JPS59152985A - Impregnation method for ground - Google Patents

Abstract

PURPOSE:To prepare pollution-free grout having uniform gel, capable of controlling gel time, by adding an alkali metal salt, an acid, and a specific small amount of an electrolyte substance of polyvalent metal to a colloidal solution of silicic acid to give a solution, injecting the solution to the ground. CONSTITUTION:(A) A colloidal solution of silicic acid having preferably 8-10 pH, 10-60wt% SiO2 content, and a molar ratio of SiO2/Na2O of >=50 is blended with (B) an alkali metal salt and/or an acid and <=2wt% electrolyte subtance of polyvalent metal, to give an impregnation solution. This impregnation solution is injected to the ground, and it is solidified.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground injection method using a colloidal solution of silicic acid.

Traditionally, water glass clouds have been used for ground injection. Water glass grout is a liquid alkali metal salt of silicic acid, and is used to solidify the ground by adding salt or acid to precipitate a silicic acid gel.

However, since the alkali metal salt of silicic acid exhibits high alkalinity and gelation occurs in the alkaline region, there is a problem in that groundwater remains alkaline for a long period of time.

To solve this problem, a ground injection method has been developed in which water glass is added to an acidic solution and the alkali in the water glass is removed, and the alkali is combined with the acidic silicic acid solution to form a gel in a neutral region. There is.

This grout is a grouting material with extremely excellent properties, as the solids are neutral and the pH of groundwater does not fluctuate.
It had the disadvantages of low strength and very short gelation time.

That is, usually Si in the injection liquid in water glass grout
From the viewpoint of strength, the concentration of n, , should be 10% by weight or more (the unconfined compressive strength of consolidated sand is l Kp / cy1 or more).
However, when the concentration of 5102 is 10% by weight or more, the gelation time is within 1 minute near the neutral region (pH 4 to 8).
It usually takes a few seconds. The gel time is 30 to 120, which has good permeability and is suitable for solidifying without dispersing in the ground.
7) However, if the gelation time is to be near the neutral range and an analysis degree of 30 to 120 is to be obtained, the concentration of 5102 must be less than 5% by weight. At this concentration, the consolidated sand strength is 0.5 i(q/c
It does not reach rI, and the injection method cannot be used practically.

Well, the water glass grout in the neutral range is made by adding water glass to an acidic solution to neutralize the alkali in the water glass to obtain the injection liquid, so there are a lot of things in the injection liquid. However, many neutralization products generated by neutralization, such as Na ions and acid radicals, remain, but these Na
Nothing would be better than establishing an injection method that leaves no residual ions or acid roots.

Another known method is to add water glass to an acidic solution and use it in the ground injection method. It utilizes the phenomenon of gelation through silicic acid, and in order to obtain a formulation with a gelation time of 30 minutes or more and a Sl○2 content of IQ wt% or more, the pH must be
It is necessary to adjust and inject to the acidic/singing range around 3.

The purpose of the present invention is to provide a further developed technique for solving the above problems.

In order to achieve the above object, the present invention is characterized by injecting into the ground an injection liquid obtained by adding additives shown in the following groups 1 and 2 to a silicic acid colloid liquid, respectively, It is characterized in that the amount of the additives shown in the second group is 2% by weight or less of the total blended liquid.

Group 1: One or more selected from the group of alkali metal salts and acids.

Group 2: Polyvalent metal electrolyte substances.

Hereinafter, the present invention will be specifically explained in detail.

The present inventor discovered that when a polyvalent metal electrolyte substance (a substance that dissociates polyvalent metal ions) is mixed with a colloidal solution of silicic acid (silica sol), white turbidity or partial precipitation occurs, but the amount of the mixture is about 20% of the total mixed solution. We focused on the fact that if it is within the weight percent, a solution that maintains fluidity can be obtained by mixing, and when this is injected into the ground, a strong solidified body can be obtained, and an extremely excellent injection effect can be obtained, especially in heterogeneous ground. As a result of further research, the following phenomena were discovered and the present invention was completed.

That is, by adding one or more types of acids or alkali metal salts to a polyvalent metal electrolyte substance within a double weight percentage of the total blended solution to a blended solution containing a colloidal solution of silicic acid as a main ingredient, 6) from several hours. It becomes possible to easily control the gelation time up to several seconds.

