Dam body reinforcement structure

Abstract

To suppress scouring of a dam body.SOLUTION: A dam body reinforcement structure comprises: a dam body 20; a wall-shaped ground improvement portion 30 arranged continuously along the dam body 20 inside the dam body 20; and a plurality of convex ground improvement portions 40 provided at intervals along the longitudinal direction of the wall-shaped ground improvement portion 30 and protruding from the wall-shaped ground improvement portion 30 toward a river 12 side.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a bank reinforcement structure. [Background technology]

[0002] 2. Description of the Related Art Reinforcement structures that reinforce a levee body with a soil improvement body are known (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-032690 A [Patent Document 2] JP 2015-081436 A Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, it is possible to reinforce embankments of rivers, reservoirs, etc. by forming wall-shaped ground improvement bodies along the embankments.

[0005] However, in this case, when the water level of rivers or reservoirs rises, the embankment may be scoured along the surface of the wall-shaped ground improvement body, which may increase the amount of runoff (deficiency) of the embankment.

[0006] In consideration of the above, an object of the present invention is to suppress scouring of a cut-off wall. [Means for solving the problem]

[0007] The embankment reinforcement structure described in claim 1 comprises a embankment, a wall-shaped ground improvement section arranged continuously along the inside of the embankment, and a plurality of convex ground improvement sections arranged at intervals in the longitudinal direction of the wall-shaped ground improvement section and protruding from the wall-shaped ground improvement section toward the water body.

[0008] According to the embankment reinforcement structure of claim 1, the wall-shaped ground improvement section is provided continuously along the inside of the embankment. This wall-shaped ground improvement section is provided with a plurality of convex ground improvement sections. The plurality of convex ground improvement sections are provided at intervals in the longitudinal direction of the wall-shaped ground improvement section and protrude from the wall-shaped ground improvement section toward the water body.

[0009] As a result, when the water level in rivers and reservoirs rises, the water flowing along the embankment is slowed down by the multiple convex ground improvement sections. As a result, scouring of the embankment is suppressed, and the amount of runoff (loss) of the embankment can be reduced.

[0010] The embankment reinforcement structure according to claim 2 is the embankment reinforcement structure according to claim 1, wherein the convex ground improvement portion protrudes from the wall-like ground improvement portion in the wall thickness direction of the wall-like ground improvement portion.

[0011] According to the embankment reinforcement structure of claim 2, the convex ground improvement portion protrudes from the wall-like ground improvement portion in the wall thickness direction of the wall-like ground improvement portion, thereby improving the workability of the convex ground improvement portion.

[0012] The embankment reinforcement structure described in claim 3 is the embankment reinforcement structure described in claim 1, in which the convex ground improvement portion protrudes from the wall-shaped ground improvement portion in a direction inclined with respect to the wall thickness direction of the wall-shaped ground improvement portion in a plan view.

[0013] According to the bank body reinforcement structure of claim 3, the convex ground improvement portion protrudes from the wall-shaped ground improvement portion in a direction inclined with respect to the wall thickness direction in plan view.

[0014] Here, by increasing or decreasing the inclination angle of the convex ground improvement section relative to the wall thickness direction of the wall-shaped ground improvement section, it is possible to adjust the deceleration rate of the water flowing along the embankment when the water level of a river, reservoir, etc. rises. Therefore, scouring of the embankment can be effectively suppressed when the water level of a river, reservoir, etc. rises.

[0015] The embankment reinforcement structure described in claim 4 is the embankment reinforcement structure described in claim 3, in which the embankment is arranged along a river as the water body, and the convex ground improvement portion is inclined toward the upstream or downstream side of the river with respect to the wall thickness direction in a plan view.

[0016] According to the embankment reinforcement structure of claim 4, the embankment is provided along a river. The convex ground improvement portion is inclined toward the upstream side or downstream side of the river with respect to the wall thickness direction of the wall-shaped ground improvement portion in a plan view.

