JP2000109834A - Chemical liquid to be injected in soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong gel time and obtain practical compressing strength and improved durability by using an aqueous solution of active silicic acid and an aqueous solution of acidic silica sol as effective components. SOLUTION: An aqueous solution of active silicic acid which substantially does not contain any salt is obtained by removing alkali ions from a water-soluble silicate such as sodium silicate and the like by means of an ion exchange method or the like. Acidic silica sol is obtained by mixing the water-soluble silicate with an acid such as sulfuric acid or the like and adjusting pH in an acidic region. An amount of the aqueous solution of acidic silica sol mixed with the aqueous solution of active silicic acid to prepare a chemical liquid to be injected in soil is preferably 2-200 wt.% of total amount of SiO2 existing in the aqueous solution of active silicic acid. Further, pH of the chemical liquid is preferably less than 4. Besides the two components, an inorganic salt such as aluminum sulfate or the like may be added to the chemical liquid as an auxiliary agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a ground injection chemical liquid particularly useful as a soil improvement material for strengthening the ground under existing structures, stopping water and / or preventing liquefaction, and more particularly to colloidal silica or acidic In contrast to silica sol, the present invention relates to a ground injection chemical solution in which the gelation time of a homogel is long and practical compressive strength is obtained.

[0002]

2. Description of the Related Art As a conventional soil injection material, a material mainly containing water glass is often used, and its hardening agent (gelling agent) includes calcium salts such as portland cement, slaked lime, steel slag, and sodium hydrogen sulfate. , Inorganic salts such as magnesium sulfate, various acids such as phosphoric acid, glyoxal,
Organic acids and esters such as ethylene carbonate have been used. However, the method using water glass has a problem in durability and the like, as already introduced in a large number of documents, and is recognized only as a temporary material. Therefore, various methods have been proposed for injecting a chemical solution adjusted to neutral or acidic by making an acidic reactant act on the water glass while avoiding the alkali content of the water glass. However, when the injection material is adjusted to near neutrality, it hardens instantaneously, so that the method of application as the injection material is limited. In addition, the one adjusted to acidic is Na ₂ produced by the reaction between water glass and a curing agent.
Water-soluble salts such as SO ₄ will be eluted even after the chemical solution has solidified, which causes environmental problems such as corrosion of underground structures and changes in water quality.

[0003] In view of the above, several ground injection materials mainly containing colloidal silica have been proposed. For example, a ground injection material containing a neutral silica sol as a main component and a polyvalent metal inorganic salt as a curing agent (Japanese Patent Application Laid-Open No. 54-73407), a gel obtained by mixing a colloidal solution of silicic acid and an alkali metal neutral salt There has been proposed a ground consolidation method (Japanese Patent Publication No. 22115/1990) in which an injection material whose aging time is adjusted within 20 hours is injected into the ground. In addition, as a method of adding an acid to colloidal silica, a silicate colloid solution having a pH of 4 to 7 and a gelation time adjusted within 20 hours is used, and a ground injection method (JP-A-59-93786). Gazette), a liquid for ground injection obtained by mixing a colloidal solution of silicic acid, an acid and a neutral salt of an alkali metal (Japanese Patent Publication No. 64-8677), and an acid obtained by mixing a colloidal solution of silicic acid and an acidic reactant. A ground injection chemical solution comprising colloidal silica and water glass (Japanese Patent Publication No. 7-10977) has been proposed.

The colloidal silica referred to here is a commercial product generally referred to as a silica sol, and is generally obtained by stabilizing activated silicic acid obtained by passing sodium silicate through an ion exchange resin by heating or the like, and having an average particle size of Is 10-20
nm is commonly used.

On the other hand, apart from acidic silica sol and colloidal silica, some ground improvement materials mainly using an aqueous solution of active silicic acid have been proposed. For example, Japanese Patent Publication No. 3-20430 and Japanese Patent Publication No. 1-55679 propose a ground improvement material mainly containing an active silicic acid aqueous solution (pH 2 to 4) substantially containing no salt.

[0006] These conventionally proposed chemicals have a long gel time of about 20 hours, so that the amount of the chemical which can be injected from one injection port is several cubic meters.
Since the ground improvement area is limited to a radius of about 1 m from the injection hole, when improving the ground under the existing structure having a width of several meters, many holes are required on the floor of the existing structure. The ground is improved by complicated means such as emptying and pouring a chemical solution there.

[0007]

When a chemical injection method is used as a measure to prevent liquefaction of an existing structure, it is necessary to greatly increase the penetration distance of the chemical into the ground in order to further simplify the operation. There is a need for a ground injection chemical solution having an extremely long gelation time and excellent durability.

