JP2024019747A - Soil modifier - Google Patents

Abstract

To provide a soil modifier that uses an alternative substance instead of an anionic polymeric coagulant as a modification auxiliary combined with a water-absorbing polymer, to reduce environmental load, while providing modification effects that are not inferior to conventional products.SOLUTION: A soil modifier contains a water-absorbing polymer, a modification auxiliary, a solidifying agent, and a dispersant. The soil modifier uses thickening polysaccharides instead of anionic polymeric coagulants, thereby reducing environmental impact while offering modification effects that are not inferior to conventional products.SELECTED DRAWING: Figure 1

Description

The present invention mainly relates to a soil conditioner for treating soft soil containing a large amount of water.

For soil that contains a lot of water, such as sedimentary soil caused by tsunami or storm surge damage, construction sludge, and soft soil, waste materials such as plants, stones, and waste materials contained in the soil are removed using a sieve and reused. In order to smoothly carry out transportation and removal using heavy equipment, etc., we conduct reformation work to make the soil into fine grains that are easy to handle, and solidify and strengthen soft soil to make it easier to transport and remove it from residential areas and parks. For example, soil may be modified to make it usable for other purposes, or if soft soil contains harmful substances, it may be insolubilized to prevent the harmful substances from leaching out of the soil.

On the other hand, soil reforming agents containing flocculants, reforming aids, solidifying agents, and dispersing agents are used as treatment agents to transform turbid water, high water content sludge, etc. into free-flowing soil that is easy to handle. A soil reforming agent described in Patent Document 1 is conventionally known, which uses a water-absorbing polymer as a flocculant and an anionic polymer flocculant as a modification aid.

In addition, by using a soil improvement solidifying agent that is a mixture of a cement-related solidifying agent, a pH adjuster, a flocculant, and a water absorption enhancer for highly water-containing soil, soft soil can be used for other purposes. A solidifying agent for soil improvement described in Patent Document 2 that strengthens and improves soil to provide suitable soil and ground is conventionally known.

Furthermore, we have a patent for treating contaminated soil containing harmful substances generated in mountainous areas and urban areas by using a treatment agent containing magnesium oxide as a main component to insolubilize the harmful substances and prevent them from leaching out of the contaminated soil. The insolubilization method described in Document 3 is conventionally known.

JP 2021-6614 Publication Japanese Patent Application Publication No. 2002-363560 JP 2021-011574 Publication

According to the above Patent Documents 1 to 3, it is possible to reform high water content soil into soil that is easy to handle, strengthen soft ground, and prevent harmful metals from flowing out from within the soil. However, since the soil conditioner contains a large amount of petroleum-derived components, there was a problem in that the environmental impact on the soil being treated was high.

The present invention provides a soil reforming agent that has a lower environmental impact than when an anionic polymer flocculant is used as a reforming agent combined with a water-absorbing polymer, and can exhibit various reforming performances that are equivalent or better. The purpose is to

As a result of intensive studies to solve the above problems, the present inventors have developed a soil conditioner containing a water-absorbing polymer, a reforming aid, a solidification agent, and a dispersant in place of an anionic polymer flocculant. It was discovered that by adding a thickening polysaccharide, the same modification performance could be achieved with a lower environmental impact, and the present invention was completed. The invention is as follows.

[1] A soil improving agent containing a water-absorbing polymer and a modification aid, characterized in that the modification aid is a thickening polysaccharide.
[2] A soil amendment characterized by using tapioca flour as the thickening polysaccharide.
[3] It is characterized by containing 0.6 to 3% of the thickening polysaccharide.
[4] It is characterized by containing 0.1% or more of the water-absorbing polymer.
[5] A soil conditioner characterized in that magnesium oxide is used as the solidifying agent.
[6] A soil amendment characterized by adding a pH adjuster.
[7] A soil amendment characterized by using calcium carbonate or zeolite as a dispersant.

