JPH08284138A - Construction method of checkdam and rolling block for erosion and sedimentation control - Google Patents

Abstract

PURPOSE: To construct a firm checkdam simply and quickly by few hands by utilizing natural force while effectively absorbing the fall energy of a debris' flow and a pyroclastic flow. CONSTITUTION: A large number of unit blocks 1 capable of being rolled discretely and having engaging projections 11 are scattered and arranged in a zone positioned on the upstream side of a place, where a dam in a zone, in which a debris' flow and a pyroclastic flow are generated or there is the possibility of the generation of these flows, is constructed. The scattered unit blocks 1 are carried away and collected by the fall energy of the debris' flow and the pyroclastic flow when both flows are generated in the zone, the engaging projections 11 of the adjacent unit blocks 1 are engaged mutually by collection, and the rolling of each unit block 1 is prevented by the engagement, thus manufacturing an unmovable checkdam 2. The unit block 1 has a large number of the projections 11, in which the envelopes of front ends are formed in a spherical surface, and has a core body having large weight and being made of concrete at a central section. The projections 11 are formed by rollable numbers under the state, in which the block is borne by the front end sections of the projections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sabo dam for blocking debris flow and pyroclastic flow, a method for constructing the same, and a concrete block used for the construction.

[0002]

2. Description of the Related Art The conventional wisdom about conventional sabo dams is that they must be strong structures that can withstand the enormous energy of debris flows and pyroclastic flows, and must be huge immovable structures installed on firm ground. It was that. Of course, in Japan where there is a land private ownership system and land is expensive, the concept that it must be an immovable structure in order to protect the land in a certain area is necessary. On the other hand, however, the falling energy of debris flow and pyroclastic flow moving down a steep slope is enormous, and enormous cost is required to construct an immovable sabo dam that can withstand this energy, which is extremely difficult to realize.

Therefore, in the conventional erosion control dam, as shown in FIG. 10, a small-scale dam 21 that withstands a small-scale debris flow or pyroclastic flow is provided on the slope 41, and the small-scale debris flow or pyroclastic flow is sloped 41. When it flows down, it receives the energy and stops it, deposits the falling debris on the upstream part of the dam, and as a result, changes the natural steep slope 41 into a relatively gentle slope 42 due to the deposited sand surface. Is the main. Then, the full-scale debris flow and pyroclastic flow thereafter do not cause fatal damage to the dam 21, which is the main body, and part of the falling energy is absorbed when passing through the gentle slope 42, resulting in the downstream. The effect of pyroclastic flow and debris flow on the river was reduced.

Such dams are usually installed in multiple stages at intervals along the flow path of debris flow and pyroclastic flow, and by gradually reducing the falling energy, the debris flow and pyroclastic flow are finally stopped to prevent disasters. Has achieved the purpose of.

In view of the fact that it is impossible to absorb all the energy of the debris flow and pyroclastic flow, the structure of FIG. 10 is designed to overcome the dam 21 so that a part of the energy is reduced. As another structure, the transmission type dam 22 shown in FIG. 11 is also frequently used. This dam 22 has a structure in which earth and sand or small-diameter stones pass through the dam, absorb the falling energy by frictional resistance when passing through the dam, and stop large-diameter stones that cannot pass through the dam.

On the other hand, although the field of use is different from that of the present invention,
As a dam for preventing sediment transport on the seabed, a dam constructed by stacking so-called Tetrapot (trademark) is well known.

[0007]

The erosion control dams 21 and 22 shown in FIGS. 10 and 11 are provided with a solid foundation so that the dams do not move or collapse due to debris flow or pyroclastic flow and are integrated on top of them. Must be built on. Also, it takes some time to solidify concrete,
It takes a considerable amount of time to build. Therefore, it is difficult to build it in the place where debris flow and pyroclastic flow occur frequently.
Further, when the dams 21 and 22 are filled with pyroclastic flow or debris flow, it is necessary to make a similar dam on the accumulated sediment, and, as mentioned above, since it is usually provided in multiple stages, the total cost is enormous. It will be

Further, when a debris flow or a pyroclastic flow occurs during the construction of the dam, there is a possibility that a serious accident related to the human life of the worker may occur even if the scale is small.