[0017] Here, by inclining the convex ground improvement section toward the upstream side of the river in the wall thickness direction of the wall-shaped ground improvement section, the water flow along the embankment can be slowed down when the river floods, thereby suppressing scouring of the embankment.

[0018] On the other hand, if the convex ground improvement section is inclined toward the downstream side of the river in the wall thickness direction of the wall-shaped ground improvement section, the water flow along the embankment can be slowed down and the occurrence of turbulence can be suppressed when the river floods. This prevents the embankment from being scoured.

[0019] Therefore, for example, by changing the inclination direction of the convex ground improvement section relative to the wall thickness direction of the wall-shaped ground improvement section depending on the characteristics of the water flow along the embankment when the river is flooded, scouring of the embankment can be efficiently suppressed.

[0020] The embankment reinforcement structure according to claim 5 is the embankment reinforcement structure according to claim 1, in which the convex ground improvement portion is formed at least from the lower end of the embankment to an upper portion thereof.

[0021] According to the embankment reinforcement structure of claim 5, the convex ground improvement portion is formed at least from the lower end to the upper part of the embankment, which makes it possible to suppress scouring of the embankment at least from the lower end to the upper part of the embankment when the water level of a river, a reservoir, etc. rises.

[0022] The bank reinforcement structure according to claim 6 is the bank reinforcement structure according to any one of claims 1 to 5, wherein the wall-shaped ground improvement portion and the convex ground improvement portion are formed by columnar improvement bodies.

[0023] According to the embankment reinforcement structure of claim 6, the wall-shaped ground improvement portion and the convex ground improvement portion are formed by columnar improvement bodies. Here, the columnar improvement bodies can be constructed by a small construction machine. Therefore, the wall-shaped ground improvement portion and the convex ground improvement portion can be constructed even in a narrow embankment. Effect of the Invention

[0024] As described above, according to the present invention, scouring of the embankment can be suppressed. [Brief description of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view showing a bank body to which a bank body reinforcement structure according to one embodiment is applied. [Diagram 2] 2 is a cross-sectional view taken along line 2-2 of FIG. 1. [Diagram 3] FIG. 4 is a partially enlarged cross-sectional view of FIG. [Figure 4] FIG. 4 is a cross-sectional view corresponding to FIG. 3 and showing a bank body to which a modified example of the bank body reinforcement structure according to one embodiment is applied. [Diagram 5] FIG. 4 is a cross-sectional view corresponding to FIG. 3 and showing a bank body to which a modified example of the bank body reinforcement structure according to one embodiment is applied. [Figure 6] FIG. 13 is a vertical cross-sectional view showing a circulating water tank used in a comparative experiment. [Figure 7] 7(A) is a plan view showing a levee model according to an embodiment used in a comparative experiment, and FIG. 7(B) is a cross-sectional view taken along line 7B-7B in FIG. 7(A). [Figure 8] 8(A) is a plan view showing a bank model according to Comparative Example 1 used in a comparative experiment, and FIG. 8(B) is a cross-sectional view taken along line 8B-8B in FIG. 8(A). [Figure 9] 9(A) is a plan view showing a bank model according to Comparative Example 2 used in a comparative experiment, and FIG. 9(B) is a cross-sectional view taken along line 9B-9B in FIG. 9(A). [Figure 10] 13 is a graph showing the experimental results of a comparative experiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, one embodiment will be described with reference to the drawings.

[0027] (levee body) 1 and 2 show a levee body 20 to which the levee body reinforcement structure according to this embodiment is applied. As an example, the levee body 20 is a river levee built along a river 12. The levee body 20 is formed by an embankment built on the ground 10.

[0028] 1 indicates, as an example, the water level of the river 12 when the river 12 is flooded. The river 12 is also an example of a water area.

