Dam structure

Abstract

To provide a dam structure that, with a simple structure, can maintain good water flow function as a whole for the overhanging trapping body, and can effectively suppress the uplift of the main dam upstream when a debris flow occurs. [Solution] A weir structure 10 equipped with an overhanging trapping body 30, wherein the overhanging trapping body 30 is composed of one or more sets of intermediate trapping column units 30A and one or more sets of upstream trapping column units 30B, and the intermediate trapping column units 30A and upstream trapping column units 30B are arranged at predetermined intervals in the longitudinal and transverse directions of the river so that a continuous bypass passage that allows water flow can be formed inside the overhanging trapping body when a debris flow including driftwood occurs.

Description

Technical Field

[0001] The present invention relates to a dam structure that can be used for sediment capture works such as debris flows and floating logs, and floating log capture works in rivers.

Background Art

[0002] A general sand control dam includes a main body for blocking sediment, and a pair of sleeve portions formed at intervals on the main body so as to form a water passage portion (Patent Document 1). In this type of dam, when a debris flow occurs, floating logs clog the water passage portion and the water level rises, so it is easy for the floating logs to overflow over the sleeve portion of the dam together with the debris flow. In order to suppress the overflow of floating logs, it is known to increase the concrete on the existing dam to raise the sleeve portion, or to retroactively attach a floating log capture body in the expanded water passage portion. It is also known to use the deposited sediment on the upstream side of the dam and install a floating log capture body on the deposited sediment on the upstream side separated from the water passage portion (Patent Document 2). Furthermore, it is known to build an additional concrete base on the upstream wall surface of the dam and install a capture fence made of steel columns on this base, or to directly attach a capture fence made of steel columns to the upstream wall surface of the dam (Patent Documents 3, 4).

[0003] In the conventional countermeasures, the capture body or capture fence consists of a plurality of steel columns, and the plurality of steel columns are arranged in a horizontal row on the same line at a position separated from the upstream wall surface of the dam so as to surround the water passage portion, and the floating logs are captured by the capture body or capture fence before reaching the water passage portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] Conventional dams used for erosion control have the following problems: <1> For existing dams, measures such as raising the wing sections to improve driftwood capture performance, or adding driftwood capture devices to the water passages, require a significant amount of time and expense to implement. <2> In countermeasures involving the installation of trapping bodies in the sediment accumulated upstream of a dam, it takes several years for the upstream side of the dam to become completely filled with sediment. Therefore, in the case of sub-sand conditions where the accumulated sediment does not reach the required height, it is not possible to install the capture device, resulting in a lack of responsiveness. <3> Conventional trapping devices or trapping fences consist of multiple steel posts arranged horizontally at equal intervals along the same line. Therefore, when driftwood accumulates in the trap or trap fence, the opening becomes blocked, and then pebbles of various sizes fill the gaps between the driftwood, forming a watertight barrier that causes blockage. In particular, the wider the opening of the water-permeable section, the more likely it is that a water-impermeable barrier will form at an early stage. <4> As mentioned above, even if a trapping body or trapping fence is installed on the upstream side of the dam, a barrier with poor water permeability will ultimately be formed on the upstream side of the dam. When a water-impedance barrier forms upstream of a dam, the water loses its passage and driftwood overflows downstream through the dam's flank. <5> For a trapping device or trapping fence to function on the upstream side of a weir, the opening width of the water passage must be narrow, the weir must be raised by the side sections, and the upstream side of the main weir must be impounded. Conversely, if the opening width of the water passage is wide, the opening width for capturing driftwood will also be wide. As a result, the water passage capacity in the gap between the driftwood capture structure and the sleeve section will be relatively low, and if the opening of the water passage becomes clogged, it will cause a dam to form. In other words, conventional countermeasures that involve installing a trapping body or trapping fence on the upstream side of the weir are only effective in suppressing weir elevation when the opening width of the water passage is narrow. When the opening width of the water passage is wide, the effect of suppressing weir elevation is small, and driftwood overflow cannot be effectively suppressed.

