JP7777003B2 - Method for constructing a dam and dam - Google Patents

Description

The present invention relates to a method for constructing a dam and to the dam itself.

A well-known example of a river debris flow countermeasure is a dam (sabo dam) equipped with a trapping body to capture rocks, driftwood, etc. that flow from upstream. The dam has a pair of non-overflow sections that protrude from both sides of the river, with an opening between the non-overflow sections to allow water to pass through.
The trap is installed in the opening and traps large-diameter rocks, driftwood, etc. while allowing small-diameter sediment and water to pass through. The trap has an upstream unit facing upstream in the river flow direction and a downstream unit facing downstream, with both units extending at an angle so that they approach each other as they extend upward and are connected to each other near their upper ends. The trap is installed across the width of the opening and its lower end is attached to a concrete foundation (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2017-101502

Meanwhile, in large rivers or rivers where large debris flows are predicted, dams called high dams, which are 15 meters or more in height from the bottom of the concrete foundation to the top, are often constructed. In the case of high dams, both the non-overflow section and the trapping body must be high, so construction can take a long time. In this case, if a debris flow occurs during construction, the trapping body will not function as a trapping body when it is not completed, and will therefore be unable to capture rocks, driftwood, etc.
Furthermore, if an existing dam becomes filled with sediment or if there are changes to the design standards for the dam, it will be necessary to build a new dam on top of the existing dam and raise the dam level.In this case, raising the dam level is difficult because the structure of the above-mentioned trapping body does not anticipate the addition of a new trapping body.

The present invention was developed in consideration of the above-mentioned problems, and aims to provide technology that allows trapping bodies to function even during construction, and that allows new trapping bodies to be connected to raise the height.

One aspect of the present invention is a method for constructing a new dam on an existing dam, comprising the steps of constructing a pair of non-overflow sections above the existing dam, and constructing a capture body in an opening formed between the pair of non-overflow sections that allows flowing water from upstream of the river to pass through and captures objects contained in the flowing water, wherein the capture body is attached to the non-overflow sections during the step of constructing the capture body.

The trapping body also includes an upstream unit located upstream of the river that traps the object, a downstream unit located downstream of the river that is curved so that its central portion protrudes toward the upstream unit, and a connecting portion that connects the upstream unit and the downstream unit. In the process of constructing the trapping body, it is preferable to attach at least each end of the downstream unit to the non-overflow portion.

Furthermore, it is preferable that the existing dam is a permeable dam equipped with a pair of non-overflow sections and a capture body, and that the construction method includes a first step of connecting the vertical and horizontal members that constitute the new capture body to the existing capture body, a second step of connecting a frame connected to the end of the horizontal member to the upper end of the existing non-overflow section, a third step of connecting the end of the horizontal member to the frame, and a fourth step of pouring concrete into the upper end of the non-overflow section to bury the frame.

It is also preferable that the second step be carried out immediately before the construction of the cross member in the first step is completed.

It is also preferable to repeat steps 1 through 3 multiple times before carrying out step 4.

Furthermore, it is preferable that the fourth step be performed with the connection portion between the end of the cross member and the frame connected in the third step exposed.

One aspect of the present invention is a dam comprising a pair of non-overflow sections and a capture body that is installed in an opening formed between the pair of non-overflow sections and that allows flowing water from upstream of the river to pass through and captures objects contained in the flowing water. The dam is characterized by also comprising a base installed in the non-overflow section and to which the capture body is connected, a first connecting part installed on the capture body that connects to a new capture body, and a second connecting part installed on the base that connects to the new base.

Furthermore, it is preferable that the capture body comprises a horizontal member connected to the mount and a vertical member intersecting the horizontal member, and that the first connecting portion be provided at the upper end of the vertical member.

Furthermore, it is preferable that the frame be buried in the non-overflow section with the second connecting portion exposed.

According to the present invention, the trap can function even during construction, and new traps can be connected to raise the height.

This is an oblique view of the dam before it is raised. This is an oblique view of a dam with the inside of the non-overflow section visible. FIG. 1 is a diagram illustrating a method for constructing a dam. FIG. 1 is a diagram illustrating a method for constructing a dam. FIG. 1 is a diagram illustrating a method for constructing a dam. FIG. 1 is a diagram illustrating a method for constructing a dam. FIG. 1 is a diagram illustrating a method for constructing a dam. This is an oblique view of the dam after it has been raised. FIG. 10 is a perspective view of a dam before being raised in a modified example. FIG. 10 is a perspective view of a dam in a modified example, showing the inside of a non-overflow section. FIG. 10 is a perspective view of a dam after being raised in a modified example.

A preferred embodiment of the present invention will be described with reference to the drawings.

<Dam structure>
1 and 2, the dam 100 is generally called a permeable dam, and comprises a pair of non-overflow sections 1, an opening 2, a capture body 3, and a mount 4. In the following, the vertical direction refers to the height direction of the dam 100 (depth direction of the river), and the horizontal direction refers to the width direction of the dam 100 (width direction of the river), which is perpendicular to the height direction of the dam 100.

The non-overflow sections 1 are walls made of concrete, and are also called sleeves. Each of the pair of non-overflow sections 1 extends from either bank of the river toward the center of the river, crossing the river. A predetermined distance is left between the pair of non-overflow sections 1, and an opening 2 is formed therein. The non-overflow sections 1 are constructed by pouring concrete upward onto a foundation 11 formed on the riverbed.

