Reinforcement structures for the slopes behind levees and methods for reinforcing the slopes behind levees

Abstract

To provide a levee back slope reinforcement structure that can more reliably prevent levee breaches or extend the time until a levee breach occurs by preventing overflow water from flowing around to the back of the molded structure. [Solution] The levee back slope reinforcement structure is a levee back slope reinforcement structure that protects the inland slope of the levee from overflow, and is characterized in that a molded structure is laid from the levee back slope to the toe of the levee back slope, and the molded structure is made of a cloth formwork having a bag body made of a two-layer woven fabric consisting of an upper layer cloth and a lower layer cloth, in which mortar or concrete is filled and hardened, and the upper end of the molded structure is embedded into the levee body at the top of the levee.

Description

[Technical Field]

[0001] This invention relates to a structure for reinforcing the slope behind an embankment and a method for reinforcing the slope behind an embankment. [Background technology]

[0002] In recent years, heavy rain disasters have become more severe and frequent due to climate change, and there is a need to prevent and mitigate the damage. In particular, river levees are collapsing due to flooding, and one of the causes is overtopping. Therefore, there is a need for "resilient river levees" that can withstand overtopping.

[0003] Traditionally, riverbank protection methods involved, for example, leveling and compacting the soil surface to be protected on the back slope of the inner side of the levee, laying a filter, then piling up rubble stones, and finally attaching concrete blocks to the top surface while applying cement mortar to the joints.

[0004] However, in the case of the above structure, when water overflows the embankment during a large-scale flood, there are cases in which the slope protection work is destroyed or washed away. For example, as shown in Figure 16, (1) the water flow destroys the embankment due to the action of overflowing water and incoming waves (coast), (2) the covering work on the back slope is washed away as the water flow becomes high speed in the super-flow zone of the back slope, and (3) further, the crest protection work is washed away and the soil of the embankment body is washed away through the gaps in the protection work, which may lead to the collapse of the embankment.

[0005] The solution would be to set the height of the levees to a level that prevents them from overtopping even in the event of a major flood. However, in reality, this is often impossible due to various problems such as land availability, technical issues, and aesthetic concerns. Therefore, in practice, methods of reinforcing levees are being attempted with the aim of preventing the collapse of levees due to overtopping, as described above.

[0006] Therefore, a structure is needed that prevents the back slope covering from being washed away even if overtopping occurs on the river embankment. At the same time, it is necessary that the embankment slope is not eroded by the overflowing water, and that the predetermined embankment crest height is maintained even if overtopping occurs with an overflow depth of 30 cm and an overflow duration of 3 hours.

[0007] Furthermore, as a method for reinforcing embankments, for example, a method of reinforcing the toe of the embankment's back slope with blocks is known (see Patent Document 1 and Non-Patent Document 1).

[0008] This construction method slows down erosion by reinforcing the toe of the embankment's back slope with blocks, extending the time before the embankment breaks. This allows for sufficient lead time for evacuation. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2018-184722 [Non-patent literature]

[0010] [Non-Patent Document 1] National Institute for Land and Infrastructure Management Document No. 911 (May 2016) [Overview of the project] [Problems that the invention aims to solve]

[0011] However, in the case of concrete blocks, the weight of the concrete blocks tends to be large in order to resist the fluid forces acting when water overtops. When constructing concrete block coverings, large heavy machinery such as cranes must be used, and it is necessary to secure access routes and scaffolding for the heavy machinery. Concrete blocks and erosion prevention materials have low water-blocking effect, and seepage water from overflow may seep into the back slope, potentially loosening the slope behind the covering. When covering the concrete blocks with backfill soil, rainwater may run along the interface between the concrete blocks and the backfill soil, potentially causing the backfill soil to wash away. In addition, the landward side of the drainage work must be covered with a material that has a filter function in order to properly drain seepage water from within the embankment.

[0012] Thus, despite the high importance of countermeasures against overflow failure, effective measures remain insufficient. If overflow continues, the levee will eventually break. For disaster prevention and mitigation, it is extremely important to consider how long the levee's function can be maintained and what measures can be taken to maintain the levee's function for an extended period, when considering the levee's resistance to overflow.

[0013] This invention was proposed in view of the above-mentioned conventional circumstances, and the object of this invention is to provide a levee back slope reinforcement structure and a levee back slope reinforcement method that can more reliably prevent levee failure or extend the time until levee failure by preventing overflow water from flowing around to the back of the molded structure. [Means for solving the problem]

