Scour prevention structure and its construction method

Abstract

To provide an anti-scouring structure and its construction method capable of suppressing suction and leakage of gravel from the bottom and surroundings of a protective block and stabilizing the installation state of multiple protective blocks.SOLUTION: An anti-scouring structure (10) includes multiple bed protection blocks (16) as multiple protective blocks that are laid on the river bed (SB) to protect the river bed (SB), and adjacent bed protection blocks (16) are flexibly connected to each other. The anti-scouring structure (10) includes a suction prevention member (22) that is provided to some of the bed protection blocks (16) to prevent drainage and seepage of gravel in the river bed (SB) from a gap between the adjacent bed protection blocks (16).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a scour prevention structure for preventing scouring of a riverbed, a waterway bottom, a still water pond, or the seabed, and a construction method thereof. [Background technology]

[0002] Many agricultural intake weirs are installed in the mid- to upper reaches of rivers, for example, to facilitate water supply to farm fields. Furthermore, downstream of the weir, the riverbed is often excavated for flood control or aggregate extraction purposes, causing riverbed lowering upstream. When the riverbed lowering reaches the downstream side of the weir, piping and scouring occur, sucking out sand and gravel from the weir bottom and causing the concrete floor (apron) downstream of the weir to collapse, leading to damage to the weir.

[0003] Generally, downstream of a structure such as a weir, a plurality of bed protection blocks are laid as a plurality of protection blocks for protecting the riverbed. The bed protection blocks are arranged in multiple rows along the river width direction. Adjacent bed protection blocks may be flexibly connected by connecting members such as shackles to prevent them from scattering due to flowing water, etc. Alternatively, adjacent bed protection blocks may be configured to interlock with each other so that they are flexibly connected. In addition, the bed protection blocks may be made larger or heavier to prevent them from scattering.

[0004] Incidentally, Patent Document 1 shows a prior art document related to the present invention. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6871583 Summary of the Invention [Problem to be solved by the invention]

[0006] There are gaps of about 5 cm between adjacent protection blocks. If the discharge flow rate from the weir is high, the sand and gravel at the bottom of the protection block is sucked out through the gap, causing the block to sink. If the flow begins to fall onto the protection block due to the sinking, the suction will progress further, creating a large scour hole immediately downstream of the weir.

[0007] A similar phenomenon occurs immediately downstream of the bed protection blocks (bed protection works) when the water level drops due to lowering of the riverbed downstream of the weir. In this case, the lowered water level downstream of the bed protection works increases the flow velocity, expanding scouring immediately downstream of the bed protection works, causing sand and gravel at the bottom of the bed protection works to leak into scour holes, which then cause the bed protection works to bend (become uneven) and tilt (tilt). The expansion of the scour holes makes the bending and tilting even more pronounced. The gaps between the bed protection blocks widen depending on the angle of bending, making it easier for the sand and gravel at the bottom of the bed protection blocks and surrounding areas to be sucked out. In addition, the tilting increases the flow velocity above the bed protection blocks, further exacerbating the suction. In this way, the tilting spreads to the upstream part of the bed protection works and, when it reaches immediately downstream of the weir, also increases the flow velocity immediately downstream of the weir. This causes scour holes to appear and expand immediately downstream of the weir. If the expansion of the scour hole causes a downflow immediately downstream of the weir, the scour hole will expand further, and combined with the settlement of the bed protection block due to the expansion of scouring immediately downstream of the bed protection work, the lowering of the riverbed downstream of the weir will eventually spread to immediately downstream of the weir.

[0008] The expansion of the scour hole immediately downstream of the weir and the lowering of the riverbed immediately downstream of the weir (subsidence of the bed protection block) as described above can cause piping at the bottom of the weir and leakage of sand and gravel from the bottom of the apron, ultimately leading to damage to the weir.

[0009] Connecting the protection blocks together does not prevent sand and gravel from being sucked out of the gaps between them when the riverbed downstream lowers and the flow velocity increases, so it does not prevent scouring immediately downstream of the weir or damage to the weir. On the other hand, even if the protection blocks are made larger or heavier, they cannot prevent the expansion of scouring immediately downstream of the protection works due to the lowering of the riverbed downstream, and therefore cannot prevent the protection blocks from rolling or being washed away into the scour hole immediately downstream of the protection works, which ultimately leads to the scattering of the protection blocks and scouring immediately downstream of the weir. In other words, connecting the protection blocks together or making them larger or heavier only serves to somewhat delay scouring and riverbed lowering immediately downstream of the weir. Furthermore, adding more protection blocks to replace lost protection blocks simply results in more blocks being washed away and has little effect.

