Capture fence

Abstract

To provide a capturing fence excellent in transportability, handleability, work efficiency, and economic efficiency, capable of further miniaturizing a constituent member of the capturing fence while holding rigidity of the capturing fence.SOLUTION: In this capture fence 10 three dimensionally constructed by connecting an upstream side column material 1, a downstream side column material 2 and a capture member 3, the downstream side column material 2 is connected to the upstream side column material 1 in an attitude of being inclined downward toward the downstream side D from the upstream side U. A width dimension V of the downstream side column material 2 is smaller than a width dimension W of the upstream side column material 1 to be connected. The upstream side column member 1 is provided in a vertical posture. Alternatively, it is provided in a posture inclined upward from the upstream side U toward the downstream side D. The downstream side column member 2 is connected to the upstream side column member 1 via a joint plate 4. A section modulus of the downstream side column member 2 is smaller than a section modulus of the upstream side column member 1 to be connected. A width dimension V of the downstream side column member 2 is set to 1 / 2 or more of a width dimension W of the upstream side column member 1, and SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention belongs to the technical field of trapping fences constructed three-dimensionally by connecting upstream and downstream pillars with trapping members, and more specifically, relates to a debris flow (sand) and driftwood trapping fence that functions as a trapping fence by being installed on the riverbed in places where there is no regular flow of water but where debris flows are expected to occur during floods. [Background technology]

[0002] There is no constant flow of water, but there are areas where debris flows are expected during floods. Debris flows occur when the ground on a mountainside, which has been weakened by continuous heavy rain, becomes fluid, causing gravel such as soil and stones to flow down the river or stream, and there is a risk of causing damage to settlements downstream. In order to prevent such debris flows from flowing down to settlements, various capture fences (also called capture bodies, protective fences, protective works, or erosion control structures) have traditionally been used, which are erected in the direction of the debris flow (see, for example, Patent Documents 1 to 4).

[0003] These trapping fences block the stones and driftwood contained in the debris flow while allowing water and sand to pass through, separating the rocks from the water and preventing the damaging debris flow from flowing down to the settlements at the foot of the river. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-141568 [Patent Document 2] Patent Publication No. 2021-147823 [Patent Document 3] Patent Publication No. 2021-141824 [Patent Document 4] Japanese Patent Publication No. 2022-39651 Summary of the Invention [Problem to be solved by the invention]

[0005] (1) The trapping fence is required to have a rigidity (structure) that can withstand the external force of the debris flow in order to effectively trap the debris flow and protect the downstream conservation object (prevent disaster). (2) In addition, taking into consideration the construction of the trap fence in narrow areas (narrow sections) such as behind residential houses or along roads, it is required that the components (pillars and beams) that make up the trap fence be made smaller (compact) in order to improve portability, ease of handling, and work efficiency.

[0006] The capture fences according to Patent Documents 1 to 4 meet the requirements (1) for the rigidity of the capture fence and (2) for the miniaturization of the components, to a certain extent. However, if it were possible to further miniaturize the components (2) while maintaining the rigidity of the capture fence (1), it would be even more beneficial, as this would allow for further improvements in portability, ease of handling, and work efficiency.

[0007] Therefore, the present invention was devised in consideration of the problems of the background art described above, and its purpose is to provide a capture fence that is excellent in portability, ease of handling, work efficiency, and economy, and that can further reduce the size of the components described in (2) while maintaining the rigidity of the capture fence described in (1). [Means for solving the problem]

[0008] As a means for solving the above problem, the capture fence according to the invention described in claim 1 is a capture fence constructed three-dimensionally by connecting an upstream post, a downstream post, and a capture member, and the downstream post is connected to the upstream post in an attitude inclined downward from the upstream side to the downstream side, The width of the downstream pillar is smaller than the width of the upstream pillar to which it is connected.

[0009] The invention described in claim 2 is characterized in that, in the capture fence described in claim 1, the upstream post material is arranged in a vertical position or in an upwardly inclined position from the upstream side to the downstream side.

[0010] The invention described in claim 3 is characterized in that, in the capture fence described in claim 1 or 2, the downstream post material is connected to the upstream post material via a joining plate.

[0011] The invention described in claim 4 is characterized in that, in the capture fence described in claim 1 or 2, the cross-sectional modulus of the downstream post material is smaller than the cross-sectional modulus of the upstream post material to which it is connected.

