JP2007314725A - Ground stabilizing admixture, ground stabilizing material and construction method for ground stabilization using the ground stabilizing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ground stabilizing admixture, ground stabilizing material and a ground stabilizing construction method, enabled fixed amount force feed, capable of imparting high viscosity decreasing effect and equalizing impregnant, and for force injection into the soil to harden and stabilize the ground. <P>SOLUTION: A ground stabilizing admixture comprising a phosphate, an alkali metal chloride and a polyacrylic acid, the ground stabilizing admixture containing 20-250 pts. alkali metal chloride and 20-200 pts. polyacrylic acid per 100 pts. phosphate, the ground stabilizing admixture further containing an organic acid, the ground stabilizing admixture containing 10-55 pts. solid in 100 pts. ground stabilizing admixture, the ground stabilizing material comprising cement, the ground stabilizing admixture and water, the ground stabilizing material comprising cement, a phosphate, an alkali metal chloride and a polyacrylic acid, are provided. A ground stabilizing construction method comprising force injection of the ground stabilizing material into the ground, mixing with the soil and curing, is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a ground stabilization admixture, a ground stabilization material, and a ground stabilization method for injecting high pressure into the ground and hardening and stabilizing the ground.

In order to improve a bad ground such as a soft ground, the soft ground must be hardened and stabilized.
As this ground stabilization method, for example, a method in which cement milk is sprayed deeply into the ground at high pressure, mixed with soil, hardened and stabilized (see Non-Patent Document 1) can be mentioned.
In this method, for example, a pipe for injecting cement milk into the ground is inserted, and the cement milk is injected at a high pressure from the vicinity of the pipe tip while rotating the pipe to cut the soil in the ground. While discharging the mixture with soil to the ground through another tube, the pipe is raised at a constant speed, and the ground is replaced with a mixture of cement milk and soil to harden and stabilize the ground. .
When cement milk and soil are mixed by cutting, the cement particles and soil particles agglomerate with each other due to electrical action, so the viscosity of the mixed soil, which is a mixture of cement milk and soil, increases. There was a problem that it was difficult to discharge it to the ground.

As a material for reducing the viscosity of the mixed soil, as a liquid material, an ultrahigh pressure jet injection method containing a naphthalene sulfonate formalin condensate, a melamine sulfonate formalin condensate, and / or a polycarboxylic acid compound, etc. Cement additives are known (see Patent Document 1).
However, these cement additives for ultra-high pressure jet injection method have some results in sandy soil and sandy silt, but in viscous ground, the effect of lowering viscosity is small, There is a problem that it is difficult to improve strength development.

On the other hand, substances that contain phosphates, alkali metal-containing materials (sulfates, sulfites, carbonates, bicarbonates, etc.), organic acids, ammonium salts, etc. A combination is known (see Patent Documents 2 to 7).
However, these have a problem that the effect of lowering the viscosity is small although the strength development is excellent in the viscous ground.

  Moreover, when using the liquid ground stabilization admixture, the provision of the higher viscosity reduction effect and the homogenization with an injection are calculated | required.

Tsuboi, Naomichi, Actual state of chemical injection method, pages 5-9, March 25, 1981, Kashima Press, second revised edition issued Japanese Patent Laid-Open No. 06-127993 JP 05-254903 A Japanese Patent Laid-Open No. 06-206747 Japanese Patent Application Laid-Open No. 07-206495 Japanese Patent Application Laid-Open No. 07-069695 JP 2004-143041 A JP 09-194835 A

  As a result of various studies to solve the above problems in the ground stabilization method, the present inventor has given a high viscosity reduction effect by using a specific ground stabilization admixture, and by liquefaction, It became possible to perform quantitative pumping, and in addition, the present invention was completed upon obtaining the knowledge that excellent strength development was exhibited.

  That is, the present invention is a ground stabilization admixture or a liquid ground stabilization admixture comprising phosphate, alkali metal chloride, and polyacrylic acid. On the other hand, the ground stabilization admixture comprises 20 to 250 parts of alkali metal chloride and 20 to 200 parts of polyacrylic acid, and further comprises the admixture for stabilization of ground comprising organic acids. Yes, the ground stabilization admixture having a solid concentration of 10 to 55 parts in 100 parts of the liquid ground stabilization admixture, comprising cement and the ground stabilization admixture A ground stabilization material, a ground stabilization material containing cement, phosphate, alkali metal chloride, and polyacrylic acid. The ground stabilization material is injected into the ground at high pressure and mixed with soil. It is a ground stabilization method that is hardened.

  By using the ground stabilization admixture of the present invention and the ground stabilization material using the same, a high viscosity reduction effect is imparted, and quantitative pumping is possible by liquefaction, and excellent strength development The effect is shown.

Hereinafter, the present invention will be described in detail.
Parts and% used in the present invention are based on mass unless otherwise specified.

