JP2020117962A - Levee body seepage destruction suppression structure - Google Patents

Abstract

To provide a levee body seepage destruction suppression structure that can suppress seepage destruction of a levee body installed around a reservoir and enables reduction in construction costs/construction periods as compared with the conventional structures.SOLUTION: A levee body seepage destruction suppression structure includes: a steel sheet pile wall 15a installed on an upstream slope face 10b on the upstream side of a levee body 10 and at a high-water position 12 having a height equal to a normal high-water level of a reservoir 11 or in the vicinity thereof, the steel sheet pile wall installed along a direction, in which the levee body 10 extends, and so as to protrude upward; and a protection part 20 for protecting the upstream slope face 10b over the high-water position 12 or the vicinity thereof, the protection part 20 also being a filled type seepage prevention part 21 made of an impermeable material filled between the steel sheet pile wall 15a and the upstream slope face 10b. Thereby, seepage destruction of the levee body 10 can be suppressed and construction costs/construction periods can be reduced as compared with the conventional structures.SELECTED DRAWING: Figure 1

Description

The present invention relates to a structure for suppressing permeation failure of a bank.

In recent years, a large number of river dikes and reservoir ponds have been destroyed due to large-scale earthquakes, and several large-scale earthquakes are expected to occur, so seismic reinforcement of dikes is becoming more important. ..

Based on such a background, a levee (bank body) reinforcing technique using a steel sheet pile has been proposed so far (see, for example, Patent Documents 1 to 3).
In the seismic performance reinforcing structure of a dam body described in Patent Document 1, a reinforcing plate-like body formed of steel sheet piles in two columns in the longitudinal direction is formed at almost the center of an embankment dam such as an earth fill dam or a reservoir. It is embedded and has a double shut-off structure in which the upper end portions of both reinforcing plate-like bodies are connected by a connecting member at predetermined intervals.

In addition, in the embankment reinforcement structure described in Patent Document 2, one or more rows of underground steel wall bodies are provided along the continuous direction of the embankment within the range of the substantially top end of the continuous embankment, and the embankment. On at least one of the slopes, so as to protect the slope, diagonal slant is provided so as to become lower as it goes away from the top of the embankment, the lower part of the diagonal is below the embankment. It is placed in the ground.

In addition, in the embankment reinforcement structure described in Patent Document 3, a first suppressing member and a second suppressing member provided along the first slope and the second slope of the embankment, and the first suppressing member. And a plurality of connecting members that connect the second restraining member to each other, and the first restraining member and the second restraining member are arranged on the first slope and the second slope. The slope surface portion and the root insertion portion embedded in the ground are provided, and the slope surface portion and the root insertion portion are continuously formed in a substantially linear shape.

JP, 2003-321826, A JP, 2011-214254, A JP, 2005-221994, A

By the way, "Agricultural Civil Engineering Society Transactions of JSIDRE No. 218,
As described in 127-137 (2002.4), "Causes of agricultural pond destruction due to heavy rain and characteristics of disasters", there are about 200,000 to 250,000 agricultural ponds nationwide. , It is a valuable water resource not only for agriculture but also for the region. However, there are many ponds due to their old construction and aging, and there is concern about damage to the ponds during heavy rainfall. Damage to the pond includes damage to the levee body due to slippage and erosion, leakage of the levee body and foundation, and damage to incidental structures, but most of the damage is due to heavy rainfall, with a proportion of 95% or more. Has become.
It is said that infiltration damage is the most common cause of damage to the bank of a pond due to heavy rain. This infiltration failure is because the upstream slope on the pond side (reservoir side or upstream side) from the full water level to the upper part of the levee body serves as a leakage entry port into the levee body that causes infiltration failure. On the upstream slope of the dam body, repeated dryness and wetness due to vertical movement of the water level, soil particles sucked out to the water side, and erosion due to waves for a long period of time, the ground strength of the dam body decreased, and water pressure acted due to rising water level. In some cases, it may be destroyed locally.

