JP2020041315A - Scour preventing construction around pile-shaped body, and construction method of scour preventing construction around pile-shaped body - Google Patents

Abstract

To provide a scour preventing construction around a pile-shaped body and a construction method of a scour preventing construction around a pile-shaped body capable of easily managing a top end height without the necessity of shaping and not damaging a foundation structure and an incidental installed object.SOLUTION: A positioning cradle 13 is installed on a water bottom 1 in a peripheral edge portion of an installation position of an asphalt mat 3, and then asphalt mats 3-1-1 and 3-1-2 are lifted down by using a hanging metal fitting 15, to lay them on the water bottom 1. In the same procedure, the remaining asphalt mats 3-2, 3-3,... are sequentially laid on the water bottom 1. The asphalt mat 3 is laid so as to provide an overlapping portion. Then, a foundation pile 9 is inserted into an installation hole 11 formed in a center of the asphalt mat 3, and the foundation pile 9 is installed on the water bottom 1. After that, a ring-shaped rectangular hat 5 is installed so as to cover a gap 12 between the foundation pile 9 and the asphalt mat 3, and a weight 7 is installed on the asphalt mat 3, to complete scour preventing construction 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a scouring prevention work around a pile and a construction method of a scour prevention work around a pile.

  In the past, stone-based structures were generally used to prevent scouring of landing-type offshore wind power generation foundations, and the filter layer dissipated on top of a filter layer with a small particle size to prevent sand suction. There is used a two-layer structure in which an armor layer having a large particle size is provided to prevent the occurrence of a crack.

  There are cables around the foundation, especially in the case of monopile foundations, where the mainstream is to make a hole in the wall of the monopile and draw the cable into the pile. At this time, if the top of the scour prevention work is too high with respect to the cable laying position, rework such as re-digging the armor layer and adjusting the height may occur. Management is required.

Japanese Patent No. 5893408

  However, it takes time and cost to spread the floor and make the top of the scour prevention work to a constant height. In Europe, dedicated stonewagons are used, but the introduction and maintenance of such vessels is very costly.

  Also, when constructing a scour prevention work by placing stones after the foundation is installed, the stones may hit basic structures such as monopiles, transition pieces, jackets, etc., or incidental installations such as anticorrosion electrodes, and damage them. There is a possibility.

  Furthermore, in both the armor layer and the filter layer, when a stormy wave such as a typhoon occurs, the stones move and gradually dissipate due to the action of the waves. Therefore, maintenance such as replenishment and shaping is required. In addition, the escaped stones may damage the above-mentioned substructure and incidental structures.

  Conventional stone scouring prevention works have a certain thickness, and the presence of such scouring prevention works may cause a phenomenon called secondary scouring in which the area around the scour prevention works is scoured.

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to eliminate the need for shaping, to easily manage the height of the top end, and to damage the substructure and incidental installations. An object of the present invention is to provide a method for preventing scouring around a pile and preventing scouring around a pile.

  In order to achieve the above-described object, a first invention is to provide a sheet-like or mat-like water-impermeable covering provided in a predetermined range of a water bottom around a pile-like body, And a weight that is installed and maintains the stability of the covering body against external forces generated by water.

  In the first invention, since the sheet-like or mat-like covering is used, shaping such as leveling work after laying is not required, the height of the top end can be easily controlled, and the construction period can be shortened. In addition, since a water-impermeable coating is used, it is possible to eliminate sand suction. Furthermore, since the thickness of the covering is smaller than that of a normal stone filter layer, it is possible to suppress the occurrence of secondary scouring in the vicinity.

The pile is, for example, an offshore wind foundation pile.
Thereby, scouring around the foundation pile of the offshore wind power of the landing type such as the monopile type or the jacket type can be prevented.

It is preferable that the covering is a flexible mat having a predetermined thickness. The flexible mat is, for example, an asphalt mat.
Thereby, the covering body can be laid so as to follow the unevenness at the bottom of the water.

The weight is, for example, a bag filled with stone or crushed stone.
Thus, the weight can be easily manufactured. Also, material costs can be reduced.

The covering may be divided into strips, and the weight may be provided at a joint portion of the covering.
Further, the cover may be divided into strips, and joint portions of the cover may be tied.
Furthermore, the covering may be divided into strips, and a water-impermeable sheet may be provided between the water bottom surface and the covering so as to close a joint portion of the covering.