[0012] The invention described in claim 5 is characterized in that, in the capture fence described in claim 1 or 2, the width dimension of the downstream post material is set to be at least half the width dimension of the upstream post material.

[0013] The invention described in claim 6 is characterized in that, in the capturing fence described in claim 1 or 2, the downstream post is detachably attached to the upstream post. [Effects of the Invention]

[0014] (1) The capture fence of the present invention can be implemented with a smaller width dimension (section modulus) of the downstream post material relative to the upstream post material, compared to conventional technologies (e.g., Patent Documents 1 to 4, or Figures 17 and 19 of the present application), making it possible to realize a capture fence that is excellent in transportability, handling, work efficiency, and economy. Accordingly, when the anchor fixing method is used, the base plate attached to the downstream pillar can also be made smaller (compact), making it possible to realize a capture fence that is easier to transport, handle, work efficiently, and is more economical. When the downstream pillar is detachably mounted relative to the upstream pillar, the downstream pillar, which is a main component, can be smoothly attached and detached, allowing for good maintenance work. (2) In particular, the present invention is characterized by the fact that the width of the downstream column is smaller than that of the joining plate bolted to the upstream column, which makes it easier and smoother to weld the joining plate to the downstream column than conventional techniques in which the joining plate (upstream column) and the downstream column have the same width, and factory fabrication is also easier. Therefore, compared to conventional techniques, welding work with superior efficiency and quality can be achieved. (3) Furthermore, since the width of the downstream post is smaller than that of the upstream post in this invention, collisions of debris flows (earth and sand) and driftwood with the downstream post can be reduced compared to the conventional technology in which the widths of the upstream and downstream posts are the same. This makes it possible to realize a trapping fence that is both durable and economical. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of a trapping fence according to the present invention (Example 1) as viewed from the downstream side. [Figure 2] FIG. 2 is a side view of the trapping fence according to FIG. 1. [Figure 3] 2 is a front view of the trapping fence in FIG. 1 as seen from the downstream side. FIG. [Figure 4] 2 is a perspective view of the trapping fence shown in FIG. 1, seen from the upstream side. FIG. [Figure 5] 2 is a front view of the trapping fence in FIG. 1 as seen from the upstream side. FIG. [Figure 6] FIG. 10 is a perspective view of the trapping fence according to the present invention (Example 2) as seen from the downstream side. [Figure 7] FIG. 7 is a side view of the trapping fence according to FIG. 6. [Figure 8] 7 is a front view of the trapping fence shown in FIG. 6 as seen from the downstream side. [Figure 9] FIG. 10 is a perspective view of the trapping fence according to the present invention (Embodiment 3) as viewed from the downstream side. [Figure 10] FIG. 10 is a side view of the trapping fence shown in FIG. 9. [Figure 11] 10 is a front view of the trapping fence shown in FIG. 9 as seen from the downstream side. [Figure 12]10 is a perspective view of the trapping fence shown in FIG. 9, seen from the upstream side. FIG. [Figure 13] 10 is a front view of the trapping fence shown in FIG. 9, seen from the upstream side. [Figure 14] Graphs A and B are graphs summarizing the results of calculations made to confirm the effects of the present invention. [Figure 15] Graphs A and B are graphs summarizing the results of calculations made to confirm the effects of the present invention. [Figure 16] 1 is a graph summarizing the results of calculations performed to confirm the effects of the present invention. [Figure 17] FIG. 10 is a perspective view of a conventional trapping fence corresponding to the first embodiment, viewed from the downstream side. [Figure 18] 18 is a front view of the trapping fence shown in FIG. 17 as seen from the downstream side. [Figure 19] FIG. 11 is a perspective view of a conventional trapping fence corresponding to the third embodiment, viewed from the downstream side. [Figure 20] FIG. 20 is a side view of the trapping fence shown in FIG. 19. [Figure 21] 20 is a front view of the trapping fence shown in FIG. 19, seen from the downstream side. DETAILED DESCRIPTION OF THE INVENTION

[0016] Next, an embodiment of the trapping fence according to the present invention will be described with reference to the drawings. [Example]

[0017] 1 to 5, the capture fence according to the present invention is a capture fence 10 constructed three-dimensionally by connecting an upstream post 1, a downstream post 2, and a capture member 3, and the downstream post 2 is connected to the upstream post 1 in an attitude inclined downward from the upstream side U to the downstream side D. The width dimension V of the downstream post 2 is set smaller than the width dimension W of the upstream post 1 to which it is connected.

