JP2000109835A - Chemical liquid to be injected in soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily design gel time, improve consolidation durability and prevent pollution of groundwater and corrosion of an underground structure 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 and pH thereof is preferably less than 4. An acidic reactive agent is preferably added to the aqueous solution of active silicic acid to adjust pH at a value not more than 2 whereby the aqueous solution keeps stability for a long term and production not in site but in plant is enabled. The acidic reactive agent is preferably phosphoric acid. The amount of water glass to be added to the aqueous solution of active silicic acid in preparing a chemical liquid to be injected to soil is 25-300 wt.% of the amount of total SiO2 existing in the aqueous solution of active silicic acid. Gel time can be arbitrarily and widely changed by changing a mixing ratio thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical for improving the ground, and more particularly to a method for easily setting a gelling time, having excellent consolidation durability and good permeability, and contaminating groundwater. The present invention relates to a chemical solution for ground injection without a solid.

[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, those prepared to be acidic are those produced by the reaction between water glass and a curing agent.
Water-soluble salts such as a ₂ SO ₄ will be eluted even after the chemical solution has solidified, and therefore, may corrode underground structures,
Alternatively, there is an environmental problem such as a change in groundwater 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 composed of an acidic colloidal silica obtained by mixing a colloidal solution of silicic acid and an acidic reactant and water glass (Japanese Patent Publication No. 7-10977), a colloidal solution of silicic acid, an acid and an alkali metal For ground injection obtained by mixing a water-soluble salt (Japanese Patent Publication No. 64-8677), and a ground injection material comprising a colloidal solution of silica and silicate obtained by mixing water glass and an acid reactant (Japanese Patent Publication No. Hei 6-86). -744
No. 21) has been proposed. The colloidal silica referred to here is a commercial product generally referred to as silica sol, which is generally obtained by stabilizing activated silicic acid obtained by passing sodium silicate through an ion exchange resin by heating or the like. Thicknesses of up to 20 nm are usually used.

[0004]

However, these ground injection materials containing colloidal silica as a main component have no problem in durability, but in order to exhibit practical consolidation strength, a high-concentration silica component is required. In addition to the necessity, colloidal silica is obtained by stabilizing active silicic acid by a complicated operation as described above, and is disadvantageous because the production process is industrially complicated. In addition, an injection method for ground improvement requires a gelling time for solidifying which is short to an extremely long one depending on the condition of use. For example, when performing extremely unstable parts of the ground, a method of solidifying in a short time is required.When improving the ground below the structure, a chemical solution is injected from around the structure to improve the structure. A long consolidation time is required to penetrate and improve the lower part of the steel.
Therefore, an object of the present invention is to provide a chemical solution for injecting ground into which the gelation time can be easily set, the solidification durability is excellent, and there is no risk of contamination of groundwater or corrosion of the underground structure.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a ground injection chemical solution which achieves the above object, and more specifically, to a ground injection liquid solution containing an active silicic acid aqueous solution and water glass as effective components.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The chemical solution for ground injection according to the present invention is characterized in that an active silicic acid aqueous solution as a main agent and water glass as a curing agent are used as active ingredients. 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, and a water-soluble silicate such as sodium silicate is subjected to an ion exchange method.
It is obtained by removing alkali ions by electrophoresis, electrodialysis, or the like, and the aqueous solution does not substantially contain a salt. Physically, the pH of the aqueous solution
2 to 4 silicic acid atoms in an aqueous solution having at least one silanol group capable of participating in condensation and having an average molecular diameter of 1 to 2 nm which is finer than colloidal silica in a silicic acid aqueous solution having a molecular weight of 1,000 or less. An aqueous solution of silicic acid containing the body,
The concentration of SiO ₂ is 12% by weight or less, preferably 2 to 1%.
Those having 0% by weight or less are preferred. The pH of the active silicic acid aqueous solution used in the present invention is preferably less than 4, preferably 2 or less.