  If the covering is divided into strips, it can be easily laid on the water bottom. In addition, if a weight is installed at the seam portion, it is possible to prevent the covering body from being turned up after being laid, and to prevent sand from being sucked out from the seam portion. Tightening the joints can prevent the covering from being rolled up after laying. If the water-impermeable sheet is installed so as to cover the seam portion, it is possible to prevent sand from being sucked out from the seam portion after the seam is laid.

A hole may be provided in an outer peripheral portion of the cover, and a water-permeable sheet may be provided between the water bottom surface and the cover so as to cover the hole.
This allows only water to pass through the water-permeable sheet and holes at the outer peripheral portion of the cover, and does not allow sand to pass, thereby preventing secondary scouring.

It is preferable that a ring-shaped auxiliary covering body having a predetermined weight and rigidity is installed in a range covering a gap between the pile-shaped body and the covering body.
This can prevent sand from being sucked out from the gap between the pile and the covering.

  The second invention comprises a step a of laying a sheet-like or mat-like impervious covering body in a predetermined range of a water bottom, and a step b of piercing the covering body and placing a pile-like body on the water bottom. Installing a weight on the upper surface of the covering body to maintain the stability of the covering body against an external force caused by water. C. The construction method.

  In the second aspect, the cover is laid on the bottom of the water before the installation of the pile, so that the pile and other attached objects are not damaged when the cover is laid. In addition, since a sheet-like or mat-like covering body is used, shaping such as leveling work after laying is not required, the height of the top is easily managed, and the construction period can be shortened. Furthermore, since the impermeable coating is used, it is possible to eliminate sand suction. Since the thickness of the covering is thinner than the conventional stone filter layer, it is possible to suppress the occurrence of secondary scouring in the vicinity.

In the step (a), for example, an installation hole is formed in the covering body so as to penetrate the pile-shaped body.
In this case, after the step b, a step d of installing a ring-shaped auxiliary covering body having a predetermined weight and rigidity in a range covering the gap between the pile-shaped body and the covering body may be further provided. desirable.
If the installation holes are provided, the pile-shaped body can be securely and easily installed at a predetermined position. In addition, if the auxiliary cover is provided, it is possible to prevent sand from being sucked out from the gap between the pile and the cover.

In the step a, a gantry for positioning is installed on a water bottom at a peripheral portion of the installation position of the covering body, and the hanging position of the covering body and the gantry for positioning are brought into contact with each other to determine the installation position of the covering body. It is desirable.
Thereby, the position where the covering body is laid can be easily determined.

  ADVANTAGE OF THE INVENTION According to this invention, shaping is unnecessary, the top height can be easily managed, and the scouring prevention work around the pile-like body and the periphery of the pile-like body which do not damage the foundation structure and the incidental installations can be performed. Can be provided.

Figure showing scour prevention work 2 Figure showing scour prevention work 2 Diagram showing the process of laying asphalt mat 3 The figure which shows the process of installing the foundation pile 9 The figure which shows the process of installing the ring rectangular hat 5 Figure showing scour prevention work 2a Figure showing scour prevention work 2a Diagram showing the process of laying asphalt mat 3a Figure showing another construction method of scour prevention work 2a The figure which shows the example of arrangement | positioning of a water-impermeable sheet Figure showing scour prevention work 2b Figure showing scour prevention work 2c Figure showing asphalt mat 3c Diagram showing construction method of scour prevention work 2d Figure showing scour prevention work 2e

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
1 and 2 are views showing a scour prevention work 2 according to a first embodiment of the present invention. FIG. 1 is a diagram of the scour prevention work 2 viewed from above. FIG. 2A is a cross-sectional view taken along arrow A1-A1 shown in FIG. 1, and FIG. 2B is a cross-sectional view taken along arrow A2-A2 shown in FIG.

  As shown in FIGS. 1 and 2, the scour prevention work 2 includes an asphalt mat 3, a ring rectangular hat 5, a weight 7, and the like. The scour prevention work 2 is constructed, for example, around a foundation pile 9 (pile-shaped body) that is a foundation of offshore wind power.

  The asphalt mat 3 is a covering and is laid in a predetermined range of the water bottom 1 around the foundation pile 9 as shown in FIG. The asphalt mat 3 is a water-impermeable flexible mat and has a thickness of about 30 to 200 mm. The asphalt mat 3 is divided into strip-shaped asphalt mats 3-1-1, 3-1-2, 3-2, 3-3, 3-4, and 3-5. As shown in FIG. 2B, an overlapped portion is provided at a joint portion of the divided asphalt mat 3.