On the other hand, in the seismic performance reinforcing structure of the dam body described in Patent Document 1, the reinforcing plate bodies are embedded in two columns in the longitudinal direction of the substantially central portion of the dam body, and the upper end of the reinforcing plate body is provided. Although the parts are connected by a connecting member at predetermined intervals, it is impossible to prevent permeation from the upstream slope, which is the starting point of permeation failure.
Further, in the embankment reinforcement structure described in Patent Document 2, when a diagonal member is provided so as to protect the downstream slope, the embankment slope is collapsed or the ground is scourd due to flooding during flooding. Although it can be prevented, it does not function as a protection method against osmotic destruction. Although it is shown that diagonal members are installed on the upstream slope, it is necessary to place diagonal members on the ground below the dam body, which impedes the water flow below the dam body and affects the water environment. Will be given.
Further, in the embankment reinforcement structure described in Patent Document 3, as a protection of the slope, a restraining member is provided along the two slopes on both sides of the dam body, and the two restraining members are fastened by a plurality of connecting members. Since it is necessary to embed a connecting material inside the body and reinforcement along two slopes, the reinforcing structure becomes large and the construction cost and construction period increase.

The present invention has been made in view of the above circumstances, and is capable of suppressing permeation failure of a dam body provided around a reservoir, and compared with conventional methods for reinforcing a dam body, which are particularly aimed at earthquake resistance measures, compared with conventional heavy rain methods. The objective is to provide a structure for preventing erosion damage to a levee body that can shorten the construction cost and construction period by specializing in preventing osmotic damage at times.

In order to achieve the above-mentioned object, the structure for preventing osmotic failure of a dam body according to the present invention is a structure for suppressing osmotic damage of a dam body that suppresses osmotic damage of a dam body provided on at least part of the outer periphery of a reservoir
Assuming that the reservoir side is the upstream side of the bank body, the steel wall is on the upstream slope of the upstream side of the bank body and at or near the full water position of a height equal to the full water level of the reservoir. Is installed along the extending direction of the levee body and so as to project upward,
A protection unit for protecting the upstream slope above the full water position or its vicinity is provided,
The protective portion is a filling-type permeation preventive portion made of an impermeable material filled between the steel wall and the upstream slope.

Here, a steel sheet pile wall formed by connecting a plurality of steel sheet piles is preferably used as the steel wall, but the steel sheet wall is not limited to this. For example, a steel pipe sheet pile wall formed by connecting a plurality of steel pipe sheet piles, a steel wall formed by connecting a plurality of steel sheet piles and steel pipe sheet piles, or the like may be used.
In addition, "the vicinity" means an upstream slope and a range within 1 m in the vertical direction from the full water position.
Further, examples of the “filling type permeation preventive portion made of an impermeable material” include, but are not limited to, a filling type prevention portion formed of blade metal, soil cement or bentonite.

According to the present invention, the steel wall projects upward along the extending direction of the dam body at or near the full-fill position on the upstream slope of the dam body and at the height equal to the constant full-water level of the reservoir. Installed on the upper surface, or a protection part for protecting the upstream slope above the full water position or its vicinity, and the protection part is made of an impermeable material filled between the steel wall and the upstream slope. Since it is the filling type permeation prevention unit, the filling type permeation prevention unit can prevent permeation breakdown of the bank body by preventing permeation during water increase on the upstream slope that is the starting point of permeation destruction.
Further, since the filling type permeation preventive portion is provided by filling the impermeable material between the steel wall and the upstream slope of the dam body, it is not necessary to protect the entire slope, which is more than conventional. Construction cost and construction period can be shortened.

Further, another levee body osmotic failure suppression structure of the present invention is a levee body osmotic failure suppression structure for suppressing osmotic failure of a dam body provided in at least a part of the outer periphery of a reservoir,
Assuming that the reservoir side is the upstream side of the bank body, the steel wall is on the upstream slope of the upstream side of the bank body and at or near the full water position of a height equal to the full water level of the reservoir. Is installed along the extending direction of the levee body and so as to project upward,
A protection unit for protecting the upstream slope above the full water position or its vicinity is provided,
The protection part includes a surface type permeation preventive part made of a water impermeable material provided along the upstream slope above the full water position or its vicinity, and the steel wall and the surface type permeation preventive part. And a filling-type permeation-preventing portion made of a water-impermeable material filled in between.

