JP2021178900A - Mud-formation preventive material, and method for constructing water-shielding layer - Google Patents

Abstract

To provide a mud-formation preventive material and a method for constructing water-shielding layer that can economically prevent mud-formation of bentonite mixed soil constituting water-shielding layer and laid in layers.SOLUTION: Provided is a mud-formation preventive material that prevents bentonite mixed soil layer laid by rolling and compacting bentonite mixed soil sprinkled on the ground from mud-formation, and includes an asphalt emulsion and an emulsion dilution solution for diluting the asphalt emulsion, and in which the emulsion dilution solution is obtained by adding and dissolving a sedimentation suppression material that is nonionic and imparts viscosity to water, in water.SELECTED DRAWING: Figure 1

Description

The present invention relates to a mud-forming preventive material for preventing mud formation of bentonite mixed soil laid in a layer on the ground, and a method for constructing an impermeable layer using the mud-forming prevention material.

Conventionally, in the waste disposal site constructed in the ground, in order to prevent rainfall from becoming leachate containing harmful substances through the waste layer and spreading to the surrounding ground and contaminating the soil, the surrounding area An impermeable layer is provided between the ground and the ground. In particular, soil impermeable is often used at the bottom of waste disposal sites.

Soil impermeable is an impermeable work using bentonite mixed soil, and bentonite mixed soil uses locally generated soil or purchased sand as the base material, and the blending amount designed based on the results of laboratory tests etc. on this base material. Bentonite is mixed and hydrated. Then, the bentonite mixed soil is sprinkled on the ground, compacted and compacted, and laid in a layered manner to obtain a high water-impervious performance to the extent that the leachate containing the above-mentioned harmful substances can be contained.

Such an impermeable layer is generally constructed by the following procedure. First, bentonite mixed soil designed to ensure the desired impermeable performance is manufactured and laid in layers with respect to the target area on the ground. After the laying is completed, the surface of the bentonite mixed soil laid in layers is covered with a waterproof sheet such as a civil engineering sheet or a vinyl sheet and cured.

Curing with a waterproof sheet suppresses quality deterioration such as swelling and mud formation due to contact of bentonite mixed soil with water such as rainfall during the period until the impermeable sheet is laid on the surface of bentonite mixed soil. Do to do. However, not only the covering work using the waterproof sheet is complicated, but also rainwater easily leaks from the gap of the waterproof sheet. In the case of water leakage, it took a lot of time and effort to strip off the muddy part and lay the bentonite mixed soil again.

Under such circumstances, for example, Patent Document 1 discloses a method of forming an asphalt film by changing the work of covering the surface of the bentonite mixed soil laid in a layer with a waterproof sheet and curing it. Specifically, the bentonite mixed soil is spread to a predetermined thickness, spread to a substantially uniform thickness using a finisher, and then a water-impervious sheet forming material such as asphalt emulsion is sprayed on the surface of the bentonite mixed soil. , Form an impermeable sheet made of asphalt film.

Japanese Unexamined Patent Publication No. 2000-328544

According to the method of Patent Document 1, a water-impervious sheet made of an asphalt film can be formed only by directly spraying the water-impervious sheet-forming material on the surface of the bentonite mixed soil. Workability can be greatly improved.

The asphalt emulsion used as such an impermeable sheet forming material is diluted with water and used when sprayed on the surface of the bentonite mixed soil. However, in many cases, the asphalt emulsion diluted with water is not uniformly dispersed in water, for example, a part of the asphalt emulsion is settled.

Then, the asphalt film formed by spraying on the surface of the bentonite mixed soil has a thin portion in which the film thickness is not uniform, and rain leaks to the bentonite mixed soil through this thin portion. It can lead to mud. In order to prevent such a phenomenon, the amount of the asphalt emulsion added to water had to be increased, which was inferior in economic efficiency.

The present invention has been made in view of the above problems, and its main purpose is to prevent mud formation, which can economically prevent the mud formation of bentonite mixed soil laid in layers on the ground. It is to provide the construction method of the impermeable layer using the material and the material for preventing mud formation.

