Embankment reinforcement structure

Abstract

To realize rational structure for improving strength of an embankment at a swell of water in a reinforcement structure of an embankment by double steel sheet pile wall.SOLUTION: A reinforcement structure 10 of an embankment comprises: a first steel sheet pile wall 11 installed in a portion at a water area 2 side of a dam body 1; a second steel sheet pile wall 12 installed in a portion at an opposite side to the water area 2 of the dam body; and a connection member 13 connecting head portions of each of the first steel sheet pile wall 11 and the second steel sheet pile wall 12. When a length direction of the dam body is an x direction and a horizontal direction perpendicular to the x direction is a y direction, with respect to an average value per unit length in the x direction, a bending rigidity EI1 in the y direction of the first steel sheet pile wall and an embedded length L1 of the first steel sheet pile wall, and a bending rigidity EI2 in the y direction of the second steel sheet pile wall and an embedded length L2 of the second steel sheet pile wall satisfy a relation of a formula (i).SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There are concerns about the cracking and subsidence of embankments due to earthquakes, and the breaching and collapse of embankments due to erosion of the embankment caused by overtopping during floods. As a countermeasure against this, for example, Patent Document 1 describes a reinforcement structure for embankments in which steel sheet pile walls are cast into the slopes on both sides of the embankment in the width direction, extending in the continuous direction of the embankment, and the heads of each steel sheet pile wall are connected by tie rods. This type of reinforcement structure using double steel sheet pile walls is known to be effective as a countermeasure against liquefaction, because the two rows of steel sheet pile walls suppress the deformation and movement of soil during an earthquake.

[0003] On the other hand, Patent Document 2 describes a reinforcing structure for a levee in which the steel sheet pile wall on the water side of the double steel sheet pile wall is formed continuously, while the steel sheet pile wall on the opposite side of the water side is formed as a discrete bracing work, and the embedded length of the steel sheet pile wall on the water side reaches the bearing layer of the ground, while the bracing work on the opposite side of the water side is not embedded to the bearing layer. By forming the steel sheet pile wall on the water side continuously and with an embedded length that reaches the bearing layer, deformation and movement of the soil during an earthquake can be suppressed, while the opposite side of the water side is formed discretely and with a shorter embedded length, which can reduce the amount of steel material used and the labor required for driving the steel sheet piles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-13451 A [Patent Document 2] Patent No. 5578140 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, although research has progressed on the above-mentioned double steel sheet pile wall reinforcement structure for embankments as a measure against liquefaction during earthquakes, it cannot be said that a sufficient number of rational structures have been proposed to improve the strength of embankments in the event of overtopping or scouring caused by rising water levels. In the following explanation, "when the water level rises" refers to the case where overtopping and scouring may occur due to rising water levels.

[0006] Therefore, an object of the present invention is to realize a rational structure for improving the strength of a levee during times of flooding in a reinforcing structure of a levee using a double steel sheet pile wall. [Means for solving the problem]

