Lightweight banking structure, and manufacturing method of lightweight banking structure

Abstract

To prevent subsidence of a surface layer of a lightweight banking structure.SOLUTION: A lightweight banking structure 10 comprises: a block layer 12 composed of a plurality of foam blocks 14 stacked at a side of a structure 50 such as a bridge; and a foam layer 16 made of a foam such as polyurethane foam and formed between the structure 50 and the block layer 12. The foam layer 16 includes a skin layer 22 formed along the block layer 12. The lightweight banking structure 10 comprises a floor slab 18 provided on the foam blocks 14. The foam layer 16 is formed between the structure 50 and the floor slab 18.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a lightweight embankment structure and a method for manufacturing a lightweight embankment structure. [Background technology]

[0002] For example, at the back of structures such as bridge abutments and concrete retaining walls, a lightweight embankment structure is formed using the EPS method, in which polystyrene foam blocks are stacked as embankment material, in order to reduce rear earth pressure (see, for example, Patent Document 1). In such a lightweight embankment structure, a concrete deck is placed on top of the stacked polystyrene foam blocks in order to distribute the load applied to the polystyrene foam blocks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-210715 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to reduce the localized excessive load that the deck applies to the rear surface of the structure during an earthquake, Patent Document 1 proposes placing a buffer material between the structure and the deck. However, because the buffer material in Patent Document 1 is primarily intended to buffer the load of the deck, there is a risk that the soil covering the polystyrene foam blocks will flow into the gaps between the polystyrene foam blocks that break apart during an earthquake, causing the surface layer of the lightweight embankment structure to sink.

[0005] The present invention has been proposed in consideration of the above-mentioned problems associated with the conventional technology, and aims to provide a lightweight embankment structure and a method for manufacturing a lightweight embankment structure that can prevent subsidence of the surface layer. [Means for solving the problem]

[0006] The first aspect of the lightweight embankment structure according to the present invention is as follows: a block layer consisting of a plurality of foam blocks stacked on the side of the structure; a foam layer formed between the structure and the block layer, The foam layer includes a skin layer formed along the block layer.

[0007] A second aspect of the lightweight embankment structure according to the present invention is the same as the first aspect, A floor slab is provided on the foam block, The foam layer may be formed between the structure and the deck.

[0008] A third aspect of the lightweight embankment structure according to the present invention is the same as the second aspect, The floor may include a floor slab provided on the foam layer and separate from the floor slab provided on the foam block.

[0009] An example of a manufacturing method for a lightweight embankment structure according to the present invention is as follows: A step of forming a foam skin layer along a block layer formed by stacking a plurality of foam blocks on a side of a structure by spraying a foam material onto a surface of the block layer facing the structure; The present invention also includes a step of forming a foamed layer including the skin layer between the structure and the block layer by foaming a foam material between the structure and the skin layer. Effect of the Invention

[0010] The lightweight embankment structure according to the present invention can prevent subsidence of the surface layer. According to the manufacturing method of the lightweight embankment structure of the present invention, subsidence of the surface layer of the lightweight embankment structure can be prevented. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing a lightweight embankment structure according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing the manufacturing process of the lightweight embankment structure of the embodiment. [Diagram 3] FIG. 2 is an explanatory diagram showing the manufacturing process of the lightweight embankment structure of the embodiment. [Figure 4] A schematic cross-sectional view showing a modified example of a lightweight embankment structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, the light-weight embankment structure and the manufacturing method thereof according to the present invention will be described below with reference to the attached drawings, using preferred examples. Note that the embodiment and drawings described below are merely examples of the present invention, and are not intended to limit the present invention to these configurations, and may be modified as appropriate without departing from the scope of the present invention. EXAMPLES

[0013] As shown in Fig. 1, the lightweight embankment structure 10 according to the embodiment includes a block layer 12 composed of a plurality of foam blocks 14 piled up on the side of a structure 50, and a foam layer 16 formed between the structure 50 and the block layer 12. The lightweight embankment structure 10 also includes embankment decks (deck slabs) 18, 20 provided on the foam blocks 14. The structure 50 according to the embodiment is a bridge including a road deck 54 supported by an abutment 52, and the lightweight embankment structure 10 is provided on the side of the abutment 52 of the bridge.

