Reinforcement method of existing levee and levee

Abstract

To achieve increase of maximum water-holding capacity in a levee and reinforcement of a levee body, without requiring large-scale construction or site acquisition.SOLUTION: A reinforcement method of an existing levee is provided which includes steps of: placing a wall body extending in the extension direction of an existing levee to a levee body; and excavating a slope face of the levee body or the slope face and part of a top end of the levee body on the water-area side of the wall body. Also, the reinforcement method of an existing levee is provided which includes steps of: placing a wall body which extends in the extension direction of the existing levee and in which an upper end height is higher than the top end height of the levee body at the levee body; and constructing additional banking at least on top of one of the top end and the slope face of the levee body in an area along the wall body on the opposite side from the water area of the wall body.SELECTED DRAWING: Figure 1C

Description

[Technical Field]

[0001] The present invention relates to a method for reinforcing an existing embankment and to an embankment. [Background technology]

[0002] In recent years, heavy rain disasters have become frequent, raising concerns about flooding caused by overflowing water and breaches or collapses of river levees due to scouring of the levee body. As a countermeasure against such disasters, for example, Patent Document 1 proposes a technique for excavating the bottom of a river, lake, or coastline and reusing the excavated soil as embankment materials. This technique increases the maximum water retention capacity within the levee while also reinforcing the levee body itself. Another known method for river levees is called "retraction leveeing," which involves constructing a new levee on the inward side of the river than the existing levee and then removing the old one, thereby expanding the river channel cross-sectional area within the levee. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-9481 Summary of the Invention [Problem to be solved by the invention]

[0004] However, excavating and deepening the waterbed, as with the technology described in Patent Document 1, requires large-scale dredging work, and in the case of rivers, there is a possibility that sediment will be deposited on the bottom again. In the case of a levee, dredging work is not necessary and the cross-sectional area of ​​the river channel is certainly expanded, but if the river behind the levee is in an urban area, land acquisition is difficult and the impact on the surrounding environment is significant.

[0005] Therefore, the present invention aims to provide a method for reinforcing an existing levee and a levee that can increase the maximum water retention capacity within the levee and strengthen the levee body without the need for large-scale construction or land acquisition. [Means for solving the problem]

[0006] [1] A method for reinforcing an existing levee, comprising the steps of: casting a wall extending in the extension direction of the existing levee into the levee; and excavating the slope of the levee or a portion of the slope and top of the levee on the water side of the wall. [2] A method for reinforcing an existing levee described in [1], further comprising the step of constructing additional embankment on at least one of the top or slope of the levee body on the side opposite the water body of the wall body. [3] A method for reinforcing an existing levee, comprising the steps of: casting a wall into the levee, the wall extending in the extension direction of the existing levee and having an upper end height higher than the top height of the levee; and constructing additional embankment on at least one of the top end or slope of the levee in an area along the wall on the opposite side of the water body from the wall. [4] A method for reinforcing an existing levee described in [2] or [3], further comprising the step of casting an additional wall on the opposite side of the wall from the water body, and the additional embankment being constructed between the wall and the additional wall. [5] A method for reinforcing an existing levee described in [4], further comprising a step of connecting the heads of the wall body and the additional wall body with a connecting material. [6] The method for reinforcing an existing levee described in [4], further comprising the step of applying ground reinforcement to the additional embankment or the step of improving the ground of the additional embankment. [7] A method for reinforcing an existing levee described in [4], wherein at least one of the wall body and the additional wall body is a steel sheet pile wall or a steel pipe sheet pile wall. [8] A method for reinforcing an existing levee described in any one of [1] to [3], wherein the wall is a steel sheet pile wall or a steel pipe sheet pile wall. [9] In a levee in which a wall extending in the extension direction of an existing levee is cast into the levee body, a step of casting an additional wall on the side opposite to the water area with respect to the wall body, and a step of constructing additional embankment on at least one of the top end or slope of the levee body between the wall body and the additional wall body. Methods for reinforcing existing embankments, including:

[10] A method for reinforcing an existing embankment described in [9], wherein the wall and the additional wall are steel sheet pile walls or steel pipe sheet pile walls.

[11] A levee comprising a levee body and a wall extending in the extension direction of the levee and forming the side of the levee body facing the water body, the levee body comprising a first portion constructed to a predetermined height from the ground surface and a second portion constructed above the first portion, and both the first portion and the second portion being in contact with the wall body.

