Slope face conservation method and program for slope face conservation method

Abstract

To provide a new civil engineering technology that also takes measures against flood damage caused by heavy rain on a slope face.SOLUTION: A slope face conservation method includes: forming a trench on the slope face of a site to guide running water; and placing water-permeable and water-retention material in the trench. The water-permeable and water-retention material is filled into a mesh bag having a predetermined size and shape and the mesh bags are placed continuously or at a predetermined interval in the trench.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a slope conservation method and a program for the slope conservation method. [Background technology]

[0002] In recent years, record-breaking torrential rains have occurred frequently in both mountainous and plain areas, causing great human and economic losses. In particular, electricity transmission towers, which are representative of social infrastructure facilities, have their main cables spread across mountainous areas, and if they collapse, it could cause a power outage on hundreds of thousands of households. For this reason, site conservation measures that can handle the recent weather conditions are also required for the sites of electricity transmission towers.

[0003] Up until now, site conservation has mainly been achieved by adopting greening methods, but there have been frequent incidents of sites being washed away together with greenery due to increased erosion caused by torrential rains that exceeded expectations. For example, a conventional greening method involves applying a mixture of soil and cement to the slope and then spraying on it with asphalt emulsion.

[0004] However, in the case of a method in which a mixture of soil and cement is laid on a slope and then asphalt emulsion is sprayed on, there is a problem that rainwater seeps in between the cement mixed layer and the slope, which can easily cause the cement mixed layer to peel off and collapse. Therefore, a method has been proposed in which a vegetation net is laid on the slope to cover it and prevent the topsoil from sliding off.

[0005] However, when covered only with a net, rainwater can penetrate the topsoil layer during rainfall, making it susceptible to scouring, and there is a limit to the ability to fix the topsoil in place. Therefore, a construction method has been developed in which a frame is laid on the slope to prevent the topsoil from sliding off, but within the area of ​​the frame, there is nothing to fix the topsoil to the slope, so there is an issue that the adhesion between the slope and the topsoil layer is insufficient, making it easy for the added soil to slide off.

[0006] As described above, with conventional slope greening methods, the adhesion between the topsoil and the slope is insufficient, leading to the topsoil sliding off or erosion by collected and infiltrated rainwater, and the reality is that the intended objectives from the perspective of slope conservation are not being achieved.

[0007] On the other hand, one method of utilizing coal ash in a greening technique for slopes is disclosed in which a retaining mat member is laid on the slope of an iron flat block and secured in place with anchor members, soil containing a binder is added until the retaining mat member is covered to form a layer of soil, and then a layer of soil containing plant seeds, fertilizer, and an erosion prevention agent is sprayed on top to form a plant growth layer, in which the binder and erosion prevention agent contain fly ash and have water permeability and water retention properties (see Patent Document 1). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2001-90012 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, the above-mentioned prior art only mentions water permeability (good drainage) and weed-preventing properties that suppress the germination of plants such as weeds, and does not question its water retention. For example, there is no disclosure or suggestion of civil engineering technology that takes measures against flood damage caused by heavy rain.

[0010] An object of the present invention is to provide a new slope preservation method that also takes measures against flood damage caused by heavy rain on slopes. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention relates to a slope preservation method, which is characterized by forming a groove for guiding running water on the slope of a site and disposing a water-permeable material in the groove.

[0012] The present invention also relates to a program for a slope conservation method, which is characterized by having a computer perform calculations to select the position, number, length and depth of the grooves to be constructed on the slope and / or the number and type (particle size of the water-permeable material) of the mesh bags to be placed and optimize the layout, based on information related to the soil and shape of the slope, information related to the shape, position and falling water of structures on the slope, and / or weather information such as rainfall. Effect of the Invention

