JP7282949B1 - Scouring prevention method using natural sedimentation of stones and rocks - Google Patents

Abstract

A scouring prevention construction method utilizing natural sedimentation of stones and rocks. [Solution] In front of the building where the scouring condition is occurring, large stones and rocks in the surroundings are arranged vertically in the direction of the flow, and they are arranged in multiple rows. They are spaced apart and fixed directly to the bottom with individual fasteners. At the same time, between and on the sides of these rows and adjacent to the building, rows of larger stones and rocks, also in the surroundings, were placed transversely to the direction of the water flow, each with individual fastenings. It is fixed directly to the bottom of the water by a tool. This provides a natural sediment deposit on the front of the building to prevent scouring of the building. [Selection drawing] Fig. 1

Description

The present invention relates to a method for preventing scouring occurring in front of bridge piers, embankments, revetments and other structures in stony or rocky basins and bodies of water.

In rivers, structures such as bridge piers and revetments may be deeply eroded where water flows directly, which is called scouring. Scouring sometimes destroys bridge piers and causes bridges to be washed away, and it also destroys embankments that are protected by banks. However, scouring itself is a completely natural phenomenon, and it is a phenomenon that always occurs when water currents collide directly with quay walls on the bank of a river. is occurring.

There are many stones and rocks of various sizes in the upper and middle reaches of the river, and there are also many smaller gravel, sand and soil. In the upper and middle streams, it is normal for the river to flow deep where there are large stones and rocks, and to flow shallow where there are many pebbles and sand. The scouring phenomenon occurs in a place where there are large stones, rocks, small stones, sand, soil, and so on, and where there is a strong water current.
The scouring phenomenon can often be seen in the bends in the upper and middle reaches of rivers, and these places often form deep pools, and it can be said that this is because the rocks in the bends are huge. Even if it is not a curved part, even if a huge rock is in contact with the water flow, there may be a deep abyss in front of it.
In addition, there are places in the upstream and midstream where natural quays continue along the banks of the river, but even in those places the river flows deep in front of the quays, and there is a lot of small sediment such as gravel and sand on the bottom of the river. At these places, water flows parallel to the quay walls, so it can be said that scouring occurs in the same way as in the bend, although it is not as deep as the edge of the bend.

In Japan, it is normal for the normal flow of the upper and middle streams to be transparent, and at that time there is almost no sediment flowing down. The scouring phenomenon is caused by excessively flowing stones, rocks, and other sediments, so it is more likely to occur when the water level is high and the amount of water is large.
When the water volume is normal, the water current meanders around the center of the riverbed, but when the water volume increases, the flow rate increases and changes the position of the flow, sometimes scouring the protected bank. Since the water current has a strong tendency to try to flow deep in the place where the water flowed when the water level is high, the bank continues to flow deeply even when the water level returns to normal, and the scouring condition continues before the concrete revetment. In this case, even if it is a wide riverbed, it often becomes a scene where the position of the water flow is limited to both banks.

At first glance, the sediment of various sizes in the upper and middle reaches appears to be flowing down and accumulating in a completely irregular manner, but there is a clear regularity. In the upper-middle stream, the size of stones and rocks increases as it reaches the upper stream. This is well known to many people in Japan, and some say they learned it in elementary school. For example, no one would be surprised if a river with a handful of stones and rocks upstream cannot see stones larger than a fist in its middle reaches.
To be precise, this phenomenon means that the size of large stones and rocks in the earth and sand at each location in the upper and middle reaches becomes larger as it reaches the upper stream and becomes smaller as it approaches the lower stream. Not all stones and rocks in each place are getting bigger, and in each place there are more small stones and rocks than big stones and rocks, and they are upstream and downstream of each place. It is no different from the size of the small stones and rocks on the side.