[12] The embankment described in

[11] , including an additional wall cast on the opposite side of the wall from the water body.

[13] The embankment described in

[12] , wherein the heads of the wall and the additional wall are connected to each other by a connecting member.

[14] A levee comprising a levee body, a first wall extending in the extension direction of the levee and forming the side of the levee body facing the water body, and a second wall cast on the opposite side of the first wall from the water body, wherein the levee body comprises a first part constructed to a predetermined height from the ground surface and a second part constructed above the first part, wherein of the first and second parts, only the first part is in contact with the first wall, and the tops of the first and second walls are connected to each other by a connecting material.

[15] A levee comprising a levee body, a first wall body cast into the levee body and extending in the extension direction of the levee, and a second wall body cast on the opposite side of the first wall body from the water body, wherein the heads of the first wall body and the second wall body are connected by a connecting material, and in the area between the first wall body and the second wall body and adjacent to the water body side of the second wall body, a ground reinforcement material is installed in a part of the levee body or a part of the levee body is improved in soil.

[16] A levee described in any one of

[11] to

[15] , wherein the upper surface of the levee body is paved. [Brief explanation of the drawings]

[0007] [Figure 1A] 1A to 1C are diagrams showing a method for reinforcing a river levee according to a first embodiment of the present invention. [Figure 1B] 1A to 1C are diagrams showing a method for reinforcing a river levee according to a first embodiment of the present invention. [Figure 1C] 1A to 1C are diagrams showing a method for reinforcing a river levee according to a first embodiment of the present invention. [Figure 2]FIG. 2 is a diagram for schematically explaining the effect of increasing the river channel cross-sectional area in the example shown in FIG. 1. [Figure 3] FIG. 2 is a diagram showing the example of FIG. 1 in which a portion higher than the bank body is formed by a separate member. [Figure 4] FIG. 10 is a diagram showing a method for reinforcing a river levee according to a second embodiment of the present invention. [Figure 5] 10A and 10B are diagrams showing a method for reinforcing a river levee according to a third embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing a case where tie members are installed as connecting members in the example of FIG. 5. [Figure 7] FIG. 10 is a diagram showing a modified example of the third embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example in which ground reinforcement material is installed on the additional embankment in the example of FIG. 7. [Figure 9] FIG. 10 is a diagram illustrating an example of calculation in effect verification of an embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating an example of calculation in effect verification of an embodiment of the present invention. [Figure 11] FIG. 10 is a diagram illustrating an example of calculation in effect verification of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0009] 1A to 1C are diagrams illustrating a method for reinforcing a river levee according to a first embodiment of the present invention. As shown in FIG. 1A, levee 1 is an existing levee and includes levee body 2, which has a river-side slope 21, a crest 22, and a river-side slope 23. As shown in FIG. 1B, a steel sheet pile wall 31 is installed in levee body 2. The steel sheet pile wall 31 is an example of a wall installed in levee body 2 and extending in the direction of the levee. In the illustrated example, the top height h2 of the steel sheet pile wall 31 is higher than the crest height h1 of levee body 2. However, as described below, the heights h1 and h2 may be approximately the same. Note that the heights h1 and h2 may be measured relative to one another, and the reference point is not particularly limited. For example, the ground level (GL) on the riverside of the design drawing may be used as the ground level, and the heights h1 and h2 may be measured based on this ground level.

[0010] After constructing the steel sheet pile wall 31 as described above, the slope 21 of the levee body 2 is excavated, for example, down to ground level, on the riverside of the steel sheet pile wall 31, as shown in Figure 1C. This allows the steel sheet pile wall 31 to form the riverside side of the levee body 2. If the steel sheet pile wall 31 is installed with sufficient penetration depth, the levee body 2 remains structurally stable even after the riverside slope 21 of the steel sheet pile wall 31 is excavated. By excavating the slope 21 in this manner, the river channel cross-sectional area—that is, the maximum water retention capacity of the river levee—can be increased. For example, as shown in Figure 1C, when the river water level rises to the design high water level (HWL), the cross-sectional area of ​​the waterway that allows water to flow down the excavated section 24 below the design high water level (HWL) is expanded. This increases the maximum flow rate of water that can flow down the levee 1 without overflowing during floods. The slope 21 on the river side of the steel sheet pile wall 31 does not necessarily have to be excavated down to the ground surface, but may be excavated shallower or deeper. Therefore, the position of the ground surface on the river side does not need to be specified in order to determine the extent to which the slope 21 should be excavated. Depending on the shape of the existing river levee and the cross-sectional area of ​​the river channel to be secured, the slope 21 and the ground following it may be excavated down to the riverbed or close to the riverbed.