In the present invention, it is preferable to use an active silicic acid aqueous solution whose pH is adjusted to 2 or less by adding an acidic reactant to the active silicic acid aqueous solution. When the pH of the active silicic acid aqueous solution is adjusted to 2 or less by adding an acidic reactant to the active silicic acid aqueous solution in this way, it is stable for a long time, and it is not always necessary to produce it on site, and it can be produced in a factory. As the acidic reactant, for example, sulfuric acid,
Examples thereof include inorganic acids such as hydrochloric acid and phosphoric acid, and organic acids such as citric acid and gluconic acid. Among them, phosphoric acid, which has a small influence of corrosion on the structure, is particularly preferably used.

The active silicic acid aqueous solution of the present invention is different from acidic silica sol and colloidal silica. The acidic silica sol 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 component derived from sodium silicate. Colloidal silica is usually obtained by adding a small amount of sodium ions to active silicic acid obtained through sodium silicate to an ion exchange resin and heating to form a core of silica, and further adding active silicic acid thereto to stabilize it. Stabilized by condensation, usually several nm to several tens nm
Having a particle diameter of 4 to 10 and a sol state, that is, a state in which colloid particles are dispersed in a liquid and exhibit fluidity.

The water glass used in the present invention is not particularly limited. For example, sodium silicate No. 3 and sodium silicate 4 specified in JIS K1408 (hereinafter referred to as JIS sodium silicate 3 and JIS sodium silicate 4). ) Etc. can be used. Also, when producing an aqueous solution of activated silicic acid,
An aqueous sodium silicate solution that is partially ion-exchanged from the ion-exchange resin and discharged may be used.

In the chemical solution for injection into the ground of the present invention, the mixing ratio of water glass to the aqueous solution of activated silica is 25 to 300 wt% based on the total amount of SiO _{2 in} the aqueous solution of activated silica.
%, Preferably 30 to 250 wt%, and the gelation time can be changed arbitrarily and widely by changing the compounding ratio of the two components. You can set the percentage. The gelling time of this chemical solution tends to increase as the pH decreases, and the gelation time of a homogel (a gel solidified by reacting the chemical solution before injection into the ground) is 1
It can be set from 5 minutes to 300 hours.

In the present invention, in addition to the above two components, auxiliary agents such as salts of alkali metals, alkaline earth metals, aluminum carbonates, acid carbonates, sulfates, acid sulfates, chlorides, alkali metals, Alkaline earth metals, hydroxides of aluminum, or these metal oxides that become hydroxides in water may be blended. In the present invention,
Further, sequestering materials such as EDTA, polyphosphate, polycarboxylic acid, N, N'dibutylthiourea,
N, N'diethylthiourea, dibenzylsulfoxide,
A corrosion inhibitor such as N-dodecylpyridium chloride and N-cetylpyridium chloride metal, and a polymerization inhibitor of silicate ions such as ethylene glycol, diethylene glycol, glycerin, casein, and urea may be blended.

[0012] Compared with the conventional grout using an aqueous solution of acidic silicic acid obtained by adding water glass to an acidic solution, the chemical solution for ground injection according to the present invention not only has excellent durability but also causes environmental problems. Absent. In addition, compared with a glaucoma containing colloidal silica as a main component, a low-concentration SiO ₂ and a high consolidation strength can be obtained, and the gelation time can be arbitrarily set.
Due to such features, the ground injection chemical liquid of the present invention is further required for the purpose of increasing durability of the foundation ground, strengthening the ground, and requiring durability such as waterproofing work for embankments and tunnels. Can be applied to long-term temporary works such as excavating several years after pouring, has better permeability than conventional grout, has better consolidation strength, and has less secondary pollution.

