JPH11269458A - Grout for ground injection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grout of which the homogel has a very long gelling time and which exhibits a gel strength practically enough by using, as effective components, an aq. active silicic acid soln. and an acidic reactant. SOLUTION: This grout is prepd. by adding at least one acidic reactant selected from phosphoric, sulfuric, hydrochloric, and citric acids, etc., to an aq. active silicic acid soln. to adjust the pH to lower than 2. If necessary, a sequestering agent (e.g. a polyphosphate), a metal corrosion preventive (e.g. N,N-dibutylthiourea), and a polymn. inhibitor (e.g. glycerin) are incorporated into the grout. The gelling time of the homogel is at least 5 days, and the unconfiend compression strength of solidified sand is 0.5 kg/cm<2> or higher. The aq. active silicic acid soln. is prepd. by removing alkali ions from a water- soluble silicate (e.g. sodium silicate) by an ion-exchange method, etc., has at least one silanol group capable of participating in condesation in an aq. soln. at a pH of 2-4, and has a mol.wt. of 1,000 or lower, an average particle size of 1-2 nm, and an SiO2 concn. of 12 wt.% or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical for injecting ground, which is particularly useful as a ground improvement material for strengthening the ground under an existing structure, stopping water and / or preventing liquefaction, and more specifically, colloidal silica or The present invention relates to a liquid for ground injection having a longer gelation time than a conventional injection method using an acidic silica sol or the like.

[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,
Aldehydes, esters, such as ethylene carbonate, have been used. However, the method of using water glass is
As already introduced in many documents, the durability and the like are insufficient, and only the value as a temporary material is recognized. 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 in an extremely short time, so that the method of application as the injection material is limited. Also adjusted to acidic (acidic silica sol)
There are environmental problems such as salts such as Na ₂ SO ₄ generated by the reaction between the water glass and the hardener corroding underground structures or changing the quality of groundwater due to the elution of these salts.

[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). Japanese Patent Application Laid-Open No. 64-8677), a colloidal silica solution obtained by mixing a colloidal solution of silicic acid and an acidic reactant and a water glass, and a colloidal solution of silicic acid and an acidic reactant. For injecting ground, which comprises acidic colloidal silica and water glass obtained as described above (Japanese Patent Publication No. 7-10977).

The colloidal silica referred to here is a commercial product generally called silica sol, which is obtained by stabilizing activated silicic acid obtained by passing sodium silicate through an ion exchange resin by heating or the like. Average particle size is 10-2
The one with 0 nm is usually used. On the other hand, apart from acidic silica sol and colloidal silica, some ground improvement materials using an active silicic acid aqueous solution as a main component have been proposed. For example,
JP-B-3-20430 and JP-B1-55679
The publication discloses an aqueous solution of active silicic acid (p.
H2 to 4) have been proposed as ground improvement materials, but these improvers are injected near neutrality, and the gelation time of the homogel is substantially several at the longest. About an hour. These conventionally proposed chemical solutions have a gelation time of about 20 hours even if they have a long gelation time. Therefore, the amount of the chemical solution that can be injected from one injection port is about several m ³ , and the improvement range of the ground is at most an injection hole. 1m radius from
Limited to nearby. For this reason, when improving the ground under an existing structure having a width of several meters, it is necessary to make many holes in the floor of the existing structure, and to improve the ground by complicated means such as pouring a chemical solution into it. Construction has to be done.

[0005]

When a chemical injection method is used as a measure to prevent liquefaction of the ground of an existing structure,
In order to further simplify the operation, it is necessary to greatly increase the penetration distance of the chemical solution into the ground. For this reason, there is a demand for a ground injection chemical solution having an extremely long gelation time. In addition, the injection material containing water glass or acidic silica sol as a main component has a problem of adversely affecting the durability of itself and the durability of a structure in contact with the injection material, and the injection material containing colloidal silica as a main component is activated silica. However, there is a problem in that the gel strength is lower than that of the injection material containing as a main component, and the longer the gelation time, the lower the gel strength. In addition, the gelation time of various injection materials that have been proposed so far is as long as 2 at most.
There has been no known chemical solution for ground injection in which the time is limited to 0 hours, the gelation time to homogel is as long as 5 days or more, and a practical gelation strength is obtained. Here, the homogel refers to a gel obtained by reacting a chemical solution comprising a main agent and a curing agent before injecting into a ground. As described above, an object of the present invention is to provide a chemical solution for ground injection, which has an extremely long gelation time and at the same time obtains practical compressive strength.