[0011] Figure 2 is a diagram for schematically explaining the effect of increasing the river channel cross-sectional area in the example shown in Figure 1. For example, let L1 be the cross-sectional area of ​​the excavated portion on the left bank of the river (excavated portion 24 shown in Figure 1C), L2 be the cross-sectional area of ​​the excavated portion on the right bank of the river, H be the difference in height between the cut-off wall 2 and the steel sheet pile wall 31 (for simplicity, assumed to be the same on both banks), and B be the distance between the steel sheet pile walls 31 on both banks. The increased river channel cross-sectional area A1 relative to the previous river channel cross-sectional area A0 can be expressed by the following equation (1). The upper end height h2 of the steel sheet pile wall 31 may be the same as the crest height h1 of the cut-off wall 2. In this case, H = 0, and only the cross-sectional area L1 + L2 of the excavated portion is considered as the increase in the river channel cross-sectional area. A1 = A0 + L1 + L2 + B × H (1)

[0012] Note that H=0 also occurs when the upper end height h2 of the steel sheet pile wall 31 is lower than the crest height h1 of the levee body 2. However, even in this case, the crest 22 of the levee body 2 gradually erodes after overflow occurs, and the actual crest height decreases. In such a case, if the steel sheet pile wall 31 were not present, erosion would continue, further lowering the crest height and causing the river channel cross-sectional area to continue decreasing. On the other hand, if the steel sheet pile wall 31 is cast, the crest height will not fall below the upper end height h2 of the steel sheet pile wall 31, and the river channel cross-sectional area can be maintained.

[0013] The position at which the cut-off wall 2 should be excavated and the degree to which the upper end height h2 of the cut-off wall 31 should be raised relative to the crest height h1 of the cut-off wall 2 to ensure H = h2 - h1 in Equation (1) can be determined, for example, by substituting the required river channel cross-sectional area A1 or the increase in the river channel cross-sectional area A1 - A0 into Equation (1). The sheet pile wall 31 may be constructed at the slope of the cut-off wall 2, i.e., near the boundary between the slope 21 and the crest 22, as in the example shown in Figure 1C, or it may be constructed midway along the crest 22 of the cut-off wall 2, as in the example shown in Figure 2. In this case, parts of the slope 21 and the crest 22 are excavated on the riverside of the sheet pile wall 31. Alternatively, the sheet pile wall 31 may be constructed midway along the slope 21. In this case, only part of the slope 21 is excavated on the riverside of the sheet pile wall 31.

[0014] According to the first embodiment of the present invention, the river channel cross-sectional area is increased by excavating part of the levee body 2 on the river-front side of the steel sheet pile wall 31, so dredging of the riverbed is not required. Also, no construction is required on the river-reverse side of the levee 1. Therefore, in the above embodiment, the maximum water retention capacity within the levee can be increased without the need for large-scale construction or land acquisition, and while minimizing the impact on the surrounding environment on the river-reverse side.

[0015] FIG. 3 illustrates the example of FIG. 1 in which the portion higher than the embankment body is formed by a separate member. In the illustrated example, the upper end of the steel sheet pile wall 31 is lower than the crest height of the embankment body 2, but the upper end of a concrete block 41 attached to the top of the steel sheet pile wall 31 is higher than the crest 22 of the embankment body 2, thereby raising the embankment 1. In this case, the steel sheet pile wall 31 and the concrete block 41 constitute a wall cast into the embankment body 2 and whose upper end is higher than the crest height of the embankment body 2. The wall may also be composed of two or more members. The shape of the concrete block 41 is not particularly limited. For example, if the concrete block 41 has an L-shaped cross section as in the illustrated example, the upper end of the wall will be located at a position different from the position where the steel sheet pile wall 31 is cast into the embankment body 2. The concrete block 41 may be installed at the top of the steel sheet pile wall 31 as cap concrete, for example. Furthermore, instead of the concrete blocks 41, a concrete wall, a steel wall, or a block or wall of a composite structure of steel and concrete may be provided at the head of the steel sheet pile wall 31 to form a wall together with the steel sheet pile wall 31. The above-described configuration can also be applied to other embodiments described below.