[0018] The upstream-side pillar 1 is made of an H-shaped steel and is provided in a vertical position (vertical direction) with respect to the riverbed with its flange surface facing the upstream side U. The downstream column 2 is made of H-shaped steel, and as can be seen in Figure 2, it is tilted downward by approximately 30 degrees (see symbol θ) from the upstream side U to the downstream side D, and its upper end is connected to the center of the height of the upstream column 1 via a connecting plate 4. The capturing members 3 are made of beams (steel pipes) and are provided in multiple stages (six stages in the illustrated example) approximately horizontally between the adjacent upstream pillars 1.

[0019] The width V of the downstream side column 2 (200 mm in the illustrated example) is smaller than the width W of the upstream side column 1 (250 mm in the illustrated example) to be connected. Specifically, in this example, the upstream side column 1 has a height of 250 x 250 x 9 x 14 mm and a section modulus (Z) of Zx: 860 cm 3 , Zy:292cm 3 The downstream column 2 is H200 x 200 x 8 x 12 mm, and the section modulus (Z) is Zx: 472 cm 3 , Zy:160cm 3 H-shaped steel beams are used. In short, the downstream column material 2 in this embodiment is characterized in that its width dimension is set smaller than that of the upstream column material 1, and also in that its section modulus (Z) is set smaller.

[0020] In this embodiment, the upstream pillar 1 is about 3 m high, but the design can be modified appropriately depending on the structural design, such as being able to be about 2 m high as in Example 2. Furthermore, in this embodiment, the upstream pillar 1 is installed in a vertical position relative to the riverbed, but this is not limited to this, and it can also be installed in an attitude inclined upward (for example, at about 60 degrees) from the upstream side U to the downstream side D. The inclination angle θ of the downstream pillar 2 is not limited to the above-mentioned approximately 30 degrees, and can be appropriately changed depending on the structural design. In addition, the joint position with the upstream pillar 1 is not limited to the center in the height direction of the upstream pillar 1, and can be appropriately changed depending on the structural design. The number or size of the upstream side pillars 1, downstream side pillars 2, and capturing members 3 used is not limited to the above, and can be changed as appropriate depending on the structural design. The structural designs mentioned above refer to the expected scale of debris flow (soil and sand) and driftwood, the depth of the debris flow, the flow velocity of the debris flow, or a simulation of capturing debris and driftwood using image analysis.

[0021] The capturing member 3 can be implemented by using H-shaped steel beams instead of the steel pipes. Alternatively, it can be implemented by using a mesh member such as a net, wire, or expanded metal, provided that it has the rigidity required to capture the debris flow (earth and sand) or driftwood.

[0022] In this embodiment, the joining plate 4 is rectangular, with a width (250 mm) equal to the width W of the upstream column 1, and a height sufficient to allow it to be integrated with the downstream column 2. In this embodiment, the joining plate 4 is integrated with the downstream column 2 by welding in a factory or the like before being transported to the site.

[0023] The capture fence 10 may be constructed by an embedding method in which the lower ends of pillars or the like are embedded in a concrete foundation, or as in this embodiment, it may be constructed by an anchor fixing method in which a base plate 6 is provided at the lower end of a pillar or the like and the fence is installed on a concrete foundation using an anchor bolt 7 and a nut (e.g., double nut) 8 (the concrete foundation is omitted for convenience of illustration). Specifically, in this embodiment, the base plate 6, which is integrally formed at the lower end of the upstream pillar 1, is fixed to the concrete foundation using anchor bolts 7 and double nuts 8. Next, the base plate 6, which is integrally formed at the lower end of the downstream pillar 2, is fixed to the concrete foundation using anchor bolts 7 and double nuts 8, and the connecting plate 4, which is integrally formed at the upper end thereof, is detachably fixed to a predetermined position on the flange surface of the upstream pillar 1 facing the downstream side D using bolt fastening means 5. Around the same time as these operations, the capture member 3 is attached to the upstream pillar 1 using bolt fastening means or the like, thereby constructing the capture fence 10 in three dimensions. The effects of the trapping fence 10 having the above configuration will be discussed below.