[0007] [1] A reinforcing structure for a levee comprising a first steel sheet pile wall driven into the water body side of the levee body, a second steel sheet pile wall driven into the water body side of the levee body, and connecting members connecting the heads of the first steel sheet pile wall and the second steel sheet pile wall, wherein, when the longitudinal direction of the levee body is defined as the x direction and the horizontal direction perpendicular to the x direction is defined as the y direction, a bending stiffness EI1 of the first steel sheet pile wall in the y direction and an embedded length L1 of the first steel sheet pile wall, and a bending stiffness EI2 of the second steel sheet pile wall in the y direction and an embedded length L2 of the second steel sheet pile wall satisfy the relationship of formula (i) for average values ​​per unit length in the x direction. TIFF0007640852000001.tif1784[2] A reinforcement structure for a levee described in [1], wherein the bending rigidity EI1 of the first steel sheet pile wall and the bending rigidity EI2 of the second steel sheet pile wall satisfy the relationship of equation (ii). EI2>EI1 (ii) [3] A reinforcement structure for a levee described in [2], wherein the bending rigidity in the y direction of the steel sheet piles constituting the second steel sheet pile wall is higher than the bending rigidity in the y direction of the steel sheet piles constituting the first steel sheet pile wall. [4] A reinforcement structure for a levee described in [2] or [3], wherein the first steel sheet pile wall has steel sheet piles intermittently arranged at predetermined intervals in the x direction, and the second steel sheet pile wall has steel sheet piles arranged continuously. [5] A reinforcement structure for a levee described in any one of [1] to [4], wherein the embedded length L1 of the first steel sheet pile wall and the embedded length L2 of the second steel sheet pile wall satisfy the relationship of formula (iii). L2>L1 (iii) [6] A reinforcement structure for a levee described in [5], wherein the embedded length of some of the steel sheet piles constituting the second steel sheet pile wall is longer than the embedded length of the remaining steel sheet piles constituting the second steel sheet pile wall and the steel sheet piles constituting the first steel sheet pile wall, or the embedded length of some of the steel sheet piles constituting the first steel sheet pile wall is shorter than the embedded length of the remaining steel sheet piles constituting the first steel sheet pile wall and the steel sheet piles constituting the second steel sheet pile wall. [7] A reinforcement structure for a levee described in any one of [1] to [6], wherein the bending rigidity EI1 of the first steel sheet pile wall and the embedment length L1 of the first steel sheet pile wall, and the bending rigidity EI2 of the second steel sheet pile wall and the embedment length L2 of the second steel sheet pile wall satisfy the relationship of equation (iv). TIFF0007640852000002.tif1884 Effect of the Invention

[0008] According to the above configuration, a rational structure can be realized for improving the strength of the embankment during floods by increasing the bending rigidity or lengthening the embedded length of the second steel sheet pile wall, which is subjected to a larger moment when erosion and scouring occur on the slope on the opposite side of the embankment from the water area due to overflow during floods. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing a reinforcement structure for an embankment according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing an example of a structure of a steel sheet pile wall in the reinforcement structure shown in FIG. 1. [Diagram 3] FIG. 2 is a perspective view showing another example of the structure of a steel sheet pile wall in the reinforcement structure shown in FIG. 1. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a reinforcement structure for an embankment according to a second embodiment of the present invention. [Diagram 5] FIG. 5 is a perspective view showing an example of the structure of a steel sheet pile wall in the reinforcement structure shown in FIG. 4. [Figure 6] FIG. 5 is a perspective view showing another example of the structure of a steel sheet pile wall in the reinforcement structure shown in FIG. 4. [Figure 7] FIG. 5 is a perspective view showing still another example of the structure of a steel sheet pile wall in the reinforcement structure shown in FIG. [Figure 8] FIG. 1 is a diagram showing the state set in an analysis for verifying the effect of a reinforcement structure for a levee according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] FIG. 1 is a schematic cross-sectional view showing a reinforcing structure for a levee according to a first embodiment of the present invention. In this embodiment, the reinforcing structure for a levee 10 includes a first steel sheet pile wall 11 driven into a portion of the levee body 1 on the water area 2 side, a second steel sheet pile wall 12 driven into a portion of the levee body 1 opposite the water area 2, and a tie rod 13 which is a connecting member connecting the heads of the first steel sheet pile wall 11 and the second steel sheet pile wall 12. Here, the levee body 1 has a slope 1A on the water area side, a slope 1B on the opposite side to the water area, and a top surface 1C. The first steel sheet pile wall 11 is driven into the slope shoulder which is the boundary between the slope 1A on the water area side and the top surface 1C, or in the vicinity thereof, and the second steel sheet pile wall 12 is driven into the slope shoulder which is the boundary between the slope 1B on the opposite side to the water area and the top surface 1C, or in the vicinity thereof. The first steel sheet pile wall 11 and the second steel sheet pile wall 12 each extend in the longitudinal direction (x direction) of the bank body 1.