[0014] The inventors of this invention have concluded that the above problem can be solved by using a fabric formwork instead of concrete blocks, and have completed this invention. That is, the present invention is as follows. [1] A reinforcing structure for the inner slope of a levee, which protects the inner slope of the levee from overflow, is constructed by laying a molded structure from the inner slope of the levee to the toe of the inner slope. The formed structure body is formed by filling and solidifying mortar or concrete inside a cloth formwork having a bag body made of a two-layer fabric of an upper layer cloth and a lower layer cloth. A dike back slope reinforcement structure, characterized in that the upper end portion of the formed structure body is embedded inside the dike body at the dike top end portion. [2] The dike back slope reinforcement structure according to [1], wherein a breathable waterproof sheet is arranged between the back slope and the formed structure body. [3] The cloth formwork includes a bag body made of a two-layer fabric of an upper layer cloth and a lower layer cloth, a first part arranged on the back slope part of the dike body and having a plurality of mesh parts made of a single-layer fabric formed in an island shape at a predetermined interval inside the bag body, a second part arranged in contact with a drain work provided at the dike heel part and having a plurality of filter parts made of a single-layer fabric formed in an island shape at a predetermined interval inside the bag body, and is provided with The dike back slope reinforcement structure according to [1] or [2], wherein the first part and the second part are integrated. [4] A dike back slope reinforcement construction method for protecting the inner dike side slope against overtopping, comprising the following steps: (1) A step of laying a cloth formwork having a bag body made of a two-layer fabric of an upper layer cloth and a lower layer cloth on the back slope; (2) A step of placing mortar or concrete inside the bag body of the cloth formwork to form a formed structure body; (3) A step of embedding the upper end portion of the formed structure body inside the dike body at the dike top end portion. The dike back slope reinforcement construction method is characterized by having the above steps. [5] The dike back slope reinforcement construction method according to [4], wherein a breathable waterproof sheet is arranged between the back slope and the formed structure body in the step (1). [6] The cloth formwork includes a bag body made of a two-layer fabric of an upper layer cloth and a lower layer cloth, a first part having a plurality of mesh parts made of a single-layer fabric formed in an island shape at a predetermined interval inside the bag body, A second part having a plurality of filter parts made of a single-layer fabric formed in an island shape at predetermined intervals inside the bag body; The first part and the second part are integrated; In the step (1), the first part is arranged on the back slope surface part of the embankment body, and the second part is arranged in contact with the drain work provided on the slope crest part of the embankment body. The embankment back slope reinforcement method according to [4] or [5].

Advantages of the Invention

[0015] According to the present invention, by preventing the overflow water from flowing around to the back of the formed structure, it is possible to provide a more reliable embankment back slope reinforcement structure and an embankment back slope reinforcement method that can prevent embankment breakage or extend the time until embankment breakage.

Brief Description of the Drawings

[0016] [Figure 1] It is a view showing an example of the embankment back slope reinforcement structure of the present invention. [Figure 2] It is a view for explaining the structure of the breathable waterproof sheet. [Figure 3] It is a plan view showing a configuration example of the cloth formwork. [Figure 4] It is a cross-sectional view of the formed structure after placing the filling material inside the cloth formwork. [Figure 5] It is a cross-sectional view showing an example of an intermediate body of a long fiber-reinforced synthetic resin linear material. [Figure 6] It is a view showing a part of the coated knotless net that becomes the surface constituent material of the cage mat body. [Figure 7] It is a view showing an example of a cage mat using a mesh body as a surface constituent material. [Figure 8] It is a view showing the large-scale embankment model experimental water channel of the National Institute of Land and Infrastructure Management used in the example. [Figure 9] It is a view showing the particle size distribution of the embankment body material used for the embankment body model. [Figure 10] It is a view showing the compaction curve of the embankment body material used for the embankment body model. [Figure 11] This photograph shows the state of a fabric formwork laid out on a slope. [Figure 12] This is a photograph showing the situation during the overflow experiment (before the overflow). [Figure 13] This is a photograph showing the overflow experiment in progress. [Figure 14] This is a photograph showing the situation after the water overflow experiment. [Figure 15] This figure shows the water level measurements for each part every hour. [Figure 16] This is a schematic diagram illustrating the mechanism of levee failure due to the protection work on the slope behind the levee. [Modes for carrying out the invention]

[0017] The following describes in detail an exemplary embodiment of the present invention (hereinafter abbreviated as "this embodiment"). The present invention is not limited to this embodiment and can be implemented in various modifications within the scope of its gist. In this specification, the upper and lower limits of each numerical range can be arbitrarily combined.

[0018] [Reinforcement structure for the slope behind the embankment] First, let me explain the embankment slope reinforcement structure of the present invention. Figure 1 shows an example of the embankment slope reinforcement structure according to the present invention.

[0019] This levee back slope reinforcement structure 100 is a levee back slope reinforcement structure that protects the inner slope of the levee from river overflow, and consists of a molded structure 40 laid from the levee back slope to the toe of the levee back slope.

[0020] Note that "inside the embankment" refers to the urban area side (the side behind the river), and "outside the embankment" refers to the river side (the side facing the river).

[0021] The molded structure 40 is formed by filling a fabric formwork 41, which has a bag-like body 42 made of a two-layer woven fabric 45 consisting of an upper layer fabric 43 and a lower layer fabric 44, with a filler material 50 such as mortar or concrete, which is then solidified inside the formwork. The upper end of the molded structure 40 is embedded into the interior of the dam body at the top of the dam 14.

[0022] This levee back slope reinforcement structure 100 prevents overflowing water from flowing around to the back of the molded structure 40, thereby more reliably preventing levee breaches or extending the time until a breach occurs. As a result, it is possible to construct a "resilient river levee" that is resistant to overflows.

