JPH1150435A - Semi-permeation-type erosion control dam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain and soil from flowing down to the downstream side as much as possible in the latter half of flood from the slit part of a concrete slit dam not to adverse influence to the downstream side. SOLUTION: A slit part 2 reaching down to a riverbed is provided in the water passage part of a concrete dam, and a horizontal beam 6 is installed on the upstream side face of the dam for suppressing a gravel discharge amount from the slit part 2. The upward and downward interval of the horizontal beams 6, 6 is set at 1.0 or 1.5 times larger than the maximum gravel diameter in a lower stage, and 1.0 or 1.5 times larger than an average gravel diameter. The horizontal beam 6 is installed to be replaced with steel-made base materials 7, 7 fixed on the wall face of a dam upstream side in parallel with the slit part 2. Thereby the gravel discharge amount can be suppressed from the slit part 2 at the time of flood and the like, and natural environment of the downstream side is preserved to maintain the landscape. Even in the case where the soil and sand amount of the dam upstream side and size of stone and gravel change, the setting interval of the horizontal beam is modified in response thereto, and thereafter the gravel discharge amount can be regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-permeable sabo dam, and more particularly, to a slit provided in a water passage portion to allow sediment to flow out at normal times, and to maintain a sand storage capacity for trapping debris flow until a debris flow occurs. The present invention relates to an improvement of a concrete slit dam having a function of causing the slit dam to function.

[0002]

2. Description of the Related Art A sabo dam in which an artificial constriction is formed by providing a vertically extending slit portion in a water passage portion is designed to dam up flowing water by the flow contraction effect of the slit portion. As a result, when a flooded area is formed on the upstream side of the dam, the inflowed sediment sinks and accumulates, so that a large amount of sediment can be prevented from flowing out at once in a flood.

[0003] One or several slits are formed in a concrete slit dam, for example, in a water passing part. The lower edge of the slit usually extends to a riverbed, and consideration is given to securing a fishway. Needless to say, in order for the concrete slit dam to exhibit the above-described effects, it is necessary that the gravels contained in the running water have a relatively small particle size as compared with the slit width and do not cause clogging.

[0004] The slit always allows earth and sand and running water to flow,
During floods, etc., sediment will be temporarily deposited on the upstream due to the dam damming effect. In other words, the opening of the dam is only a narrow slit, and the flow of the debris flows rises before the debris flow arrives. It is less likely to be caught in the slit.
In this way, the temporary damping out of large amounts of sediment and boulders during the occurrence of debris flows and floods is suppressed mainly by the damming effect.

[0005] Such a concrete slit dam,
It is particularly effective when the flow rate is large due to the relatively small basin area and the length of the flood is long. On the other hand, if the sedimentary shoulder on the upstream side starts to collapse during the flood reduction period, the accumulated sediment can be discharged during the flood reduction period and during normal times, and the function of controlling the sediment discharge is exhibited.

[0006] The concrete slit dam has attracted attention as a structure taking into consideration the natural environment, and has recently been more and more actively constructed in the sabo business.
In other words, it has not only the above-mentioned sediment control function but also a function as a fishway, which greatly contributes to the preservation of the environment and maintenance of the natural scenery.

[0007]

Due to the above, there are more and more opportunities for concrete slit dams to be planned. However, the problem of discharging sediment at a stretch during the flood mitigation period, that is, the problem of depositing sediment in dam pockets. There is also a problem specific to concrete slit dams in that the outflow of sediment becomes severe later in the flood. Since there is a possibility that a large amount of earth and sand will flow out at once, as a condition for installation, select a place that will not cause problems even if there is a large amount of runoff, or set up a sand pit or the like on the downstream side of the dam. It is necessary to consider it to be attached.

[0008] The above-mentioned sand basin functions as a buffer zone for sediment outflow during a flood, but can be used as a place of rest and a green sabo zone in normal times. However, if a large amount of sediment is discharged, these green belts will be buried in the sediment, and rehabilitation work that requires a lot of labor will be required to restore it as a place for relaxation.

