JP7096789B2 - Slope impermeable structure and its construction method - Google Patents

Description

The present invention relates to a slope impermeable structure provided as a surface layer of a slope and a method for constructing the same.

As disclosed in Patent Documents 1 and 2, the slope formed by cutting or embankment should be stabilized by using concrete or the like in order to prevent the infiltration of rainwater that causes slope failure. Is being done.

For example, Patent Document 1 discloses that a water-impervious structure is provided on a surface layer by spraying concrete on a slope. Further, Patent Document 2 discloses a slope stabilizing work in which a vertical beam is constructed of reinforced concrete and the slope exposed between the vertical beams is covered with a greening spray material.

On the other hand, Patent Documents 3 and 4 describe that a material obtained by mixing steelmaking slag and blast furnace granulated slag is used as a simple pavement material for roads. Here, in order to use it as a road pavement, a material having a high binding force such as cement or asphalt is added so that ruts and wear are unlikely to occur due to the running of the vehicle, and the strength is increased.

Japanese Unexamined Patent Publication No. 2017-197934 Japanese Unexamined Patent Publication No. 2004-52533 Japanese Patent No. 5765125 Japanese Unexamined Patent Publication No. 2017-48625

However, the material cost of the binder such as cement and asphalt is high, and the construction cost increases particularly when the construction is performed on a long slope where the surface area of the slope is large.
Therefore, an object of the present invention is to provide a water-impervious structure for a slope having high impermeable performance and a method for constructing the same, in addition to being able to be constructed only with a relatively inexpensive material.

In order to achieve the above object, the slope impermeable structure of the present invention is a slope impermeable structure provided as the surface layer of the slope, and compacts a slag material obtained by mixing steelmaking slag and blast furnace granulated slag. It is characterized by compaction so that the density ratio is 90% or more.
Here, it is preferable to compact the slag material so that the compaction density ratio is 95% or more.

For example, the steelmaking slag has a particle size of 40 mm or less, and the blast furnace granulated slag may have a content of 5% by mass or more and 25% by mass or less with respect to the total amount of the slag material. Further, the thickness of the surface layer formed by the slag material can be 100 mm to 200 mm. Further, it is preferable that the water permeability coefficient of the surface layer formed by the slag material is 3.0 × 10 ^-6 m / s or less.

Further, the invention of the method for constructing the impermeable structure for the slope is a method for constructing the impermeable structure for the slope provided as the surface layer of the slope, in which a slag material obtained by mixing steelmaking slag and blast furnace granulated slag is laid on the slope. It is characterized in that it is compacted so that the compaction density ratio is 90% or more.

The impermeable structure of the slope of the present invention configured in this way is constructed by compacting a slag material, which is a mixture of steelmaking slag and blast furnace granulated slag, so that the compaction density ratio is 90% or more. To.

In short, since only the steelmaking slag and the blast furnace granulated slag generated in the steelmaking process are used, the material cost can be relatively low. Further, high impermeable performance can be ensured by compacting so that the compaction density ratio is 90% or more. In particular, by setting the compaction density ratio to 95% or more, the penetration rate of rainwater into the slope can be significantly reduced.

It is explanatory drawing which showed the structure of the impermeable structure of the slope of this embodiment. It is explanatory drawing which showed the outline of the ground model of the watering experiment which performed to confirm the effect of the impermeable structure of the slope of this embodiment. It is a figure explaining the relationship between the water content ratio, the dry density, and the hydraulic conductivity. It is a figure explaining the result of the watering experiment together with the comparative example, (a) is the graph which showed the time history of the penetration rate when the rainfall intensity is 20 mm / hr, and (b) is the penetration when the rainfall intensity is 90 mm / hr. It is a graph which showed the time history of a rate. It is a figure explaining the result of the watering experiment when the rainfall intensity is 20mm / hr, (a) is the graph which showed the time history of the saturation degree at the downstream point of a slope, (b) is the saturation degree at the center point of a slope. (C) is a graph showing the time history of the degree of saturation at the upstream point of the slope. It is a figure explaining the result of the watering experiment in the case of the rainfall intensity 90mm / hr, (a) is the graph which showed the time history of the saturation degree at the downstream point of the slope, (b) is the saturation degree at the center point of the slope. It is a graph showing the time history of.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially enlarged explanatory view showing the configuration of a water-impervious structure on a slope described in the present embodiment.
First, the overall configuration will be explained with reference to FIG. 1. On the slope S, the slope generated when excavating the ground, the embankment, the embankment, etc. by raising the soil on the foundation ground, etc. This applies to slopes that occur during embankment to construct.

