Bed protection structure for riverbed scouring prevention, and construction method for the same

Abstract

To provide a bed protection structure for riverbed scouring prevention that can prevent scouring of a riverbed and can minimize the possibility of scattering or washing away of bed protection works, and to provide a construction method for the same.SOLUTION: A bed protection structure 10 for preventing scouring of a riverbed comprises: a cage mat portion 20 which is laid on the riverbed and has a filler material 14 filled therein; and an anchor portion 30 which is embedded in an excavation portion 16 formed by excavating downward the riverbed at the most upstream side of the cage mat portion 20 and has the filler material 14 filled therein, wherein the cage mat portion 20 and the anchor portion 30 are integrally connected. In addition, a construction method for the bed protection structure 10 comprises: an excavation portion formation process in which the most upstream side of the riverbed at the construction site of the bed protection structure 10 is excavated downward to form the excavation portion 16; a cage mat portion formation process in which the cage mat portion 20 is formed at the downstream side of the excavation portion 16; and an anchor portion formation process in which the anchor portion 30 is formed in the excavation portion 16 and the cage mat portion 20 and the anchor portion 30 are integrated together.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a bed protection structure for preventing scouring of a riverbed and a construction method thereof. [Background technology]

[0002] 2. Description of the Related Art Bed protection works, which consist of a plurality of bed protection blocks laid in a river channel for the purpose of preventing scouring of the riverbed by flowing water, have been known mainly downstream of river structures such as sluice gates and weirs.

[0003] Also, a scouring prevention structure for preventing scouring of a riverbed, a waterway bottom, a still water pond, or the seabed and a construction method thereof have been disclosed (see Patent Document 1). The scouring prevention structure disclosed in Patent Document 1 is characterized in that it comprises a plurality of first mats that are laid on a riverbed or the like and filled with a filler material to prevent the suction of sand and gravel from the riverbed or the like, and a plurality of protection blocks that are laid on the upper side of the first mats to protect the riverbed or the like, and adjacent protection blocks are connected to each other in a flexible manner. Furthermore, it is characterized in that it comprises a second mat that is buried in the riverbed or the like so as to be located on the tip side of the plurality of first mats, is thicker than the first mats, is filled with the filler material, and prevents the suction of sand and gravel from the riverbed or the like, and the plurality of protection blocks are laid from the upper side of the plurality of first mats to the upper side of the second mat.

[0004] It is described that the scouring prevention structure disclosed in Patent Document 1 can suppress tilting of the protective block due to scouring of the lower side of the protective block, thereby stabilizing the installation state of the protective block. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2023-87962 A Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional riverbed protection works using bed protection blocks can prevent scouring of the riverbed to a certain extent if the flow velocity is gentle. However, when the river rises due to heavy rain and the flow velocity increases, scouring progresses through the gaps between the bed protection blocks, causing the bed protection blocks to sink. If scouring progresses further, the bed protection blocks move and scatter, the river flow becomes more complicated, and the flow velocity increases in some places, which can cause the riverbed to lower and localized scouring to cause the bed protection works to collapse.

[0007] In addition, according to the scouring prevention structure disclosed in Patent Document 1, multiple protective blocks are laid on the upper side of the first mat, and it is believed that scouring from the gaps between the protective blocks can be prevented to some extent. However, in a structure in which multiple protective blocks are laid, it is believed that the flow tends to concentrate in the gaps between the protective blocks as the flow speed increases, and when the flow concentrates in the gaps, scouring is likely to occur accordingly.

[0008] Furthermore, in recent years, there have been many cases of localized flooding and sudden increases in flow speed due to heavy rain caused not only by typhoons but also by the occurrence of linear rainbands. In these cases, there is a high risk that bed protection works using laid bed protection blocks will be scattered or washed away, and recovery work will require time and effort, so new bed protection works are required.

[0009] In view of the above problems, the inventors of the present application conducted extensive research in order to provide a riverbed scouring prevention bed protection structure and its construction method that can prevent scouring of the riverbed and minimizes the possibility of the bed protection works being scattered or washed away, and as a result, they arrived at the present invention. [Means for solving the problem]

[0010] In other words, the present invention is a bed protection structure for preventing scouring of a riverbed, comprising a cage mat section that is laid on the riverbed and filled with filler material inside, and an anchor section that is buried in an excavation section formed by excavating the riverbed downward on the upstream side of the cage mat section and filled with the filler material inside, and is characterized in that the cage mat section and the anchor section are connected together as a single unit.