[0024] <Consideration of the effects of Example 1> (Considerations on stress intensity) FIG. 14A is a graph summarizing the results of trial calculations based on external force conditions (debris flow depth of 1.0 m, debris flow velocity of 6.0 m / sec) to consider the operational effects of the trapping fence 10 according to Example 1. The vertical axis indicates the stress intensity σ (MPa) acting on the upstream column 1 or the downstream column 2, and the horizontal axis indicates the width dimension (size) of the downstream column 2. The solid line indicates the maximum compressive stress intensity acting on the upstream column 1, and the dotted line indicates the maximum tensile stress intensity acting on the upstream column 1. In the figure, "diagonal column" indicates the downstream column 2, "steel height" indicates the height of the capture fence 10 (upstream column 1), and "pin joint" indicates the bolt joint means 5.

[0025] In short, H200 on the horizontal axis indicates the capture fence 10 according to Example 1 (Figures 1 to 5), and H250 on the horizontal axis indicates the capture fence 30 according to the prior art (see Figures 17 and 18, in which the width of the downstream pillar 2 is 250 mm, the same as the width of the upstream pillar 1) (for specific numerical values ​​including the cross-sectional modulus, see paragraph

[0019] ). 14A, it can be seen that the maximum compressive stress and maximum tensile stress values ​​applied to the H200 (Example 1) and the H250 (conventional technology) are almost flat with no difference between them. This confirms that even if the downstream pillar 2 is reduced in size from H250 to H200, it can still function (role) as a trapping fence in the same way as with the H250.

[0026] Next, considering the entire graph in Figure 14A, it can be seen that adding the downstream post 2 reduces the stress generated in the upstream post 1 compared to when there is no downstream post 2 (no diagonal member), and that the maximum tensile stress is almost constant from H125 to H250, regardless of the size of the downstream post 2. It can also be seen that the maximum compressive stress is almost constant from H150 to H250, regardless of the size of the downstream post 2. Furthermore, considering that the maximum tensile stress at H125 is almost the same as the maximum tensile stress at H250, it can be inferred that if the width (or section modulus) of the downstream post 2 is half or more (or approximately 1 / 6.4 or more) that of the upstream post 1, it will be able to function (role) as a trapping fence in the same way as with H250.

[0027] Here, the H125 is H125 x 125 x 6.5 x 9 mm, and the section modulus (Z) is Zx: 134 cm 3 , Zy:46.9cm 3 For reference, H150 is H150 x 150 x 7 x 10 mm, and the section modulus (Z) is Zx: 216 cm 3 , Zy:75.1cm 3 H175 is H175 x 175 x 7.5 x 11 mm, section modulus (Z) is Zx: 331 cm 3 , Zy:112cm 3 This shows H-shaped steel.

[0028] (Cost-effectiveness considerations) 14B is a graph summarizing the results of calculations based on external force conditions (debris flow depth of 1.0 m, debris flow velocity of 6.0 m / sec) to consider the cost-effectiveness of the trapping fence 10 according to Example 1. The vertical axis represents cost-effectiveness (stress reduction rate / mass increase rate), and the horizontal axis represents the width dimension (size) of the downstream-side pillar material 2. According to the graph in Figure 14B, it is possible to gradually reduce the generated stress by gradually increasing the size of the downstream pillar material 2, but this increases the mass of the components (steel) of the capture fence, making it uneconomical (reducing cost-effectiveness). Therefore, unlike the prior art, it is not necessary to match the size of the downstream post 2 to the size of the upstream post 1, and it can be confirmed that it is more economical to make the size of the downstream post 2 smaller (downsized) than the size of the upstream post 1, as in the present Example 1. Therefore, since the width dimension (section modulus) of the downstream post 2 can be made smaller compared to the prior art, it is possible to realize a trapping fence that is not only economical but also excellent in transportability, handling, and work efficiency.