In order to achieve such an object, the mud-preventing material of the present invention is a mud-preventing material for preventing mud-forming of the bentnite layer laid by compacting and compacting the bentonite mixed soil sprinkled on the ground, and asphalt. The emulsion is provided with an emulsion diluting solution for diluting the asphalt emulsion, and the emulsion diluting solution is obtained by adding and dissolving a sedimentation inhibitor which is nonionic and imparts viscosity to water to water. It is characterized by.

The mud-forming preventive material of the present invention is characterized in that the sedimentation inhibitor is guar gum.

The mud-forming preventive material of the present invention is characterized in that the sedimentation inhibitor is added in an amount of 0.3% by weight or more and 2.0% by weight or less with respect to water.

According to the anti-muddy material of the present invention, it is prepared by diluting an asphalt emulsion with an emulsion diluted solution in which a nonionic sedimentation inhibitor is added to water and dissolved. As a result, even when a cationic emulsion is used as the asphalt emulsion, the phenomenon that the asphalt component is decomposed and solidified does not occur, and the asphalt emulsion can maintain a uniformly dispersed and homogeneous state. It will be possible.

Therefore, when the anti-mud removal material is sprayed on the surface of the bentonite layer, a high-quality anti-mud formation film having a substantially uniform layer thickness without unevenness can be formed. Therefore, it is possible to exert a high mud prevention effect on the bentonite layer while suppressing the amount of spraying per ^{1 m 2 of} the construction target area to a small amount.

Further, since the sedimentation inhibitor has a property of imparting viscosity to water, not only the sedimentation of the asphalt emulsion can be suppressed, but also the viscosity can be imparted to the mud-forming inhibitor. As a result, when the mud-forming preventive material is sprayed on the surface of the bentonite layer, it adheres well to the bentonite layer, and it is possible to suppress the phenomenon of water leakage in the gap between the two.

Further, if guar gum, which is generally used as a thickening material, is used as the sedimentation inhibitor, a mud-forming preventive film can be formed at low cost and with a small amount of addition, and the construction cost can be significantly reduced.

The method for constructing the impermeable layer of the present invention is a method for constructing the impermeable layer using the anti-muding material of the present invention, in which bentonite mixed soil is sprinkled on the ground and compacted to lay the bentonite layer. It is characterized by comprising a step of coating the surface of the bentonite layer with a mud-forming preventive film formed of the mud-forming preventive material.

According to the method for constructing the mud-made impermeable layer of the present invention, no special equipment is required and complicated work is not required. Therefore, the mud of the bentonite layer is muddy while improving the workability, shortening the construction period and reducing the construction cost. It is possible to prevent the formation of water and provide a high-quality impermeable layer.

According to the present invention, it is possible to economically prevent the muddyization of bentonite mixed soil laid in layers on the ground.

It is a figure which shows the outline of the impermeable layer in embodiment of this invention. It is a figure which shows the construction procedure of the impermeable layer in embodiment of this invention. It is a figure which shows the result of the evaluation experiment about the stability of the asphalt emulsion in embodiment of this invention. It is a figure which shows the composition of the simulated bentonite mixed soil in embodiment of this invention. It is a figure which shows the procedure of the confirmation experiment of the mud formation prevention effect in embodiment of this invention. It is a figure which shows the confirmation experiment result of the mud formation prevention effect in embodiment of this invention.

The details of the method of constructing the mud-decomposing preventive material and the impermeable layer of the present invention will be described below with reference to FIGS. 1 to 6 by taking as an example the impermeable layer provided between the waste disposal site and the ground. do. Prior to this, first, the waste disposal site and the impermeable layer will be described.

As shown in FIG. 1, in the waste disposal site 1 constructed in the ground, an impermeable layer 2 adopting soil impermeable is constructed on the bottom and the side surface of the excavated portion of the ground G, and the impermeable layer 2 is constructed. Waste 3 is stored inside the enclosure.