[0013]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. In addition, in each Example,% is weight percent. <Preparation of Active Silicic Acid Aqueous Solution> 1500 mL of a sodium silicate aqueous solution prepared by diluting JIS Sodium Silicate No. 3 with water to adjust the concentration of SiO ₂ to 3% was prepared using a cation exchange resin (Amberlite IR 120B; manufactured by Organo Corporation). ) 1000m
L to obtain an aqueous solution of activated silicic acid. The pH of this aqueous solution was 2.5.

Examples 1 to 11: Using the active silicic acid aqueous solution obtained above, a 15% aqueous phosphoric acid solution, and water glass (20% solution of JIS sodium silicate 3), liquids A and B having the compositions shown in Table 1 A liquid was prepared. Table 1 shows the pH and the SiO ₂ concentration of the ground injection chemical solution obtained by mixing the solution A and the solution B.

Comparative Examples 1 to 8: Similarly, 30% colloidal silica, 15% phosphoric acid aqueous solution, water glass (JIS
Solution A and Solution B having the compositions shown in Table 2 were prepared using sodium silicate No. 3 (20% solution). Table 2 shows the pH and SiO ₂ concentration of the ground injection chemical solution obtained by mixing the solution A and the solution B.

[0016]

[Table 1]

[0017]

[Table 2]

<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 8 and Comparative Examples 1 to 8 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 3 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 Unconfined Compressive Strength of Sand Gel> Also, 100 mL of the chemical solution prepared by mixing the solution A and the solution B prepared in Examples 1 to 11 and Comparative Examples 1 to 8 was added to 5 cmΦ × 20 c
The Toura standard sand was poured into a mold having a capacity of 10 cm and poured into a sand layer, 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 3 shows the results.

[0020]

[Table 3]

Examples 2, 10, 11 and Comparative Examples 7,
Regarding the sample No. 8, the solidification was not completed yet after one day, and the uniaxial compressive strength could not be measured. Examples 7, 8 and 9
In the samples of the above, only the gel time was measured. From the results in Table 3, the chemical solution for ground injection according to the present invention can obtain practically-consolidated sand strength at a lower concentration of SiO ₂ than the colloidal silica-water glass grout. The gelation time can be arbitrarily set depending on the mixing ratio of the water glass and the pH.

[0022]

As described above, the chemical solution for ground injection according to the present invention contains an active silicic acid aqueous solution and water glass as effective components, and is practically usable even at a lower SiO2 concentration than conventional colloidal silica grout. The consolidated strength of the consolidated sand is obtained, and the gel time can be arbitrarily and easily set within a range from several minutes to several days. In addition, since it can be manufactured by a simpler process and apparatus than a colloidal silica grout, it can be supplied in a larger amount and at a lower cost than a colloidal silica chemical. Furthermore, since the alkali content can be reduced as compared with the water glass type chemical solution,
It surpasses durability. Therefore, it can also be applied to long-term temporary construction such as increasing the bearing capacity of the foundation ground, strengthening the ground, waterproofing works such as embankments and tunnels, and excavating and excavating several years after injection. It has better penetration than conventional grafts, and has better consolidation strength and less secondary contamination.

 ──────────────────────────────────────────────────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 F-term in the Research & Development Division of Nippon Kagaku Kogyo Co., Ltd. 2D040 AA04 AB01 BB09 CA02 CA10 CB03 CC01 4H026 CA03 CB01 CB06 CB08

Claims (5)

[Claims] 1. A ground injection chemical comprising an active silicic acid aqueous solution and water glass as active ingredients. _2. The chemical liquid for injecting ground according to claim 1, wherein the mixing ratio of the water glass is 25 to 300% by weight of SiO _{2 in} the aqueous solution of activated silicic acid. 3. The chemical for injection into the ground according to claim 1, wherein the pH of the aqueous solution of activated silicic acid is 4 or less. 4. The ground injection chemical according to claim 1, further comprising an acidic reactant. 5. The chemical for ground injection according to claim 4, wherein the acidic reactant is one or more kinds selected from sulfuric acid, hydrochloric acid, phosphoric acid, citric acid, and gluconic acid.