Revetment structure

Abstract

To provide a revetment structure capable of easily reducing affection by a rise of a river and stably greening a sloped face of a river.SOLUTION: A revetment structure includes a plurality of non-woven fabrics 4, 5 integrally laminated so as to have a plurality of small rooms 3 partitioned in a plane direction. A net-like member 2 having higher strength than the non-woven fabrics 4, 5 and having flexibility and corrosion resistance is disposed on a vegetation mat 1 in which at least one kind 6 of a seed, a base material, and a fertilizer is stored in the small room 3. The non-woven fabrics 4, 5 have a leakage depression effect of the stored object in the small room 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a revetment structure suitable for use in, for example, a vegetated revetment of a river embankment or the like. [Background technology]

[0002] One method is to lay vegetation mats on the slopes of river embankments during periods when the river water level does not rise much (non-flood season), to create a bank protection structure and encourage vegetation to grow.This will prevent the collapse of the embankment during periods when the water level is more likely to rise (flood season), thanks to the plants that are already growing on the slopes and the vegetation mats that have already been laid.

[0003] As a means of constructing such a revetment structure, the applicant has already proposed a vegetation mat in which the edges of an at least partially dissolvable top sheet and a water-soluble back sheet are sewn together to form a bag, and with vegetation material loaded inside the bag, the surfaces of the top sheet and the back sheet are sewn together in a predetermined direction at multiple intermediate points with large meshes, thereby containing the vegetation material within the bag so that it cannot move, and further comprising a first net with a small mesh made of corrosive fibers and a second net with a large mesh made of corrosion-resistant fibers on the surface side (Patent Document 1,

[0016] ).

[0004] In this type of vegetation mat, the back sheet decomposes due to rainwater, etc., so that the vegetation material adheres tightly to the slope, effectively preventing gaps from forming between the vegetation material and the slope. Furthermore, even if the top sheet decomposes due to rainwater, etc., the first net can prevent the vegetation material from being washed away, and because the first net is made of a corrosive fiber, it can be assimilated with the soil by the time the plant seeds grow large.

[0005] Furthermore, a second net made of corrosion-resistant fibers with large mesh sizes that will not get tangled in the plant trunks as the plants grow is attached to the outer surface of the first net, so that the net can ensure that the entire vegetation mat is securely laid on the slope while preventing the slope from collapsing.Furthermore, when trees and other plants grow and their trunks become large, the second net will not get tangled in the trunks and hinder their growth, allowing the trees and other plants to grow well and reliably green the slope. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-146291 Summary of the Invention [Problem to be solved by the invention]

[0007] In Japan, the flood season generally occurs from June to October, which is the rainy season through to the typhoon season. The period when plants (such as grass) take root (around April to May) and the flood season hardly overlap, so the impact of flooding on vegetation before it takes root is usually small.

[0008] However, in areas with heavy snowfall (Hokkaido and parts of Tohoku), the period when rivers flood due to melting snow (around April to May) overlaps with the period when plants take root (around April to May), and there is a problem in that the flooding of rivers makes it difficult to achieve stable greening of river slopes.

[0009] The present invention has been made with the above-mentioned points in mind, and its object is to provide a bank protection structure that reduces the impact of rising river water levels and facilitates stable greening of river slopes. [Means for solving the problem]

[0010] In order to achieve the above object, the revetment structure of the present invention is a revetment structure constructed on a slope, and has a plurality of nonwoven fabrics laminated and integrated to form a plurality of small compartments partitioned in the surface direction, and a vegetation mat containing at least one of seeds, base material, and fertilizer in the small compartments, on which a mesh member having higher strength than the nonwoven fabric and having flexibility and corrosion resistance is placed, the small compartments having a dimension of 5 to 20 cm and a roughly diamond shape in a plan view, and two diagonals of this diamond are oriented in the longitudinal and lateral directions of the rectangular vegetation mat, respectively, and are oriented along the contour lines and in a direction perpendicular thereto, the mesh member has a lattice pattern with a mesh size of 5 to 25 mm and has a tensile strength of 0.5 to 4.0 tons per meter of width. The vegetation mat has, as the plurality of nonwoven fabrics, an upper nonwoven fabric positioned above the contents of the small compartment when the vegetation mat is laid on a slope, and a lower nonwoven fabric positioned below, and the upper nonwoven fabric is thinner, has a smaller basis weight, a larger coefficient of water permeability, and has a higher tensile strength than the lower nonwoven fabric. (Claim 1).