The impermeable layer 2 that employs soil impermeable has a bentonite mixed soil layer 21 laid on the ground G and a mud-preventing film 22 that covers the surface of the bentonite mixed soil layer 21, and the bentonite mixed soil layer 21. 2 is a bentonite mixed soil 211 sprinkled on the ground, which is compacted by rolling so as to have a uniform thickness, as shown in FIGS. 2 (a) and 2 (b).

The bentonite mixed soil 211 is produced, for example, by adding bentonite to soil such as locally generated soil and mixing it at a construction site. Further, the blending amount of bentonite is designed after confirming in an indoor test an amount capable of achieving the impermeable performance required for the impermeable layer 2. When producing the bentonite mixed soil 211, a blending amount of bentonite exceeding this design value is added.

The mud formation prevention film 22 is provided to prevent the bentonite mixed soil layer 21 from becoming mud due to water supply caused by, for example, rainfall, and is made of an asphalt film. As shown in FIG. 2C, the asphalt film is formed by decomposing the asphalt emulsion As of the mud-forming preventive material 221 sprayed on the surface of the bentonite mixed soil layer 21 and solidifying the asphalt content.

≪Mudification prevention material≫
As shown in FIG. 1, the mud-forming preventive material 221 is prepared by diluting the asphalt emulsion As with the emulsion dilution solution 4.

Asphalt emulsion As is an emulsified product in which asphalt is dispersed in fine particles in water containing an emulsion, and there are various types, but in this embodiment, a cationic emulsion is adopted. Cationic emulsions are used, for example, for tack coats that adhere to each layer of asphalt pavement. When sprayed, they decompose into water and asphalt before the water evaporates, and quickly form an asphalt film. Are known.

Although such a cationic emulsion can be diluted with water, it tends to settle in water and is not uniformly dispersed in many cases. Therefore, in the mud-forming preventive material 221, when diluting the asphalt emulsion As, the emulsion diluting solution 4 is used instead of water.

The emulsion diluting solution 4 can not only suppress the sedimentation of the asphalt emulsion As, but also impart viscosity to the mud-forming preventive material 221 so as to be familiarly adhered to the surface of the bentonite mixed soil layer 21 when sprayed or sprayed. The one is preferable. Further, even when a cationic emulsion is used as the asphalt emulsion As, it is preferable that the asphalt emulsion can be uniformly dispersed without sedimentation.

The cationic emulsion used as the asphalt emulsion As is positive ion (cationic). Therefore, in the emulsion diluting solution 4, a nonionic material that can be dissolved in water to impart viscosity and does not ionize when dissolved in water is adopted as the sedimentation inhibitor 5, and this is used as water. The liquid is prepared by adding to and dissolving.

Examples of the sedimentation inhibitor 5 include ethylene glycol, polyvinyl alcohol, guar gum and the like. Guar gum is a nonionic neutral polysaccharide obtained from the seeds of the annual plant guar, and is used as a thickener in various fields.

The following experiment was conducted in order to evaluate the stability of the asphalt emulsion As when the mud-forming preventive material 221 was prepared by using these three kinds of materials as the sedimentation inhibitor 5.

<Evaluation experiment on the stability of asphalt emulsion>
First, each of the above three types of materials was adopted as the sedimentation inhibitor 5, dissolved in water and mixed to prepare an emulsion diluted solution 4. The emulsion dilution solution 4 and the asphalt emulsion As were put into a 100 ml graduated cylinder with a stopper so that the asphalt emulsion As was diluted 16 times, and stirred up and down to prepare a mud-preventing material 221.

In this experiment, as shown in FIG. 3, two types of anti-muddying materials 221 prepared by changing the solution concentration of the emulsion diluted solution 4 were prepared with ethylene glycol (2 types), polyvinyl alcohol (4 types), and guagam (5 types). A total of 11 types of emulsion diluted solutions 4 were prepared.

Further, as a comparative example, xanthan gum and CMC (Carboxy Methyl Cellulose), which are anionic materials, were used instead of the sedimentation inhibitor 5, and this was added to water to prepare a diluted emulsion for comparison. Further, the asphalt emulsion As was added to the diluted solution of the comparative emulsion and stirred to prepare a material for preventing mud formation for comparison.

