JPH04345685A - Conditioner for water-containing soil - Google Patents

Abstract

PURPOSE:To obtain the title conditioner which can condition surplus soil in construction, having high water content, to make it suitable for reuse as resources by using a carboxylated water-soluble polymer and lime as constituents. CONSTITUTION:The title conditioner contains a carboxylated water-soluble polymer [e.g. a (meth)acrylamide polymer containing (meth)acrylic acid or its salt] and lime (powdery quick lime or slaked lime) preferably at a weight ratio of (1:2) to (1:250). By using this conditioner, surplus soil of high water content, which has hitherto been difficult to utilize and an object for illegal dumping, can be conditioned in a plant as it is without being dried in the sun so that it can be reused as resources for back filling, etc.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improver for hydrated soil. Specifically, we improve the soil quality of construction surplus soil, etc. (hereinafter referred to as "surplus soil") generated from construction and civil engineering work, etc.
This invention relates to a water-containing soil improver suitable for reuse as a resource.

0002

[Prior art] Traditionally, most of the surplus soil generated in various places was
Since it cannot be reused, it is disposed of in landfills or transported to other locations, but there is a significant amount of illegal dumping, and it is attracting attention as an issue of environmental destruction. This is due to the fact that while the amount of surplus soil generated is rapidly increasing due to active redevelopment projects, the number of sea-surface reclamation projects is decreasing, making it difficult to secure sites to accept the surplus soil.

[0003] In addition, when backfilling the excavated site,
The law stipulates that sand must be used. Therefore, for backfilling, it is generally necessary to bring mountain sand from other areas, which is also causing problems of environmental destruction. Regarding the reuse of surplus soil generated under such circumstances,
There is an example in which a test plant for treating residual soil using quicklime is in operation.

0004

[Problem to be solved by the invention] The above test plant method targets only high-quality residual soil, and because the site is vast, it is improved by targeting residual soil that has been dried in the sun and has a low moisture content. When considering an improved plant, a large site is not available, so it is necessary to improve the residual soil with a high moisture content generated on site without drying it in the sun, and such soil with a high moisture content is highly sticky. This caused problems such as adhesion to mixers and other equipment, making operations difficult and impossible to dispose of.

[0005]

[Means for Solving the Problems] The present inventors have solved the problems of the prior art and, as a result of intensive studies to obtain an excellent improver for the reuse of residual soil, have developed a method containing (meth)acrylic acid or its salt. We have discovered that by using lime in combination with a water-soluble polymer having a carboxyl group such as a (meth)acrylamide-based polymer, water-containing soil such as leftover soil can be reused for backfilling, and we have arrived at the present invention.

That is, the gist of the present invention resides in a water-containing soil improving agent comprising a water-soluble polymer having a carboxyl group and lime. The present invention will be explained in detail below. In order to reuse soft or highly sticky water-containing soil for backfilling, etc., the improvement of the present invention aims to improve its strength, give it fluidity like sand, and improve it to the extent that it does not swell in water. It is a solidification process. Therefore, the improvement in the present invention does not simply mean clumping and solidifying the water-containing soil to a state in which fluidity is lost.

[0007] The water-soluble polymer used in the present invention is usually a polymer that dissolves in an amount of 1 g or more in at least 100 ml of water. The polymer has a carboxyl group as a hydrophilic group, and among all the monomers constituting the polymer,
The monomer having a carboxyl group is usually 1 to 80 mol%
, preferably 5 to 60 mol%. Furthermore, the carboxyl group may be present in either free acid or salt form.

Examples of the salt include salts of alkali metals such as sodium and potassium, salts of alkaline earth metals such as calcium and magnesium, ammonium salts, and amine salts such as alkylamines having 1 to 18 carbon atoms and alkanolamines. , and mixtures of two or more of these, preferably alkali metal salts. Such water-soluble polymers include (meth)acrylamide-based polymers containing (meth)acrylic acid or its salts, copolymers of maleic acid or its salts and vinyl acetate, itaconic acid or its salts and (meth) Although there are copolymers with acrylamide, preferred are (meth)acrylamide-based polymers containing (meth)acrylic acid or a salt thereof. Acrylamide polymers containing (meth)acrylic acid or its salts include (meth)acrylic acid or its salts and (meth)acrylic acid or its salts.
In addition to those copolymerized with meth)acrylamide, those obtained by partially hydrolyzing (meth)acrylamide may also be used. Alternatively, a copolymer of a combination of the monomers shown above may be used.

Furthermore, the above polymer may contain monomers containing sulfonic acid groups as hydrophilic groups, such as vinyl sulfonic acid,
A copolymer containing allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, salts thereof, etc. may also be used. In addition, hydrophobic monomers such as olefins, acrylic esters, and vinyl esters may be included as long as they do not impede water solubility.