The opening 2 is a space formed between a pair of non-overflow sections 1, and a capture body 3 is installed therein. This allows the capture body 3 to capture large rocks and driftwood contained in the debris flow while allowing water, sand, small pebbles, etc. to pass through. A foundation 21 is formed at the bottom of the opening 2. The foundation 21 is formed in the riverbed and is made of, for example, concrete.

The capture body 3 allows water flowing from upstream in the river to pass through while capturing objects such as large rocks and driftwood. It is attached to the opening 2, at its base 21 and on the sides of the non-overflow sections 1 on both sides of the river in the direction of flow (on both sides across the river). The capture body 3 is used, for example, in high dams. Here, a "high dam" refers to a dam whose height (dam height) from the riverbed (bottom) on which the dam foundation is installed to the top of the capture body 3 is 15 m or more. High dams are primarily constructed on large rivers and rivers where large debris flows are predicted.

The capture body 3 includes an upstream unit 6 , a downstream unit 7 , and a connecting portion 8 .
The upstream unit 6 is provided on the upstream side of the river and is a functional component that captures objects such as rocks and driftwood contained in a debris flow that has flowed down from the upstream side of the dam 100. In other words, the upstream unit 6 is the unit that is directly subjected to the impact of the debris flow.

When the dam 100 is viewed in plan, the upstream unit 6 is provided linearly along the direction across the river (the width direction of the dam 100).
The upstream unit 6 includes a plurality of horizontal members 61 and a plurality of vertical members 62 .

The multiple horizontal members 61 are provided in a direction crossing the river and are arranged side by side along the height direction of the dam 100. The spacing between adjacent horizontal members 61 is preferably set smaller than the diameter of the rocks to be captured in the event of a debris flow. The spacing between adjacent horizontal members 61 may be the same from the top to the bottom of the capture body 3, or may be narrowed only above the capture body 3, and can be freely changed depending on the expected scale of the debris flow.
The cross member 61 is made up of, for example, a plurality of cylindrical steel pipes, each of which is connected to another via a flange provided at each end. Note that the steel pipes may be connected by welding their ends together without providing flanges, but considering the need for replacement after a debris flow collision, it is preferable to use flanges for connection.
Each horizontal member 61 is provided so as to penetrate the vertical members 62 and is joined to the vertical members 62 at their intersections. That is, of the multiple steel pipes constituting each horizontal member 61, the steel pipes that intersect with the vertical members 62 are joined to the steel pipes constituting the vertical members 62 and are configured as an integrated cross pipe 3a that is generally cross-shaped when viewed from the front.
Each cross member 61 has both longitudinal ends attached to the opposing side walls of the non-overflow section 1. Specifically, as shown in Figure 2, the ends of each cross member 61 are connected to the frame 4, and the frame 4 is embedded in the non-overflow section 1, thereby fixing each cross member 61 to the non-overflow section 1.

The multiple vertical members 62 are arranged along the height direction of the dam 100 and connect adjacent horizontal members 61 in the height direction. The multiple vertical members 62 are arranged side by side along the height direction of the dam 100. The spacing between adjacent vertical members 62 is preferably set smaller than the diameter of the rocks to be captured in the event of a debris flow. The spacing between adjacent vertical members 62 may be the same from one end to the other of the width direction of the capture body 3, or may be narrowed only near the center of the width direction of the capture body 3, and can be freely changed depending on the expected scale of the debris flow.
The vertical members 62 are made up of, for example, a plurality of cylindrical steel pipes, each end of which is connected to another via a flange. Note that the steel pipes may be connected by welding their ends together without providing flanges, but considering the need for replacement after a debris flow collision, it is preferable to use flanges for connection.
Each vertical member 62 is provided so as to penetrate the horizontal member 61 and is joined to the horizontal member 61 at the intersection. That is, of the multiple steel pipes constituting each vertical member 62, the steel pipes that intersect with the horizontal member 61 are joined to the steel pipes constituting the horizontal member 61 and are configured as an integrated cross pipe 3a that is generally cross-shaped when viewed from the front.
The lower end of the vertical member 62 is buried in the foundation 21 , so that the lower end of the vertical member 62 stands upright on the foundation 21 .
A flange portion 91 is provided at the upper end of the vertical member 62. This flange portion 91 functions as a first connecting portion that connects a new capture body above the existing capture body 3 when raising the height of the existing dam 100.

The downstream unit 7 is located downstream of the river from the upstream unit 6, and the impact load of the debris flow acting on the upstream unit 6 is transmitted via the connecting part 8, supporting the capture body 3.
When the dam 100 is viewed from above, the downstream unit 7 is provided in a direction that crosses the river, and is curved so that its central portion in the extension direction protrudes toward the upstream unit 6. In other words, the downstream unit 7 employs an arch structure, and is a structural member that uses compressive force to support the impact load of the debris flow transmitted from the upstream unit 6 via the connecting portion 8.
The downstream unit 7 includes a plurality of horizontal members 71 and a plurality of vertical members 72 .

