JP7212581B2 - Debris flow sedimentary work - Google Patents

Description

The present invention relates to debris flow deposition work.

Conventionally, the Ministry of Land, Infrastructure, Transport and Tourism has indicated a debris flow deposition area and a debris flow deposition channel as a debris flow and driftwood countermeasure facility for reducing the force of a debris flow and depositing it in the Technical Guidelines for Countermeasures against Debris Flow and Driftwood.

FIG. 8(a) shows a debris flow deposition site 40, which is formed by providing a widened portion (area of land where the flow path is widened) 41 in the middle of the flow path, and upstream and downstream ends of the widened section 41, respectively. An end erosion control dam 42 and a downstream end erosion control dam 43 are arranged, and if necessary, a floor consolidation work 44 is arranged in the middle in the upstream and downstream directions.

The debris flow deposition site 40 secures a space for depositing the amount of deposition necessary for the debris flow/driftwood treatment plan by widening and digging the channel to make the slope of the river bed gentle.

Fig. 8(b) shows a debris flow deposition channel 45, but it is difficult to widen the channel like the debris flow deposition site 40 due to land use conditions such as the development of residential land in the background ground and topographical conditions such as valley bottom plains. In such a case, the channel is dug to make the slope of the stream bed 46 gentler than the original slope of the stream bed 47, thereby sedimenting the sediment 48 and accumulating the amount of deposition necessary for the debris flow/driftwood treatment plan. It is intended to secure a space that can be used.

In addition, on slopes where erosion control facilities such as sabo dams are installed to dam debris flows, sabo dams should be installed so as to cross the flow of the debris flow itself, and upstream of the sabo dams. , a configuration in which a plurality of weirs are arranged in a plurality of stages for trapping the debris flow at the front end of the initial movement of the debris flow is known (see Patent Document 1).

JP-A-2001-207431

In the debris flow deposit 40, when the sediment flows into the sedimentation work from the upstream channel, it is deposited by the momentum of the sediment flow, so even if it is deposited near the inlet or toward the outlet, it will be dispersed in the width direction. Therefore, the sediment does not spread all over the debris flow deposition area 40, and even if the sediment is widened to store a large amount of sediment, the sediment does not accumulate within that width. , is a concern.

That is, the debris flow deposition site 40 deposits sediment along a slope from the inlet to the outlet, but since it spreads from the inlet to the widened portion 41, the tractive force is reduced and the sediment is deposited at the inlet. Since it accumulates in the vicinity or in the center and does not accumulate in the entire area, it is not possible to obtain a trapping effect that makes full use of the scale of the facility.

The debris flow deposition channel 45 or the one shown in Patent Document 1 is not particularly widened, so the amount of deposited debris is limited, and the frequency of removal of debris increases.

In addition, the technique shown in Patent Document 1 is intended to capture the debris flow at the tip of the initial movement of the debris flow when a debris flow occurs, and is not intended to capture a large amount of debris by guiding and diffusing it in the width direction of the river. .

An object of the present invention is to solve the problems of the conventional debris flow sedimentation work, etc., and to realize a debris flow sedimentation work that can effectively capture the sediment of the debris flow and deposit a larger amount. Make it an issue.

In order to solve the above problems, the present invention is constructed in the middle of a river, has a recessed structure, and has an inlet at an upstream end and an outlet at a downstream end. is wider than the width of the river, and has a bottom and a peripheral wall that surrounds the bottom except for the inlet and outlet. In the recessed structure, from the exit side to the entrance side, flow contraction work, slitting work and dispersing work are arranged in order, and the slitting work and dispersing work is formed lower than the height of the peripheral wall, and the flow contraction work consists of a pair of projections formed facing each other on both sides of the flow channel work,
The slits are provided on both the left and right sides of the channel in the width direction, and are formed as weirs with slits, respectively. To provide a debris flow sedimentation work characterized in that it is configured as follows.