The molecular weight of the water-soluble polymer used in the present invention is usually 1,000,000 or more, preferably 5,000,000 or more. Although the manufacturing method is not particularly limited, it is generally a radical polymerization method, and among these, solution polymerization using water, lower alcohol, or the like as a solvent is particularly employed. The concentration of the monomer is usually 10% by weight or more, preferably 15 to 60% by weight. When polymerizing in an aqueous solvent, the polymerization initiators include peroxides such as potassium persulfate and ammonium persulfate, redox initiators using them, and N,N'-azobis-(
Water-soluble radical polymerization initiators such as 2-amidinopropane) dihydrochloride and 4,4'-azobis-(4-cyanovaleric acid)-2-sodium are preferred. The amount of the radical polymerization initiator used is usually 0.005 to 5% by weight, preferably 0.05% by weight, based on the weight of the mixture of copolymerizable monomers.
~0.5% by weight.

The polymerization method is not particularly limited, but examples of aqueous solution polymerization include polymerization under stirring, polymerization while standing in a container under heat insulation, polymerization in sheet form while removing heat, and polymerization in oil. Examples include a method of polymerizing in an aqueous emulsion or in a dispersed state. The method of polymerization by leaving still is to remove oxygen by passing nitrogen gas through the specified monomer aqueous solution, then bring it to the specified temperature, add the radical polymerization initiator, mix uniformly, and then bring it to the specified temperature under a nitrogen gas stream. An example of a method of holding is given. The polymerization temperature is usually selected in the range of 10 to 150°C depending on the molecular weight of the desired polymer, but preferably 40 to 80°C.

[0012] The thus obtained polymer is dried as it is in a drier or treated with a dehydrating agent, then dried and pulverized, and then used as a sample. The lime used in the present invention is quicklime or slaked lime, and in either case it is preferably added in powder form. The mixing weight ratio of water-soluble polymer and lime is usually 1:
The ratio is 1 to 1:500, preferably 1:2 to 1:250.

[0013] The soil to which the present invention is applied usually has a water content of 20% or more. In particular, the improver of the present invention can be expected to have a water content of 40 to 200, and even a water content of 6.
It is soil with a high moisture content of about 0 to 150, and specifically, it is the leftover soil (construction surplus soil) generated from general civil engineering and construction work such as domestic water supply and sewerage work, road work, and residential land development work. . The water content ratio is a value expressed as a percentage of the mass of soil water lost by oven drying at 100°C to the oven dry mass of soil, and is defined in JIS A1203 (
This is the value measured by the water content ratio test method).

[0014] The soil type includes a loam layer, gravel, earth and sand, and is usually a mixture of these, but depending on the site, concrete pieces may also be mixed in. The water content ratio varies depending on the soil quality, so it largely depends on the site where it occurs. Examples of materials with a high water content include the Kanto loam layer, which usually has a water content of around 100 to 120 and is highly sticky; however, by using the improver of the present invention, it can be solidified and
Since it is granulated, it is given fluidity, has no stickiness or swelling property in water, improves ground bearing capacity, and can be reused for backfilling.

The amount of the improver of the present invention added is not particularly limited as it varies depending on the water content ratio of the soil to be treated, but the water-soluble polymer is usually 0.001 to 1% by weight, based on the water-containing soil.
Preferably it is 0.01 to 0.5% by weight, and the amount of lime is
It is usually 0.2 to 20% by weight, preferably 0.5 to 10% by weight. The method of adding the improver of the present invention is not particularly limited, but preferably it is a method of adding lime after adding the water-soluble polymer, but there is no problem in using it simultaneously by adding and mixing or premixing. Further, the mixing with soil may be carried out by a conventional method, such as a method in which the improver is sprinkled on the water-containing soil on a belt conveyor and mixed using a backhoe. Lime is usually added in the form of a powder, but the water-soluble polymer may be added in the form of a powder or an aqueous solution.

[0016] Other cement-based solidifying agents, super absorbent resins, etc. can be added to the improving agent of the present invention in arbitrary proportions, and these may also be added separately at the time of soil mixing.

[0017]

[Examples] The present invention will be explained in more detail by examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example of producing a water-soluble polymer In a 100 ml separable flask equipped with a stirrer, a nitrogen inlet tube, and a cooling tube, 9.60 g of a 20% by weight sodium acrylate (hereinafter abbreviated as "ACA-Na") aqueous solution and 13
．． 08 g of acrylamide (hereinafter abbreviated as "AAM") and 32.82 g of demineralized water were added and uniformly dissolved. The system was degassed while stirring and introducing nitrogen into the container.

Next, soak in a 50°C water bath until the internal temperature is 50°C.
When the temperature was reached, 4.50 g of 0.2% by weight N,N'-azobis-(2-amidinopropane) dihydrochloride aqueous solution was added to bring the total amount to 60 g. Incidentally, stirring was stopped at the start of polymerization. 4 in a constant temperature water bath at 50°C while introducing nitrogen.
When polymerized for a period of time, the concentration of the polymer was 25% by weight.
Polymer A having a molar ratio of CA-Na/AAM=10/90 was obtained.