The multiple cross members 71 are arranged in a direction crossing the river and are aligned along the height direction of the dam 100. The spacing between adjacent cross members 71 is preferably set smaller than the diameter of the rocks to be captured in the event of a debris flow. The spacing between adjacent cross members 71 may be the same from the top to the bottom of the capture body 3, or may be freely changed depending on the expected scale of the debris flow, such as by narrowing the spacing only above the capture body 3. The cross members 71 are arranged in a position facing the cross member 61 of the upstream unit 6 in the direction of the river flow.
The horizontal members 71 are made up of, for example, a plurality of cylindrical steel pipes, which are connected to each other via flanges provided at each end. Since each horizontal member 71 is required to be able to withstand the impact load of a debris flow, it is preferable to use a steel pipe with a larger diameter and higher strength than the steel pipes that make up the horizontal members 61 of the upstream unit 6. Note that the steel pipes may be connected by welding their ends together without providing flanges, but considering the need for replacement after a debris flow collision, connection using flanges is preferable.
Each horizontal member 71 is provided so as to penetrate the vertical members 72 and is joined to the vertical members 72 at their intersections. That is, of the multiple steel pipes constituting each horizontal member 71, the steel pipes that intersect with the vertical members 72 are joined to the steel pipes constituting the vertical members 72 to form an integrated crossing pipe 3c that is generally cross-shaped in front view. Furthermore, the steel pipes may be steel pipes that extend linearly along the axial direction or steel pipes that are curved along the axial direction, and an appropriate steel pipe may be selected depending on the curvature of the horizontal member 71.

Each cross member 71 is curved so that its central portion in the longitudinal direction (axial direction) protrudes toward the upstream unit 6. That is, the steel pipes located closer to the longitudinal center of the cross member 71 are closer to the cross member 61 of the upstream unit 6, and the steel pipes located closer to the end of the cross member 71 are farther from the cross member 61 of the upstream unit 6. By connecting the steel pipes together in this arrangement, the cross member 71 can be formed into an arch shape.
Each cross member 71 has both longitudinal ends attached to the opposing side walls of the non-overflow section 1. Specifically, as shown in Figure 2, the ends of each cross member 71 are connected to the frame 4, and the frame 4 is embedded in the non-overflow section 1, thereby fixing each cross member 71 to the non-overflow section 1.

The multiple vertical members 72 are arranged along the height direction of the dam 100 and connect adjacent horizontal members 71 in the height direction. The multiple vertical members 72 are arranged side by side along the height direction of the dam 100. The spacing between adjacent vertical members 72 is preferably set smaller than the diameter of the rocks to be captured in the event of a debris flow. The spacing between adjacent vertical members 72 may be the same from one end to the other of the width direction of the capture body 3, or may be narrowed only near the center of the width direction of the capture body 3, and can be freely changed depending on the expected scale of the debris flow.
The vertical members 72 are made up of, for example, a plurality of cylindrical steel pipes, each end of which is connected to another via a flange. Note that the steel pipes may be connected by welding their ends together without providing flanges, but considering the need for replacement after a debris flow collision, it is preferable to use flanges for connection.
Each vertical member 72 is provided so as to penetrate the horizontal member 71 and is joined to the horizontal member 71 at the intersection. That is, of the multiple steel pipes constituting each vertical member 72, the steel pipes that intersect with the horizontal member 71 are joined to the steel pipes constituting the horizontal member 71 to form an integrated cross pipe 3c that is generally cross-shaped when viewed from the front.
The lower end of the vertical member 72 is buried in the foundation 21 , so that the lower end of the vertical member 72 stands upright on the foundation 21 .
A flange portion 91 is provided at the upper end of the vertical member 72. This flange portion 91 functions as a first connecting portion that connects a new capture body above the existing capture body 3 when raising the height of the existing dam 100.

The connecting portion 8 connects the upstream unit 6 and the downstream unit 7 together.
The connecting portions 8 are arranged along the direction of river flow, connecting the opposing cross members 61 of the upstream unit 6 and the cross member 71 of the downstream unit 7. That is, like the cross members 61 and 71, the connecting portions 8 are arranged side by side along the height direction of the dam 100. Therefore, the spacing between adjacent connecting portions 8 is set to be smaller than the diameter of the rocks to be captured in the event of a debris flow. Furthermore, like the cross members 61 and 71, the spacing between adjacent connecting portions 8 may be the same from the top to the bottom of the capture body 3, or may be narrowed only above the capture body 3, and can be freely changed depending on the expected scale of the debris flow.
The connecting portion 8 is formed, for example, by a cylindrical steel pipe. One end of the steel pipe is connected to a cross member 61 (cross pipe 3a) of the upstream unit 6 via a flange, and the other end is connected to a cross member 71 (cross pipe 3c) of the downstream unit 7 via a flange. Therefore, the cross members 61, 71 to which the connecting portion 8 is connected must be provided with flanges in advance at positions opposite each end of the connecting portion 8. Note that the connecting portion 8 is not necessarily connected using flanges, and the connecting portion 8 may also be joined to the cross members 61, 71 by welding or the like.

The frame 4 is erected on the foundation 11 of the non-overflow section 1. The frame 4 is connected to the capture body 3, and when the dam 100 is completed, it will be buried in the non-overflow section 1 while still connected to the capture body 3.
The mount 4 is used to firmly fix the capture body 3 to the non-overflow section 1.
For each non-overflow section 1, the frame 4 is provided at a position facing the end of the cross member 61 of the upstream unit 6 and at a position facing the end of the cross member 71 of the downstream unit 7. A plurality of frames 4 are connected along the height direction of the non-overflow section 1, and are provided at positions where each cross member 61, 71 of the capture body 3 can be connected.
The mount 4 includes a plurality of vertical portions 41 and a plurality of horizontal portions 42 .