[0013] According to the present invention, it is possible to provide a new civil engineering technology that takes measures against flood damage caused by heavy rain on slopes, and it is possible to ensure site conservation that corresponds to the weather environment at the site of a transmission tower, which is a representative social infrastructure facility. It is also possible to establish an innovative site conservation method that contributes to the conservation of mountain ecosystems by promoting the restoration of vegetation and helps to achieve carbon neutrality. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a plan view showing a schematic diagram of a slope preservation method according to the present invention. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] 1 is a graph showing flow velocity attenuation by particle size. [Figure 4] 1 is a graph showing flow velocity attenuation by particle size. [Diagram 5] 1 is a graph showing flow velocity attenuation by particle size. [Figure 6] 1 is a graph showing flow velocity attenuation by particle size. [Figure 7] 13 is a table showing the step number attenuation effect. [Figure 8] 13 is a graph showing a step number attenuation effect. [Figure 9] 13 is a graph showing the water volume attenuation effect over time. [Figure 10] FIG. 13 shows the conservation points of the on-site test. [Figure 11] FIG. 13 shows the conservation points of the on-site test. [Figure 12]FIG. 1 is a diagram illustrating a conservation method for field testing using woven fence construction. [Figure 13] FIG. 13 shows the post-conservation areas of the field test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the present invention will be described based on an embodiment. FIG. 1 is a plan view for explaining the slope preservation method of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of the plan view shown in FIG.

[0016] In the slope preservation method of the present invention, grooves 11 are formed on a slope 10 as shown in Figures 1 and 2. The number of grooves 11 may be one or more in the direction of rainwater flow indicated by the arrows in the figures, but from the viewpoint of disposing a relatively large amount of water-permeable material to effectively preserve the flood damage countermeasures associated with localized heavy rain, it is preferable to have more than one groove 11. Specifically, in the range of inclination angles of 20 degrees to 40 degrees, it is preferable to have 2 to 4 grooves per 10 m width, and further, at inclination angles of 40 degrees or more, it is preferable to have 5 to 6 grooves per 10 m.

[0017] The width and depth of the groove 11 itself can be appropriately set from the viewpoint of disposing a water-permeable substance in the groove 11. From the viewpoint of fixing the water-permeable substance in the groove 11, it is preferable that the water-permeable substance is disposed so as to fit into the groove 11 in the width direction of the groove 11, and it is preferable that the width of the groove 11 is set to satisfy such a requirement.

[0018] Next, in the slope protection method of the present invention, a water-permeable retentive material 13 is placed in the groove 11. Since the water-permeable retentive material 13 is generally granular or powdery, the water-permeable retentive material 13 is filled in the net bag 12 and then placed in the groove 11, preferably fitted. The size of the net bag 12 can be, for example, a square shape with a mesh size of 1 mm to 4 mm, a width of 15 cm to 50 cm, and a length of 30 cm to 100 cm. By setting the mesh size of the net bag 12 within this range, rainwater that flows into the net bag 12 through the mesh due to heavy rain or the like reaches the water-permeable material 13 with large particle size filled in the net bag 12 and first loses its momentum, and is then led sequentially to the net bag 12 filled with the water-permeable material 13 with smaller particle size, losing momentum, and is absorbed into the porous material, and a part of it is gradually absorbed into the slope.

[0019] The width and length described above are preferable from the viewpoint of facilitating handling of the net bag 12. That is, as described in this embodiment, the slope preservation method of the present invention involves forming a trench 11 directly on-site and disposing the net bag 12 in the trench 11, but if the width and length of the net bag 12 are within the above-mentioned range, i.e., the size of the net bag 12 is determined by the above-mentioned width and length, handling becomes easy and the slope preservation method of the present invention can be easily carried out.

[0020] The material constituting the net bag 12 is not particularly limited, but when solidifying, it is preferable to use a biodegradable material. This allows the net bag 12 to decompose within a few months to a few years, leaving only the water-permeable, water-retentive substance 13 in the groove 11. This eliminates the need to dispose of the net bag 12 as waste. After the net bag 12 disappears, the water-permeable, water-retentive substance 13 will remain in the groove 11, and will continue to provide the above-mentioned effects.