[0006] The present invention aims to provide a dam structure that can solve the above-mentioned problems. [Means for solving the problem]

[0007] The present invention relates to a weir structure comprising a main dam having a water passage in the center and sleeves on both sides of the water passage, and an overhanging capture body fixed to the upstream wall of the main dam, wherein the overhanging capture body is composed of one or more sets of intermediate capture column units installed at predetermined intervals on the upstream side of the main dam, and one or more sets of upstream capture column units installed at predetermined intervals upstream of the intermediate capture column units, and the intermediate capture column units and the upstream capture column units are supported by support units attached to the upstream wall of the main dam, overhanging laterally. The support unit consists of a plurality of capture columns erected at predetermined intervals along the lateral direction of the river, and the distance from the upstream wall of the main embankment to the capture columns constituting the upstream capture column unit is greater than the distance from the upstream wall of the main embankment to the capture columns constituting the intermediate capture column unit, so that when a debris flow including driftwood occurs, a continuous bypass passage that allows water to flow inside the overhanging capture body can be formed, and the intermediate capture column unit and the upstream capture column unit are arranged at predetermined intervals in the longitudinal and lateral directions of the river. In another embodiment of the present invention, the intermediate capture column unit and the upstream capture column unit are arranged at predetermined intervals in the longitudinal and lateral directions of the river, in an uneven, concave, convex, or staggered pattern in a plan view. In another embodiment of the present invention, the multiple capture columns constituting the intermediate capture column unit and the upstream capture column unit are configured to be detachable from the support unit. In another embodiment of the present invention, multiple sets of the intermediate trapping column units, which are arranged in the lateral direction of the river, are spaced apart at intervals of 1 / 3 to 1 / 2 of the average driftwood length. In another embodiment of the present invention, multiple sets of the upstream capture column units, which are arranged in the lateral direction of the river, are spaced apart at intervals of 1 / 3 to 1 / 2 of the average driftwood length. In another embodiment of the present invention, the plurality of capture columns constituting the intermediate capture column unit and the upstream capture column unit are arranged at intervals of 1 / 3 to 1 / 2 of the average driftwood length. In another embodiment of the present invention, the arrangement of the multiple capture columns constituting the intermediate capture column unit and the upstream capture column unit is 2 to 7. In another embodiment of the present invention, the apparent water-permeable width of the overhanging capture body, obtained by adding the total distance of the multiple water-permeable separation sections formed between the main embankment, the capture column unit, and the intermediate capture column unit to the total length of the overhanging capture body which constitutes the overhanging capture body which has water permeability, is dimensionally at least twice the water-permeable width of the water-permeable section of the main embankment. In other embodiments of the present invention, the support unit may be a rigid frame structure made by combining a plurality of horizontal main beams projecting laterally from the upstream wall of the main embankment, a plurality of horizontal transverse beams intersecting between adjacent horizontal main beams, and diagonal members, etc. Alternatively, the support unit may be any one of a three-dimensional truss structure, a wall structure, or a cantilevered concrete base. [Effects of the Invention]

[0008] The present invention provides one of the following effects. <1> The intermediate and upstream capture column units of the overhanging capture structure, installed on the upstream wall of the main embankment, are arranged at predetermined intervals in the longitudinal and transverse directions of the river. Therefore, water can be channeled to the main dam's water-conducting section through a bypass passage formed inside the overhanging trapping body. Therefore, since good water flow function can be maintained for the entire overhanging trapping structure, it is possible to effectively suppress not only the weir on the upstream side of each trapping column unit, but also the weir on the upstream side of the main dam. <2> Since the overhanging trapping body is directly fixed to the upstream wall of the main dam, compared to conventional countermeasures where trapping bodies are erected in the accumulated sediment upstream of the dam, there is no need to wait until the upstream side of the dam is completely filled with sand, and the trapping function for driftwood and other debris can be performed even when the sand level is low. <3> By arranging the intermediate and upstream capture column units at predetermined intervals in the longitudinal and transverse directions of the river, each independent capture column unit complements the others, enabling efficient capture of driftwood. <4> By configuring the capture column to be detachable from the support unit, not only is the assembly of the capture column easier, but only the minimum number of damaged capture columns necessary can be replaced. <5> In conventional driftwood trapping structures, multiple steel columns are arranged at equal intervals along the same line. Therefore, if a significant decrease in water flow capacity occurs in one of these columns, the decrease in water flow capacity will cascade down the entire length of the driftwood trapping structure. In contrast, in this invention, since each capture column unit is spaced apart from each other, the water flow performance of each capture column unit due to the capture of driftwood does not affect each other. Therefore, even if some capture column units experience a significant decrease in water flow capacity, this decrease in water flow capacity will not affect other capture column units. <6> As driftwood is captured by each capture column unit, the cross-sectional diameter of the bypass passage formed within the protruding capture body narrows, but the Venturi effect causes the flow velocity within the bypass passage to become very high, pushing downstream any small and medium-sized pebbles, branches, leaves, and other driftwood that would otherwise remain within the bypass passage. Therefore, the detour route is less likely to become blocked, and good water flow through the detour route can be maintained for a long period of time. [Brief explanation of the drawing]