[0014] The block layer 12 is composed of a plurality of foam blocks 14 piled up on the side of the abutment 52. The foam blocks 14 are made of foam such as polystyrene foam. The foam blocks 14 are rectangular parallelepipeds formed with a size of, for example, about 100 cm wide × 200 cm long × 50 cm high, although not particularly limited thereto. The block layer 12 is preferably provided at a distance of, for example, about 0.5 m to 2 m from the abutment 52, from the viewpoints of the buffering effect between the abutment 52 and the foam blocks 14 and the ease of forming the foam layer 16, although not particularly limited thereto. The block layer 12 may have a vertical surface on the abutment 52 side as shown in FIG. 1, a stepped surface on the abutment 52 side, or another shape.

[0015] The embankment slabs 18, 20 are reinforced or unreinforced concrete layers having a higher specific gravity than the foam block 14. The embankment slabs 18, 20 are provided for the purpose of leveling unevenness, dispersing the load applied to the lightweight embankment structure 10 from above, fixing the foam block 14, and preventing the foam block 14 from floating up. The lightweight embankment structure 10 of the embodiment includes, as embankment slabs, a middle embankment slab 18 sandwiched between the foam blocks 14 at the top and bottom, and an upper embankment slab 20 disposed on the topmost foam block 14. The middle embankment slab 18 is disposed inside the block layer 12 with a gap between it and the abutment 52. The upper embankment slab 20 is provided from above the topmost foam block 14 in the block layer 12 to above the foam layer 16.

[0016] The foam layer 16 is made of a foam such as polyurethane foam. Among foams, on-site foamed polyurethane foam that is foamed and cured at the construction site is preferable from the viewpoints of light weight, workability, adhesion to the abutment 52, etc. The foam layer 16 includes a skin layer 22 formed along the block layer 12. The skin layer 22 is a part with a higher density due to having smaller or fewer air bubbles than other parts of the foam. In addition, in the foam layer 16, the part between the skin layer 22 and the block layer 12 is made of a foam with a lower density than the skin layer 22. In addition, in the foam layer 16, the thickness from the skin layer 22 to the block layer 12 is formed to be smaller than the thickness from the skin layer 22 to the abutment 52, and it is desirable to make the thickness from the skin layer 22 to the block layer 12 as small as possible. The thickness from the skin layer 22 to the block layer 12 is not particularly limited, but is formed to be, for example, about 1 cm to 30 cm.

[0017] The compressive strength (JIS A9511) of the foam layer 16 is not particularly limited, but is, for example, 120 kN / m 2 ~400kN / m 2 The density of the foam layer 16 (JIS A9511) is not particularly limited, but is preferably about 30 kg / m 3 ~50kg / m 3 It is preferable that the amount is about 100%.

[0018] Next, a manufacturing method of the lightweight embankment structure 10 according to the embodiment will be described. The foam layer 16 is made of polyurethane foam in situ. In the backfill space between the abutment 52 and the natural ground 60, the foam blocks 14 are piled up at intervals from the abutment 52 (see FIG. 2(a)). Next, the middle embankment deck 18 is formed on the foam blocks 14 piled up to the required height (see FIG. 2(b)). The middle embankment deck 18 may be formed of cast-in-situ concrete, which is concrete poured on the foam blocks 14, or a precast concrete plate may be placed on the foam blocks 14. However, since unevenness can be adjusted, it is preferable to form the middle embankment deck 18 with cast-in-situ concrete. Furthermore, the foam blocks 14 are piled up on the middle embankment deck 18 at intervals from the abutment 52 (see FIG. 2(c)).

[0019] Next, a foam layer 16 is formed between the block layer 12 and the abutment 52. First, a foaming material, which is a mixture of liquid A (polyol) and liquid B (isocyanate) on-site, is thinly sprayed onto the surface of the block layer 12 facing the abutment 52 and foamed, thereby forming a part of the foam layer 16 made of polyurethane foam along the block layer 12 (see FIG. 3(a)). At this time, a skin layer 22 is formed on the surface of part of the foam layer 16.

[0020] Next, a foaming material made of a mixture of liquid A (polyol) and liquid B (isocyanate) is sprayed and foamed on-site between the skin layer 22 and the abutment 52 to form the remainder of the foamed layer 16 made of polyurethane foam (see FIG. 3(b)). This spraying operation is repeated from the bottom up, filling the space between the skin layer 22 and the abutment 52 with polyurethane foam, forming the foamed layer 16 including the skin layer 22 between the abutment 52 and the block layer 12. Note that even if the polyurethane foam is formed in multiple batches, the foamed layer 16 remains as a single mass due to the adhesiveness of the polyurethane foam.

