Greening soil covering material

Abstract

To provide greening soil covering material excellent in a greening function as using processed soil produced by mixing blast furnace slag fine particles and alkali stimulant with soil.SOLUTION: Greening soil covering material 1 is configured to mix plant seeds 6 enclosed or supported by biodegradable fiber material 5 with processed soil produced by mixing blast furnace slag fine particles 3 and alkali stimulant 4 with the soil 2. Total weight of mixed blast furnace slag fine particles and cement is 50 kg to 400 kg in 1 m3 of the soil where a weight ratio of the blast furnace slag fine particles and the cement is the blast furnace slag fine particles : cement=70 wt.% to 90 wt.% : 30 wt.% to 10 wt.% as using the cement as the alkali stimulant. The fiber material 5 is fiber net-like material formed in a tube shape and plant seeds 6 are placed with proper intervals within the tube shape.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a greening soil covering material that uses treated soil in which ground granulated blast furnace slag and an alkaline irritant are mixed into the soil, and yet has excellent greening properties. [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 flood damage 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 6, the mechanism by which a river levee collapses due to overtopping occurs when water overflows the top of the levee and flows to the back side of the river (Figure 6(A)), scouring the toe of the slope on the back side of the river and starting erosion (Figure 6(B)), causing the back slope to collapse (Figure 6(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 overflowing water.

[0010] On the other hand, soil mixed with a large amount of solidification material takes on a soil form similar to that of a cement-solidified soil, and does not have sufficient voids in the soil, resulting in a significantly reduced environment for plant growth. This makes it difficult for plants to grow, and when used for river embankments, etc., there are problems such as damage to the natural environment and scenery.

[0011] Therefore, a main object of the present invention is to provide a greening soil covering material that has excellent greening function while using treated soil in which ground granulated blast furnace slag and an alkaline irritant are mixed into the soil. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention relates to a first aspect of the present invention, which provides treated soil by mixing ground granulated blast furnace slag and an alkaline irritant into soil, A greening soil covering material is provided, which is characterized by having plant seeds mixed therein and surrounded or supported by a biodegradable fibrous material.

[0013] In the invention described in claim 1, first, treated soil made by mixing ground granulated blast furnace slag and an alkaline irritant is used as a covering material, so that the ground granulated blast furnace slag is hydrated by the stimulation of the alkaline irritant and undergoes a hardening reaction, so that the soil solidifies. Therefore, when used as covering soil for embankments, etc., even if the soil overflows due to flooding, erosion due to scouring is unlikely to occur, and it is possible to prevent the collapse of the embankment.

[0014] In addition, since fibrous materials are mixed together with the solidification materials (fine granulated blast furnace slag and alkaline irritant) in the early stages of construction, the mechanical properties of the fiber-reinforced soil, such as its strength and toughness (tenacity), are improved, and its resistance to erosion due to rainfall and running water is also improved.

[0015] On the other hand, in the case of treated soil in which ground granulated blast furnace slag and an alkaline irritant are mixed into the soil, when the soil hardens, the soil becomes similar to a cement-solidified soil, and the soil does not have sufficient voids, resulting in a significantly reduced environment for plant growth. In order to solve this problem, in the present invention, plant seeds surrounded or supported by biodegradable fiber materials are mixed into the soil. Therefore, when the biodegradable fiber materials are decomposed by microorganisms and voids are formed in the decayed fiber parts as the decomposition progresses, plants that germinate from the seeds can take root, and water and air are supplied through the voids, maintaining an environment in which the plant seeds can germinate, take root, and grow. Therefore, the surface of the cover soil is covered with plants, which preserves the natural environment and scenery, and the strength of the cover soil is improved by the roots of the plants spreading in the cover soil.

[0016] According to a second aspect of the present invention, there is provided the greening soil covering material according to the first aspect, in which cement is used as the alkaline irritant.

[0017] The invention described in claim 2 uses cement as an alkaline stimulant. As the alkaline stimulant, in addition to alkaline compounds such as calcium hydroxide, sodium hydroxide, potassium hydroxide, and sodium carbonate, cement can be used, and by using cement, the strength of the soil can be effectively increased.