[0021] Examples of biodegradable materials that can be used include natural products such as hemp, cotton, starch, and cellulose, as well as general-purpose biodegradable plastics such as polylactic acid, polycaprolactone, polybutylene succinate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, poly(caprolactone / butylene succinate), and poly(butylene succinate / adipate).

[0022] Examples of the water-permeable and retentive substance 13 include porous materials, such as clinker ash, volcanic gravel, pumice, and bora soil. In particular, clinker ash is preferable from the viewpoints of effective use of waste materials and water absorption and water retention. However, it goes without saying that any material made by kneading and solidifying cement-based solidification material and water is also acceptable. In this case, the porous material functions as the main body of the water-permeable and retentive substance, and the cement-based solidification material and water function as connecting materials for the main body of the water-permeable and retentive substance.

[0023] In addition, when using a connecting material as described above, it becomes necessary to transport a mixer or the like to the work site directly. Therefore, in such a case, it is preferable to mix the porous material with a cement-based solidification material in advance, fill the net bag 12 with this, and then spray water on it to solidify it. This saves the trouble of transporting a mixer or the like to the work site, improving work efficiency.

[0024] The clinker ash in the present invention refers to ash obtained by recovering, dehydrating and pulverizing a lump of coal ash that has fallen to the bottom of a boiler, among coal ash generated when coal is burned in a thermal power plant, etc. As the coal ash, clinker ash that has been crushed or sieved and classified to a particle size of about 0 mm to 40 mm is preferably used.

[0025] The weight ratio of porous material to joint material is clinker ash 1m 3200kg to 300kg of cement-based solidification material and 120 to 140 liters of admixture are mixed in a mixer to produce a mixture that is the material for the water-permeable and retentive substance 13. As the cement-based solidification material, Tufflock (product name: manufactured by Sumitomo Osaka Cement Co., Ltd.) can be used, but is not limited to this. The cement-based solidification material refers to a powder that hardens over time when mixed with an admixture such as water, and as this cement-based solidification material, for example, calcined gypsum, magnesia cement, hydraulic gypsum, natural cement, Portland cement, alumina cement, etc. can be used. In addition, in Figures 1 and 2, the water-permeable and retentive substance 13 is filled with mesh bags 12 and arranged at intervals, but the intervals can be appropriately controlled in consideration of the amount of rainfall such as torrential rain, and when the amount of rainfall is large, the mesh bags 12 can be arranged continuously in the vertical, horizontal, and height directions.

[0026] As shown in Figs. 1 and 2, the number of net bags 12 arranged for each groove 11 can be changed or the same. Furthermore, the amount and type (grain size) of the water-permeable material 13 filled in the net bags 12 can be changed or the same for each net bag. When the water-permeable material 13 filled in the net bags 12 is classified by grain size, the force of raindrops and running water can be reduced by the net bag 12 filled with the water-permeable material 13 having a large grain size, and the water can be gently guided in a desired direction by passing through the net bag 12 filled with the water-permeable material 13 having a medium grain size arranged below. Furthermore, when the net bag 12 filled with the very fine water-permeable material 13 is contacted, the behavior of water associated with the capillary phenomenon is utilized to control the permeation and water retention, and the rainwater can be freely guided in any direction, vertically, horizontally, or vertically.

[0027] In addition, although not shown in Figs. 1 and 2, a water permeability control sheet can be disposed on the bottom surface of the trench 11, specifically on the bottom surface or even deeper therefrom. This prevents the rainwater from seeping into the slope 10 through the trench 11 even in the unlikely event that the water-permeable and retentive material 13 in the net bag 12 disposed in the trench 11 cannot absorb the rainwater caused by a torrential rain or the like. This makes it possible to more reliably prevent the collapse of the site having the slope 10 due to the rainwater, and more reliably preserve the site. As the water permeability control sheet, for example, a general-purpose vinyl sheet or a nonwoven civil engineering sheet can be applied. If a water-impermeable vinyl sheet is used, the rainwater does not seep vertically, but can be moved horizontally to a lower level. In the case of a nonwoven civil engineering sheet, the speed of seepage into the ground can be controlled by changing the thickness or arranging the sheets in an overlapping manner.