[0008] The injection material containing water glass or acidic silica sol as a main component has problems in its own durability and the durability of a structure in contact with the injection material, and the injection material containing colloidal silica as a main component contains activated silica. The gel strength is weaker than that of the injection material used as the base material, and the longer the gelation time, the lower the gel strength tends to be.In order to obtain practical consolidation strength, a high concentration of silica must be used. In addition to the necessity, colloidal silica is obtained by stabilizing active silicic acid by complicated means as described above, and is disadvantageous because the production process becomes complicated industrially. In addition, the injection materials proposed so far have a maximum gel time of 20 hours even if the gel time is long, and the gel time of the homogel as proposed by the present invention is 2 days or more, and a practical gel strength. There is no known chemical for injecting ground into which soil can be obtained. Accordingly, an object of the present invention is to provide a chemical solution for ground injection having a long gelation time and excellent durability which can obtain practical compressive strength.

[0009]

SUMMARY OF THE INVENTION The present inventors have found that, particularly when improving the ground under the existing structure, the gelation time is extremely short so that a large number of holes are not made in the floor of the existing structure. As a result of intensive studies on a long and durable chemical solution for ground injection, a ground injection material having an extremely long gelation time and sufficient gel strength was found, and the present invention was completed. That is, the present invention provides a ground injection chemical containing an active silicic acid aqueous solution and an acidic silica sol aqueous solution as active ingredients. By using the ground injection chemical of the present invention, homogel (before ground injection) can be obtained. The gel time of a gel obtained by reacting a chemical solution in a state can be extremely long, and practical gel strength can be obtained with a low concentration of silica compared to colloidal silica grout. The compressive strength of sand gel is also practical 0.5kgf
/ Cm ² or more, and is particularly useful as a ground improvement material under the existing structure.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The ground injection chemical solution of the present invention is characterized in that an active silica aqueous solution is partially substituted for an active silica aqueous solution, or an acidic silica sol aqueous solution is used as a stabilizer. The active silicic acid aqueous solution used in the present invention is an unstable silicic acid aqueous solution which should be called a precursor of colloidal silica. A water-soluble silicate such as sodium silicate is ion-exchanged, peptized, electrophoresed, electrodialyzed, etc. To remove alkali ions, and the aqueous solution is substantially free of salt. Physically, the aqueous solution has a pH of 2
4, a silicic acid atom in an aqueous solution having at least one silanol group capable of participating in condensation, and a silicic acid condensate having a molecular weight of 1,000 or less, and having an average molecular diameter of 1 to 2 nm finer than colloidal silica. Containing silicic acid aqueous solution
The concentration of O ₂ is 12 wt% or less, preferably, preferably from 2 to 10% by weight or less. Further, in the present invention, an active silicic acid aqueous solution may be stabilized by adding an acidic reactant to the active silicic acid aqueous solution. In this case, by adjusting the pH to 2 or less, it is stable for a long time, and does not always need to be manufactured on site, and can be manufactured in a factory.

Further, the acidic silica sol used in the present invention comprises:
It is obtained by mixing a so-called water-soluble silicate such as sodium silicate and an acid such as sulfuric acid to obtain a pH in an acidic region and contains a large amount of sodium components derived from sodium silicate. In particular, as the acidic silica sol, it is preferable to use an aqueous solution that is made acidic by adding the following acidic reactant to a solution prepared by adding an alkali silicate such as sodium silicate or potassium silicate to a pH of less than 4, preferably less than pH 3. . The reason that the pH of the acidic silica sol aqueous solution is less than 4 is that the pH of the active silicic acid aqueous solution used in the present invention is usually 2 to 2.
4, the acidic silica sol aqueous solution used together is p
If it is larger than H4, the active silicic acid becomes unstable and the gelation time tends to be short, which is not preferable.

On the other hand, colloidal silica, which is widely used as a ground improvement material, is usually formed by adding a small amount of sodium ions or the like to activated silicic acid obtained by passing sodium silicate through an ion exchange resin to form a silica core, It is stabilized by condensation by a method such as adding active silicic acid to this, and has a particle diameter of usually several nm to several tens nm, pH of 4 to 10, and sol state. That is, it refers to a state in which the colloidal particles are dispersed in a liquid and shows fluidity, and is clearly different from the active silicic acid or acidic silica sol used in the present invention.