In rivers, the larger the stones and rocks, the more difficult it is to flow, and the smaller the sand and sand, the easier it is to flow. Therefore, it is normal for large stones and rocks in each location to stay in place for a long time, and smaller sand and sand tend to flow down more frequently. It often comes and flows downstream. The phenomenon that the size of stones and rocks increases as it goes upstream is related to the fact that the frequency of occurrence of flooding in rivers differs according to the scale.
A particularly large flood occurs only once every few decades or decades. Large-scale flooding occurs about once every few years, and large-scale flooding occurs about once a year. Normal flooding occurs several times a year, and smaller flooding occurs many times a year.

Most of the stones and rocks in the river flow down only when the water rises on a particularly large scale. Even stones and rocks don't flow forever.
When the water rises on a large scale, stones and rocks that are smaller than the largest stones and rocks in the surrounding area flow down, but they do not continue to flow down forever. Stones, rocks, and small earth and sand smaller than them are flowing down whenever there is the above-mentioned rise in water or large and small rises. However, even those small stones and rocks, most of them do not continue to flow anywhere. At any of those occasions when the water rises, the larger stones, rocks, and sediments that are flowing down will stop and start accumulating sooner.

All stones and rocks in a river do not flow more than they deserve for their size and weight. Therefore, the large stones and rocks in each place will not easily move downstream even if there are many opportunities for the water to rise. It can be said that this trend is more pronounced in the upper reaches, where the stones and rocks are larger in size. In other words, the larger the stones and rocks in the upstream, the longer it takes for them to descend little by little.
In the middle stream, where stones and rocks are generally smaller, the size of large stones and rocks changes from place to place over a long distance, but large stones and rocks do not flow down as easily. These phenomena have continued in many rivers around the world without change over the years. Therefore, anyone can confirm that the stones and rocks are larger in the upstream. However, since the water volume and slope of the river flow do not change uniformly due to topography and tributaries, the phenomenon that the size of stones and rocks increases as it goes upstream does not change uniformly. .

In the upstream and midstream, there are also situations where it is easier to check those things. When the water level rises and the river bed becomes a stream, a large amount of sediment flows over the width of the river, and the river bank where the water flow is weak. There are many deposits of large stones and boulders. On the other hand, in large and small floods that occur frequently, the water level does not rise so much, so the water flow does not reach the high river bed, and the stones, rocks, and small sediments that flow down and accumulate are deposited in the center of the river. It deposits only on or near the bottom of a U-shaped dug.
Due to these circumstances, the large stones and rocks in each place have few chances to flow down, and often stay on the riverbed or bank and continue to accumulate, so they are conspicuously visible in those places. These stones and rocks are characterized by their similar sizes, even though their shapes are different.

The description here simplifies some phenomena that occur in reality, but the situation that occurs in actual rivers is a little more complicated. Also, in recent years, many construction works have been carried out in the upstream and midstream, so it cannot be said that the above phenomenon is occurring as it is. However, many people are aware that there is a phenomenon in which the size of stones and rocks increases as they go upstream. It is also a clear fact that large stones and rocks in each place do not flow down easily, and such phenomena occur universally in rivers everywhere.

In the upper and middle reaches of the river, there is a quay made of huge rocks at the bend where the water flow directly hits, and the place is often deep. , Even if a strong water current hits it, it is not a huge rock, but a lot of large and small stones, rocks, and small earth and sand accumulate, and you can see the situation where the water current bends and flows down without scouring.

In the various scouring prevention methods that have been considered in the past, it is common to install a structure that directly controls the strong water flow that is the cause of scouring at that location to prevent the scouring phenomenon. (See Patent Documents 1 to 3, for example).
In most conventional scouring prevention works, it was not always sufficient to consider the regularity of sediment flow and sedimentation in rivers with a lot of sediment such as stones and rocks. The present invention considers the regularity of sediment flow and sedimentation in the upstream and midstream, and the importance of large stones and rocks at each location. This invention is based on observations of places where there is no soil, and is intended to create a sedimentation situation in front of a building that does not cause scouring by utilizing natural sediment flow and sedimentation.