[0009] On the other hand, a dam with so-called tetrapots has the strength necessary to prevent sediment transport on the sea floor and to receive the static pressure of the accumulated sand, but it is not capable of inhibiting debris flow and pyroclastic flow. It is possible. That is, in a dam having such a structure, when a debris flow or a pyroclastic flow collides with the dam, the dam collapses due to the falling energy, and the blocks constituting the dam are scattered to the downstream side, so that they are not used as erosion control.

In view of the problems of the conventional sabo dam as described above, the present invention is capable of effectively absorbing the falling energy of debris flow and pyroclastic flow by a completely new idea and finally stopping it. It is an object of the present invention to obtain a method for constructing a sabo dam easily and quickly with a small amount of manpower, and safely in an area where frequent debris flow and pyroclastic flow occur, and to obtain a concrete block used for the method.

[0011]

The method of the present invention has an idea that is completely opposite to the conventional wisdom, that is, the conventional wisdom that an immovable structure is used so that the dam does not move or scatter. On the contrary, the scattered concrete blocks are aggregated by natural force, and the aggregated concrete blocks are integrated with each other so that a strong erosion control dam is constructed.

The method of the present invention can be individually rolled and entangled in an area where a debris flow or a pyroclastic flow is generated or is likely to be generated and which is located upstream of a site where a dam is to be constructed. A large number of unit blocks 1 provided with projections 11 are scattered and arranged. When the debris flow or pyroclastic flow occurs in the area, the unit blocks 1 arranged in a scattered manner are swept away by the falling energy and aggregate, and the entangled protrusions 11 of the adjacent unit blocks 1 are entangled with each other by the entanglement, and by this entanglement The unit block 1 is prevented from rolling and becomes a sabo dam 2.

The erosion control rolling block used in the method of the present invention comprises a large number of projections 11 having a spherical envelope surface at the tip, and a heavy core 18 made of concrete at the center thereof. And As a preferred form of block, a structure in which the basic shape of the core body 18 is a regular polyhedron and the protrusions 11 are formed by the corners 11a of the regular polyhedron and the cones 11b erected at the centers of the respective faces of the regular polyhedron are mentioned. You can In particular, the structure in which the regular polyhedron is a regular hexahedron is easy to manufacture, and the number of the protrusions 11 is an appropriate number.

Further, by varying the projection length depending on the direction of the projection 11, the center of gravity G of the block can be decentered from the center P of the spherical surface Q which is the envelope surface of the projection tip.

The number of projections 11 of each block is set to the number that allows the blocks to roll while being supported by the tip portions of the projections, and at least 8, preferably 14 or more are provided. Between the protrusions 11 provided on each block, there is a space in which the protrusions of adjacent blocks are inserted with a margin.

When the regular polyhedron of claim 4 is a regular tetrahedron, the number of protrusions is 8, and when it is a regular hexahedron, the number of protrusions is 14. The shape of the core body 18 at this time is appropriately a shape obtained by cutting out the central portion of each side of the regular regular polyhedron. If a regular polyhedron, which is the basic shape, is a regular hexahedron in this structure, the block can be easily manufactured.

The enveloping surface at the tip of the projection of the block does not necessarily have to be a perfect spherical surface, and may be a spherical surface such as an elliptic sphere or an oval shape. When a large number of protrusions 11 are provided,
It may include a low-height projection whose tip does not reach the spherical surface.

[0018]

The applicant of the present invention has proposed a rollable concrete block for constructing a sabo dam in Japanese Patent Application No. 6-55071. The present invention was made by testing the sabo dam proposed in the application and considering the behavior of the unit block.

The debris flow and pyroclastic flow passages are not of constant width and are twisted or bent, and the debris flow or pyroclastic flow slows down in some places and slows in other places along such terrain. Flowing.