[0029] The levee body 20 has a trapezoidal cross-sectional shape as a whole. The levee body 20 has a top surface 20T, a front slope 20S1 on the river 12 side, and a back slope 20S2 on the opposite side to the river 12. The levee body 20 is reinforced by a wall-shaped ground improvement section 30 and a plurality of convex ground improvement sections 40. The cross-sectional shape of the levee body 20 is not limited to a trapezoidal shape and can be changed as appropriate.

[0030] (Wall-shaped ground improvement section) The wall-shaped ground improvement section 30 is provided continuously in a wall shape inside the embankment body 20 along the longitudinal direction (direction of arrow L) of the embankment body 20. This wall-shaped ground improvement section 30 is a portion where the embankment body 20 and the ground directly below the embankment body 20 (hereinafter referred to as "directly below ground 10A") are improved in a wall shape from the top surface 20T of the embankment body 20 along the longitudinal direction of the embankment body 20. Also, the lower end of the wall-shaped ground improvement section 30 reaches (is embedded in) the impermeable layer 10K of the directly below ground 10A, for example.

[0031] The depth of the wall-shaped ground improvement section 30 is appropriately set according to the depth of the river 12 and the strata of the ground 10A directly below. The wall-shaped ground improvement section 30 only needs to be formed from the lower end to the upper part of the embankment 20, and does not necessarily need to extend between the embankment 20 and the ground 10A directly below.

[0032] The wall-shaped ground improvement section 30 has a plurality of columnar improvement bodies 32 connected in a wall shape. The columnar improvement bodies 32 are formed in a cylindrical shape. The columnar improvement bodies 32 are formed across the levee body 20 and the ground 10A directly below, and their lower ends reach the impermeable layer 10K of the ground 10A directly below.

[0033] When constructing the columnar improvement body 32, the embankment body 20 and the ground 10A directly below are excavated from the top surface 20T of the embankment body 20 with an auger or the like (not shown), while a cement-based solidification material such as cement milk is injected into the embankment body 20 and the ground 10A directly below. The cement-based solidification material and the excavated soil are then stirred and mixed to form (construct) the columnar improvement body 32 in the embankment body 20 and the ground 10A directly below.

[0034] (Convex ground improvement section) The multiple convex ground improvement sections 40 are provided in a comb shape in the wall-shaped ground improvement section 30. Specifically, the multiple convex ground improvement sections 40 are provided at intervals in the longitudinal direction of the wall-shaped ground improvement section 30 (embankment body 20). In addition, the multiple convex ground improvement sections 40 protrude from the wall-shaped ground improvement section 30 toward the river 12 side.

[0035] More specifically, the multiple convex ground improvement sections 40 protrude from the wall-shaped ground improvement section 30 in the wall thickness direction (arrow W direction, width direction of the embankment 20) of the wall-shaped ground improvement section 30. In other words, the multiple convex ground improvement sections 40 are provided approximately perpendicular to the wall-shaped ground improvement section 30.

[0036] The multiple convex ground improvement sections 40 are formed by improving the embankment body 20 and the ground 10A directly below from the top surface 20T and front slope 20S1 of the embankment body 20 along the width direction of the embankment body 20. The lower end of the wall-shaped ground improvement section 30 reaches (is embedded in) the impermeable layer 10K of the ground 10A directly below, for example.

[0037] The depth of the convex ground improvement portion 40 is appropriately set according to the depth of the river 12 and the strata of the ground 10A directly below. The convex ground improvement portion 40 only needs to be formed from the lower end to the upper part of the embankment 20, and does not necessarily need to extend between the embankment 20 and the ground 10A directly below.

[0038] The convex ground improvement section 40 has a plurality of (two in this embodiment) connected columnar improvement bodies 42. The columnar improvement bodies 42 are formed in a cylindrical shape. The columnar improvement bodies 42 are formed across the levee body 20 and the ground 10A directly below, with their lower ends reaching the impermeable layer 10K of the ground 10A directly below.