[0009] [Figure 1] Model diagram of the dam structure as seen from the upstream side, according to Example 1. [Figure 2] Plan view of the weir structure [Figure 3] Cross-sectional view taken along line III-III in Fig. 2 [Figure 4] Cross-sectional view taken along line IV-IV in Fig. 2 [Figure 5] Cross-sectional view taken along line V-V in Fig. 2 [Figure 6] Explanatory drawing of the form in which the support unit is formed by a concrete base [Figure 7] Plan view of the weir structure for explaining the trapping action of driftwood [Figure 8] Plan model drawing of the weir structure according to Example 2 in which side trapping columns are added to the overhanging trapping body [Figure 9A] Plan model drawing of the weir structure according to Example 3 in which the intermediate trapping column unit and the upstream trapping column unit are arranged in a concave shape [Figure 9B] Plan model drawing of the weir structure according to Example 3 in which the intermediate trapping column unit and the upstream trapping column unit are arranged in a convex shape [Figure 9C] Plan model drawing of the weir structure according to Example 3 in which the intermediate trapping column unit and the upstream trapping column unit are arranged in a staggered shape

Mode for Carrying Out the Invention

[0010] [Example 1] 1. Outline of the weir structure The weir structure 10 according to this example will be described with reference to Figs. 1 to 6 The weir structure 10 is a structure installed in a river to capture driftwood, earth and sand, gravel, etc. of debris flow, and includes a main dike 20 installed in the transverse direction of the river, and an overhanging capture body 30 fixed to the upstream wall surface 21 of the main dike 20 and provided so as to project upstream

[0011] In the following description, the longitudinal direction of the river (the penetrating direction of the main body 20) will be defined as the "longitudinal direction" or "front-back direction", and the transverse direction of the river (the longitudinal direction of the main body 20) will be defined as the "transverse direction" or "left-right direction" for explanation

[0012] 2. Main dike The main dam 20 is an impermeable dam body and has an upstream wall 21 and a downstream wall 22. Furthermore, the main embankment 20 has a water passage section 23 of a predetermined width in its central part, and a pair of sleeve sections 24 on both sides of the water passage section 23. In this example, we will describe a configuration where the main dam 20 is an existing weir, but the main dam 20 may also be a newly constructed weir.

[0013] 3. Driftwood overhang trap Referring to Figures 1-5, the overhanging trapping body 30 is fixed to the upstream wall 21 of the main embankment 20 and is a driftwood trapping fence that is integrally installed, separated from the upstream wall 21 on the upstream side.

[0014] <1> Overview of the protruding trap The overhanging capture body 30 consists of one or more sets of intermediate capture column units 30A installed at predetermined intervals on the upstream side of the main dam 20, and one or more sets of upstream capture column units 30B installed at predetermined intervals on the upstream side of the intermediate capture column units 30. The intermediate capture column unit 30A and the upstream capture column unit 30B are both positioned upstream of the main dam 20 and approximately parallel to the main dam 20.

[0015] The overhanging capture unit 30 is positioned upstream from the main dam 20 in the order of intermediate capture column unit 30A and upstream capture column unit 30B. The intermediate capture column unit 30A and the upstream capture column unit 30B, which constitute the protruding capture body 30, will be described in detail below.

[0016] <2> Configuration of the capture column unit The intermediate capture column unit 30A and the upstream capture column unit 30B consist of a support unit 35 attached to the upstream wall surface 21 of the main dam 20, extending laterally, and a plurality of capture columns 31 erected laterally at predetermined intervals at appropriate positions on the support unit 35, in a self-supporting manner.

[0017] The basic configuration of the intermediate capture column unit 30A and the upstream capture column unit 30B is the same, but the distance between the capture column 31 and the upstream wall 21 of the main dam 20 is different.

[0018] <2.1> Support Unit The support unit 35 is a support structure for supporting multiple capture columns 31 arranged in the horizontal direction.

