JP2012012483A - Grout material for grouting and grouting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grout material for grouting which ensures easy adjustment of gelling time, excels in infiltration property into the ground, and exhibits high durability and solidification strength, even when it has a composition not using phosphoric acid at all or using a reduced amount of the phosphoric acid, and to provide a grouting method using the grout material.SOLUTION: The grout material for grouting is mainly composed of colloidal silica and sodium silicate, contains an inorganic acid and an organic acid as a gelling agent, and has a pH at 25°C of 2-7. It is preferable that the grout material for grouting contains a pH buffer solution prepared by combining an inorganic acid with an organic acid having the logarithmic value (pKa) of the reciprocal of an acid dissociation constant at 25°C in the range of 1.0-7.0, and has buffering action in the pH range of 2-7.

Description

  TECHNICAL FIELD The present invention relates to a ground injection grout material containing silica particles of colloidal silica and a ground injection method, and more particularly to improvement of ground used for soft ground and ground liquefaction prevention, foundation ground reinforcement work, etc. The present invention relates to a ground injection grout material and a ground injection construction method.

As a ground injection material for injecting into soft ground or the like to solidify the ground, conventionally, an injection material mainly composed of sodium silicate, an injection material mainly composed of an acidic active silicate aqueous solution consisting of sodium silicate and acid, or An injection material mainly composed of neutral colloidal silica is known (Patent Documents 1 and 2). However, these injection materials all contain a large amount of alkalis or salts. When the content of alkali or salt is large, the alkali or salt is liberated from the consolidated body over a long period of time, causing shrinkage destruction of the consolidated body, resulting in durability deterioration such as a decrease in strength of the consolidated body. In order to improve such drawbacks, in recent years, sodium silicate is treated with a cation exchange resin or an ion exchange membrane to remove the alkali in the sodium silicate soda solution and further use colloidal silica. A ground injection material has been proposed (see, for example, Patent Documents 3 to 5).
The ground injection material described in Patent Document 3 is composed of acidic colloidal silica and sodium silicate, and is excellent in that a high-strength injection material can be obtained. However, there is a large variation in gelation time due to slight differences in material composition. Comes with difficulties.
The ground injection material described in Patent Document 4 is an injection material obtained by adding an acidic agent such as an inorganic acid or tartaric acid to the active silicic acid to improve the stability of the active silicic acid, but the gelation time is only extended for several days. It cannot be said that handling at the construction site is easy. Furthermore, a method for improving the storage stability by adding an alkali agent to extend the gelation time has been described, but in this method, the gelation time varies greatly due to slight differences in the material composition, making it difficult for practical use. Is accompanied.
The ground injection material described in Patent Document 5 is an injection material composed of active silicic acid, sodium silicate, and an acidic reactant (organic acids such as inorganic acid, citric acid, and gluconic acid, and examples are phosphoric acid only), and an active silicic acid aqueous solution. Since the silica concentration is several percent by weight, the transportation cost from the production site (factory) to the construction site is high, and the gelation takes place in a few days, so problems such as being unable to store in large quantities at the construction site are solved. Not.

  As mentioned above, the ground injection material using activated silicic acid is limited to a part of use, so that the ground injection material containing two components of colloidal silica and sodium silicate as a main material and containing a gelling agent is widely used. became. Of the two components, the gelation time is adjusted mainly by the blending ratio of sodium silicate and gelling agent, and phosphoric acid, sulfuric acid, and sodium hydrogen sulfate are used as the gelling agent. Among them, phosphoric acid has three steps of pKa values (logarithm of the reciprocal of acid dissociation constant, pKa1 = 1.83, pKa2 = 6.43, pKa3 = 1.46) and is an acid that can easily adjust the gelation time. . However, in lakes and rivers, there are concerns about enrichment due to phosphorus accumulation. On the other hand, sulfuric acid and sodium hydrogen sulfate are acids whose pKa2 is 1.74 and it is difficult to adjust the gelation time.

  Incidentally, the above colloidal silica is a commercial product generally called a silica sol, and a silica concentration of 20 to 50% by weight obtained by stabilizing and concentrating active silicic acid usually obtained by passing sodium silicate through an ion exchange resin by heating or the like. The average particle size is about 10 to 20 nm. These ground injection materials mainly composed of colloidal silica are highly permeable injection materials and are excellent in durability.