Here, as the "surface type permeation preventive part made of water-impermeable material", for example, a concrete block installed on the upstream slope, sprayed concrete constructed on the upstream slope, impermeable water covering the upstream slope Examples include seats and geotextiles, but are not limited thereto.

In the present invention, the protective part is a surface type permeation preventive part made of a water impermeable material provided along the upstream slope above the full water position or its vicinity, the steel wall and the surface type. Since it has a filling-type permeation preventive part made of a water impermeable material filled between the permeation preventive part and the upstream slope, which is the starting point of permeation failure, it prevents permeation at the time of water increase and the permeation failure of the dam body. Can be suppressed. Also, if only the surface type permeation preventive part is installed on the upstream slope, the surface type permeation preventive part may be peeled off from the upstream slope due to the water flow. By covering and protecting the upper side of the permeation preventive portion, the surface type permeation preventive portion can be firmly fixed to the upstream slope position.
Further, the surface type permeation preventive portion is provided along the upstream slope, and the filling type permeation preventive portion is provided by filling an impermeable material between the steel wall and the surface type permeation preventive portion. Since it is not necessary to protect the entire slope, the construction cost and construction period can be shortened compared to the conventional method.

Moreover, in the said structure of this invention, the upper end of the said steel wall, the upper surface of the said filling type penetration prevention part, and the top end of the said bank may be paved integrally.
When the surface type permeation preventive part is provided on the upstream slope of the bank, the upper end of the surface type permeation preventive part, the upper end of the steel wall, the upper surface of the filling type permeation preventive part and the top end of the bank body are included. May be paved integrally.

According to such a configuration, the upper end of the steel wall, the upper surface of the filling-type permeation preventive portion, and the top of the bank are integrally paved, so that the upstream slope from the top of the bank due to overflow water and Water leakage into the bank can be prevented.

Further, in the above configuration of the present invention, the lower end of the steel wall is located below the full water position, and is supported by a support member installed below the lower end of the steel wall,
The support member may be a plurality of steel members provided at predetermined intervals in the extending direction of the steel wall, or a water-permeable steel wall extending in the extending direction of the steel wall.

According to such a configuration, the steel wall is installed at the position where the upstream slope and the full water level always intersect with each other, so that the amount of stored water in the entire pond does not decrease. Furthermore, the lower end of the steel wall is installed below the lower end, because it is supported by a plurality of steel members or a supporting member made of a water permeable steel wall, the steel wall can be reliably installed, It does not hinder the groundwater flow in the dam and in the soft layer just below the dam.

Further, in the configuration of the present invention, a structure extending in the width direction of the bank is provided inside the bank,
When the support member is a plurality of steel members provided at predetermined intervals in the extending direction of the steel wall, the steel member is installed in a position to avoid the structure,
When the support member is a water-permeable steel wall extending in the extending direction of the steel wall, it is located above the structure among a plurality of steel sheet piles that compose the water-permeable steel wall. The lower end portion of the steel sheet pile may not reach the structure.

Here, the structure provided inside the levee body includes, but is not limited to, a bottom gutter.

With such a configuration, it is possible to prevent the steel member or the water permeable steel wall installed inside the bank from interfering with the structure and damaging the structure.

According to the present invention, since it is specialized in the reinforcement construction method for suppressing the seepage failure of the bank body provided around the reservoir, the construction cost and construction period can be shortened as compared with the conventional construction method for reinforcing the entire bank body.