[0023] As shown in Figure 1, the dam body includes an embankment 10 and a reinforcement structure 100 for the slope behind the dam.

[0024] The embankment fill 10 is composed of a highly permeable fill material. The permeability coefficient of the fill material is, for example, 1.0 × 10⁻⁶. -7 ~10 -4 It is cm / sec.

[0025] A drainage section is formed at the toe of the slope, which is the lower end of the back slope 11 located opposite the river side of the embankment 10. The drainage section is composed of a drainage structure 20. The drainage structure 20 is made of a material with higher permeability than the embankment material of each layer of the embankment 10, so that water that has seeped into the embankment 10 is collected.

[0026] A pier channel (not shown) may be provided to guide the water collected in the drain structure 20 to a predetermined outlet. The pier channel ensures that the water collected in the drain structure 20 is reliably drained.

[0027] A waterproof sheet 21 may be laid on the surface slope 12 of the dam body. This prevents river water from seeping into the dam body.

[0028] Furthermore, at the top of the dam body, the crest 14, a slope protection structure 22 made of concrete blocks or the like is provided on the slope shoulder.

[0029] In the levee back slope reinforcement structure 100, a breathable waterproof sheet 30 and a molded structure 40 are arranged in order from the side adjacent to the inner slope (back slope) 11 of the levee body embankment 10.

[0030] Furthermore, in the embankment back slope reinforcement structure 100 of the present invention, the upper end of the molded structure 40 is embedded inside the embankment body at the top of the embankment 14. For example, in the example shown in Figure 1, the upper end of the molded structure 40 is shown inserted below the slope shoulder protection work 22, but the upper end of the molded structure 40 may also be embedded in the embankment soil 10.

[0031] This prevents overflowing water from flowing around to the back of the molded structure 40 and also provides stability against centrifugal force (negative pressure) generated by overflowing water near the slope shoulder.

[0032] Furthermore, by placing a breathable waterproof sheet (waterproof sheet) 30 between the slope and the molded structure 40, seepage from the joints of the molded structure 40 (cloth formwork 41) and infiltration of overflow water into the embankment are prevented.

[0033] Furthermore, when a breathable waterproof sheet 30 is placed between the slope and the molded structure 40, it is preferable that the upper end of the breathable waterproof sheet 30 is also embedded in the embankment along with the molded structure 40.

[0034] The levee back slope reinforcement structure 100, constructed as described above, has the upper part of the molded structure 40 using a cloth formwork 41 embedded within the levee body. This allows the frictional force between the air permeable waterproof sheet 30 and the levee body soil, as well as the tensile force of the air permeable waterproof sheet 30, to be added to the scouring force acting on the molded structure 40. As a result, it offers improved resistance to scouring forces compared to conventional block mats, and also reinforces the levee body embankment.

[0035] In this embodiment, when water overflows, the uneven curved surface on the upper surface of the molded structure 40 reduces the flow velocity, thereby suppressing the progression of erosion at the toe of the embankment.

[0036] Since the molded structure 40 using the cloth formwork 41 has a plate structure, it can resist fluid pressure on the surface, so it has an advantage in terms of structure compared to concrete blocks. In addition, the cloth formwork 41 does not require special heavy machinery for laying, can cover a large area at once, and is excellent in workability.

[0037] In addition, on the uppermost part of the embankment body, materials other than embankment fill may be piled up in order to pave with asphalt or concrete for management roads, etc. or to construct other structures.

[0038] <Breathable waterproof sheet> The breathable waterproof sheet used for the back slope reinforcement structure 100 of the embankment will be described.

[0039] The breathable waterproof sheet 30 is composed of a fibrous sheet having the property of allowing air to pass through but difficult for water to pass through. The breathable waterproof sheet 30 has, for example, a breathability of 220 m 3 / m 2 / 24h to 1200 m 3 / m 2 / 24h and a water permeability coefficient of 7.7×10 -9 cm / sec to 8.6×10 -5 cm / sec. For example, the breathability of the breathable waterproof sheet 30 is 220 m 3 / m 2 / 24h and a water permeability coefficient of 8.6×10 -9 cm / sec. When the breathable waterproof sheet 30 with such a water permeability coefficient is used, it is possible to ensure the degree of water tightness required for the embankment body. By using the breathable waterproof sheet 30, the variation in the water permeability coefficient of the back slope surface 11 of the embankment fill 10 can be eliminated, and the waterproof performance originally required for the back slope surface 11 can be ensured.

[0040] Since this breathable waterproof sheet 30 has the property of allowing air to pass through easily, even when a gap is formed between it and the back slope surface 11, air can escape from the gap and quickly fill the gap. Since the gap is filled, the risk of damage to the breathable waterproof sheet 30 is lower than before. In addition, since the breathable waterproof sheet 30 allows air to pass through easily, it is effective when maintaining and growing grass-like plants on the molded structure 40.

[0041] Figure 2 is a diagram illustrating the structure of the breathable waterproof sheet 30. This breathable waterproof sheet 30 has a structure in which a breathable and waterproof layer 31 is sandwiched between reinforcing layers 32 and 33. The breathable and waterproof layer 31 allows air to pass through the breathable waterproof sheet 30, while most of the water is blocked. The reinforcing layers 32 and 33 prevent deterioration and damage to the breathable and waterproof layer 31 due to external factors.