[0009] The above-mentioned slit portion exhibits a dam damming effect at the time of flooding or the like, but various kinds of large and small gravels are mixed in the earth and sand. It is necessary to take some measures when the predetermined slit width cannot be maintained due to sediment accumulation and wear at the slit in a place where sediment movement is active in normal times, but usually the width of the slit is about 2 to 3 m. Is selected. However, if gravel large enough to pass through the slit is discharged from the slit during water reduction, etc., it will be scattered in the green belt, making restoration work extremely difficult.

Incidentally, there are examples in which a large number of wide slits are provided in a concrete dam, and a steel lattice screen is arranged in the slits, or a number of steel materials are provided horizontally in the slits to form a ladder-shaped slit. The former is intended to supplement the function of trapping debris when the width of the slit is too wide, and the latter is to prevent clogging of debris in the slit when the width of the slit is too narrow. The purpose is to prevent debris from entering the slit.

In each of the above examples, the outflow of the boulders is prevented, so that the debris flow containing the boulders can be stopped.
However, the running water is constantly discharged regardless of the amount of water, so it is inevitable that considerable debris will flow downstream during floods and when the amount of water is large. In other words, since the slit is not a damping-up effect by reducing the flow of flowing water, even if a screen is provided, the function of suppressing the outflow of debris during the flood reduction period cannot often be exhibited.

The above-mentioned lattice screen is installed so as to be dropped from above into a vertical groove provided on the opposite side wall of the slit, and the ladder-shaped slit is formed such that both ends of each steel material are opposed to the slit so as to form a ladder shape. It is embedded in the side wall and fixed. The former has the advantage that grid screens can be manufactured in advance in factories, etc., however, it is not easy to carry assembled screens into mountainous areas, and installation work by heavy machinery is inevitable. It can not be denied that will be a large scale. In the latter case, it is almost impossible to replace the steel material when the steel material is to be constructed on site in parallel with the concrete casting or the like, and even when the ladder-shaped opening is to be changed later.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the amount of sand discharged during flood water reduction and not to impede the outflow of running water or harmless sediment in normal times, and to reduce It is possible to control the outflow of relatively large gravel as much as possible and reduce the impact on sandy lands and green areas on the downstream side, and pass through the slit due to changes in the situation on the upstream side of the dam and progress of maintenance projects. An object of the present invention is to provide a semi-permeable sabo dam in which, when the size of gravel changes, the size of gravel to be discharged can be changed later according to the diameter of the gravel.

[0014]

According to the present invention, a concrete dam is provided with a slit portion which reaches a riverbed at a water passage portion, and sediment and running water are constantly circulated in the slit portion, and the dam is dammed up in a flood or the like. The effect slows down the boulders running at the tip of the debris flow that reached the upstream pond, and temporarily accumulated sediment in the pond, causing a temporary large outflow of sediment and boulders during debris flows and floods. Applied to concrete slit dams that can suppress the outflow of water. The feature is, referring to FIG.
On the upstream side of the dam, cross beams extending across the slit in the left and right direction to suppress the amount of sand and gravel from the slit 2
Are arranged in multiple stages. The vertical spacing of this cross beam is
It is 1.0 to 1.5 times the maximum diameter of the rubble expected to reach the dam at the lower part of the slit part 2, and 1.0 to 1 times the average diameter of the rubble expected to reach the upper part to the middle part. .5 times. Thus, the cross beam 6
The boulder running at the tip of the debris flow is prevented as much as possible by the lower cross beam, and the relatively large debris mixed in the subsequent sediment flow is prevented to some extent in the middle or upper stage, while Small pebbles with little effect can flow out of the slit part 2 in normal times,
In addition, the sediment runoff during the flood reduction period was to be suppressed.

The cross beam 6 is a steel material, and steel bases 7, 7 extending vertically in parallel with the slits are disposed on the left and right sides of the slit 2 on the upstream side surface of the dam. Is fixed to the cross beam 6.

It is preferable that the above-mentioned cross beam 6 is detachably fixed to a steel base material 7. Further, it is preferable that the steel base 7 is also detachably fixed on the upstream side surface of the dam.

[0017]

According to the present invention, harmless sediment and running water are always circulated in the slit section provided with the cross beam, and during floods, etc., flooding ponds are generated upstream by the dam damping-up effect. The boulders can be decelerated at the pond and kept upstream. Therefore, the amount of sand and gravel from the slit can be controlled during a flood, etc., and the natural environment on the downstream side is preserved and the landscape is maintained. Of course, the slit is formed so as to reach the riverbed, so that a fishway is secured and the balance of the natural ecosystem can be maintained.