[0039] The number of columnar improvement bodies 42 constituting the convex ground improvement section 40 is not limited to two, but may be one, or three or more. In other words, the convex ground improvement section 40 can be constituted by at least one columnar improvement body 42.

[0040] When constructing the columnar improvement body 42, the embankment body 20 and the ground 10A directly below are excavated from the top surface 20T and the front slope 20S1 of the embankment body 20 with an auger or the like (not shown), while a cement-based solidification material such as cement milk is injected into the embankment body 20 and the ground 10A directly below. The cement-based solidification material and the excavated soil are then stirred and mixed to form (construct) the columnar improvement body 42 in the embankment body 20 and the ground 10A directly below.

[0041] The convex ground improvement section 40 (columnar improvement body 42) formed on the front slope 20S1 of the embankment body 20 is provided within a range that can be worked on by heavy machinery installed on the top surface 20T of the embankment body 20. In this embodiment, the convex ground improvement section 40 extends across the top surface 20T and the front slope 20S1 of the embankment body 20, but the convex ground improvement section 40 may be formed only on the top surface 20T of the embankment body 20, or may be formed only on the front slope 20S1 of the embankment body 20.

[0042] (action) Next, the operation of this embodiment will be described.

[0043] According to this embodiment, the wall-shaped ground improvement section 30 is provided continuously inside the embankment body 20 along the embankment body 20. This wall-shaped ground improvement section 30 suppresses destruction of the embankment body 20 due to erosion or overflow when the river 12 is flooded.

[0044] In addition, the wall-shaped ground improvement section 30 is formed across the embankment body 20 and the ground 10A directly below. This prevents water from seeping into the boundary between the embankment body 20 and the ground 10A directly below when the river 12 is flooded, thereby preventing the embankment body 20 from being destroyed.

[0045] Furthermore, the wall-shaped ground improvement section 30 is provided with a plurality of convex ground improvement sections 40. The plurality of convex ground improvement sections 40 are provided at intervals in the longitudinal direction of the wall-shaped ground improvement section 30 and protrude from the wall-shaped ground improvement section 30 to the river 12 side.

[0046] This, for example, as shown in Fig. 3, suppresses scouring of the embankment 20 along the surface of the wall-shaped ground improvement section 30 on the river 12 side. This makes it possible to reduce the amount of runoff (loss) of the embankment 20. Note that the destruction shape (scouring state) of the embankment 20 shown in Fig. 3 is an example, and is not limited thereto.

[0047] Furthermore, when the river 12 is flooded, the water flow F flowing along the embankment body 20 is decelerated by the multiple convex ground improvement portions 40. As a result, scouring of the embankment body 20 by the water flow F is further suppressed.

[0048] Furthermore, the convex ground improvement portion 40 is formed from the lower end to the upper part of the embankment body 20. This makes it possible to prevent scouring of almost the entire embankment body 20 when the river 12 is flooded.

[0049] In addition, the multiple convex ground improvement portions 40 protrude from the wall-shaped ground improvement portion 30 in the wall thickness direction (arrow W direction) of the wall-shaped ground improvement portion 30. This improves the workability of the convex ground improvement portion 40.

[0050] Furthermore, the wall-shaped ground improvement section 30 and the convex ground improvement section 40 are formed by a plurality of columnar improvement bodies 32, 42. Here, the columnar improvement bodies 32, 42 can be constructed by a small construction machine. Therefore, the wall-shaped ground improvement section 30 and the convex ground improvement section 40 can be constructed even for a levee body 20 with a narrow top surface 20T.

[0051] (Modification) Next, a modification of the above embodiment will be described.

[0052] In the above embodiment, the convex ground improvement portion 40 protrudes from the wall-shaped ground improvement portion 30 in the wall thickness direction of the wall-shaped ground improvement portion 30. However, the protruding direction of the convex ground improvement portion 40 is not limited to the wall thickness direction of the wall-shaped ground improvement portion 30 and can be changed as appropriate.