According to the present invention configured as described above, by using a thickening polysaccharide instead of an anionic polymer flocculant as a modification aid combined with a water-absorbing polymer, the effect of modifying water-containing soil can be improved. It is possible to keep the environmental impact to a lower level while still achieving its full potential.

It is a table showing the results of an experiment comparing the modification performance of a comparison modifier and soil modifiers 1 and 2. It is a table comparing the experimental results when the comparative modifier and soil modifier 1 were used in sample soils with moisture contents of 42%, 45%, 48%, and 52%. FIG. 2 is a table showing the relationship between the amount of soil conditioner added and the amount of arsenic eluted.

Embodiments of the present invention will be described below. Note that the percentages described in this specification are based on mass unless otherwise specified.

The soil amendment according to the embodiment of the present invention contains a water-absorbing polymer, a thickening polysaccharide which is also used as a reforming aid, a solidifying agent, a pH adjusting agent, and a dispersing agent, and is portable as a whole. It is easily powdered.

The above soil conditioner can effectively absorb moisture in the soil by combining a water-absorbing polymer that absorbs and swells moisture with a reforming agent that has a flocculating effect. It can reform soil that contains a lot of water into smooth particles. Furthermore, by including a thickening polysaccharide as a modification aid instead of an anionic polymer flocculant made of petroleum-derived ingredients, the soil quality is the same or better than when an anionic polymer flocculant is used. It is possible to significantly reduce the burden on the environment while obtaining the reforming effect. Hereinafter, the specific structure of the soil conditioner of the present invention will be explained.

(Water-absorbing polymer)
A water-absorbing polymer (water-absorbing polymer, SAP) is a polymeric resin that absorbs water and swells when it comes into contact with water. Examples of water-absorbing polymers include starch-based, cellulose-based, polyvinyl alcohol-based, and acrylic-based resins.

In addition, the water-absorbing polymer exhibits a modifying effect if it is contained in an amount of 0.1% or more of the total soil modifier, and increasing the content of the water-absorbing polymer increases the modifying effect. Specifically, the water-absorbing polymer preferably accounts for about 1 to 6% of the total soil conditioner.

(thickening polysaccharide)
As a modification aid to be combined with the water-absorbing polymer, a naturally occurring thickening polysaccharide was used in place of the conventional anionic polymer flocculant. Specific examples of thickening polysaccharides include guar gum, locust bean gum, tara gum, xanthan gum, alginic acid, carrageenan, tamarind gum, glucomannan, cationized starch, cationized guar gum, quince seed, agar, methylcellulose, carboxymethylcellulose, In addition to a mixture of multiple polysaccharides such as tapioca starch and soybean polysaccharide, and their salts or derivatives, it also contains by-products including thickening polysaccharides generated in the manufacturing process such as flying powder. Further, as a modification aid, only one type of the above-mentioned thickening polysaccharides may be used, or two or more types may be used as a mixture. In the present invention, in particular, tapioca processed into powder was used.

Further, the content of the thickening polysaccharide is preferably about 0.6 to 3.0%, particularly preferably about 0.8 to 1.6%, based on the total soil conditioner.

(solidifying agent)
A solidifying agent is a solidifying and insolubilizing agent containing either or both of a magnesium component and a calcium component as a main component, and is used to solidify the soil that is the object of treatment and to insolubilize harmful substances contained in the soil. Can be done. Specifically, magnesium oxide, calcium oxide, etc. are used.

In addition, the content of the solidification agent is determined by the soil quality (type) and moisture content of the hydrated soil, the purpose of the modified treated soil (specifically, whether it will be transported, sieved to remove impurities, or used for soft soil. (e.g., whether to increase the strength of soil, insolubilize harmful metals in soil, etc.) That is, while it is possible to obtain the effect of improving soil without including a solidifying agent, the amount to be added is adjusted depending on the intended use of the treated soil that has undergone the reforming treatment and has become granular. Depending on the use, it may be included so as to constitute 50% or more of the total soil conditioner.