[0011] In the riverbed scouring prevention bed protection structure of the present invention, the inside of the anchor portion is divided into a plurality of cells.

[0012] Furthermore, in the riverbed scouring prevention bed protection structure of the present invention, the cross-sectional depth of the excavated portion (anchor portion) in the flow direction is characterized in that it is deepest on the most upstream side and gradually becomes shallower in the downstream direction.

[0013] In addition, the riverbed scouring prevention bed protection structure of the present invention is characterized in that the cross-sectional depth of the excavated portion (anchor portion) in the flow direction gradually becomes deeper from the most upstream side to the downstream side, and gradually becomes shallower from the deepest part.

[0014] The present invention also relates to a construction method for a bed protection structure to prevent scouring of a riverbed, characterized in that it includes an excavation section formation step of excavating downwardly the most upstream side of the riverbed at the construction site of the bed protection structure to form an excavation section, a cage mat section formation step of forming a cage mat section on the downstream side of the excavation section, and an anchor section formation step of forming an anchor section in the excavation section and integrating the cage mat section with the anchor section.

[0015] Furthermore, in the construction method for a riverbed scouring prevention bed protection structure of the present invention, the anchor portion forming step is characterized by including a step of dividing the inside of the anchor portion into a plurality of cells. Effect of the Invention

[0016] According to the riverbed scouring prevention bed protection structure of the present invention, the structure itself is simple, but the cage mat part of the present invention can prevent scouring of the riverbed. Also, unlike the conventional structure in which a plurality of bed protection blocks are laid, the present invention is a structure in which the cage mat part and the anchor part are connected together as one unit, so there is no risk of the cage mat part being scattered or washed away in the event of a flood.

[0017] Furthermore, even if the riverbed below the cage mat is scoured to some extent due to flooding or the like, the cage mat can be maintained in its laid state along the scoured riverbed because the entire cage mat is supported by the anchor parts. Therefore, the cage mat can maintain its effectiveness in preventing scouring of the riverbed for a long period of time, and the cage mat is placed more firmly due to tension applied to it, further improving the scour prevention effect.

[0018] Furthermore, in the riverbed scouring prevention bed protection structure of the present invention, the anchor part is divided into a plurality of cells, which makes it possible to suppress the movement of the filling material within the anchor part due to the river flow, thereby enhancing the effectiveness of the anchor part in preventing scouring of the riverbed.

[0019] Furthermore, in the riverbed scouring prevention bed protection structure of the present invention, the cross-sectional depth of the anchor section (excavation section) in the flow direction is deepest at the upstream side and gradually becomes shallower in the downstream direction, or gradually becomes deeper from the upstream side in the downstream direction and gradually becomes shallower from the deepest part, which further enhances the effect of the anchor section and significantly reduces the work of backfilling the excavation hole when forming the excavation section.

[0020] Furthermore, according to the construction method of the present invention for a riverbed scouring prevention bed protection structure, while the structure itself is simple, it is possible to construct a bed protection structure that can prevent scouring of the riverbed and that does not have the risk of the basket mat portion being scattered or washed away in the event of a flood.