[0053] For example, in the modified example shown in Fig. 4, the convex ground improvement section 40 protrudes from the wall-shaped ground improvement section 30 in a direction inclined with respect to the wall thickness direction of the wall-shaped ground improvement section 30 in a plan view. More specifically, the convex ground improvement section 40 inclines toward the upstream side of the river 12 (the opposite side to the arrow F) with respect to the wall thickness direction of the wall-shaped ground improvement section 30 in a plan view. This makes it possible to more efficiently slow down the water flow F flowing along the embankment 20 when the river 12 is flooded.

[0054] 5, the convex ground improvement section 40 is inclined toward the downstream side (arrow F side) of the river 12 with respect to the wall thickness direction of the wall-shaped ground improvement section 30 in a plan view. This makes it possible to slow down the water flowing along the embankment body 20 and suppress the occurrence of turbulence when the river 12 is flooded.

[0055] In this way, by changing the inclination direction of the convex ground improvement section 40 relative to the wall thickness direction of the wall-shaped ground improvement section 30 according to the characteristics of the water flow F that flows along the embankment body 20 when the river 12 is flooded, it is possible to efficiently suppress scouring of the embankment body 20. Note that the destruction shapes (scouring states) of the embankment body 20 shown in Figures 4 and 5 are merely examples and are not intended to be limiting.

[0056] In addition, by increasing or decreasing the inclination angle of the convex ground improvement portion 40 relative to the wall thickness direction of the wall-shaped ground improvement portion 30, it is possible to adjust the deceleration rate of the water flow F flowing along the embankment body 20 when the river 12 is flooded. Therefore, scouring of the embankment body 20 can be efficiently suppressed when the river 12 is flooded.

[0057] In the above embodiment, the wall-shaped ground improvement section 30 and the convex ground improvement section 40 are formed by the columnar improvement method (columnar improvement bodies 32, 42). However, the wall-shaped ground improvement section 30 and the convex ground improvement section 40 are not limited to the columnar improvement method and may be constructed by other ground improvement methods.

[0058] Furthermore, the embankment reinforcement structure according to the above embodiment may be implemented in combination with a lattice-shaped ground improvement body formed in a lattice shape in a plan view. For example, a lattice-shaped ground improvement body having the wall-shaped ground improvement section 30 as a part of a wall may be formed inside the embankment 20 in a direction parallel to the embankment normal and on the opposite (land) side to the river 12, and a plurality of convex ground improvement sections may be provided in the wall-shaped ground improvement section on the river 12 (water area side) side of the lattice-shaped ground improvement body. Furthermore, the embankment reinforcement structure according to the above embodiment may be implemented in combination with other ground improvement bodies, not limited to the lattice-shaped ground improvement body.

[0059] In the above embodiment, the embankment 20 is a river embankment installed along the river 12. However, the embankment 20 is not limited to a river embankment, and may be a coastal embankment installed along a coast or a pond embankment installed along a reservoir. In this case, the sea or the reservoir is an example of a water area.

[0060] (Comparative experiment) Next, a comparative experiment will be described.

[0061] (overview) In this comparative experiment, a reduced-scale model of the embankment according to the embodiment (hereinafter referred to as the "embankment model") and a model of the embankment according to the comparative example were placed in a circulating water tank, and the state of destruction (shape of destruction) of each embankment model was observed. Then, the cross-sectional loss rate of each embankment model was calculated from the state of destruction of each embankment model, and the results were compared.

[0062] (circulating water tank) 6 shows a circulating water tank 50. The circulating water tank 50 is a long water tank. Water 52 in the circulating water tank 50 is circulated in the longitudinal direction (arrow direction) of the circulating water tank 50 by a circulation pipe 54 and a circulation pump 56. The flow rate of the water in the circulating water tank 50 can be adjusted by the output of the circulation pump 56.

