Soil covering material

Abstract

To provide soil covering material excellent in a greening function as well as preventing drainage of fiber for the soil covering material reinforced through mixing blast furnace slag fine particles and the fiber in the soil.SOLUTION: A soil covering agent 1 produced by mixing blast furnace slag fine particles 3 and fiber 4 in the soil 2, wherein the fiber 4 is made of biodegradable fiber, and the alkali stimulant 5 is mixed in the fiber 4. Lime and / or cement is used as the alkali stimulant 5. The fiber 4 forms a core sheath structure, the alkali stimulant 5 is mixed in a sheath part 7, and the core par 6 does not include the alkali stimulant 5.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a soil covering material in which ground granulated blast furnace slag and fibers are mixed into soil to reinforce the soil and prevent the fibers from flowing out. [Background technology]

[0002] In recent years, there have been many floods that far exceed the capacity of flood control facilities due to the intensification and concentration of rainfall, and according to the Non-Patent Document 1 below, flooding caused by Typhoon No. 19 of 2019 (2019 East Japan Typhoon) resulted in the collapse of river levees in 142 locations nationwide (86% of which were caused primarily by overflowing) and caused extensive damage, including the inundation of approximately 35,000 hectares. It is expected that damage caused by floods will become more frequent and severe due to climate change in the future, and there is a need to prevent and mitigate this damage.

[0003] In order to prevent and mitigate flood damage, the basic principle will remain the same as in the past: lowering river water levels as much as possible by dredging and widening river channels and constructing flood control facilities such as dams and floodplains. However, there is an increasing need to implement efficient and effective measures to reduce damage caused by flooding as much as possible even in the case of floods that exceed the capacity of flood control facilities, and the Ministry of Land, Infrastructure, Transport and Tourism has indicated a policy that it is necessary to consider measures to strengthen river levees against overflowing.

[0004] For this reason, there is a need for river levees with a resilient structure that is less likely to collapse even if the water overflows, and that has a disaster mitigation effect such as lengthening the time until the levees collapse ("resilient river levees" even if they are overflowed).

[0005] As shown in Figure 4, the mechanism by which river levees collapse due to overtopping occurs when water overflows the top of the levee and flows to the back side of the river (Figure 4(A)), scouring the toe of the slope on the back side of the river and starting erosion (Figure 4(B)), causing the back slope to collapse (Figure 4(C)), and ultimately leading to the collapse of the top of the levee.

[0006] One method for preventing erosion of slopes and other embankments is to use fiber-mixed reinforced soil, in which fibers are mixed into soil, as cover soil for the construction of river embankments, embankments, and the surface layers of ground slopes, as disclosed in, for example, Patent Documents 1 and 2 listed below. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-306834 [Patent Document 2] Japanese Patent Application Publication No. 10-204882 [Non-patent literature]

[0008] [Non-Patent Document 1] Technical Review Committee on Strengthening River Levees, Reference Material 1 Report of the Technical Review Committee on River Levees in light of the damage caused by Typhoon No. 19 of 2019, August 2020 Summary of the Invention [Problem to be solved by the invention]

[0009] However, although the conventional fiber-mixed reinforced soil disclosed in Patent Documents 1 and 2 and the like can be expected to improve strength to a certain extent by intertwining the reinforcing fibers with the soil particles, it has lower strength than soil improvement using solidifying materials such as cement and ground granulated blast furnace slag, and is less effective at preventing erosion due to scouring caused by overflow.

[0010] On the other hand, in fiber-reinforced soil, which is made by mixing ground granulated blast furnace slag and fibers into the soil, it takes a considerable amount of time for the ground granulated blast furnace slag to harden, so there is a concern that the fibers may be washed away during use due to rainfall or running water until the ground granulated blast furnace slag hardens.

[0011] In addition, soil that has been mixed with a large amount of solidifying agent takes on a soil form similar to that of a cement-solidified soil, with no sufficient voids in the soil, significantly reducing the environment for plant growth. This makes it difficult for plants to grow, and when the soil is used for river embankments, etc., there are problems such as damage to the natural environment and scenery.

[0012] Therefore, the main object of the present invention is to provide a soil covering material which is reinforced by mixing ground granulated blast furnace slag and fibers into the soil, which prevents the fibers from flowing out and has excellent greening properties. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention according to claim 1 provides a soil covering material in which ground granulated blast furnace slag and fibers are mixed with soil, The soil covering material is characterized in that the fibers are made of biodegradable fibers and an alkaline irritant is mixed into the fibers.

[0014] In the invention described in claim 1 above, treated soil made by mixing ground granulated blast furnace slag and fibers into soil is used as a soil cover material, so that the ground granulated blast furnace slag solidifies and, by mixing in fibers, it is expected to improve mechanical properties such as strength and toughness (tenacity) and to improve erosion resistance against rainfall, running water, etc. Therefore, when used as a cover soil for embankments, etc., erosion due to scouring is unlikely to occur even if the soil overflows due to flooding, and it is possible to prevent the collapse of the embankment.