In the lower part of the slit, small but relatively large boulders are gathered on the riverbed and are likely to flow out. Therefore, in this part, the maximum diameter of boulders expected to reach the dam is 1.0 to 1.0. Cross beams are provided at 1.5 times the vertical spacing, thereby preventing the flow of undesired rubble. In the upper and middle tiers, there is only rubble that can pass through the horizontal beams that are selected to be 1.0 to 1.5 times the average diameter of rubble expected to reach the dam. Outflow is suppressed.

The cross beam is a steel material and is disposed on the upstream side surface of the dam, and is attached to a steel base material fixed to the left and right of the slit. This not only simplifies the mounting structure of the cross beams, but also allows most of the load received from the debris by the cross beams to act on the dam retaining wall, and damage and outflow of the steel base material and the cross beams is possible. Decrease.

If the cross beam is detachably fixed to the steel base or the steel base is detachably fixed on the upstream side of the dam, replacement work of the steel base and the cross beam is facilitated. . Therefore, it is possible to subsequently adjust the amount of sand and gravel so that the interval between the cross beams can be changed according to the change in the amount of sediment and the size of rubble on the upstream side of the dam.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A translucent sabo dam according to the present invention will be described below in detail with reference to the drawings showing an embodiment thereof. Fig. 2 shows the riverbed 1
It is the front view which looked at the concrete slit dam 3 provided with the slit part 2 which reaches to it from the downstream. In this example, as shown in the plan view of FIG. 3, a concrete slit dam 3 as a gravity dam and a sub dam 4 on the downstream side are provided. In the figure, this secondary dam is also a semi-permeable sabo dam.

The upper end of the dam in FIG. 2 has a width of about 40 m and a height of about 15 m. The width of the slit 2 provided in such a concrete dam is 2 m.
m or 3 m in most cases. Further, two or more slit portions may be provided as necessary, but one slit portion is provided in the illustrated example.

As shown in FIG. 1 (a), which is the back side of FIG. 2, and FIG. 1 (b), a cross section of the concrete slit dam 3 is provided on the upstream side of the concrete slit dam 3. A cross beam 6 is attached. The large number of cross beams 6, 6 are fixed to the left and right sides of the slit portion 2 on the upstream side surface of the dam in parallel with the slit portion.
It is attached to straddle.

Referring to FIG. 4A, the base material 7 is also a steel material, for example, an H-shaped steel. The H-section steel has its web portion 7a perpendicular to the retaining wall surface 3a, and the lower flange portion 7b is detachably fixed to a seat plate member 3b provided on the retaining wall surface by an anchor bolt 7c or the like. The cross beam 6 may also be a shaped steel, but in the illustrated example, a steel pipe is used, and the U-bolt 6 is used.
By a, it is detachably fixed to the upper flange portion 7d. Regardless of which material is used for the cross beam 6 and the steel base material 7, a fastening device such as a bolt or a U-bolt or a fastener may be used, and the web portion 7 a of the steel base material 7 is used to fix the cross beam 6. Is provided with a bolt hole in the upper flange portion 7d.

The cross beams 6 are arranged such that the upper and lower gaps are different between the upper and lower portions of the slit portion 2. That is, in the lower stage, the stones are arranged at intervals of 1.0 to 1.5 times the maximum diameter of the gravels expected to reach this dam, and in the upper to middle stages, the average gravels diameter is 1.0
Or 1.5 times as long.

The reason that the vertical spacing of the cross beams 6, 6 is selected to be 1.0 to 1.5 times the diameter of the rubble expected to reach the dam is as described by the present inventors. It is based on results. In other words, if any multiple within this range is selected, the outflow rate is maximized for small-sized rubble due to the mutual interaction of rubble and the like without impairing the sediment discharging function in the slit portion. On the other hand, it is based on the finding that the outflow rate of undesired large-sized rubble is minimized as much as possible.