[0011] In the above-mentioned bank protection structure, the nonwoven fabric may have an effect of preventing leakage of contents stored in the small compartment (claim 2).

[0012] In the above-mentioned bank protection structure, the small chamber may contain poorly water-soluble fertilizer (claim 3).

[0013] In the above-mentioned bank protection structure, the nonwoven fabric may have a suction prevention effect (claim 4).

[0014] [Effects of the Invention]

[0015] The present invention provides a bank protection structure that can reduce the effects of rising river water levels and facilitate stable greening of river slopes.

[0016] That is, in the bank protection structure of the invention according to each claim of the present application, seeds, etc. are stored and held in small chambers of the vegetation mat, and if the components of the chambers are designed so that they do not immediately decompose when they come into contact with water and are impervious to seeds, etc., the seeds, etc. in the chambers can be prevented from being washed away even if the vegetation mat is submerged by rising river waters. Therefore, by providing the vegetation mat with the strength and structure that does not hinder the germination and root growth of vegetation seeds (seeds stored in the small chambers, seeds buried in the area where the vegetation mat is laid, seeds that are thought to fly onto the vegetation mat after it is laid, etc.), it is expected that the growth of vegetation seeds will be promoted after the water level of the river drops.

[0017] Furthermore, by storing seeds etc. in a number of small rooms, even if one of the rooms is damaged, only the seeds etc. stored in that room are at risk of being washed away from the damaged area, which also increases the reliability of greening the river slope.

[0018] The bank protection structure of the invention according to claim 2 can reliably prevent seeds and the like from being washed away in the small chambers when the vegetation mat is submerged.

[0019] In the bank protection structure of the invention according to claim 3, even if the vegetation mat is submerged, the growth of vegetation seeds can be promoted by the use of poorly water-soluble fertilizer after the river water level drops.

[0020] In the bank protection structure of the invention of claim 4, the nonwoven fabric prevents soil from being sucked out from the back of the vegetation mat, providing stronger protection for the river embankment during floods, thereby contributing to the formation of a strong river bank and making it less likely that the growth of the target plants will be reduced.

[0021] In the revetment structure of the invention of claim 1, the two diagonals of the diamond shape of the small chamber are oriented along the contour lines and perpendicular to these lines, respectively, thereby efficiently dispersing water that flows along the vegetation mat in the direction of the contour lines and water that flows perpendicular to the contour lines when submerged, and more reliably preventing seeds, etc. in the small chamber from being washed away and soil and sand from the slope from being sucked away by the water flow. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is an exploded perspective view showing a schematic configuration of a revetment structure according to an embodiment of the present invention. [Figure 2] (A) is a plan view of a portion of the revetment structure (one end in the longitudinal direction), (B) is a plan view of a portion of the revetment structure with the topmost mesh member removed, and (C) is a plan view of a portion of the mesh member. [Figure 3] 1A is a bottom view of a portion of the revetment structure, and FIG. 1B is a plan view of a portion of the protective net of the revetment structure. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of the present invention will be described below.

[0024] The revetment structures shown in Figures 1, 2(A), and 3(A) are constructed, for example, on the slope of a river embankment, and comprise a vegetation mat 1 and a mesh member 2 (in this example, a geogrid, a type of geotextile) that is superimposed on the vegetation mat 1 and has higher strength, flexibility, and corrosion resistance than the vegetation mat 1. Note that Figure 2(A) shows the state in which the mesh member 2 shown in Figure 2(C) is placed on top of the vegetation mat 1 shown in Figure 2(B).