[0010] Possible measures to prevent damage to structures such as weirs include installing river crossing structures such as ground sills downstream of the weir to restore the tilted bed protection blocks to their original position, or injecting fill concrete between adjacent bed protection blocks. The former method requires the construction of a new river crossing structure similar to the weir, which is costly. Furthermore, scouring and riverbed lowering problems also occur immediately downstream of the ground sills, necessitating the repeated construction of additional ground sills. The latter method eliminates the flexibility of adjacent bed protection blocks, preventing them from adapting to changes in the riverbed topography. Scouring immediately downstream of the bed protection structure can damage the structure and wash away the bed protection blocks from its downstream end, ultimately causing scouring immediately downstream of the weir. Alternatively, to prevent scouring immediately downstream of the weir, frequent backfilling of scour holes immediately downstream of the bed protection structure and repairing the bed protection structure are required, which also increases costs.

[0011] In other words, in response to the drop in downstream water levels and increased flow velocity on the bed protection blocks caused by the lowering of the riverbed downstream of the weir, it is not easy or costly to prevent scouring and riverbed lowering immediately downstream of the apron.

[0012] The above-mentioned scouring problems occur not only in scour prevention structures installed downstream of structures such as weirs, but also in scour prevention structures installed upstream of structures if the flow velocity is fast. They can also occur if the flow velocity is faster than expected when designing a bed protection structure, even if the downstream riverbed has not lowered. They can also occur in scour prevention structures installed on the bottom of a waterway, still water pond, or seabed, regardless of whether they are in a river.

[0013] Therefore, one aspect of the present invention aims to prevent scouring and deterioration of the riverbed and other surrounding areas upstream and downstream of the structure by suppressing the suction and leakage of sand and gravel from the bottom and surrounding areas of protective blocks, etc., and stabilizing the installation state of multiple protective blocks, etc. [Means for solving the problem]

[0014] In order to solve the above-mentioned problems, a scour prevention structure according to one aspect of the present invention is a scour prevention structure for preventing scouring of a riverbed, a waterway bottom, a still water pond or the seabed, and comprises a plurality of protection blocks that are laid on the riverbed, waterway bottom, still water pond or seabed and protect the riverbed, waterway bottom, still water pond or seabed, adjacent protection blocks are flexibly connected to each other, and further comprises suction prevention members that are provided on a part of each protection block and prevent suction of sand and gravel from the riverbed, waterway bottom, still water pond or seabed through gaps between adjacent protection blocks.

[0015] In order to solve the above-mentioned problems, a construction method for a scour prevention structure according to one embodiment of the present invention is a method for constructing a scour prevention structure according to one embodiment of the present invention, and includes a laying step of laying a plurality of protection blocks on a riverbed, a waterway bottom, a still water pond, or the seabed, a first connecting step of connecting suction prevention members attached to the side or top surfaces of adjacent protection blocks, and a second connecting step of flexibly connecting adjacent protection blocks that have already been laid.

[0016] Furthermore, a construction method for a scouring prevention structure according to one aspect of the present invention is a method for constructing a scouring prevention structure according to one aspect of the present invention, and includes a laying step of laying a plurality of protective blocks on a riverbed, a waterway bottom, a still water pond, or the seabed so that suction prevention members attached to the bottom or side of each protective block are positioned below the protective blocks adjacent to each protective block, and a connecting step of flexibly connecting adjacent protective blocks that have already been laid. [Effects of the Invention]