  The ring rectangular hat 5 is an auxiliary covering, and is installed in a range covering the gap 12 between the foundation pile 9 and the asphalt mat 3 as shown in FIG. The ring rectangular hat 5 is impermeable and has a predetermined weight and rigidity. The ring rectangular hat 5 is, for example, a modified asphalt sheet, and is provided with a steel frame (not shown) for maintaining the shape and preventing rolling up after installation. The ring rectangular hat 5 is installed so that the outer peripheral portion overlaps the upper surface of the asphalt mat 3.

  As shown in FIGS. 1 and 2, the weight 7 includes weights 7-1, 7-2, and 7-3, and is installed on the upper surface of the asphalt mat 3. The weight 7-1 is installed at the joint portion so as to press the overlapping portion of the asphalt mat 3 divided into strips. The weight 7-2 is installed so as to straddle the asphalt mat 3 and the ring rectangular hat 5. The weight 7-3 is installed at an outer peripheral portion of the asphalt mat 3 (at a position inside the outer edge of the asphalt mat 3 by about 50 to 100 cm). The weight 7 is, for example, a bag filled with stone or crushed stone. The particle size of the stone to be filled is not limited to a specific range.

  The weight 7 does not move in response to an external force generated by a wave, a tide, or the like, and holds the asphalt mat 3 to maintain stability. The weight 7-1 prevents sand from being sucked out and turned up from the joint portion of the strip-shaped asphalt mat 3. The weight 7-2 prevents the sand from being sucked up or rolled up from the overlapping portion of the asphalt mat 3 and the ring rectangular hat 5, but as described above, the ring rectangular hat 5 has a predetermined weight and rigidity. The installation of the weight 7-2 is not essential. The weight 7-3 prevents the outer periphery of the asphalt mat 3 from being curled up. If the weight 7-3 is arranged along the outer edge of the asphalt mat 3, the height of the outer edge of the scour prevention work 2 may increase and secondary scouring may occur around the scour prevention work 2. In the embodiment, since the weight 7-3 is set apart from the outer edge of the asphalt mat 3, the height of the outer edge of the scour prevention work 2 becomes the thickness of the asphalt mat 3, thereby preventing secondary scouring.

  Next, a construction method of the scour prevention work 2 will be described. FIG. 3 is a diagram illustrating a process of laying the asphalt mat 3. FIGS. 3A and 3B are views of the state where the asphalt mat 3 is laid, as viewed from the side, and FIG. 3C is a view of the state where the asphalt mat 3 is laid, as viewed from above.

  FIG. 4 is a diagram illustrating a process of installing the foundation pile 9. 4A is a cross-sectional view taken along the arrow BB shown in FIG. 4B, and FIG. 4B is a view of the state where the foundation pile 9 is installed as viewed from above.

  FIG. 5 is a diagram illustrating a process of installing the ring rectangular hat 5. 5A is a cross-sectional view taken along the arrow CC shown in FIG. 5B, and FIG. 5B is a view of the state where the ring rectangular hat 5 is installed, as viewed from above.

  In order to construct the scour prevention work 2, first, the gantry 13 for positioning shown in FIG. 3A is installed on the water bottom 1 at the periphery of the installation position of the asphalt mat 3 using a hoist ship or the like. The gantry 13 is installed at an appropriate position by an underwater positioning device (not shown).

  After the gantry 13 is installed, the asphalt mats 3-1-1 and 3-1-2 are suspended in water using the hanging hardware 15 as shown in FIG. To determine the installation position of the asphalt mat 3-1-1 and 3-1-2. Then, the asphalt mats 3-1-1 and 3-1-2 are laid on the water bottom 1.

  The hanging fitting 15 has a shock absorbing material 16 for suppressing a shock at the time of contact with the gantry 13. Further, an underwater camera (not shown) for confirming the installation position may be provided. Further, the hanging fitting 15 may have an auto release mechanism (not shown). If the auto release mechanism is used, the asphalt mat 3 can be removed from the hanging fitting 15 without performing a work by a diver.