[0015] In addition, since the fibers are made of biodegradable fibers and an alkaline irritant is mixed into the fibers, the alkaline content eluted from the fibers acts as an irritant to harden the ground granulated blast furnace slag, making it possible to produce homogeneous reinforcement soil. Furthermore, as the alkaline irritant is eluted from the fibers, the hardening of the ground granulated blast furnace slag starts from the fiber surface, and the hardening spreads from there in a diffusive manner, so that the fibers can be fixed to the improved soil until they are biodegraded, making it possible to prevent the fibers from flowing out.

[0016] Furthermore, when biodegradable fibers are decomposed by microorganisms and voids form in the decayed fiber, plants that germinate from scattered plant seeds can take root, and water and air can be supplied through these voids, maintaining an environment conducive to plant germination, rooting, and growth. As a result, the surface of the cover soil is covered with plants, preserving the natural environment and scenery, and the strength of the cover soil is improved as the roots of the plants spread within the cover soil.

[0017] As a second aspect of the present invention, there is provided the soil covering material according to the first aspect, in which either or both of lime and cement are used as the alkaline irritant.

[0018] In the invention described in claim 2, lime and / or cement are used as an alkaline stimulant for the ground granulated blast furnace slag. By using lime and / or cement, it becomes easier to mix with the fibers and easier to dissolve from the fibers.

[0019] The present invention according to claim 3 provides the soil covering material according to claim 1, wherein the fibers have a core-sheath structure, the alkaline irritant is mixed in the sheath portion, and the core portion does not contain the alkaline irritant.

[0020] In the invention described in claim 3, the fiber has a core-sheath structure consisting of a core and a sheath, and the alkaline irritant is mixed only in the sheath. This allows the ground granulated blast furnace slag on the fiber surface to harden quickly, and the core improves the reinforcing effect of the covering soil.

[0021] According to a fourth aspect of the present invention, there is provided the soil covering material according to the third aspect, in which fibers having different decomposition performance are used for the core and sheath.

[0022] In the invention described in claim 4 above, fibers having different decomposition properties are used for the core and sheath. By using a material that has quick biodegradability for the sheath, the alkaline irritant contained in the sheath is dissolved early, which promotes the hardening of the ground granulated blast furnace slag on the fiber surface.

[0023] The present invention according to claim 5 provides the soil covering material according to claim 3, in which a synthetic fiber that is difficult to biodegrade is used for the core portion, and a biodegradable fiber is used for the sheath portion.

[0024] In the invention described in claim 5 above, the core is made of synthetic fiber that is not easily biodegradable, so that the core remains intact even after the sheath biodegrades, thereby improving the strength of the covering soil. Effect of the Invention

[0025] As explained above in detail, according to the present invention, a covering material in which ground granulated blast furnace slag and fibers are mixed with soil to reinforce it can prevent the fibers from flowing out and has excellent greening properties. [Brief description of the drawings]

[0026] [Figure 1] FIG. 2 is a diagram showing a manufacturing procedure for the soil covering material 1 according to the present invention. [Diagram 2] FIG. 2 is a perspective view showing a fiber 4 according to a first embodiment. [Diagram 3] FIG. 4 is a perspective view showing a fiber 4 according to a second embodiment. [Figure 4] This is a cross-sectional view showing the mechanism of river levee collapse due to overflow. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings. The soil cover material 1 according to the present invention can be used for covering soil on river embankments, river revetments, slopes and the soil surface of embankments.

[0028] As shown in Figure 1, the soil covering material 1 of the present invention is a mixture of soil 2, ground granulated blast furnace slag 3, and fiber 4, wherein the fiber 4 is made of biodegradable fiber and an alkaline irritant 5 is mixed into the fiber 4.

[0029] There are no particular limitations on the soil 2, and a wide variety of soils can be used, including clayey soil, silty soil, sandy soil, gravel, etc. In some cases, stabilized soil whose properties have been chemically improved by mixing an improving material such as a cement-based or lime-based material in powder or slurry form may be used.

[0030] The ground granulated blast furnace slag 3 is obtained by drying and crushing granulated blast furnace slag, which is a by-product in the process of manufacturing pig iron in a blast furnace, and is known to be hydrated and hardened by contact with an alkaline stimulant 5. As the ground granulated blast furnace slag 3, several types with different Blaine values ​​are available on the market, and any of them can be used without any particular restrictions.