[0028] Furthermore, in the slope conservation method of the present invention, a woven fence work 15 is provided at the base of the ditch 11. As a result, when the slope 10 is steep, even if the net bag 12 slides down inside the ditch 11, the net bag 12 will not be thrown out of the ditch 11, and it is possible to prevent the net bag 12 filled with the water-permeable retentive material 13 from being washed away with rainwater and being lost. On the other hand, when the slope 10 is gently sloping, it is possible to control rainwater and obtain the desired effect by forming a side ditch by bare digging without providing the woven fence work 15 and simply pouring the water-permeable material 13 into it.

[0029] As described above, in the slope conservation method of the present invention, the above operations can be carried out directly on-site, and can always be carried out under the best conditions by so-called on-site construction. In other words, the position, number, length, depth of the grooves 11 to be constructed on the slope 10 and / or the number, type (particle size of the water-permeable material) and layout of the net bags 12 to be installed can be optimized based on information on the soil and shape of the slope 10, information on the shape, position, and falling water of structures (steel towers, etc.) on the slope 10, and / or weather information such as the amount of rainfall.

[0030] In addition, the above optimization can also be performed by storing information obtained from the relationship between information on the soil and shape of the slope, information on the shape, position and falling water of structures (such as steel towers) on the slope and / or weather information such as rainfall, and the position, number, length and depth of the trenches to be constructed on the slope and / or the number, type (particle size of the water-retentive material) of the mesh bags to be placed and the layout, in a computer, and then determining the position, number, length and depth of the trenches to be constructed on any slope and / or the number, type (particle size of the water-retentive material) of the mesh bags to be placed and the layout by the computer performing calculations based on this information.

[0031] Specifically, information on the soil and three-dimensional shape of the slope 10, as well as the shape and position of structures on the slope 10 (for example, the presence or absence of a steel tower and its position) are first input into a computer (step S1). Next, based on information such as the annual precipitation at the location, the expected amount of water falling on the slope 10 and the expected amount of rainfall are input into the computer (step S2). Next, based on the information obtained in steps S1 and S2, the positions, number, length and depth of the grooves 11 to be constructed on the slope 10 are set to initial values, such as forming multiple rows of wide and deep grooves on a slope with a steep slope and a deep valley shape, and further the number, type (particle size of the water-permeable material) and layout of the net bags 12 to be placed in the grooves 11 are determined (step S3).

[0032] At this time, if the amount of water cannot be sufficiently attenuated in the grooves 11 and net bags 12, the weighting is updated again in step S3 by changing the coefficients of the formula, the positions and number of the grooves 11 are adjusted, and the optimum number of the net bags 12 is updated. This operation is repeated until the amount of water attenuates by 50% or more after 30 minutes has elapsed, and the positions and number of the grooves 11 and the number of the net bags 12 that satisfy the requirements are input to the computer as conditions sufficient to protect the slope 10 from rainwater, etc. (step S4).

[0033] Such conservation conditions are obtained for the types of soil and shape of various slopes 10 in step S1 described above, and for the shapes and positions of structures on the slopes 10, and also for the amount of water falling on the slopes 10 and the amount of rainfall in step S2, and input into the computer. Therefore, for any slope 10, appropriate conservation conditions can be selected from the conservation conditions stored in the computer based on information on the soil and shape of the slope 10, information on the shapes and positions of structures on the slope 10, and the amount of water falling on the slope 10 and the amount of rainfall, or based on optimal values ​​calculated from the selected conservation conditions, the position, number, length and depth of the trenches 11 to be constructed on the slope 10 can be obtained, and further the number, type (particle size of the water-permeable material) and layout of the net bags 12 to be disposed in the trenches 11 can be determined.