  Next, as shown in FIG. 3 (b), the asphalt mat 3-2 is hung down using the hanger 15, and the hanger 15 is brought into contact with the gantry 13 to determine an installation position. The asphalt mat 3-2 is installed at the position shown in FIG. In the same procedure, the asphalt mats 3-3, 3-4, and 3-5 are sequentially installed on the water bottom 1, and the laying of the asphalt mats 3 is completed. An installation hole 11 is formed in the center of the asphalt mat 3.

  After the asphalt mat 3 is laid, the foundation pile 9 is inserted into the installation hole 11 of the asphalt mat 3 as shown in FIG. The foundation pile 9 is installed so as to penetrate the asphalt mat 3. The diameter of the installation hole 11 is larger than the diameter of the foundation pile 9, and a gap 12 is formed between the outer peripheral surface of the foundation pile 9 and the asphalt mat 3.

  After the foundation pile 9 is installed, the ring rectangular hat 5 is installed so as to cover the gap 12 between the foundation pile 9 and the asphalt mat 3 as shown in FIG. Thereafter, as shown in FIGS. 1 and 2, the weight 7 is placed on the asphalt mat 3 to complete the scour prevention work 2.

  As described above, according to the first embodiment, since the asphalt mat 3 is used as the covering, shaping such as leveling work is not required at the time of construction, and the top height can be easily managed. Further, since the asphalt mat 3 has the installation holes 11, the foundation pile 9 can be reliably and easily installed at a predetermined position. Furthermore, since the asphalt mat 3 is laid before the foundation pile 9 is installed, the foundation pile 9 and other attached objects are not damaged at the time of laying.

  In the first embodiment, the flexible asphalt mat 3 can be laid so as to follow the unevenness of the water bottom 1. Moreover, the gap 12 between the foundation pile 9 and the asphalt mat 3 can be reliably covered with the ring rectangular hat 5 as the auxiliary covering. Since the asphalt mat 3 and the ring rectangular hat 5 are impermeable, it is possible to prevent the sand around the foundation pile 9 from being sucked out. Further, since the asphalt mat 3 is thinner than the conventional stone filter layer and is less likely to hinder the flow, it is possible to suppress the occurrence of secondary scouring around the asphalt mat. The asphalt mat 3 is excellent in durability and does not change its shape, so that maintenance is easy.

  In the first embodiment, since the asphalt mat 3 is divided into strips, it can be easily transported to the site, can be stored in a narrow work yard, and can be easily hung by the hanging hardware 15. In addition, by installing the gantry 13 for positioning on the water bottom 1, the hanging metal 15 and the gantry 13 are brought into contact with each other, so that the laying position of the asphalt mat 3 can be easily determined.

  The weight 7 installed on the upper surface of the asphalt mat 3 prevents scouring due to waves or tides, and prevents lifting or rolling up due to the application of lifting pressure to the impermeable asphalt mat 3. By using a bag filled with stone or crushed stone as the weight 7, the weight 7 can be easily manufactured, and the material cost can be reduced.

  In the first embodiment, the weights 7-1, 7-2, and 7-3 are juxtaposed in a row without any gap, but the number of the weights 7 is determined in consideration of the weight of the asphalt mat 3 and the ring rectangular hat 5. May be determined. The weight 7 may be arranged so as to prevent the asphalt mat 3 from rolling up and sucking out sand.

  Hereinafter, another example of the present invention will be described as second to fifth embodiments. Each embodiment will be described with respect to differences from the embodiments described above, and the same components will be denoted by the same reference numerals in the drawings and the like, and description thereof will be omitted. Further, the configurations described in the respective embodiments, including the first embodiment, can be combined as needed.

[Second embodiment]
6 and 7 are views showing a scour prevention work 2a according to the second embodiment of the present invention. Drawing 6 is a figure which looked at scour prevention work 2a from the upper part. 7A is a cross-sectional view taken along the arrow D1-D1 shown in FIG. 6, and FIG. 7B is a cross-sectional view taken along the arrow D2-D2 shown in FIG.

  The scour prevention work 2a shown in FIGS. 6 and 7 includes an asphalt mat 3a, a ring rectangular hat 5, an impermeable sheet 17, and the like. The asphalt mat 3a has a thickness of about 50 to 200 mm and a predetermined weight. The asphalt mat 3a is divided into strip-shaped asphalt mats 3a-1, 3a-2, 3a-3, 3a-4, and 3a-5. As shown in FIG. 7B, at the joint portion of the divided asphalt mat 3a, the asphalt mats 3a are laid so as not to overlap with each other.