[0021] Furthermore, since the anchor portion formation process in the construction method of the riverbed scouring prevention bed protection structure of the present invention includes a process of dividing the inside of the anchor portion into a plurality of cells, it is possible to construct a bed protection structure that enhances the anchor portion's effect of preventing scouring of the riverbed. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a schematic plan view showing the construction of the riverbed scouring prevention bed protection structure of the present invention. [Diagram 2] FIG. 2(a) is a schematic cross-sectional view of one embodiment of the AA portion shown in FIG. 1, and FIG. 2(b) is a schematic cross-sectional view showing another aspect of the anchor portion. [Diagram 3] 1. FIG. 4(a) is a schematic cross-sectional view of another embodiment at the AA portion shown in FIG. 1, and FIG. 4(b) is a schematic cross-sectional view showing another aspect of the anchor portion. [Figure 4] 1. FIG. 4(a) is a schematic cross-sectional view of another embodiment at the AA portion shown in FIG. 1, and FIG. 4(b) is a schematic cross-sectional view showing another aspect of the anchor portion. [Diagram 5] 3 is a schematic cross-sectional view showing the deformed state of the riverbed scouring prevention bed protection structure shown in FIG. 2(b). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the riverbed scouring prevention bed protection structure of the present invention will be described in detail with reference to the drawings. In the following, the "riverbed scouring prevention bed protection structure" will be simply referred to as the "bed protection structure". Figure 1 is a schematic plan view showing the state in which the bed protection structure of the present invention is constructed, and Figure 2(a) is a schematic cross-sectional view showing one embodiment of the AA section in the construction state of the bed protection structure shown in Figure 1. As shown in these figures, the bed protection structure 10 of this embodiment is a bed protection structure for preventing scouring of the riverbed RB, and is installed downstream of an apron 12 of a dam (not shown).

[0024] More specifically, the bed protection structure 10 of this embodiment is composed of a cage mat section 20 that is laid on the riverbed RB downstream of the apron 12 and has a filler material 14 filled therein, and an anchor section 30 that is buried in an excavation section 16 formed by excavating downward the riverbed RB on the upstream-most side of the cage mat section 20 and has a filler material 14 filled therein.

[0025] The cage mat section 20 of the bed protection structure 10 of this embodiment is formed by filling a plurality of cells 25 consisting of a bottom net 21, a side net 22, a partition net 23, and a cover net 24, all of which are made of mesh members, with a filler material 14. Examples of the filler material 14 include gravel, boulders, crushed stone, and broken granite stones, and the particle size of the filler material 14 is preferably set to a size that does not pass through the mesh of the mesh members.

[0026] The material of the net-like member is not particularly limited, but for example, high-strength stainless steel is preferable because of its excellent abrasion resistance and durability. The size of the mesh of the net-like member is also not particularly limited as long as the filler 14 can pass through it.

[0027] Moreover, it is preferable that fastening members 26 are arranged in each cell 25 (see Figs. 1 and 2). The fastening members 26 are arranged in the vertical direction in the cell 25 to connect the bottom net 21 and the lid net 24. By arranging the fastening members 26, it is possible to prevent the basket mat portion 20 from loosening and to prevent the filling material 14 from moving in the cell 25. The number and positions of the fastening members 26 to be arranged are not particularly limited and are set appropriately according to the size of the cell 25.

[0028] The anchor section 30 of the bed protection structure 10 of this embodiment is formed by forming cells 31 consisting of at least a bottom net 21, a side net 22, and a cover net 24 made of mesh members in the excavation section 16 formed by excavating the riverbed RB on the most upstream side of the cage mat section 20, in other words, the riverbed RB immediately downstream of the apron 12, downward, and filling the cells 31 with the filler material 14. The filler material 14 can be, for example, gravel, boulders, crushed stone, or broken granite stones, and in the case of repair work of an existing bed protection work, it is also possible to reuse the existing bed protection block 32 as the filler material 14. The anchor section 30 formed by filling the cells 31 formed in the excavation section 16 with the filler material 14 is in a state of being buried in the excavation section 16.

[0029] The bed protection structure 10 of this embodiment is characterized in that the cage mat portion 20 and the anchor portion 30 constituting the bed protection structure 10 are integrally connected. One example of a method for integrally connecting the cage mat portion 20 and the anchor portion 30 is to connect the cells 25 constituting the cage mat portion 20 and the cells 31 constituting the anchor portion 30 with a coil wire or the like, but in this embodiment, by sharing at least the bottom net 21 and the lid net 24 constituting the cage mat portion 20 and the anchor portion 30, the cage mat portion 20 and the anchor portion 30 can be easily formed integrally.

[0030] That is, the bottom net 21 constituting the cage mat section 20 is disposed from the most downstream side toward the upstream side of the riverbed RB on which the cage mat section 20 is laid, and is also disposed continuously in the excavation section 16 formed immediately downstream of the apron 12. After filling the cells 25 relating to the cage mat section 20 and the cells 31 relating to the anchor section 30 with the filler material 14, the cover net 24 is disposed continuously from the cage mat section 20 to the anchor section 30, whereby the cage mat section 20 and the anchor section 30 can be integrally connected. Details of the construction method for the bed protection structure of the present invention will be described later.