[0019] The support unit 35 illustrated in Figures 1, 3 to 5 will be described below. The support unit 35 is a rigid frame structure manufactured by combining multiple horizontal main beams 32 projecting horizontally from the upstream wall 21 of the main dam 20, multiple horizontal crossbeams 33 intersecting between adjacent horizontal main beams 32, and diagonal members 34, etc. In this example, the capture columns 31 are configured to be inserted into each horizontal main beam 32, allowing the capture columns 31 to be replaced as needed.

[0020] The support unit 35 is not limited to this example and may be any of the following: a three-dimensional truss structure, a wall structure, a cantilevered concrete base, etc. Figure 6 illustrates an example of a cantilevered concrete support unit 35. In short, any structure that can be easily attached to the upstream wall 21 of the main dam 20 and that can support multiple capture columns 31 is sufficient. Considering cost-effectiveness and ease of construction, a rigid frame structure is preferable for the support unit 35.

[0021] <2.2> Capture Pillar The capture column 31 is a highly rigid column for capturing driftwood, and can be made of materials such as steel pipes, steel rods, filled steel pipes with a binding agent, or special filled steel pipes in which PC material is placed inside the steel pipe and then filled with a binding agent.

[0022] The capture column 31 has a total length capable of capturing driftwood, and its total length is at least equal to the water passage height that protrudes above the bottom level of the water passage section 23 of the main embankment 20.

[0023] In this example, we show a configuration in which the capture columns 31 are erected vertically at predetermined positions on each horizontal main beam 32 relative to the support unit 35. However, the capture columns 31 may also be erected in a forward-tilted or backward-tilted position at an appropriate angle.

[0024] <2.3> Spacing of capture posts Multiple capture columns 31 are arranged with a predetermined capture interval (separation distance) G1 between them. The capture interval G1 will be discussed later.

[0025] <2.4> Number of capture posts in the arrangement The number of capture columns 31 that make up the intermediate capture column unit 30A and the upstream capture column unit 30B can be selected as appropriate. In practical terms, each capture column unit 30A, 30B consists of approximately 2 to 7 capture columns 31. The number of capture posts 31 that make up each capture post unit 30A, 30B can be appropriately selected according to the site conditions.

[0026] <3> Arrangement configuration of each capture column unit In this example, we will describe a configuration in which the main embankment 20, the intermediate capture column unit 30A, and the upstream capture column unit 30B are arranged in an irregular (crank) shape in a plan view, with predetermined capture intervals (separation distances) G2 to G5 separating them from each other in the vertical (front-to-back) and horizontal (left-to-right) directions. In this example, we will describe a configuration in which, among the multiple capture columns 31 that make up each capture column unit 30A, 30B, only the terminal capture column 31 is positioned so that it overlaps with others along the river direction.

[0027] The intermediate capture column unit 30A and the upstream capture column unit 30B were separated and arranged in an uneven configuration in order to simultaneously achieve the following multiple objectives. [Reason 1] The purpose is to capture driftwood individually using each capture column unit 30A and 30B. [Reason 2] This is to form a bypass passage S inside the protruding capture body 30 when the water flow capacity of each capture column unit 30A, 30B decreases. [Reason 3] This is to prevent adverse effects on other capture column units 30A and 30B if the water flow capacity of some capture column units 30A and 30B decreases.

[0028] <3.1> Vertical spacing of each capture column unit Each capture column unit 30A and 30B constituting the overhanging capture body 30 is positioned parallel to each other and facing the main embankment 20, and is arranged in the order of intermediate capture column unit 30A and upstream capture column unit 30B from the main embankment 20 upstream.

[0029] In other words, the upstream wall 21 of the main dam 20 and the intermediate capture column unit 30A are separated by a capture interval G2, and the intermediate capture column unit 30A and the upstream capture column unit 30B are separated by a capture interval G3. The distance between the upstream wall 21 of the main dam 20 and the upstream capture column unit 30B is separated by a capture interval G6, which is the sum of the two capture intervals G2 and G3.

[0030] The two capture intervals G2 and G3 may be the same, but setting the capture interval G2 closer to the main embankment 20 to be narrower can suppress the inflow of driftwood into the water passage section 23 through the bypass passage S formed between the upstream wall 21 of the main embankment 20 and the intermediate capture column unit 30A.