(pH adjuster)
The pH adjuster may be one that can adjust the pH of the soil conditioner, which is made alkaline by the solidifying agent, and specifically includes citric acid, malic acid, adipic acid, fumaric acid, maleic acid, succinic acid, Organic acids such as tartaric acid and their derivatives, sulfates such as ammonium sulfate, ferrous sulfate, aluminum sulfate, lithium sulfate, magnesium sulfate, potassium sulfate, ammonium phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, phosphorus Phosphates such as sodium acid dihydrogen phosphate and potassium dihydrogen phosphate, chloride salts such as ammonium chloride, carbonates and carbon hydrogen salts such as sodium carbonate, potassium carbonate, dolomite, sodium hydrogen carbonate, potassium hydrogen carbonate, hydroxide It may be a hydroxide such as magnesium, a metal oxide such as amyluna, or an acid clay such as acid clay or activated clay.

In addition, if you want to make the pH of the soil conditioner acidic, increase the content of the pH adjuster in the solidification agent, and if you want to make the pH of the soil conditioner alkaline, increase the content of the pH adjuster in the solidification agent. By reducing (not adding) the amount, the pH of the soil amendment can be adjusted as desired. In other words, soil conditioners are usually neutral, but if the soil to which they are added is acidic or alkaline, adjusting the pH of the soil conditioner in advance will bring the pH of the soil after the modification to neutral. , or be able to approach neutrality.

(dispersant)
Dispersants are mainly inorganic powders that can make it easier for water-absorbing polymers and modification aids to spread throughout the soil to be treated, improving the efficiency of removing water from the soil and improving soil modification. It also has the effect of reducing the amount of chemicals used. Examples used in the present invention include, but are not limited to, powdered materials such as calcium carbonate, zeolite, gypsum, coal ash, diatomaceous earth, volcanic ash, and paper sludge. Among these, powders of calcium carbonate and zeolite, which make the modified soil less likely to form lumps, are more preferred. In addition, as a dispersing agent, one type may be used individually, and two or more types may be used in combination.

The powdered soil conditioner according to the present embodiment described above can be produced by mixing a water-absorbing polymer, a thickening polysaccharide, a solidifying agent, a pH adjusting agent, and a dispersing agent in a mixer or the like. . By the way, in order to achieve the effect of modifying water-containing soil into smooth granules, it is possible to achieve a certain degree of effect if at least a water-absorbing polymer and a thickening polysaccharide are included. Solidifying agents must also be included in order to strengthen and improve soil, and to insolubilize harmful substances contained in soil.

(Soil modification method)
The soil improvement method using the soil amendment of the present invention includes a step of adding the above-mentioned soil amendment to the water-containing soil to be treated, and stirring so that the soil amendment is uniformly contained in the soil. The method includes a stirring process in which water-containing soil is modified into a loose (granular) state.

The present invention will be specifically explained below using experimental examples. Note that the present invention is not limited to these examples. First, an experimental example regarding a soil amendment using tapioca flour processed as a reforming aid (thickening polysaccharide) will be described.

(Experiment example)
First, sample soil was prepared by mixing yellow soil and clay at a ratio of 4:1 and adding water until the moisture content reached 42%. A modification treatment was performed by adding and stirring the prepared soil samples, and the modification effects of the soil samples (water-containing soil) were compared for each modifier. At this time, the amount of soil amendment added to the sample soil was adjusted so that the amount of the improvement aid was 0.04g, 0.08g, and 0.16g per 100g of sample soil, and the comparison was made. .

By adding and mixing an anionic polymer, processed tapioca flour, or processed potato flour to the above sample soil, it was confirmed whether soil modification effects could be obtained.

FIG. 1 is a table comparing soil modification effects when anionic polymers, processed tapioca flour, or processed potato flour are added to sample soil. As shown in the experimental results in FIG. 1, both tapioca flour and potato flour were confirmed to have a certain degree of soil reforming effect. Among them, it was confirmed that when tapioca flour was used, the modification effect was higher than when potato flour was used, and the modification effect was equivalent to that when an anionic polymer flocculant was used.