[0029] 16 is a graph (not shown) summarizing the results of trial calculations based on external force conditions (debris flow depth of 1.0 m, debris flow velocity of 6.0 m / sec) when welding connection means (rigid connection) are used instead of the bolt connection means 5 (pin connection) of Example 1. The notation of the vertical and horizontal axes is the same as in FIG. 14A, so the explanation thereof will be omitted. (Considerations on stress intensity) 16, it can be seen that the maximum compressive stress and maximum tensile stress values ​​applied to the H200 and the H250 (conventional technology) are almost flat, with no significant difference between them. This confirms that even if the downstream column material is downsized from H250 to H200, it can still function (role) as a trap fence in the same way as the H250. In other words, even if a welded connection means is used instead of the bolt connection means 5 of Example 1, it can still function (role) as a trap fence in the same way as the H250. Next, considering the entire graph in Figure 16, it can be seen that adding a downstream post reduces the stress generated in the upstream post compared to when there is no downstream post (no diagonal member), and the maximum tensile stress does not change significantly from H125 to H250, regardless of the size of the downstream post. It can also be seen that the maximum compressive stress does not change significantly from H150 to H250, regardless of the size of the downstream post. Furthermore, considering that the maximum tensile stress applied to the H125 post does not change significantly from the maximum tensile stress applied to the H250 post, it can be inferred that if the width of the downstream post is at least half that of the upstream post, it will be able to function (role) as a trapping fence in the same way as the H250 post. [Example]

[0030] 6 to 8 show a capture fence 10 according to Example 2. This capture fence 10 differs from the capture fence 10 according to Example 1 in that the height of the upstream pillars 1 has been reduced from 3 m to 2 m. Accordingly, the height of the downstream pillars 2 has also been reduced, the spacing between the base plates 6 attached to the lower ends of the pillars 1, 2 has been reduced (narrowed), and the number of capture members (steel pipes) 3 has been reduced from six (stages) to five (stages). As the other configurations are the same as those of Example 1, the same reference numerals have been used and their explanations will be omitted.

[0031] <Consideration of the effects of Example 2> (Considerations on stress intensity) Figure 15A is a graph summarizing the results of calculations based on external force conditions (debris flow depth of 1.0 m, debris flow velocity of 6.0 m / sec) similar to those in the case of Example 1 above, in order to consider the action and effect of the capture fence 10 of Example 2. As in Figure 14A, the vertical axis indicates the stress intensity σ (MPa) acting on the upstream column 1 or the downstream column 2, and the horizontal axis indicates the width dimension (size) of the downstream column 2. The solid line indicates the maximum compressive stress intensity acting on the upstream column 1, and the dotted line indicates the maximum tensile stress intensity acting on the upstream column 1. In the figure, "diagonal column" refers to the downstream column 2, "steel height" refers to the height of the capture fence 10 (upstream column 1), and "pin joint" refers to the bolt joint means 5.

[0032] In short, H200 on the horizontal axis indicates the capture fence 10 according to Example 2 (Figures 6 to 8), and H250 on the horizontal axis indicates the capture fence according to the prior art (in which the width of the downstream pillar 2 is 250 mm, the same as the width of the upstream pillar 1) (for specific numerical values ​​including the cross-sectional modulus, see paragraph

[0019] ). The graph in Figure 15A shows that the maximum compressive stress and maximum tensile stress values ​​for the H200 (Example 2) compared with the H250 (conventional technology) show almost no difference in the maximum tensile stress values, remaining almost flat. Furthermore, although the maximum compressive stress value decreases slightly, it is considered that this decrease is not a problem for the function of the trapping fence. From this, it can be inferred that even if the downstream column 2 is downsized from H250 to H200, the function (role) of the trapping fence can be performed in the same way as with the H250. Considering the cost-effectiveness considerations explained below with reference to Figure 15B, it can be seen that using H200 is better than using H250 because the mass of the components (steel) increases with the H250 (conventional technology) compared with the H200 (present invention), making it uneconomical (reducing cost-effectiveness).

[0033] Next, considering the entire graph in Figure 15A, it is possible to reduce the stress generated in the upstream column 1 by adding the downstream column 2 compared to when there is no downstream column 2 (no diagonal member), and considering that the maximum tensile stress is almost constant from H125 to H250 regardless of the size of the downstream column 2, it is inferred that if the width (or section modulus) of the downstream column 2 is more than half (or approximately 1 / 6.4 or more) that of the upstream column 1, it can perform the function (role) of the capture fence in the same way as in the case of H250.