In the following, an example will be described of a slope having a 1: 2.0 gradient, that is, an impermeable layer 1 having an impermeable structure for the slope, which is provided as a surface layer of the slope S inclined at an inclination angle of about 26 ° with respect to the horizontal. An impermeable layer 1 is provided on such a slope S in order to prevent the infiltration of rainwater into the inside of the slope S and the erosion of the surface, which cause the slope collapse.

The most required performance of the impermeable layer 1 is impermeable performance, and the smaller the permeability coefficient, the more preferable. Further, it is preferable that the impermeable layer 1 can be constructed only with a relatively inexpensive material without using an expensive material such as cement or asphalt.

Therefore, in the present embodiment, the impermeable layer 1 is formed of a slag material obtained by mixing steelmaking slag and blast furnace granulated slag. Steel slag such as steelmaking slag and blast furnace granulated slag is an industrial by-product generated in the steelmaking process, and it can be obtained at a relatively low price and can contribute to the reduction of environmental load by effectively using it.

Steelmaking slag and blast furnace granulated slag are composite materials containing calcium oxide, calcium silicate, iron (II) oxide, alumina and the like as main components, and have latent hydrohardness. In addition, steelmaking slag alone has weak water hardness and develops strength, but by mixing blast furnace granulation slag with steelmaking slag, steelmaking slag, which is a strong alkali, stimulates blast furnace granulation slag with even stronger water hardness. , Hydrate is formed to form a strong solidified body.

More specifically, the blast furnace granulated slag is stimulated by the alkali of the steelmaking slag, and silica (Si) and aluminum (Al) dissolve in water, causing a pozolan reaction with calcium (Ca) dissolved from the steelmaking slag. When lime silica-aluminum (CSAH: C = CaO, S = SiO ₂ , A = Al ₂ O ₃ , H = H ₂ O) -based hydrate is produced, it connects the interparticle gaps and at the same time creates interparticle voids. Caking occurs when filled. In addition, excess Ca ions in water react with carbonate ions in the air to simultaneously generate calcium carbonate (CaCO ₃ ) and consolidate.

In order to construct the impermeable layer 1 with a slag material obtained by mixing such steelmaking slag and blast furnace granulated slag, the slag material is spread on the slope S and water for promoting water hardness is sprayed on the slag material. Then, it is formed by rolling and compacting with a compactor or the like.

As the steelmaking slag, for example, a steelmaking slag having a particle size of 40 mm or less that has passed through the mesh by sieving with a sieve having a mesh size of 40 mm can be used. Further, as the blast furnace granulated slag, glassy granular slag that has been rapidly cooled by injecting pressurized water onto the molten blast furnace slag can be used.

The blast furnace granulated slag is mixed so that the content of the blast furnace granulated slag is, for example, 5% by mass or more and 25% by mass or less with respect to the total amount of the slag material. On the other hand, the content of the steelmaking slag with respect to the total amount of the slag material is 95% by mass or less and 75% by mass or more. In short, the total amount of slag material is a combination of steelmaking slag and blast furnace granulated slag.

On the other hand, in order to exert the impermeable performance required for the impermeable layer 1, it is necessary to compact the road pavement or more. That is, in road pavement, the impermeable performance may not be so important as there is a pavement that actively infiltrates rainwater into the base side like a permeable pavement, but in order to stabilize the slope S. Is required to have a water-impervious performance equal to or higher than a predetermined value.

Therefore, in the following, the relationship between the degree of compaction and the water permeability will be described, and the impermeable structure suitable for the impermeable layer 1 provided as the surface layer of the slope S will be described. First, a watering experiment conducted to confirm the impermeable performance will be described with reference to FIGS. 2 to 6.

In this watering experiment, in order to understand the difference in impermeable performance depending on the construction conditions (water content ratio, dry density) of the slope S (slope) using the above-mentioned slag material, the ground of the slope that simulates the vicinity of the slope A model (see Fig. 2) was prepared and carried out.