It is a cross-sectional view which shows the permeation|rupture destruction prevention structure of the embankment which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the penetration failure of a bank body. 1 is a perspective view showing a steel sheet pile wall of a first example, showing a structure for suppressing permeation failure of an embankment according to a first embodiment of the present invention. FIG. FIG. 3 is a sectional view showing a state in which the steel sheet pile wall of the first example is installed. It is a perspective view showing the steel sheet pile wall of the 2nd example. FIG. 7 is a sectional view showing a state in which the steel sheet pile wall of the second example is installed. It is a cross-sectional view which shows the permeation|rupture destruction prevention structure of the embankment which concerns on the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a transverse cross-sectional view showing a structure for suppressing permeation failure of a dam body according to the first embodiment.
First, before describing the levee body osmosis failure suppression structure of the first embodiment, the levee body penetration failure will be described with reference to FIG.

As shown in FIG. 2, the infiltration failure route is a route that reaches a downstream slope by flowing down a relatively shallow portion of the bank from the upstream slope above the full water level.
Holes with a diameter of several cm and a depth of several tens of cm are often observed near the upper slope of the full water level. It is considered that such a hole did not occur in a short time, but it occurred over a long period of time due to repeated dryness and wetness due to vertical movement of the water storage level, suction of soil particles to the water storage side, erosion due to waves, etc. When the water pressure acts on the upstream slope due to such erosion for a long period of time and the ground strength of the dam decreases, and the water level rises during heavy rainfall, etc., the above-mentioned holes will cause the water leakage entrance to the inside of the dam and the downstream slope. When there is a bottom gutter near the foundation ground, especially in the vicinity, it becomes a structural change point in the levee body and unequal subsidence is likely to occur. As a method of repairing the upstream slope that serves as a seepage entrance, concrete blocks may be laid on the surface of the location, but the concrete blocks may be washed away by the water flow, or the bank that supports the concrete blocks. When the body collapses, the concrete block may flow out together with the dam body, making it impossible to maintain the top height of the dam body.

Therefore, in this embodiment, the following osmotic fracture suppression structure is adopted.
First, in the present embodiment, the outer periphery of the reservoir 11 is surrounded by the bank 10 in a plan view (not shown), but the bank 10 may be provided on at least part of the outer periphery of the reservoir.
In this case, the portion where the bank body 10 is not provided is the existing ground such as the ground and is formed by the bank body or a protrusion having a height higher than that. Therefore, the outer circumference of the reservoir is surrounded by the earth structure formed by the bank and the protrusion. Note that the earth structure is basically a structure formed mainly of earth, and includes those provided with various facilities or articles formed of concrete or the like inside or on the surface thereof.

Further, as shown in FIG. 1, the soft layer 30 is directly below the bank 10, and the support layer 40 or the bedrock layer is directly below the soft layer 30. The soft layer 30 and the support layer 40 are continuous below the reservoir 11.
In this embodiment, the bank 10 is provided on the upper surface of the soft layer 30, but when the soft layer 30 is not provided, the bank 10 is provided directly on the upper surface of the support layer 40.

When the reservoir 11 side (inside) is the upstream side and the outside is the downstream side across the crown 10a of the bank 10, the reservoir 11 exists because water is stored on the upstream side. Moreover, the bank body 10 is provided with an upstream slope 10b on the upstream side and a downstream slope 10c on the downstream side with the top end 10a interposed therebetween. The upstream slope 10b and the downstream slope 10c have the same inclination angle with respect to the ground surface (the upper surface of the soft layer 30), but the upstream slope 10b and the downstream slope 10c may have different inclination angles.

In addition, a steel sheet pile wall (steel wall) 15a is installed so as to project upward on the upstream slope 10b of the bank body 10 and at or near the full water position 12 having a height equal to the normal full water level of the reservoir 11. There is.
The lower end of the steel sheet pile wall 15 a is located inside the bank 10 about 1 m below the full water position 12. The lower end position of the steel sheet pile wall 15a may be matched with the full water position, but due to the occurrence of construction error in the depth direction of the steel sheet pile wall 15a, fluctuation of the water storage level, weathering, etc. Considering that fluctuations may occur, the lower end of the steel sheet pile wall 15a is about 1 m or more in order to surely protect the filling type permeation preventive portion with the steel sheet pile wall at a height equal to or higher than the full water position, and the bank body 10 It is preferable to put the roots inside.
The lower end of the steel sheet pile wall 15a is supported by a support member 18 installed below the lower end.