  As shown in FIG. 7, the impermeable sheet 17 is provided between the asphalt mat 3a and the water bottom 1. As shown in FIG. 7 (b), the water-impermeable sheet 17 is a water-impermeable sheet 17-1 corresponding to the asphalt mats 3a-1, 3a-2, 3a-3, 3a-4 and 3a-5. , 17-2, 17-3, 17-4, and 17-5. At the joint portion of the divided asphalt mat 3a, the water-impermeable sheet 17 corresponding to at least one asphalt mat 3a extends in the direction of the other asphalt mat 3a and overlaps with the other asphalt mat 3a. As a result, the joint portion of the asphalt mat 3a is closed by the impermeable sheet 17.

  The asphalt mat 3a and the ring-shaped rectangular hat 5 used in the scour prevention work 2a have a sufficient weight to maintain stability against external forces generated by waves, tides, and the like. Therefore, in the scour prevention work 2a, a weight is not set on the upper surface of the asphalt mat 3a, and the joint portion of the strip-shaped asphalt mat 3a, the asphalt mat 3a and the ring rectangular hat are not provided by the weight of the asphalt mat 3a and the ring rectangular hat 5. 5 and the outer edge of the asphalt mat 3a is prevented from being curled up. The water-impermeable sheet 17 prevents the sand from being sucked out from the joint portion of the strip-shaped asphalt mat 3a.

  Next, a construction method of the scour prevention work 2a will be described. FIG. 8 is a diagram illustrating a process of laying the asphalt mat 3a. FIG. 8A is a view of a state where the asphalt mat 3a is laid, as viewed from the side, and FIG. 8B is a view of a state where the asphalt mat 3a is laid, as viewed from above.

  In order to construct the scour prevention work 2a, first, in the same manner as in the first embodiment, the positioning pedestal 13 shown in FIG. After the gantry 13 is installed, the water-impermeable sheet 17-1 is hung down using the hanging hardware 15 shown in FIG. Then, as shown in FIG. 8A, the asphalt mat 3 a-1 is hung down in water using the hanger 15 and laid on the water bottom 1.

  Thereafter, the water-impermeable sheet 17-2 and the asphalt mat 3a-2, the water-impermeable sheet 17-3 and the asphalt mat 3a-3,... Are sequentially installed on the water bottom 1 in the same procedure, and the asphalt mat 3a is laid. I do. The laying position of the impermeable sheet 17 and the asphalt mat 3a is determined by bringing the hanging bracket 15 and the gantry 13 into contact.

  As shown in FIG. 8B, the installation position of the foundation pile 9 is indicated by the marking 11a on the asphalt mat 3a. After laying the asphalt mat 3a, the asphalt mat 3a is punched out with the foundation pile 9 using the marking 11a as a mark, and the foundation pile 9 is placed on the water bottom 1 by penetrating the asphalt mat 3a as shown in FIG.

  After the foundation pile 9 is installed, as shown in FIG. 7A, the ring rectangular hat 5 is installed in a range covering the periphery of the foundation pile 9 to complete the scour prevention work 2a.

  Also in the second embodiment, the same effect as that of the first embodiment can be obtained by laying the impermeable and flexible asphalt mat 3a as the covering body and then installing the foundation pile 9. Since the asphalt mat 3a and the ring rectangular hat 5 are impermeable, it is possible to prevent the sand around the foundation pile 9 from being sucked out.

  In the second embodiment, since the asphalt mat 3a is punched by the foundation pile 9, a gap is hardly formed between the foundation pile 9 and the asphalt mat 3a. Further, since the weight 7 is not installed on the asphalt mat 3a, the height of the scouring prevention work 2a can be easily controlled, and the cost for manufacturing the weight 7 can be reduced.

  In the second embodiment, an example is shown in which no weight is provided on the asphalt mat 3a, but a weight may be provided. When the gap between the foundation pile 9 and the asphalt mat 3a is small, the ring rectangular hat 5 is not always necessary. In the second embodiment, the asphalt mat 3a divided into strips and the impermeable sheet 17 corresponding thereto are separately laid, but the construction method is not limited to this. FIG. 9: is a figure which shows another construction method of the scour prevention work 2a. As shown in FIG. 9, the water-impermeable sheet 17-1 corresponding to the lower surface of the asphalt mat 3a-1 divided into strips may be integrated. In the example shown in FIG. 9, the work of laying the divided asphalt mat 3a and the corresponding impermeable sheet 17 on the water bottom 1 at the same time is repeated to complete the laying of the asphalt mat 3a.

