JP2011116829A - Grouting material and grouting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grouting material and a grouting method superior even in keeping water quality, providing the foundation improvement effect without causing the problem of remaining of excessive acids, by enabling uniform grouting into the ground, while preventing separation and precipitation of a hardly-soluble alkali agent. <P>SOLUTION: This grouting material presents acidic to neutral property. The grouting material is formed by mixing a liquid A and a liquid B. The liquid A is acidic silica sol obtained by mixing water glass with an acidic liquid, and the liquid B is a mixed liquid obtained by mixing water glass with magnesium hydroxide. In the grouting method, the grouting material is injected into the ground. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ground injection material and a ground injection method (hereinafter also simply referred to as “injection material” and “injection method”), and more particularly, to a ground injection used for the purpose of strengthening soft ground or stopping water in a leaked ground. It relates to materials and ground injection method.

  Conventionally, various solution-type grouts mainly composed of water glass are known as grouts used for ground improvement such as soft ground. Above all, in the ground injection method in which silica sol is gelled in an acidic or neutral region, conventionally, an acidic liquid and water glass are used, and water glass is added to the acidic liquid so as to maintain an acid-excess state. A two-step method in which a strong acidic silicic acid aqueous solution having a pH of about 1 to 2 is prepared while mixing both solutions, and then a pH adjuster is added to the aqueous solution to shift the pH in a neutral direction for injection. Was taken.

  However, although it is easy to prepare a strongly acidic silicic acid aqueous solution having a pH of 1 to 2 by adding water glass to the acidic liquid, the pH value is similarly set to a constant value in the intermediate region of 2 to 7, Generally very difficult. That is, in this intermediate region, the gel time changes greatly due to slight fluctuations in pH, and therefore it is very difficult to perform injection by selecting a gel time corresponding to a predetermined pH. On the other hand, a technique of mixing a non-alkaline silicic acid aqueous solution (acidic silica sol) obtained by treating water glass with sulfuric acid and magnesium hydroxide has been proposed by the present applicant (see Patent Document 1).

  Further, for example, Patent Document 2 discloses a ground injection method using a non-alkaline silicic acid aqueous solution obtained by mixing a water glass aqueous solution containing a slow-acting alkaline agent in advance and an acidic solution as a chemical solution for ground injection. Has been. Furthermore, Patent Document 3 discloses an injection method by which the present applicant mixes and gels water glass obtained by adding calcium carbonate to an acidic silicic acid aqueous solution. In addition, a method of injecting an acid neutralizer into the ground in advance before injecting acidic silica sol grout is also known.

Japanese Patent Publication No. 2-47514 (Claims etc.) Japanese Patent Publication No. 3-54154 (claims, etc.) Japanese Patent Publication No. 5-4431 (claims, etc.)

  According to the technique described in Patent Document 1, the effect that the gelation time can be easily adjusted and the solidified body can have high strength can be obtained. On the other hand, the hardly soluble alkali agent is acidic. There has been a problem that separation may occur in silica sol or in water. For this reason, neutralization occurs only in the vicinity of the injection port, does not appear in a wide range, the acidic silica sol spreads in the ground, and the tip is diluted with water, resulting in incomplete gelation or strength However, there is a problem that groundwater tends to be acidic or the groundwater tends to be acidic.

  Also in the technique according to Patent Document 2, if the chemical solution is allowed to stand, the alkaline agent is immediately separated into the bottom, and when it is poured into the long mold, the alkaline agent is separated in the vicinity of the injection port. There was a tendency to end up. Furthermore, in the method according to Patent Document 3, calcium carbonate in the water glass reacts with the acid in the acidic water glass to generate carbon dioxide gas, and precipitates are generated to inhibit permeation, or the injection ground is in a porous state. For example, the strength may be lowered or the strength may be reduced. Furthermore, in the method of injecting an acid silica sol after previously injecting an acid neutralizer such as a hardly soluble alkali agent into the ground, the hardly soluble alkali agent is separated in the ground and precipitates near the injection port. It did not spread over a wide area, so most of the acidic silica sol spread into the ground as it was, and excess acid remained in the ground.