  In the ground stabilization admixture of the present invention (hereinafter referred to as the present admixture), phosphates, alkali metal chlorides, and polyacrylic acids are used.

  The phosphate used in the present invention has an effect of reducing the viscosity of the mixed soil, and preferably has high solubility in water. Specifically, in addition to phosphoric acid, pyrophosphoric acid, metaphosphoric acid, and hexametaphosphoric acid, These salts such as dihydrogen phosphate and dihydrogen pyrophosphate can be used. As the salt, sodium salt, potassium salt, lithium salt and the like can be used, and one or two of these can be used. The above can be used. Of these, use of phosphoric acid or dihydrogen phosphate is preferable.

  In the present invention, an alkali metal chloride (hereinafter referred to as the present chloride) is further used as a substance that reduces the retarding action of phosphate without increasing the viscosity reduction effect and increases the strength development.

Examples of the chloride include chlorides such as sodium, potassium, and lithium, and one or more of these can be used. Of these, sodium chloride is preferred in terms of strength development.
The amount of the chloride used is preferably 20 to 250 parts, more preferably 30 to 200 parts, relative to 100 parts of phosphate. If it is less than 20 parts, high strength development may not be obtained, and if it exceeds 250 parts, a sufficient viscosity reducing effect may not be obtained.

In this invention, the effect of reducing the further outstanding viscosity is acquired by using polyacrylic acid together.
The polyacrylic acid is polyacrylic acid or a derivative thereof or a salt thereof. Specifically, polyacrylic acid or a polyacrylic acid ester copolymer or a sodium salt, a potassium salt, or a calcium salt thereof may be used. Although it can be used, it is preferable to use a sodium salt from the viewpoint of availability, and the copolymer is preferably a crosslinked branched type. In particular, in the present invention, sodium polyacrylate, particularly a low-polymerization water-soluble polymer, having a solid content of 90% or more and a 40% concentration slurry viscosity at 25 ° C. of 10,000 cps or less. The use of a polymerization degree type is preferable from the viewpoint of obtaining a high viscosity reduction effect, and a viscosity of 50 to 2,000 cps is more preferable.
The amount of polyacrylic acid used is preferably 20 to 200 parts, more preferably 30 to 150 parts, per 100 parts of phosphate. If it is less than 20 parts, a sufficient viscosity reducing effect may not be obtained, and if it exceeds 200 parts, it takes a long time to solidify, and high strength development may not be obtained.

  When the present admixture is used as a liquid, the total solid content of phosphate, main chloride and polyacrylic acid in 100 parts of the admixture is preferably 10 to 55 parts, 15 to 45 More preferably, it is a part. If it is less than 10 parts, a large amount of the admixture needs to be added, and the construction efficiency may decrease. If it exceeds 55 parts, the stability of the admixture may be impaired.

In the present invention, it is preferable to use organic acids in order to further improve the viscosity reducing effect and the stability of the present admixture.
The organic acids are those that stabilize metal ions in the admixture and are not particularly limited as long as they are substances that can be used for this purpose. For example, at least one carboxyl group, preferably 1 is used. It is an organic acid having ˜3, more preferably 2-3, and it is possible to use one having 1 to 3 hydroxyl groups and / or 1 to 3 amino groups.
Specific examples of these organic acids include, for example, (1) monocarboxylic acids such as formic acid, acetic acid, and propionic acid, (2) oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, malein Dicarboxylic acids such as acid, fumaric acid and phthalic acid, (3) tricarboxylic acids such as trimellitic acid and tricarbaryl, (4) oxycarboxylic acids such as citric acid, tartaric acid, gluconic acid and malic acid, malic acid (5) aminocarboxylic acids such as aspartic acid and glutamic acid, (6) aminopolycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA) and trans-1,2-diaminocyclohexanetetraacetic acid (CyDTA), (7 ) Ethylenediaminetetra (methylenephosphonic acid) [EDTPO], ethylenediaminedi (methylenephosphonic acid) [EDDPO], nitriloto (8) Complex forming agents such as phosphonic acids such as 1-hydroxyethylidene-1,1'-diphosphonic acid [HEDPO], and (8) diketones such as acetylacetone and hexafluoroacetylacetone. In the present invention, one or more of these complex-forming agents can be used. Moreover, what contains an alkali metal can also be used for a complex formation agent. Of these, it is preferable to use sodium citrate, which is effective in reducing viscosity and is less likely to inhibit strength development.
Although the usage-amount of organic acids is not specifically limited, 0.1-100 parts are preferable with respect to 100 parts of phosphates, and 0.3-60 parts are more preferable. If it is less than 0.1 part, the effect of reducing the viscosity may be reduced, and if it exceeds 100 parts, strength development may be inhibited.