For example, there are two examples of the support member 18. The support member 18 of the first example is a water permeable steel sheet pile wall (water permeable steel wall) 15b.
As shown in FIGS. 3 and 4, the water permeable steel sheet pile wall 15b and the steel sheet pile wall 15a form a steel sheet pile wall 15 formed integrally.
That is, first, the steel sheet pile wall 15 is formed by connecting a plurality of hat-shaped steel sheet piles 16.
The steel sheet pile 16 includes a web 16a, flanges 16b formed at both ends of the web 16a, and an arm 16c formed at an end of the flange 16b opposite to the web 16a, and a tip of the arm 16c. A joint 16d is formed on the portion.
Then, the adjacent steel sheet piles 16, 16 are connected by fitting the joints 16d, 16d to each other, whereby the steel sheet pile wall 15 is formed.

The web 16a is integrally formed by an upper web 16a1 and a lower web 16a2, and a plurality (a large number) of elliptical or circular water-permeable holes 17 are provided in the lower web 16a2 at predetermined intervals in the vertical and horizontal directions. Therefore, the water permeation hole 17 is not provided in the upper web 16a1.
The lower portion having the lower web 16a2 provided with the water perforations 17 is the water permeable steel sheet pile wall 15b, and the upper portion having the upper web 16a1 is the steel sheet pile wall 15a.

Although the steel sheet pile wall 15a and the water permeable steel sheet pile wall 15b are integrally formed, they may be separately formed and connected by welding or the like.
Further, the steel sheet pile constituting the steel sheet pile wall 15 is not limited to the hat-shaped steel sheet pile, and may be a U-shaped steel sheet pile or a straight steel sheet pile.

Further, as shown in FIGS. 5 and 6, a second example of the support member 18 is a plurality of steel members provided at predetermined intervals in the extending direction of the steel sheet pile wall 15a (left and right direction in FIGS. 5 and 6). (Steel sheet pile) 15c, and the steel sheet pile wall 15 is constituted by the steel sheet pile wall 15a and the steel member 15c. That is, the steel sheet pile wall 15a and the steel member 15c are formed in the same cross section and are continuous in the vertical direction.
The steel sheet pile wall 15 is formed by connecting a plurality of hat-shaped steel sheet piles 16 as in the first example described above.
The steel sheet pile 16 includes a web 16a, flanges 16b formed at both ends of the web 16a, and an arm 16c formed at an end of the flange 16b opposite to the web 16a, and a tip of the arm 16c. A joint 16d is formed on the portion.
Then, the adjacent steel sheet piles 16, 16 are connected by fitting the joints 16d, 16d to each other, whereby the steel sheet pile wall 15 is formed.

Among the plurality of steel sheet piles 16 constituting the steel sheet pile wall 15, a predetermined steel sheet pile 16 has a length in the up-down direction longer than the other steel sheet piles 16 and protrudes downward, The projecting portion serves as a steel member 15c and supports the steel sheet pile wall 15a from below. Such steel members 15c are integrally formed with the steel sheet pile wall 15a, and a plurality of such steel members 15c are provided at predetermined intervals in the extending direction of the steel sheet pile wall 15a.

Although the steel sheet pile wall 15a and the steel member 15c are integrally formed, they may be separately formed and connected by welding or the like. The steel member formed separately may be a hat-shaped member. The sheet pile is not limited to the steel sheet pile, and may be a steel sheet pile having another shape, a steel pipe sheet pile, or the like.
Further, the steel sheet pile constituting the steel sheet pile wall 15 is not limited to the hat-shaped steel sheet pile, and may be a U-shaped steel sheet pile or a straight steel sheet pile.