[0025] The vegetation mat 1 has a rectangular shape, for example, with a width of approximately 1 m and a length of approximately 10 m, and is laid on the slope with its longitudinal direction (vertical direction) facing from the top of the slope to the bottom of the slope.As shown in Figures 2(B) and 3(A), it has multiple (two in this example) nonwoven fabrics 4, 5 that are laminated together to form multiple small compartments 3 (see Figure 2(B)) divided in the surface direction (direction perpendicular to the thickness direction) (see Figure 1), and each small compartment 3 contains vegetation material 6 (at least one of seeds, substrate, and fertilizer), and is configured so that the vegetation material 6 in the small compartment 3 does not flow out into other small compartments 3 or to the outside.

[0026] The small chambers 3 are divided by a sewing member (e.g., monofilament) 7 that stitches together the nonwoven fabrics 4, 5, etc., and in this example, each small chamber 3 is configured to have a roughly diamond shape in a plan view. More specifically, as shown in Figure 2(B), the ends of each small chamber 3 overlap with the small chamber 3 adjacent in the horizontal (short) direction (left and right), that is, there are overlapping portions 3a on the left and right, and each small chamber 3 does not overlap with the small chamber 3 adjacent in the vertical (longitudinal) direction, and there is an overlapping portion 3a between two small chambers 3 lined up vertically.

[0027] If each small chamber 3 is too large, the plant material 6 stored therein will tend to become uneven, and if it is too small, it will be unsuitable for storing plant material 6, so it is preferable that the small chambers 3 have dimensions of, for example, approximately 5 to 20 cm in length and width.

[0028] Furthermore, as shown in Figure 2(B), the periphery of the vegetation mat 1 is sewn in a straight line using stitching material 7, and the small chambers 3 near the periphery of the vegetation mat 1 have a diamond shape with part of it cut out.However, from the standpoint of promoting greening, it is preferable to store vegetation material 6 in such small chambers 3 if possible.

[0029] Of the two nonwoven fabrics 4, 5, the upper nonwoven fabric 4, which is located above the vegetative material 6 when the vegetative mat 1 is laid on a slope, is primarily required to have the effect of preventing leakage of the contents (vegetative material 6) contained in the small compartments 3, while the lower nonwoven fabric 5, which is located below the vegetative material 6 when the vegetative mat 1 is laid on a slope, is required to have the effect of preventing leakage of the contents (vegetative material 6) contained in the small compartments 3 and the effect of preventing soil from being sucked out from the back side of the vegetative mat 1. The leakage prevention effect can reliably prevent the vegetative material 6 from being washed away in the small compartments 3 when the vegetative mat 1 is submerged, and the sucking prevention effect prevents soil from being sucked out from the back side of the vegetative mat 1, thereby providing stronger protection for the river slope during floods, contributing to the formation of a strong riverbank and also making it less likely that the growth of target plants will be reduced.

[0030] If the upper nonwoven fabric 4 is less permeable to water than the lower nonwoven fabric 5, the water flow that has entered the back side of the vegetation mat 1 or the small room 3 when the vegetation mat 1 is submerged will tend to lift the upper nonwoven fabric 4 from the slope, which may in turn cause the vegetation mat 1 to easily peel off from the slope. Therefore, it is preferable that the hydraulic conductivity of the upper nonwoven fabric 4 is greater than that of the lower nonwoven fabric 5. In this example, the hydraulic conductivity of the upper nonwoven fabric 4 is set to 3.3 × 10 -2 cm / s, and the hydraulic conductivity of the lower nonwoven fabric 5 is 3.1 × 10 -3 It is expressed as cm / s.

[0031] In order to set the magnitude of the hydraulic conductivity in this way, it is advantageous to make the upper nonwoven fabric 4 thinner than the lower nonwoven fabric 5 and to make the basis weight smaller. In this example, the thickness of the upper nonwoven fabric 4 is 0.5 mm and the basis weight is 30 g / m 2 The thickness of the lower nonwoven fabric 5 is 2.5 mm, and the basis weight is 140 g / m 2 It is stated as such.

[0032] Furthermore, by making the upper nonwoven fabric 4 have a higher tensile strength than the lower nonwoven fabric 5, even if the lower nonwoven fabric 5 is damaged, it is possible to easily maintain the effect of suppressing the loss of vegetative materials 6 in the small room 3 and the suction of soil from the slope. In this example, the tensile strength of the upper nonwoven fabric 4 is 41.8 to 58.2 N / 5 cm, and the tensile strength of the lower nonwoven fabric 5 is 39.2 N / 5 cm.