[0017] According to one aspect of the present invention, the installation state of multiple protective blocks can be stabilized by suppressing the suction of sand and gravel from the bottom of the protective block and the surrounding area, or by suppressing the leakage of sand and gravel from the bottom of the protective block into the scouring hole. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic cross-sectional side view of a scour prevention structure according to a first embodiment. FIG. [Figure 2] FIG. 2 is a schematic plan view of the scour prevention structure shown in FIG. [Figure 3] FIG. 2 is an enlarged view of part III in FIG. [Figure 4] FIG. 3 is an enlarged view of part IV in FIG. 2. [Figure 5] FIG. 10 is a schematic perspective view showing a state in which a suction prevention member is attached to the side of a bed protection block along its circumferential direction. [Figure 6] FIG. 2 is a schematic diagram illustrating a construction method for the scour prevention structure according to the first embodiment. [Figure 7] FIG. 10 is a schematic cross-sectional side view of a scour prevention structure according to a second embodiment. [Figure 8] FIG. 8 is an enlarged view of part VIII in FIG. [Figure 9] FIG. 10 is a schematic perspective view showing a state in which a suction prevention member is attached to the bottom surface of a bed protection block. [Figure 10] FIG. 10 is a schematic diagram illustrating a construction method for a scour prevention structure according to a second embodiment. [Figure 11]FIG. 10 is a schematic cross-sectional side view of a scour prevention structure according to a third embodiment. [Figure 12] FIG. 12 is a schematic plan view of the scour prevention structure shown in FIG. [Figure 13] FIG. 12 is an enlarged view of a portion XIII in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the specification and claims of this application, the term "riverbed" refers to the riverbed as well as the river slope. The term "waterway bottom" refers to the bottom of various waterways such as agricultural drainage channels and dam spillways as well as the slope of the waterway. The term "seabed" refers to the seabed near the coast as well as the slope of the coast. The term "gravel" refers to sediment and sand. In the drawings, "WD" refers to the river width direction, and "FD" refers to the flow direction.

[0020] [First embodiment] The configuration of a scour prevention structure 10 according to a first embodiment will be described with reference to Figures 1 to 5. Figure 1 is a schematic side cross-sectional view of the scour prevention structure 10 according to the first embodiment. Figure 2 is a schematic plan view of the scour prevention structure 10 shown in Figure 1. Figure 3 is an enlarged view of part III in Figure 1. Figure 4 is an enlarged view of part IV in Figure 2. Figure 5 is a schematic perspective view showing a state in which suction prevention members 22 are attached to the side of a bed protection block 16 along its circumferential direction.

[0021] 1 and 2, the scour prevention structure 10 according to the first embodiment is a structure for preventing scouring of the riverbed SB, and is installed immediately downstream of the weir apron 12. The scour prevention structure 10 is located between revetments 14 installed on both sides of the riverbed SB.

[0022] As shown in Figures 1 to 4, the scour prevention structure 10 includes a plurality of bed protection blocks 16 as a plurality of protection blocks for protecting the riverbed SB, and the plurality of bed protection blocks 16 are laid on the riverbed SB immediately downstream of the apron 12. Each bed protection block 16 is made of, for example, concrete, and the plurality of bed protection blocks 16 are arranged in multiple rows along the river width direction. The interval between adjacent bed protection blocks 16 in the river width direction is set to a gap of, for example, about 5 cm. The interval between adjacent bed protection blocks 16 in the flow direction is set to a gap of, for example, about 5 cm.

[0023] The shape of each bed protection block 16 is shown as a substantially rectangular parallelepiped for ease of explanation, but like existing bed protection blocks, it can be changed to various shapes.

[0024] As shown in Figures 3 to 5, connecting reinforcement bars (connecting rings) 18 are embedded in each corner of the upper part of each bed protection block 16. The connecting reinforcement bars 18 of each bed protection block 16 adjacent to each other in the flow direction and / or river width direction are flexibly connected by connecting members 20 such as shackles. In other words, the scour prevention structure 10 is equipped with connecting members 20 that flexibly connect each bed protection block 16 adjacent to each other in the flow direction and / or river width direction.

[0025] As shown in Figures 3 to 5, the scour prevention structure 10 is equipped with suction prevention members 22 for preventing suction of sand and gravel from the riverbed SB through gaps between adjacent bed protection blocks 16 in the flow direction and / or river width direction. Each suction prevention member 22 is provided along the periphery of a part of the side surface of each bed protection block 16. Each suction prevention member 22 is configured in a mesh or film shape.

[0026] To ensure the wear resistance and durability of each suction prevention member 22, general-purpose fibers such as polyester fiber, nylon fiber, polyethylene fiber, and vinylon fiber, or high-strength fibers such as ultra-high molecular weight polyethylene fiber, polyarylate fiber, aramid fiber, carbon fiber, and glass fiber are used as the material for each suction prevention member 22. The material for each suction prevention member 22 may be a single material or a composite material. The fiber is preferably filament yarn, which has excellent strength, but spun yarn, slit yarn, etc., are also acceptable. Knitted nets are primarily used as the material for each suction prevention member 22. Russell nets are typically used as the knitting method, but knotless or knotted nets may also be used. Woven nets, synthetic resin nets, wire mesh, etc. may also be used for each suction prevention member 22. Film-like materials such as nonwoven fabrics are also acceptable.