As shown in FIG. 3, these comparative mud-preventing materials were prepared by changing the solution concentration of the comparative emulsion diluted solution, and 3 types of CMC and 3 types of xanthan gum were prepared, for a total of 6 types. .. The 11 types of mud-preventing materials 221 and 6 types of comparative mud-preventing materials prepared in this way were allowed to stand for 7 days each, and the separated state of asphalt and the state of the supernatant water were visually observed.

Looking at FIG. 3, sediments are present in all of the comparative mud formation preventive materials. This is because both xanthan gum and CMC are anionic materials, so when dissolved in water, the portion with a hydrophobic group is ionized into negative (negative) ions. It can be presumed that this reacts with the positive (cationic) ions of the cationic emulsion adopted as the asphalt emulsion As, and the asphalt content is decomposed, solidified, and settled.

On the other hand, when ethylene glycol is used as the sedimentation inhibitor 5, the solution concentration is 20% by volume or more, the solution concentration of polyvinyl alcohol is 0.1% by weight or more, and the solution concentration of guar gum is 0.3% by weight or more. As is stably dispersed in the emulsion diluted solution 4. Therefore, it can be said that ethylene glycol, polyvinyl alcohol, and guar gum are all materials that can be adopted as the sedimentation inhibitor 5.

However, polyvinyl alcohol is inferior in terms of workability because it needs to be heated during the work of dissolving it in water. Further, when ethylene glycol is used, the solution concentration of the emulsion diluted solution 4 must be 20% by volume or more, which is inferior in economic efficiency from the viewpoint of material cost.

Therefore, the material used for the sedimentation inhibitor 5 can be completely dissolved in cold water, and the asphalt emulsion As can be dispersed in the emulsion diluted solution 4 even if the solution concentration is as small as at least 0.3% by weight. Guar gum is suitable. Therefore, the following experiment was conducted in order to confirm the mud formation prevention effect of the mud formation prevention material 221 prepared by adopting guar gum for the sedimentation suppression material 5.

<Experiment to confirm the effect of preventing mud formation>
In the experiment, first, the sedimentation inhibitor 5 using guar gum is added to water to prepare an emulsion diluted solution 4 having a solution concentration of 0.5% by weight. Next, the emulsion dilution solution 4 and the asphalt emulsion As are mixed and stirred to prepare a mud-forming preventive material 221 having a dilution ratio of the asphalt emulsion As twice.

On the other hand, a simulated base material is prepared, and the simulated bentonite mixed soil 211'is prepared by mixing and stirring so that the bentonite and the simulated base material have a dry weight ratio of 15:85. Quartz sand was used as the simulated base material, and the particle size was adjusted by mixing No. 3 silica sand to No. 9 silica sand with the composition shown in FIG. The prepared simulated bentonite mixed soil 211'was hydrated so as to have an optimum water content of 12%, and mixed until homogeneous.

As shown in FIG. 5A, this hydrated simulated bentonite mixed soil 211'was dropped into a cylindrical acrylic mold 6 and had a compaction degree equivalent to 90% (dry density 1.619 g / cm ³ ). I squeezed it to be. The work of dropping the simulated bentonite mixed soil 211'on the acrylic mold 6 and tamping it was performed in a plurality of times, and the height of the simulated bentonite mixed soil 211'was adjusted to match the height of the upper surface of the acrylic mold 6.

As shown in FIG. 5B, the mud-forming preventive material 221 prepared in advance was uniformly applied to the surface of the simulated bentonite mixed soil 211'filled with the acrylic mold 6 thus prepared to prepare a specimen. In this experiment, as shown in FIG. 6, three types of specimens having different coating amounts of the mud-forming preventive material 221 were prepared.

Further, as a comparative example, a comparative mud-forming preventive material was prepared by diluting the asphalt emulsion As in water twice. A specimen was prepared by uniformly applying this to the surface of the simulated bentonite mixed soil 211'prepared as described above. In this case as well, as shown in FIG. 6, three types of specimens having different amounts of the comparative mud-forming preventive material were prepared.