[0018] In the present invention according to claim 3, the weight ratio of ground granulated blast furnace slag to cement is 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 and cement is 100% by weight. 3 The greening soil covering material according to claim 2 is provided, which is mixed in a ratio of 50 kg to 400 kg per unit area.

[0019] The invention described in claim 3 above shows a preferred blending example when cement is used as an alkali stimulant. By significantly increasing the ratio of ground granulated blast furnace slag to the amount of cement, CO2 emissions are reduced compared to when the entire amount of cement is used. 2 This will enable a significant reduction in emissions.

[0020] As the present invention according to claim 4, there is provided a greening soil covering material as described in claim 1, in which the fiber material is a fiber mesh material formed into a tubular shape, and plant seeds are arranged at appropriate intervals within this tube.

[0021] The present invention described in claim 4 shows an example of a suitable form for a fiber material. Specifically, the fiber material is preferably a fiber net material formed into a tube shape, with plant seeds arranged at appropriate intervals inside the tube. By adopting such a form, the plant seeds do not fall off the fiber material, and when the fiber material decays and voids are formed in that part, voids are formed around the plant seeds. These voids then become water channels, supplying moisture around the seeds, which creates the conditions for germination of the seeds and allows them to take root and grow. Effect of the Invention

[0022] As explained above in detail, according to the present invention, it is possible to provide a greening soil covering material having excellent greening functions, even when using treated soil in which ground granulated blast furnace slag and an alkaline irritant are mixed into the soil. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a manufacturing procedure diagram of the greening soil covering material 1 according to the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a cross-sectional view of a river embankment using the greening soil covering material 1. [Figure 4] This is a cross-sectional diagram of the soil covering work 10. [Diagram 5] FIG. 2 is a cross-sectional view of another example of a soil covering work 10. [Figure 6] This is a cross-sectional view showing the mechanism of river levee collapse due to overflow. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. [Greening soil cover material 1] The greening soil covering material 1 according to the present invention will be described in detail with reference to the drawings.

[0025] As shown in Figure 1, the greening soil covering material 1 is a treated soil prepared by mixing soil 2 with ground granulated blast furnace slag 3 and an alkaline irritant 4, and mixing in plant seeds 6 surrounded or supported by biodegradable fiber material 5.

[0026] 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.

[0027] The ground granulated blast furnace slag 3 is obtained by drying and pulverizing 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 4. 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.

[0028] As the alkaline stimulant 4, in addition to alkaline compounds such as calcium hydroxide, sodium hydroxide, potassium hydroxide, and sodium carbonate, cement can be used, and among these, cement is preferably used. When cement is used, the weight ratio of ground granulated blast furnace slag to cement is particularly set to 70% to 90% by weight: 30% to 10% by weight, and the total weight of ground granulated blast furnace slag and cement is 100g / kg. 3 It is desirable to mix 50kg to 400kg, preferably 70kg to 300kg, per 1 m of soil. 3 50kg / m 3 If it is less than 400kg / m, the strength of the cover soil 1 will be insufficient and scouring will easily occur. 3 If the hardness of the greening soil covering material 1 exceeds this value, the plants will not be able to take root sufficiently and the material will become unsuitable for vegetation.

[0029] Because a large amount of ground granulated blast furnace slag 3 is used, the greening soil covering material 1 is closer to being slightly alkaline than if the entire material was cement, which creates an environment in which plants can grow and also contributes to reducing carbon dioxide emissions generated during cement production.

[0030] The biodegradable fiber material 5 is a biodegradable fiber that is decomposed into water, carbon dioxide, etc. by the action of microorganisms. The biodegradable fiber material 5 includes natural fibers and biodegradable synthetic fibers. Examples of natural fibers include cotton, hemp, wool, silk, acetate, and fibers from trees and coconuts. Examples of biodegradable synthetic fibers include polylactic acid-based synthetic fibers and polyester-based synthetic fibers. 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.

[0031] The fiber length of the biodegradable fiber material 5 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 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 the biodegradable fiber material 5 of short fibers, it is possible to improve the entanglement with the soil particles of the soil 2, and it is easy to disperse and mix evenly in the soil 2. In addition, there is no particular limit to the fineness, but it is preferable to use one of 10 to 200 denier, preferably 50 to 150 denier. If the fiber is too thin, the reinforcing effect of the soil covering material 1 will decrease, and there is a risk that the roots of plants will not be able to penetrate into the decayed fiber part. In addition, it is preferable to use non-shrinking fibers to make it easier for the roots of plants to penetrate.