[0031] According to the bed protection structure 10 of this embodiment configured as described above, the structure itself is simple, but the cage mat portion 20 of the bed protection structure 10 of this embodiment can prevent scouring of the riverbed RB. Also, unlike conventional structures in which a plurality of bed protection blocks are laid, the bed protection structure 10 of this embodiment is configured by integrally connecting the cage mat portion 20 and the anchor portion 30, so there is no risk of the cage mat portion 20 scattering during flooding, or being washed away by the anchor portion 30 connected integrally to the cage mat portion 20.

[0032] Furthermore, even if the riverbed RB below the cage mat section 20 is scoured to some extent due to the occurrence of a flood or the like, the cage mat section 20 can be maintained in its laid state along the scoured riverbed RB because the entire cage mat section 20 is supported by the anchor section 30 as shown in Fig. 5. Therefore, the effect of preventing scouring of the riverbed RB by the cage mat section 20 can be maintained for a long period of time, and the cage mat section 20 is laid more firmly due to tension applied to it, thereby further improving the scour prevention effect.

[0033] Although the bed protection structure 10 according to one embodiment of the present invention has been described above, the bed protection structure of the present invention is not limited to the above-mentioned embodiment. The bed protection structure 10a according to another embodiment of the present invention shown in Fig. 3(a) has a basic structure that is substantially similar to the bed protection structure 10 according to the above-mentioned embodiment, and the cage mat portion 20 that is laid on the riverbed RB downstream of the apron 12 and filled with the fill material 14 has the same structure.

[0034] The anchor portion 30a in the bed protection structure 10a of this embodiment is buried in an excavation portion 17 formed by excavating downward the riverbed RB on the upstream-most side of the cage mat portion 20, and is formed by filling the inside with filler material 14, but the cross-sectional shape of this excavation portion 17 in the flow direction is different from that of the excavation portion 16 related to the bed protection structure 10.

[0035] That is, the cross-sectional depth in the river flow direction of the anchor part 30a (excavation part 17) of the bed protection structure 10a of this embodiment is characterized in that it is deepest on the most upstream side, that is, immediately downstream of the apron 12, and gradually becomes shallower toward the downstream side. The anchor part 30a of the bed protection structure 10a of this embodiment shown in Figure 3(a) can be formed larger than the anchor part 30 of the bed protection structure 10, so that the effect of preventing the cage mat part 20 from being washed away can be further improved and the backfilling work of the excavation part 17 excavated when forming the anchor part 30a can be significantly reduced.

[0036] Furthermore, the bed protection structure 10b according to another embodiment of the present invention shown in Figure 4(a) has a structure that is substantially similar to the bed protection structures 10, 10a according to the embodiments of the present invention, and the cage mat portion 20 has the same structure. However, the anchor portion 30b according to the bed protection structure 10b of this embodiment is buried in an excavation portion 18 formed by excavating downward the riverbed RB on the most upstream side of the cage mat portion 20, and is formed by filling the inside with filler material 14. However, the cross-sectional depth of this anchor portion 30b (excavation portion 18) in the river flow direction is characterized in that it gradually becomes deeper from the most upstream side, that is, from the side immediately downstream of the apron 12, to the downstream side, and gradually becomes shallower from the deepest part until it connects to the riverbed RB.

[0037] The anchor portion 30b of the bed protection structure 10b of this embodiment shown in Figure 4(a) can be formed even larger than the anchor portions 30, 30a, thereby further enhancing the effect of preventing the cage mat portion 20 from being washed away and significantly reducing the work of backfilling the excavated portion 18 excavated when forming the anchor portion 30b.

[0038] The embodiment of the bed protection structure of the present invention has been described above, but in the anchor parts 30, 30a, 30b according to each of the above-mentioned embodiments, each of the anchor parts 30, 30a, 30b may be divided into a plurality of cells. For example, the anchor part 30 according to the embodiment of the bed protection structure 10 shown in Fig. 2(a) can be formed by filling the filler material 14 into the cell 31 composed of at least the bottom net 21, the side net 22, and the cover net 24 arranged in the excavation part 16.