[0031] <3.2> Horizontal spacing of intermediate capture column units Multiple sets of intermediate trapping column units 30A are intermittently positioned along the lateral direction. The intermediate capture column units 30A, which are arranged horizontally, are spaced apart by a predetermined capture interval G4.

[0032] <3.3> Horizontal spacing of upstream capture column units Multiple sets of upstream capture column units 30B are intermittently positioned along the lateral direction. The upstream capture column units 30B, which are arranged horizontally, are also spaced apart by a predetermined capture interval G5.

[0033] <3.4> Interval for capturing driftwood The capture intervals G1 to G5 described above represent distances at which driftwood can be captured while restricting its easy passage, and are 1 / 3 to 1 / 2 the length of the driftwood. For example, if the average length of driftwood is 5-10m, then the intervals between captures G1-G5 will be 2.5-5m.

[0034] <3.5> Relationship between driftwood capture intervals and detour paths Each of the capture intervals G2 to G5 described above affects the formation of the bypass passage S, which will be described later, and the width of the bypass passage S widens according to each of the capture intervals G2 to G5. Therefore, the capture intervals G2 to G5 described above are not limited to the dimensional examples shown above, but should be appropriately selected considering the expected maximum amount of driftwood to be captured by each capture column unit 30A, 30B.

[0035] <4> Number of horizontal rows for each capture column unit The number of horizontal rows of intermittently arranged capture column units 30A and 30B can be appropriately selected according to the width dimension of the water passage section 23 of the main embankment 20.

[0036] <4.1> Number of horizontal rows of intermediate capture column units Multiple intermediate trapping column units 30A have at least a number of horizontal rows that can traverse the water passage section 23 of the main dam 20. In this example, two sets of intermediate capture column units 30A are shown in a horizontal arrangement on the upstream side of the water passage section 23 of the main dam 20. However, the intermediate capture column units 30A may be arranged in a single set, or in a set of three or more sets.

[0037] <4.2> Number of horizontal rows of upstream capture column units Multiple upstream capture column units 30B have at least a number of horizontal rows that can traverse across the water passage section 23 and the sleeve section 24 of the main dam 20. In this example, a configuration is shown in which three sets of upstream capture column units 30B are arranged horizontally across the water passage section 23 and the side section 24 of the main dam 20. However, the configuration may also include one set of upstream capture column units 30B, or four or more sets.

[0038] <5> detour passage As previously described, in the present invention, each capture column unit 30A, 30B is arranged in an uneven pattern in a plan view, with intervals between them in the horizontal and vertical directions, respectively. The reason for arranging each capture column unit 30A, 30B in an uneven configuration is to form a continuous bypass passage S that allows water flow between adjacent capture column units 30A, 30B in the front-back, left-right, and right directions, and between the main embankment 20 and the intermediate capture column unit 30A, without impairing the driftwood capture function.

[0039] <5.1> Function of detour routes As previously described, the purpose of forming the detour passage S is to ensure the overall water flow capacity of the overhanging capture body 30, even if the water flow capacity of each capture column unit 30A, 30B decreases, thereby effectively suppressing the occurrence of weir formation.

[0040] <5.2> Locations where detours are formed In this example, a series of continuous bypass passages S are formed between the interior of the overhanging trapping body 30 and the main embankment 20, as shown below. 1) Between the intermediate capture column unit 30A and the upstream capture column unit 30B, which are adjacent to each other in the longitudinal direction of the river. 2) Between the upstream wall 21 of the main dam 20 and the intermediate capture column unit 30A, which are adjacent to each other in the longitudinal direction of the river.

[0041] 3) Between two adjacent upstream capture column units 30B in the lateral direction of the river. 4) Between two adjacent intermediate capture column units 30A in the lateral direction of the river.

[0042] The number of detour paths S increases according to the number of intermediate capture column units 30A or upstream capture column units 30B installed.

[0043] <6> Apparent water passage width in the protruding trap The upstream capture column unit 30A and the intermediate capture column unit 30B, which constitute the aforementioned overhanging capture body 30, have water permeability throughout their entire length. Furthermore, water is permeable across the total distance between each of the aforementioned capture column units 30A and the intermediate capture column unit 30B, at multiple points of separation. In this invention, the range obtained by adding the total distance of the multiple separation points mentioned above to the total length of the upstream capture column unit 30A and the intermediate capture column unit 30B is defined as the "apparent water passage width of the overhanging capture body."