As shown in FIG. 5 (c), for each of the six types of specimens prepared as described above, a tubular water tank 7 having the same inner diameter as the acrylic mold 6 and having no bottom is formed into an acrylic mold. It was installed on the upper part of No. 6 and tap water W'was injected into the water tank 7. As a result, the surfaces of the mud-forming preventive material 221 and the comparative mud-forming preventive material are in contact with the tap water W'in the water tank 7, respectively.

After allowing to stand for 2 weeks in this state, as shown in FIG. 5D, the tap water w'in the water tank 7 is drained and the water tank 7 is removed, and the simulated bentonite mixed soil 211'in the acrylic mold 6 is removed. The amount of swelling h was measured. The swelling amount h was grasped by measuring the height h at which the simulated bentonite mixed soil 211'was raised from the upper surface of the acrylic mold 6.

Looking at FIG. 6, swelling was observed in the simulated bentonite mixed soil 211'in all the specimens coated with the comparative mud-forming inhibitor obtained by diluting the asphalt emulsion As with water. In particular, at 0.65 L / m ² (Comparative Example 1), which has the smallest coating amount, swelling of about 2 mm is observed.

This is because the asphalt emulsion As is not uniformly dispersed when diluted with water, and as shown in the image of FIG. 6, the layer thickness of the comparative mud-preventing film 22'formed after the application of the comparative mud-preventing material. Is prone to unevenness. Therefore, it can be presumed that tap water w'leaks from the thin layer portion and causes swelling in the simulated bentonite mixed soil 211'.

On the other hand, in the mud-forming preventive material 221 produced by using guar gum as the sedimentation inhibitor 5, the simulated bentonite mixed soil 211'does not swell regardless of the coating amount. In particular, it can be seen that even with a small coating amount of about 0.6 L / m ² (Example 1), high impermeable performance is exhibited and the simulated bentonite mixed soil 211'is prevented from becoming muddy.

By adopting and diluting the emulsion diluting solution 4, the asphalt emulsion As is uniformly dispersed and becomes a uniform state, and as shown in the image of FIG. 6, the mud-degrading preventive material 221 is applied. It can be presumed that the formed mud-forming preventive film 22 is due to the formation of a uniform layer thickness with few irregularities.

≪Construction method of impermeable layer≫
A method of constructing the impermeable layer 2 using the mud-forming prevention material 221 using guar gum as the sedimentation suppressing material 5 will be described below with reference to FIG.

First, bentonite mixed soil 211 is manufactured by adding and mixing an amount of bentonite capable of achieving the impermeable performance required for the impermeable layer 2 with earth and sand such as locally generated soil at the construction site. Further, guar gum is used as the sedimentation inhibitor 5 to prepare an emulsion diluting solution 4, and the asphalt emulsion As is diluted with this emulsion diluting solution 4 to prepare a mud-forming preventive material 221.

At this time, the solution concentration of the emulsion dilution solution 4 is preferably about 0.3 to 2.0% by weight, and the dilution ratio of the asphalt emulsion As is preferably about 2 to 4 times. If the solution concentration of the emulsion diluted solution 4 is less than 0.3% by weight, the asphalt emulsion As may settle, and if it exceeds 2.0% by weight, the solubility of guar gum is inferior and the viscosity becomes excessive. There is a risk of affecting the workability when spraying the mud-forming preventive material 221.

Next, as shown in FIG. 2A, the bentonite mixed soil 211 is sprinkled onto the ground G in the construction target area, and then the bentonite mixed soil 211 is compacted and tightened as shown in FIG. 2B. Perform consolidation. As a result, the bentonite mixed soil 211 forms a dense bentonite mixed soil layer 21 having a uniform layer thickness and a small hydraulic conductivity.

After that, as shown in FIG. 2C, the mud-preventing material 221 is sprayed or sprayed on the surface of the bentonite mixed soil layer 21 and cured for a predetermined period. Then, the asphalt component separated from the mud formation prevention material 221 is solidified, and the mud formation prevention film 22 which is an asphalt film is formed on the surface of the bentonite mixed soil layer 21. As a result, the impermeable layer 2 composed of the bentonite mixed soil layer 21 and the mud formation prevention film 22 is constructed on the ground G.

