JPS581716B2 - Soil stabilization method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for stabilizing soil quality.

Consolidating and hardening soft ground and preventing water permeation are important issues in the fields of civil engineering, architecture, agriculture, and mining, and grouting methods such as cement milk, silicate, and chromium lignin have traditionally been used. A known method is to inject a chemical solution (soil stabilizer) containing such substances into the soil and gel it in the soil.In particular, recently there have been various synthetic polymer soil stabilizers such as acrylamide, urea, and urethane. It has been developed and put into practical use.

Among these synthetic polymeric soil stabilizers, acrylamide monomer (or a monomer mixture of water-soluble vinyl monomer and acrylamide monomer that can be copolymerized with acrylamide monomer), water-soluble divinyl monomer, The so-called acrylamide soil stabilizer, which consists of an aqueous solution of a mixture of polymers and redox catalysts, has good permeability into the soil, easy adjustment of gel time, and high gel strength and durability. It is superior to other soil stabilizers in terms of good water permeability and workability during construction, and is known as a typical polymeric soil stabilizer.

However, with conventional acrylamide-based soil stabilizers, a relatively large amount of vinyl monomers (mainly acrylamide monomers) remain in the gel (polymer) even after gelation is completed in the soil. There are drawbacks.

Acrylamide polymers are almost harmless, but acrylamide monomers are orally toxic in mice and have an LD5o of 2.
It is highly toxic at 52 mg/kg.

Recently, due to the spread of pollution prevention ideas based on the preservation of the living environment and the improvement of public health, the toxicity of monomers remaining in polymeric soil stabilizers polymerized in the soil has become a major social problem. There is a need for the development of a polymeric soil stabilizer that has a small amount of residual monomer after polymerization, in other words, a polymeric soil stabilizer that has a very high polymerization rate.

The amount of monomer remaining in the polymeric soil stabilizer after polymerization depends on the types of vinyl monomer and divinyl monomer used, but it varies greatly depending on the selection of the polymerization catalyst.

Acrylamide-based soil stabilizers can be gelled using only water-soluble radical catalysts such as persulfates and water-soluble peroxides, but they can also be gelled at low temperatures below room temperature, for example in the case of construction in cold regions. Because it is necessary to quickly gel the stabilizer, in acrylamide-based soil stabilizers, a water-soluble reducing substance (to accelerate polymerization) is usually added to the above radical catalyst as a catalyst. A variety of so-called redox catalysts are used.

Various compounds have been proposed as reducing agent components of redox catalysts used in acrylamide soil stabilizers, but amines such as tertiary amines and polyalkylene polyamines have excellent activity, and it is important to use them. It is an excellent reducing agent that has the advantage of making it easy to adjust the gel time of the chemical solution, especially when used in combination with a reducing metal salt. It has the advantage of being able to

However, even when an acrylamide soil stabilizer is gelled in soil using a redox catalyst containing such a reducing agent component, even if the amount is small in the polymer after 24 hours have passed after gelation. 100ppm
In some cases, more than 1000 ppm of acrylamide monomer remains, and if a large amount of amine is used in an attempt to shorten the gel time, or if an amine and a reducing metal salt are used together, the remaining amount of acrylamide monomer becomes even more. The amount of pollutants increases dramatically, which contaminates the soil and causes unfavorable results in terms of pollution prevention.

In view of this, the present inventors conducted various studies in an attempt to rectify the above-mentioned shortcomings seen in the prior art, and as a result, when stabilizing soil quality with an acrylamide-based soil stabilizer, amines were used as a reducing agent component of a redox-based catalyst. By using sulfite (or bisulfite) in combination, the polymerization rate of the soil stabilizer injected into the soil is significantly increased, and this reduces the amount of acrylamide monomer remaining in the soil stabilizer after gelation. The present invention was developed based on the discovery that the

That is, the present invention provides (a) an acrylamide monomer or a mixture of a water-soluble vinyl monomer copolymerizable with the acrylamide monomer and an acrylamide monomer, (a) a water-soluble divinyl monomer, and (c) a water-soluble divinyl monomer. When a chemical solution containing a redox catalyst is injected into soil and gelled in the soil to stabilize the soil quality, amines and sulfite (hydrogen) salts are used in combination as reducing agent components of the redox catalyst. The main purpose of this study is to stabilize soil quality.

The water-soluble vinyl monomer used in combination with the acrylamide monomer in the present invention can be copolymerized with acrylamide, and typical examples include acrylamide derivatives such as methacrylamide, methylolacrylamide, and acrylamide. Examples include acids and their monovalent salts, methacrylic acid and their monovalent salts, vinyl acetate, hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and its salts, dimethyldiallylammonium chloride, and the like.

The mixing ratio of these water-soluble vinyl monomers to acrylamide monomers can be changed as appropriate depending on the construction purpose (strength of the stabilized soil, degree of water stoppage, etc.), but usually Acrylamide monomer: water-soluble vinyl monomer -1: 0.5 or less (molar ratio).