Multiple vertical sections 41 are provided along the height direction of the dam 100. The vertical sections 41 are, for example, composed of multiple cylindrical steel pipes. Flanges are provided at both ends of the vertical sections 41. The axial ends of each steel pipe are connected to each other via the flanges. The lower ends of the vertical sections 41, which are provided directly in the foundation 11 of the non-overflow section 1, are buried in the foundation 11, and as a result, the lower ends of the vertical sections 41 are erected on the foundation 11.

The horizontal portions 42 are provided midway along the axis of the vertical portions 41 so as to intersect with the vertical portions 41, and are arranged side by side along the height direction of the dam 100. The horizontal portions 42 are made up of, for example, a plurality of cylindrical steel pipes, and each steel pipe is connected to the horizontal members 61, 71 of the capture body 3 via a flange provided at one end in the axial direction of the steel pipe.
Each horizontal portion 42 is provided so as to penetrate the vertical portion 41 and is joined to the vertical portion 41 at the intersection thereof. In other words, the gantry 4 is configured as an integrated cross pipe having a generally cross shape when viewed from the front, in which the steel pipes constituting the vertical portions 41 and the steel pipes constituting the horizontal portions 42 are joined together.
Each horizontal portion 42 is provided so that one longitudinal end is exposed from the non-overflow portion 1 to the opening 2, and is positioned so that this one end can be connected to the horizontal members 61, 71.
The frame 4 is buried in the non-overflow section 1 except for the connection portions with the cross members 61, 71 of the capture body 3 in the horizontal portion 42. By burying the frame 4 in the non-overflow section 1, the cross members 61, 71 are fixed to the non-overflow section 1 via the frame 4, and the capture body 3 is fixed to the side wall of the non-overflow section 1.
The frame 4 extends in the height direction of the non-overflow section 1 by connecting the ends of multiple vertical sections 41 together.
In the dam 100, a flange portion 92 is provided at the upper end of the vertical portion 41 of the frame 4 located at the top. This flange portion 92 is exposed (protrudes) from the upper surface (top end surface) of the non-overflow portion 1. This exposed flange portion 92 functions as a second connecting portion that connects a new frame 4a above the existing frame 4 when the existing dam 100 is raised.

<How to build a dam>
Next, a method for constructing a new dam on the existing dam 100 (a method for raising the dam 100) will be described.
When raising the dam 100, as shown in Figure 3, a new capture body 3A is constructed at the upper end of the capture body 3 of the existing dam 100. When constructing the new capture body 3A, as shown in Figure 3, the vertical members 62a constituting the upstream unit 6a are connected to the flange portions 91 at the upper ends of the vertical members 62 from near the center of the width of the opening 2 toward the non-overflow portions 1 on both banks, while the horizontal members 61a are connected and assembled (first step).
Specifically, the vertical ends of the generally cross-shaped cross pipes 3a, each having a steel pipe constituting the vertical member 62a and a horizontal member 61a disposed midway between the steel pipes constituting the vertical member 62a so as to be perpendicular to the axial direction of the vertical member 62a, are connected to flanges 91 at the upper ends of the vertical members 62a, while the opposing horizontal ends of adjacent cross pipes 3a are connected to straight pipes (non-cross pipes) 3b extending in a straight line. As a result, the lower ends of the vertical members 62a constituting the upstream unit 6a are connected to the vertical members 62 of the existing capture body 3, and the lowest horizontal member 61a constituting the upstream unit 6a is connected.

Similarly to the upstream unit 6a, the downstream unit 7a is assembled by connecting the vertical members 72a constituting the downstream unit 7a to the flange portions 91 at the upper ends of the vertical members 72 from near the center of the width of the opening 2 toward the non-overflow portions 1 on both banks, while connecting the horizontal members 71a, as shown in Figure 3 (first step).
Specifically, the vertical ends of the generally cross-shaped crossing pipes 3c, each having a steel pipe constituting the vertical member 72a and a horizontal member 71a arranged perpendicular to the axial direction of the vertical member 72a, are connected to flanges 91 at the upper ends of the vertical members 72, while the opposing horizontal ends of adjacent crossing pipes 3c are connected to straight pipes (non-crossing pipes) 3d extending in a straight line. As a result, the lower ends of the vertical members 72a constituting the downstream unit 7a are connected to the vertical members 72 of the existing capture body 3, and the lowest horizontal member 71a constituting the downstream unit 7a is connected.
Furthermore, the cross pipe 3a and the cross pipe 3c are connected by a connecting portion 8a, thereby connecting the lowest stage of the upstream unit 6a and the lowest stage of the downstream unit 7a.

In the first step, the cross pipes 3a, 3c are connected to the vertical members 62, 72 of the existing capture body 3, while the cross pipes 3a, 3c are connected to the straight pipes 3b, 3d, and as shown in Figure 4, when the ends of the horizontal members 61a, 71a each come very close to the construction area of the non-overflow section 1a, the frame 4a is connected to the flange portion 92 at the upper end of the frame 4 exposed on the upper end surface of the existing non-overflow section 1 (second step). In other words, the second step is performed just before the construction of the horizontal members 61a, 71a in the first step is completed.
The base 4a is a substantially cross-shaped member having a vertical portion 41a and a horizontal portion 42a provided midway along the vertical portion 41a so as to be perpendicular to the axial direction of the vertical portion 41a.