Patent 6986119 Patent 5022500 Patent 5936356

In rivers, scouring occurs not only in bridge piers but also in concrete embankments. However, since the various conventional techniques do not truly prevent scouring and only add to the expense of repeated construction work, a permanent solution to these problems has been desired.

In natural rivers, large stones and rocks in each place do not easily move and flow down even if the water rises many times. It continues to exist in a natural sedimentary state with other stones and rocks without causing excavation phenomena.
Scouring occurs because the stones and rocks in contact with the flow are too large compared to the surrounding earth and sand. Therefore, if it is possible to create a natural sedimentation centered on large stones and rocks in front of structures such as bridge piers, revetments, and embankments where scouring occurs, it will be possible to prevent strong scouring during high water levels. Water currents will no longer reach buildings or shores directly, and scouring will no longer occur.

In front of the building where scouring is occurring, arrange some of the larger stones and rocks in the surroundings vertically in the direction of the water flow, and arrange them in one or more rows. Install with a gap. Each of these stones, rocks, and rows of rocks is held directly to the bottom using fasteners so that they do not move even when the bottom itself is fluidized by rising water. In addition, between the rows of stones and rocks installed vertically and in contact with the structures on the side of them, rows of stones and rocks are also installed in the transverse direction of the water flow. These stones and rocks and their rows are also fixed directly to the bottom of the water using fasteners.
At this time, the fasteners that hold the stones, rocks, or rows of them to the bottom of the water must be individually buried directly in the bottom of the water. If a base block made of concrete or the like is provided under a row of stones or rocks, or if fasteners are embedded in them, the base block will act as a huge stone or rock, causing new scouring. end up
If the number of large stones and rocks in the surrounding area is small, it is possible to use artificial stones and rocks that resemble them, but artificial ones are extremely poor in durability, so they should be natural as much as possible. You should use stone.

If the stones or rocks to be held in place are too large to be held directly in place by fasteners, etc., a number of such stones or rocks are placed in a bag or gabion using wire mesh or metal fittings. After arranging them in a shape or the like, they are placed in rows, spaced apart in the direction of the water flow, while still allowing the water flow to pass freely through the stones and rocks, and are secured in the same manner as above. stay on the bottom for a long time. In addition, in contact with the structures between and on the sides of the vertically installed sack-shaped or gabion-shaped rows of stones and rocks, similarly sac-shaped or gabion-shaped rows of stones and rocks are installed in the transverse direction of the water flow. Stay on the bottom in the same way. Even in these cases, each anchor holding the stone or rock and row to the bottom must be directly buried separately and separately from the other anchors.

An important aspect of the new construction method is the size of stones and rocks to be held in place vertically and horizontally. The large stones and rocks in the surrounding area do not easily flow down even when there is a large-scale rise in water. But it will not be destroyed.
If those stones or rocks are too large, they create a new scouring condition around them and prevent other stones, rocks, or sediment from accumulating. less, and more likely to flow down. For the same reason, even if concrete is set in place of a row structure of natural stone or rock, or concrete blocks are held in rows, the new structure will not produce results.

The length of the rows of stones and rocks to be installed by the new construction method will be changed according to the conditions of each place. Even if the number of stones and rocks in the row is small, it may be effective in some cases. In a natural river, the slope of the bank is steep where there are large stones and rocks on the bank, and the slope is gentle where there are many pebbles and sand on the bank.
Spacing between rows of stones or rocks should also be considered. If the gap is too narrow, there is less chance of large stones and rocks flowing in, and if it is too wide, a new strong water current will be generated in the place and the stones and rocks that flow down will be easily discharged. . The spacing between rows depends on the strength of the water flow and the amount of sediment that flows down, but it should be about 3 to 5 times the width of the rows of stones and rocks that are installed. This also depends on the situation on the spot.