JP 54-73407 A Japanese Patent Laid-Open No. 3-66794 Japanese Patent Laid-Open No. 4-136088 Japanese Patent Laid-Open No. 11-181425 JP 2000-109835 A

  Therefore, the present invention can easily adjust the gelation time, has excellent permeability to the ground, and has high durability and consolidation strength even if the composition does not use phosphoric acid at all or reduces the amount used. An object is to provide a grout material for injection and a ground injection method using the same.

As a result of diligent research to solve such problems, the inventors of the present invention have used a colloidal silica and sodium silicate as main materials, and a ground injection grout material containing a specific acid as a gelling agent has a gelation time. It was found that the adjustment was easy, the permeability to the ground was excellent, and the durability and consolidation strength were high.
That is, the present invention is a ground injection grout material containing colloidal silica and sodium silicate as main materials, an inorganic acid and an organic acid as gelling agents, and a pH of 2 to 7 at 25 ° C.
More preferably, it contains a pH buffer solution in which an inorganic acid and a logarithmic value (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. are combined in the range of 1.0 to 7.0, and buffered between pH 2 and 7 It is a grout material for ground injection having an action.
The inorganic acid is preferably sulfuric acid, phosphoric acid or a mixed acid of sulfuric acid and phosphoric acid.
The organic acid is preferably selected from the group consisting of oxalic acid, maleic acid, tartaric acid, malic acid, citric acid and lactic acid.
In the most preferred combination, the inorganic acid is sulfuric acid and the organic acid is oxalic acid or citric acid.
Furthermore, the present invention also provides a ground injection method for injecting the above-mentioned ground injection grout material into the ground.

  ADVANTAGE OF THE INVENTION According to this invention, adjustment of gelation time is easy, the grout material for ground injection | pouring which is excellent in the permeability to the ground, and has high durability and consolidation strength can be provided. By injecting the ground injection grout material of the present invention into the ground, the stability of the ground can be remarkably improved.

It is a figure which shows the relationship of the sulfuric acid concentration in the grout material for ground injection | pouring, and pH. It is a figure which shows the relationship between the sulfuric acid concentration in the grout material for ground injection | pouring, and gelation time. It is a figure which shows the relationship of the sulfuric acid concentration in the grout material for ground injection | pouring, and pH. It is a figure which shows the relationship between the sulfuric acid concentration in the grout material for ground injection | pouring, and gelation time. It is a figure which shows the relationship between the acid concentration (except the phosphoric acid content of a base) in the grout material for ground injection, and pH. It is a figure which shows the relationship between the acid density | concentration (except the base phosphoric acid content) in the grout material for ground injection, and gelation time.

Hereinafter, the present invention will be described in detail based on preferred embodiments thereof.
The colloidal silica which is the main material of the ground injection grout material of the present invention is not particularly limited, and commercially available products can be used. Moreover, the sodium silicate which is a 2nd main material is not specifically limited, either, A commercially available product can be used.

The ground injection grout material of the present invention contains an inorganic acid and an organic acid as a gelling agent. As the inorganic acid, sulfuric acid, phosphoric acid or a mixed acid of sulfuric acid and phosphoric acid is preferable, but acidic salts thereof can also be used. A strong acid that completely dissociates like hydrochloric acid or nitric acid is not preferred because it is difficult to adjust the gelation time. In addition, when using the mixed acid of a sulfuric acid and phosphoric acid as an inorganic acid, it is preferable that the phosphoric acid density | concentration in the grout material for ground injection shall be 0.4 mol / L or less.
The organic acid is preferably an organic acid having a logarithmic value (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. of 1.0 to 7.0, and examples of such an organic acid include amino acids such as aspartic acid, alanine, and glycine. And carboxylic acids such as formic acid, citric acid, acetic acid, oxalic acid, tartaric acid, lactic acid, phthalic acid, propionic acid, maleic acid, butyric acid and malic acid. Among them, oxalic acid (pKa1 = 1.04, pKa2 = 3.82), maleic acid (pKa1 = 1.84, pKa2 = 5.83), tartaric acid (pKa1 = 2.87, pKa2 = 3.97), apple Acid (pKa1 = 3.23, pKa2 = 4.77), citric acid (pKa1 = 2.90, pKa2 = 4.35, pKa3 = 5.69), and lactic acid (pKa1 = 3.64) are more preferable. Since oxalic acid has a low molecular weight, it is most preferable because of its large acid amount per weight. The ground injection grout material of the present invention is mainly composed of colloidal silica and sodium silicate, contains the above-mentioned inorganic acid and organic acid as a gelling agent, and has a pH of 2 to 7 at 25 ° C. is there.