[0031] As the fiber 4, a biodegradable fiber material, that is, a biodegradable fiber that is decomposed into water, carbon dioxide, etc. by the action of microorganisms, is used. The fiber 4 includes natural fibers and biodegradable synthetic fibers. Natural fibers include cotton, hemp, wool, silk, acetate, and fibers from trees and coconuts. Biodegradable synthetic fibers include polylactic acid-based synthetic fibers, polyester-based synthetic fibers, etc. For example, synthetic fibers including polylactic acid (PLA), polyhydroxyalkanoate (PHA), biopolybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT)-polylactic acid (PLA) compound, starch polyester resin, cellulose acetate (diacetate), polyvinyl alcohol (PVA), polyglycolic acid (PGA), polybutylene succinate (PBS), polybutylene succinate (PBSA), polybutylene adipate terephthalate (PBAT), polyethylene terephthalate succinate (PETS), etc. can be used. The biodegradable fiber material 5 is one that can maintain the fiber reinforcing effect of the covering soil for about 1 to 5 years.

[0032] The fiber length of the fibers 4 is not particularly limited, but it is preferable to use short fibers of about 10 to 250 mm. The shorter the fiber length, the better from the viewpoint of mixability and agitation with the soil 2, and the longer the fiber length, the better from the viewpoint of strength reinforcement. Therefore, a preferable range of the fiber length is determined taking into consideration the balance between the two. By using a biodegradable fiber material of short fibers, the fibers are well entangled with the soil particles of the soil 2, and are easily dispersed and mixed in the soil 2. There is also no particular limitation on the fineness, but it is preferable to use fibers of 10 to 200 denier, preferably 50 to 150 denier. If the fibers are too thin, the reinforcing effect of the reinforced soil 1 will decrease, and there is a risk that plant roots will not be able to penetrate into the decayed fiber part. In addition, if the fibers are too thick, it will take a long time to biodegrade and the elution of the mixed alkaline stimulant 5 will be reduced, so that the hardening of the ground granulated blast furnace slag 3 may be delayed. In addition, it is preferable to use non-shrinking fibers in order to make it easier for plant roots to penetrate into the voids of the decayed fibers.

[0033] As the alkaline stimulant 5, in addition to alkaline compounds such as calcium hydroxide, sodium hydroxide, potassium hydroxide, and sodium carbonate, lime and cement can be used. Among these, it is preferable to use either or both of lime and cement.

[0034] The method of mixing the alkaline stimulant 5 into the fiber 4 is not particularly limited, and may include a method of mixing and kneading the alkaline stimulant 5 into the molten raw material of the synthetic fiber, and then spinning it to add it internally, or a method of mixing the alkaline stimulant 5 during the fiber spinning process to adhere it to the surface, and then combining it with a binder as needed to increase the amount of adhesion or prevent the attached alkaline stimulant 5 from falling off.

[0035] The alkaline stimulant 5 is mixed into the fibers 4, and also mixed into the soil 2 alone, as shown in FIG. 1. As the alkaline stimulant 5 to be mixed into the soil 2 alone, as described above, it is possible to use alkaline compounds such as calcium hydroxide, sodium hydroxide, potassium hydroxide, and sodium carbonate, as well as lime and cement, and among these, cement is preferably used. When cement is used as the alkaline stimulant 5 to be mixed into the soil 2 alone, the weight ratio of the ground granulated blast furnace slag 3 to the cement is particularly set to 70% by weight to 90% by weight: 30% by weight to 10% by weight, and the total weight of the ground granulated blast furnace slag 3 and the cement is 100% by weight per 1 m of soil. 3 It is desirable to mix 50 to 400 kg, preferably 70 to 300 kg, per 1 m of soil. 3 50kg / m 3 If the soil cover material 1 is less than 400 kg / m, the strength of the soil cover material 1 is insufficient and scouring is likely to occur. 3 If the temperature exceeds this range, the hardness of the covering material 1 increases, preventing plants from taking root sufficiently, making the material unsuitable for vegetation.

[0036] Because a large amount of ground granulated blast furnace slag 3 is used, the soil covering material 1 becomes closer to a weak alkaline state compared to when the entire material is made of cement, which creates an environment in which plants can grow and contributes to reducing carbon dioxide emissions generated during cement production.

[0037] In order to mix the ground granulated blast furnace slag 3 and the fibers 4 into the soil 2, they are placed in a mixing device such as a mixer and stirred for a certain period of time.

[0038] The soil covering material 1 thus produced is pumped by a pumping device using compressed air and sprayed onto the surface of river banks, slopes, and embankments. Note that a means of transporting the soil covering material using heavy machinery such as a backhoe or a means of transporting the soil using a belt conveyor may also be used.