[0034] In other words, by performing machine learning from steps S1 to S4 using a computer, appropriate conservation conditions can be selected and applied to any slope 10.

[0035] In view of the above embodiment, the present application also includes the following inventions. [1] A slope preservation method characterized by forming a trench to guide running water on the slope of a site and placing a water-retaining material in the trench. [2] A slope preservation method as described in [1], in which the water-permeable material is a material made of a porous material, or a material obtained by kneading or premixing cement with a porous material and then spraying water on it to solidify it. [3] The slope preservation method according to [2], wherein the porous material is at least one selected from the group consisting of clinker ash, volcanic gravel, pumice, and bora soil. [4] A slope conservation method described in any one of [1] to [3], in which the water-permeable material is filled into a mesh bag having a predetermined size and shape and arranged continuously or at predetermined intervals within the trench. [5] A slope preservation method as described in [4], wherein the mesh bag has a mesh size of 1 mm to 4 mm and is an approximately rectangular bag shape with a width of 15 cm to 50 cm and a length of 30 cm to 100 cm. [6] A slope preservation method according to [4] or [5], wherein the mesh bag is filled with the water-permeable, water-retentive material classified according to particle size. [7] A slope conservation method described in any one of [4] to [6], wherein the mesh bag is made of a biodegradable material. [8] A slope preservation method according to any one of [4] to [7], in which a water-permeability control sheet is disposed or buried in the lowest layer of the trench or even deeper therein. [9] A slope conservation method described in any one of [4] to [8], in which a woven fence work is installed at the foot of the trench.

[10] A slope conservation method as described in any of [4] to [9], in which the position, number, length and depth of the grooves to be constructed on the slope and / or the number and type (particle size of the water-permeable material) of the mesh bags to be disposed are selected and layout are optimized based on information relating to the soil and shape of the slope, information relating to the shape, position and falling water of structures on the slope, and / or weather information such as rainfall.

[11] A program for a slope preservation method, characterized in that it causes a computer to perform calculations to select the position, number, length and depth of the grooves to be constructed on the slope and / or the number and type (particle size of the water-permeable material) of the mesh bags to be placed, and optimize the layout, based on information relating to the soil and shape of the slope, information relating to the shape, position and falling water of structures on the slope, and / or weather information such as rainfall. EXAMPLES

[0036] (Measurement of flow velocity attenuation by grain size) Tests were conducted for different particle sizes of clinker ash at inclination angles of 10 degrees and 30 degrees, with a rainfall equivalent to 48 mm for 1 hour. Figures 3 and 4 show the flow velocity reduction effect using clinker ash samples of 0-40 mm, 0-7 mm, and 5-7 mm, compared to no sample.

[0037] As shown in Figure 3, when the angle is 10 degrees, after 20 minutes, 0-40mm has attenuated by 69%, 0-7mm by 62%, and 5-7mm by 35%. 0-40mm is not drained for the first 10 minutes after the start. After that, it is slowly drained while retaining water. Also, the more the particle size range is narrowed, the less water is retained. The results of Figure 3 also show that clinker ash with a particle size of 0-40mm (raw ash) has a high flow velocity attenuation effect.

[0038] Also, as shown in Figure 4, when the angle is 30 degrees, the flow velocity attenuation effect after 20 minutes is 50% for 0-40mm and 37% for 5-7mm compared to no sample, and 0-40mm is 19% lower than the 10 degree inclination angle, but there is no difference for 5-7mm. On the other hand, it was found that the attenuation effect of 0-40mm clinker ash is 50% even when the inclination angle is increased to 30 degrees.

[0039] Tests were conducted for different particle sizes of clinker ash at inclination angles of 10 degrees and 30 degrees, with a rainfall equivalent to 1,000 mm for 1 hour. Figures 5 and 6 show the flow velocity reduction effect of clinker ash samples of 0-40 mm, 0-7 mm, and 5-7 mm compared to no sample.