  More preferably, the ground injection grout material of the present invention comprises a pH buffer solution in which an inorganic acid is combined with an organic acid having a logarithmic value (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. of 1.0 to 7.0. And preferably has a buffering action between pH 2 and 7. According to the knowledge of the present inventors, the gelation time largely depends on the pH of the injection material. By using a pH buffer solution as the liquid composition of the ground injection grout material, the pH fluctuation due to slight differences in the material composition is small. The variation in pH is small even with respect to the decrease in the concentration of the injection material due to the groundwater, so that the variation in the gelation time is small, and the predetermined gelation time can be substantially realized easily.

  The colloidal silica which is the main material of the ground injection grout material of the present invention is not particularly limited, and commercially available products can be used. Moreover, the sodium silicate which is a 2nd main material is not specifically limited, either, a commercially available product can be used, and a 3 silicate sodium or a 4 silicate sodium is preferable, and 3 silicate sodium is produced in large quantities. It is inexpensive and preferable.

  The colloidal silica used in the present invention is manufactured using sodium silicate as a raw material. Sodium silicate is diluted in advance to a silica concentration of 3 to 7% by weight and brought into contact with a strongly acidic cation exchange resin to remove sodium to obtain an active silicic acid aqueous solution. The active silicic acid aqueous solution has a pH of about 2 to 4, and an alkali agent is added to the active silicic acid aqueous solution to adjust the pH to 9 to 10.5 and heated to 60 to 100 ° C. to perform particle growth (aging), or 60 to An active silicic acid aqueous solution is added to an alkali agent heated to 100 ° C. to adjust the pH to 9 to 10.5, and particle growth (aging) is performed while maintaining a temperature of 60 to 100 ° C. After the particle diameter is 5 to 20 nm, the silica concentration is adjusted to 10% by weight or more by ultrafiltration. In the present invention, a particle size of 5 to 20 nm is preferable.

  The colloidal silica preferably contains at least 10% by weight of silica particles. Furthermore, the silica concentration is preferably in the range of 10 to 30% by weight. Products with high silica concentration are preferred to simplify transportation and reduce transportation costs.

  The ground injection grout material of the present invention can be used in combination with another additive, for example, a gelling time adjusting agent. For example, slaked lime, calcium chloride, magnesium chloride, magnesium hydroxide, or the like is used to shorten the gelation time. Alternatively, the gelation time and initial gel strength can be adjusted by using cement (Portland cement, alumina cement, blast furnace cement) and slag in combination.

  The grout material for ground injection of the present invention is prepared by separately preparing a liquid A in which colloidal silica, an inorganic acid, an organic acid, and water are mixed and dissolved, and a liquid B in which sodium silicate is diluted with water. Are used in combination.

  As one of the ground injection methods, the ground injection grout material of the present invention is injected into an unstable ground (improved ground) through a chemical injection pipe, and the ground is strengthened by consolidation. It is a method of stopping the water and stabilizing the ground. In addition, as the ground improvement method, two or more kinds of ground injection grout materials of the present invention, for example, multiphase injection using ground injection grout materials having different sol particle diameters and reactants, and solidified. This is a method of strengthening or stopping the ground to stabilize the ground.

  In addition, the adjustment of the gelation time of the grout material for ground injection of the present invention may be arbitrary, and preferably in the range of several seconds to several tens of hours for that purpose. The gel time is preferably set according to the presence or absence of groundwater, the type of soil, the sediment accumulation structure, and the state around the injection site, and there is no particular limitation. Further, a one-shot method, a 1.5-shot method, a two-shot method, or the like may be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

(Materials used)
Colloidal silica; silica doll 30, manufactured by Nippon Chemical Industry Co., Ltd., silica concentration = 30% by weight
Sodium silicate; special sodium silicate, manufactured by Nippon Chemical Industry Co., Ltd., silica concentration = 26 wt%, Na ₂ O = 7 wt%, specific gravity 1.32
Phosphoric acid: 75% phosphoric acid, manufactured by Nippon Chemical Industry Co., Ltd. Sulfuric acid: 75% sulfuric acid, manufactured by Nippon Chemical Industry Co., Ltd. Oxalic acid dihydrate, citric acid monohydrate, maleic acid, DL-malic acid, lactic acid, tartaric acid: reagent

<Example 1>
The composition of the liquid B is shown in Table 1, the composition of the liquid A is 0.1 mol / L, the composition of the sulfuric acid is changed, and the composition of the liquid A is shown in Table 2. In mixing the two liquids, the B liquid was quickly added to the A liquid with stirring. The pH of the liquid mixture (injection material) and the gelation time were measured, and the results are shown in Table 3, FIG. 1 and FIG. A glass electrode type pH meter was used for pH measurement.