The rollable blocks 1 scattered in the flow path of debris flow as described above, when debris flow or pyroclastic flow occurs,
The blocks themselves are gradually washed away, while each of them reduces its fall energy. The blocks 1 swept away in this manner are naturally gathered at a place where the flow velocity is slow or a place where the width of the flow is narrow. Since the unit block 1 used in the present invention is provided with the protrusions 11 that allow adjacent blocks to be entangled with each other when assembled, when they are gathered together, the protrusions interfere with each other to prevent the individual blocks 1 from rolling. To be done. Therefore, the blocks 1 stop at the gathering point, and the stopped blocks more firmly block the flow of debris flow and pyroclastic flow, so that the scattered blocks 1 gather at the place one after another, and the strong sabo dam is naturally formed. Built in.

The block 1 as a unit is a preformed product which is transported to the site and arranged. In areas where debris flows and pyroclastic flows are constantly occurring, unit blocks 1 are placed one by one using a helicopter. The location of block 1 is
It does not have to be very precise, but it should be placed in anticipation of flow-inducing or destructive effects and collective conditions.

It is preferable that the block 1 as a unit is as large and heavy as possible within a transportable range. Generally, it is considered appropriate to set it to about 10t. In this case, the diameter of the spherical surface Q which is the envelope surface of the tip of the protrusion is 2 to 3 m.
Therefore, the scattered individual blocks and the sabo dam constructed by arranging them in parallel form allow the large flow to be overcome and fine sediment to pass between the intertwined projections 11. It also has the function of the dam in FIG. Then, the blocks 1 can be piled up in multiple layers, and after the blocks placed earlier have been washed away, new blocks can be placed to make a multi-stage gathering, and finally a strong and large-scale Sabo dam can be constructed. .

The structure in which the center of gravity G of the block is deviated from the center P of the spherical surface Q serving as the envelope surface of the projection tip and the structure in which the spherical surface at the projection tip is an elliptical or oval spherical surface imparts rolling resistance to each unit block. It can also be used to give direction to the rolling of blocks.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of the method of the present invention, and FIGS. 2 and 3 are schematic views of a part of a sabo dam constructed by the method of the present invention. As shown in FIG. 1, a konpeito sugar-like block 1 having entangled protrusions 11 is arranged in an area where debris flow or pyroclastic flow is expected. The arrangement position is the upstream region of the point where the valley streak, which is the flow path for debris flow and pyroclastic flow, is bent, the slope is gentle, and the width is narrow.

The block 1 is arranged, for example, as shown in FIG. 1, so that the block 1 is arranged along the flow path so as to guide the side of the expected flow, or the flow is blocked to reduce the fall energy. Place B in the width direction of the flow. When a pyroclastic flow or a debris flow occurs, each block 1 reduces the energy of the flow due to the resistance to the rolling, and is pushed by the flow and rolls downstream. The balance between the flow resistance of the block 1 and the easiness of rolling is determined by the number of the projections 11, and the one having a small number of the projections 11 has a large force for blocking the flow. On the other hand, those with a large number of protrusions are prone to roll, and therefore gather more quickly.

The scattered blocks 1 gather at the points where the flow path is bent, the slope is gentle, or the width is narrow due to the debris flow and pyroclastic flow being received several times. Then, by collecting the blocks,
As shown in FIG. 3, the rolling of the individual blocks 1 is prevented in a state where the protrusions 11 of the adjacent blocks 1 are intertwined with each other. And a large number of blocks 1 assembled in this way
As a result, the dam 2 having a gap for passing fine earth and sand or water is formed between the tangled protrusions 11. Debris is accumulated on the upstream side of the dam, and a new block is further arranged on the accumulated debris, so that a large number of blocks 1 are intertwined with each other and are gathered in multiple stages, as shown in FIG. The dam 2 as shown in FIG.

FIGS. 4 and 5 show an example of a unit block having the most preferable structure for constructing a dam according to the present invention. In the unit block 1 of the first embodiment, the first projections 11a are formed at the corners of the regular hexahedron by cutting out the central portions of the sides of the regular hexahedron, and a square pyramid is formed in the center of each surface. The second protrusion 11b is provided. Second protrusion 1
1b is provided with the first projection 11a at a height such that their tip forms a spherical envelope surface.