[0006]

Means for Solving the Problems The present inventors have found that even when improving the ground under the existing structure, the gelation time can be extremely reduced without making many holes in the floor of the existing structure. Intensive research was conducted on long ground injection chemicals. As a result, an active silicic acid aqueous solution substantially free of salts and a chemical solution for ground injection containing an acidic reactant as an active ingredient have an extremely long homogelation time, and a practical gel strength is obtained. , Even when the drug solution is injected into the soil,
The gelation time can be at least one day or more, and at the same time, the compressive strength of the sand gel (solidified by infiltrating the ground liquid into sand) is practically 0.5 kgf / cm ^2.
The inventors have obtained the above-mentioned materials, and found that they are particularly useful as a ground improvement material under the existing structure, and have completed the present invention. That is, the present invention provides a ground injection chemical solution containing an active silicic acid aqueous solution and an acidic reactant as active ingredients.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The chemical for injection into the ground according to the present invention is characterized in that an active silicic acid aqueous solution and an acidic reactant are used as active ingredients. Here, the active silicic acid aqueous solution is different from an acidic silica sol or colloidal silica as follows. 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 5n
It has a particle size of m to several tens of nm and a pH of 4 to 5, and refers to a sol state, that is, a state in which colloid particles are dispersed in a liquid and exhibit fluidity.

On the other hand, the active silicic acid aqueous solution used in the present invention is a precursor of colloidal silica, and is an unstable silicic acid aqueous solution, which is obtained by ion exchange or peptization from a water-soluble silicate such as sodium silicate. It is preferably obtained by removing alkali ions by electrophoresis, electrodialysis, or the like, and the aqueous solution preferably does not substantially contain a salt or alkali ion. Physically, this aqueous solution has a pH of 2 to 4, and the silicate atom in the aqueous solution has at least one silanol group capable of participating in condensation, has a molecular weight of at most 1,000 or less, and has an average molecular diameter smaller than that of colloidal silica. An aqueous solution of silicic acid containing a silicic acid condensate of 1 to ₂ nm in which the concentration of SiO ₂ is 12% by weight or less and
% By weight or less is preferred.

The acidic reactant of the present invention is an acidic substance having a higher acidity than silicic acid. Examples of the acidic reactant that can be used in the present invention include inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, and organic acids such as citric acid and gluconic acid. One or more of these are used. Of these, phosphoric acid, which is less affected by corrosion on the structure, is particularly preferably used. The chemical solution for ground injection according to the present invention is obtained by adding an acidic reactant to the above-mentioned aqueous solution of activated silicic acid to lower the pH to less than 2, and preferably having a pH of 1.5 or less. The reason is that when the pH is higher than 2, the gelation time tends to be short, and a sufficient gelation time cannot be secured. The time for gelation into a homogel is affected by the pH of the ground injection chemical solution, the concentration of silicic acid in the aqueous solution of active silicic acid, or the amount of salt remaining in the solution, but is usually 5 days or more. As described above, by adjusting the pH of the chemical solution for ground injection according to the present invention to 2 or less with an acidic reactant, the gelation time could be significantly extended as compared with the conventional one. The adjustment of the pH may be appropriately selected depending on the purpose of the injection, the construction conditions, and the characteristics of the ground to be improved. Further, the soil injection chemical solution of the present invention, depending on the content of alkali components such as alkali metal salts such as sodium and potassium, calcium, magnesium and the like in the ground, when injected into soil, However, by appropriately selecting the aqueous solution of the active silicic acid and the acidic reactant and adjusting the pH, the gelation time can be at least 1 day or more and 2 days or more. In this case, JISA121
6 The unconfined compression strength of consolidated sand measured according to the “Unconfined compression test method for soil” is 0.5 kgf / cm ² or more, and in many cases 1.0 kgf / cm ² or more, which is usually necessary for practical use. A material having a strength of 0.5 kgf / cm ² or more can be obtained.
Moreover, the chemical | medical solution for ground injection of this invention has the characteristic that polymerization of silicic acid is suppressed by adding an acid stronger than silicic acid to the active unstable aqueous silicate solution, and the stability of chemical | medical solution itself is improved.