In carrying out this watering experiment, it was decided to carry out a hydraulic conductivity test of the specimen of slag material with different water content ratio and density (dry density), and to grasp the change of the hydraulic conductivity depending on the water content ratio and the magnitude of the dry density. First, as shown in FIG. 3, a water permeability test of a specimen having a compaction density ratio of 90% to 99% in a water content ratio of 7% to 11% was performed. Here, the compaction density ratio (Dc) is a ratio between the dry density of the sample and the maximum dry density, and is an index indicating the degree of compaction, which is sometimes referred to as “compacting degree”.

As a result of a series of tests, it was found that the permeability coefficient decreases as the water content ratio increases and approaches 11% of the optimum water content ratio, and that the smaller the compaction density ratio (dry density), the smaller the permeability coefficient is obtained. In particular, when the optimum water content ratio is close to 11% and the compaction density ratio is as large as 99%, it was confirmed that the hydraulic conductivity becomes an extremely small value of 1.0 × 10 ^-8 m / s or less.

In addition, a hydraulic conductivity test was conducted on a specimen with a water content ratio higher than the optimum water content ratio of a slag material specimen with a different water content ratio, and the change in the hydraulic conductivity due to the magnitude of the water content ratio in a range larger than the optimum water content ratio. I decided to figure out. As for the preparation density of this specimen, three types of specimens having a compaction density ratio of 90% and a water content ratio of 11%, 12%, and 13% were prepared.

As a result of the permeability test on these three types of specimens, the specimen with a water content of 11% was 1.11 × 10 ^-5 (m / s), and the specimen with a water content of 12% was 1.76 × 10 ^-5 . A hydraulic conductivity k of 2.24 × 10 ^-5 (m / s) was obtained for the specimen with (m / s) and a water content of 13%. In short, it was found that the hydraulic conductivity k is almost the same regardless of the water content ratio, and the influence of the hydraulic conductivity on the hydraulic conductivity k is small in a range larger than the optimum hydraulic conductivity.

FIG. 2 shows an outline of the ground model used in the watering experiment conducted to confirm the effect of the impermeable structure on the slope of the present embodiment. This ground model has a structure in which a slope work using slag material is laid on a slope ground (made of Tohoku Sisago No. 6) that imitates a slope S with a layer thickness of 120 mm.

The impermeable layer 1 has a layer thickness of 150 mm and a slope length of about 1700 mm. When the water-impervious layer 1 is installed on the actual slope S, the layer thickness is preferably about 100 mm to 200 mm. In addition, a transparent horizontal plate was installed at the position on the slope S on the slope side (downstream side of the surface water), and the vicinity of the plate was set as an opening that was not the slope ground so that the amount of surface water could be measured. Further, on the slope ground imitating the slope S, a plurality of drainage paths are provided in the direction orthogonal to the lower surface so that the permeation amount can be measured.

Then, after the construction of the ground model, the soil tank was tilted at 26 degrees in order to simulate the 1: 2.0 slope S (see Fig. 1). In addition, soil moisture meters and pore water pressure meters were installed at intervals of 300 mm on the slope ground. Here, the soil moisture meter is labeled as PWP01, PWP02, ... in order from the glue tail side (downstream side of the surface water), and the pore water pressure meter is labeled as M01, M02, ... in order from the glue tail side. Signed.

The watering experiment was carried out in multiple patterns with different rainfall intensities. Specifically, watering experiments were conducted when the rainfall intensity was 20 mm / hr and when the rainfall intensity was 90 mm / hr. Further, the simulation of the impermeable layer 1 was performed in a plurality of cases (Case1-Case3) in which the composition of the slag material as a material was the same and the degree of compaction was changed.

The composition of the slag material was such that the content of steelmaking slag was 80% by mass (particle size 25 mm or less) and the content of blast furnace granulated slag was 20% by mass (particle size 2 mm). The initial water content was 11.0% in all cases.

Case 1 is a case compacted so that the drying density is 2.263 (g / cm ³ ). This degree of compaction is 99% in terms of compaction density ratio (Dc) expressed as a ratio to the maximum dry density. The permeability coefficient k measured by the indoor permeability test of Case 1 was 9.04 × 10 ^-9 (m / s).

Case 2 is a case compacted so that the drying density is 2.057 (g / cm ³ ). This degree of compaction is 90% in terms of the compaction density ratio (Dc) expressed as a ratio to the maximum dry density. The permeability coefficient k measured by the indoor permeability test of Case 2 was 1.11 × 10 ^-5 (m / s).