[0032] After the greening soil covering material 1 is applied, plant seeds 6 are surrounded or supported by the biodegradable fiber material 5 in order to allow plants to flourish. As a means for arranging the plant seeds 6 in the fiber material 5, it is preferable that the fiber material 5 is formed into a tube-like fiber net material 7, and a large number of plant seeds 6, 6... are arranged at appropriate intervals within this tube, as shown in Fig. 2. The length of this fiber material 5 is preferably about 50 to 300 mm.

[0033] The biodegradable fiber material 5 may be in the form of a string, a strip, or a sheet having plant seeds 6 supported within its fibers.

[0034] To mix the soil 2 with ground granulated blast furnace slag 3 and an alkaline stimulant 4 such as cement, and further mix the biodegradable fiber material 5 surrounding or supporting the plant seeds 6, these are placed in a mixing device such as a mixer and stirred for a certain period of time.

[0035] The greening soil covering material 1 thus produced is pumped by a compressed air pumping device and sprayed onto the surface of river banks, slopes, and embankments. Note that a means of transporting the material using heavy machinery such as a backhoe or a means of transporting the material using a belt conveyor may also be used.

[0036] The greening soil cover material 1 solidifies as the ground granulated blast furnace slag 3 hydrates with the alkaline irritant 4 and undergoes a hardening reaction. Therefore, when used as soil cover for a levee, it is difficult for erosion to occur due to scouring even if the soil overflows due to flooding, making it possible to prevent the collapse of the levee. The biodegradable fiber material 5 becomes entangled with the soil, improving mechanical properties such as strength and toughness (tenacity), and improving erosion resistance against rainfall and running water.

[0037] Furthermore, the biodegradable fiber material 5 is decomposed by microorganisms, and as the decomposition progresses, gaps are formed in the decayed fiber parts, allowing water and air to be supplied through these gaps, maintaining an environment that is favorable for the germination, rooting and growth of the plant seeds 6. As a result, 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 within the covering soil.

[0038] [River embankment structure using greening soil covering material 1] Next, an example in which the greening soil covering material 1 according to the present invention is used as a soil covering work 10 for a river bank will be described in detail.

[0039] The example shown in Fig. 3 is an example in which a two-layer soil covering work 10 consisting of a surface layer 11 and a lower layer 12 is provided on the surface portion of the slope and foot of a river levee. The construction of the soil covering work 10 is not limited to this, and it may be a single-layer structure as shown in Fig. 5, or a multi-layer structure of three or more layers (not shown).

[0040] In the example of the river embankment shown in Fig. 3, as described above, it is constructed in a two-layer structure consisting of a surface layer 11 and a lower layer 12. In this case, when plant seeds 6 surrounded or supported by biodegradable fiber material 5 are mixed in, it is preferable to mix them only in the surface layer 11 and not in the lower layer 12. By mixing seeds only in the surface layer 11, it is possible to eliminate waste of seeds that germinate in the lower layer 12 but do not grow to the surface and die, and plants are more likely to grow luxuriantly on the surface of the soil cover work 10. When the soil cover work 10 is constructed in a multi-layer structure of three or more layers, the plant seeds 6 surrounded or supported by biodegradable fiber material 5 are mixed in the outermost layer.

[0041] In the case where the soil cover 10 is composed of a surface layer 11 and a lower layer 12, the lower layer 12 may use fibers that are less likely to decompose as the biodegradable fiber material 5 compared to the surface layer 11. By using fibers that are less likely to decompose as the biodegradable fiber material 5 of the lower layer 12, the reinforcing effect of the fibers of the lower layer 12 is sustained for a long period of time, and the biodegradable fiber material 5 mixed in the lower layer 12 starts to biodegrade when the roots of the plants growing in the surface layer 11 reach the boundary between the surface layer 11 and the lower layer 12. This makes it possible to suppress a decrease in the reinforcing effect of the biodegradable fiber material 5, and does not inhibit the growth of the roots of the plants from the surface layer 11 to the lower layer 12. Here, "less likely to decompose" means that the period (biodegradation period) until the fibers biodegrade and decay is long. The difference in the biodegradation period between the surface layer 11 and the lower layer 12 is preferably about 1 to 3 years.