Polymers B to H were obtained in the same manner except that the monomer compositions were changed to those described below. Approximately 10 g of each of the obtained 25% by weight polymers was left for measuring the polymerization rate, which was wet-pulverized and dehydrated in acetone or methanol, dried under reduced pressure at room temperature, and further pulverized using a coffee mill-type pulverizer to form fine powder. did.

The polymerization rate measured by the bromine method was approximately 100% in all cases. Also, for the reduced viscosity ηsp/c,
The dried polymer was dissolved in 1N saline to a concentration of 0.1 g/dl and measured at 25°C using an Ostwald viscometer. Below, the monomer composition (molar ratio) of Polymers A to H
, indicating reduced viscosity. (composition)

(Reduced viscosity) Polymer A: ACA-Na/A
AM=10/90 28.1
〃 B: 〃
=20/80 31.
2 〃C: 〃
=30/70 2
6.9 〃 D: 〃
=60/40
19.6 E: MCA-Na/AA
M = 20/80 26.9
〃 F: A A M
=100 29.6
〃 G:AMPS-Na/AAM=10
/90 28.9 〃
H: 〃 =
20/80 27.8 Polymers A to D
is ACA-Na/AAM system, and E is sodium methacrylate (hereinafter abbreviated as "MCA-Na")/AAM
system, F is an AAM homopolymer, G and H are sodium 2-acrylamido-2-methylpropanesulfonate (hereinafter abbreviated as "AMPS-Na")/AAM system. Examples 1 to 5 and Comparative Examples 1 to 5 Improvement tests were conducted using the Kanto loam layer (collection location: Minami Otani, Machida City, Tokyo) with a water content of 115 as raw material soil.

[0021] The raw material soil was divided into 7 kg portions into plastic bags and subjected to improvement treatment. In the improved treatment, 7 g of each type of water-soluble polymer powder was sprinkled and mixed in a plastic bag, and then 210 g of quicklime powder was added and stirred. It was immediately sealed to prevent moisture from escaping. After 6 days of sealed curing, the improved soil was divided into three layers in a mold with an inner diameter of 15 cm and tamped 92 times with a rammer weighing 4.5 kg in accordance with JIS A1210 (soil compaction test method by compaction). We conducted a test.

[0022] Next, preparations were made for a water immersion expansion test in accordance with JIS A1211 (CBR test method), and the amount of expansion was monitored by immersing it in a water tank for 4 days. Furthermore, after taking it out from the aquarium, removing the water, and performing the prescribed measurement 15 minutes later,
CBR (California Bearing Ra)
tio) A load-penetration curve was determined using a tester. The load at a penetration depth of 2.5 mm (hereinafter abbreviated as penetration strength) is read, and CBR is calculated using the following formula. As the standard load in the formula, the standard load of 1,370 kg at the time of 2.5 mm penetration as defined by JIS was used.

CBR=(penetration strength/standard load)×100(%)CBR
The larger the value, the higher the strength. In addition, the condition of the improved soil was visually observed. The test results are summarized in Table 1. In addition, the expansion ratios determined from the expansion amount after 4 days of water immersion, which were measured at the same time, were all 1% or less, which was good.

[0024]

[Table 1] *) Because the clay was soft, it could not be tamped by a tamping tester, so it was tamped by hand as a reference.

Examples 6, 7 and Comparative Examples 6-8 Polymer B
The test was conducted in the same manner as in Example 1 except that the amount of lime was changed.

The results are shown in Table 2. Comparative Examples 6 to 8 were all treated with lime alone. The results of the water immersion expansion test showed that the swelling ratio was 1% or less in all cases. Note that Example 2 is also listed in Table 2 for comparison.

[0027]

[Table 2]

[0028]

[Effect of the invention] By using the water-containing soil improver of the present invention, residual soil with a high moisture content, which was previously difficult to use and subject to illegal dumping, can now be improved in plants without being dried in the sun. , it can be reused as a resource for backfilling, etc. In this way, environmental damage caused by illegal dumping of surplus soil and extraction of sand for backfilling can be prevented, and this greatly contributes to the local community.

Claims (3)

[Claims] 1. A water-containing soil improvement agent comprising a water-soluble polymer having a carboxyl group and lime. 2. The water-containing soil improvement agent according to claim 1, wherein the water-soluble polymer is a (meth)acrylamide-based polymer containing (meth)acrylic acid or a salt thereof. Claim 3: The weight ratio of water-soluble polymer and lime is 1:1.
The water-containing soil improving agent according to claim 1, wherein the ratio is 1:500 to 1:500.