Examples of the acidic reactants used for adjusting the pH of the above-mentioned activated silicic acid and acidic silica sol include inorganic acids such as sulfuric acid, hydrochloric acid and phosphoric acid, and organic acids such as citric acid and gluconic acid. Of these, phosphoric acid, which is less affected by corrosion on the structure, is particularly preferably used. The mixing ratio of the aqueous solution of acidic silica sol to the aqueous solution of active silica is usually ₂ to 200 wt% based on the total amount of SiO _{2 in} the aqueous solution of active silica.
%, Preferably 10 to 200 wt%. The reason for this is that if the amount of the acidic silica sol is larger than 200 wt%, the Na ₂ SO ₄ component contained in the acidic silica sol is not preferable because the underground structure is corroded or the water quality changes. If the amount of SiO _{2 in} the aqueous acidic silica sol solution is less than 2% by weight, the pH of the mixed solution tends to increase, and it is difficult to obtain a long gelation time. The soil injection chemical solution according to the present invention has a pH of less than 4,
Preferably less than two are preferred. Therefore, for the purpose of adjusting the pH, the above-mentioned acidic reactant may be added later to the chemical solution of the present invention. The reason for setting the pH to less than 4 is that p
If H is larger than 4, the gelation time tends to be short. Further, the gelation time of the homogel is affected by the pH of the ground injection chemical solution.
Preferably, it is 10 days or more. In the present invention, as described above, the gelation time can be arbitrarily adjusted by adjusting the pH, and the pH adjustment may be appropriately selected according to the characteristics of the ground to be improved. The unconfined compressive strength of the consolidated sand using the chemical solution of the present invention is JIS 12
16 It is a measurement method according to the “uniaxial compression test method for soil”, and is usually preferably 0.5 kgf / cm ² or more.

Further, in addition to the above two components, inorganic salts such as aluminum sulfate, magnesium chloride, sodium hydrogen carbonate, magnesium sulfate, aluminum nitrate, aluminum phosphate, potassium chloride, calcium chloride and the like are blended as auxiliary agents. No problem. In the present invention, further, for example, sequestering materials such as EDTA, polyphosphate and polycarboxylic acid, N, N'dibutylthiourea, N, N'diethylthiourea, dibenzylsulfoxide, N-dodecylpyridium chloride, N- A corrosion inhibitor such as cetylpyridium chloride metal and a polymerization inhibitor of silicate ions such as ethylene glycol, diethylene glycol, glycerin, casein and urea may be blended.

As a method of preparing the chemical solution of the present invention, an aqueous solution of acidic silica sol may be added to the aqueous solution of active silica, or an aqueous solution of active silica may be added to the aqueous solution of acidic silica sol. Furthermore,
If necessary, the above-mentioned acidic reactant for adjusting the pH and various auxiliaries can be added to obtain the ground injection chemical solution of the present invention. The ground injection chemical solution of the present invention has an extremely long gelation time, for example, preventing liquefaction of existing structures,
It can be suitably used as a ground improvement material for strengthening the ground under the existing structure or stopping water.

Next, an injection method using the ground improvement material of the present invention will be described. The ground injection chemical solution according to the present invention,
Since the chemical solution does not solidify in the injection tube because it has a long gelation time as described above, the mixing method of the chemical solution is not particularly limited. For example, one-solution one-step injection (one-shot method) Any mixing method of two-liquid one-step injection (1.5 shot method) and two-liquid two-step injection (two shot method) may be used. A known injection method can be applied as the injection method of the chemical solution, and examples thereof include a double tube strainer method and a double tube double packer method. Further, it is also applicable to a single tube rod system by sealing the inlet of the injection tube with a packer. The chemical solution is used in the form of an acidic solution, but can be injected without a problem with a device or the like by using a commonly used acid-resistant injection machine.

The most characteristic feature of the chemical solution for ground injection of the present invention is that practical compressive strength can be obtained although the gelation time is much longer than that of the conventional one. Therefore, the ground injection chemical solution of the present invention can be injected from the outer periphery of the existing structure having a width of about 10 m so as to form a hole in the floor of the existing structure. The ground beneath can be improved without taking any additional steps.
In addition, since it can be injected into the ground at low pressure over a long period of time, there is little risk of adversely affecting existing structures and nearby areas, and the state of seepage injection can be obtained. It is possible to predict the injection range.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.
In addition, in each Example,% is weight percent.

<Preparation of aqueous solution of activated silicic acid> JIS K14
No.08 sodium silicate 3 (JIS sodium silicate 3)
Is diluted with water to adjust the SiO ₂ concentration to 3%, and 1500 mL of an aqueous sodium silicate solution is passed through 1000 mL of a cation exchange resin (Amberlite IR 120B; manufactured by Organo Co., Ltd.) to obtain an active silicic acid aqueous solution. Was. The pH of this aqueous solution was 2.5.

<Preparation of acidic silica sol> 57% sulfuric acid 70
430 L of water added to 250 L of JIS sodium silicate No. 3 water while stirring vigorously.
500 L of an aqueous sodium silicate solution to which L was added was gradually added dropwise to prepare an aqueous acidic silica sol solution. P of this aqueous solution
H was 1.5 and the total SiO ₂ concentration was 10%.