In addition, Case 3 is a case compacted to a dry density of 2.171 (g / cm ³ ). This degree of compaction is 95% in terms of the compaction density ratio (Dc) expressed as a ratio to the maximum dry density. The permeability coefficient k measured by the indoor permeability test of Case 3 was 3.19 × 10 ^-6 (m / s).

In the watering experiment, water was sprinkled from the top of the inclined ground model to a rainfall intensity of 20 mm / hr or 90 mm / hr, and the amount of surface water discharged from the position of the transparent horizontal plate and the infiltration discharged from the lower surface side of the slope ground. The amount, the detected value of the soil moisture meter and the pore water pressure meter were measured.

FIG. 4-Fig. 6 shows the experimental results for each rainfall intensity. Here, for comparison, the experimental results when the impermeable layer 1 is not provided (no countermeasures) are also shown. First, FIG. 4 shows the time history of the permeation rate when the rainfall intensity is 20 mm / hr (FIG. 4 (a)) and when the rainfall intensity is 90 mm / hr (FIG. 4 (b)).

Here, the permeation rate (%) is a value indicating the ratio of the permeation amount to the total of the surface water amount and the permeation amount, and is calculated by the formula of permeation rate = permeation amount / (surface water amount + permeation amount). Looking at these results, it was confirmed that the penetration rate was hardly observed in Case 1 at any rainfall intensity, and that the penetration into the slope S did not occur.

On the other hand, Case 2 showed almost no water-blocking effect, and the penetration rate was about the same as that of no measures. On the other hand, in Case 3 with a compaction density ratio of 95%, complete impermeable water could not be achieved, but it can be said that considerable rainfall did not penetrate and flowed down as surface water (surface water).

Therefore, it was decided to set the rainfall intensity to 20 mm / hr and verify the difference depending on the position of the slope S in each case. Here, the rainfall intensity of 20 mm / hr is classified as "strong rain" in the forecast term and "rainfall" in the image received by humans, according to the classification of "rain intensity and how to get off" by the Japan Meteorological Agency.

FIG. 5 is a graph showing the time history of the degree of saturation (%), FIG. 5 (a) shows the degree of saturation at the downstream point of the slope S (point PWP01 in FIG. 2), and FIG. 5 (b) shows the degree of saturation. The degree of saturation at the central point of S (point PWP03 in FIG. 2) is shown, and FIG. 5 (c) shows the degree of saturation at the upstream point of slope S (point PWP06 in FIG. 2).

Looking at these results, at the downstream point (Fig. 5 (a)), the degree of saturation was low in the case of no countermeasures, and the case where the slope work was constructed with the impermeable layer 1 made of slag material (Case1-Case3). Then, it can be seen that the degree of saturation is relatively high.

This is because, without countermeasures, rainfall permeates the inside of the slope S (inside the embankment) almost evenly, whereas in the case where the impermeable layer 1 is constructed, the surface water flowing down the surface of the impermeable layer 1 flows down. It is thought that this is because the number increases and a part of it penetrates near the downstream point (glue). In short, it is considered that the inflow in the glue butt will be larger than in the case of no measures.

On the other hand, at the central point (FIG. 5 (b)), the saturation of Case 2 was the same as that of no countermeasures, and in Case 1 and Case 3, there was almost no increase in saturation, and the penetration rate shown in FIG. 4 was observed. Similar to the result of, the result showed no increase with the passage of time.

At the upstream point (Fig. 5 (c)), an increase in saturation was confirmed in the order of Case1, Case3, Case2, and no countermeasures, and at the downstream and central points, penetration equal to or higher than that without countermeasures was confirmed. It was confirmed that Case 2 also had a certain impermeable effect at the upstream point.

FIG. 6 shows the results of verifying the difference depending on the position of the slope S in each case by the time history of the saturation degree (%), assuming that the rainfall intensity is 90 mm / hr. Here, the rainfall intensity of 90 mm / hr is classified as "rain intensity and how to get off" by the Japan Meteorological Agency. I feel afraid. "

Then, in the graph of FIG. 6 showing the time history of the saturation degree, FIG. 6A shows the saturation degree at the downstream point of the slope S (PWP01 point of FIG. 2), and FIG. 6B shows the center of the slope S. The degree of saturation at the point (PWP03 point in FIG. 2) is shown.