A configuration in which a blocking wall member is arranged between the slits formed on the left and right sides may be adopted.

The plurality of pairs of distributed structures may be arranged in a V-shape toward the upstream side in a plan view.

The inlet section and the outlet section may have an inlet wall and an outlet wall formed continuously with the peripheral wall section at the upstream end and the downstream end of the peripheral wall section, respectively.

The bottom, peripheral wall, inlet wall, and outlet wall may each be made of concrete.

The bottom may be horizontally or downwardly slanted from upstream to downstream.

According to the debris flow sedimentation work according to the present invention, a recessed structure widened to the river is provided, a channel is provided in the center of the recessed structure, and the recessed structure is gradually contracted from the outlet side to the inlet side. By arranging stream work, slit work, and dispersion work, in normal times or during medium and small floods, the flow is contracted by the contraction work, and even if the weir is raised, the flow is contracted by the contraction work through the slit work, and the channel is temporarily channeled. The sediment deposited in the dam will gradually flow downstream to restore the function of accumulating the silt. are dispersed and deposited over a wide area to accommodate a greater amount of sediment.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the Example of the debris flow deposition work based on this invention, (a) is a top view, (b) is AA sectional drawing in (a). (a) is a front view of the embodiment seen from the downstream side, and (b) is a perspective view showing an example of a piling work. FIG. 4 is a diagram for explaining the normal operation of the above embodiment, where (a) is a plan view and (b) is a cross-sectional view taken along the line AA in (a). It is a top view explaining the effect|action of the said Example at the time of the medium and small amount of water. 4A is a cross-sectional view taken along the line AA in FIG. 4, and FIG. 4B is a diagram for explaining the operation of the above-described embodiment when water is flowing to a medium or small level, and FIG. It is sectional drawing which shows a state. FIG. 4 is a diagram for explaining the action of the above embodiment during a flood, and is a plan view showing a state in which earth and sand have accumulated up to the height of the slit. FIG. 6 is a diagram for explaining the action of the above embodiment during a flood, where (a) is a cross-sectional view for explaining the process of depositing earth and sand, and (b) is FIG. 1 is a cross-sectional view taken along line AA of FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a conventional technique, (a) is a perspective view of a debris flow deposition site as an example of the prior art, and (b) is a cross-sectional view of a debris flow deposition channel as another example of the prior art.

A mode for carrying out the debris flow deposition work according to the present invention will be described below with reference to the drawings based on an embodiment.

(Example)
An embodiment of the debris flow deposition work according to the present invention will be described with reference to FIGS. 1 to 7. FIG. In this specification, the direction from upstream to downstream of the river is referred to as the upstream/downstream direction, and the direction orthogonal to the upstream/downstream direction of the river is referred to as the width direction. Moreover, the left-right direction toward the downstream is referred to as the left-right direction.

First, the configuration of this embodiment will be described with reference to FIGS. 1 and 2. FIG. The debris flow deposition work 1 of this embodiment is formed in the middle of a river along the flow of the river, and as shown in FIG. It has a recess structure 2 .

As shown in FIG. 1, in this embodiment, the recessed structure 2 is elongated from upstream to downstream and has a rectangular shape in plan view. Other shapes such as an ellipse, an elongated hexagon, etc. may be used as long as they are wider than the river.

The recess structure 2 has a bottom 3 and a peripheral wall 4 surrounding the bottom 3 . The bottom part 3 is made of concrete, but it may be covered with stones, nets, etc., or may be made of other materials.

Although this bottom 3 is described as being horizontal in the upstream and downstream directions in FIG. It is formed with a slope so that it slopes downward from upstream to downstream according to the momentum of the flow, the amount of water, etc. For example, if the original riverbed slope is large, the slope of the bottom 3 is increased, or conversely, the slope is decreased.