[0027] The diameter (thickness) of the mesh legs of each suction prevention member 22 is set, for example, to 1.0 mm to 8.0 mm. The mesh size of each suction prevention member 22 is set to be equal to or smaller than the average grain size of the gravel in the riverbed SB. The average grain size of gravel refers to the grain size at 60% of the integrated value of the grain size distribution determined by sieving. Specifically, the mesh size of each suction prevention member 22 is set, for example, to 5 mm to 25 mm. If mesh larger than the average grain size can be used to prevent suction by armoring or the like, it is possible to use mesh larger than the average grain size. Furthermore, each suction prevention member 22 may consist of a single member, or may be made up of multiple overlapping members.

[0028] A band-like portion having a width of, for example, about 1 cm to 5 cm may be formed at the end of each suction prevention member 22. The band-like portion of each suction prevention member 22 can be formed by closing the mesh at the end of each suction prevention member 22 or by sewing a cloth material such as canvas. Furthermore, each suction prevention member 22 may be a membrane-like member without a mesh instead of a mesh-like member.

[0029] The suction prevention members 22 may be attached to the side of each bed protection block 16 by adhesive bonding using concrete bond, point fastening with stainless steel bolts, attachment using stainless steel pressure plates, or any other known attachment method. However, because the bed protection block 16 is installed in a location where dryness and wetting occur repeatedly, it is desirable that the attachment method for each suction prevention member 22 be a method using a material that is resistant to deterioration due to rust, etc.

[0030] 2 and 4, the ends of adjacent suction prevention members 22 in the flow direction and / or river width direction are connected to each other by a known connecting member 24, such as a braided rope, an interlocking connection using fasteners, a joint belt, or other known connecting member 24. In other words, the scour prevention structure 10 is provided with connecting members 24 that connect the ends of adjacent suction prevention members 22 in the flow direction and / or river width direction. As the connecting member 24, a quick-drying adhesive that bonds the ends of adjacent suction prevention members 22 to each other, or a connecting rope that is inserted through the mesh of the ends of adjacent suction prevention members 22 to connect them may be used.

[0031] Next, a construction method for the scour prevention structure according to the first embodiment will be described with reference to Fig. 3 to Fig. 6. Fig. 6 is a schematic diagram for explaining the construction method for the scour prevention structure according to the first embodiment.

[0032] 3 and 6, the construction method for the scour prevention structure according to the first embodiment is a method for constructing the scour prevention structure 10 on the riverbed SB, and includes a temporary laying step, an attachment step, a first connecting step, a laying step, and a second connecting step. The specific contents of the construction method for the scour prevention structure according to the first embodiment are as follows.

[0033] As shown in VIA of Figure 6, a plurality of bed protection blocks 16 are temporarily laid on the riverbed SB using construction machinery such as a backhoe or a crane (temporary laying process). Then, as shown in Figures 5 and 6VIA, workers attach suction prevention members 22 to the side of each bed protection block 16 along its circumferential direction (attachment process).

[0034] As shown in VIB of Figure 6, the positions of the bed protection blocks 16 on the riverbed SB are adjusted by construction machinery so that the gap between adjacent bed protection blocks 16 is, for example, about 30 cm (temporary laying step). Then, as shown in VIC of Figure 6, workers connect the ends of adjacent suction prevention members 22 with connecting members 24 (first connecting step).

[0035] As shown in VID of Figure 6, the positions of the bed protection blocks 16 on the riverbed SB are adjusted by the construction machine so that the gap between adjacent bed protection blocks 16 is, for example, about 5 cm. This allows the construction machine to lay multiple bed protection blocks 16 on the riverbed SB (laying process).

[0036] 3 and 4, the worker then flexibly connects the connecting reinforcements 18 of adjacent bed protection blocks 16 with connecting members 20 (second connecting step). This completes the construction of the scour prevention structure 10.

[0037] Note that the attachment step may be omitted from the construction method for the scour prevention structure by attaching the suction prevention members 22 to the side surfaces of each bed protection block 16 in advance in a factory or the like. Also, it is not necessary to adjust the positions of the bed protection blocks 16 on the riverbed SB so that the gap between adjacent bed protection blocks 16 is, for example, about 30 cm. In this case, after laying multiple bed protection blocks 16 on the riverbed SB, workers connect the ends of adjacent suction prevention members 22 with connecting members 24.

[0038] Next, the effects of the first embodiment will be described.