As an example, Table 1 shows the ratio of the diameter of rubble reaching the slit dam and the number of the rubble mixed during the flood. In this case, the average gravel diameter is about 60 cm, and when the maximum diameter is 150 cm, the aperture (vertical interval) of the cross beam is 60 cm to 90 cm in the upper and middle stages.
In the range of 150 cm to 2
It will be set in the range of 25 cm.

[Table 1]

Therefore, the opening of the cross beam is set to 60 cm in the upper and middle sections of the slit portion, and 150 cm in the lower section.
Assuming m, the passage rate of the slit portion at each gravel diameter is as shown in the lowermost row of Table 1 above. That is, most of the diameter of 50 cm or less passes, 30% of the diameter of 50 cm to 100 cm remains on the upstream side, and 80% of the diameter of 100 cm or more does not flow downstream. Although this is only an example, it can be understood that the effect of preventing the boulders from flowing away is high. In this case, in calculation, the average diameter of the rubble that passes through the slit is about 50 cm, and the average diameter of the rubble that cannot pass through the slit is about 95 cm, and the tendency of the effect by the cross beam is grasped. be able to.

Various types of rubble will be accumulated on the upstream side of the dam during floods and the like. However, since artificial stenosis is formed by slits to dam up running water, Debris tends to settle in the flooded area formed upstream of the area. Furthermore, the boulders running at the tip of the debris flow generated prior to the sediment flow are remarkably decelerated, so that the boulders are less likely to be caught in the slit portion 2, and relatively small subsequent debris enters the slit portion. Of course, if the boulder reaches the slit, it is near the riverbed, and it can of course be sufficiently prevented even if the vertical spacing of the cross beams is wide.

It is known that heavier rubble forms a lower layer and a lower rubble forms an upper layer in the pond. Therefore, in the lower section of the slit portion 2, relatively large rubble is smaller than boulder. They gather on the riverbed and try to run off.
In this area, the cross beams installed at the desired intervals prevent the flow of undesirably large gravels. The same applies to the upper stage and the middle stage. However, since the width of the slit portion 2 is originally 2 m to 3 m, a vertical beam that intersects the horizontal beam 6 is generally not often required.

FIG. 5 shows the behavior of gravel and sediment from normal times to the flood reduction period. In normal times, as shown in FIG.
Pass through. At the time of the flood, sediment is deposited on the upstream flooding pond 8 as shown in FIG.
It is possible to prevent the earth and sand as shown by the imaginary line 10 from flowing out at once. As shown in FIG. 5 (c), the sediment shoulder 9 at the location of the flood pond starts to collapse during the flood reduction period, but the outflow is controlled by the cross beam 6 of the slit portion 2,
An adverse effect on the downstream side due to the outflow of the debris from the slit portion 2 is suppressed as much as possible.

The amount and time of the outflow of the earth and sand from the slit portion depend on many conditions such as the position and shape of the slit portion, sediment shape and particle size, flood waveform and sediment concentration, and topography. However, the vertical spacing of the cross beams can be changed later according to the change in the amount of sediment and the size of rubble and the progress of the upstream maintenance project.

This is because the cross beams and the steel base material are made detachable, but it is possible to adjust the amount of sand and gravel by changing the arrangement of the cross beams according to the flow gravel diameter. Become. For example, cross beams can be added or thinned out later. Of course, it is needless to say that if the cross beam or the like is damaged, it can be replaced by a simple replacement work to regenerate the function as the slit dam.

According to the translucent sabo dam of the above construction, an artificial constriction is formed by the slit provided in the water passage so that flowing water is dammed up by the flow contraction effect of the slit, and the upstream of the dam. A flooded area is formed on the side to promote the sedimentation of inflow sediment, preventing not only a large amount of sediment and driftwood from flowing out at the same time during a flood, but also a function of suppressing sediment runoff during the flood reduction period.

Therefore, the dispersion of large rubble on the downstream side is reduced, the environmental protection and the natural scenery are maintained, and the slit effect is exerted by the slit part whose lower edge extends to the riverbed. In the present invention as well, a fishway can be secured, and the ecosystem can be maintained and balanced. By the way, the rubble and sediment deposited on the upstream side of the dam are dug up using heavy equipment etc. after checking the timing, but before the work, the water can be drained from the upstream side through the slit part, so In addition, it is easy to treat and carry out the drained sediment.