[0044] The inventors conducted various experiments regarding the relationship between the "apparent water passage width of the overhanging trapping body" and the actual water passage width in the water passage section 23 of the main dam 20, in relation to suppressing the uplift of the weir structure 10.

[0045] As a result, we learned that in order to obtain the effect of suppressing weir rise, it is necessary to ensure that the "apparent water passage width of the overhanging trapping body" is at least twice the length of the actual water passage width in the water passage section 23 of the main dam 20. In this invention, instead of arranging the multiple capture columns 31 in a horizontal line at equal intervals, the multiple capture columns 31 are arranged in an uneven pattern, thereby ensuring a longer apparent water passage width.

[0046] 4. The trapping effect of dam structures Referring to Figure 6, the debris flow trapping function of the dam structure 10 will be explained.

[0047] <1> Installation of an overhanging trap on the main embankment As previously described, an overhanging trapping body 30 capable of capturing driftwood, sediment, etc., will be installed on the upstream wall 21 of the existing main dam 20. In this invention, the overhanging trapping body 30 is directly installed on the upstream wall 21 of the main dam 20. Compared to conventional countermeasures that involve erecting trapping bodies in the accumulated sediment upstream of a dam, the overhanging trapping body 30 can be installed in a sub-sand condition.

[0048] <2> The trapping effect of the main embankment. Debris flows, including driftwood, that are flowing down the river are dammed upstream of the main dam 20. Sediment and gravel settle under their own weight and accumulate on the upstream side of the main dam 20. When the debris flow is dammed by the main dam 20, the water level upstream of the main dam 20 rises, and once it exceeds a certain level, the water flows downstream through the water passage section 23.

[0049] <3> Capture action by the protruding capture body Referring to Figure 6, the trapping action of the protruding trapping body 30 on driftwood W will be explained. Upstream of the main dam 20, an overhanging trapping body 30 covers part of the water passage section 23 and the sleeve section 24. When the water level of the debris flow rises, the overhanging trapping body 30 functions as follows.

[0050] <3.1> Capture of driftwood by capture column unit The driftwood W separates from the debris flow and floats on the water surface as it drifts downstream. The driftwood W that reaches the overhanging capture body 30 is blocked by multiple capture columns 31 that make up the intermediate capture column unit 30A and the upstream capture column unit 30B, which are located in front of and behind it.

[0051] In this invention, instead of arranging multiple capture pillars 31 in a horizontal line at equal intervals on the upstream side of the main dam 20, multiple unitized capture pillars 31 are arranged unevenly with spacing in the vertical and horizontal directions (front, back, left, and right directions).

[0052] Therefore, driftwood W flowing downstream toward the overhanging capture body 30 is captured before it is captured by the multiple upstream capture column units 30A installed at the uppermost position. Some of the driftwood W that could not be captured by each upstream capture column unit 30A flows downstream through the channels formed between the upstream capture column units 30A which are arranged at intervals, and the driftwood W that flows downstream is captured by the intermediate capture column unit 30B located downstream of the upstream capture column unit 30A. Furthermore, driftwood W flows down outside the upstream capture column unit 30A and enters the channel formed between the two capture column units 30A and 30B, and this driftwood W is also captured by the intermediate capture column unit 30B. In this way, the separate and independent capture column units 30A and 30B complement each other and efficiently capture driftwood W, thereby suppressing blockage in the water passage section 23 of the main embankment 20 caused by driftwood W.

[0053] <3.2> Regarding the water permeability of the driftwood trapping structure The water permeability of the conventional driftwood capture system and the driftwood capture system of the present invention will be explained in comparison below.

[0054] <3.2.1> Conventional driftwood capture methods In conventional driftwood trapping structures, where multiple steel pillars are lined up at equal intervals on the same line upstream of a weir, if the opening width of the water passage becomes wider than a certain point, the water passage capacity of the driftwood trapping structure decreases, causing the water to lose its escape route and resulting in premature weir formation. Furthermore, in conventional driftwood trapping structures, multiple steel columns are arranged at equal intervals along the same line. Therefore, if a significant decrease in water flow capacity occurs in one of these columns, the decrease in water flow capacity will cascade down the entire length of the driftwood trapping structure.

[0055] <3.2.2> The driftwood capture method of the present invention In contrast, in the present invention, even if the capture of driftwood W progresses and the water flow capacity of each capture column unit 30A, 30B decreases, a bypass passage S is formed inside the protruding capture body 30, so the water flow function of the protruding capture body 30 as a whole is not significantly impaired. The water flow function through the bypass passage S will be explained below.