[0039] Each suction prevention member 22 is provided along the periphery of a part of the side surface of each bed protection block 16. Therefore, even if adjacent bed protection blocks 16 bend and the gap between them widens, suction of gravel from the riverbed SB through the gap can be prevented. In particular, because the mesh size of each suction prevention member 22 is set to be equal to or smaller than the average particle size of the gravel in the riverbed SB, suction of gravel from the riverbed SB through the gap between adjacent bed protection blocks 16 can be sufficiently prevented. This prevents tilting (tilting) of the bed protection block 16 and scouring immediately downstream of the apron 12 due to suction of gravel from the bottom and surrounding areas of the bed protection block 16, thereby stabilizing the installation state of the multiple bed protection blocks 16. This prevents scouring immediately downstream of the weir installed on the riverbed SB and avoids damage to the weir, such as the collapse of the apron 12.

[0040] As each suction prevention member 22 is provided on the side of each bed protection block 16 and adjacent suction prevention members 22 are connected to each other, friction between the suction prevention members 22 and the bed protection blocks 16 is reduced, preventing deterioration of the suction prevention members 22. Furthermore, as the connecting reinforcement 18 of adjacent bed protection blocks 16 are flexibly connected to each other, the suction prevention members 22 will not break due to tensile force even if adjacent bed protection blocks 16 flex. This makes it possible to improve the durability of the suction prevention members 22.

[0041] Second Embodiment The configuration of a scour prevention structure 26 according to a second embodiment will be described with reference to Figures 7 to 9. Figure 7 is a schematic side cross-sectional view of the scour prevention structure 26 according to the second embodiment. Figure 8 is an enlarged view of part VIII in Figure 7. Figure 9 is a schematic perspective view showing a state in which a suction prevention member is attached to the bottom surface of a bed protection block 16.

[0042] As shown in Figures 7 and 8, the scour prevention structure 26 according to the second embodiment is a structure for preventing scouring of the riverbed SB, and is installed immediately downstream of the weir apron 12. The scour prevention structure 26 is located between revetments 14 installed on both sides of the riverbed SB. The scour prevention structure 26 has a similar configuration to the scour prevention structure 10 (see Figures 1 and 2) described above, and only those points of the configuration of the scour prevention structure 26 that differ from the configuration of the scour prevention structure 10 will be described. For ease of explanation, members that have the same functions as the members described in the first embodiment will be denoted by the same reference numerals, and their description will not be repeated.

[0043] 8 and 9, each suction prevention member 22 is provided on the bottom surface, which is part of each bed protection block 16. Furthermore, a portion of each suction prevention member 22 protrudes outward from at least two sides of the bottom surface of each bed protection block 16. A portion of each suction prevention member 22 is located below the bed protection block 16 adjacent to the respective bed protection block 16 in the flow direction and / or river width direction.

[0044] The method of attaching each suction prevention member 22 to the bottom surface of each bed protection block 16 is by bonding using concrete bond or the like. Each suction prevention member 22 is bonded to the entire bottom surface of each bed protection block 16. In order to reduce the material cost of the suction prevention members 22, each suction prevention member 22 may be bonded to only a part of the bottom surface of each bed protection block 16. Furthermore, the method of attaching each bed protection block 16 and each suction prevention member 22 may be a method other than bonding, and the attachment position may also be on the side of each bed protection block 16. The key point is that no gaps that allow riverbed gravel to pass through should occur between each bed protection block 16 and each suction prevention member 22.

[0045] Next, a construction method for the scour prevention structure according to the second embodiment will be described with reference to Fig. 8 to Fig. 10. Fig. 10 is a schematic diagram for explaining the construction method for the scour prevention structure according to the second embodiment.

[0046] 8 and 10, the construction method for the scour prevention structure according to the second embodiment is a method for constructing the scour prevention structure 26 on the riverbed SB, and includes an attachment step, a laying step, and a connecting step. The specific contents of the construction method for the scour prevention structure according to the second embodiment are as follows.

[0047] As shown in XA in Figure 10, a worker places the suction prevention member 22 in a placement area such as the riverbed SB, and applies concrete bond to the portion of the suction prevention member 22 that corresponds to the bottom surface of the bed protection block 16. Next, a construction machine such as a backhoe or crane is used to place the bed protection block 16 on the corresponding portion of the suction prevention member 22. Then, by allowing the concrete bond to cure, the suction prevention member 22 can be attached to the bottom surface of the bed protection block 16 (attachment process).