As shown in FIG. 1, the steel sheet pile wall 15 having such a configuration is vertically installed on the upstream slope 10b of the dam body 10 and at or near the full water position 12 having a height equal to the constant full water level of the reservoir 11. (Pasting), the upper steel sheet pile wall 15a projects upward from the full water position 12, and the lower end of the steel sheet pile wall 15a is located about 1 m below the full water position 12.
The lower end of the steel sheet pile wall 15a is supported by the water permeable steel sheet pile wall 15b or the steel member 15c which is the lower support member 18, and the lower end of the water permeable steel sheet pile wall 15b or the steel member 15c forms the soft layer 30. Although it penetrates and is in contact with or close to the upper surface of the support layer 40 immediately below it, it may be rooted in the support layer 40.
In addition, in FIG. 1, the case where the support member 18 is the water permeable steel sheet pile wall 15b is shown.

Further, the upstream slope 10 b above the full water position 12 of the bank 10 or the vicinity thereof is protected by the protection unit 20.
The protection part 20 is a filling-type permeation prevention part 21 made of an impermeable material, which is filled in a space between the steel sheet pile wall 15a and the upstream slope 10b. The water impermeable material is preferably blade metal soil, soil cement, bentonite, or the like, but is not limited thereto. Such a filling type permeation preventive portion 21 is formed in a right-angled triangular cross section, and is in close contact with the surface of the steel sheet pile wall 15a facing the bank 10 side and the upstream slope 10b.

Further, the upper end of the steel sheet pile wall 15a, the upper surface of the filling type permeation preventive portion 21, and the top end 10a of the bank 10 are at substantially the same height position. The upper surface and the top 10a of the bank 10 are integrally paved to form a paving portion 22. The pavement portion 22 has a predetermined thickness, and its upper surface is formed substantially horizontally. Note that examples of the paving material used for paving include concrete and asphalt, but are not limited thereto.

Further, as shown in FIG. 6, a structure 25 such as a bottom gutter extending in the width direction (direction orthogonal to the paper surface in FIG. 6) orthogonal to the extending direction of the dam body 10 is provided at the bottom of the dam body 10. Is provided and when the support member 18 is a plurality of steel members 15c provided at predetermined intervals in the extending direction of the steel sheet pile wall 15a, the steel member 15c includes the structure 25. It is installed in a position to avoid. The bottom gutter is guided by the water taken from the water intake holes of the slant pipe buried along the upstream slope 10b of the bank 10.

In addition, as shown in FIG. 4, a structure 25 such as a bottom gutter that extends in the width direction orthogonal to the extending direction of the dam body 10 (direction orthogonal to the paper surface in FIG. 4) is provided at the bottom of the dam body 10. Is provided and when the support member 18 is the water permeable steel sheet pile wall 15b, among the plurality of steel sheet piles 16 that compose the water permeable steel sheet pile wall 15b, it is located above the structure 25. The lower end portion of the steel sheet pile 16 does not reach the structure 25 and is close to the structure 25.

As described above, according to the present embodiment, the steel sheet pile wall 15a of the bank 10 is located at or near the full fill position 12 on the upstream slope 10b of the dam 10 and at the height equal to the constant full water level of the reservoir 11. The protection part 20 is installed along the extending direction and so as to project upward, and the protection part 20 for protecting the upstream slope 10b above the full water position 12 or its vicinity is provided, and the protection part 20 serves as the steel sheet pile wall 15a. Since the filling type permeation preventive portion 21 made of a water impermeable material is filled between the upstream side slope 10b and the upstream slope 10b, the filling type permeation prevention portion 21 causes the upstream slope 10b, which is the starting point of the permeation failure, at the time of increasing water. It is possible to prevent the penetration of the dam body 10 and prevent the breakage of the bank 10. As a result, it is possible to prevent sliding failure in which the upper portion of the dam body 10 collapses along the permeation failure surface in the dam body.
Further, since the filling type permeation preventive portion 21 is provided by filling the impermeable material between the steel sheet pile wall 15a and the upstream slope 10b of the bank 10, the bank 10 is excavated and deteriorated. Large-scale earthwork such as substituting the ground material or injecting a chemical solution to harden the ground is unnecessary, and the construction cost and construction period can be shortened compared to the conventional one.