[0039] In the soil covering material 1, the ground granulated blast furnace slag 3 is hydrated by the alkaline irritant 5 and undergoes a hardening reaction, solidifying the soil. Therefore, when used as soil covering for a levee, it is possible to prevent erosion due to scouring even if the soil overflows due to flooding, and to prevent the collapse of the levee. In addition, by entangling the fibers 4 with the soil, mechanical properties such as strength and toughness (tenacity) can be improved until the fibers 4 are biodegraded, and erosion resistance against rainfall, running water, etc. can be improved.

[0040] In addition, since the fibers 4 are made of biodegradable fibers and contain an alkaline irritant 5, the alkaline content eluted from the fibers 4 acts as an irritant to harden the ground granulated blast furnace slag 3, making it possible to produce a homogeneous soil covering material. In addition, the alkaline irritant 5 mixed in the fibers 4 is eluted during the biodegradation process of the fibers 4, and the soil begins to harden as it diffuses from the fiber surface, so the fibers 4 can be fixed to the soil covering material and the fiber 4 can be prevented from being washed away.

[0041] Furthermore, the fibers 4 made of biodegradable fibers are decomposed by microorganisms, and as the decomposition progresses, voids are formed in the decayed fiber parts, allowing water and air to be supplied through these voids, maintaining an environment in which scattered plant seeds and the like can easily germinate, take root, and grow, so that the surface of the covering soil is covered with plants, preserving the natural environment and scenery, and the strength of the covering soil is improved as the roots of the plants spread in the covering soil. In order to cover the surface of the soil covering material 1 with plants early, plant seeds may be mixed into the soil 2 or scattered on the surface of the soil covering material 1 in advance. There are no restrictions on the form in which the plant seeds can be mixed in, but by mixing plant seeds surrounded or supported by biodegradable fiber material, the biodegradable fiber material is decomposed by microorganisms.As the decomposition progresses, gaps are formed in the decayed fiber parts, allowing plants that germinate from the seeds to take root and allowing water and air to be supplied through these gaps, thereby maintaining an environment conducive to the germination, rooting and growth of the plant seeds.The surface of the covering soil is covered with plants, preserving the natural environment and landscape, and the strength of the covering soil is further improved as the roots of plants spread within the covering soil.

[0042] [Example of fiber 4 morphology] (First embodiment) As shown in FIG. 2, the fiber 4 of the first embodiment is a normal fiber in which the entire cross section of the fiber 4 is made of the same material, and the alkaline irritant 5 is mixed into this fiber 4 almost uniformly.

[0043] At the beginning of installation of the soil covering material 1, the alkaline irritant 5 attached to the surface of the fibers 4 dissolves, hardening the ground granulated blast furnace slag 3 around the fibers 4, and as the fibers 4 decay, the ground granulated blast furnace slag 3 inside dissolves, and the hardened range of the ground granulated blast furnace slag 3 gradually spreads.

[0044] (Second embodiment) 3, the fiber 4 of the second embodiment has a core-sheath structure, the alkaline irritant 5 is mixed in the sheath portion 7, and the core portion 6 does not contain the alkaline irritant 5. The alkaline irritant 5 in the sheath portion 7 is dissolved from the fiber 4, so that the fiber 4 can be quickly fixed to the soil covering material 1.

[0045] In addition, in the fiber 4 having a core-sheath structure, it is possible to use a fiber having different decomposition performance between the core portion 6 and the sheath portion 7. For example, in order to quickly elute the alkaline irritant 5 mixed in the sheath portion 7 and solidify the ground granulated blast furnace slag 3 on the surface of the fiber 4, the sheath portion 7 can be made of a material that is more easily decomposed than the core portion 6.

[0046] Furthermore, it is also possible to use synthetic fibers that are difficult to biodegrade for the core 6 and biodegradable fibers for the sheath 7. In this way, even after the sheath 7 has biodegraded and decayed, the synthetic fibers that are difficult to biodegrade for the core 6 will act as a reinforcing material, improving the mechanical properties of the cover soil, such as its strength and toughness. [Explanation of symbols]

[0047] 1...covering material, 2...soil, 3...fine powder of blast furnace slag, 4...fiber, 5...alkaline stimulant, 6...core, 7...sheath

Claims

1. A covering material in which ground granulated blast furnace slag and fibers are mixed with soil, A soil covering material characterized in that the fibers are made of biodegradable fibers and an alkaline irritant is mixed into the fibers.

2. 2. The soil covering material according to claim 1, wherein either lime or cement or both are used as the alkaline stimulant.

3. 2. The soil covering material according to claim 1, wherein the fibers have a core-sheath structure, the alkaline irritant is mixed in the sheath portion, and the alkaline irritant is not contained in the core portion.

4. 4. The soil covering material according to claim 3, wherein the core and sheath parts are made of fibers having different decomposition properties.

5. 4. The soil covering material according to claim 3, wherein the core part is made of a synthetic fiber which is difficult to biodegrade, and the sheath part is made of a biodegradable fiber.

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