  As mentioned above, when the poorly soluble alkaline agent is separated and settled in the injection material, when injected into the ground, the poorly soluble alkaline agent accumulates in the ground near the injection port and is injected evenly into the ground. In addition, the acidic silica solution with a long acid-excess gelation time diffuses over a wide area and is diluted in the groundwater, and the desired ground improvement effect cannot be obtained. This will cause problems. Further, when carbonate is used as the hardly soluble alkali agent, carbon dioxide gas is generated, which causes a problem in terms of penetration and strength. Therefore, there has been a demand for the realization of a ground injection material and a ground injection method capable of performing injection without causing separation and precipitation of a hardly soluble alkaline agent in the injection material and without generating gas.

  Therefore, the object of the present invention is to solve the above-mentioned problems, and to prevent the separation and precipitation of the hardly soluble alkaline agent, and to perform homogeneous injection into the ground without causing problems such as residual acid. The purpose of the present invention is to provide a ground injection material and a ground injection method capable of obtaining a desired ground improvement effect.

  As a result of diligent study, the inventors of the present invention used magnesium hydroxide that does not generate carbon dioxide gas due to acid as a hardly soluble alkaline agent, and this magnesium hydroxide was previously mixed with water glass, The inventors have found that the above problem can be solved by using a method of mixing with an acidic silica sol obtained from water glass and an acidic liquid, and have completed the present invention.

  That is, the ground injecting material of the present invention is a ground injecting material that exhibits acidity to neutrality, and an acidic silica sol obtained by mixing water glass and acidic liquid is used as A liquid, and water glass and magnesium hydroxide are mixed. The liquid mixture obtained by mixing is liquid B, and liquid A and liquid B are mixed.

  Further, the ground injection method of the present invention uses an acidic silica sol obtained by mixing water glass and acidic liquid as liquid A, and a liquid mixture obtained by mixing water glass and magnesium hydroxide as liquid B. A ground injecting material obtained by mixing the liquid and the B liquid and exhibiting acidity to neutrality is injected into the ground.

  According to the present invention, magnesium hydroxide is preliminarily mixed with water glass so that magnesium hydroxide floats in the acidic silica sol, so that separation and precipitation of magnesium hydroxide can be prevented. it can. In addition, after mixing this mixed solution with acidic silica sol, the effect of magnesium hydroxide can be obtained by the action of magnesium hydroxide without causing gas generation, and the effect of gradually shifting from an acid-rich state to a neutral direction can be obtained. Similarly, the effect of shifting to the neutral direction can be obtained before and after, and the occurrence of acid pollution can be prevented. Furthermore, the gelation is more stable than in the conventional method, and magnesium hydroxide is dispersed in the silica solution at the tip that has permeated into the ground. Gelation time and strength can be obtained. Furthermore, the injection material can be uniformly injected into the ground, and the infiltration distance in the ground can be set more firmly and solidified, and the entire injection region can be consolidated without causing a decrease in strength. .

It is the schematic which shows the experimental apparatus used in the Example. It is a graph which shows the relationship between osmotic distance and uniaxial compressive strength of a specimen. It is a graph which shows the relationship between osmosis distance and pH of a specimen.

Hereinafter, embodiments of the present invention will be described in detail.
In the present invention, acidic silica sol obtained by mixing water glass and acidic liquid is designated as A liquid, mixed liquid obtained by mixing water glass and magnesium hydroxide is designated as B liquid, and A liquid and B liquid Is mixed to obtain a ground injection material exhibiting neutrality from acidity, and this is injected into the ground.

  In the present invention, a mixed liquid (liquid B) in which magnesium hydroxide is mixed with water glass in advance and an acidic silica sol (liquid A) are mixed. In this mixed solution (Liquid B), water glass and magnesium hydroxide are combined to form a micellar silica solution. Therefore, magnesium hydroxide is suspended in this silica solution, and the liquid becomes cloudy. The acid-excess acidic silica sol obtained by mixing the silica solution and the acidic silica sol aqueous solution is gradually neutralized by the alkali and magnesium hydroxide of the water glass. The effect of shifting to is shown.