In this embodiment, the peripheral wall portion 4 is an inclined wall inclined downward toward the bottom portion 3, but it may be a vertical wall. The peripheral wall portion 4 is made of concrete and is continuous with the bottom portion 3. However, it may be made of other materials such as stones piled up or surrounded by a net, or the soil may be excavated. may be used as the peripheral wall portion of the

An inlet section 8 and an outlet section 9 are formed at the upstream end and the downstream end of the debris flow deposition work 1 . Left and right inlet walls 10 and outlet walls 11 are formed in the inlet portion 8 and the outlet portion 9, respectively, and are continuous with the upstream end and the downstream end of the peripheral wall portion 4, respectively.

The inlet wall 10 and the outlet wall 11 are also inclined walls in this embodiment, but they may be vertical walls. In the present embodiment, the entrance wall 10 and the exit wall 11 are made of concrete, similar to the surrounding wall 4. However, stones may be piled up or surrounded by a net. , etc., or the entrance wall and the exit wall may be formed by excavating soil.

A channel 12 is formed in the center of the bottom portion 3 in the width direction, and is formed as a groove from upstream to downstream. As shown in FIG. 2(a), the channel 12 is formed with side walls 13 on both left and right sides in the width direction. good.

At the entrance portion 8 and the exit portion 9 of the debris flow deposition work 1, the downstream end of the entrance wall 10 and the upstream end of the exit wall 11 are connected to the upstream end and the downstream end of the side wall 13 of the channel work 12, respectively.

In the debris flow deposition work 1, a flow contraction work 17 is formed in the vicinity of the downstream end (near the exit portion 9), as shown in FIGS. The flow contraction work 17 is composed of a pair of protrusions 18 provided so as to protrude from the side walls 13 on both the left and right sides of the flow channel work 12, respectively. It is formed narrower than the horizontal width s of 12.

In the debris flow deposition work 1, near the downstream end (near the outlet 9) and upstream of the flow contraction work 17, a pair of slit works 21 are provided symmetrically on both left and right sides of the flow channel work 12. ing. The slitting 21 is configured as a weir having a slit 22 . Although the slit 21 is made of concrete in this embodiment, it may be made of steel (steel plate, steel pipe, etc.) or other materials instead of concrete.

In this embodiment, the slit 21 has a trapezoidal cross section perpendicular to the width direction as shown in FIG. It has a slit 22 penetrating in the upstream and downstream directions at the central portion in the width direction.

The width of the slit 22 will be explained later in the description of the operation, but in normal times, if the flowing water of the debris flow is contracted by the flow contraction work 17 (the horizontal width of the flowing water is narrowed to flow), the upstream is dammed up and the water depth is increased. It is designed so that even if it rises, it will flow through the slit 22 so that the depth of the water can be kept within the channel 12 .

Although the slits 22 are not essential, by providing the slits 22, a part of the debris flow is allowed to flow through the slits 22, thereby reducing the overflow that tends to occur when there are no slits. can be prevented.

The gaps between the slits 21 on both the left and right sides of the channel 12 are closed with a closing wall member 23 . The blocking wall material 23 has a height that does not exceed the height of the debris flow deposition work 1, that is, the height of the peripheral wall 4, and may be a member such as a panel (plate material) that completely impermeable to the debris flow. , fences, grids, etc., which are not completely impermeable.

In addition, in this embodiment, the slits 21 on both the left and right sides are provided on both the left and right sides (a pair of left and right) with the flow channel 12 interposed therebetween. That is, depending on the gradient of the bottom portion 3, the amount of water, etc., a plurality of units (a plurality of pairs of left and right) may be provided on each of the left and right sides.

For example, if the bottom 3 has no slope or is relatively flat, one unit may be used as in this embodiment. A pair may be provided.

In the debris flow deposition work 1, as shown in FIG. 25 are arranged in a V-shape toward the upstream side in a plan view.

The dispersion work 25 serves as a guide against the debris flow, and moves the soil from the center in the width direction so as to guide it in the left-right direction so that it spreads in the width direction, so that the soil moves to the center in the width direction. It has a function of suppressing concentrated deposition in the debris flow deposition work 1 and dispersing and depositing it over a wide range of the debris flow deposition work 1, making it possible to receive a larger amount of soil.