The water-soluble divinyl monomer used in the present invention is copolymerized with an acrylamide monomer (or a monomer mixture of this and other water-soluble vinyl monomers) to form a polymer with a three-dimensional network structure. Examples include alkylidene bisacrylamides such as methylenebisacrylamide, condensates of polyhydric aldehyde compounds and acrylamide such as dihydroxyethylenebisacrylamide, and 3-di(acrylamidomethyl)-2-imitazolidone. Examples include condensates of cyclic polymethylene urea, formaltehyde and acrylamide, condensates of acrylamide such as hexahydro-1,3,5-triacroyl-s-triazine, and polyvalent metal salts of acrylic acid or methacrylic acid.

Acrylamide monomer (of these water-soluble divinyl monomers)
or a monomer mixture of this and other water-soluble vinyl monomers), the mixing ratio is usually preferably 1 to 30% by weight.

The oxidizing agent components of the redox catalyst used in the present invention include commonly used persulfates, hydrogen peroxide, water-soluble organic peroxides, perchloric acid, etc., but especially potassium persulfate and ammonium persulfate. Representative persulfates are preferably used.

In the present invention, amines and sulfite (hydrogen) salts are used in combination as the reducing agent component of the retox catalyst, and the amines used include, for example, dimethylaminopropionitrile, dimethylaminoethanol, dimethylaminepropanol, and triethanolamine. , nitrilotrispionamides, tertiary amines such as triethylamine, trimethylamine, N-N-N'-N'-tetramethylethylenediamine, secondary amines such as diethanolamine, morpholine, piperazine, triethylenetetramine, tetraethylene Examples include polyethylene polyamines such as pentamine, polyethyleneimine, dimethylaminomethylated polyacrylamide, and polymeric amines such as polydimethylaminoethyl methacrylate, but especially dimethylamine propionitrile, triethanolamine, dimethylamino It is preferable to use ethanol, triethylamine, diethanolamine, etc. because the amount of acrylamide monomer remaining in the soil stabilizer after polymerization can be reduced.

These amines may be used not only individually, but also in combination.

The types of sulfites used in the present invention include, for example, sodium sulfite, lithium sulfite, and sodium sulfite. Potassium sulfate, ammonium sulfite, etc. are mentioned, and types of hydrogen sulfite include not only water-soluble salts such as sodium hydrogen sulfite, potassium hydrogen sulfite, and ammonium hydrogen sulfite, but also others such as calcium sulfite,
Examples include salts that are sparingly soluble in water, such as barium sulfite, lead sulfite, iron sulfite, and copper sulfite.

Even when these poorly water-soluble salts are used, the same effects as when soluble salts are used can be expected.

Sulfites and hydrogen sulfites can be used not only individually, but also in combination.

In the present invention, in addition to the above-mentioned sulfite (hydrogen) salt, a known reducing agent such as Rongalit,
Reducing metal ions and the like can also be used.

In addition, an appropriate polymerization inhibitor such as ferrocyan salt or ferrocyan salt may be added to the chemical solution to temporarily suppress gelation of the chemical solution injected into the soil.

In the present invention, the amount of the redox catalyst used is usually 1 to 30% by weight based on the total monomer components in the case of the oxidizing agent component, while the amount of the redox catalyst used is usually 1 to 30% by weight based on the total monomer component in the case of the reducing agent component. 0.5 to 40% by weight of amines, sulfite (
Hydrogen) salt is used in an amount of 0.1 to 20% by weight.

The present invention is preferably implemented as follows.

4 to 40% by weight aqueous solution of a mixture of acrylamide monomer (or a monomer mixture of this and other water-soluble vinyl monomers) and a water-soluble divinyl monomer, based on the total monomer component. A chemical solution is prepared by adding 0.5 to 40% of amines and 0.1 to 20% of sulfite (hydrogen) salt, and further adding an appropriate known polymerization accelerator or polymerization inhibitor as necessary.
This is called liquid A.

Next, 1 to 30% by weight based on the total monomer components in liquid A.
An aqueous solution containing the oxidizing agent component of the redox catalyst is prepared in the same volume as the A solution, and this is designated as the B solution.

Both solutions A and B are mixed in equal volumes and injected into soil to polymerize and gel in the soil.

In addition, the present inventors previously reported in Japanese Patent Application No. 52-45854 that when preparing an acrylamide-based soil stabilizer, the supernatant liquid obtained by dissolving soil with microbial activity in water was used as the mixing water to achieve polymerization. It was proposed that the amount of acrylamide remaining in the soil stabilizer can be extremely reduced, but if the above-mentioned supernatant liquid is used as the mixing water when preparing the soil stabilizer used in the present invention. The amount of acrylamide monomer remaining in the soil stabilizer after polymerization can be further reduced.

Furthermore, if an appropriate amount of suspended matter such as cement milk, which has been conventionally used in various soil stabilizers, is added to the soil stabilizer used in the present invention, an even better soil stabilizing effect can be obtained.

EXAMPLES Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples.

In addition, in each example, all parts simply represent weight.