[0033] The revetment structure (vegetation mat 1) in this example is not limited to specific species (target species) but is intended for active greening, utilizing buried seeds and airborne seeds as well. From the perspective of making it difficult to hinder the germination and rooting of vegetation seeds (seeds stored in small chamber 3, buried seeds in the area where vegetation mat 1 is laid, seeds that are likely to fly to vegetation mat 1 after laying, etc.), it is preferable that both nonwoven fabrics 4 and 5 be made of short-fiber nonwoven fabric (e.g., polyester). In particular, it is best to avoid using a long-fiber nonwoven fabric for the upper nonwoven fabric 4, which has high tensile strength, as this could significantly impede the germination and rooting of vegetation seeds. Similarly, it is best to avoid using a long-fiber nonwoven fabric for the lower nonwoven fabric 5, as this could hinder the germination and growth of buried seeds.

[0034] As shown in Fig. 1, the vegetation mat 1 has a pair of holding sheets 8 that sandwich the vegetation material 6 from above and below between the upper and lower nonwoven fabrics 4 and 5. The holding sheets 8 are intended to prevent the vegetation material 6 from leaking through the mesh of the upper and lower nonwoven fabrics 4 and 5 when the vegetation mat 1 is being transported, and it is desirable that the holding sheets 8 have water permeability, a mesh size smaller than that of the nonwoven fabrics 4 and 5, and tensile strength that does not hinder the germination and rooting of vegetation seeds. The holding sheets 8 in this example are made of vegetable fiber (with a basis weight of 13 g / m 2 ) crepe paper is used.

[0035] Furthermore, as shown in Figure 1, a protective net 9 having a higher tensile strength than the upper nonwoven fabric 4 and an expandable mesh size is provided on the upper surface of the upper nonwoven fabric 4, so that the vegetation mat 1 laid on the slope is less likely to be damaged even if workers walk on it. The protective net 9 in this example is a raschel-knit polyethylene net (basis weight 53.3 g / m 2 , mesh size 11mm x 5mm) (see Figure 3(B)).

[0036] On the other hand, the mesh member 2 is a geotextile net (geogrid) made of durable fibers such as nylon, polyester, aramid, carbon, glass, polyacetal, etc., molded into a grid pattern (see Figures 1 and 2(C)) with a mesh size of about 5 to 25 mm (preferably 5 to 10 mm). However, filaments made of the above fibers may also be braided into a mesh pattern with a similar mesh size as above, or both of these (a grid pattern and a mesh pattern) may be overlapped, and the tensile strength per meter of width is set to about 0.5 to 4.0 tons. This is strong enough to withstand the fluid force of water flowing in a river at a flow rate of up to 5.0 m / s. Furthermore, the mesh member 2 has a tensile strength of about 0.5 to 4.0 tons per meter. 2 Each one weighs 200-250g, making it relatively light.

[0037] As shown in Figure 1, the vegetation mat 1 in this example is made by stacking, from the bottom, a lower nonwoven fabric 5, a retaining sheet 8, vegetation material 6, a retaining sheet 8, an upper nonwoven fabric 4, and a protective net 9, in that order, and sewing these together with a stitching member 7 so that the vegetation material 6 is contained within a small chamber 3 partitioned by the stitching member 7.

[0038] In contrast, the mesh member 2 is separate from the vegetation mat 1 and is placed on top of the vegetation mat 1 laid on the slope on site. In this state, appropriate fixing devices such as anchor pins that penetrate both the vegetation mat 1 and the mesh member 2 are driven in, integrating the two and fixing them to the slope to construct a revetment structure.

[0039] However, this is not limited to this, and for example, only the vegetation mat 1 may be fixed to the slope with a fixing device such as an anchor pin, and the mesh member 2 may be connected to this vegetation mat 1 with an appropriate connecting device, or the vegetation mat 1 and the mesh member 2 may be integrated from the beginning using an appropriate joining means such as sewing or adhesive.