  Further, the arrangement of the impermeable sheet is not limited to the arrangement shown in the second embodiment. FIG. 10 is a diagram illustrating an arrangement example of the water-impermeable sheet. FIG. 10 (a) is a diagram showing a scour preventing work 2a ', and FIG. 10 (b) is a diagram showing a scour preventing work 2a' '.

  In the scour preventing work 2a 'shown in FIG. 10A, the impermeable sheet 17' is laid in a strip shape only near the seam of the asphalt mat 3a divided into strips. In the scour preventing work 2a '' shown in FIG. 10B, one impermeable sheet 17 '' having a size substantially equal to that of the asphalt mat 3a is laid. Also in each example shown in FIG. 10, the water-impermeable sheet prevents the sand from being sucked out from the joint portion of the asphalt mat 3a.

[Third Embodiment]
FIG. 11 is a diagram illustrating a scouring prevention work 2b according to the third embodiment. FIG. 11A is a view of the scour prevention work 2b viewed from above, and FIG. 11B is a cross-sectional view taken along an arrow EE shown in FIG. 11A.

  The scour prevention work 2b shown in FIG. 11 includes an asphalt mat 3b, a ring rectangular hat 5, a binding material 21, and the like. The asphalt mat 3a is divided into strip-shaped asphalt mats 3b-1, 3b-2, 3b-3, 3b-4, and 3b-5. As shown in FIG. 11 (b), the divided asphalt mat 3b is laid such that the asphalt mats 3b abut against each other at the seam portion, and prevents sand from being sucked out from the seam portion between the asphalt mat 3b and the water bottom 1. An impermeable sheet 17 'and the like are laid. Alternatively, as in the case of the asphalt mat 3 of the first embodiment, the seam portion is provided with an overlapping portion. The binding material 21 binds adjacent asphalt mats 3b. As the binding material 21, for example, a fiber belt, an annealed iron wire, a combination of an annealed iron wire and a wire rope, or the like is used. The required number and arrangement of the binding materials 21 are not limited to those shown in FIG. 11, but are determined according to the type of the binding material and the size (weight in water) of the asphalt mat.

  When constructing the scour prevention work 2b, the asphalt mats 3b divided into strips may be laid one by one on the water bottom 1 and then tied with the binding material 21, or the asphalt mats divided into strips may be used. The asphalt mat 3b may be laid on the water bottom 1 after the 3b is tied with the binding material 21 on land.

  After laying the asphalt mat 3b, the foundation pile 9 is installed on the water bottom, and the ring rectangular hat 5 is installed around the foundation pile. The foundation pile 9 may be installed in an installation hole formed in the asphalt mat 3b in advance, or may be installed by punching out the asphalt mat 3b. FIG. 11 shows an example in which no weight is provided on the asphalt mat 3b. However, a weight may be provided as needed.

  Also in the third embodiment, the same effects as in the first embodiment can be obtained by laying the impermeable and flexible asphalt mat 3b as the covering body and then installing the foundation pile 9. Since the asphalt mat 3b and the ring rectangular hat 5 are impermeable, it is possible to prevent the sand around the foundation pile 9 from being sucked out. In the third embodiment, the asphalt mat 3b is tied with the tying material 21, so that the asphalt mat 3b can be prevented from being rolled up from the seam portion.

[Fourth embodiment]
FIG. 12 is a view showing a scour prevention work 2c according to the fourth embodiment of the present invention. FIG. 12A is a view of the scour prevention work 2c as viewed from above, and FIG. 12B is a cross-sectional view taken along an arrow FF shown in FIG. 12A. FIG. 13 is a diagram showing the asphalt mat 3c.

  The scour preventing work 2c shown in FIG. 12 includes an asphalt mat 3c, a ring rectangular hat 5, a weight 7-3, and the like. As shown in FIG. 13, the asphalt mat 3c is not divided into a plurality, and has an installation hole 11c at the center.

  In order to construct the scour prevention work 2c, the asphalt mat 3c is suspended in water and laid on the water bottom 1 as shown in FIG. After the foundation pile 9 is pierced through the installation hole 11c and the foundation pile 9 is placed on the water bottom 1, the ring rectangular hat 5 is placed so as to cover the gap 12 between the foundation pile 9 and the asphalt mat 3c. Thereafter, the weight 7-3 is set on the asphalt mat 3c.