  Specifically, in the present invention, by mixing the acidic silica sol (liquid A) and the silica solution (liquid B), the acidic silica sol and the silica of micelles composed of water glass and magnesium hydroxide are gradually dissolved. In response to gelation, gelation occurs, and the reaction with magnesium hydroxide continues even after gelation and reaches the neutral region.

  Here, when the liquid A and the liquid B are mixed and injected into the ground, the magnesium hydroxide permeates the soil particles in a wide range from the injection port while being uniformly dispersed in the injection material, so that the injection range is made uniform. Move to neutral and solidify. The reason is that the liquid A forms an acidic silica sol by mixing water glass and acid, and the liquid B is mixed with water glass and magnesium hydroxide so that water glass is surrounded around the magnesium hydroxide fine particles. Forms a white sol in which the silica molecules are entangled, and the two sols are dispersed in the aqueous solution while resisting each other, so it has excellent dispersibility, and magnesium hydroxide separates and precipitates even when injected into the ground Without spreading, the excess acid in the acidic silica sol causes a neutralization reaction with the alkali in the sol of the B liquid, and the gelation gradually proceeds to gel, and after the gelation, The magnesium hydroxide dissolves and neutralizes the excess acid in the gel to neutralize the gel. Furthermore, the magnesium hydroxide reacts with the acid like calcium carbonate to react with the carbon. Since no gas is believed to be due to a possible homogenous consolidation.

  In the injection material of the present invention, after being injected into the ground, a phenomenon in which the pH value automatically shifts to the neutral direction occurs in the entire ground to be injected. Pollution can be prevented. In addition, since the injection material is homogeneously injected into the ground, magnesium hydroxide is suspended in the acidic silica sol at the tip of the injection solution, and the penetration distance becomes wide to promote gelation. However, the entire injection region can be securely consolidated. In addition, dilution and dispersion due to groundwater is unlikely to occur at the tip of the injection, and can be solidified without departing from the injection target area, and the ground to be injected is maintained in a substantially neutral area. It is also excellent in terms of conservation.

As a result, the following effects can be obtained in the present invention.
(1) The injection material can penetrate into the ground extensively without separating the magnesium hydroxide in the vicinity of the injection port, and the entire injection material can be moved in the neutral direction.
(2) The neutralization of excess acid in the acidic silica sol is carried out slowly, and the gel is also neutralized, so that a predetermined solidified body corresponding to a predetermined injection amount is formed without adjusting the gelation time. Is done.
(3) Since the tip of the injection material during injection contains an alkali agent, gelation occurs even during injection, and the injection region at the tip extends over the injection region, so that the injection material at the tip becomes groundwater. It can gel in the ground without thinning.
(4) Since there is no generation of gas due to the reaction with the acid, the permeability is excellent and a uniform consolidated body is formed.

  In the present invention, the liquid A and the liquid B may be combined at the tip using a double pipe and injected into the ground, or may be mixed before being sent to the injection pipe. . Further, they may be mixed in a mixer and injected into the ground.

  In the present invention, the combined ratio of the liquid A and the liquid B that retains the excess of acid is the electrochemical neutralization point at which the combined liquid becomes unstable and the gelation time is shortened, that is, around pH 8.5. In other words, the merging ratio is preferably such that the non-alkaline region on the acidic side from around pH 7 is always maintained. In the present invention, since the magnesium hydroxide is mixed in the water glass of the B liquid, the pH value of the gelled product may shift to the alkali side. If present, it is possible to form a homogeneous injection material without precipitating massive silica.

  In the present invention, the acidic liquid (acid reactive agent) is an acid such as an inorganic acid (sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, etc.) or an organic acid (formic acid, acetic acid, etc.), an acidic salt (monocalcium phosphate, phosphoric acid). Monosodium, sodium hydrogen sulfate, aluminum sulfate, aluminum chloride, etc.).

Further, since magnesium hydroxide (Mg (OH) ₂ ) in the present invention does not gel the water glass even when mixed with water glass in a large amount, the reaction is activated only after mixing with the liquid A. Ideal for invention.