At this time, if a cationic emulsion is used as the asphalt emulsion As of the mud-preventing material 221, the asphalt content is rapidly separated without waiting for the evaporation of water after spraying, and the mud-preventing film 22 is formed in a short period of about half a day. Can be formed.

As described above, the construction method of the impermeable layer 2 using the mud-decomposing preventive material 221 does not require a special device and does not require complicated work, so that the workability is improved, the construction period is shortened, and the construction cost is reduced. However, it is possible to prevent the bentonite mixed soil layer 21 from becoming muddy and to provide a high-quality impermeable layer 2.

Further, the mud-forming preventive material 221 that forms the mud-forming prevention film 22 of the impermeable layer 2 is obtained by diluting the asphalt emulsion As with an emulsion diluting solution 4 in which a nonionic sedimentation inhibitor 5 is added to water and dissolved. Created by. Therefore, even when a cationic emulsion is used for the asphalt emulsion As, the phenomenon that the asphalt component is decomposed and solidified does not occur, and the asphalt emulsion As is uniformly dispersed in the mud-forming preventive material 221. It is possible to maintain such a state.

Therefore, when the mud-preventing material 221 is sprayed on the surface of the bentonite mixed soil layer 21, a high-quality mud-preventing film 22 having a substantially uniform layer thickness without unevenness can be formed. As a result, it is possible to exhibit high impermeable performance and prevent the bentonite mixed soil layer 21 from becoming mud while suppressing the amount of spraying per ^{1 m 2} of the construction target area to a small amount.

Further, since the sedimentation suppressing material 5 has a property of imparting viscosity to water, not only the sedimentation of the asphalt emulsion As can be suppressed, but also the viscosity of the mud-forming preventive material 221 can be imparted. Therefore, when the mud formation prevention material 221 is sprayed on the surface of the bentonite mixed soil layer 21, a mud formation prevention film 22 that is in close contact with the bentonite mixed soil layer 21 is formed, so that water leakage occurs from the gap between the two. It becomes possible to suppress it.

The method of constructing the mud-proofing material 221 and the impermeable layer 2 of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention.

For example, in the present embodiment, the impermeable layer 2 provided between the waste disposal site 1 and the ground G is given as an example, but the present invention is not necessarily limited to this, and the impermeable layer 2 provided on the ground G is not necessarily limited to this. If so, it may be adopted in any facility.

Further, as long as the mud-preventing material 221 can form the mud-preventing film 22 on the surface of the bentonite mixed soil layer 21, any means such as spraying, spraying, and coating may be adopted as the construction method.

1 Waste disposal site 2 Impermeable layer 21 Ventnite mixed soil layer 211 Ventnite mixed soil 211'Simulated bentnite mixed soil 22 Mudification prevention film 22'Comparative mudderization prevention film 221 Mudification prevention material 3 Waste 4 Emulsion diluted solution 5 Sedimentation inhibitor 6 Acrylic mold 7 Water tank G Soil W Water W'Tap water As Asphalt emulsion

Claims (4)

It is a mud-forming preventive material that prevents the bentonite layer laid by compacting and compacting the bentonite-mixed soil sprinkled on the ground.
The asphalt emulsion and the emulsion diluting solution for diluting the asphalt emulsion are provided.
A mud-degrading preventive material, wherein the emulsion diluted solution is obtained by adding and dissolving a sedimentation inhibitor that is nonionic and imparts viscosity to water to water. In the mud prevention material according to claim 1,
A mud-preventing material, characterized in that the sedimentation suppressing material is guar gum. In the mud prevention material according to claim 2,
A mud-forming preventive material, wherein the sedimentation inhibitor is added in an amount of 0.3% by weight or more and 2.0% by weight or less with respect to water. A method for constructing an impermeable layer using the mud-forming preventive material according to any one of claims 1 to 3.
The process of sprinkling bentonite mixed soil on the ground, compacting it, and laying a bentonite layer.
A method for constructing a water-impervious layer, comprising:

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