Looking at these results, at the downstream point (Fig. 6 (a)), the results were similar to those for the rainfall intensity of 20 mm / hr, but at the central point (Fig. 6 (b)), the saturation level was also in Case 2. It was confirmed that the increase in the amount of water was suppressed.

When the inflow is very large, as in the case of a rainfall intensity of 90 mm / hr classified as "heavy rain", a certain amount is drained as surface water and the saturation inside the slope S increases. It is considered to have been suppressed.

By the way, since the slag material is alkaline, the pH of each case was also measured for reference. In each case, the pH of surface water was about 7.8-8.5 on average, and the pH of osmotic water was about 8.2-11.7. However, as the carbonation of the slag material proceeds from the surface, these pH gradually decrease with the passage of time.

Next, the operation of the impermeable structure of the slope of the present embodiment and the method of constructing the same will be described.
In the water-impervious structure of the slope of the present embodiment configured as described above, a slag material obtained by mixing steelmaking slag and blast furnace granulated slag is spread evenly on the slope S, and the compaction density ratio becomes 90% or more. It is built by compacting it like this.

In short, since only the steelmaking slag and the blast furnace granulated slag generated in the steelmaking process are used, the material cost can be relatively low. In addition, by compacting so that the compaction density ratio is 90% or more, high impermeable performance that does not increase the saturation of at least the vicinity of the glue shoulder of the slope S (upstream side of surface water) should be ensured. Can be done.

Further, when the rainfall intensity is high, it is possible to suppress an increase in the degree of saturation not only in the vicinity of the shoulder of the slope S but also in the vicinity of the center. Further, by setting the compaction density ratio to 95% or more, the penetration rate of rainwater into the slope S can be significantly reduced.

In such an impermeable layer 1, a slag material having a steelmaking slag having a particle size of 40 mm or less and a blast furnace granulated slag content of 5% by mass or more and 25% by mass or less based on the total amount is compacted by rolling compaction. It can be built by.

Further, by setting the thickness of the impermeable layer 1 formed of the slag material to about 100 mm to 200 mm, the desired impermeable performance can be obtained while suppressing the material cost. In short, by compacting the impermeable layer 1 so that the permeability coefficient k is 3.0 × 10 ^-6 m / s or less, rainwater permeates the inside of the slope S such as embankment or ground and induces collapse. Can be prevented.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes to the extent that the gist of the present invention is not deviated are made in the present invention. Included in the invention.

For example, in the above-described embodiment, the slope S having a slope of 1: 2.0 has been described as an example, but the present invention is not limited to this, and the present invention is also applied to embankments and cuts having slopes of any slope. Can be applied.

S slope 1 Impermeable layer (impermeable structure of slope)

Claims (10)

It is a water-impervious structure of the slope provided as the surface layer of the slope.
A water-impervious structure on a slope characterized by compacting a slag material, which is a mixture of steelmaking slag and blast furnace granulated slag, so that the compaction density ratio is 90% or more. The water-impervious structure for a slope according to claim 1, wherein the slag material is compacted so that the compaction density ratio is 95% or more. The invention according to claim 1 or 2, wherein the steelmaking slag has a particle size of 40 mm or less, and the blast furnace granulated slag has a content of 5% by mass or more and 25% by mass or less with respect to the total amount of the slag material. Impermeable structure on the slope of. The water-impervious structure for a slope according to any one of claims 1 to 3, wherein the surface layer formed of the slag material has a thickness of 100 mm to 200 mm. The water-impervious structure for a slope according to any one of claims 1 to 4, wherein the water permeability coefficient of the surface layer formed of the slag material is 3.0 × 10 ^-6 m / s or less. It is a method of constructing a water-impervious structure on a slope provided as the surface layer of the slope.
A method for constructing a water-impervious structure on a slope, characterized in that a slag material obtained by mixing steelmaking slag and blast furnace granulated slag is spread evenly on the slope and compacted so that the compaction density ratio is 90% or more. The method for constructing a water-impervious structure for a slope according to claim 6, wherein the slag material is compacted so that the compaction density ratio is 95% or more. 6. How to build an impermeable structure on the slope of the slag. The method for constructing a water-impervious structure for a slope according to any one of claims 6 to 8, wherein the surface layer formed of the slag material has a thickness of 100 mm to 200 mm. The method for constructing a water-impervious structure for a slope according to any one of claims 6 to 9, wherein the water permeability coefficient of the surface layer formed of the slag material is 3.0 × 10 ^-6 m / s or less. ..

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