[0034] (Cost-effectiveness considerations) 15B is a graph summarizing the results of calculations based on the external force conditions (debris flow depth of 1.0 m, debris flow velocity of 6.0 m / sec) in order to consider the cost-effectiveness of the trapping fence 10 according to Example 2, as in Example 1. The vertical axis represents cost-effectiveness (stress reduction rate / mass increase rate), and the horizontal axis represents the width dimension (size) of the downstream-side pillar 2. According to the graph in Figure 15B, it is possible to gradually reduce the generated stress by gradually increasing the size of the downstream pillar material 2, but this increases the mass of the components (steel) of the capture fence, making it uneconomical (reducing cost-effectiveness). Therefore, unlike the prior art, it is not necessary to match the size of the downstream post 2 to the size of the upstream post 1, and it can be confirmed that it is more economical to make the size of the downstream post 2 smaller (downsized) than the size of the upstream post 1, as in the present Example 2. Therefore, since the width dimension (section modulus) of the downstream post 2 can be made smaller compared to the prior art, it is possible to realize a trapping fence that is not only economical but also excellent in transportability, handling, and work efficiency. [Example]

[0035] 9 to 13 show a capture fence 20 according to Example 3. This capture fence 20 differs from the capture fence 10 according to Example 1 in that the upstream pillar 1 and the downstream pillar 2 are made of steel pipes 11, 12 instead of H-section steel. Another difference is that the upstream pillar 1 and the downstream pillar 2 are joined by welding instead of bolt joints 5 (pin joints). The welding may be performed in a factory or the like before delivery to the site, or may be performed by on-site welding. In the figure, reference numeral 13 denotes a beam (frame material), a flanged steel pipe that also functions as a capture member, reference numeral 13a denotes a flange, reference numeral 14 denotes a branch steel pipe that also functions as a capture member, and reference numeral 15 denotes a base plate. When constructing this capture fence 20 using an anchor fixing method, it is installed on a concrete foundation using anchor bolts and nuts (e.g., double nuts) not shown.

[0036] The capture fence according to Example 3 is a capture fence 20 constructed three-dimensionally by connecting an upstream post 11, a downstream post 12, a beam (capture member) 13, and a capture member 14, and the downstream post 12 is connected to the upstream post 11 in a position inclined downward from the upstream side U to the downstream side D. The width dimension of the downstream post 12 is set smaller than the width dimension of the upstream post 11 to which it is connected, so that Fig. 11 can be easily understood.

[0037] The upstream-side pillar 11 is made of a steel pipe as described above, and is installed in a vertical position (vertical direction) with respect to the riverbed. As mentioned above, the downstream pillar 12 is also made of a steel pipe, and as can be seen in Figure 10, it is tilted downward by approximately 30 degrees (see symbol θ) from the upstream side U to the downstream side D, and its upper end is connected to the center of the height of the upstream pillar 1 by a welding joint means. Steel pipes (flanged steel pipes, branch steel pipes) are also used for the beam materials (capture members) 13 and capture members 14, and are arranged approximately horizontally in multiple rows (a total of five rows in the illustrated example) between adjacent upstream column materials 11. The shape and size of the steel pipes used for the upstream column 11, downstream column 12, and beam 13 are not limited to the illustrated example and can be changed as appropriate depending on the structural design, but typically have an outer diameter of about 300 to 600 mm and a wall thickness of about 9 to 22 mm. Similarly, the shape and size of the steel pipes used for the capture member 14 are not limited to the illustrated example and can be changed as appropriate depending on the structural design, but typically have an outer diameter of about 200 to 300 mm and a wall thickness of about 9 to 22 mm.

[0038] Furthermore, the width of the downstream post 12 (200 mm in the illustrated example) is smaller than the width of the connected upstream post 11 (300 mm in the illustrated example). In short, the downstream post 12 in this embodiment is characterized by having a smaller width than the upstream post 11, and also by having a smaller section modulus.

[0039] In this embodiment, the upstream pillar 11 is about 3 m high, but it can be about 2 m high, and the design can be modified appropriately depending on the structural design. In addition, in this embodiment, the upstream pillar 11 is installed in a vertical position with respect to the riverbed, but this is not limited to this, and it can also be installed in an attitude inclined upward (for example, about 60 degrees) from the upstream side U to the downstream side D. The inclination angle θ of the downstream pillar 12 is not limited to the above-mentioned approximately 30 degrees, and can be appropriately changed depending on the structural design. In addition, the joint position with the upstream pillar 11 is not limited to the center of the upstream pillar 11 in the height direction, and can be appropriately changed depending on the structural design. The number or size of the upstream side pillars 11, downstream side pillars 12, beams 13, and capture members 14 used is not limited to the above, and can be changed as appropriate depending on the structural design. The structural designs mentioned above refer to the expected scale of debris flow (soil and sand) and driftwood, the depth of the debris flow, the flow velocity of the debris flow, or a simulation of capturing debris and driftwood using image analysis.