In the claims and part of the specification, the size of the large stone or rock is described as the larger stone or rock in the surroundings. This is because, when carrying out construction work, it is not required to strictly judge whether the stones or rocks are large or not based on numerical values.
The size of large stones and boulders in each location is different for each location. In addition, stones and rocks in rivers usually have various shapes, and it is impossible to strictly define and judge the size of each in this situation. Furthermore, even in the case of large stones and rocks at different locations in an actual river, their sizes are not exactly the same.
Therefore, in order to make it possible to judge large stones and rocks realistically, they are taken as large stones and rocks in the surroundings. In fact, it is a matter within the discretion of the builder doing the work on site.

The row of stones or rocks installed and fixed according to the invention is in front of the building and is formed by larger stones or rocks in the surroundings. Therefore, the building is not directly hit by the strong water flow of the increased water level, and scour conditions do not occur around the building. And the various large and small stones, rocks, and earth and sand that flowed down piled up and piled up between rows of stones and rocks, along the sides, and on top of them, just like on a normal bank.
When a large-scale flood or a large-scale flood occurs, in the structure of the present invention, large stones, rocks, and stones of similar sizes in the large amount of earth and sand that flowed down when the water volume was the largest Yaiwa enters between the rows of stones and rocks, but due to its size and weight, it cannot climb over the rows of stones and rocks that have been placed, and often remains between the rows of stones and rocks. . Most of the other sediments flowed over the rows of stones and rocks and flowed down, even if they flowed in large amounts. It flows down again. As the amount of rising water decreases, stones and rocks that are smaller than larger stones and rocks are deposited on the spot, and then as the amount of water decreases, the sediment deposited on the spot becomes even smaller.

When the water rises, the sediments of various sizes deposited on the banks of the river flow down in order from small sands and gravel to small stones and rocks, and not all the sediment flows down at once. Even in the new structure according to the present invention, even if there are many floods such as large-scale floods and large-scale floods, the sediment deposited on the spot will not flow down immediately, and the installed large stones will not flow down. Since rocks and larger stones and rocks deposited later do not flow down, the possibility of a strong water current hitting the structure directly is extremely low.
In the structure according to the present invention, among stones, rocks, and earth and sand of various sizes that flow down every time water rises, further flow down of earth and sand that is smaller than larger stones and rocks in place is prevented. There is no The new structure keeps the stones and rocks that should flow down whenever the water rises to various scales, and keeps the stones and rocks that cannot flow down in place. It deposits stones, rocks, and earth and sand of various sizes sequentially.

The structure according to the method of the present invention is a method that utilizes the phenomena of sediment flow and sedimentation that are naturally observed in rivers. It is easy to install because it uses rocks. In addition, this construction method can be applied to a shore without structures such as a bank protection.
The newly formed scene becomes a natural landscape in harmony with nature, a natural environment itself. Naturally accumulated stones and rocks are much more durable than artificial stones, rocks, or concrete, and are maintained in that state for a long time. It is extremely easy to maintain a new structure because it is naturally replaced by many floods.

The stones and rocks of the present invention are placed in a vertical row and fixed using fasteners on both sides and the center of the pier, and the rows of stones and rocks are similarly fastened along the pier in the transverse direction of the flow. It is a top view of the example which used and installed and fixed. A plan view of the present invention implemented in a bank protection, in which the stones and rocks of the present invention are put together in a bag-like or basket-like shape, arranged in rows, spaced apart, and fixed using fasteners in the transverse direction of the flow. It is a plan view of an example of installation and fixing using fasteners in the same way along the seawall. Fig. 10 is a plan view of the present invention, in which when stones and rocks are put together in a bag-like or basket-like shape and arranged in a row, fasteners for fixing them are connected to the left and right to use a U-shaped structure. 4 is a cross-sectional view of FIG. 3. FIG.

