JPH0464366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in an open dam structure for preventing damage caused by debris flows during floods.

(Prior art and its problems) Debris flow refers to a case where an abnormally large amount of sediment flows out compared to the amount normally transported by river flow, the flow distance is sufficiently longer than that of a collapse, the movement speed is faster than that of a landslide, A flow of sediment that is a combination of water and sediment, often containing boulders. Therefore,
The damage caused by debris flows during floods is enormous, and in order to prevent damage caused by debris flows, the downstream section of mountain streams where debris flows occur is equipped with a screen effect that captures boulders in the debris flow and transmits the debris, thereby reducing the destructive energy of debris flows. Various types of open dams, such as slit-shaped dams and lattice-frame dams, have been proposed with the aim of reducing the force of the dam and minimizing damage to downstream areas.

However, the conventional open dam structure
As shown in the figure, the main purpose is to prevent the boulders contained in the debris flow from flowing down, so the boulders are made to hit the pillars or boulders directly to stop their movement. Therefore, there is a problem in that the pillars or beams are seriously damaged, and in some cases, the dam may collapse.

Additionally, according to experiments and observations, the boulders contained in a debris flow are concentrated at the front part of the debris flow, as shown in Figure 5, and when such a debris flow reaches an open dam, the boulders in the front part collide first. However, as the movement of the boulders stops, most of the sediment is stored in the upstream of the open dam where the gaps are blocked by the boulders (see Figure 4), and the following flow is dammed up and becomes a vortex, which flows on both sides of the dam. There is also the problem that the intrusions become susceptible to damage due to scouring, and open dams no longer perform their original function.

(Problems to be Solved) An object of the present invention is to provide an open dam that can stop the movement of boulders, which is the original function of an open dam, but can allow small to medium-sized gravel and earth and sand to permeate downstream.

(Means for Solving the Problems) The present invention solves the problems of conventional slit dams and lattice frame dams by absorbing the kinetic energy of boulders that concentrate at the front part of a debris flow by colliding with the dam body and stopping the debris flow. This is due to the structure of the dam, so instead of directly stopping the movement of the boulders contained in the debris flow, if you change the direction of movement of the boulders and guide them to both banks downstream of the dam to capture them, the impact force that will be applied to the dam body will be reduced. In addition, it was completed with the focus on reducing kinetic energy, which not only reduces damage to the dam body, but also eliminates damage caused by scouring of debris flow vortices caused by sediment accumulation. The reason for this is that ``In open erosion control dams built as a measure against debris flows, when supporting columns are placed at regular intervals in the river width direction via beams, and in multiple rows in the flow direction, the central area in the river width direction is Debris flow boulder particle size D
Support column 1 with an effective spacing L1 of 1.5 to 2.0D.
Closely arranged part 1 formed by arranging 0 and/or beams 11
and a sparsely arranged part 2 or pillars 10 and 11 which are arranged on both sides of the densely arranged part 1 with an effective spacing L2 of 2.0D or more relative to the debris flow boulder particle diameter D. Boulder transmission zone 6 without beam 20
This is an open erosion control dam designed to guide boulders in a debris flow to both banks downstream of the dam.

The spacing between the pillars 10 in the river width direction and/or the beams 11 in the vertical direction is based on the assumed debris flow boulder grain size D.
When arranged at an effective interval L1 of 1.5 to 2.0D, a screen effect can be exerted that prevents the passage of large stones, but allows the passage of small and medium-sized stones. Therefore, in the present invention, as shown in Fig. 1, 1.5
The pillars 10 are densely arranged with an effective spacing L1 of ~2.0D, and on both sides of the densely arranged part 1, the pillars 10 are arranged sparsely with an effective spacing L2 of 2.0D or more relative to the particle size D of debris flow boulders. This will guide the boulders that collide with the densely arranged central area to both banks downstream of the dam according to the flow of the debris flow, thereby preventing the accumulation of sediment. Alternatively, as shown in FIG. 2, on both sides of the densely arranged part 1 of the pillars, etc., there is no coarsely arranged part with an effective spacing L2 of 2.0 or more relative to the debris flow boulder particle diameter D, and both sleeve parts 5 are The boulder transmission zone 6 may be formed on the inside.