[0040] In the bank protection structure of this example constructed as described above, the vegetative material 6 is stored and held in the small chambers 3 of the vegetative mat 1, and the components of the small chambers 3 (nonwoven fabrics 4, 5, retaining sheet 8) are designed so that they do not immediately decompose when they come into contact with water and are impervious to the vegetative material 6, so even if the vegetative mat 1 is submerged due to rising river water levels, the vegetative material 6 in the small chambers 3 is prevented from being washed away. In addition, since the vegetative mat 1 has the strength and structure to not hinder the germination and root growth of vegetative seeds, it is expected that the growth of vegetative seeds will be promoted after the water level of the river drops.

[0041] Furthermore, by storing the vegetation materials 6 in a plurality of small rooms 3, even if some of the small rooms 3 are damaged, only the vegetation materials 6 stored in those small rooms 3 are at risk of being washed away from the damaged area, which also increases the reliability of greening the river slope.

[0042] Furthermore, each small chamber 3 of the vegetation mat 1 is designed to have an approximately diamond shape when viewed from above, and the two diagonals of the diamond of the small chamber 3 are oriented along the contour lines (the direction in which the river flows) and perpendicular to this, respectively.This effectively disperses water flowing along the vegetation mat 1 in the direction of the contour lines and water flowing perpendicular to this when submerged, and more reliably prevents the vegetation material 6 in the small chambers 3 from being washed away and the soil and sand on the slope from being sucked away by the water flow.

[0043] Here, if the vegetation material 6 stored in the small room of the vegetation mat 1 contains fertilizer, by making this fertilizer a poorly water-soluble fertilizer (a fertilizer that is neither organic fertilizer nor an immediate-acting fertilizer), even if the vegetation mat 1 is submerged, the poorly water-soluble fertilizer can promote the growth of vegetation seeds after the water level of the river drops.

[0044] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications can be mentioned.

[0045] In the above embodiment, the vegetation mat 1 has a pair of upper and lower retaining sheets 8 to prevent the vegetation material 6 from leaking through the mesh of the upper and lower nonwoven fabrics 4, 5 when the vegetation mat 1 is being transported, etc. However, if the vegetation material 6 does not leak through the mesh of the nonwoven fabrics 4, 5 or if the amount of leakage is limited, the retaining sheets 8 may be omitted.

[0046] In the above embodiment, a geogrid is used for the mesh member 2, but the present invention is not limited to this, and for example, a wire mesh may be used for the mesh member 2.

[0047] It goes without saying that the modifications given in this specification may be combined as appropriate. [Explanation of symbols]

[0048] 1 vegetation mat 2. Mesh members 3 Small Room 3a Overlapped part 4 Upper nonwoven fabric 5 Lower non-woven fabric 6. Vegetation materials 7 Suture material 8 Retaining Sheet 9 Protective Net

Claims

1. A revetment structure constructed on a slope, The vegetation mat has a plurality of nonwoven fabrics laminated together to form a plurality of small compartments partitioned in the surface direction, and at least one of seeds, a substrate, and fertilizer is accommodated in the small compartments. A mesh member having higher strength, flexibility, and corrosion resistance than the nonwoven fabrics is placed on the vegetation mat. The small chamber has a generally rhombus shape in plan view with dimensions of 5 to 20 cm, and the two diagonals of the rhombus are oriented in the longitudinal and lateral directions of the rectangular vegetation mat, respectively, and are oriented along the contour lines and in a direction perpendicular thereto; The mesh member has a lattice shape with a mesh size of 5 to 25 mm and a tensile strength of 0.5 to 4.0 tons per meter of width. The vegetation mat has, as the multiple nonwoven fabrics, an upper nonwoven fabric that is positioned above the contents of the small room when the vegetation mat is laid on a slope, and a lower nonwoven fabric that is positioned below, and the upper nonwoven fabric is thinner, has a smaller basis weight, a higher permeability coefficient, and has higher tensile strength than the lower nonwoven fabric.

2. The bank protection structure according to claim 1, wherein the nonwoven fabric has an effect of preventing leakage of contents stored in the small compartment.

3. 3. The revetment structure according to claim 1, wherein said small chamber contains a poorly water-soluble fertilizer.

4. The revetment structure according to any one of claims 1 to 3, wherein the nonwoven fabric has a suction prevention effect.

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