Examples 1-2: Using the active silicic acid aqueous solution obtained as described above and a 20% aqueous solution of JIS sodium silicate No. 3, liquids A and B having the compositions shown in Table 1 were prepared. In addition, the pH of the chemical solution obtained by mixing the solution A and the solution B and SiO ₂
The concentrations are shown in Table 1.

Examples 3 to 5: Using the aqueous solution of active silicic acid and the aqueous solution of acidic silica sol prepared as described above, solutions A and B having the compositions shown in Table 2 were prepared. Table 2 shows the pH and SiO ₂ concentration of the chemical solution obtained by mixing the solution A and the solution B.

[0023]

[Table 1]

[0024]

[Table 2]

Comparative Examples 1-3 Liquids A and B having the compositions shown in Table 3 were prepared using the same 30% aqueous colloidal silica solution and the same acidic silica sol aqueous solution as prepared in Examples 3-5 prepared as described above. This A
Table 3 shows the pH and SiO ₂ concentration of the chemical solution obtained by mixing the solution B and the solution B.
Shown in

[0026]

[Table 3]

<Measurement of gel time of homogel> Example 1
Each of the drug solutions prepared by mixing Solution A and Solution B prepared in Comparative Examples 1 to 5 and Comparative Examples 1 to 3 was transferred to a container, and a gelation reaction was performed at room temperature. The gelation time until a homogel was obtained was measured.
Table 4 shows the results. The gelation time was defined as the time from mixing of the chemicals to the state in which the chemicals inside no longer flow even when the container was tilted.

<Measurement of Uniaxial Compressive Strength of Sand Gel> Further, 100 mL of the chemical solution prepared by mixing the liquid A and the liquid B prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was added to 5 cmΦ × 20 cm.
The Toura standard sand was poured into the L formwork into a sand layer packed to a height of 10 cm, and a solidification reaction of the sand layer was performed (sand gel).
One day, 7 days, and 28 days after the injection of the drug solution, the uniaxial compressive strength of the sand gel was measured according to JIS A1216. Table 4 shows the results.

[0029]

[Table 4]

The samples of Examples 3 to 5 and Comparative Example 1 were not completely solidified after one day, and the uniaxial compressive strength could not be measured. From the results in Table 4, the chemical solution for ground injection of the present invention has a longer homogelation time and a higher practical compressive strength in spite of a lower silica concentration than the system using colloidal silica and acidic silica sol. It can be seen that it can be obtained.

[0031]

As described above, the chemical solution for ground injection according to the present invention contains an active silicic acid aqueous solution and an aqueous solution of acidic silica sol as active ingredients, and the gelation time of the homogel is 2 days or more compared to the conventional chemical solution for ground injection. That is a very long time,
Nevertheless, a sufficiently practical compressive strength of 1.0 kgf / cm ² or more can be obtained. The content of water-soluble salts such as Na ₂ SO ₄ can be reduced as compared with a conventional acidic silica sol-based chemical solution, the durability can be improved as compared with an acidic silica sol, and it can be supplied at a lower cost than a colloidal silica-based chemical solution. In addition, since a chemical solution having an extremely long gel time can be prepared, if the existing structure has a width of up to about 10 m,
Chemical solution can be injected from the outer periphery of the structure at low pressure for a long time,
It is possible to reinforce the ground under the existing structure and stop water without causing harmful deformation to the existing structure or nearby incidental facilities.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Sekine 9-11-1, Kameido, Koto-ku, Tokyo Nippon Kagaku Kogyo Co., Ltd. Research and Development Headquarters (72) Inventor Shigeru Tsukahara 9-11 Kameido, Koto-ku, Tokyo No. 1 Nippon Kagaku Kogyo Co., Ltd. Research and Development Headquarters (72) Inventor Yasuhiro Abe 9-11-1, Kameido, Koto-ku, Tokyo Nippon Kagaku Kogyo Co., Ltd. Research and Development Headquarters (72) Inventor Yoshiro Kaneda Tokyo 9-11-1, Kameido, Koto-ku Nippon Kagaku Kogyo Co., Ltd. Research and Development Division F-term (reference) 4H026 CA03 CB01 CB03 CB06

Claims (4)

[Claims] 1. A ground injection chemical solution comprising an active silicic acid aqueous solution and an acidic silica sol aqueous solution as active ingredients. 2. The ground injection chemical according to claim 1, wherein the mixing ratio of the acidic silica sol aqueous solution is ₂ to 200% by weight of the total SiO ₂ in the active silicic acid aqueous solution. 3. The ground injection chemical according to claim 1, wherein the pH of the ground injection chemical is less than 4. 4. The method according to claim 1, further comprising an inorganic salt.
Or the chemical | medical solution for ground injection as described in 3.