[0056] <3.3> Water diversion via bypass routes If the water flow capacity of each capture column unit 30A, 30B decreases, a continuous bypass passage S is formed around the intermediate capture column units 30A and the upstream capture column unit 30B, which are arranged in an uneven pattern in plan view with intervals between them. Even if the water flow capacity of each capture column unit 30A, 30B decreases, the bypass passage S guides the water flow through the spaces between each capture column unit 30A, 30B toward the water passage section 23. Therefore, since the overall water flow function of the overhanging trapping body 30 can be maintained, not only the weir on the upstream side of each trapping column unit 30A, 30B but also the weir on the upstream side of the main dam 20 can be effectively suppressed.

[0057] In particular, as driftwood W is captured by each capture column unit 30A, 30B, the cross-sectional diameter of the bypass passage S formed within the protruding capture body 30 is narrowed. Even if the cross-sectional diameter of the bypass passage S is narrowed, the flow velocity of the water becomes very high due to the Venturi effect as it passes through the bypass passage S. Therefore, small and medium-sized gravel, branches, leaves, and other debris that would otherwise remain in the detour passage S are swept away and pass through, making it less likely for the detour passage S to become blocked.

[0058] Furthermore, since the capture column units 30A and 30B are spaced apart from each other, the water flow performance of each capture column unit 30A and 30B due to the capture of driftwood W does not affect each other. Therefore, even if some of the capture column units 30A and 30B experience a significant decrease in water flow capacity, it will not affect the other capture column units 30A and 30B.

[0059] In this way, the uplift of the main dam 20 on the upstream side can be effectively suppressed, and compared to conventional dams, the effect of preventing the overflow of debris flows, including driftwood W, through the water passage section 23 and the sleeve section 24 of the main dam 20 can be sustained for a long period of time.

[0060] [Example 2] Other embodiments of the protruding capture body 30 will be described below, but in that description, the same parts as in the above embodiments will be denoted by the same reference numerals and their detailed descriptions will be omitted.

[0061] <1> A configuration in which lateral capture columns are added to the protruding capture body. In the previous embodiment, the left and right lateral spaces of the overhanging trapping body 30 are widely open, and there is a risk that driftwood W may flow into the water passage section 23 of the main embankment 20 through these lateral openings. In such cases, as shown in Figure 8, a lateral capture column 31 may be added between the outermost upstream capture column unit 30B that constitutes the overhanging capture body 30 and the capture column 31 at its terminal. As for the method of erecting the lateral capture column 31, for example, the erection configuration shown in Figure 5 can be applied.

[0062] <2> The effect of this example In this embodiment, in which lateral capture columns 31a are added and erected on the left and right sides of the overhanging capture body 30, it becomes possible to effectively suppress the inflow of driftwood through the spaces on the left and right sides of the overhanging capture body 30, and the effect of suppressing the inflow of driftwood into the water passage section 23 of the main embankment 20 is higher compared to Embodiment 1.

[0063] [Example 3] <1> Other configuration examples of intermediate and upstream capture column units In the above embodiment, a configuration was described in which the intermediate capture column unit 30A and the upstream capture column unit 30B were arranged in an uneven concave-concave pattern in a plan view. However, the arrangement of each capture column unit 30A, 30B may also be in a concave, convex, or staggered pattern, as will be described below. In any configuration, the number of capture columns 31 constituting the intermediate capture column unit 30A and the upstream capture column unit 30B can be selected as appropriate.

[0064] Figure 9A shows a configuration in which one set of intermediate capture column units 30A and two sets of upstream capture column units 30B are arranged in a concave shape. Figure 9B shows a configuration in which two sets of intermediate capture column units 30A and one set of upstream capture column units 30B are arranged in a convex shape. Figure 9C shows a configuration in which multiple sets of intermediate capture column units 30A and multiple sets of upstream capture column units 30B are arranged in a staggered pattern.