In this embodiment, the distributed work 25 is made of concrete, and has a structure in which a plurality of trapezoidal discs are continuously projected upward as shown in FIGS. 1(a) and 2(b). However, the material of the dispersed work 25 may be steel material, embankment, etc., and the structure thereof may be fences, blocks, or the like.

Furthermore, the shape of the dispersal work 25 is diverse, such as rectangular or circular in plan view, or their arrangement and combination. It can be selected as appropriate. The height of the dispersing work 25 is set so as not to exceed the height of the debris flow sedimentation work 1, that is, the height of the peripheral wall portion 4. However, if it is too low, the effect of dispersing earth and sand will be reduced.

(Action)
The configuration of the embodiment of the debris flow deposition work 1 according to the present invention has been described above. It is explained below.

Normal time:
In normal times, the debris flow water 28 flowing in the river enters the debris flow deposition work 1 from the inlet 8 and flows through the channel work 12 as shown in FIGS. 3(a) and 3(b). Then, the earth and sand of the debris flow are carried downstream from the channel construction 12 in the center of the debris flow deposition work 1 by running water 28 .

In normal times, the amount of water flowing through the river slightly increases, and the stream 28 is contracted by the flow contraction work 17, so that if the upstream side rises and the water depth rises in the channel work 12, the bottom 3 is flooded. However, by passing through the slit 22 of the slit 21, the water depth is kept within the channel 12. - 特許庁

In other words, even if the amount of water in the debris flow increases slightly and the water depth in the channel work 12 rises on the upstream side, the flowing water stays in the channel work 12 and passes through the contraction work 17. The width of the slit 22 of the slitter 21 is set so as to flow.

Medium and small flood:
Here, "medium and small floods" are floods that have a larger amount of water flowing through the river than normal, but are not large enough to cause flooding. 5 to 1/30 probability flood).

4 and 5(a), the flowing water 28 is contracted by the flow contraction work 17, so that the inside of the channel work 12 is dammed up and the inside of the channel work 12 is flooded. to water When the bottom 3 is flooded, the running water 28 of the debris flow passes through the slit 22 of the slit 21 and flows downstream.

During a medium or small flood, the sediment 29 of the debris flow gradually sediments (accumulates) from upstream to downstream in the flooded water 30 of the channel 12, as shown in FIGS. 4 and 5(a). To go. The head of this sedimentation (downstream end of the sedimentation) is called a sedimentation shoulder 33 .

When the sedimentation shoulder 33 does not reach the position of the slit 21 (see FIG. 5(a)), the sediment 29 accumulated in the channel 12 is removed by the flow of water in the latter half of normal times or floods. As shown in (b), it is gradually eroded and flowed downstream. Therefore, the channel 12 recovers the function of the channel 12 again.

Flood time:
During a flood, the debris flow flowing in the river enters the debris flow deposition work 1 from the inlet 8, flows through the channel work 12, and the flowing water 28 is contracted by the flow contraction work 17 and overflows the channel work 12, as shown in FIG. As shown in FIG. 7(a), the slit work 21 is also dammed up, and the upstream side of the debris flow deposition work 1 is gradually flooded.

Even if the sedimentation work is flooded, the sediment 29 of the debris flow is sedimented from a low place, so it progresses downstream while forming a sedimentation shoulder 33 within the channel work 12 . In such a state, as shown in FIGS. 6 and 7(a), the upstream side of the slit 21 in the recess structure 2 becomes a wide flooded pond.

By the way, if the progress of the sedimentation shoulder 33 to the downstream side is left to nature, in the configuration of the debris flow dispersal sedimentation pond shown in FIG. There is a tendency for deposits to be concentrated in the center of the width direction within the deposition work.

