JP3992641B2 - Weir dam wear and scouring prevention method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a construction method for preventing wear and scouring of a flowing water falling portion caused by falling water or debris in a river dam.
[0002]
[Prior art]
Various dams installed in rivers are locally damaged by abrasion, scouring, etc. due to running water, debris flow and impact. Even dams made of high-strength concrete wear out in units of several centimeters in about one year, and usually the deepest part of scouring reaches several tens of centimeters in several years. When such scouring conditions become severe, inconveniences such as breakage of the dam due to turbulent flow and abnormal erosion occur.
[0003]
Various methods have been tried to prevent such dams from being worn and scoured. In other words, various materials have been attached to the surface of the flowing water falling portion where wear and scouring occur violently.
For example, there is a method of sticking steel plates, but the cost is high, it is difficult to sufficiently adhere to the dam concrete, the landscape is not preferable, the occurrence of a secondary disaster due to a large structure when it is lost There was a problem. The method of stretching natural stone has problems such as difficult construction for sufficient adhesion between dam concrete and natural stone, long construction period, and easy occurrence of wear and cracks in a short period of time. . In addition, there are methods such as stretching various rubber materials, coating resin mortar, and using both in combination, but rubber materials are difficult to secure adhesion to dam concrete, and cost is high, and resin mortar However, the coating was also expensive and required high construction techniques including water leakage treatment.
As described above, all the methods and methods of dam wear and scouring prevention that have been attempted so far have many problems, and no satisfactory results have been obtained.
[0004]
[Problems to be solved by the invention]
In view of such circumstances, the present invention provides a method for preventing dam wear and scouring, which has durable wear and scour prevention effects, is easy to construct, has a short construction period, and is easy to repair. With the goal.
[0005]
[Means for Solving the Problems]
As a result of various studies by the present inventors, it has been considered that impact energy of flowing water and sedimentary rocks, especially strong energy in the downward direction, should be received by a soft structure, and wear should be received by soils and rocks that can be easily procured on site.
That is, the present invention provides an excavation part in a portion corresponding to a flowing water falling part of a dam installed in a river, covers at least an inner wall of the excavation part with an impact buffer, and the inside of the excavation part includes a sand layer and A lower layer that is a gravel layer and an upper layer made of crushed rock and gravel are provided, and the layer made of crushed rock and gravel is covered and bound with a net-like or porous high-strength sheet, and then crushed as a surface layer. It provides a method for preventing dam scouring and scouring, characterized by laying a layer of rock and gravel.
The net-like or porous high-strength sheet is preferably a fiber material or a fiber-reinforced composite material having a specific strength of 200 × 10 ³ m or more and a specific modulus of 3 × 10 ⁶ m or more.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The dam wear / scour prevention method according to the present invention will be described in detail below with reference to FIGS.
[0007]
The weirs installed in the rivers are water discharge dams, hydroelectric dams, drinking / industrial water dams, etc., which cause wear and scouring in the lower part of the basin due to falling or falling water. Any dam that occurs can be the subject of the present construction method.
[0008]
In the present construction method, first, the excavation part 2 is provided in a portion corresponding to the flowing water falling part of the dam 1. It is preferable that the excavation part 2 is provided in the whole flowing water falling part, However, The excavation part 2 may be a partial thing centering on the part where a flowing water falling amount is especially large. Also, the form of excavation is not particularly limited, but it may be a form in which a part where impact energy such as flowing water is most likely to be applied when the amount of water is normal is deeply excavated. The depth of the excavation part 2 depends on the amount of water flowing in the river. For example, in the case of a water intake weir (maximum water flow amount of about 10 to 50 m ³ / sec) of a normal-scale hydroelectric power plant, the depth is 0.5 to 2.0 m. The degree is appropriate.
[0009]
At least the inner wall of the excavation part 2 in the method of the present invention is covered with an impact cushioning material 3 such as a rubber-based material in order to absorb lateral impact energy such as flowing water.
The impact buffering material 3 is not particularly limited as long as it has an impact buffering effect and is excellent in cut resistance and wear resistance, and examples thereof include natural rubber materials and urethane rubber materials.
The shock absorbing material 3 may be laid not only on the side wall of the excavation part 2 but also on the bottom surface.
[0010]
Next, the excavation part 2 to which the shock absorbing material 3 is fixed is provided with a sand layer and / or a gravel layer as a lower layer 4 therein. This layer acts as a buffer layer against downward impact energy such as flowing water.