[0012] In this embodiment, the tie rod 13 is disposed as the connecting member, but the connecting member is not particularly limited as long as it is a member that can connect the first steel sheet pile wall 11 and the second steel sheet pile wall 12 and transmit tensile and shear forces. In other embodiments, the connecting member may be a concrete top plate installed across the heads of the steel sheet pile walls, or a wall body made of steel material installed perpendicular to the steel sheet pile walls.

[0013] In this embodiment, the bending rigidity EI2 of the second steel sheet pile wall 12 is larger than the bending rigidity EI1 of the first steel sheet pile wall 11 (EI2>EI1). Here, the bending rigidities EI1 and EI2 are bending rigidities in the horizontal direction (y direction) perpendicular to the longitudinal direction (x direction) of the bank body 1. The bending rigidities EI1 and EI2 are calculated as average values ​​per unit length in the longitudinal direction (x direction) of the bank body 1. That is, the bending rigidities EI1 and EI2 are calculated by multiplying the Young's moduli E1 and E2 of the material of the steel sheet piles constituting each steel sheet pile wall by the second moments of area I1 and I2 about the axis in the y direction within the range of the unit length in the x direction of each steel sheet pile wall.

[0014] Fig. 2 is a perspective view showing an example of the structure of a steel sheet pile wall in the reinforcement structure shown in Fig. 1. In the example shown in the figure, the bending rigidity of the steel sheet pile constituting the second steel sheet pile wall 12 is higher than that of the steel sheet pile constituting the first steel sheet pile wall 11. Here again, the bending rigidity is the bending rigidity in the horizontal direction (y direction) perpendicular to the longitudinal direction (x direction) of the embankment body 1. More specifically, for example, the steel sheet pile constituting the second steel sheet pile wall 12 has a larger moment of area about the axis in the y direction when forming a steel sheet pile wall than the steel sheet pile constituting the first steel sheet pile wall 11. As a result, for example, even if the first steel sheet pile wall 11 and the second steel sheet pile wall 12 are both formed continuously in the longitudinal direction (x direction) of the embankment body 1 and the embedded length L of the first steel sheet pile wall 11 and the second steel sheet pile wall 12 are substantially the same, the bending rigidity EI2 of the second steel sheet pile wall 12 is greater than the bending rigidity EI1 of the first steel sheet pile wall 11.

[0015] FIG. 3 is a perspective view showing another example of the structure of the steel sheet pile wall in the reinforcement structure shown in FIG. 1. In the illustrated example, in the first steel sheet pile wall 11, missing parts 11X are formed at a predetermined interval P in the longitudinal direction (x direction) of the bank body 1. That is, in the first steel sheet pile wall 11, the steel sheet piles are intermittently arranged at a predetermined interval P. The interval P does not necessarily have to be the same for all the missing parts 11X, and may be different, for example, three steel sheet piles in one place that are arranged between the missing parts 11X to form the first steel sheet pile wall 11, and four steel sheet piles in another place. On the other hand, in the second steel sheet pile wall 12, such missing parts are not formed, and the steel sheet piles are continuously arranged. As a result, if the unit length x1 is set to be equal to or greater than the interval P of the missing parts 11X formed in the first steel sheet pile wall 11 in the x direction, the second moment of area I1 of the first steel sheet pile wall 11 in the range of the unit length x1 is reduced by the amount of the missing parts 11X. As a result, for example, even if the first steel sheet pile wall 11 and the second steel sheet pile wall 12 are both constructed of steel sheet piles of the same material and cross-section, and the embedded lengths L of the first steel sheet pile wall 11 and the second steel sheet pile wall 12 are substantially the same, the bending rigidity EI2 of the second steel sheet pile wall 12 is greater than the bending rigidity EI1 of the first steel sheet pile wall 11.