[0048] Thereafter, as shown in XB of Figure 10, a construction machine is used to lay multiple bed protection blocks 16 on the riverbed SB so that each suction prevention member 22 is positioned below the bed protection block 16 adjacent to it (laying process). Furthermore, as shown in Figures 8 and 9, workers flexibly connect the connecting reinforcement 18 of each adjacent bed protection block 16 with connecting members 20 (connecting process). This completes the construction of the scour prevention structure 26.

[0049] In addition, by attaching the suction prevention members 22 to the bottom surface of each bed protection block 16 in advance in a factory or the like, the attachment step may be omitted from the construction method of the scouring prevention structure.

[0050] Next, the effects of the second embodiment will be described.

[0051] Each suction prevention member 22 is provided on the bottom surface, which is part of each bed protection block 16. Therefore, even if adjacent bed protection blocks 16 flex and the gap between them widens, suction of gravel from the riverbed SB through the gap can be prevented. In particular, because the mesh size of each suction prevention member 22 is set to be equal to or smaller than the average particle size of the gravel in the riverbed SB, suction of gravel from the riverbed SB through the gap between adjacent bed protection blocks 16 can be sufficiently prevented. This prevents tilting (tilting) of the bed protection blocks 16 due to suction of gravel directly below the bed protection blocks 16 and scouring directly downstream of the apron 12, thereby stabilizing the installation state of the multiple bed protection blocks 16. This prevents scouring directly downstream of the weir installed on the riverbed SB and avoids damage to the weir, such as the collapse of the apron 12.

[0052] A portion of each suction prevention member 22 is located below the adjacent bed protection block 16. Therefore, even if adjacent suction prevention members 22 are not connected to each other, the space between adjacent bed protection blocks 16 on the riverbed SB can be covered with suction prevention members 22. This eliminates the need to connect adjacent suction prevention members 22 to each other, and improves the workability of the scour prevention structure 26.

[0053] Third Embodiment The configuration of a scour prevention structure 28 according to a third embodiment will be described with reference to Fig. 11 to Fig. 13. Fig. 11 is a schematic side cross-sectional view of the scour prevention structure 28 according to the third embodiment. Fig. 12 is a schematic plan view of the scour prevention structure shown in Fig. 11. Fig. 13 is an enlarged view of part XIII in Fig. 11.

[0054] As shown in Figures 11 and 12, the scour prevention structure 28 according to the third embodiment is a structure for preventing scouring of the riverbed SB, and is installed immediately downstream of the weir apron 12. The scour prevention structure 28 is located between revetments 14 installed on both sides of the riverbed SB. The scour prevention structure 28 has a similar configuration to the scour prevention structure 10 (see Figures 1 and 2) described above, and only those points of the configuration of the scour prevention structure 28 that differ from the configuration of the scour prevention structure 10 will be described. For ease of explanation, members that have the same functions as the members described in the first embodiment will be denoted by the same reference numerals, and their description will not be repeated.

[0055] As shown in Figure 13, one of the bed protection blocks 16 adjacent to each other in the flow direction and / or river width direction has a convex portion 30 formed on the top of the other bed protection block 16, protruding towards the other bed protection block 16. The other of the bed protection blocks 16 adjacent to each other in the flow direction and / or river width direction has a concave portion 32 formed on the top of the other bed protection block 16, which can fit into the convex portion 30 of the one bed protection block 16, recessed on the opposite side to the one bed protection block 16. Furthermore, each connecting member 20 and each suction prevention member 22 is located below the convex portion 30 of one of the bed protection blocks 16.

[0056] The scour prevention structure 28 can be constructed on the riverbed SB by the same method as the construction method for the scour prevention structure according to the first embodiment.

[0057] Next, the effects of the third embodiment will be described.

[0058] The third embodiment provides the same effects as the first embodiment. In addition, the third embodiment provides the following effects.

[0059] Because each suction prevention member 22 is located below the convex portion 30 of one of the adjacent bed protection blocks 16, it is possible to reduce wear on the suction prevention member due to gravel flowing down from the upper side of the bed protection block 16. This improves the durability of the suction prevention member 22.

[0060] Since each connecting member 20 is located below the convex portion 30 of one of the adjacent bed protection blocks 16, it is possible to reduce wear on the connecting member 20 caused by gravel flowing down from the upper side of the bed protection block 16. This improves the durability of the connecting member 20.