  Also in the fourth embodiment, the same effects as in the first embodiment can be obtained by laying the impermeable and flexible asphalt mat 3b as the covering body and then installing the foundation pile 9. Since the asphalt mat 3c and the ring rectangular hat 5 are impermeable, it is possible to prevent the sand around the foundation pile 9 from being sucked out.

  In the fourth embodiment, since the asphalt mat 3c has no joint, the weight 7-1 can be omitted. Further, since the ring rectangular hat 5 has a sufficient weight, the weight 7-2 can be omitted. In the fourth embodiment, since the number of the weights 7 is smaller than that in the first embodiment, the height of the scouring prevention work 2c can be easily managed, and the cost for manufacturing the weight 7 can be reduced.

[Fifth Embodiment]
FIG. 14 is a diagram illustrating a construction method of a scour prevention work 2d according to the fifth embodiment of the present invention. FIG. 14A is a view of the scour prevention work 2d as viewed from above, and FIG. 14B is a cross-sectional view taken along an arrow GG shown in FIG. 14A.

  The scour prevention work 2d shown in FIG. 14 includes an asphalt mat 3d, a ring rectangular hat 5, a weight 7-3, a water-permeable sheet 23, and the like. In the asphalt mat 3d, holes 19 are provided at predetermined intervals on the outer peripheral portion as shown in FIG. 14A, and installation holes 11d are provided in the central portion as shown in FIG. 14B. The water permeable sheet 23 is, for example, a nonwoven fabric. The water-permeable sheet 23 is provided between the asphalt mat 3d and the water bottom 1. The water permeable sheet 23 is arranged so as to close the holes 19.

  In order to construct the scour prevention work 2d, the water-permeable sheet 23 and the asphalt mat 3d are suspended in the water in order and laid on the water bottom 1 as shown in FIG. Alternatively, the asphalt mat 3 d to which the water permeable sheet 23 is attached is suspended in water and laid on the water bottom 1. After the foundation pile 9 is penetrated through the installation hole 11d and the foundation pile 9 is placed on the water bottom 1, the ring rectangular hat 5 is placed so as to cover the gap 12 between the foundation pile 9 and the asphalt mat 3d. Then, the weight 7-3 is set on the asphalt mat 3d.

  Also in the fifth embodiment, the same effects as in the first embodiment can be obtained by laying the impermeable and flexible asphalt mat 3d as the covering body and then installing the foundation pile 9. Since the asphalt mat 3d and the ring rectangular hat 5 are impermeable, it is possible to prevent the sand around the foundation pile 9 from being sucked out. Also in the fifth embodiment, since the asphalt mat 3d has no joint, the number of the weights 7 can be reduced, and the same effect as in the fourth embodiment can be obtained.

  In the scour prevention work 2d of the fifth embodiment, when secondary scouring is likely to occur on the water bottom 1 around the asphalt mat 3d, only water passes through the water-permeable sheet 23 and the holes 19. In the scour prevention work 2d, since the sand on the water bottom 1 does not pass through the water-permeable sheet 23, the sand is not sucked out from the holes 19, so that secondary scour can be prevented.

  In the first to fifth embodiments, the rectangular asphalt mat is used as the covering, but the shape of the asphalt mat is not limited to this. FIG. 15 is a diagram showing the scour prevention work 2e. Drawing 15 is a figure which looked at scour prevention work 2e from the upper part.

  As shown in FIG. 15, the asphalt mat 3e of the scour prevention work 2e is octagonal. The asphalt mat 3e is divided into eight substantially trapezoidal portions by a line connecting the corner and the installation range of the foundation pile 9. The weight 7-1 is installed at the joint portion of the divided asphalt mat 3e, and prevents the sand from being sucked out and turned up from the joint portion. The weight 7-3 is installed on the outer peripheral portion of the asphalt mat 3e, and prevents the peripheral portion of the asphalt mat 3e from rolling up.

  In the first to fifth embodiments, the offshore wind foundation pile 9 is shown as a pile, but the pile is not limited to this. Also, the installation holes for installing the piles need not be rectangular. The material of the ring-shaped auxiliary covering body is not limited to the modified asphalt sheet, and the shape may be any as long as it can cover the gap around the pile-shaped body.