[0016] FIG. 4 is a schematic cross-sectional view showing a reinforcement structure of a levee according to a second embodiment of the present invention. In this embodiment, the reinforcement structure of the levee includes a first steel sheet pile wall 11 driven into a portion of the levee body 1 on the water area 2 side, a second steel sheet pile wall 22 driven into a portion of the levee body 1 opposite to the water area 2, and a tie rod 23 which is a connecting member connecting the heads of the first steel sheet pile wall 21 and the second steel sheet pile wall 22. The first steel sheet pile wall 21 and the second steel sheet pile wall 22 each extend in the longitudinal direction (x direction) of the levee body 1. The embedded length L2 of the second steel sheet pile wall 22 is longer than the embedded length L1 of the first steel sheet pile wall 21 (L2>L1). Here, the embedded lengths L1 and L2 are calculated as average values ​​per unit length in the longitudinal direction (x direction) of the levee body 1.

[0017] 5 to 7 are perspective views showing examples of the structure of the steel sheet pile wall in the reinforcement structure shown in FIG. 4. In the example shown in FIG. 5, the embedded length L2 of the entire second steel sheet pile wall 22 is longer than the embedded length L1 of the entire first steel sheet pile wall 21. On the other hand, in the example shown in FIG. 6, the embedded length L2 of some steel sheet piles 221 constituting the second steel sheet pile wall 22 is longer than the embedded length L1 of the entire first steel sheet pile wall 21. 21 However, the remaining steel sheet piles 222 constituting the second steel sheet pile wall 22 and the steel sheet piles constituting the first steel sheet pile wall 21 are embedded length L 22 , L1 (in the example of Figure 6, L 22 7, the embedded length L of some of the steel sheet piles 211 constituting the first steel sheet pile wall 21 is longer than 11 However, the remaining steel sheet piles 212 constituting the first steel sheet pile wall 21 and the steel sheet piles constituting the second steel sheet pile wall 22 are embedded in the wall L 12 , L2 (in the example of Figure 7, L 12 In these cases, the embedded length L2 of the second steel sheet pile wall 22 is longer than the embedded length L1 of the first steel sheet pile wall 21 (L2>L1) in the average value per unit length in the longitudinal direction (x direction) of the embankment body 1.

[0018] The first and second embodiments of the present invention described above can be combined with each other. That is, the first steel sheet pile wall (bending rigidity EI1, embedded length L1) to be installed in the water area side of the embankment in the reinforcement structure of the embankment and the second steel sheet pile wall (bending rigidity EI2, embedded length L2) to be installed in the water area side of the embankment may be EI2>EI1 and L2>L1. In the first embodiment, EI2>EI1 and L2=L1, and in the second embodiment, EI2=EI1 and L2>L1. The conditions including these can be expressed by the following formula (1). Specifically, it is sufficient to select an appropriate magnitude relationship from the above options after securing sufficient bending rigidities EI1, EI2 and embedded lengths L1, L2 for each of the first steel sheet pile wall 11 and the second steel sheet pile wall 12 in terms of design.

[0019]

number

[0020] From the viewpoint of more effectively improving the strength of the embankment, it is more preferable that the condition of formula (2) is satisfied. The condition of formula (2) is satisfied, for example, when the bending stiffness EI2 is 10% or more greater than the bending stiffness EI2, or when the embedded length L2 is 10% or more greater than the embedded length L1. For example, hat-shaped steel sheet piles constituting the steel sheet pile wall are known to be 10H, 25H, 45H, and 50H types, in order of decreasing bending stiffness, and there is a difference in bending stiffness of at least 10% between each type. Therefore, when the second steel sheet pile wall is constructed of a type of steel sheet pile having a bending stiffness greater than that of the first steel sheet pile wall, the condition of formula (2) is satisfied when the bending stiffness EI2 is 10% or more greater than the bending stiffness EI2.

[0021]

number

[0022] The reasons why a levee reinforcement structure that meets the above conditions improves the strength of the levee during times of flooding are explained below.