The plan view of FIG. 1 will be described as an example in which a structure according to the method of the present invention is installed on a bridge pier in the upper and middle reaches of a river. Larger stones and rocks 2 in the surrounding area are vertically arranged in rows on both sides of the pier 6 facing the direction 1 of the flow and on the central part of the pier. The fastener 4 is directly buried in the bottom of the water and fixed at that place. In this figure, the fasteners are assumed to be piles or columns.
In addition, between the vertical rows of the stones and rocks, similarly large stones and rocks 2 in the surroundings are arranged in a row in the transverse direction of the flow and installed just before the pier, and the fasteners 4 are placed on the bottom of the water. They are directly buried and fixed in place.
Due to these structures, among the large amount of sediment that flows when the water level rises, the larger stones and rocks first stay between the rows of stones and rocks, and the smaller stones and rocks and small sediment gradually fall into place as the water level decreases. Stay in place. Therefore, strong water currents do not directly reach the piers and scouring is eliminated. In the case of piers, there is no need to build a long pier with a wide width against the flow, so you do not need many rows of stones and rocks to be installed facing the flow, but you can install them on both sides of the pier. is required.

FIG. 2 is a plan view when the present invention is applied to a bank protection 7 in an upper-middle stream area, and a structure in which a large number of large stones and rocks 2 in the surrounding area are put together in a bag-like or basket-like 3 row-like structure. Then, a plurality of them are installed at intervals in the direction 1 from which the water flow comes, and fasteners 4 are directly buried in the bottom of the water and fixed at each place. In addition, between and beside these rows, bag-shaped or basket-shaped rows of stones and rocks 3 are similarly installed and fixed just before them along the bank protection in the transverse direction of the flow.
Since scouring conditions do not occur on all banks even in the upstream and midstream of rivers, it is not necessary to perform scouring prevention work on all banks. Scouring prevention works need to be carried out only on banks that are hit by strong currents when the water level rises. If scouring prevention works can be carried out at these places and sedimentation that does not flow down even when the water rises can be produced, natural sedimentation will also occur around and downstream.

In FIG. 3, when a large number of large stones and rocks 2 in the surrounding area are collected in a bag-like or basket-like shape 3, U-shaped fasteners 5 connected to the left and right are used to fix them. 1 is a plan view of an example; FIG.

FIG. 4 is a cross-sectional view of FIG. 3 above.

1 Direction of water flow.
2 A large stone or rock in the surroundings.
3 Bag-shaped or cage-shaped structure containing large stones or rocks 4 Fasteners for holding large stones or rocks, or bag-shaped or cage-shaped structures containing them, in place.
5 U-shaped fasteners connected to the left and right to hold large stones and rocks, or bag-like or basket-like structures containing them, in place.
6 piers.
7 Revetment.
8 bottom.

Claims (3)

In front of bridge piers, revetments, embankments, and other structures where scouring is occurring or is likely to occur underwater, large stones or rocks in the surrounding river, or man-made structures that resemble them Stones and rocks are arranged vertically in the direction of the water flow, and are placed individually or in multiple rows at intervals. Scouring prevention construction method characterized by firmly holding down and fixing in place . If the above-mentioned large stones and rocks in the surrounding river or artificial stones and rocks resembling them are of a size that cannot be directly fixed individually by fasteners, In order for the water flow to pass freely, the wire mesh is placed in an elongated basket-like or bag-like shape, and the rows are arranged vertically in the direction of the water flow, either singly or at intervals . 2. The anti-scouring method according to claim 1, wherein each of the fasteners is directly buried in the bottom of the water so that the stones and rocks and their rows are securely held in place and fixed. Between the rows of stones and rocks set facing the direction from which the water flows, and beside the rows of stones and rocks set facing the direction from which the water flows , and in the surrounding rivers Larger stones or rocks inside, or man-made stones or rocks resembling them, are placed in front of the structure in a row transversely to the direction from which the water flow comes, each with a separate fastener. 3. The anti-scouring construction method according to claim 1 or 2, wherein the scouring prevention method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention construction method is characterized in that the scouring prevention method is characterized in that by burying the scouring force directly in the water bottom, the scouring prevention method is securely held down and fixed in place.

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