In the second step, the pedestal 4a is connected to the flange 92 at the upper end of the pedestal 4 exposed at the upper end surface of the existing non-overflow section 1, and then the lateral ends of the cross pipes 3a, 3c, which are extended up to a position adjacent to the non-overflow section 1a, are connected to the end of the horizontal section 42a of the pedestal 4a by the straight pipes 3b, 3d (third step), as shown in Fig. 5. Here, one end of the straight pipes 3b, 3d is connected to the cross pipes 3a, 3c via the flange, and the other end of the straight pipes 3b, 3d is connected to the horizontal section 42a of the pedestal 4a via the flange.
This completes the bottommost part of the new trapping body 3A, and the cross member 61a at this bottommost part is connected to the base 4a.

Next, as shown in Figure 6, steps 1 to 3 are repeated to construct a new trapping body 3A in the second lowest tier. Specifically, the vertical members 62a and 72a of the new crossing tubes 3a and 3c are connected to the upper ends of the vertical members 62a and 72a of the lowermost crossing tubes 3a and 3c, while adjacent crossing tubes 3a and 3c are connected by straight tubes 3b and 3d. Furthermore, the crossing tubes 3a and 3c are connected by a connecting portion 8a. This connects the upstream unit 6a and the downstream unit 7a.
Then, when the ends of the cross members 61a and 71a have come very close to the construction area of the non-overflow section 1a, the new vertical member 41a of the pedestal 4a is connected to the upper end of the vertical section 41a of the pedestal 4a. After that, as shown in Figure 6, the horizontal ends of the cross pipes 3a and 3c, which have been extended to a position adjacent to the non-overflow section 1a, are connected to the horizontal section 42a of the pedestal 4a by the straight pipes 3b and 3d. One end of the straight pipes 3b and 3d is connected to the cross pipes 3a and 3c via flanges, and the other end of the straight pipes 3b and 3d is connected to the horizontal section 42a of the pedestal 4a via flanges.
This completes the second-lowest section of the new capture body 3A, and the horizontal member 61a in the second-lowest section of capture body 3A is connected to the second-lowest section frame 4a. In other words, by connecting the cross pipes 3a, 3c to each other, the vertical members 62a, 72a of the upper and lower sections are arranged coaxially along the height direction of the non-overflow section 1a, and the horizontal members 61a, 71a are arranged with a gap between them in the height direction of the non-overflow section 1a.
Furthermore, if the holes in the flanges of the vertical parts 41a of the mounts 4a are formed somewhat larger than the outer diameter of the bolts used for connection, the installation errors of the cross pipes 3a and 3c can be easily eliminated by adjusting the positions of the mounts 4a aligned vertically.

Next, as shown in FIG. 7, concrete is poured onto the upper end surface of the existing non-overflow section 1 to construct a non-overflow section 1a (fourth step).
In the fourth step, concrete is poured into the upper end surface of the existing non-overflow section 1 so as to bury the connecting portion between the existing base 4 aligned in the height direction of the new capture body 3A and the lowest base 4a of the capture body 3A, and the connecting portion between the lowest base 4a and the second base 4a. Furthermore, the connecting portion between the capture body 3A and the base 4a is not buried, in consideration of replacement during subsequent maintenance of the capture body 3A.
In addition, taking into consideration the connection of the third stage frame 4a, in the fourth step, concrete is poured so that the flange portion 92 at the upper end (upper end of the vertical portion 41a) of the second stage frame 4a is exposed.
The fourth step may be performed after the first to third steps have been repeated several times. That is, the cross pipes 3a, 3c, the straight pipes 3b, 3d, and the frame 4a may be connected in several stages, and then concrete may be poured onto the upper end surface of the existing non-overflow section 1 to construct the non-overflow section 1a.

Thereafter, the steps of connecting the cross members 61a, 71a and the vertical members 62a, 72a by connecting the cross pipes 3a, 3c and the straight pipes 3b, 3d, connecting the frames 4a, connecting the cross members 61a, 71a to the frames 4a, and pouring concrete into the non-overflow section 1a are repeated up to the required height to construct a new capture body 3A and non-overflow section 1a, completing the dam 100 as shown in Figure 8. Note that the cross pipe located at the top has a T-shape when viewed from the front, as there is no other cross pipe connected above it.
Through the above steps, a dam 100 as shown in FIG. 8 is constructed.

According to the above-described construction method for the dam 100 and dam 100A, the trapping bodies 3, 3A are connected to the frames 4, 4a embedded in the concrete that constitutes the non-overflow sections 1, 1a, so that the trapping bodies 3, 3A are firmly fixed to the non-overflow sections 1, 1a. This allows some of the debris flow load and impact load acting on the trapping bodies 3, 3A to be released to the non-overflow sections 1, 1a, improving the resistance of the trapping bodies 3, 3A to being pushed out or pulled out.
Furthermore, the trapping bodies 3, 3A are simply fixed to the non-overflow sections 1, 1a of the dam 100, 100A at intervals along its height, with the horizontal members 61, 71, 61a, 71a and the vertical members 62, 72, 62a, 72a having the same configuration. Therefore, even if the dam is not constructed to the originally planned height, the trapping bodies 3, 3A can function up to the completed height. In other words, conventional trapping bodies lack sufficient strength to function as a dam until completed, whereas the dam 100, 100A described above functions as a dam even if a debris flow occurs during construction because the trapping bodies 3, 3A are strong enough to capture rocks, driftwood, etc. Therefore, even in the construction of a dam, such as a high dam, which requires a long construction period, damage caused by a debris flow during construction can be reduced, and the construction period can be divided.