[0042] The breathable and waterproof layer 31 is made of, for example, a polyethylene continuous ultrafine fiber nonwoven fabric having a pore diameter of approximately 0.5 μm, and the reinforcing layers 32 and 33 are made of, for example, a nonwoven fabric. The diameter of a water droplet is usually 1000 to 3000 μm, and the diameter of drizzle is usually 100 to 200 μm. If the pore diameter of the breathable and waterproof layer 31 of the breathable and waterproof sheet 30 is the above value, the diameter of water droplets, drizzle, etc., are larger than the pore diameter of the breathable and waterproof layer 31, so they will not pass through the breathable and waterproof layer 31. For this reason, the breathable and waterproof sheet 30 will be waterproof. Also, the diameter of water vapor is usually 0.004 μm, and the diameter of carbon dioxide is usually 0.0023 μm. Since these diameters are smaller than the pore diameter of the breathable and waterproof layer 31, they will pass through the breathable and waterproof layer 31. For this reason, the breathable and waterproof sheet 30 will be breathable.

[0043] <Fabric formwork> This section describes the fabric formwork used in the reinforcement structure 100 for the embankment's inner slope. Figure 3 is a plan view showing an example of a fabric formwork configuration, and Figure 4 is a cross-sectional view of the molded structure after filling material has been poured into the fabric formwork.

[0044] The fabric formwork 41 comprises a bag 42 made of a two-layer woven fabric 45, a first part 41A having a mesh section 47 made of a plurality of single-layer woven fabrics 46 formed in an island-like manner at predetermined intervals inside the bag 42, and a second part 41B having a filter section 49 made of a plurality of single-layer woven fabrics 48 formed in an island-like manner at predetermined intervals inside the bag 42, with the first part 41A and the second part 41B being sewn together as a single unit.

[0045] In the following explanation, we will use the example of filling the inside of the bag 42 with mortar as the filler material 50 and allowing it to solidify, but the present invention is not limited to this, and concrete may be used as the filler material, for example.

[0046] In this fabric formwork 41, the bag body 42 consists of a two-layer fabric 45 in which multiple island-shaped filter sections 49 are formed at predetermined intervals. The two-layer fabric 45 is composed of an upper layer fabric 43 and a lower layer fabric 44, and is usually obtained by weaving in a bag weave. A filler material 50 such as mortar is poured into the gaps in the two-layer fabric 45. The fabric formwork 41 is laid with the upper layer fabric 43 side facing up (outside).

[0047] The bag body 42 is provided with an injection port (not shown), through which a filler material 50 such as mortar is poured into the void formed by the upper layer fabric 43 and the lower layer fabric 44 of the bag body 42.

[0048] This bag 42 is obtained by weaving a two-layer fabric 45 consisting of an upper layer fabric 43 and a lower layer fabric 44 using warp and weft threads, and forming multiple island-shaped single-layer fabrics 46 and multiple island-shaped single-layer fabrics 48 at predetermined intervals. Specifically, the warp and weft threads that make up the lower layer fabric 44 and the upper layer fabric 43 are partially woven as single-layer fabrics 46 to form a mesh section 47, and the warp and weft threads that make up the lower layer fabric 44 and the upper layer fabric 43 are partially woven as single-layer fabrics 48 to form a filter section 49.

[0049] There are no particular restrictions on the size, number, and arrangement of the mesh section 47 and filter section 49, and they can be selected as appropriate depending on the construction site, etc. However, a narrower spacing will result in a more planar concrete surface. For example, in Figure 1, the mesh section 47 and filter section 49 are arranged in a staggered pattern, but this is not the only option; for example, they may be arranged in a vertical or horizontal parallel pattern.

[0050] In the fabric formwork 41, the portion that is placed on the slope of the dam body is designated as a first portion 41A having a mesh portion 47, and the portion that is placed in contact with the drainage system 20 provided at the toe of the dam body is designated as a second portion 41B having a plurality of filter portions 49.

[0051] By placing the first section 41A, which has a mesh section 47, on the slope of the levee, and covering the mesh section 47 with soil and sowing seeds, roots can extend through the openings in the mesh section 47, making it possible to grow grass-like plants on the back slope 11 covered with the molded structure 40. This promotes the greening of the levee slope.

[0052] Regarding soil cover stability, the fabric formwork 41 has a mesh section 47 that acts as a pocket for trapping the soil cover, making it less prone to runoff compared to the concrete block formwork.

[0053] From the viewpoint of preventing the erosion of the embankment soil on the slope while allowing plants to extend their roots, the mesh portion 47 preferably has an opening ratio (or mesh opening) of 0.3% to 15.0%, and more preferably 4.5% to 10.0%.

[0054] Furthermore, by placing a second section 41B having a filter section 49 in contact with the drain structure 20, it becomes possible to efficiently drain seeping water from within the embankment, such as rainwater from the slope, eliminating the need for drainage functions in the embankment pier channel and slope retaining structure.