[0042] Furthermore, the biodegradable fiber material 5 of the lower layer 12 may have a smaller fineness than the biodegradable fiber material 5 of the surface layer 11. When plant roots extend from the surface layer 11 to the lower layer 12, the lower layer 12 has many fine roots that are subdivided compared to the surface layer 11, so it is preferable to arrange the biodegradable fiber material 5 with a small fineness so that such fine roots can spread. When the same type of fiber is used in the surface layer 11 and the lower layer 12, the total weight of the fibers to be mixed is the same.

[0043] Furthermore, it is preferable that the lower layer 12 has a larger mixing ratio of the ground granulated blast furnace slag 3 and the cement (alkali stimulant) 4 than the surface layer 11. By increasing the mixing ratio in the lower layer 12, the strength of the lower layer 12 increases, and even if the surface layer 11 is scoured by the water flowing on the surface, the scour to the lower layer 12 can be suppressed.

[0044] In the river embankment covering work 10 of the present invention, a large amount of ground granulated blast furnace slag 3 and cement (alkaline stimulant) 4 are mixed with the soil 2 to form a semi-concrete soil, which makes it less likely for erosion of the back side of the river due to scouring when the water overflows, resulting in a river embankment with a resilient structure.

[0045] Furthermore, since both the ground granulated blast furnace slag 3 and the cement (alkaline irritant) 4 contain biodegradable fiber material 5, in addition to the reinforcing effect due to solidification, the biodegradable fiber material 5 acts as a reinforcing agent by intertwining with the soil particles of the soil 2, further improving mechanical properties such as strength and toughness (tenacity). This improves the shear strength against external forces, and further increases erosion resistance against rainfall, running water, and the like.

[0046] Furthermore, biodegradable fiber material 5 that can be decomposed by microorganisms is used as the fiber, and plant seeds 6 are placed in this fiber material 5. As a result, voids are formed in the fiber parts that are decomposed and decayed by microorganisms, and water and air are supplied to the inside of the covering soil through these voids. This maintains a vegetative environment in which plant seeds can easily germinate, take root, and grow, thereby preserving the natural environment and landscape, and further improving the strength of the covering soil as the plants take root.

[0047] Furthermore, even if the biodegradable fiber material 5 flows into a river or the sea due to runoff during construction or scouring during use, the biodegradable fiber material 5 will be decomposed by microorganisms in the water, preventing plastic from flowing into the ocean as would occur in the case of using synthetic fibers, making it possible to create an environmentally friendly covering work 10.

[0048] [Other examples] (1) In the above embodiment, an example was shown in which the greening soil covering material 1 of the present invention was used as a soil covering work 10 for a river embankment, but this greening soil covering material 1 can also be suitably used as soil covering applied to the soil surface of river banks, slopes and embankments. [Explanation of symbols]

[0049] 1...Greening soil cover material, 2...Soil, 3...Blast furnace slag powder, 4...Cement (alkaline stimulant), 5...Biodegradable fiber material, 6...Plant seeds, 7...Tubular fiber net material (biodegradable fiber material), 10...River embankment soil cover, 11...Surface layer, 12...Sublayer

Claims

1. The soil is treated by mixing ground granulated blast furnace slag and an alkaline irritant into the soil. A greening soil covering material characterized by containing plant seeds surrounded or supported by a biodegradable fiber material.

2. 2. The greening soil covering material according to claim 1, wherein the alkaline irritant is cement.

3. The weight ratio of ground granulated blast furnace slag to cement is 70% to 90% by weight: 30% to 10% by weight, and the total weight of ground granulated blast furnace slag and cement is 1 m3 of soil. ３ The greening soil covering material according to claim 2, which is mixed in a ratio of 50 kg to 400 kg per unit area.

4. 2. The greening soil covering material according to claim 1, wherein the fiber material is a fiber net material formed into a tube shape, and plant seeds are arranged at appropriate intervals inside the tube shape.

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