Furthermore, in the present invention, it is possible to use an alkali metal sulfate as a substance that reduces the retarding action of phosphate without increasing the viscosity reducing effect and increases strength development.
As the alkali metal sulfate, sodium sulfate, potassium sulfate, and lithium sulfate can be used, and one or more of these can be used. Of these, sodium sulfate is preferably used in terms of strength development.
The amount of alkali metal sulfate used is preferably 20 to 250 parts, more preferably 30 to 150 parts, per 100 parts of phosphate. If it is less than 20 parts, high strength development may not be obtained, and if it exceeds 250 parts, a sufficient viscosity reducing effect may not be obtained.

  This admixture uses phosphates, chlorides, and polyacrylic acids and, if necessary, organic acids and alkali metal sulfates as materials, and these materials are used in the form of powder. Either a powder or a solution can be used, but when a powder is used, it is preferably mixed with water and heated to form a solution as necessary.

The solution is preferably dissolved by heating, and it is possible to shorten the time for solution by heating.
The dissolution temperature is preferably 40 to 80 ° C., and the dissolution time is the time for these materials to be completely dissolved, preferably 10 minutes to 3 hours. The temperature raising rate and the cooling rate are not particularly limited, and it is possible to dissolve using a material or warm water preheated to 40 to 80 ° C. in advance.
It is preferable to stir at the time of dissolution, and it is possible to shorten the dissolution time by stirring.

  There are no particular limitations on the order of mixing the materials into the dissolution tank and the charging speed. Further, in order to adjust the storage property in the dissolution tank and the time required for the production, it is possible to adjust the pH using phosphoric acid, alkali metal hydroxide, carbonate or the like.

  In this invention, this admixture, cement, and water are mixed and a ground stabilization material is prepared.

  The cement used in the present invention is not particularly limited, and various portland cements such as normal, early strength, ultra-early strength, and moderate heat, and various portland cements mixed with blast furnace slag, fly ash, and the like. Examples include mixed cement, environmentally friendly cement (eco-cement) manufactured from municipal waste incineration ash and sewage sludge incineration ash, and commercially available fine particle cements. Various Portland cements and various mixed cements are finely powdered. It is also possible to use it. Moreover, what was adjusted by increasing / decreasing the quantity of components (for example, gypsum etc.) normally used for cement can also be used.

  The amount of the admixture used is preferably 1 to 50 parts, more preferably 3 to 30 parts, relative to 100 parts of cement. If it is less than 1 part, the effect of lowering viscosity may be small, and if it exceeds 50 parts, strength development may be inhibited.

  The amount of water used in the present invention varies depending on the moisture content of the soil and is not particularly limited, but is usually preferably 30 to 500 parts, more preferably 50 to 300 parts with respect to 100 parts of cement. . If it is less than 30 parts, the fluidity of the mixed soil (slime), which is a mixture of cement milk and soil, is small, and if it exceeds 500 parts, strength development may be inhibited.

In the present invention, it is possible to use a water reducing agent, particularly a high performance water reducing agent, due to soil conditions and construction reasons.
The water reducing agent is used to improve the fluidity of cement concrete and can be used in liquid or powder form.
As the water reducing agent, for example, known water reducing agents such as lignin sulfonic acid, naphthalene sulfonic acid, and polycarboxylic acid can be used.

  This admixture is effective not only for clay soil but also for soil such as sandy soil and corrosive soil.

  The mixing and stirring conditions of the present invention are not particularly limited as long as the admixture and water are mixed before high-pressure jetting into the ground, and when the admixture is a liquid, It is possible to mix and stir with water using a batch mixing method that mixes water with a grout mixer that rotates at a rotational speed of about 10 to 1,000 rpm, or a continuous mixing method that uses a line mixer with blades installed in the pipe. is there.

  Next, the ground stabilization method of the present invention will be described.

First, drill a hole that requires ground improvement.
The diameter of the drilling hole is not particularly limited as long as the injection rod can be inserted.
The depth of the drilling hole varies depending on the region to be improved and is not particularly limited, but is usually about 10 to 50 m.
Next, a double tube or triple tube structure injection rod is inserted, and cement milk obtained by adding water to the ground stabilization material of the present invention is pumped using a grout pump, an ultrahigh pressure pump, a compressor, or the like. Inject from a nozzle of a heavy pipe or a triple pipe.
A larger pumping pressure of cement milk is preferable, but it is usually about 50 to 700 kg / cm ² in consideration of wear of the double pipe, triple pipe, or nozzles thereof.
The amount of cement milk fed is not particularly limited, but is preferably about 30 to 800 liters / minute.

  The cement milk jetted in this way in the ground is mixed and stirred together with the soil, and the injection rod rises to the ground at a constant speed while rotating, so it finally consists of cement milk and soil. A columnar pile is formed in the ground.