Further, the upper end of the steel sheet pile wall 15a, the upper surface of the filling-type permeation preventive portion 21, and the top end 10a of the bank 10 are at substantially the same height position, and since these are paved integrally, it is possible that the overflow water causes It is possible to prevent water leakage from the top of the bank to the upstream slope 10b and the bank.
Further, since the steel sheet pile wall 15a is installed at a position where the upstream slope 10b and the full water level always intersect, the amount of stored water in the entire pond does not decrease. Furthermore, since the lower end of the steel sheet pile wall 15a is supported by the plurality of steel members 15c installed below the lower end or the water permeable steel wall 15b, the steel sheet pile wall 15a can be reliably installed, The groundwater flow in the bank 10 and in the soft layer 30 immediately below the bank 10 is not hindered. In order to more firmly support the steel sheet pile wall 15a by the support member 18, a connecting member using H-shaped steel or the like is provided across the extending direction of the steel sheet pile wall 15a including the upper portion of the support member 18. When connecting the steel sheet pile walls 15a or constructing the pavement portion 22, the steel sheet piles (water permeable sheets) to be the supporting members 18 are formed by connecting the top ends of the steel sheet pile walls 15a with a connecting member or coping. The steel sheet pile wall 15b or the steel member 15c) may be connected to another steel sheet pile 16.

Further, when a structure 25 such as a bottom gutter extending in the width direction of the dam body 10 is provided inside the dam body 10, a plurality of steels provided at predetermined intervals in the extending direction of the steel sheet pile wall 15a. The member 15c is installed above the structure 25 among the plurality of steel sheet piles 16 that are installed at positions avoiding the structure 25 and that constitute the water permeable steel wall 15b extending in the extending direction of the steel sheet pile wall 15a. Since the lower end portion of the steel sheet pile 16 located at does not reach the structure 25, the steel member 15c or the water permeable steel wall 15b installed inside the bank 10 interferes with the structure 25 and the structure concerned. It is possible to prevent the object 25 from being damaged.

(Second embodiment)
FIG. 7 is a transverse cross-sectional view showing a structure for suppressing permeation failure of a dam body according to the second embodiment.
The difference of the second embodiment from the above-described first embodiment is the configuration of the protection unit 20 that protects the upstream slope 10b above the full water position 12 or its vicinity, and therefore this point will be described below. In the description, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof may be omitted.

In the present embodiment, the protection unit 20 includes the surface-type permeation prevention unit 24 made of an impermeable material, which is provided along the upstream slope 10b above or near the full water position, the steel wall 15a, and the surface type. The structure has a permeation preventive portion 24 and a filling type permeation preventive portion 21a which is filled with a water impermeable material.
Examples of the surface-type permeation preventive portion 24 include a concrete block installed on the upstream slope 10b, sprayed concrete applied on the upstream slope 10b, an impermeable sheet covering the upstream slope 10b, a geotextile, and the like. However, it is not limited to this.
Such a surface type permeation preventive portion 24 is constructed by driving the steel sheet pile wall 15 at the full water position 12 of the upstream slope 10b, and then covering the upstream slope 10b above the full water position 12 with steel. You may construct before the placement of the sheet pile wall 15. If there is an existing surface protection member such as a concrete block on the upstream slope 10b, the existing material may be utilized by removing only the surface protection member at the portion where the steel sheet pile is to be placed. Further, the upper end of the surface type permeation preventive portion 24 is substantially at the same position as the top end 10 a of the bank 10.
Further, the support member 18 that supports the steel sheet pile wall 15a may be the water permeable steel sheet pile wall 15b or a plurality of steel members 15c, as in the first embodiment.

Further, the filling-type permeation preventive portion 21a is formed by filling a gap between the steel wall 15a and the surface-type permeation preventing portion 24 with a water impermeable material such as metallurgical soil, soil cement or bentonite. .. Such a filling type penetration preventing portion 21a is formed in a right-angled triangular cross section, and is in close contact with the surface of the steel sheet pile wall 15a facing the bank 10 side and the surface of the surface penetration preventing portion 24.
Furthermore, the upper end of the steel sheet pile wall 15a, the upper surface of the filling type permeation prevention portion 21a, the upper end of the surface type permeation prevention portion 24, and the top end 10a of the bank 10 are at substantially the same height position. The upper end, the upper surface of the filling-type permeation preventive portion 21a, the upper end of the surface-type permeation prevention portion 24, and the top end 10a of the bank 10 are integrally paved to form a paving portion 22.