  The weight 7 need not be a bag filled with stone or crushed stone. The weight 7 may be anything that is easy to manufacture and easy to install in water, and may be, for example, a concrete block or a mortar or the like cast inside a cylindrical bag.

  The coating is not limited to the asphalt mat 3. The covering may be a sheet-like member having a thickness of up to about 30 mm, and for example, a palace sheet (registered trademark) may be used. Also, a concrete mat or the like formed by connecting concrete blocks or the like with a linear material may be used.

  The preferred embodiment according to the present invention has been described with reference to the accompanying drawings, but the present invention is not limited to this example. It is obvious to those skilled in the art that various changes or modifications can be made within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present invention. I understand.

1 ... water bottom 2, 2a, 2a ', 2a'', 2b, 2c, 2d, 2e ... scour prevention work 3, 3-1-1, 3-1-2, 3-2, 3- 3, 3-4, 3-5, 3a, 3a-1, 3a-2, 3a-3, 3a-4, 3a-5, 3b, 3b-1, 3b-2, 3b-3, 3b-4, 3b-5, 3c, 3d, 3e ... asphalt mat 5 ... ring rectangular hat 7, 7-1, 7-2, 7-3 ... weight 9 ... foundation pile 11, 11c, 11d ... ... Installation holes 11a ... Marking 12 ... Gap 13 ... Stand 15 ... Hanging bracket 16 ... Shock absorbers 17, 17-1, 17-2, 17-3, 17-4, 17-5, 17 ', 17''... water-impermeable sheet 19 ... hole 21 ... binding material 23 ... water-permeable sheet

Claims (14)

Sheet-like or mat-like impermeable coverings installed in a predetermined range of the water bottom around the pile,
A weight installed on the upper surface of the cover, which maintains the stability of the cover against external force generated by water,
A scouring prevention work around a pile-shaped body, comprising:   The scouring prevention work around the pile-shaped body according to claim 1, wherein the pile-shaped body is a foundation pile for offshore wind power.   The scouring prevention work around the pile-shaped body according to claim 1 or 2, wherein the covering body is a flexible mat having a predetermined thickness.   The scouring prevention work around the pile-shaped body according to claim 3, wherein the flexible mat is an asphalt mat.   The scouring prevention work around the pile-shaped body according to any one of claims 1 to 4, wherein the weight is a bag filled with stone or crushed stone.   The scouring prevention work around the pile-like body according to any one of claims 1 to 5, wherein the covering body is divided into strips, and the weight is installed at a joint portion of the covering body. .   The scouring prevention work around the pile-shaped body according to any one of claims 1 to 6, wherein the covering is divided into strips, and a joint portion of the covering is tightened.   The said covering body is divided | segmented into strip shape, The water-impermeable sheet is installed between the said water bottom surface and the said covering body so that the joint part of the said covering body may be closed, The Claims characterized by the above-mentioned. 7. A scouring prevention work around the pile-shaped body according to any one of 7.   9. A hole is provided in an outer peripheral portion of the cover, and a water-permeable sheet is provided between the water bottom surface and the cover so as to cover the hole. Scour prevention work around piles described in Crab.   10. A ring-shaped auxiliary covering body having a predetermined weight and rigidity is installed in a range covering a gap between the pile-shaped body and the covering body. Scour prevention work around the pile-shaped body described. A step a of laying a sheet-like or mat-like impermeable coating in a predetermined range of the water bottom surface,
A step b of piercing the covering and placing the pile on the water floor;
A step c of installing a weight on the upper surface of the cover to maintain stability of the cover against an external force generated by water;
Construction method of scour prevention work around pile-shaped body, characterized by comprising:   The construction method according to claim 11, wherein in the step (a), an installation hole is provided in the covering body so as to penetrate the pile-shaped body.   After the step b, a step d of installing a ring-shaped auxiliary covering body having a predetermined weight and rigidity in a range covering a gap between the pile-shaped body and the covering body is further provided. The construction method according to claim 11 or 12, wherein the scouring prevention work around the pile-shaped body is performed.   In the step a, a gantry for positioning is installed on a water bottom at a peripheral portion of the installation position of the covering body, and the hanging position of the covering body and the gantry for positioning are brought into contact with each other to determine the installation position of the covering body. The construction method of a scouring prevention work around a pile-like body according to any one of claims 11 to 13, characterized in that:

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