[0040] The capturing member 14 may be implemented as a mesh member such as a net, wire, or expanded metal instead of the steel pipe.

[0041] In this embodiment, the upstream column 11, downstream column 12, beam 13, and capture member 14 are assembled together in advance at a factory or the like before being transported to the site, and the base plate 15 integrally formed at the lower end of each of the upstream column 11 and downstream column 12 is fixed to the foundation concrete using anchor bolts and double nuts not shown, thereby constructing the three-dimensional capture fence 20 of Example 3.

[0042] In comparison with the above-mentioned Examples 1 and 2, the capture fence 20 of Example 3 is implemented by changing the upstream column 11 and downstream column 12 from H-shaped steel to steel pipes, and by replacing the bolt joint means 5 with a welded joint means. However, this does not change the feature of the present invention that the width dimension (section modulus) of the downstream column is made smaller than that of the upstream column, and as explained in the above paragraph

[0029] , taking into consideration that the same effect can be achieved when implemented with a welded joint means as when implemented with a bolted joint means 5, it is presumed that the capture fence 20 of Example 3 can achieve the same effect as the above-mentioned Examples 1 and 2.

[0043] Although the above-mentioned Examples 1 to 3 have been described based on the drawings, it should be noted that the present invention is not limited to the illustrated examples and includes the range of design modifications and application variations that are normally made by those skilled in the art, as long as they do not deviate from the technical concept thereof. For example, the downstream post 2 or 12 may be connected at a position above or below the center of the height of the upstream post 1 or 11. Connecting them at a higher position often increases the stability of the entire capture fence 10, but often increases the cost of materials. Furthermore, the steel pipe used for the capturing member 3 according to Examples 1 and 2 may be implemented as a single steel pipe as in the illustrated example, or may be implemented as a split structure (may be split at two or more locations) configured to be joined by bolting (flange joining) a pair of flanges provided on the end faces of opposing steel pipes, as in the beam 13 according to Example 3. Meanwhile, the beam 13 and capturing member 14 according to Example 3 may also be implemented as a single steel pipe, in addition to the illustrated example. [Explanation of symbols]

[0044] 1 Upstream column material (H-beam steel) 2 Downstream column material (H-shaped steel) 3. Capture element 4 Joint Plate 5. Bolt connection means (bolt) 6 base plate 7 anchor bolts 8 Nut (double nut) 10 Capture Fence 11 Upstream column material (steel pipe) 12 Downstream column material (steel pipe) 13 Beam material (flanged steel pipe) 13a flange 14 Capture member (branch steel pipe) 15 base plate 20 Capture Fence 21 Downstream column material (H-shaped steel) 22 Downstream column material (steel pipe) 30 Conventional trapping fence 40 Conventional trapping fence U Upstream side D Downstream side W Width of upstream pillar V Width of downstream pillar θ Tilt angle (30 degrees)

Claims

1. In a trapping fence constructed three-dimensionally by connecting an upstream post, a downstream post, and a trapping member, the downstream post is connected to the upstream post in an attitude inclined downward from the upstream side to the downstream side, A capture fence characterized in that the width dimension of the downstream post member is smaller than the width dimension of the upstream post member to which it is connected.

2. 2. The trapping fence according to claim 1, wherein the upstream post is provided in a vertical position or in a position inclined upward from the upstream side to the downstream side.

3. 3. The trapping fence according to claim 1, wherein the downstream post is connected to the upstream post via a joining plate.

4. 3. The trapping fence according to claim 1, wherein the section modulus of the downstream post is smaller than the section modulus of the upstream post to which it is connected.

5. 3. The trapping fence according to claim 1, wherein the width of the downstream post is set to at least half the width of the upstream post.

6. 3. The trapping fence according to claim 1, wherein the downstream post is detachably attached to the upstream post.

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