[0061] Other Embodiments The technical concept applied to the scour prevention structure 10 (26, 28) installed immediately downstream of the weir apron 12 may also be applied to scour prevention structures installed downstream of structures other than weirs, or upstream of structures including weirs. Also, the technical concept applied to the scour prevention structure 10 (26, 28) may also be applied to scour prevention structures installed on the bottom of a waterway, a still water basin, or the seabed.

[0062] 〔summary〕 The scouring prevention structure according to aspect 1 of the present invention is a scouring prevention structure for preventing scouring of a riverbed, a waterway bottom, a still water pond or the seabed, and comprises a plurality of protection blocks laid on the riverbed, waterway bottom, still water pond or seabed to protect the riverbed, waterway bottom, still water pond or seabed, adjacent protection blocks are flexibly connected to each other, and further comprises suction prevention members provided on a part of each protection block to prevent suction of sand and gravel from the riverbed, waterway bottom, still water pond or seabed through gaps between adjacent protection blocks.

[0063] According to the above configuration, the suction prevention member is provided on a portion of each protection block. Therefore, even if adjacent protection blocks bend and the gap between them widens, suction of sand and gravel from the riverbed, waterway bottom, still water pond, or seabed through the gap can be prevented. This suppresses tilting (tilting) of the protection blocks due to suction of sand and gravel from the bottom and surrounding areas of the protection blocks, stabilizing the installation state of the multiple protection blocks. Therefore, scouring immediately downstream of structures such as weirs installed on the riverbed can be prevented, and damage to the structures can be avoided.

[0064] In the scouring prevention structure according to aspect 2 of the present invention, in aspect 1, each suction prevention member is provided along the circumferential direction of the side or top surface of each protective block, and adjacent suction prevention members may be connected to each other.

[0065] According to the above configuration, each suction prevention member is provided on the side or top surface of each protective block, and adjacent suction prevention members are connected to each other, thereby reducing friction between the suction prevention members and the protective blocks and preventing deterioration of the suction prevention members. Furthermore, because adjacent protective blocks are connected to each other in a flexible manner, even if the adjacent protective blocks bend, the suction prevention members will not break due to tensile force. This improves the durability of the suction prevention members.

[0066] A scouring prevention structure according to aspect 3 of the present invention is the same as that of aspect 1, wherein each suction prevention member is provided on the bottom or side of each protective block, and a portion of each suction prevention member may be located below the protective block adjacent to the respective protective block.

[0067] According to the above configuration, a portion of each suction prevention member is located below the protective block adjacent to it. Therefore, the space between adjacent protective blocks in a riverbed or the like can be covered with the suction prevention member without connecting adjacent suction prevention members. This eliminates the need to connect adjacent suction prevention members, improving the ease of construction of the scour prevention structure.

[0068] A scouring prevention structure according to aspect 4 of the present invention is such that, in any of aspects 1 to 3, a convex portion is formed on the top of one of the adjacent protective blocks so as to protrude towards the other protective block, and a concave portion capable of engaging with the convex portion of the one protective block is formed on the top of the other protective block so as to be recessed on the opposite side to the one protective block, and each suction prevention member may be located below the convex portion of the one protective block.

[0069] According to the above configuration, since each suction prevention member is located below the protrusion of one of the protective blocks, wear of the suction prevention members due to sand and gravel flowing down from the upper side of the protective block can be reduced, thereby improving the durability of the suction prevention members.

[0070] The scouring prevention structure according to aspect 5 of the present invention is the same as that of aspect 4, and includes connecting members that flexibly connect adjacent protective blocks, and each connecting member may be located below the convex portion of one of the protective blocks.

[0071] According to the above configuration, since each connecting member is located below the protrusion of one of the protective blocks, wear of the connecting members due to sand and gravel flowing down from the upper side of the protective block can be reduced, thereby improving the durability of the connecting members.

[0072] A scouring prevention structure according to aspect 6 of the present invention is such that, in any of aspects 1 to 4, each suction prevention member is configured in a mesh or membrane shape, and the mesh size of each suction prevention member may be equal to or smaller than the average particle size of gravel in the riverbed, waterway bottom, still water pond, or seabed.

[0073] According to the above configuration, the mesh size of each suction prevention member is smaller than the average particle size of gravel in the riverbed, etc., so that it is possible to sufficiently prevent gravel in the riverbed, etc. from being suctioned out through the gaps between adjacent protective blocks.