The cross beam is attached to a steel base material disposed on the left and right sides of the slit portion. In short, it is only necessary that the cross beam does not fall off the steel base material, so that the mounting structure of the cross beam is simplified. Needless to say. The steel substrate is on the upstream side of the dam, and the majority of the load received by the cross beam from the debris is received by the dam retaining wall, reducing the likelihood that the steel substrate or cross beam will break or flow out.

The cross beam may be semi-permanently fixed to the steel base material and the steel base material may be semi-permanently fixed to the dam retaining wall. In this case, it is preferable that at least one of them has a detachable mounting structure. For example, when the steel base is not shown, but is directly fixed to the dam retaining wall, the cross beam 6 may be fixed to the steel base 7 by a detachable securing device as described above.

As shown in FIG. 4B, the cross beam 6 is connected to a steel base 7.
In order to fix the base member 7 by welding, the steel base member 7 may have a mounting structure as shown in FIG. In this case, if the steel base material is removed from the dam retaining wall, it is needless to say that the cross beams are also integrally removed.However, unlike the wide grid screen described in the section of the prior art, the handling is relatively small. Easy.

[Brief description of the drawings]

FIG. 1 shows the structure of a dam retaining wall in a semi-permeable sabo dam according to the present invention, in which (a) is a wearing state diagram showing an arrangement of cross beams and the like attached to an upstream side wall, and (b) is a wearing state diagram (a). 2) is a cross-sectional view taken along line II of FIG.

FIG. 2 is a front view seen from the downstream side of a concrete slit dam in which a horizontal beam is provided in a slit portion.

FIG. 3 is a plan view of a slit dam installed together with a sub dam.

FIG. 4 shows a fixing structure of a cross beam and a steel base material,
(A) is an attached state in which both are detachable, and is a cross-sectional view taken along the line IV-IV in (b) of FIG. 1, and (b) is a fixed state view when the cross beam is welded to a steel base material.

FIG. 5 shows the behavior of soil and the like in the concrete slit dam, (a) shows the state of flow during normal times, (b) shows the state during a flood, and (c) shows the state during the flood reduction period. Schematic.

[Explanation of symbols]

1 ... riverbed, 2 ... slit part, 3 ... concrete slit dam, 6 ... cross beam, 7 ... steel base material.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroshi Aramaki 3-6-24 Uozaki Minamicho, Higashinada-ku, Kobe City, Hyogo Prefecture Inside Kawasaki Construction Materials Co., Ltd. (72) Inventor Takahisa Mizuyama 3 Shinjocho, Ibaraki City, Osaka Prefecture −14

Claims (4)

[Claims] 1. A slit section which reaches a riverbed is provided in a water passage section of a concrete dam, and sediment and running water are constantly circulated in the slit section. In a flood or the like, a flood pond generated on the upstream side due to a dam damaging effect. To slow down boulders running at the tip of the debris flow that reached the river and temporarily deposit sediment in the flood basin to prevent temporary massive outflow of boulders and boulders during debris flows and floods. In the concrete slit dam, on the upstream side of the dam, a cross beam straddling in the left-right direction of the slit portion is arranged in a multi-step shape in order to suppress the amount of sand and gravel from the slit portion. The gap is estimated to reach 1.0 to 1.5 times the maximum diameter of rubble expected to reach the dam in the lower section of the slit, and to reach the dam in the upper to middle sections. It is selected to be 1.0 to 1.5 times the average diameter of the debris, and the boulders running at the tip of the debris flow are blocked as much as possible by the lower cross beam, and the relatively large debris mixed into the subsequent sediment flow Semi-permeable sabo, characterized by being able to prevent the small pebbles with little influence on the downstream side from flowing out of the slit portion in normal times, and to suppress the outflow of sediment during the flood reduction period dam. 2. The cross beam is made of a steel material, and a steel base extending vertically in parallel with the slit is disposed on the upstream side of the dam on the left and right sides of the slit. The translucent sabo dam according to claim 1, wherein is fixed. 3. The translucent sabo dam according to claim 1, wherein the cross beam is detachably fixed to the steel base. 4. The translucent sabo dam according to claim 1, wherein the steel substrate is detachably fixed on an upstream side surface of the dam.