[0021] Next, the upper embankment slab 20 is formed on the top foam block 14 and the foam layer 16 (see FIG. 3(c)). The upper embankment slab 20 may be formed by pouring concrete on the foam block 14, or by placing a precast concrete plate on the foam block 14 and the foam layer 16. However, it is preferable to form the upper embankment slab 20 by pouring concrete on the foam block 14, since this allows for unevenness adjustment. Finally, the upper embankment slab 20 is covered with soil to obtain the lightweight embankment structure 10 of the embodiment (see FIG. 1). The surface layer of the lightweight embankment structure 10 is not limited to being covered with soil as in the embodiment, and may be covered with asphalt or concrete in addition to or instead of soil.

[0022] As described above, the manufacturing method of the embodiment includes a step of forming a polyurethane foam skin layer 22 along the block layer 12 by spraying a foaming material onto the surface of the block layer 12 facing the abutment 52, and a step of forming a foam layer 16 including the skin layer 22 between the abutment 52 and the block layer 12 by foaming the foaming material between the abutment 52 and the skin layer 22. By previously forming the polyurethane foam skin layer 22 along the block layer 12 on the surface of the block layer 12 facing the abutment 52 in this manner, the foaming heat of the polyurethane foam generated when forming the foam layer 16 between the abutment 52 and the skin layer 22 can be blocked by the previously formed polyurethane foam, thereby preventing adverse effects on the foam block 14. In addition, the polyurethane foam that directly contacts the foam block 14 of the block layer 12 can be made thin, so that the effect of the foaming heat of the polyurethane foam formed along the block layer 12 on the foam block 14 can be suppressed.

[0023] In the lightweight embankment structure 10, the foam layer 16 is formed between the abutment 52 and the block layer 12, so that even if the abutment 52 of the structure 50 vibrates due to an earthquake, the vibration of the abutment 52 is buffered by the foam layer 16, and the vibration of the abutment 52 can be prevented from being transmitted to the block layer 12. According to the lightweight embankment structure 10, even if an earthquake occurs, the inertial force of the structure 50 is not easily transmitted from the structure 50 to the block layer 12, so that it is possible to prevent the foam block 14 from shifting or the occurrence of gaps around the foam block 14 during an earthquake. Therefore, it is possible to prevent the outflow of soil covering the upper side of the block layer 12 and prevent the surface layer of the lightweight embankment structure 10 from subsiding.

[0024] In the lightweight embankment structure 10, since the foam layer 16 is formed between the abutment 52 and the middle embankment deck 18, even if the middle embankment deck 18 shakes horizontally due to an earthquake, the foam layer 16 can cushion the vibration of the middle embankment deck 18 and prevent the middle embankment deck 18 from colliding with the abutment 52. According to the lightweight embankment structure 10, since the middle embankment deck 18 is unlikely to vibrate even in the event of an earthquake, it is possible to prevent the foam blocks 14 from shifting or gaps from forming around the foam blocks 14 during an earthquake. Therefore, it is possible to prevent the outflow of soil covering the upper side of the block layer 12 and prevent the surface layer of the lightweight embankment structure 10 from subsiding.

[0025] In the lightweight embankment structure 10, the upper embankment deck 20 is placed from above the top foam block 14 to above the foam layer 16. The foam layer 16 is a single mass of polyurethane foam and does not fall apart like the foam block 14, so it can cushion the vibration of the upper embankment deck 20 caused by earthquakes.

[0026] By constructing the foam layer 16 from polyurethane foam, which has better creep characteristics than the foam blocks 14, such as polystyrene foam, it is possible to suppress subsidence over time of the surface layer of the lightweight embankment structure 10. In addition, since the foam layer 16 is lighter than soil and sand, it is possible to minimize the load applied to the supporting ground. Furthermore, the foam layer 16 adheres to the surrounding objects such as the abutment 52, block layer 12, and middle embankment deck 18 due to the self-adhesiveness unique to polyurethane foam, so that a stable lightweight embankment structure 10 can be obtained that is integrated with the surroundings.