Example 1 130 parts of acrylamide, 22 parts of sodium methacrylate
A mixture of 6 parts, 2.0 parts of 3-di(acrylamidomethyl)-2-imidazolidone, 16 parts of dimethylamine propionitrile, and 1.0 part of sodium bisulfite was dissolved in water to make a total amount of 200 parts. .

This is called liquid A. On the other hand, 2.0 parts of potassium persulfate was dissolved in water to make the total amount 200 parts.

This is called liquid B. Keep the temperature of both liquids A and B at 20℃,
The mixture was poured into 1500 parts of standard sand while being mixed in equal amounts to form a gel.

It gelated after 1 minute and 42 seconds. After gelation, the changes over time in the amount of acrylamide monomer remaining in the hardened sand and the physical properties of the hardened sand were measured, and the results are shown in Table 1.

To extract the residual acrylamide monomer from the hardened sand, add approximately 5 times the amount of pure water to the sampled hardened sand, mix and crush this with a juice mixer for 10 minutes, and pass through it once to remove the sand and swollen gel. The amount of acrylamide monomer in the r-liquid thus obtained is determined from the Pharmaceutical Toxicology Chemistry Test Method [edited by the Pharmaceutical Society of Japan, Sanitary Chemistry 2].
The measurement was carried out by the gas chromatography method specified in Vol. 0, No. 3, p. 150 (1974).

Comparative Example 1 An acrylamide soil stabilizer was prepared in the same manner as in Example 1 except that sodium bisulfite was not used, and the mixture was poured into standard sand.

Both solutions A and B gelled in 3 minutes and 4 seconds.

Table 2 shows the results of measuring changes over time in the amount of acrylamide monomer remaining in the hardened sand after gelation and the unconfined compressive strength of the hardened sand.

As is clear from the comparison of the results of Comparative Example 1 and Example 1, dimethylaminopropionitrile and sodium hydrogen sulfate were used as the reducing agent components of the redox catalyst when solidifying the standard sand with the acrylamide soil stabilizer. When used in combination (Example 1, the amount of acrylamide monomer remaining in the hardened sand 24 hours after gelation was reduced by about 1 liter compared to the case where sodium hydrogen sulfate was not used (Comparative Example 1))
/10.

Comparative Example 2 Ferrous sulfate (heptahydrate) instead of sodium bisulfite
An acrylamide soil stabilizer was prepared in the same manner as in Example 1 except that 0.4 part of citric acid (l hydrate) and 0.2 part of citric acid (l hydrate) were used and poured into the standard sand.

Both solutions A and B gelled in 1 minute and 17 seconds.

Table 3 shows the results of measuring changes over time in the amount of acrylamide monomer remaining in the hardened sand after gelation and the unconfined compressive strength of the hardened sand.

As is clear from the comparison of the results of Comparative Example 2 and Example 1, dimethylamine propionitrile and sodium hydrogen sulfate were used as the reducing agent components of the redox catalyst when solidifying the standard sand with the acrylamide soil stabilizer. When used in combination (Example 1 is a case where other water-soluble reducing agents (ferrous sulfate and citric acid) are used instead of sodium hydrogen sulfate (Comparative Example 1), the hardening after 24 hours after gelation is Reduce the amount of acrylamide monomer remaining in the sand to approximately 1/10
can be reduced to

Examples 2-6 13.0 parts of acrylamide, 2 parts of sodium methacrylate
．． 0 parts, 2.0 parts of 3-(diacrylamide methyl)-2-imidazolide, 2.4 parts of triethanolamine, and a mixture of reducing agents as shown in Table 4 were dissolved in water to make a total amount of 200 parts. I made it.

This is called liquid A.

On the other hand, dissolve 2.0 parts of potassium persulfate in water and make 2.0 parts of potassium persulfate.
It was made into 00 copies.

This is called liquid B. Keep the temperature of both liquids A and B at 20℃,
The mixture was poured into 1500 parts of standard sand while being mixed in equal volumes to form a gel.

Table 4 shows the results of measuring the change over time in the amount of acrylamide monomer remaining in the hardened sand after gelation and the unconfined compressive strength of the hardened sand.

As is clear from Table 4, when triethanolamine and bisulfite (or sulfite) were used together as the reducing agent component of the redox catalyst according to the method of the present invention, the The amount of remaining acrylamide monomer was small as in Example 1, and good results were obtained.

Comparative Examples 3 to 4 Acrylamide-based soil stabilization was carried out in the same manner as in Example 2, except that in Example 2, sodium hydrogen sulfite was not used as the reducing agent component, and only triethanolamine was used in the amount shown in Table 5. The standard sand was consolidated with the agent.

Table 5 shows the results of the same tests as in Example 2 for compacted sand.

Claims (1)

[Claims] 1 (a) an acrylamide monomer or a mixture of an acrylamide monomer and a water-soluble vinyl monomer that can be copolymerized with an acrylamide monomer, (a) a water-soluble divinyl monomer, and (c) a redox catalyst. In order to stabilize the soil quality by injecting the chemical containing the chemical solution into the soil and gelling it in the soil, amines and sulfites (
A soil stabilization method characterized by the combined use of hydrogen (hydrogen) salt.