However, as shown in FIG. 2, the densely arranged portion 1 is
Arranging the dam in an almost trapezoidal shape that widens from upstream to downstream is more effective in guiding boulders in a debris flow to both banks downstream of the dam.
It is desirable for the structural strength of the open dam to provide the coarsely installed portions 2 on both sides of the dam.

It is preferable to arrange pocket areas 3 on both banks downstream of the dam to store boulders.Furthermore, due to the nature of the rock on both banks downstream of the dam, boulders can be stored on both banks downstream of the dam where pocket areas 3 are provided. It is preferable to install a buffering zone 4 in the event of a collision to reduce the force of collision of the guided boulders with both banks and to trap them.

In addition, in the above embodiment, the spacing between the columns and beams was considered, but when the columns 10 are connected in a three-dimensional lattice shape by the beams 11, the vertical spacing of the beams 11 should be adjusted to the effective spacing of the columns 10. is preferable. Moreover, although the installation mode of the pillar 10 on the riverbed may be constructed by a conventional method, the construction method for the group pile type open dam submitted at the same time may be adopted. In other words, a plurality of steel pipe piles with sufficient penetration length into the river bed are used as supports, arranged at regular intervals in the river width direction, and arranged in multiple rows in the river flow direction so that the heads of the steel pipe piles are A simple structure may be adopted in which the riverbeds are connected to form a planar truss structure, while a concrete layer is laid on the riverbed to prevent scouring.

(Operations and Effects of the Invention) As is clear from the above explanation, according to the present invention, instead of directly stopping the movement of boulders contained in a debris flow, it is possible to change the direction of movement of the boulders and guide them to both banks downstream of the dam. As a result, the destructive energy of debris flows can be effectively reduced, which not only prevents damage caused by debris flows during floods but also reduces the impact force applied to the dam body without impeding river functions. Alternatively, the kinetic energy is reduced, causing less damage to the dam body. In addition, because the boulders at the front of the debris flow stop moving, most of the debris in the trailing flow is not stored, and can be transmitted downstream along with small and medium-sized debris, so the original function of the open dam is not hindered.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an outline of an open type sabo dam according to the present invention, Fig. 2 is a plan view showing a modified example of the sabo dam according to the present invention, and Fig. 3 is an overview of a conventional open dam type sabo dam. 4 is a cross-sectional side view thereof, and FIG. 5 is a cross-sectional side view showing the mode of debris flow. 1... Densely arranged part, 2... Roughly arranged part, 3... Pocket area, 4... Buffer zone, 6... Boulder transmission zone, 10... Support column, 11... Beam.

Claims (1)

[Claims] 1. In an open erosion control dam built as a debris flow countermeasure, when columns are arranged via beams at regular intervals in the river width direction and in multiple rows in the flow direction, Debris flow boulder particle size D in the central area
Support column 1 with an effective spacing L1 of 1.5 to 2.0D.
Closely arranged part 1 formed by arranging 0 and/or beams 11
and a sparsely arranged part 2 or pillars 10 and 11 which are arranged on both sides of the densely arranged part 1 with an effective spacing L2 of 2.0D or more relative to the debris flow boulder particle diameter D. Boulder transmission zone 6 without beam 20
This is an open type erosion control dam that is designed to guide boulders in a debris flow to both banks downstream of the dam. 2. The open erosion control dam according to item 1 above, wherein pocket areas 3 for storing boulders are provided on both banks downstream of the dam. 3. The open type erosion control dam according to the above items 1 and 2, wherein a buffering zone 4 in the event of a collision with boulders is installed on both banks downstream of the dam where the pocket area 3 is provided.