[0039] Further, in the process of filling the cell 31 from below with the filler material 14, as shown in FIG. 2(b), by disposing a partition net 23 that divides the cell 31 in the vertical direction at an appropriate depth and dividing it into a plurality of cells while filling the filler material 14 to the top, it is possible to suppress the movement of the filler material 14 within the anchor part 30, which is most susceptible to the influence of the river flow immediately downstream of the apron 12, and to enhance the effect of preventing scouring of the riverbed RB of the anchor part 30.

[0040] Similarly, in the anchor part 30a of the bed protection structure 10a of the embodiment shown in FIG. 3(a) and the anchor part 30b of the bed protection structure 10b of the embodiment shown in FIG. 4(a), in the process of filling the cells 31 of the anchor parts 30a and 30b from below with the filler material 14, as shown in FIG. 3(b) and FIG. 4(b), by disposing partition nets 23 of an appropriate depth and width that divide the inside of the cells 31 in the vertical and horizontal directions to divide them into a plurality of cells while filling the filler material 14 to the top, it is possible to suppress the movement of the filler material 14 within the anchor parts 30a, 30b and to enhance the effect of preventing scouring of the riverbed RB of the anchor parts 30a, 30b.

[0041] Next, the construction method of the bed protection structure of the present invention will be described with reference to Fig. 2(a). In the construction method of the bed protection structure 10 of this embodiment, first, in the excavation part formation step, the most upstream side of the riverbed RB at the construction site of the bed protection structure 10, that is, the immediately downstream side of the apron 12, is excavated downward to form the excavation part 16.

[0042] Next, in the cage mat portion forming process, the cage mat portion 20 is formed on the downstream side of the excavation portion 16. More specifically, a bottom net 21 constituting a plurality of cells 25 for the cage mat portion 20 and a cell 31 for the anchor portion 30 is laid from the most downstream side of the riverbed RB located at the laying location of the cage mat portion 20 to the excavation portion 16. Then, a side net 22 and a partition net 23 are arranged to form the plurality of cells 25 for the cage mat portion 20. When the side net 22 is laid, the side net 22 is also arranged in the excavation portion 16 to form the cell 31 for the anchor portion 30.

[0043] Then, the filler 14 is filled in the cells 25 on the most downstream side of the cage mat portion 20, and then the filler 14 is filled in the cells 25 on the upstream side in sequence, whereby the cage mat portion 20 is generally formed.

[0044] When the cage mat portion 20 is mostly formed and reaches the excavated portion 16, in the anchor portion formation process, the cells 31 formed in the excavated portion 16 are filled with filler material 14 to form the anchor portion 30. The anchor portion 30 formed by filling the cells 31 with filler material 14 is embedded in the excavated portion 16. Then, by disposing a lid net 24 on the cage mat portion 20 and the anchor portion 30, a bed protection structure 10 in which the cage mat portion 20 and the anchor portion 30 are integrated is obtained.

[0045] In the construction method of the bed protection structure 10 of this embodiment, the lid nets 24 constituting the cage mat portion 20 and the anchor portion 30 are disposed together in the final process, but for example, in the cage mat portion forming process, the lid nets 24 may be disposed sequentially at the time when the filler material 14 is filled in the cells 25. If the cage mat portion 20 and the anchor portion 30 of the bed protection structure 10 of this embodiment are integrated, the method of integration is not particularly limited, for example, by sharing the bottom net 21, side net 22, and lid net 24 that form the cells 25 of the cage mat portion 20 and the cells 31 of the anchor portion 30 as in this embodiment, or by connecting the cells 25 of the cage mat portion 20 and the cells 31 of the anchor portion 30 with a coil wire or the like.

[0046] The construction method for the bed protection structure 10 of this embodiment has been described above, but the construction method for the bed protection structures 10a and 10b according to the other embodiments of the present invention is similar, so the description will be omitted.