[0055] From the viewpoint of efficiently draining seepage water from within the embankment while preventing the outflow of the slope embankment soil, the filter section 49 preferably has an opening ratio (or mesh size) of, for example, 0.3% to 15.0%, and more preferably 4.5% to 10.0%.

[0056] Furthermore, in the fabric formwork 41, the first part 41A and the second part 41B are seamlessly integrated, for example, by sewing. By integrating two different types into a single structure, a more robust structure is created against the fluid forces acting during overflow. As a result, it is possible to more reliably prevent dam breaches or extend the time until a dam breach occurs.

[0057] Furthermore, during construction, the fabric formwork 41 has a mesh section 47 and a filter section 49, resulting in good drainage and improved work efficiency. In addition, the need for chipping work after construction can be reduced, thereby reducing the effort and labor costs involved.

[0058] The fabric form of the cloth formwork 41 in this embodiment is not particularly limited and may be woven, knitted, or nonwoven fabric, but from the viewpoint of mechanical strength, it is preferable that it be woven, and it is preferable that the front and back layers of the tubular weave be plain weave or diagonal weave.

[0059] There are no particular limitations on the fibrous material used for the bag 42; for example, nylon 6, nylon 66, polyamide, polyester, vinylon, polypropylene, polyvinylidene chloride, etc., can be used. Among these, polyester fibers are preferred.

[0060] Polyester fibers are extremely strong and possess the following characteristics: their strength remains unchanged even when wet; they are resistant to friction; they are wrinkle-resistant; their strength hardly changes even when exposed to sunlight; and they have almost no water absorption. By using polyester fibers to construct the fabric formwork 41, it is possible to provide a fabric formwork 41 and molded structure 40 that maintain high strength and do not tear even when exposed to wind and rain outdoors for long periods of time.

[0061] Any polyester fiber can be used, such as polyethylene terephthalate fiber and polybutylene terephthalate fiber. The polyester fiber may be either a round cross-section fiber or a non-circular cross-section fiber.

[0062] The fiber material used in the fabric mold 41 of this embodiment is preferably untwisted, but processed yarns that have undergone processing such as false twisting, bulking, crimping, or winding may be used if necessary. When mixing multiple types of fibers, there are no particular limitations on their form, and different types of fibers may be used for the warp and weft, or multiple types of fibers may be processed by false twisting or twisting as needed to make a blended yarn, or even the same type of fiber may be used, but with different thermal and mechanical properties, or with different fineness or filament counts, or a combination of long filament fibers and short filament spun yarn may be used.

[0063] Furthermore, the fibers used in the fabric formwork 41 of this embodiment may contain additives such as heat stabilizers, smoothing agents, pigments, oils, opacifiers, matting agents, flame retardants, plasticizers, and water repellents. For example, by adding a water repellent to the fibers, the water-impermeable properties of the fabric formwork 41 can be further enhanced. Examples of water repellents include fluororesin-based water repellents and silicone resin-based water repellents.

[0064] It is preferable to use yarns that exhibit nearly the same strength and elongation characteristics for both the warp and weft threads. Specifically, it is preferable to use yarns with approximately the same fineness for both the warp and weft threads. This makes it possible to ensure that the elongation deformation of the bag body 42 is approximately the same when the filler material 50 is poured into the fabric formwork 41. Generally, the fabric strength of the bag body 42 can be obtained at the pouring construction site by designing and managing the weaving process with a minimum fabric strength of 150 kg / 3 cm width.

[0065] The thickness of the yarn is selected according to the strength and thickness of the bag body 42 at the time of casting and there are no particular restrictions, but from the viewpoint of tensile strength, a total fineness of 400 to 3000 decitex (dtex) is preferred, more preferably 600 to 1500 dtex, and even more preferably 800 to 1200 dtex can be used as a multifilament. For example, a polyester multifilament yarn with a fineness of 1100 dtex / 192f can be used. Furthermore, from the viewpoint of the applicability of the water-impermeable resin, it is preferable that the warp and weft threads constituting the double fabric that makes up the bag body 42 of this embodiment have approximately the same fineness. By making the warp and weft threads approximately the same fineness, the surface irregularities of the woven fabric to which the water-impermeable resin is applied are reduced, and coating unevenness that causes a decrease in water pressure resistance can be reduced.

[0066] <Drainage work> This section describes the drainage system used in the levee back slope reinforcement structure 100. The drainage system 20 is formed by filling the inside of a basket mat 60, such as a gabion or quiver, with a filling material such as a stone block.

[0067] This basket mat 60 is formed by, for example, using an intermediate 64 of a long fiber-reinforced synthetic resin, which is made by covering the outer circumference of long fibers 61 impregnated with an uncured thermosetting resin with a solidified thermoplastic resin 63, to create a covered knotless net 65 with an arbitrary mesh size, and then using the heat-cured covered knotless net 65 as a surface component 66 to form a multifaceted three-dimensional shape.