[0023] When the river floods, water overflows from the water area side and flows over the levee to the opposite side. When overflow occurs, erosion and scouring progress on the slope 1B (see Fig. 1; the same below) of the levee body 1 on the opposite side of the water area 2, and the levee body 1 no longer has the effect of suppressing the deformation of the second steel sheet pile wall 12 on the opposite side of the water area 2. This causes different behaviors with respect to horizontal loads such as flood loads between the second steel sheet pile wall 12 on the opposite side of the water area 2 and the first steel sheet pile wall 11 on the water area 2 side. Specifically, the moment generated in the second steel sheet pile wall 12 is larger than that in the first steel sheet pile wall 11, and the range of influence of the moment is deeper in the second steel sheet pile wall 12 than in the first steel sheet pile wall 11. Even if erosion and scouring of the slope 1B occurs in the first steel sheet pile wall 11 due to overtopping, the deformation is still suppressed by the embankment 1 between the first steel sheet pile wall 11 and the second steel sheet pile wall 12, so the generated moment is small and the range of influence of the moment is also shallow. By transmitting the load applied to the second steel sheet pile wall 12 to such a first steel sheet pile wall 11 by the tie rod 13, part of the moment of the second steel sheet pile wall 12 can be borne by the first steel sheet pile wall 11.

[0024] When taking into account the behavior during flooding as described above, by applying the above conditions, it becomes possible to enable the second steel sheet pile wall 12 to withstand a larger moment, while for the first steel sheet pile wall 11, steel sheet piles with lower rigidity than the steel sheet piles that make up the second steel sheet pile wall 12 can be constructed with a wall extension or embedment depth sufficient to withstand a relatively smaller moment, making it possible to design a rational embankment reinforcement structure.

[0025] Conventionally, the reinforcement structure of embankments using double steel sheet pile walls has been studied mainly as a measure against liquefaction during earthquakes, and therefore the erosion and scouring of the slope on the opposite side of the water area when overtopping occurs has not been taken into consideration, and the first and second steel sheet pile walls have been designed to behave symmetrically against the flow force caused by liquefaction during earthquakes, or to behave the same against horizontal loads such as flood loads. In this case, it is not necessary to make the bending stiffness and embedded length of the first and second steel sheet pile walls different, and rather, as opposed to the above embodiment, the steel sheet pile wall on the opposite side of the water area is formed discretely or the embedded length is shortened, thereby reducing the amount of steel material used and the man-hours required for driving the steel sheet piles, as described above. Although such a conventional reinforcement structure of embankments using double steel sheet piles is also effective as a measure against liquefaction during earthquakes, the configuration according to the embodiment of the present invention described above is advantageous for a rational design that takes into account the strength of the embankment during flooding.

[0026] In the above-described embodiment, the second steel sheet pile on the opposite side of the water area is described as a continuous wall, but if it is possible to suppress the soil of the embankment during floods, etc., gaps between the steel sheet piles are permitted, and joints do not necessarily have to be fitted between the steel sheet piles. In addition, although the length of a river embankment is long, the reinforcement structure as in the above-described embodiment does not necessarily have to be formed over the entire length of the embankment, but only needs to be formed in a section that allows the average value per unit length in the longitudinal direction of the embankment to be calculated for the bending rigidity and embedded length of the steel sheet pile wall. In addition, the steel sheet pile wall in the above-described embodiment can be partially or entirely replaced by a wall made of a material other than steel sheet piles, for example, PC sheet piles.