Furthermore, if the existing dam 100 becomes filled with sediment or if there are changes to the dam's design standards, it becomes necessary to construct a new dam on top of the existing dam 100 and raise the height of the dam 100. However, because the structure of conventional traps does not anticipate raising the height, it was not possible to construct a trap of the same structure above an existing trap. However, because the above-mentioned traps 3, 3A are fixed to the non-overflow sections 1, 1a, the trap 3A can be easily constructed above the trap 3 of the existing dam 100. Therefore, if the dam 100 having the above configuration is first constructed, a dam of the same structure can be constructed above it several years later to raise the height of the dam 100. This allows the dam 100 to be raised without creating any weak parts in the dam 100A as a whole.
In addition, the upper ends of the vertical members 62, 72 of the capture body 3 are provided with flange portions 91 that connect to the vertical members 62a, 72a of the capture body 3A to be newly constructed, and the upper end of the vertical portion 41 of the frame 4 is provided with a flange portion 92 that is exposed from the upper end surface of the non-overflow section 1 and connects to the frame 4a to be newly constructed.Therefore, when raising the existing dam 100 to construct the dam 100A, the new capture body 3A and frame 4a can be easily connected without making any changes to the existing dam 100.

Furthermore, since the cross members 61, 71, 61a, 71a that make up the capture bodies 3, 3A are attached at both ends to the non-overflow sections 1, 1a, even if rocks or driftwood contained in a debris flow climb over the upper ends of the upstream units 6, 6a and downstream units 7, 7a and fall below the capture bodies 3, 3A, the falling rocks and driftwood are less likely to collide with the capture bodies 3, 3A, and damage to the capture bodies 3, 3A can be suppressed.
Furthermore, since the stands 4, 4a have a simple structure consisting of vertical sections 41, 41a and horizontal sections 42, 42a both made from steel pipes, the same materials can be used as the horizontal members 61, 71, 61a, 71a and vertical members 62, 72, 62a, 72a of the capture bodies 3, 3A, making it easy to perform the connection work.

Furthermore, during construction of the capture body 3A, the second step of installing the platform 4a is carried out immediately before the construction of the cross members 61a, 71a is completed in the first step. This means that even if an error occurs in the construction position of the cross members 61a, 71a, the error can be eliminated by adjusting the installation position of the platform 4a, and the cross members 61a, 71a can be reliably and easily connected to the platform 4a.
In addition, the frame 4a to which the capture body 3A is connected is buried in the concrete poured to construct the non-overflow section 1a, so that the capture body 3A is firmly fixed to the non-overflow section 1a, thereby increasing the rigidity of the dam 100A.
Furthermore, after repeating the installation of the vertical members 62a, 72a, horizontal members 61a, 71a and frame 4a in steps 1 to 3 over multiple stages, concrete for multiple stages of the non-overflow sections 1a can be poured all at once in step 4, thereby increasing the flexibility of construction.

<Modification>
As shown in FIGS. 9 to 11, the above construction method can also be applied when constructing a dam 200A by raising the height of an existing dam 200.
Here, the dam 200, 200A differs from the above-mentioned dam 100, 100A in the configuration of the capture bodies 3B, 3C, and therefore the following will describe in detail the capture bodies 3B, 3C. The dam 200 comprises a pair of non-overflow sections 1, an opening 2, a capture body 3B, and a base 4.
The capture body 3B includes an upstream unit 6B, a downstream unit 7, and a connecting portion 8.
The upstream unit 6B is provided on the upstream side of the river and is a functional component that captures objects such as rocks and driftwood contained in the debris flow that has flowed down from the upstream side of the dam 200. In other words, the upstream unit 6B is the unit that is directly subjected to the impact of the debris flow.

The upstream unit 6B is bent so that its central portion in the extension direction protrudes toward the upstream side of the river when the dam 200 is viewed in plan view. In other words, the upstream unit 6B employs a curved arch structure, which reduces the composite stress level due to the temperature stress of the upstream unit 6B (internal stress that occurs in a structure due to temperature changes (for example, stress due to expansion and contraction of each component due to changes in outside temperature)).
The upstream unit 6B includes a plurality of horizontal members 61 and a plurality of vertical members 62 .

The multiple cross members 61 are arranged in a direction crossing the river and are aligned along the height direction of the dam 200. The spacing between adjacent cross members 61 is preferably set smaller than the diameter of the rocks to be captured in the event of a debris flow. The spacing between adjacent cross members 61 may be the same from the top to the bottom of the capture body 3, or may be narrowed only above the capture body 3, and can be freely changed depending on the expected scale of the debris flow. The cross members 61 are arranged in a position facing the cross member 71 of the downstream unit 7B in the direction of the river flow.
The cross member 61 is made up of, for example, a plurality of cylindrical steel pipes, each of which is connected to another via a flange provided at each end. Note that the steel pipes may be connected by welding their ends together without providing flanges, but considering the need for replacement after a debris flow collision, it is preferable to use flanges for connection.
Each horizontal member 61 is provided so as to penetrate the vertical members 62 and is joined to the vertical members 62 at their intersections. That is, of the multiple steel pipes constituting each horizontal member 61, the steel pipes that intersect with the vertical members 62 are joined to the steel pipes constituting the vertical members 62 to form an integrated crossing pipe 3a that is generally cross-shaped in front view. Furthermore, the steel pipes may be steel pipes that extend linearly along the axial direction or steel pipes that are curved along the axial direction, and an appropriate steel pipe may be selected depending on the curvature of the horizontal member 61.
Each horizontal member 61 is bent so that the center portion in the longitudinal direction (axial direction) protrudes toward the upstream side of the river. Each horizontal member 61 has a curved arch structure.
Each cross member 61 has both longitudinal ends attached to the opposing side walls of the non-overflow section 1. Specifically, as shown in Figure 10, the ends of each cross member 61 are connected to a frame 4, and the frame 4 is embedded in the non-overflow section 1, thereby fixing each cross member 61 to the non-overflow section 1.