[0068] Figure 5 shows a schematic diametrical cross-sectional view of an example of an intermediate (hereinafter referred to as "intermediate") 64 of a long fiber-reinforced synthetic resin linear material, in which long fibers impregnated with an uncured thermosetting resin are coated with a solidified thermoplastic resin on their outer circumference. Multiple long fibers 61 are impregnated with an uncured thermosetting resin 62 and further coated with a thermoplastic resin 63 to form an intermediate 64 with sufficient flexibility.

[0069] The long fibers 61 can be arbitrarily selected from synthetic fibers such as aramid fibers and polyester fibers, inorganic fibers such as glass fibers, or metal fibers, according to the specific characteristics required of the basket mat to be manufactured. The thickness and number of fibers used can also be arbitrarily selected according to the specific physical properties required of the basket mat to be manufactured, such as the breaking strength.

[0070] The uncured thermosetting resin 62 can be any resin as long as it can be easily impregnated into the long fibers 61, hardens upon heating, and has excellent physical stability after hardening. This includes thermosetting resins composed of unsaturated alkyds or epoxy acrylates, crosslinking substances such as crosslinking monomers, and polymerization initiators such as diacyl peroxides.

[0071] The thermoplastic resin 63 has sufficient flexibility to produce a mesh body consisting of a covered knotless net 65, which is the surface component of the basket mat. Any resin can be used, such as polyester resins or polyolefin resins, as long as it is not affected by crosslinking substances in the uncured thermosetting resin 62.

[0072] Figure 6 provides a simplified illustration of a portion of the covered knotless mesh 65, which forms a surface component of a multifaceted three-dimensional cage mat. The covered knotless mesh 65, manufactured using the intermediate material 64 shown in Figure 5 which has sufficient flexibility, becomes a covered knotless mesh 65 with sufficient rigidity after heat treatment following manufacturing.

[0073] Figure 7 illustrates a rectangular hexahedron cage mat 60 as an example of a cage mat using a mesh as a surface component. The covered knotless mesh 65, which is given sufficient rigidity by being manufactured and heat-treated in Figure 6, is cut to any required size to become the respective surface components 66 of the rectangular hexahedron.

[0074] Such cage mats 60 have sufficient rigidity to maintain their shape during and after construction, and do not become brittle or break due to corrosion over time, nor do they cause personal injury or environmental pollution due to corrosion. They are lightweight and have moderate flexibility to adapt to slight irregularities in the construction ground, thereby improving work efficiency. Furthermore, due to their flexibility, even with scouring after construction, the cage mats sink in accordance with the scouring within a small amount of time, preventing the gaps from widening.

[0075] [Reinforcement method for the slope behind the embankment] Next, the embankment back slope reinforcement method of the present invention, which uses such a fabric formwork 41, will be described.

[0076] The present invention provides a method for reinforcing the embankment back slope, which uses the aforementioned fabric formwork 41 to protect the embankment back slope from river overflow, and consists of the following steps: (1) A step of laying the cloth formwork 41 on the back slope 11, (2) A step of pouring mortar or concrete into the inside of the bag body 42 of the cloth formwork 41 to form a molded structure 40, (3) The process includes embedding the upper end of the molded structure 40 into the interior of the embankment at the top of the embankment 14. The details are explained below.

[0077] (1) Lay the cloth formwork 41 on the back slope 11. First, a cloth formwork 41 is laid on the back slope 11 with the upper cloth 43 side facing upwards (outside).

[0078] Furthermore, it is preferable to place a breathable waterproof sheet (waterproof sheet) 30 between the slope and the molded structure 40. This more reliably prevents overflowing water from flowing around to the back of the molded structure 40 and also makes it more stable against centrifugal force (negative pressure) generated by overflowing water near the top of the slope.

[0079] It is preferable to shape the slope at the construction site before laying the air-permeable waterproof sheet 30 and the fabric formwork 41 on the slope. Slope shaping mainly involves, for example in the case of an embankment, cutting and filling based on the planned cross-sectional drawing to eliminate unevenness in the ground and removing trees, grass, roots, etc.

[0080] Furthermore, if the slope to be protected is larger than a certain size, multiple units of the fabric formwork 41 of a predetermined size may be prepared and transported to the construction site. The fabric formwork 41 units may then be combined as appropriate while checking the shape of the construction site to form the fabric formwork 41 according to the size and shape of the slope at the construction site.

[0081] While aligning the position, the fabric formwork 41 is laid and fixed on the slope by a predetermined method, such as by driving a single pipe for suspension support into the top of the embankment 14 and passing the fabric formwork 41 through this single pipe to suspend it.

[0082] (2) A filler material 50 such as mortar or concrete is poured into the inside of the bag 42 of the cloth formwork 41 to form a molded structure 40.

[0083] After the laying process, a fluid (unsolidified) filler material 50 such as mortar or concrete is injected between the upper layer fabric 43 and the lower layer fabric 44. Then, the site is maintained until the filler material 50 injected into the fabric formwork 41 solidifies, and the filler material 50 is solidified by controlling the temperature and waterproofing necessary for solidification.

[0084] Furthermore, after the filler material 50 has solidified, at least the mesh portion 47 and the filter portion 49 of the cloth mold 41 may be washed with water.