[0063] (Empty body model) 7(A) and 7(B) show a levee model 20X according to the embodiment. The levee model 20X according to the embodiment is applied with the levee reinforcement structure according to the above embodiment. That is, a wall-shaped ground improvement section 30 and a convex ground improvement section 40 are formed in the levee model 20X.

[0064] 8(A) and 8(B) show a levee model 20Y1 according to Comparative Example 1. The levee model 20Y1 according to Comparative Example 1 does not include the levee reinforcement structure according to the above embodiment. In other words, the levee model 20Y1 does not include the wall-shaped ground improvement section 30 and the convex ground improvement section 40.

[0065] 9(A) and 9(B) show a cut-off wall model 20Y2 according to Comparative Example 2. In the cut-off wall model 20Y2 according to Comparative Example 2, only the wall-shaped ground improvement section 30 is formed, and the convex ground improvement section 40 is not formed.

[0066] (Experimental Results) Fig. 10 shows graphs X, Y1, and Y2 showing the cross-sectional loss ratios of the embankment body models 20X, 20Y1, and 20Y2 according to the embodiment and comparative examples 1 and 2. The horizontal axis of Fig. 10 represents the distance from the upstream of each of the embankment body models 20X, 20Y1, and 20Y2 (longitudinal position), and the horizontal axis of Fig. 10 represents the cross-sectional loss ratios [%] of each of the embankment body models 20X, 20Y1, and 20Y2.

[0067] 10, the cross-sectional loss ratio of the embankment model 20Y2 of Comparative Example 2 was generally higher than the cross-sectional loss ratio of the embankment model 20Y1 of Comparative Example 1. This is considered to be because, in the embankment model 20Y2 of Comparative Example 2, the embankment body 20 was scoured along the surface of the wall-shaped ground improvement section 30 on the water 52 side, and the runoff amount (loss amount) of the embankment body 20 increased.

[0068] On the other hand, the cross-sectional defect ratio of the embankment model 20X according to the embodiment was lower than that of the embankment model 20Y2 according to Comparative Example 2, and was approximately the same as that of the embankment model 20Y1 according to Comparative Example 1. This confirmed that the convex ground improvement section 40 suppressed the destruction (scouring) of the embankment body 20.

[0069] Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and one embodiment and various modified examples may be used in appropriate combination, and it is of course possible to implement the present invention in various forms without departing from the gist of the present invention. [Explanation of symbols]

[0070] 12 Rivers (water bodies) 20 Embankment body 30 Wall-like ground improvement section 32 Improved columnar body 40 Convex Site Improvement 42 Columnar Improvement

Claims

1. The embankment and a wall-shaped ground improvement section provided continuously along the bank inside the bank; A plurality of convex ground improvement sections are provided at intervals in the longitudinal direction of the wall-shaped ground improvement section and protrude from the wall-shaped ground improvement section toward the water area side; A dam body reinforcement structure equipped with:

2. The convex ground improvement portion protrudes from the wall-shaped ground improvement portion in the wall thickness direction of the wall-shaped ground improvement portion, The embankment reinforcement structure according to claim 1.

3. The convex ground improvement portion protrudes from the wall-shaped ground improvement portion in a direction inclined with respect to the wall thickness direction of the wall-shaped ground improvement portion in a plan view. The embankment reinforcement structure according to claim 1.

4. The embankment is provided along a river as the water area, The convex ground improvement portion is inclined toward the upstream side or downstream side of the river with respect to the wall thickness direction in a plan view. The embankment reinforcement structure according to claim 3.

5. The convex ground improvement portion is formed at least from the lower end portion of the embankment to the upper portion thereof. The embankment reinforcement structure according to claim 1.

6. The wall-shaped ground improvement portion and the convex ground improvement portion are formed by columnar improvement bodies. The embankment reinforcement structure according to any one of claims 1 to 5.

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