The multiple vertical members 62 are arranged along the height direction of the dam 200 and connect adjacent horizontal members 61 in the height direction. The multiple vertical members 62 are arranged side by side along the height direction of the dam 200. The spacing between adjacent vertical members 62 is preferably set smaller than the diameter of the rocks to be captured in the event of a debris flow. The spacing between adjacent vertical members 62 may be the same from one end to the other of the width direction of the capture body 3B, or may be narrowed only near the center of the width direction of the capture body 3B, and can be freely changed depending on the expected scale of the debris flow.
The vertical members 62 are made up of, for example, a plurality of cylindrical steel pipes, each end of which is connected to another via a flange. Note that the steel pipes may be connected by welding their ends together without providing flanges, but considering the need for replacement after a debris flow collision, it is preferable to use flanges for connection.
Each vertical member 62 is provided so as to penetrate the horizontal member 61 and is joined to the horizontal member 61 at the intersection. That is, of the multiple steel pipes constituting each vertical member 62, the steel pipes that intersect with the horizontal member 61 are joined to the steel pipes constituting the horizontal member 61 and are configured as an integrated cross pipe 3a that is generally cross-shaped when viewed from the front.
The lower end of the vertical member 62 is buried in the foundation 21 , so that the lower end of the vertical member 62 stands upright on the foundation 21 .
A flange portion 91 is provided at the upper end of the vertical member 62. This flange portion 91 functions as a first connecting portion that connects a new capture body above the existing capture body 3 when raising the height of the existing dam 200.

The downstream unit 7 is located downstream of the river from the upstream unit 6B, and the impact load of the debris flow acting on the upstream unit 6B is transmitted via the connecting portion 8, supporting the capture body 3B.
The downstream unit 7 is disposed in a direction that crosses the river when the dam 200 is viewed from above, and is curved so that its central portion in the extension direction protrudes toward the upstream unit 6B. In other words, the downstream unit 7 employs an arch structure, and is a structural member that uses compressive force to support the impact load of the debris flow transmitted from the upstream unit 6B via the connecting portion 8.
The downstream unit 7 includes a plurality of horizontal members 71 and a plurality of vertical members 72 .
The downstream unit 7 has the same configuration as that of the above embodiment, and therefore the same reference numerals are used and the description thereof will be omitted.

The connecting portion 8 connects the upstream unit 6B and the downstream unit 7 together.
The connecting portion 8 is provided along the direction of the river flow, and connects the cross member 61 of the upstream unit 6B and the cross member 71 of the downstream unit 7, which face each other.
The configuration of the connecting portion 8 is the same as that of the above embodiment, and therefore the description thereof will be omitted.

The platform 4 is erected on the foundation 11 of the non-overflow section 1. The platform 4 is connected to the capture body 3B, and when the dam 200 is completed, the platform 4 will be buried in the non-overflow section 1 while still connected to the capture body 3B.
The stand 4 is used to firmly fix the capture body 3B to the non-overflow section 1.
For each non-overflow section 1, the frame 4 is provided at a position facing the end of the cross member 61 of the upstream unit 6B and at a position facing the end of the cross member 71 of the downstream unit 7. A plurality of frames 4 are connected along the height direction of the non-overflow section 1, and are provided at positions where each of the cross members 61, 71 of the capture body 3B can be connected.
The configuration of the gantry 4 is the same as that of the above embodiment, so the same reference numerals are used and the description thereof will be omitted.

The connected horizontal members 61, 71 are bent into an arch shape so that their central portions in their extension direction (axial direction of the horizontal members 61, 71) protrude most toward the upstream side of the river. When viewed in plan, the horizontal members 61, 71 are arranged so that the horizontal members 61 and 71 facing each other in the river flow direction are spaced approximately equally apart from one end to the other. In other words, the horizontal members 61 and 71 facing each other in the river flow direction are connected by multiple connecting portions 8 of the same length. Each vertical member 62 connects each horizontal member 61 to another, and each vertical member 72 connects each horizontal member 71 to another.

The method for constructing dam 200A by raising the height of dam 200 involves constructing a new capture body 3C at the upper end of capture body 3B of the existing dam 200, thereby constructing the non-overflow section 1. The specific procedure is the same as the method for constructing dam 100A by raising the height of dam 100 in the above embodiment.

As described above, the modified examples shown in Figures 9 to 11 achieve the same effects as the construction method for dam 100 and dam 100A in the above embodiment. In addition, because the upstream unit 6B is formed by bending it, the composite stress level due to temperature stress can be reduced even when both ends are fixed to the non-overflow section 1 via the frame 4. This increases the strength of the dams 200, 200A while reducing the composite stress level due to temperature stress, and also makes it possible to reduce the steel pipe diameter of the upstream unit 6B.

<Others>
Although the preferred embodiments of the present invention have been described, the present invention is not limited to the above embodiments and includes all aspects encompassed within the concept and scope of the claims. Furthermore, each configuration may be appropriately and selectively combined to achieve at least some of the above-described problems and effects. For example, the shape, material, arrangement, size, etc. of each component in the above embodiments may be appropriately modified depending on the specific usage of the present invention.