[0085] Excess water contained in the filler 50 is discharged through the mesh of the cloth mold 41 during the solidification process. After the filler 50 has solidified, at least the mesh portion 47, the filter portion 49, and the entire molded structure 40 (mat) are washed with water.

[0086] (3) The upper end of the molded structure 40 is embedded into the embankment at the top of the embankment 14.

[0087] For example, the upper end of the molded structure 40 is inserted into the lower side of the slope protection structure 22 made of concrete blocks or the like and fixed in place. Alternatively, the upper end of the molded structure 40 may be embedded in the embankment soil 10.

[0088] Furthermore, when a breathable waterproof sheet 30 is placed between the back slope 11 and the molded structure 40, it is preferable to embed the upper end of the breathable waterproof sheet 30 together with the molded structure 40 into the interior of the dam body.

[0089] Furthermore, soil may be added to the mesh portion 47 of the molded structure 40 and seeds may be sown. This makes it possible to grow vegetation on the back slope 11 covered by the molded structure 40, thereby promoting the greening of the embankment slope.

[0090] This construction method prevents overflowing water from flowing around the back of the molded structure 40, thereby more reliably preventing levee breaches or extending the time until a breach occurs. As a result, it is possible to construct a "resilient river levee" that is resistant to overflows.

[0091] Furthermore, the fabric formwork 41 can be transported to the site in a folded state, and no special heavy machinery is required for its installation. Therefore, this construction method using fabric formwork 41 can be implemented even in narrow sites, and it can cover a large surface at once, making it highly efficient to install.

[0092] While embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the spirit of the invention.

[0093] The above describes the reinforcement structure for the back slope of a river embankment, but it is not limited to river embankments; the same configuration can be applied to embankments on coastlines, lakes, and other areas where overflow may occur. Furthermore, since the purpose of the present invention is to prevent the destruction and washing away of slope protection works when tsunamis or river currents overflow the embankment on coastlines and river embankments, the embankment slope to which the embankment reinforcement method of the present invention is applied is the back slope on the inside of the embankment. However, the slope reinforcement structure and method of the present invention can also be applied to reinforcement work on the front slope on the outside of the embankment, and to slope reinforcement work on areas other than embankments. [Examples]

[0094] The present invention will be described in detail below based on specific examples, but the present invention is not limited thereto.

[0095] In this experiment, the large-scale levee model experimental channel of the National Institute for Land and Infrastructure Management, as shown in Figure 8, was used. The levee model had a crest width of 3.0m, a levee height of 2.5m, a foundation ground height of 1.0m, a slope ratio of 1:2.0 between the front and back slopes, and a drainage height of 0.5m.

[0096] Figure 9 shows the particle size distribution of the dam material used in the dam model, and Figure 10 shows the compaction curve. The soil used was sandy soil with a fine particle content of FC = 20.4%.

[0097] For compaction, the optimal moisture content was adjusted to wopt = 22.5% (slightly wet), and the degree of compaction Dc was controlled to be approximately 90%.

[0098] The dam body protection structure was a surface covering type, consisting of the crest (asphalt pavement (5 cm asphalt surface layer, 15 cm crushed stone base layer)), the shoulder (shoulder blocks), the back slope (air permeable waterproof sheet + overflow prevention type fabric formwork), and the toe (overflow prevention type fabric formwork).

[0099] As shown in Figure 11, the fabric formwork was a mesh type with voids allowing for vegetation on the slope, and a filter type with drainage function at the toe of the slope (drain section), with mortar used as the filling material.

[0100] The fabric formwork has an average thickness of 100 mm. To prevent water seepage through the mesh gaps of the fabric formwork on the slope and to prevent water from seeping into the embankment, a breathable waterproof sheet was laid behind the fabric formwork.

[0101] A breathable waterproof sheet is a three-layer integrated sheet consisting of a breathable waterproof sheet with breathability and waterproofing properties, and a protective mat that protects both sides of it.

[0102] The fabric formwork was installed away from the channel sidewall to avoid creating resistance, and the permeable waterproof sheet was temporarily fixed with its ends raised against the channel sidewall. In addition, to evaluate the joints, the fabric formwork had a joint (butt joint) in the center of the channel.

[0103] For the breathable waterproof sheet, two joints (with an adhesive width of 10 cm) were provided in positions that did not overlap with the joints of the fabric formwork.

[0104] The drainage system consisted of a cage made of wire rods with recycled high-strength polyester fibers as the core material and coated with polyethylene to improve durability. This cage was then filled with crushed stone (particle size 150-230 mm). After filling, it was covered with an anti-suction sheet (long-fiber nonwoven fabric t=3 mm).

[0105] In the overflow experiment, the water level was raised at a constant speed until the overflow depth reached 30 cm, then the water depth was kept constant. After more than one hour, the overflow was temporarily stopped, and level measurements were taken at the center of the crest, the shoulder block, the center of the back slope, the toe of the back slope, the horizontal section of the back slope, and the foundation ground. The same conditions were repeated three times, and the erosion resistance performance was evaluated after a total overflow time of more than three hours. During the overflow experiment, the flow velocity and water depth were measured at each location, as well as at the level measurement locations. The flow velocity was measured using an electromagnetic flow meter.