According to the present embodiment, the protection unit 20 that protects the upstream slope 10b above the full water position 12 or its vicinity is provided along the upstream slope 10b above the full water position 12 or its vicinity. Since it has the permeation preventive part 24 and the filling type permeation preventive part 21a filled between the steel wall 15a and the surface type permeation preventive part 24, at the upstream slope 10b which is the starting point of the permeation failure, the It is possible to prevent the permeation more surely and prevent the dam body 10 from permeating and breaking.
Further, since the surface type permeation preventive portion 24 is provided along the upstream slope 10b, the construction cost and the construction period can be shortened as compared with the conventional construction method in which the ground material of the bank 10 is replaced or improved.
Furthermore, it is possible to prevent the surface type permeation preventive portion 24 from being peeled off or damaged from the upstream slope 10b, and even if the surface type permeation preventive portion 24 is peeled off from the upstream slope 10b, the steel sheet pile wall 15a blocks the dam. Therefore, it is possible to prevent it from falling into the reservoir 11 and being submerged in water.

10 Embankment 10a Top 10b Upstream slope 11 Reservoir 12 Full water position 15a Steel sheet pile wall (steel wall)
15b Water permeable steel sheet pile wall (water permeable steel wall)
15c Steel member 18 Supporting part 20 Protecting part 21 Filling type penetration preventing part 21a Filling type penetration preventing part 22 Pavement part 24 Surface type penetration preventing part 25 Structure

Claims (5)

A structure for suppressing the osmotic failure of a levee body that suppresses the osmotic failure of the levee body provided on at least part of the outer periphery of the reservoir.
Assuming that the reservoir side is the upstream side of the bank body, the steel wall is on the upstream slope of the upstream side of the bank body and at or near the full water position of a height equal to the full water level of the reservoir. Is installed along the extending direction of the levee body and so as to project upward,
A protection unit for protecting the upstream slope above the full water position or its vicinity is provided,
The dam body permeation failure suppression structure, wherein the protection part is a filling type permeation preventive part made of an impermeable material filled between the steel wall and the upstream slope. A structure for suppressing the osmotic failure of a levee body that suppresses the osmotic failure of the levee body provided on at least part of the outer periphery of the reservoir.
Assuming that the reservoir side is the upstream side of the bank body, the steel wall is on the upstream slope of the upstream side of the bank body and at or near the full water position of a height equal to the full water level of the reservoir. Is installed along the extending direction of the levee body and so as to project upward,
A protection unit for protecting the upstream slope above the full water position or its vicinity is provided,
The protection part includes a surface type permeation preventive part made of a water impermeable material provided along the upstream slope above the full water position or its vicinity, and the steel wall and the surface type permeation preventive part. And a filling-type permeation-preventing portion made of a water-impermeable material filled in between. 3. The structure for preventing erosion damage to a dam body according to claim 1 or 2, wherein an upper end of the steel wall, an upper surface of the filling type permeation preventive portion, and a top end of the dam body are integrally paved. .. The lower end of the steel plate wall is located below the full water position, and is supported by a support member installed below the lower end of the steel wall,
The support member is a plurality of steel members provided at predetermined intervals in the extending direction of the steel wall, or a water-permeable steel wall extending in the extending direction of the steel wall, The structure for suppressing permeation failure of a levee body according to any one of claims 1 to 3. A structure extending in the width direction of the levee is provided inside the levee,
When the support member is a plurality of steel members provided at predetermined intervals in the extending direction of the steel sheet pile wall, the steel member is installed in a position to avoid the structure,
When the support member is a water-permeable steel wall extending in the extending direction of the steel wall, it is located above the structure among a plurality of steel sheet piles that compose the water-permeable steel wall. The reinforced structure for a dam body according to claim 4, wherein the lower end portion of the steel sheet pile does not reach the structure.

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