[0040] As shown in Figure 5, when the angle was 10 degrees, 0-40mm had a damping effect of 44% after 5 minutes and 11% after 10 minutes compared to no sample, and 33% of the retained water was slowly discharged after 5 minutes. 0-7mm had a damping effect of 36% after 5 minutes and 10% after 10 minutes. Clinker ash 5-7mm had a damping effect of 4% after 5 minutes and 1% after 10 minutes, and almost all of the water passed through the floor surface as if it was crawling along the floor.

[0041] Furthermore, as shown in Figure 6, when the angle was 30 degrees, the 0-40mm sample was 16% after 5 minutes and 4% after 10 minutes compared to no sample, which is about 1 / 3 of the 10 degree inclination angle. The 5-7mm clinker ash sample was 8% after 5 minutes and 0% after 10 minutes, which suggests that the water temporarily held in the pores was drained by gravity after 5 minutes.

[0042] (Test for measuring flow velocity attenuation by stage) A comparison was made by using 0-40mm clinker ash and number of stages under conditions of rainfall equivalent to 34mm per hour and an inclination angle of 30 degrees. The attenuation effect 20 minutes after precipitation (Fig. 7) was 59% for one stage and 96% for two stages. Discharge stopped 26 minutes after the water was stopped for the one stage, but 45 minutes later for the two stages. The attenuation effect after 45 minutes was 54% for one stage and 76% for two stages. Two stages showed a large attenuation effect, and it was found that there was an effect of mitigating the flow velocity of concentrated flowing water in proportion to the amount of clinker ash used (Fig. 8). Also, no overflow occurred even at an inclination angle of 30 degrees.

[0043] The drainage volume from this test is shown in time series in Figure 9. The results clearly show that the second stage temporarily retains concentrated precipitation and slowly drains it away.

[0044] From the above, it can be seen that in order to preserve slopes, it is essential to control the damping effect by adjusting the particle size and number of layers of clinker ash.

[0045] (Field Test) <Verification test of drainage control using clinker ash at a tower site> Field tests were conducted at the sites of four steel towers. Clinker ash was selected based on the results of basic tests on porous materials, and in order to confirm its workability and effectiveness on site, it was installed on four steel towers with large inclination angles at the site of an ultra-high voltage steel tower, and a demonstration test of its drainage control effect was conducted. Several types of mesh bags were made of polyethylene with a mesh of 1 to 4 mm, width of 20 to 40 cm, and length of 20 to 100 cm, and were placed on slopes where running water is likely to concentrate. Cylindrical materials with a length of 90 cm and mesh of 4 mm and clinker ash grain size of 5 to 40 mm were placed on the top of the woven fence work, and the effect of dispersed drainage due to the permeability and water retention of the concentrated running water was confirmed. The results showed that the concentration of running water was alleviated, but the water retention effect was not large because the amount of water retention was less than that of raw ash, but the effect of preventing water concentration was confirmed by the state of the vegetation and topsoil below the installation (Fig. 10).

[0046] Based on the above results, the specifications of the net bags were changed. Materials with a width of 30 cm, length of 70 cm, and mesh of 1 mm, made of clinker ash with a particle size of 0 to 40 mm, were placed continuously on a single slope (Fig. 11). The results confirmed that the vegetation below was not washed away and was growing well due to the dispersed drainage effect. The woven fence work was placed on steep slopes where runoff is likely to concentrate. To disperse and drain concentrated runoff, two or more layers of clinker ash bags were used, so a method was devised that combines them with woven fence work with enhanced durability (Fig. 12).

[0047] Steel pipe piles 48.6mm in diameter and 1,100mm in length were driven into the woven fence at 50-70cm intervals, and inside of this, a plastic strip-shaped cross-woven net with iron wire reinforcing was placed with 14mm mesh, and then a nonwoven fabric sheet (civil engineering sheet) was placed on top, in an L shape at a height of 400mm. In the space between the woven fence net and the slope, polyethylene mesh bags 35cm x 60cm filled with porous material (coal ash) were stacked in three layers, which retained the water running from the top and allowed for dispersed drainage (runoff suppression), thereby protecting the vegetation and surface layer below the woven fence.