  The diameter of this pile varies depending on soil conditions such as N value indicating the hardness of the ground and construction conditions such as injection pressure, but is not particularly limited, but 0.5 to 20 m is appropriate. Pile can be 3 to 50m long.

  Hereinafter, the present invention will be described in detail based on experimental examples.

Experimental example 1
The phosphate, the present chloride, and the polyacrylic acids shown in Table 1 were mixed and stirred at 50 ° C. for 30 minutes to prepare a liquid main admixture.
Next, 5 parts of the prepared admixture was mixed with 100 parts of cement, and 140 parts of water was further mixed to prepare cement milk.
This cement milk was mixed with clay having a water / powder mass ratio of 120% at a volume ratio of 1: 1 to obtain a slime, and its viscosity and compressive strength were measured. The results are also shown in Table 1.
In addition, the powdery present admixture was prepared and experimented in the same manner.

<Materials used>
Cement: Ordinary Portland cement, commercially available, density 3.15 g / cm ³
Phosphate a: sodium dihydrogen phosphate, commercial phosphate b: phosphoric acid, commercial product chloride a: sodium chloride, commercial product chloride a: potassium chloride, commercial polyacrylic acid: polyacrylic acid Sodium, commercial product, viscosity 1,000 cps
Clay: Bentonite powder, commercial product, density 2.30g / cm ³

<Measurement method>
Viscosity: Measure the obtained slime with a B-type viscometer under the conditions of temperature 20 ° C, humidity 80%, rotation speed 20rpm. Compressive strength: Pour the obtained slime into a 4cm x 4cm x 16cm mold and remove after curing. The specimen obtained by molding was sealed at a temperature of 20 ° C, and the compressive strength at age 7 days was measured.

  From Table 1, it is understood that a high viscosity reduction effect and a high strength value can be obtained by using 20 to 250 parts of the present chloride and 20 to 200 parts of polyacrylic acid with respect to 100 parts of the phosphate. In addition, the solution obtained by making this admixture (Experiment No. 1-5) has a higher viscosity reducing effect than the one used in powder form (Experiment No. 1-15).

Experimental example 2
It carried out similarly to Experimental example 1 except having mixed the phosphate shown in Table 2, this chloride, and polyacrylic acid, and preparing this admixture of solid content concentration shown in Table 2. The results are also shown in Table 2.

Experimental example 3
The same procedure as in Experimental Example 1 was conducted except that the phosphate, the present chloride, the polyacrylic acids, and the organic acids shown in Table 3 were mixed and stirred at 50 ° C. for 30 minutes to prepare a liquid present admixture. . The results are also shown in Table 3.

<Materials used>
Organic acids A: Sodium citrate, commercial products Organic acids B: Succinic acid, commercial products

  From Table 3, it can be seen that by using 0.1 to 100 parts of organic acid with respect to 100 parts of phosphate, a further excellent viscosity reduction effect can be obtained.

Experimental Example 4
100 parts of phosphate a, 100 parts of the present chloride and 100 parts of polyacrylic acid were mixed and stirred at 50 ° C. for 30 minutes to prepare a liquid admixture having a solid content of 30%.
The amount of the admixture shown in Table 4 was mixed with water to 100 parts of cement to form a solution of 140 parts, and this was mixed with cement to prepare cement milk.
This cement milk was mixed with a clay having a water / powder mass ratio of 120% in a ratio of 1: 1 by volume with the cement milk to obtain a slime. The viscosity and compressive strength of this slime were measured. The results are shown in Table 4.

  From Table 4, it is understood that an excellent viscosity reducing effect can be obtained by using 1 to 50 parts of this admixture with respect to 100 parts of cement.

  By liquefaction, quantitative pumping becomes possible, and in addition, since it exhibits excellent strength development, it is suitable for the ground stabilization method.

Claims (8)

  An admixture for ground stabilization, comprising phosphate, alkali metal chloride, and polyacrylic acids.   A liquid ground stabilization admixture comprising a phosphate, an alkali metal chloride, and polyacrylic acids.   The ground stabilization admixture according to claim 1 or 2, wherein the alkali metal chloride is 20 to 250 parts and the polyacrylic acid is 20 to 200 parts with respect to 100 parts of the phosphate.   Furthermore, the admixture for ground stabilization as described in any one of Claims 1-3 containing organic acids.   The solid stabilization admixture according to any one of claims 2 to 4, wherein a solid content concentration is 10 to 55 parts in 100 parts of the liquid ground stabilization admixture.   A ground stabilization material comprising cement and the ground stabilization admixture according to any one of claims 1 to 5.   A ground stabilization material comprising cement, phosphate, alkali metal chloride, and polyacrylic acids.   A ground stabilization method in which the ground stabilization material according to claim 6 or 7 is injected into the ground at a high pressure, and mixed with soil to harden.