[0027] The following describes the results of an analysis verifying the effect of the embankment reinforcement structure according to the embodiment of the present invention. In the following analysis, the maximum bending moment against the horizontal load acting on the upper end of the steel sheet pile wall in the embankment reinforcement structure was calculated for each of the conditions A to C shown in FIG. 8. In the analysis, the embankment was modeled at a 1 / 15 scale, with the embankment base width of 2.0 m, the top width of 0.4 m, and the height of 0.4 m. The steel sheet pile walls were installed on the slope shoulders on the water area side (outside the embankment) and the opposite side to the water area (inside the embankment), respectively, with an embedded depth of 0.9 m. The steel sheet piles constituting each steel sheet pile wall are different as shown in Table 1. Condition A shown in FIG. 8(A) is a state in which overtopping has not occurred and the slope of the embankment body on the opposite side to the water area is preserved. Condition B shown in FIG. 8(B) is a state in which overtopping has occurred and the slope of the embankment body on the opposite side to the water area has disappeared due to erosion. State C shown in Figure 8(C) is a state in which overflow continues from state B, causing scouring to a depth of 150 mm on the opposite side of the water area.

[0028] [Table 1]

[0029] As shown in Table 1 above, in Case 1, the steel sheet pile walls on both the outside and inside of the embankment were formed using a 1 / 15 scale model of a 10H hat-shaped steel sheet pile. In the case of the 10H type, the moment of inertia per meter of wall width (the dimension in the longitudinal direction of the embankment) of the steel sheet pile wall is approximately 10,000 cm 4 On the other hand, in Case 2, the steel sheet pile wall on the outside of the embankment was formed in a shape modeled on a 1 / 15 scale of a 10H hat-shaped steel sheet pile, as in Case 1, while the steel sheet pile wall on the inside of the embankment was formed in a shape modeled on a 1 / 15 scale of a 25H hat-shaped steel sheet pile. In the case of the 25H type, the moment of inertia per meter of wall width of the steel sheet pile wall was approximately 25,000 cm 4 / m. Therefore, in Case 2, the bending rigidity of the steel sheet pile wall on the inside of the embankment is greater than that of the steel sheet pile wall on the outside of the embankment. In Case 3, the steel sheet pile walls on both the outside and inside of the embankment were formed using a shape modeled on a 1 / 15 scale of 25H hat-shaped steel sheet piles.

[0030] For each case, the maximum bending moment M generated in each steel sheet pile wall in conditions B and C was max Table 2 shows the results of calculations of the maximum bending moment [kN / m] and the allowable stress ratio in each case (long-term allowable stress was set to 197 MPa). The results for condition A are omitted because the maximum bending moment and allowable stress ratio are even smaller than those for condition B. In condition B, where the embankment slope on the opposite side of the water body has disappeared due to erosion, the allowable stress is below 1 in all cases 1 to 3, but in condition C, where scouring has also occurred, the allowable stress exceeds 1 on both the outside and inside of the embankment in case 1. This is thought to be because the deformation of the steel sheet pile wall on the inside of the embankment became excessive due to the disappearance of the slope and scouring, and a large load was also applied to the steel sheet pile wall on the outside of the embankment through the tie rod. On the other hand, in case 2, although the maximum bending moment generated on the steel sheet pile wall on the inside of the embankment in condition C exceeded that of case 1, the allowable stress did not exceed 1 because the steel sheet pile wall was formed of 25H hat-shaped steel sheet piles with high bending rigidity. In addition, in Case 2, the high rigidity of the steel sheet pile wall on the inside of the embankment suppresses deformation, so the load on the steel sheet pile wall on the outside of the embankment via the tie rods is also reduced, and the allowable stress level of the steel sheet pile wall on the outside of the embankment, which is formed with 10H hat-shaped steel sheet piles, did not exceed 1. Even in Case 3, where both steel sheet pile walls were formed with 25H hat-shaped steel sheet piles, the allowable stress levels of the inside and outside of the embankment in Condition C did not exceed 1, but in Case 2, the steel sheet pile wall on the outside of the embankment is formed with 10H hat-shaped steel sheet piles, which is advantageous in that it reduces the amount of steel used.