[0065] <2> The effect of this example In this example, the optimal arrangement can be selected from a range of concave, convex, or staggered arrangements, depending on the opening width of the water passage section 23 of the main embankment 20 and the expected amount of driftwood. [Explanation of symbols]

[0066] 10. Dam structure 20... Main embankment 21. Upstream wall of the main dam 22. Downstream wall of the main dam 23. Water passage section of the main dam 24...The wing section of the main embankment 30...Protruding capture unit 30A...Intermediate capture pole unit 30B... Upstream capture column unit 31·····Capture Pillar 31a... Lateral capture column 32...Horizontal main beam 33...Horizontal crossbeam 34... diagonal material 35·····Support Unit W······driftwood

Claims

1. A dam structure comprising a main dam having a water passage in the center and sleeves on both sides of the water passage, and an overhanging trapping body fixed to the upstream side of the upstream wall of the main dam, The aforementioned overhanging capture body comprises one or more sets of intermediate capture column units installed at predetermined intervals on the upstream side of the main dam, It consists of one or more sets of upstream capture column units installed at predetermined intervals upstream of the aforementioned intermediate capture column unit, The aforementioned intermediate capture column unit and upstream capture column unit are supported by a support unit that is attached to the upstream wall of the main dam, extending laterally. The aforementioned support unit consists of multiple capture columns erected at predetermined intervals along the lateral direction of the river, The distance from the upstream wall of the main dam to the capture column constituting the upstream capture column unit is greater than the distance from the upstream wall of the main dam to the capture column constituting the intermediate capture column unit. The intermediate trapping column unit and the upstream trapping column unit are arranged at predetermined intervals in the longitudinal and transverse directions of the river, so as to be able to form a continuous bypass passage that allows water flow inside the overhang trapping body when a debris flow containing driftwood occurs. Dam structure.

2. The weir structure according to claim 1, characterized in that the intermediate capture column unit and the upstream capture column unit are arranged in an uneven manner in a plan view at predetermined intervals in the front-to-back and left-to-right directions of the river.

3. The weir structure according to claim 1, characterized in that the intermediate capture column unit and the upstream capture column unit are arranged in a concave or convex shape in a plan view at predetermined intervals in the front-to-back and left-to-right directions of the river.

4. The weir structure according to claim 1, characterized in that the intermediate capture column unit and the upstream capture column unit are arranged in a staggered pattern in a plan view at predetermined intervals in the front-to-back and left-to-right directions of the river.

5. The dam structure according to claim 1, characterized in that it forms a continuous bypass passage through the following multiple spatial areas. 1) Between the upstream wall of the main embankment and the upstream capture column unit, which are adjacent to each other in the longitudinal direction of the river. 2) Between the upstream wall of the main embankment and the intermediate capture column unit, which are adjacent to each other in the longitudinal direction of the river. 3) Between adjacent upstream capture column units in the lateral direction of the river. 4) Between adjacent intermediate capture column units in the lateral direction of the river.

6. The weir structure according to claim 1, characterized in that the plurality of capture columns constituting the intermediate capture column unit and the upstream capture column unit are detachable from the support unit.

7. The weir structure according to claim 1, characterized in that multiple sets of intermediate capture column units arranged in the lateral direction of the river are spaced apart at intervals of 1 / 3 to 1 / 2 of the average driftwood length.

8. The weir structure according to claim 1, characterized in that multiple sets of the upstream capture column units, which are arranged in the lateral direction of the river, are spaced apart at intervals of 1 / 3 to 1 / 2 of the average driftwood length.

9. The weir structure according to claim 1, characterized in that the plurality of capture columns constituting the intermediate capture column unit and the upstream capture column unit are arranged at intervals of 1 / 3 to 1 / 2 of the average driftwood length.

10. The weir structure according to claim 1, characterized in that the arrangement of the plurality of capture columns constituting the intermediate capture column unit and the upstream capture column unit is 2 to 7.

11. The weir structure according to claim 1, characterized in that the apparent water passage width of the overhanging capture body, obtained by adding the total distance of the multiple water-permeable separation sections formed between the main weir, the capture column unit and the intermediate capture column unit to the total length of the overhanging capture body which constitutes the overhanging capture body which has water permeability, is at least twice the water passage width of the water passage section of the main weir.

12. The dam structure according to claim 1, characterized in that the support unit is a rigid frame structure manufactured by combining a plurality of horizontal main beams projecting horizontally from the upstream wall of the main dam, a plurality of horizontal transverse beams intersecting between adjacent horizontal main beams, and diagonal members, etc.

13. The dam structure according to claim 1, characterized in that the support unit is one of a three-dimensional truss structure, a wall structure, or a cantilevered concrete base.

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