However, in the debris flow deposition work 1 of the present invention, as shown in FIG. The dispersion work 25 directs the sedimentation shoulder 33 from the inlet 10 toward the downstream side, guides and spreads the sediment 29 in the downstream direction to the left and right, and the sediment 29 accumulates over a wide range of the recessed structure 2. be done.

Then, when the sedimentation shoulder 33 reaches the position of the slit 21 and the sediment 29 accumulates up to the height of the slit 21, as shown in FIG. The water overflows the wall material 23, flows into the channel work 12 on the downstream side, and flows downstream of the river from the outlet 9 of the debris flow deposition work 1. - 特許庁

In this way, according to the debris flow deposition work 1 according to the present invention, even in the event of a flood, the wide space of the widened recess structure 2 of the debris flow deposition work 1 is effectively utilized in the width direction, and a large amount of of sediment can be deposited, it is possible to effectively suppress the movement of sediment, debris, driftwood, etc. in a debris flow during a flood.

If the amount of sediment is less than the flow rate of the debris flow flowing into the debris flow deposition work 1 and the sedimentation shoulder 33 does not reach the slit work 21, the sediment will gradually erode and move downstream, as in the case of medium and small floods. Then, the debris flow deposition work 1 recovers to the normal state.

Although the embodiment for carrying out the debris flow deposition work according to the present invention has been described above, the present invention is not limited to such an embodiment, and the technology described in the claims. It goes without saying that there are various embodiments within the scope of the technical matters.

Since the debris flow sedimentation work according to the present invention is configured as described above, it can be applied to rivers in mountainous areas, etc., where both sides of the river have ample space.

1 Debris flow deposition work 2 Recess structure 3 Bottom part 4 Surrounding wall part 8 Entrance part 9 Exit part 10 Entrance wall 11 Exit wall 12 Channel work 13 Side wall of channel work 17 Flow contraction work 18 Protrusion of flow contraction work 21 Slit work 22 Slit of slit work 23 Blocking wall material 25 Distributed work 28 Flowing water 29 Earth and sand 30 Flooding 33 Sedimentation shoulder 40 Debris flow deposition area 41 Widening part 42 Upstream end erosion control dam 43 Downstream end erosion control dam 44 Consolidation work 45 Debris flow deposition channel 46 Streambed 47 Original streambed gradient

Claims (6)

A debris flow deposition work constructed in the middle of a river, having a recessed structure, and having an inlet at an upstream end and an outlet at a downstream end,
The recess structure is wider than the width of the river and has a bottom and a peripheral wall surrounding the bottom except for the entrance and exit,
At the center of the bottom in the width direction, there is a groove formed as a groove from upstream to downstream,
In the recess structure, a flow contraction work, a slit work and a dispersion work are arranged in order from the exit side to the entrance side, and the slit work and the dispersion work are all formed lower than the height of the peripheral wall,
The flow contraction work consists of a pair of protrusions formed opposite each other on both sides of the flow channel work,
The slits are provided on both left and right sides of the channel in the width direction, and are formed as weirs each having a slit,
Debris flow sedimentation work is characterized in that the distributed works are formed so as to protrude upward in a plurality of pairs on both the left and right sides of the channel work. 2. The debris flow sedimentation work according to claim 1, wherein a blocking wall material is arranged between the slits formed on the left and right sides. 3. The debris flow sedimentation work according to claim 1 or 2, wherein the plurality of pairs of distributed works are arranged in a V shape toward the upstream side in a plan view. 4. Any one of claims 1 to 3, wherein the inlet portion and the outlet portion are formed with an inlet wall and an outlet wall formed continuously with the peripheral wall portion at the upstream end and the downstream end of the peripheral wall portion, respectively. Debris flow sedimentation described. A debris flow sedimentation work according to any one of claims 1 to 4, wherein the bottom, peripheral wall, inlet wall and outlet wall are each made of concrete. The debris flow deposition work according to any one of claims 1 to 5, wherein the bottom slopes horizontally or downward from upstream to downstream.

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