Further, as the water glass in the present invention, the molar ratio _{(SiO 2 / Na 2 O)} : 1.5~5.0 liquid water glass, anhydrous water glass, hydration glass, any including crystal water glass A mixture of a metal salt of silicic acid and silicic acid in a molar ratio is used.
It should be noted that the above is an example, and the present invention is not limited to these examples.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Experiment 1>
Using the combinations of combinations of liquid A and liquid B shown in Table 1 below, the injection materials of Comparative Examples 1 to 5 and Example 1 were prepared, and the pH of the liquid mixture immediately after the mixing and 2 days after the mixing The pH of the supernatant was measured. Moreover, the presence or absence of precipitation of magnesium hydroxide was evaluated. The evaluation results are shown in Table 2 below. The kneaded silica concentration was about 5% or 6%, and the total amount was 400 ml.

(Comparative Example 1)
As the liquid A, water glass previously mixed with magnesium hydroxide was used, and as the liquid B, an acidic aqueous solution was used. In the acidic silica sol aqueous solution obtained by mixing these liquid A and liquid B, magnesium hydroxide was precipitated.

(Comparative Example 2)
As the liquid A, water glass was used, and as the liquid B, a solution prepared by mixing an acidic aqueous solution and magnesium hydroxide in advance was used. In the acidic silica sol aqueous solution obtained by mixing these A liquid and B liquid, precipitation of magnesium hydroxide occurred.

(Comparative Example 3)
An acidic silica sol obtained by mixing water glass and an acidic aqueous solution in advance was used as the A liquid, and magnesium hydroxide was used as the B liquid. In the acidic silica sol aqueous solution obtained by mixing these A liquid and B liquid, precipitation of magnesium hydroxide occurred.

(Comparative Example 4)
As liquid A, an acidic silica sol obtained by previously mixing water glass and an acidic aqueous solution was used, and as liquid B, a liquid mixture obtained by previously mixing water glass and calcium carbonate was used. In the acidic silica sol aqueous solution obtained by mixing these liquid A and liquid B, bubbles were generated and suspended.

(Comparative Example 5)
An acidic silica sol obtained by mixing water glass and an acidic aqueous solution in advance was used as the A liquid, and water glass was used as the B liquid. In the acidic silica sol aqueous solution obtained by mixing these liquid A and liquid B, no precipitation or the like occurred.

(Example)
As the liquid A, an acidic silica sol obtained by previously mixing water glass and an acidic aqueous solution was used, and as the liquid B, a mixed liquid obtained by previously mixing water glass and magnesium hydroxide was used. In the acidic silica sol aqueous solution obtained by mixing these liquid A and liquid B, magnesium hydroxide did not precipitate and became a floating state, the liquid was transparent or suspended, and no bubbles were generated. .

＊１）水ガラス：３号水ガラス，比重１．４１，シリカ濃度２９％
＊２）酸性水溶液：７５％硫酸，比重１．６７４
＊３）水酸化マグネシウム：比重２．４
＊４）炭酸カルシウム：比重２．７

* 1) Water glass: No. 3 water glass, specific gravity 1.41, silica concentration 29%
* 2) Acidic aqueous solution: 75% sulfuric acid, specific gravity 1.664
* 3) Magnesium hydroxide: specific gravity 2.4
* 4) Calcium carbonate: specific gravity 2.7

＊５）ゲルタイムが１日以上の配合は、いずれも１日以後にはゲル化した。

* 5) All formulations with a gel time of 1 day or longer gelled after 1 day.

<Experiment 2>
Next, in order to confirm the difference in pH and consolidation strength between the injection material of the present invention and the injection material of the comparative example, according to the following conditions, Comparative Example 1-1, Comparative Example 2-1 and Comparison in Table 1 above Using the injection materials of Example 3-1, Comparative Example 4-1, and Example 1-1, a sand gel specimen was prepared by a penetration method using Toyoura sand (relative density Dr = 60%), and uniaxial compressive strength was obtained. Was measured.

(Experimental device)
As an advance preparation, sample sand (Toyoura sand) is dropped from the upper part of the acrylic mold 10 having a length of 1000 mm and an inner diameter of about 50 mm and filled (relative density Dr = 60%) using the apparatus shown in FIG. Prior to injection of the material, it was saturated with degassed water.