The thickness of the lower layer 4 is not particularly limited, but is usually about 1/10 to 1/3 of the depth of the excavated part.
[0011]
In the excavation part, an upper layer 5 made of crushed rock and gravel is provided on the sand layer and / or gravel layer, which is the lower layer 4, and the layer made of crushed rock and gravel is a net-like or porous high-strength sheet. Cover and bind.
This layer is composed of a number of crushed rocks and gravel between them. The crushed rocks receive strong impact energy in the downward direction, such as flowing water, and receive soft impact energy in a soft structure. The gravel part that fills in the space works as a lubrication part when the crushed rock moves.
It is preferable from the point of unity that the crushed rocks used here are approximately 100 mm square to about 300 mm square in size, and if it can be obtained from the riverbank of the river where the method of the present invention is carried out, it can be transported, etc. It is advantageous in terms of cost.
The crushed rock and gravel of the upper layer 5 are covered and bound with a net-like or porous high-strength sheet. The covering and binding may be one for covering / binding the entire crushed rock and gravel of this layer, or may be a plurality of covering / binding.
Thus, by covering and binding with a net-like or porous high-strength sheet, even if it receives running water or the like, it will not flow downstream. And as mentioned above, crushed rocks can move a little by receiving impact energy such as flowing water, so this layer that covers / bonds crushed rock and gravel as a whole accepts impact energy such as flowing water in a flexible structure. It is.
[0012]
As a net-like or porous high-strength sheet for covering / binding crushed rock and gravel, a fiber material or a fiber-reinforced composite material having a specific strength of 200 × 10 ³ m or more and a specific modulus of 3 × 10 ⁶ m or more is used. preferable.
Examples of such materials include aramid fibers, high density polyethylene fibers, aromatic polyester fibers, and polybaraphenylenebenzoxazole fibers.
[0013]
The thickness of the upper layer 5 is not particularly limited, but is usually about 1/3 to 2/3 of the depth of the excavated part.
[0014]
On the upper layer 5 made of crushed rock and gravel covered and bound with a net-like or porous high-strength sheet, a surface layer 6 made of crushed rock and gravel similar to the upper layer is laid. However, the crushed rock and gravel of the surface layer 6 are not covered and bound with a high-strength sheet like the upper layer 5.
From the standpoint of preventing wear and scouring by receiving impact energy such as flowing water, the upper layer 5 made of crushed rock and gravel covered and bound with a high-strength sheet may be buried above the excavated part. . However, if the upper layer 5 covered and bound with a high-strength sheet is significantly deformed by the energy of running water, the river flow condition becomes irregular, and the dam is damaged or abnormal due to turbulence as in scouring. Inconvenience such as erosion occurs, and the aesthetics are also impaired.
Such inconveniences are eliminated by laying the surface layer 6 with crushed rock and gravel that are not covered and bound with a high-strength sheet. Moreover, since the crushed rock and gravel of the surface layer 6 will be washed away, it is necessary to repair them regularly, but the crushed rock and gravel will be easily available from the river basin near the construction section.
[0015]
The thickness of the surface layer 6 is not particularly limited, but is usually about 1/10 to 1/5 of the depth of the excavated part.
[0016]
【The invention's effect】
The present invention receives impact energy of flowing water and flowing debris, especially strong energy in the downward direction, with a soft structure using debris and rocks, so it can provide durable wear and scouring prevention effects and is easy to install. The construction period is short, and repairs are simple enough to replenish mainly crushed rocks and gravel. In this way, it is possible to provide a method for preventing dam scouring and scouring, which has an excellent effect of preventing scouring and scouring, and is easy to construct and repair.
[Brief description of the drawings]
FIG. 1 is a schematic view from above of an example of a result of a dam wear / scour prevention method according to the present invention.
FIG. 2 is a schematic view showing an example of a cross section of an excavation portion in the dam wear / scour prevention method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Dam 2 Excavation part 3 Shock absorbing material 4 (in excavation part) Lower layer 5 (in excavation part) Upper layer 6 (in excavation part) Surface layer

Claims (2)

An excavation part is provided in a portion corresponding to a flowing water falling part of a dam installed in a river, and at least an inner wall of the excavation part is covered with an impact buffer, and a sand layer and / or a gravel layer is formed inside the excavation part. A lower layer and an upper layer made of crushed rock and gravel are provided, and the layer made of crushed rock and gravel is covered and bound with a high-strength sheet or porous sheet, and a layer made of crushed rock and gravel as a surface layer thereon. A construction method for preventing weir scouring and scouring. 2. The intake weir according to claim 1, wherein the net-like or porous high-strength sheet is a fiber material or a fiber-reinforced composite material having a specific strength of 200 × 10 ³ m or more and a specific modulus of 3 × 10 ⁶ m or more. Abrasion / scouring prevention method.

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