[0047] As another embodiment of the construction method of the bed protection structure of the present invention, the anchor part formation step in the construction method of the bed protection structure 10 described above may include a step of dividing the inside of the anchor part 30 into a plurality of cells. That is, in the anchor part formation step, as shown in Fig. 2(b), in the process of filling the inside of the cell 31 formed in the excavation part 16 from below with the filler material 14, a partition net 23 is arranged to divide the inside of the cell 31 in the vertical direction at an appropriate depth, and the filler material 14 is filled up to the top while dividing the inside of the cell 31 into a plurality of cells. After filling the inside of the cell 31 with the filler material 14 is completed, a cover net 24 is arranged on the cage mat part 20 and the anchor part 30, thereby obtaining the bed protection structure 10 in which the cage mat part 20 and the anchor part 30 are integrated.

[0048] Furthermore, in the anchor part formation step in the construction method for the bed protection structures 10a, 10b of the embodiment of the present invention, when a step of dividing the inside of the anchor parts 30a, 30b into a plurality of cells is included, in the anchor part formation step, as shown in Figures 3(b) and 4(b), in the process of filling the cells 31 formed in the excavated parts 17, 18 from below with the filler material 14, a partition net 23 is arranged to divide the inside of the cells 31 in the vertical and horizontal directions at an appropriate depth and width, dividing the inside of the cells 31 into a plurality of cells while filling the filler material 14 up to the top, and once filling of the cell 31 with the filler material 14 is completed, a cover net 24 is arranged on the cage mat part 20 and the anchor part 30a or the anchor part 30b, thereby obtaining the bed protection structures 10a, 10b in which the cage mat part 20 and the anchor part 30a or the anchor part 30b are integrated.

[0049] Although the embodiment of the bed protection structure and its construction method of the present invention has been described in detail above, the above-mentioned embodiment should not be interpreted as substantially limiting the technical idea of ​​the present invention. For example, the bed protection blocks 32 are illustrated as the fill material 14 in the anchor parts 30, 30a, and 30b of the bed protection structures 10, 10a, and 10b of the embodiment of the present invention shown in Figures 2 to 4, but the fill material 14 filled in the cells 31 of the anchor parts 30, 30a, and 30b does not necessarily have to include the bed protection blocks 32, and the cells 31 may be filled with fill material 14 such as gravel, boulders, crushed stones, and broken granite stones. The present invention can be implemented with appropriate improvements, changes, or additions based on the ingenuity and ingenuity of a person skilled in the art within the scope of the gist of the present invention. [Explanation of symbols]

[0050] 10,10a,10b: Bed protection structure 12: Apron 14: Filling material 16, 17, 18: Excavation section 20: Basket mat section 21: Bottom net 22: Side net 23: Partition net 24: Lid net 25,31: Cell 26: Fastening member 30, 30a, 30b: Anchor part 32: Bed protection block RB: Riverbed

Claims

1. A bed protection structure for preventing scouring of a riverbed, A basket mat portion laid on the riverbed and filled with a filling material; an anchor portion that is buried in an excavation portion formed by excavating the riverbed downward on the most upstream side of the cage mat portion and that is filled with the filler; The present invention relates to a method for manufacturing a computer-implemented ... A riverbed scouring prevention bed protection structure characterized in that the cage mat portion and the anchor portion are integrally connected.

2. A riverbed scouring prevention bed protection structure according to claim 1, characterized in that the inside of the anchor portion is divided into a plurality of cells.

3. 3. A riverbed scouring prevention bed protection structure according to claim 1 or 2, characterized in that the cross-sectional depth of the anchor portion in the flow direction is deepest on the most upstream side and gradually becomes shallower in the downstream direction.

4. 3. A riverbed scouring prevention bed protection structure according to claim 1 or 2, characterized in that the cross-sectional depth of the anchor portion in the flow direction gradually becomes deeper from the most upstream side in the downstream direction and gradually becomes shallower from the deepest part.

5. A construction method for a bed protection structure for preventing scouring of a riverbed, comprising the steps of: an excavation section forming step of excavating the most upstream side of the riverbed at the construction site of the bed protection structure downward to form an excavation section; a cage mat portion forming step of forming a cage mat portion downstream of the excavation portion; an anchor portion forming step of forming an anchor portion in the excavation portion and integrating the anchor portion with the cage mat portion; A construction method for a riverbed scouring prevention bed protection structure comprising:

6. 6. The construction method for a riverbed scouring prevention bed protection structure according to claim 5, wherein the anchor portion forming step includes a step of dividing the inside of the anchor portion into a plurality of cells.

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