In the present invention, as other components of the above two components, for example, sequestering materials such as EDTA, polyphosphate, polycarboxylic acid, NN 'dibutylthiourea, NN'
Metal corrosion inhibitors such as diethylthiourea, dibenzylsulfoxide, N-dodecylpyridium chloride, N-cetylpyridium chloride, and silicate ion polymerization inhibitors such as ethylene glycol, diethylene glycol, glycerin, casein, and urea are incorporated. No problem. The chemical solution for ground injection according to the present invention can extremely increase the gelation time as compared with the conventional one, so that, for example, the strengthening of the ground under the existing structure, the prevention of liquefaction, and the prevention of water stoppage, etc. It can be suitably used as a ground improvement material.

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,
As described above, since the gelling time is sufficiently long, there is no possibility that the chemical solution is solidified in the storage tank or the injection pipe. Therefore, the mixing method of the chemical solution is not particularly limited. Any mixing method of (one-shot method), two-solution one-step injection (1.5 shot method), and two-liquid two-step injection (two-shot method) may be used. As a method of injecting the chemical solution as the ground improvement material of the present invention, a known injection method can be applied, and examples thereof include a double pipe strainer method and a double pipe 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. By using a commonly used acid-resistant injection machine, the chemical solution can be injected without causing any particular problem such as corrosion in the apparatus and the like.

[0012] Soil injection drug solution of the present invention, be practical gel time than as in was about 20 hours at most conventional, is very long and 2-10 days or more The greatest feature is that a practical compressive strength can be obtained at the same time. Therefore, in the case of an existing structure having a width of about 10 m, it is possible to improve the entire ground under the structure by injecting the chemical from the outer periphery of the structure over time. it can. In addition, since it can be generally injected into the ground at low pressure over a long period of time, there is little risk of adverse effects on existing structures and nearby areas, and since the state of infiltration injection can be obtained, analysis by infiltration theory is easy. And the injection range can be predicted.

[0013]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Examples 1 to 6: Sodium silicate JIS No. 3 was diluted with water, and 1500 ml of an aqueous sodium silicate solution adjusted to a SiO ₂ concentration of 5% was added to a cation exchange resin (Amberlite).
IR 120B (manufactured by Organo Co., Ltd.) to give an active silicic acid aqueous solution. The pH of this aqueous solution is 2.
It was 5. Also, 10 ml of 75% phosphoric acid and 90 ml of water
Was added to prepare a phosphoric acid diluted solution. Next, the active silicic acid aqueous solution and the phosphoric acid diluent were mixed in various ratios, and after measuring the pH of the aqueous solution, the aqueous solution was stored in a container at room temperature and the gelation time of the homogel was observed. Gelation time, after mixing the active silicic acid aqueous solution and phosphoric acid diluent,
The number of days until the chemical solution in the container did not flow even when the container was tilted was determined. On the other hand, a mixture of 100 ml of this aqueous solution and 100 ml of Toyoura standard sand was placed in a container and stored at room temperature, and the gelation time was observed. Similarly, the gel time in this case was determined by the number of days until the liquid medicine in the container did not flow even when the container was tilted. In addition, the sand gel strength 28 days after the sample preparation was measured. The results are shown in Table 1. In the table, the strength of the sand gel was determined by filling standard sand to a height of 10 cm in a mold having a size of 5 cmφ × 20 cmL, pouring a predetermined mixture, and allowing the mixture to stand.
It was determined by measuring according to SA1216.