As shown in FIG. 6, the block 1 having such a shape is provided with a projecting portion 32 for molding the upper and lower through holes 12 in the center of the block at the center of the bottom plate 31, and is translated in the front, rear, left and right directions in the figure. Using the mold 3 provided with the recess 34 for molding the second protrusion 11b in the center of the four side plates 33 opened by
A block main body 13 integrally provided with eight first projections 11a and four second projections 11b is molded, and a base portion 14 to be fitted into a through hole 12 (having a draft) of the block main body is formed. The two protrusion blocks 15 and 16 (the protrusion blocks 15 and 16 have the opposite taper direction of the base portion 14 to the protrusion 11b) are separately molded, and can be fitted and fixed.

A block having a larger number of protrusions 11 is formed by using a mold having a complicated split structure or a mold having side plates that open in 6 directions, 8 directions or more directions. You can also Further, as shown in FIG. 8, a core unit 18 having a fitting hole 17 is molded, and a projection unit 19 in which a projection 11 made of H-shaped steel or the like is embedded in a base portion 14 fitted and fixed in the fitting hole. It is also possible to manufacture a block having a projection made of shaped steel by fitting and fixing.

Further, as shown in FIG. 9, the center of gravity G of the core 18 is
Can be decentered from the center P of the spherical surface Q which is the envelope surface of the tip of the protrusion. In this case, due to the eccentricity of the center of gravity, each block takes a stable position in a specific direction, and resists the force of rolling. Therefore, the block having such a structure can increase the resistance of each block against debris flow and pyroclastic flow without impairing the easiness of rolling, that is, the ease of assembly.

[0031]

As described above, according to the method of the present invention, the falling energy of the debris flow or pyroclastic flow to be blocked is used to construct a strong erosion control dam by natural force. Can be quickly and safely performed using a helicopter, crane, etc., especially in areas where debris flow and pyroclastic flow frequently occur, by repeatedly using that power, ultimately it can not be constructed by human power at all. This has the effect of making it possible to build a strong sabo dam.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of the method of the present invention.

FIG. 2 is a perspective view schematically showing an assembled state of blocks.

FIG. 3 is a perspective view schematically showing a state where blocks are assembled in multiple stages.

FIG. 4 is a perspective view showing a block of the first embodiment.

5 is a cross-sectional view of the block of FIG.

FIG. 6 is a schematic cross-sectional view showing a mold for the block of FIG.

FIG. 7 is a perspective view showing a protrusion block.

FIG. 8 is a schematic perspective view showing another structure of the protrusion.

FIG. 9 is a cross-sectional view showing a block in which a core body is eccentric.

FIG. 10 is a schematic side view of a first conventional example of a sabo dam.

FIG. 11 is a schematic perspective view of a second conventional example of a sabo dam.

[Explanation of symbols]

 1 unit block 11 projection 11a first projection 11b second projection 18 core G center of gravity P center Q spherical surface

Claims (7)

[Claims] 1. An upstream side of a site where a dam is to be constructed in an area where a debris flow or a pyroclastic flow may occur or may occur,
Characterized by arranging a number of unit blocks (1) that are individually rollable and have entangled protrusions (11) in a scattered manner,
How to construct a sabo dam. 2. The unit blocks (1) dispersedly arranged by the method of claim 1 are aggregated by the falling energy of debris flow or pyroclastic flow, and the unit blocks are adjacent to each other by the aggregate.
A sabo dam, in which the unit blocks (1) are prevented from rolling due to the entanglement of the entangled protrusions (11) with each other. 3. A large number of protrusions (1
A rolling block for erosion control which comprises 1) and a heavy core (18) made of concrete in the center thereof. 4. The protrusion (11) is composed of a corner (11a) of a core (18) whose basic shape is a regular polyhedron and a cone (11b) erected at the center of each face of the regular polyhedron. The rolling block according to claim 3, wherein 5. The center of gravity (G) of the core body (18) is eccentric from the center (P) of the spherical surface (Q) which is the envelope surface of the projection tip.
The rolling block described. 6. The method for constructing a sabo dam according to claim 1, wherein the rolling block for erosion control according to any one of claims 3 to 5 is used. 7. The erosion control dam according to claim 2, wherein the erosion control rolling block according to any one of claims 3 to 5 is used as a unit block.