  Next, the liquid A and the liquid B were put in the tanks 1 and 2, respectively, and were put into the water tank 4 by the pump 3. The input amount at this time was controlled by the flow meter 5. The chemical solution introduced into the mixing tank 4 was stirred by the stirrer 6, pushed out by the compressor 7, and permeated into the sample sand in the acrylic mold 10. The mixed chemicals are injected at a constant pressure of 0.03 MPa from the lower part of the acrylic mold 10, and the chemicals that have passed through the sample sand are the detection cocks 11 to 14 arranged at four equal intervals in the longitudinal direction of the acrylic mold 10 and It was discharged from the upper part of the acrylic mold 10 and collected in a graduated cylinder (not shown).

After saturated water overflowed in the acrylic mold 10 first, the chemical liquid overflowed. The gap in the acrylic mold 10 is about 750 cm ³ . The overflow liquid after the overflow corresponding to the gap amount ended gradually decreased from neutral to acidic.

  During the penetration, the chemical solutions were collected from the detection cocks 11 to 14, respectively, and the pH (20 ° C.) of the collected chemical solutions was measured. Further, the pH of this chemical solution was measured again after 1 day from collection, and the change in pH is shown in Table 3 below.

  Furthermore, after the sand gel (penetration consolidated sand gel) specimen prepared after infiltration was left to stand for 4 weeks, the specimen was cut, and the uniaxial compressive strength and the pH of the specimen were measured for every infiltration distance of 25 cm. Evaluated the relationship. Specifically, the acrylic mold was cut at intervals of 25 cm after 4 weeks from the injection of the chemical solution, and the permeation solidified body in the acrylic mold was scraped to collect 50 g of samples, each of 125 g of distilled water (mass ratio 2.5). The mixture was stirred. About the obtained aqueous solution, pH was measured after leaving still for 2 hours. The results are shown in the following Table 4 and FIGS. 2 and 3 together with the measurement results of the uniaxial compressive strength of the specimen.

  From the above results, in Comparative Examples 1-1 and 3-1, magnesium hydroxide was separated from the injection solution, clogged near the injection port, and homogeneous infiltration in the ground was insufficient. Therefore, the neutral value was shown in the vicinity of the injection port, but it became acidic as it moved away from the injection port. Moreover, in Comparative Example 2-1, magnesium hydroxide was neutralized with an acid and did not function as magnesium hydroxide, and the injection solution exhibited a low acid value. Furthermore, in Comparative Example 4-1, since carbon dioxide gas was generated vigorously and bubbles and precipitates were formed, uniform permeation was not possible. Moreover, since a porous solid body was formed by carbon dioxide gas, the strength was low.

  That is, it is necessary to use silica sol that exhibits an acidic value for the purpose of obtaining a wide range and homogeneous solidified body of the present invention. It was found that it cannot be applied to various purposes. Moreover, in this invention, it turned out that a solidified body is formed widely and uniformly in a substantially neutral region without separating magnesium hydroxide in the injection solution, and the strength of the solidified body is almost uniform. Further, no gas such as carbon dioxide gas was generated, and a uniform cloudy silica solution was retained.

  From the results in the above table, it can be seen that the injection material of the present invention itself exhibits neutrality from acidity to neutrality in the initial stage, but the final solidified body exhibits neutral pH over time. . Thereby, according to this invention, it was confirmed that the problem of isolation | separation of the hardly soluble alkali agent in acidic silica sol can be solved.

1, 2 Tank 3 Pump 4 Mixing tank 5 Flow meter 6 Stirrer 7 Compressor 10 Acrylic mold 11-14 Detection cock

Claims (2)

  A ground-injecting material that exhibits acidity to neutrality, wherein acidic silica sol obtained by mixing water glass and acidic liquid is liquid A, and a liquid mixture obtained by mixing water glass and magnesium hydroxide is liquid B As for the ground injection material characterized by mixing A liquid and B liquid.   An acidic silica sol obtained by mixing water glass and acidic liquid is designated as A liquid, and a liquid mixture obtained by mixing water glass and magnesium hydroxide is designated as B liquid, and obtained by mixing A liquid and B liquid. A ground injection method characterized by injecting a ground injection material that is acidic to neutral into the ground.

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