[0016] FIG. 4 illustrates a river levee reinforcement method according to a second embodiment of the present invention. In the illustrated example, after the cut-off wall 2 is excavated on the riverfront side of the steel sheet pile wall 31 as described above in the first embodiment, an additional embankment 25 is constructed on the crest 22 of the cut-off wall 2 in an area along the steel sheet pile wall 31 on the riverfront side of the cut-off wall 2. By excavating the cut-off wall 2, the steel sheet pile wall 31 forms the riverfront side of the cut-off wall 2. Note that the additional embankment 25 does not need to be constructed after the excavation of the cut-off wall 2 is completed; it may be constructed in parallel with the excavation of the cut-off wall 2. The additional embankment 25 may be constructed at least in part using the soil and sand generated by the excavation of the cut-off wall 2. In this case, the additional embankment 25 may be constructed solely with the soil and sand generated by the excavation of the cut-off wall 2, or it may be constructed using a combination of the soil and sand generated by the excavation of the cut-off wall 2 and soil brought from another location. The soil generated by the excavation of the cut-off wall 2 may be used to construct the additional embankment 25 after a soil conditioning process. The soil conditioning process may be performed at a location away from the levee 1. Alternatively, the additional embankment 25 may be constructed solely with soil brought from another location, without using the soil generated by the excavation of the cut-off wall 2. While the upper end height h2 of the steel sheet pile wall 31 may be the same as the crest height h1 of the cut-off wall 2 in the first embodiment, in this embodiment, the upper end height h2 of the steel sheet pile wall 31 is higher than the crest height h1 of the cut-off wall 2. In the illustrated example, the additional embankment 25 is constructed on the crest 22 with a thickness corresponding to this height difference. In this case, after construction is completed, the original cut-off wall 2, constructed to a predetermined height from the ground surface, constitutes the first part of the cut-off wall, and the additional embankment 25 constructed above the cut-off wall 2 constitutes the second part of the cut-off wall. Both the cut-off wall 2 and the additional embankment 25 are in contact with the steel sheet pile wall 31.

[0017] According to the second embodiment of the present invention, the additional embankment 25 is constructed in the area along the steel sheet pile wall 31 on the backside of the river. This allows the additional embankment 25 to be constructed more stably than simply adding an embankment on the crest 22. Furthermore, since the additional embankment 25 is constructed adjacent to the steel sheet pile wall 31, the additional embankment 25 is less likely to be washed away even in the event of overflow, thereby more reliably achieving the effect of raising the embankment 1. Paving the top surface of the embankment body, including the additional embankment 25, further reduces the likelihood of the additional embankment 25 being washed away. These effects can also be achieved when constructing the additional embankment 25 using newly delivered soil and sand. Therefore, this embodiment may be implemented without excavating the embankment body 2 as in the first embodiment. In this case, the slope 21 may remain in the excavated portion 24 shown in FIG. 4. The configuration of paving the top surface of the embankment body can also be adopted in other embodiments, such as the examples described below with reference to FIGS. 5 to 8. 4, by constructing the additional embankment 25 using at least part of the soil generated by the excavation of the cut-off wall 2, the amount of soil disposal required for the excavation can be reduced or eliminated, and the amount of embankment material can also be reduced or eliminated. Note that the additional embankment does not necessarily have to be constructed on the crest 22 of the area along the steel sheet pile wall 31. For example, it may be constructed on the crest 22 away from the steel sheet pile wall 31 or on the slope 23 on the back side of the river. The height of the top surface of the additional embankment 25 is not particularly limited; it may be approximately the same as the top of the steel sheet pile wall 31, as in the illustrated example, or the top surface of the additional embankment 25 may be located at a lower or higher position.