[0031] [Table 2]

[0032] From the above results, it is found that in a levee reinforcement structure, between a first steel sheet pile wall driven into the water area side (outside of the levee) of the levee body and a second steel sheet pile wall driven into the opposite side of the water area (inside of the levee), making the bending rigidity of the second steel sheet pile wall larger than that of the first steel sheet pile wall is effective for improving the strength of the levee during flooding. Here, in order to be able to receive the expected resistance force from the ground even when the embedded depth is reduced by scouring, in addition to or instead of increasing the bending rigidity as described above, the embedded length of the second steel sheet pile wall can be made longer than that of the first steel sheet pile wall, which similarly improves the strength of the levee during flooding.

[0033] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art in the technical field to which the present invention pertains can come up with various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0034] 1... embankment body, 1A, 1B... slope, 1C... top surface, 2... water area, 10, 20... reinforcing structure, 11, 21... first steel sheet pile wall, 11X... missing part, 12, 22... second steel sheet pile wall, 13... tie rod, 211, 212, 221, 222... steel sheet pile.

Claims

1. a first steel sheet pile wall to be installed in the water area side portion of the embankment; a second steel sheet pile wall installed on a portion of the embankment opposite to the water area; A connecting member that connects the head portions of the first steel sheet pile wall and the second steel sheet pile wall; Equipped with When the longitudinal direction of the bank body is the x direction and the horizontal direction perpendicular to the x direction is the y direction, the bending rigidity EI of the first steel sheet pile wall in the y direction is determined for an average value per unit length in the x direction. １ and the embedment length L of the first steel sheet pile wall １ and the bending rigidity EI of the second steel sheet pile wall in the y direction. ２ and the embedment length L of the second steel sheet pile wall ２ and satisfy the relationship of formula (iv), The second steel sheet pile wall is composed of a type of steel sheet pile having a bending rigidity 10% or more greater than that of the steel sheet pile constituting the first steel sheet pile wall, in a reinforcing structure of a levee.

2. The bending rigidity EI of the first steel sheet pile wall １ and the bending rigidity EI of the second steel sheet pile wall ２ The embankment reinforcement structure according to claim 1, wherein the relationship of formula (ii) is satisfied. EI ２ >EI １ ・・・(ii)

3. The embankment reinforcement structure according to claim 2, wherein the bending rigidity in the y direction of the steel sheet piles constituting the second steel sheet pile wall is higher than the bending rigidity in the y direction of the steel sheet piles constituting the first steel sheet pile wall.

4. A first steel sheet pile wall to be installed in the water area side of the embankment; A second steel sheet pile wall is installed on a portion of the embankment opposite to the water area; and A connecting member that connects the head portions of the first steel sheet pile wall and the second steel sheet pile wall; Equipped with A reinforcing structure for a levee, in which, when the longitudinal direction of the embankment body is defined as the x direction and the horizontal direction perpendicular to the x direction is defined as the y direction, steel sheet piles are intermittently arranged at predetermined intervals in the x direction in the first steel sheet pile wall, and steel sheet piles are continuously arranged in the second steel sheet pile wall, so that, for average values ​​per unit length in the x direction, a bending stiffness EI 1 in the y direction of the first steel sheet pile wall and an embedded length L 1 of the first steel sheet pile wall, and a bending stiffness EI 2 in the y direction of the second steel sheet pile wall and an embedded length L 2 of the second steel sheet pile wall satisfy the relationship of formula (iv).

5. The embedment length L of the first steel sheet pile wall １ and the embedment length L of the second steel sheet pile wall ２ The embankment reinforcement structure according to any one of claims 1 to 4, wherein the relationship of formula (iii) is satisfied. L ２ >L １ ・・・(iii)

6. The embankment reinforcement structure of claim 5, wherein the embedded length of some of the steel sheet piles constituting the second steel sheet pile wall is longer than the embedded length of the remaining steel sheet piles constituting the second steel sheet pile wall and the steel sheet piles constituting the first steel sheet pile wall, or the embedded length of some of the steel sheet piles constituting the first steel sheet pile wall is shorter than the embedded length of the remaining steel sheet piles constituting the first steel sheet pile wall and the steel sheet piles constituting the second steel sheet pile wall.

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