Additionally, when an anionic polymer flocculant was added to the sample soil, some viscosity occurred in the sample soil, whereas when tapioca flour was added, there was almost no viscosity in the sample soil. Ta. That is, by using tapioca flour as a modification aid instead of an anionic polymer flocculant, it is possible to modify the treated soil after modifying the water-containing soil so that it has no viscosity and is more fluffy. Therefore, handling of the treated soil is improved, and it becomes easier to transport the treated soil and remove foreign matter using a sieve or the like more smoothly.

(Experiment example 2)
First, a comparative modifier consisting of 6% water-absorbing polymer (sodium polyacrylate), 0.8% anionic polymer flocculant, and 83.2% dispersant (calcium carbonate), and a water-absorbing polymer ( A soil conditioner of the present invention was prepared, which consisted of 6% of sodium polyacrylate), 1.6% of a thickening polysaccharide (processed tapioca flour), and 82.4% of a dispersant (calcium carbonate).

The moisture content of the above sample soil was increased stepwise to 42%, 45%, 48%, and 52%, and the hydrated soil was modified using the above soil amendment and a comparative amendment at each moisture content. Performance was compared. At this time, the amount and concentration of the soil amendment agent was determined based on the experimental results of Experiment 1, so that the amount of the soil amendment agent added was 0.024g or 0.048g per 100g of sample soil. They were adjusted and compared. By the way, sample soil with a moisture content of 48% has water just beginning to float on the surface of the soil, and sample soil with a moisture content of 52% is in a muddy state.

FIG. 2 is a table comparing the experimental results when the comparative modifier and the soil modifier were used in sample soils with moisture contents of 42%, 45%, 48%, and 52%. As shown in the experimental results in Figure 2, the soil amendment of the present application had the same improvement performance as the comparative amendment when the moisture content of the sample soil was 42%, 45%, and 48%. It was confirmed that it works. In addition, no water regurgitation phenomenon was observed in any of the treated soils within 24 hours after treatment.

(Experiment example 3)
First, 4.4% of water-absorbing polymer (sodium polyacrylate), 0.6% of thickening polysaccharide (processed tapioca flour), 13.3% of solidifying agent (magnesium oxide), and pH adjuster (sulfuric acid) A soil conditioner of the present invention was prepared, which consisted of 5.4% (1 iron) and 76.3% dispersant (calcium carbonate).

Next, the sample soil contained a small amount of arsenic as a harmful substance, and a soil conditioner was added to the sample soil to determine the amount of arsenic leached from the sample soil.

FIG. 3 is a table showing the relationship between the amount of soil conditioner added and the amount of arsenic eluted. As shown in the figure, it was confirmed that by treating soil containing harmful substances using the soil conditioner of the present application, it was possible to insolubilize the harmful substances in the soil.

In addition, as a result of measuring the soil strength of the treated soil modified with soil modifiers, the cone index immediately after modification was approximately 500 kN/m2, regardless of which modifier was used, and after 7 days, the soil strength was measured. After curing to some extent, it became 1300kN/square meter. In other words, it was confirmed that the soil conditioner containing the solidifying agent can also be used to strengthen and improve soft ground and soft soil.

Claims (7)

In a soil amendment containing a water-absorbing polymer and a reforming aid,
A soil improvement agent, characterized in that the improvement aid is a thickening polysaccharide. The soil amendment according to claim 1, characterized in that tapioca flour is used as the thickening polysaccharide. The soil amendment according to claim 1, containing 0.6 to 3% of the thickening polysaccharide. The soil conditioner according to claim 1, comprising 0.1% or more of the water-absorbing polymer. The soil amendment according to claim 1, which contains magnesium oxide as a solidifying agent. The soil amendment according to claim 1, further comprising a pH adjuster. The soil amendment according to claim 1, wherein calcium carbonate or zeolite is used as a dispersant.