[0018] FIG. 5 is a diagram illustrating a river levee reinforcement method according to a third embodiment of the present invention. In the illustrated example, as in the second embodiment, an additional embankment 25 is constructed by casting a steel sheet pile wall 32 as an additional wall on the riverside of the steel sheet pile wall 31, and then constructing the additional embankment 25 on the crest 22 and slope 23 of the embankment between the steel sheet pile wall 31 and the steel sheet pile wall 32. As in the second embodiment, the additional embankment 25 may be constructed using newly delivered soil and sand, or the slope 21 may remain in the excavated portion 24. The steel sheet pile wall 32 may be cast, for example, before the steel sheet pile wall 31, parallel to the steel sheet pile wall 31, or after the steel sheet pile wall 31. Alternatively, after the additional embankment 25 is constructed on the crest 22 as in the second embodiment, the steel sheet pile wall 32 may be cast and the additional embankment 25 may also be constructed on the slope 23. The upper end height of the steel sheet pile wall 32 may be higher than the crest height of the cut-off wall 2, for example, and may be approximately the same as or higher than the upper end height of the steel sheet pile wall 31. Alternatively, the upper end height of the steel sheet pile wall 32 may be lower than the crest height of the cut-off wall 2. In this case, the additional embankment 25 may be constructed so as to form a new slope along the slope 23. Note that the additional embankment 25 does not necessarily have to be constructed only between the steel sheet pile walls 31, 32, but may also be constructed outside the steel sheet pile walls 31, 32. Furthermore, the additional embankment 25 does not necessarily have to be constructed over the entire space between the steel sheet pile walls 31, 32, but may be constructed only on the entire or part of the crest 22 or the slope 23. Furthermore, for example, when the cut-off wall 2 is an existing levee, the steel sheet pile wall 32 may be cast within the slope 23 or the crest 22 of the cut-off wall 2.

[0019] According to the third embodiment of the present invention, the additional embankment 25 can be easily and stably constructed between the steel sheet pile walls 31 and 32. Furthermore, if the steel sheet pile wall 32 is cast with a sufficient embedment depth, the embankment body 2 and the additional embankment 25 are supported by the steel sheet pile wall 31 on the riverside as well as the steel sheet pile wall 32 on the riverside, thereby increasing the strength of the embankment 1. Furthermore, if the flat area on the embankment 1 is increased by constructing the additional embankment 25 on the slope 23, the usable area for roads and other purposes can be increased. These effects can also be achieved when constructing the additional embankment 25 using newly delivered soil and sand. Therefore, like the second embodiment, this embodiment may be implemented without excavating the embankment body 2 as in the first embodiment. Constructing the additional embankment 25 using at least part of the soil and sand generated by the excavation of the embankment body 2 reduces or eliminates the need for disposal of the soil and sand generated by the excavation, and also reduces or eliminates the need for embankment material.

[0020] FIG. 6 illustrates the example of FIG. 5 with tie rods installed as connecting members. In the illustrated example, the steel sheet pile walls 31, 32 are connected to each other near their heads using tie rods 33. The tie rods 33 are an example of a connecting member that transmits tensile and shear forces between the steel sheet pile walls 31, 32. Alternatively, the connecting members may be concrete top plates installed across the heads of the steel sheet pile walls or steel walls installed perpendicular to the steel sheet pile walls. Installing connecting members such as tie rods 33 transfers loads between the steel sheet pile walls 31, 32. Therefore, in the event of scouring due to overflow, for example, one of the more stable walls supports the other, making it easier to maintain the structure of the levee 1. While tie rods 33 are installed in the examples described below with reference to FIGS. 7 and 8, tie rods 33 may not be installed if, for example, the steel sheet pile walls 31, 32 are installed with sufficient embedded depth. The connecting member may be any member capable of connecting the steel sheet pile walls 31, 32, such as a tie rope.

[0021] Figure 7 is a diagram showing a modified example of the third embodiment of the present invention. In the illustrated example, an additional embankment 25 is constructed between the steel sheet pile walls 31, 32, as in the example of Figure 6 above. However, the height of the tops of the steel sheet pile walls 31, 32 is approximately the same as the height of the crest of the cut-off wall 2, and the additional embankment 25 is constructed on the riverside slope 23 rather than on the crest 22. As such, in some embodiments of the present invention, the additional embankment 25 does not necessarily have to be constructed on the crest 22. In these cases, if the original cut-off wall 2 constructed to a predetermined height from the ground surface is defined as the first part of the cut-off wall, and the additional embankment 25 constructed above the cut-off wall 2 is defined as the second part of the cut-off wall, only the first part of the cut-off wall 2 contacts the steel sheet pile wall 31 on the riverside.