[0015]

[Table 1]

Comparative Example 1: Sodium silicate aqueous solution 15 prepared by diluting sodium silicate JIS No. 3 with water and adjusting the concentration of SiO ₂ to 5%.
00 ml of cation exchange resin (Amberlite IR
120B (manufactured by Organo Corporation) to give an active silicic acid aqueous solution. The pH of this aqueous solution was 2.5. When 100 ml of this aqueous solution was stored in a container, it gelled after 2 days. A mixture of 100 ml of this aqueous solution and 100 ml of Toyoura standard sand was put in a container and stored, and gelled after 12 hours. In addition, the sand gel strength after gelation for 28 days was 1.4 kgf / cm ² .

Comparative Examples 2 to 5: The aqueous solution of activated silicic acid obtained in Comparative Example 1 and ion-exchanged water were mixed at various ratios, and the pH of each aqueous solution was measured. After storage, the gelation time of the homogel was observed in the same manner as in the examples. On the other hand, a mixture of 100 ml of this aqueous solution and 100 ml of Toyoura standard sand was placed in a container, stored at room temperature, and the gelation time was observed in the same manner as in the examples.
The sand gel strength 28 days after the sample preparation was measured in the same manner as in the example. Table 2 shows the results.

[0018]

[Table 2]

As is clear from the above results, the drug solution of the present invention can achieve a gelation time of at least 15 days with a homogel and at least 5 days with a sandgel, while at the same time obtaining a gel having sufficient sandgel strength. In the conventional method using an aqueous solution of activated silicic acid having a pH of 2 or more, a sufficient gelation time cannot be obtained.

Example 7 Sand (silica sand No. 8) was inserted into a pipe having an inner diameter of 52 mm and a total length of 20 m.
Was filled, and the medicinal solution for ground injection prepared in Example 6 was injected under pressure, and the permeability of the medicinal solution was measured. The injection pressure of the drug solution was set at a constant pressure of 7.0 kg / cm ² for 30 minutes from the start, in order to perform the relationship between the injection time and the permeation distance of the drug solution in an approximate state at the time of the actual injection. The test was performed by gradually decreasing the permeation speed of the permeation tip of the chemical solution. The result is shown in FIG. As is clear from the results, when the chemical solution for ground injection of the present invention was used, the chemical solution penetrated to a distance of about 400 cm in about 2400 minutes (40 hours).

[0021]

According to the chemical solution for injection into the ground of the present invention containing an active silicic acid aqueous solution substantially free of salt and an acidic reactant as active ingredients, the gelling time of the homogel is 5 days or more, and Considering the shortening of the gelation time due to the reaction between the gel and the chemical solution, the time can be set to about 2 days or more, and an extremely long permeation period can be maintained. In addition, when the solution is injected under pressure, it is possible to penetrate the drug solution with a penetration distance of about 5 m. As a result, in the case of an existing structure having a width of about 10 m, by injecting a chemical solution from the outer periphery of the structure at a low pressure over a long period of time, without causing harmful deformation to the existing structure or nearby incidental facilities. Therefore, it is possible to strengthen the ground under the existing structure and to stop water.

[0022]

[Brief description of the drawings]

FIG. 1 is a view showing the elapsed time, the permeation length of a chemical solution, and the measurement results of the injection pressure when the chemical solution for ground injection prepared in Example 6 was injected under pressure into sand.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuki Abe 9-11-1, Kameido, Koto-ku, Tokyo Inside Nippon Kagaku Kogyo Co., Ltd. (72) Inventor Shigeru Tsukahara 9-11-1, Kameido, Koto-ku, Tokyo Nippon Kagaku Kogyo Co., Ltd.

Claims (3)

[Claims] 1. A ground injection chemical comprising an active silicic acid aqueous solution and an acidic reactant as active ingredients. 2. The ground injection chemical according to claim 1, wherein the pH of the ground injection chemical is less than 2. 3. The acid reactant is one or two selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, citric acid, and gluconic acid.
The chemical solution for injecting into the ground according to claim 1 or 2, which is at least one kind of acid.