[0048] A follow-up survey was then conducted for one year. Rainfall data was taken from the Japan Meteorological Agency's observation station near the test site and the Ume Observatory in Saiki City, Oita Prefecture, and a time-lapse camera was installed to follow up the survey monthly. The results showed that the maximum rainfall was 479 mm in August 2021, with a maximum of 68 mm in one hour and a maximum of 15 mm in 10 minutes, but the vegetation and surface layer below the equipment were healthy. The camera showed that the running water from the main leg of the tower was concentrated and flowed into the woven fence and was absorbed. In addition, the progress of the survey showed that the topsoil was not exposed and the vegetation below the woven fence was thriving, indicating that the dispersion and drainage effect was apparent.

[0049] To date, permeable and water-retentive flat plates made from coal ash have been used as a measure against raindrops on steel towers, but a method was devised to prevent raindrop scouring by eliminating the manufacturing process and putting coal ash in a mesh bag, and a demonstration test was conducted. There are two methods: a material with a mesh of 4 mm and a clinker ash particle size of 5 to 40 mm, and a material with a mesh of 1 mm and a clinker ash particle size of 0 to 40 mm. Figure 13 shows a pattern using clinker ash of 0 to 40 mm, with artificial turf installed on the surface to mitigate the impact of raindrops and to improve the appearance. The results showed that both methods were easy to install, even on steeply sloping sites. One year later, there was no scouring or decline in vegetation due to raindrops or concentrated rainwater at the site.

[0050] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0051] 10 Slope 11 Groove 12 Net bag 13 Water-permeable substances 15 Knitted fence

Claims

1. A slope preservation method characterized by forming a trench on the slope of a site to guide running water and placing a water-permeable material in the trench.

2. 2. The slope preservation method according to claim 1, wherein the water-permeable material is a material made of a porous material, or a material obtained by kneading or premixing cement with a porous material, and then spraying water on the porous material to solidify it.

3. The slope preservation method according to claim 2, wherein the porous material is at least one selected from the group consisting of clinker ash, volcanic gravel, pumice, and bora soil.

4. 2. The slope preservation method according to claim 1, wherein the water-permeable and water-retentive substance is filled in a mesh bag having a predetermined size and shape, and is disposed in the trench continuously or at predetermined intervals.

5. The slope preservation method according to claim 4, wherein the mesh bag has a mesh size of 1 mm to 4 mm, and is an approximately rectangular bag shape having a width of 15 cm to 50 cm and a length of 30 cm to 100 cm.

6. 5. The slope preservation method according to claim 4, wherein the mesh bag is filled with the water-permeable and water-retentive substances classified according to particle size.

7. The slope preservation method according to claim 4, wherein the net bag is made of a biodegradable material.

8. 5. A slope preservation method according to claim 4, further comprising disposing or burying a water-permeability control sheet in the bottom layer of the trench or in a deeper layer thereof.

9. 5. A slope preservation method according to claim 4, further comprising providing a woven fence at the foot of the trench.

10. A slope conservation method as described in claim 4, in which the position, number, length and depth of the grooves to be constructed on the slope and / or the number and type (particle size of the water-permeable material) of the mesh bags to be disposed are selected and layout are optimized based on information related to the soil and shape of the slope, information related to the shape, position and falling water of structures on the slope and / or weather information such as rainfall.

11. A program for a slope conservation method, which is characterized by having a computer perform calculations to select the position, number, length and depth of the grooves to be constructed on the slope and / or the number and type (particle size of the water-permeable material) of the mesh bags to be arranged, and optimize the layout, based on information related to the soil and shape of the slope, information related to the shape, position and falling water of structures on the slope, and / or weather information such as rainfall.

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