[0074] The construction method of a scouring prevention structure according to aspect 7 of the present invention is a method for constructing the scouring prevention structure according to aspect 2, and includes a laying step of laying a plurality of protective blocks on a riverbed, a waterway bottom, a still water pond or the seabed, a first connecting step of connecting suction prevention members attached to the side or top surfaces of adjacent protective blocks, and a second connecting step of flexibly connecting adjacent protective blocks that have already been laid.

[0075] According to the above configuration, the suction prevention members attached to the side or top surfaces of adjacent protective blocks are connected, which reduces friction between the suction prevention members and the protective blocks and prevents deterioration of the suction prevention members. Furthermore, because adjacent protective blocks are connected to each other in a flexible manner, the suction prevention members will not break due to tensile force even if the adjacent protective blocks bend. This improves the durability of the suction prevention members.

[0076] The construction method of a scouring prevention structure according to aspect 8 of the present invention is a method for constructing the scouring prevention structure according to aspect 3, and includes a laying step of laying a plurality of protective blocks on a riverbed, waterway bottom, still water pond or seabed so that the suction prevention members attached to the bottom or side of each protective block are positioned below the protective blocks adjacent to each protective block, and a connecting step of flexibly connecting adjacent protective blocks that have already been laid.

[0077] According to the above configuration, a plurality of protection blocks are laid on a riverbed or the like so that the suction prevention members attached to the bottom or side of each protection block are positioned below the protection blocks adjacent to each protection block. Therefore, the spaces between adjacent protection blocks on the riverbed or the like can be covered with the suction prevention members without connecting adjacent suction prevention members to each other. This eliminates the need to connect adjacent suction prevention members to each other, and improves the ease of construction of the scour prevention structure.

[0078] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0079] 10: Scour prevention structure (scour prevention structure according to the first embodiment), 12: Apron, 14: Revetment, 16: Bed protection block (protection block), 18: Connecting reinforcement, 20: Connecting member, 22: Suction prevention member, 24: Connecting member, 26: Scour prevention structure (scour prevention structure according to the second embodiment), 28: Scour prevention structure (scour prevention structure according to the third embodiment), 30: Convex portion, 32: Concave portion

Claims

1. A scour prevention structure for preventing scouring of a riverbed, a waterway bottom, a still water pond, or the seabed, The protection block is laid on a riverbed, a waterway bottom, a still water pond, or a seabed, and is provided with a plurality of protection blocks for protecting the riverbed, the waterway bottom, the still water pond, or the seabed; Adjacent protection blocks are flexibly connected to each other, Furthermore, a suction prevention member is provided in a part of each protection block to prevent suction of sand and gravel from the riverbed, waterway bottom, still water pond, or seabed through gaps between adjacent protection blocks, Adjacent suction prevention members are connected to each other, Each suction prevention member is provided on the side or top surface of each protection block along its periphery. Anti-scouring structure.

2. a convex portion is formed on an upper portion of one of the adjacent protective blocks so as to protrude toward the other protective block, and a concave portion is formed on an upper portion of the other protective block so as to be recessed on the opposite side to the one protective block, the concave portion being engageable with the convex portion of the one protective block; The scour prevention structure according to claim 1 , wherein each of the suction prevention members is located below the protrusion of the one of the protection blocks.

3. a connecting member that flexibly connects adjacent protection blocks to each other; The scour prevention structure according to claim 2 , wherein each connecting member is located below the protrusion of the one of the protection blocks.

4. 4. The scouring prevention structure according to claim 1, wherein each suction prevention member is configured in a mesh or film shape, and the mesh size of each suction prevention member is equal to or smaller than the average particle size of gravel on the riverbed, the bottom of a waterway, the still water pond, or the seabed.

5. A method for constructing a scour prevention structure to prevent scouring of a riverbed, a waterway bottom, a still water pond, or the seabed, comprising: the scour prevention structure is laid on a riverbed, a waterway bottom, a still water pond, or the seabed, and comprises a plurality of protection blocks for protecting the riverbed, the waterway bottom, the still water pond, or the seabed; Adjacent protection blocks are flexibly connected to each other, Furthermore, a suction prevention member is provided in a part of each protection block to prevent suction of sand and gravel from the riverbed, waterway bottom, still water pond, or seabed through gaps between adjacent protection blocks, Adjacent suction prevention members are connected to each other, The method comprises: a laying step of laying a plurality of protection blocks on a riverbed, a waterway bottom, a still water pond, or the seabed; a first connecting step of connecting the suction prevention members attached to the side surfaces of adjacent protection blocks to each other; a second connecting step of flexibly connecting adjacent protection blocks that have already been laid.

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