[0022] Figure 8 shows an example in which ground reinforcement is applied to the additional embankment in the example shown in Figure 7 . In the illustrated example, ground reinforcement 26 is applied to the additional embankment 25 built on the slope 23 of the embankment body 2. The ground reinforcement 26 is, for example, a mesh-like, plate-like, or strip-like material made of resin or metal, including a material called a geogrid. In addition to or instead of applying the ground reinforcement 26, the additional embankment 25 may be improved by injecting slag or chemicals. This allows the application of ground reinforcement 26 to a portion of the embankment body consisting of the original embankment body 2 and the additional embankment 25, or improves the ground in the area between the steel sheet pile walls 31 and 32 and adjacent to the steel sheet pile wall 32 on the riverfront side. In this area, shear planes may be generated due to scouring caused by overflow or loads acting during earthquakes, which could weaken the embankment body. However, applying the ground reinforcement 26 or improving the ground in this area can more effectively improve the embankment strength.

[0023] While the above describes an embodiment of the present invention relating to a river levee, the present invention can also be applied to, for example, a coastal levee. In the levee according to the present invention, the "water side" and the "opposite side of the water" are specified, but in the river levee embodiment, the "river side" is the "water side" and the "river side" is the "opposite side of the water." In the case of a coastal levee, the "sea side" is the "water side" and the "land side" is the "opposite side of the water." Furthermore, while the wall and additional wall have been described as steel sheet pile walls 31 and 32, the wall and additional wall may be steel pipe sheet pile walls, concrete walls, or the like. Furthermore, the wall and additional wall may be different types of walls, such as a combination of steel pipe and sheet piles or steel and concrete.

[0024] The effectiveness of the levee according to the embodiment of the present invention as described above was verified by modeling the location where an overflow breach occurred in an actual river levee and calculating the results if the river channel cross-sectional area had been expanded. This river levee was breached by an overflow of 0.28 m depth during a typhoon. As shown in Figure 9, the distance between the crowns of the levee on both banks before the breach (river channel width) was 300 m, and the cross-sectional area of ​​the river channel enclosed by the levee slope and riverbed was 1250 m. 2 When considered per unit length, the amount obtained by multiplying the river channel width of 300m by the overflow depth of 0.28m (21.25m 2 If the water in the river had been contained within the cross-sectional area of ​​the river channel, it is believed that overflow breach could have been prevented. The shape of the levees on both banks is assumed to be the same, with the levee head height of 2.66m, the head width of 4.0m, and the width of the slope (horizontal direction) of 6.15m on the river side and 5.03m on the river side.

[0025] First, consider the case where the cross-sectional area of ​​the river channel is expanded solely by excavating the embankment body on the riverfront side of the steel sheet pile wall, as in the example shown in Figure 10. If the steel sheet pile wall is installed 1 m from the top of the slope on the riverfront side and the embankment body on the riverfront side of the steel sheet pile wall is excavated down to the ground surface, the cross-sectional area of ​​the excavated part of one side of the embankment will be 6.15 x 2.66 x 0.5 + 1 x 2.66 = 10.84 m 2 If the same excavation is carried out on both banks, the increase in the cross-sectional area of ​​the river channel will be 10.84 x 2 = 21.68 m2 This amount is the amount of overflow water mentioned above (21.25 m 2 ), so if such excavation is carried out, the increase in the cross-sectional area of ​​the river channel will increase the maximum flow rate of water that can be released, and it is highly likely that overflow will be prevented. Note that the cross-sectional area of ​​the excavated portion in the above calculation formula includes the cross-sectional area of ​​the gaps between the sediment particles that were present within the original levee body, as well as the cross-sectional area of ​​culverts, etc. Although these areas are gaps, water does not flow through them at the same velocity as the river channel, and excavation can be treated as an increase in the cross-sectional area of ​​the river channel. On the other hand, if the levee body is composed of ground materials with large gaps, such as rock and gravel, water may flow through the gaps at the same velocity as the river channel. In such cases, the gaps within the levee body can be treated as if they were included in the original cross-sectional area of ​​the river channel, and the cross-sectional area of ​​the gaps that were present within the excavated levee body can be deducted from the increase in the cross-sectional area of ​​the river channel.