[0106] <Experimental Results> Figures 12 to 14 show the overflow experiment, and Figure 15 shows the level measurements of each part every hour of overflow. The vertical axis represents the level, and the horizontal axis represents the horizontal distance from the center of the top surface.

[0107] Level measurement results showed that in the foundation ground downstream of the covering work, erosion progressed as the overflow time elapsed. However, almost no displacement was observed in other parts of the embankment before and after the overflow experiment, and the embankment crest height remained unchanged.

[0108] Table 1 summarizes the flow velocities measured at each section during the overflow experiment. The flow velocity was approximately 1.5 m / sec at the center of the crest, and reached a maximum of 4.2 m / sec as it flowed down the slope with a gradient of 1:2.0.

[0109] [Table 1]

[0110] Based on the above results, measurements taken after 3 hours of overflow at an overflow depth of 30 cm or more confirmed that the top protection work (asphalt pavement, slope shoulder blocks), back slope protection work (fabric formwork mesh section), and back slope toe protection work (drain work, fabric formwork filter section) maintained their shape without displacement.

[0111] Therefore, it was confirmed that the embankment back slope reinforcement structure of the present invention has the performance to withstand external forces of "overflow depth: 30 cm, overflow time: 3 hours," which are the benchmarks for performance evaluation. [Industrial applicability]

[0112] The embankment back slope reinforcement structure according to the present invention prevents overflowing water from flowing around to the back of the molded structure, thereby more reliably preventing embankment failure or extending the time until failure occurs, and can be widely used as an embankment slope reinforcement structure to protect the embankment's inner slope.

[0113] Furthermore, the technology of this invention received a Class B technical evaluation in the Ministry of Land, Infrastructure, Transport and Tourism's public call for proposals for "Technologies for Resilient River Embankments" (dated March 10, 2023). [Explanation of Symbols]

[0114] 10: Embankment 11: Back slope 12: Surface 14: Top of the levee 20: Drain work 21: Waterproof sheet 22: Lower shoulder protection 30: Breathable waterproof sheet 31: Waterproof layer 32: Reinforcement layer 33: Reinforcement layer 40: Molded structure 41: Fabric formwork 41A: First part 41B: Second part 42: Bag body 43: Upper layer cloth 44: Lower layer cloth 45: Double layer fabric 46: Single layer fabric 47: Mesh section 48: Single layer fabric 49: Filter section 50: Filling material 60: Basket Mat 61: Long fiber 62: Uncured thermosetting resin 63:Thermoplastic resin 64: Intermediate 65: Covered knotless net 66: Surface construction material 100: Reinforcement structure for the slope behind the embankment

Claims

1. A reinforcing structure for the inner slope of a levee, which protects the inner slope of the levee from overflow, is constructed by laying a molded structure from the inner slope of the levee to the toe of the inner slope. The molded structure is formed by filling and solidifying mortar or concrete inside a fabric formwork having a bag-like body made of two layers of woven fabric, an upper layer and a lower layer. A levee back slope reinforcement structure characterized in that the upper end of the molded structure is embedded in the interior of the levee body at the top of the levee.

2. The embankment back slope reinforcement structure according to claim 1, wherein a breathable waterproof sheet is placed between the back slope and the molded structure.

3. The aforementioned fabric formwork consists of a bag made of a two-layer woven fabric, an upper layer and a lower layer, A first portion is provided on the back slope portion of the embankment, and has multiple mesh sections made of a single layer of woven fabric, which are formed in an island-like manner at predetermined intervals inside the bag body, The bag body comprises a second portion which is positioned adjacent to a drainage structure provided at the toe of the embankment and has multiple filter sections made of a single layer of woven fabric formed in an island-like manner at predetermined intervals inside the bag body, The embankment back slope reinforcement structure according to claim 1, wherein the first part and the second part are integrated.

4. A method for reinforcing the slope on the landward side of a levee to protect the slope on the inside of the levee from overflow, comprising the following steps: (1) A fabric formwork having a bag-like body made of a two-layer fabric consisting of an upper layer and a lower layer, is laid on the back slope. (2) A step of pouring mortar or concrete into the inside of the bag body of the cloth formwork to form a molded structure, (3) A method for reinforcing the back slope of a levee, characterized by comprising the step of embedding the upper end of the molded structure into the interior of the levee body at the top of the levee.

5. The method for reinforcing the back slope of a levee according to claim 4, wherein in step (1) above, a breathable waterproof sheet is placed between the back slope and the molded structure.

6. The aforementioned fabric formwork consists of a bag made of a two-layer woven fabric, an upper layer and a lower layer, The first part of the bag has multiple mesh sections made of a single layer of woven fabric, which are formed in an island-like manner at predetermined intervals inside the bag, The bag body comprises a second portion having a plurality of filter sections made of a single layer of woven fabric, formed in an island-like manner at predetermined intervals inside the bag body, The first part and the second part are integrated, The method for reinforcing the back slope of a levee according to claim 4, wherein in step (1) above, the first portion is placed on the back slope portion of the levee body, and the second portion is placed in contact with a drain provided at the toe portion of the levee body.

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