For example, the trapping body 3, 3A is not limited to the trapping body 3, 3A in which the upstream unit 6, 6a and the downstream unit 7, 7a are connected by the connecting portion 8, 8a, but may simply be a trapping body in which vertical members and horizontal members are assembled in a lattice pattern, and the above-mentioned dam construction method is also applicable to a dam equipped with a trapping body of such a simple structure. In other words, the above-mentioned dam construction method is applicable to any trapping body equipped with horizontal members extending in a direction intersecting the plane direction of the side surface (the surface facing the opening 2) of the non-overflow section 1, 1a.
Furthermore, it is not necessary to fix the lower ends of the vertical members 62, 72, 62a, 72a of the capture bodies 3, 3A to the foundation 21 of the opening 2, and it is important to arrange the horizontal members 61, 71, 61a, 71a in multiple vertical stages in the non-overflow section 1.
In addition, the capture body 3, 3A may have only the cross members 61, 71, 61a, 71a of the downstream unit 7, 7a attached to the non-overflow portion 1, 1a.
Furthermore, if the amount of elevation of the dam 100 is small, in the fourth step, concrete is poured up to a height that buries the upper end of the frame 4a, and the non-overflow section 1a is constructed up to a position higher than the upper end of the capture body 3A, thereby completing the dam 100A.
Furthermore, although the trapping bodies 3, 3A have been described as being provided on the dams 100, 100A called high dams, they may also be provided on dams that are not high dams.
Furthermore, the method of connecting each vertical member 62, 72, 62a, 72a and each horizontal member 61, 71, 61a, 71a is not limited to connection using bolts and nuts via the flange portions, but the steel pipes that make up each vertical member 62, 72, 62a, 72a and each horizontal member 61, 71, 61a, 71a may also be joined together by welding or the like.
Furthermore, the crossing tubes constituting the vertical members 62, 72, 62a, 72a and the horizontal members 61, 71, 61a, 71a are not limited to the crossing tubes 3a, 3c formed in a generally cross shape or a generally T shape in front view, but can be freely changed in shape depending on the configuration of the capture body 3, 3A. The non-crossing tubes are not limited to the straight tubes 3b, 3d, but can be freely changed in shape, such as by being curved, depending on the configuration of the capture body 3, 3A.

1, 1a Non-overflow section 11 Foundation 2 Opening 21 Foundation 3, 3A Capture body 4, 4a Frame 41, 41a Vertical section 42, 42a Horizontal section 6, 6a Upstream unit 61, 61a Horizontal member 62, 62a Vertical member 7, 7a Downstream unit 71, 71a Horizontal member 72, 72a Vertical member 8, 8a Connecting section 91 Flange section 92 Flange section 100, 100A Dam

Claims (8)

A method for constructing a new dam on an existing dam, comprising:
constructing a pair of non-overflow sections above the existing dam;
and constructing a capture body in an opening formed between the pair of non-overflow sections, which allows flowing water flowing from the upstream of the river to pass through and captures objects contained in the flowing water,
In the step of constructing the trap, the trap is attached to the non-overflow portion ,
The existing dam is a permeable dam equipped with a pair of non-overflow sections and a capture body,
A first step of connecting vertical members and horizontal members constituting a new capture body to an existing capture body;
a second step of connecting a frame connected to the end of the cross member to an upper end of the existing non-overflow section;
a third step of connecting the end of the cross member to the frame;
a fourth step of pouring concrete into the upper end of the non-overflow section to bury the frame;
A method for constructing a dam, comprising : The trapping body includes an upstream unit provided on the upstream side of the river for trapping the object, a downstream unit provided on the downstream side of the river and curved so that its central portion protrudes toward the upstream unit, and a connecting portion connecting the upstream unit and the downstream unit,
2. The method for constructing a dam according to claim 1, wherein in the step of constructing the capture body, at least each end of the downstream unit is attached to the non-overflow portion. 3. The method for constructing a dam according to claim 1 , wherein the second step is carried out immediately before the construction of the cross members in the first step is completed. 4. The method for constructing a dam according to claim 1, wherein the fourth step is carried out after the first to third steps are repeated a plurality of times. A method for constructing a dam described in any one of claims 1 to 4 , characterized in that the fourth step is carried out in a state where the connection portion between the end of the cross member and the frame connected in the third step is exposed. A dam comprising a pair of non-overflow sections and a capture body provided at an opening formed between the pair of non-overflow sections, which allows flowing water flowing from upstream of a river to pass through and captures objects contained in the flowing water,
a frame provided in the non-overflow section and to which the capture body is connected;
a first connecting portion provided on the capture body and configured to connect to a new capture body;
a second connecting portion provided on the cradle and configured to connect to a new cradle;
The capture body includes a vertical member provided along a height direction,
the first connecting portion is a flange portion provided at an upper end portion of the vertical member,
The stand includes a vertical portion provided along a height direction,
The second connecting portion is provided at the upper end of the vertical portion of the uppermost pedestal and is a flange portion exposed on the upper surface of the non-overflow portion.
A dam characterized by: The capture body includes a horizontal member that crosses the vertical member and is connected to the frame.
The dam according to claim 6 , characterized in that 8. The dam according to claim 6 or 7 , wherein the platform has a horizontal portion that intersects with the vertical portion, one end of which is exposed to the opening, and is connected to the capture body .