[0026] Next, consider the case where, in addition to excavation, the height of the top of the steel sheet pile wall is made higher than the height of the top of the embankment body, as in the example shown in Figure 11. If the steel sheet pile wall is installed on the slope on the riverside and the embankment body on the riverside of the steel sheet pile wall is excavated down to the ground surface, the cross-sectional area of ​​the excavated part of one side of the embankment will be 6.15 x 2.66 x 0.5 = 8.18 m 2 If the same excavation is carried out on both banks, the increase in the river channel cross-sectional area will be 8.18 x 2 = 16.36 m 2 Furthermore, if the height of the top of the steel sheet pile wall is made 0.1 m higher than the crown height, this is multiplied by the width of the river channel, 300 m, to get 300 x 0.1 = 30 m. 2 The total increase in the river cross-sectional area is 16.36 + 30 = 46.36 m 2 The amount of overflow water mentioned above (21.25 m 2 ), it is highly likely that overflow can be prevented by this type of construction. In the above example, the river channel is wide, so the effect of raising the riverbed is more pronounced than that of excavating the levee, but if the river channel is narrower, for example, increasing the river channel cross-sectional area by excavating the levee can be more effective. [Explanation of symbols]

[0027] 1...embankment, 2...embankment body, 21...slope, 22...top, 23...slope, 24...excavation section, 25...embankment, 26...ground reinforcement material, 31...steel sheet pile wall, 32...steel sheet pile wall, 33...tie material.

Claims

1. a step of casting a wall body extending in the extension direction of the existing levee into the levee body; a step of excavating a part of the slope of the bank body or the slope and the top of the bank body on the water area side of the wall body; Methods for reinforcing existing embankments, including:

2. 2. The method for reinforcing an existing levee according to claim 1, further comprising the step of constructing additional embankment on at least one of the top and slope of the levee body on the side of the wall opposite the water body.

3. a step of casting a wall body onto the embankment body, the wall body extending in the extension direction of the existing embankment and having an upper end height higher than the top end height of the embankment body; constructing an additional embankment on at least one of the top and slope of the embankment in an area along the wall opposite the water body; Methods for reinforcing existing embankments, including:

4. Further comprising the step of constructing an additional wall on the opposite side of the wall from the water body; 4. The method for reinforcing an existing levee according to claim 2 or claim 3, wherein the additional embankment is constructed between the wall and the additional wall.

5. 5. The method for reinforcing an existing levee according to claim 4, further comprising the step of connecting the heads of the wall body and the additional wall body with a connecting material.

6. The method for reinforcing an existing levee according to claim 4, further comprising the step of applying a ground reinforcement material to the additional embankment or the step of improving the ground of the additional embankment.

7. 5. The method for reinforcing an existing embankment according to claim 4, wherein at least one of the wall body and the additional wall body is a steel sheet pile wall or a steel pipe sheet pile wall.

8. The method for reinforcing an existing levee according to any one of claims 1 to 3, wherein the wall is a steel sheet pile wall or a steel pipe sheet pile wall.

9. a step of constructing an additional wall on the side of the existing wall extending in the extension direction of the existing levee opposite to the water area; constructing an additional embankment on at least one of the top and slope of the bank body between the wall body and the additional wall; Methods for reinforcing existing embankments, including:

10. The method for reinforcing an existing embankment according to claim 9, wherein the wall and the additional wall are steel sheet pile walls or steel pipe sheet pile walls.

11. The embankment and a wall extending in the extension direction of the levee and forming the side of the levee body facing the water area; Including, The embankment includes a first portion constructed to a predetermined height from the ground surface and a second portion constructed above the first portion, and both the first portion and the second portion are in contact with the wall.

12. 12. The embankment of claim 11, including an additional wall cast on the opposite side of the wall from the body of water.

13. The embankment according to claim 12, wherein the heads of the wall and the additional wall are connected to each other by a connector.

14. The embankment and a first wall extending in the extension direction of the bank and forming a side surface of the bank body facing the water area; A second wall body is installed on the opposite side of the water area from the first wall body. Including, the bank includes a first portion constructed to a predetermined height from the ground surface and a second portion constructed above the first portion, of the first portion and the second portion, only the first portion is in contact with the first wall; A levee, wherein the heads of the first wall and the second wall are connected to each other by a connecting member.

15. The embankment and a first wall body that is cast into the bank body and extends in the extension direction of the bank; A second wall body is installed on the opposite side of the water area from the first wall body. Including, the heads of the first wall body and the second wall body are connected to each other by a connecting material, A levee in which ground reinforcement material is installed in a portion of the levee body or ground improvement work is performed in a region between the first wall body and the second wall body and adjacent to the water side of the second wall.

16. The embankment according to any one of claims 11 to 15, wherein the upper surface of the embankment body is paved.

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