1 (en) * | 2016-08-02 | 2019-06-13 | Esteyco Sap | System for installing anti-scouring material in a self-floating marine foundation, and associated methods and uses of said system |
US11332902B2 (en) * | 2018-02-09 | 2022-05-17 | Sumitomo Corporation | Scour prevention unit and scour prevention method |
CN110258659A (en) * | 2019-06-19 | 2019-09-20 | 中国石油工程建设有限公司 | Submarine pipeline logs in section compartment soil body anti-liquefying ability lifting device and a method |
JP2021195764A (en) * | 2020-06-11 | 2021-12-27 | キョーワ株式会社 | Filter unit for monopile and scoring prevention method using the same |
Also Published As
Publication number | Publication date |
---|---|
DK2348215T3 (en) | 2013-08-26 |
US20130142574A1 (en) | 2013-06-06 |
PT2348215E (en) | 2013-08-29 |
JP2011137366A (en) | 2011-07-14 |
ES2427192T3 (en) | 2013-10-29 |
EP2348215B1 (en) | 2013-06-12 |
EP2348215A1 (en) | 2011-07-27 |
PL2348215T3 (en) | 2014-01-31 |
US8657529B2 (en) | 2014-02-25 |
JP5315567B2 (en) | 2013-10-16 |
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