[0027] In particular, forming the foam layer 16 with on-site foamed polyurethane foam, which is a foaming material made by mixing liquid A (polyol) and liquid B (isocyanate) on-site, has the following advantages. Since on-site foamed polyurethane foam develops strength in about 24 hours after spraying, it takes less time to develop strength than concrete. In addition, since on-site foamed polyurethane foam is a hardening resin, it does not require rolling compaction as in the case of backfilling with soil and sand. Furthermore, since on-site foamed polyurethane foam becomes solid from liquid, it can be easily filled according to the surrounding shapes of the abutments 52 and the block layer 12. In this way, the construction efficiency of the foam layer 16 is increased, and the construction period of the lightweight embankment structure 10 can be significantly shortened. In addition, since the foam material is lightweight, the foam layer 16 can be formed by human labor without requiring large heavy machinery, and the construction area of ​​the lightweight embankment structure 10 has a high degree of freedom, and the foam layer 16 can be formed even in places where vehicles cannot enter.

[0028] (Example of change) The present invention is not limited to the above, and may be, for example, as follows: Note that the present invention is not limited to the specific descriptions of the embodiment and the following modified examples. (1) In the embodiment, the upper embankment deck is provided on the top foam block and on the foam layer, but this is not limited thereto, and the embankment deck provided on the top foam block and the embankment deck provided on the foam layer may be separate. The modified lightweight embankment structure 30 shown in FIG. 4 includes a first upper embankment deck 32 formed on the top foam block 14, and a second upper embankment deck 34 formed separately from the first upper embankment deck 32 on the foam layer 16. The second upper embankment deck 34 is shifted upward from the first upper embankment deck 32, and a foam layer 16 is formed between the first upper embankment deck 32 and the abutment 52. The modified lightweight embankment structure 30 differs from the embodiment in the configuration of the upper embankment deck, but other configurations and manufacturing methods are the same as those of the embodiment, so that the same reference numerals as those of the embodiment are used for configurations having the same functions, and the description thereof is omitted. The modified lightweight embankment structure 30 also has the same effect as the embodiment. In the modified lightweight embankment structure 30, even if the first upper embankment deck 32 shakes horizontally due to an earthquake, the foam layer 16 can cushion the vibration of the first upper embankment deck 32, and collision between the first upper embankment deck 32 and the abutment 52 can be avoided. According to the modified lightweight embankment structure 30, the first upper embankment deck 32 is unlikely to vibrate even in the event of an earthquake, so that the foam block 14 can be prevented from shifting or gaps can be prevented from occurring around the foam block 14 during an earthquake. Therefore, the outflow of soil covering the upper side of the block layer 12 can be suppressed, and the subsidence of the surface layer of the lightweight embankment structure 30 can be prevented.

[0029] (2) In the embodiment, a bridge is given as an example of a structure, but the structure is not limited to this and may be a retaining wall, a revetment, or the like. (3) In the examples, the entire block layer was formed and then the foam layer was formed. However, this is not limited to the above. The block layer and the foam layer may be formed by stacking the foam blocks to a certain height and then partially forming the foam layer up to the stacked height of the foam blocks. (4) In the embodiment, two embankment decks, an upper one and a middle one, are provided, but this is not limited to this, and it is also possible to have only an upper embankment deck, or to have two or more middle embankment decks. [Explanation of symbols]

[0030] 10 Lightweight embankment structure, 12 Block layer, 14 Foam block, 16 Foam layer, 18 Middle embankment slab, 20 Upper embankment slab, 22 Skin layer

Claims

1. a block layer consisting of a plurality of foam blocks stacked on the side of the structure; a foam layer formed between the structure and the block layer, A lightweight embankment structure, wherein the foam layer includes a skin layer formed along the block layer.

2. A floor slab is provided on the foam block, The lightweight embankment structure according to claim 1 , wherein the foam layer is formed between the structure and the deck.

3. 3. The lightweight embankment structure according to claim 2, further comprising a deck provided on the foam layer and separate from the deck provided on the foam block.

4. A step of forming a foam skin layer along a block layer formed by stacking a plurality of foam blocks on a side of a structure by spraying a foam material onto a surface of the block layer facing the structure; A method for manufacturing a lightweight embankment structure, comprising a step of forming a foamed layer including the skin layer between the structure and the block layer by foaming a foam material between the structure and the skin layer.

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