<Example 2>
The same material as Example 1 was used for B liquid, A liquid was made into the material mixing | blending which made the oxalic acid density | concentration 0.05 mol / L and the compounding quantity of the sulfuric acid was changed, and the material mixing | blending of A liquid was described in Table 4 . The pH and gelation time of the mixed solution (injected material) were measured, and the results are shown in Table 5, FIG. 1 and FIG.

<Comparative Example 1>
The same material as Example 1 was used for B liquid, oxalic acid was not used for A liquid, and it was set as the material mixing | blending which changed the compounding quantity only of a sulfuric acid, and the material mixing | blending of A liquid was described in Table 6. The pH of the liquid mixture (injection material) and the gelation time were measured, and the results are shown in Table 7, FIG. 1 and FIG.
As clearly shown in FIG. 1, with sulfuric acid alone (no oxalic acid added), the pH change with respect to the amount of sulfuric acid is steep in the pH range of 3 to 4, and the pH control is very difficult, and the gelation time can also be controlled. It can be estimated that it is difficult. As the oxalic acid concentration increases, the slope of the curve changes gently. When the oxalic acid concentration is 0.05 mol / L or more, the change is almost linear in the pH range of 3 to 4, and the pH control is relatively low. It can be estimated that the gelation time can be easily controlled.

<Example 3>
Examples of injection materials using various organic acids, phosphoric acid and sulfuric acid will be shown. The same material as Example 1 is used for B liquid, A liquid is made into the material mixing | blending which made the compounding quantity of organic acid and phosphoric acid constant, and changed the compounding quantity of sulfuric acid. 3. The pH and gelation time of the mixed solution (injected material) were measured, and the results are shown in Tables 9-1 to 3 and FIGS. 3 and 4.

<Comparative example 2>
An example of an injection material using only phosphoric acid and sulfuric acid without using an organic acid is shown. The same material as Example 1 is used for B liquid, A liquid is made into the material mixing | blending which made the compounding quantity of phosphoric acid constant, and changed the compounding quantity of sulfuric acid, and the material mixing | blending of A liquid is described in Table 10-1-2 did. The pH and gelation time of the mixed solution (injected material) were measured, and the results are shown in Tables 11-1 and 11 and FIGS. In the region of pH 3 to 4 in the figure, the pH is linearly changed with respect to the sulfuric acid concentration (sulfuric acid addition amount) in the sample added with the organic acid. In addition, the magnitude of the change is strongly suppressed as compared with the case where no organic acid is used.

<Example 4>
The example of the injection material which uses organic acid and phosphoric acid is shown. Table 12 shows the formulation table for the B liquid. Liquid A was based on the formulation shown in Table 13, mixed with various organic acids in different amounts, and finally added water to 300 ml. The pH of the liquid mixture (injection material) and the gelation time were measured, and the material composition of the liquid A was shown in Tables 14-1 to 14-7. In addition to the organic acid, the addition of phosphoric acid to the liquid A was also carried out. The pH and gelation time of the AB mixed solution (injection material) were measured, and the results are shown in FIGS. In the region of pH 3 to 4 in the figure, the sample to which the organic acid is added has a gentler pH change than the addition of phosphoric acid and a linear change. Among them, oxalic acid (pKa1 = 1.04, pKa2 = 3.82) has a small gradient because the pKa is small.

Claims (6)

  A grout material for ground injection, characterized by comprising colloidal silica and sodium silicate as main materials, an inorganic acid and an organic acid as gelling agents, and a pH of 2 to 7 at 25 ° C.   It contains a pH buffer solution in which an organic acid and an inorganic acid having a logarithm (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. of 1.0 to 7.0 are combined, and has a buffering action between pH 2 and 7. The grout material for ground injection according to claim 1, wherein:   The grout material for ground injection according to claim 1 or 2, wherein the inorganic acid is sulfuric acid, phosphoric acid, or a mixed acid of sulfuric acid and phosphoric acid.   The grout material for ground injection according to any one of claims 1 to 3, wherein the organic acid is selected from the group consisting of oxalic acid, maleic acid, tartaric acid, malic acid, citric acid and lactic acid.   The grout material for ground injection according to claim 1 or 2, wherein the inorganic acid is sulfuric acid and the organic acid is oxalic acid or citric acid.   A ground pouring method characterized by pouring the ground pouring grout material according to any one of claims 1 to 5 into the ground.

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