■ A homogeneous gel can be produced.

■ Additives only need to be added in small amounts, so they do not affect the quality of groundwater.

Further details of the present invention are as follows.

The silicate colloid in the present invention is water glass with Na ions removed or reduced. For example, the Na ions in the water glass are removed by passing the water glass through an ion exchange resin, or the water glass is soaked with sulfuric acid. It is obtained by summing and then removing Na ions and sulfate ions.

For example, water glass is passed through an ion exchange resin such as a zeolite-based cation exchanger or an ammonium-based ion exchanger, and the generated silica sol is further added to the water glass at a temperature of 80°C to 90°C, and then passed through the ion exchange resin again. The silica sol is obtained by performing ion exchange using a thin silica sol. In order to obtain even pure silica sol, the dilute silica sol mentioned above is adjusted to be slightly alkaline, and the above-mentioned silica sol is further added to it while evaporating, thereby simultaneously stabilizing and concentrating it. Alternatively, the activated silica sol after ion exchange can be used. In the silicic acid colloid solution of the present invention, most of the Na ions have been separated and removed, and the molar ratio is 10. That's all.

Usually, it is desirable that the content of SiO□ is 10 to 60% (by weight), the molar ratio (SiOq/Na, O) is 50 or more, and the pH value is adjusted to 8 to 10.

When the molar ratio falls below joB, the silicate colloid dissolves and becomes an aqueous solution of silicate. In this case, the grain size of the silicic acid colloid is mainly about 6 to 50 mμ. When the grain size of the silicic acid colloid is 50 mμ or more, it tends to precipitate.

The silicic acid colloid prepared in this way is stable semi-permanently, and when used as an injection solution, there is no need to worry about gelation during transport from the T field to the site and during injection operations. Even if this colloidal solution of silica is injected directly into the ground, it will not gel itself within a practical period of time, so no practical consolidation effect will be obtained.

The inventor believes that the material for ground injection must be semi-permanently stable immediately before mixing the injection liquid.
We focused on the fact that when injecting liquid, it is preferable for some solids to be suspended in order to improve the uneven ground.

This is because the injection ground usually has a complex interposition of different voids, so it is most desirable to fill the rough areas with solid content and fill the narrow areas with a solution-like injection material.

In this way, the injectable solution in the form of a highly permeable solution can penetrate between the deviating heavy and thin soil particles.

For this purpose, it is desirable that the solution injected material and the solid injected material be easily separated, and that ultimately, after gelation, they can be consolidated as a whole.

For this purpose, the present inventor conducted experiments focusing on the reaction between a silicate colloid solution and a polyvalent metal electrolyte material, and as a result, the following points were found.

(],) When a trace amount of a polyvalent metal electrolyte is added to a colloidal solution of silicic acid, cloudiness or scuttling occurs instantaneously, and the degree of this becomes more severe as the amount of the salt added increases, but the whole solution remains homogeneous. If this is mixed without any interruption, the gelation time becomes unclear because the solid content remains fluid forever.

(2) If the concentration of the electrolyte substance is within 2% (by weight), cloudiness, scuttling, or partial gelation will occur, but the fluidity will not be lost and it can be injected, and if it is injected, it will spread all over the earth. The solution and solid content are appropriately separated, the solid content fills the used part of the soil, the solution permeates into the narrow part, and gelation occurs as a whole centering on the solid content of 8102, resulting in excellent effects. sell.

(3) When the concentration of the electrolyte substance exceeds 2%, scuttling immediately becomes severe, fluidity cannot be obtained even by mixing, and even if it is injected, veins are mainly formed, and the solidification effect due to the solution content is I don't get much.

When the concentration of the silicic acid colloid becomes dilute, even if the concentration of the electrolyte substance exceeds 2% by weight, it remains fluid, but most of the silicic acid content reacts with the electrolyte and becomes a solid content consisting of silicates of polyvalent metals. Because of this, even if it is injected, the solution other than the solid content will not solidify, the strength will be extremely reduced, and no injection effect will be obtained.

On the other hand, as a result of various studies, the present inventor found that the following problems exist in the reaction between a colloidal solution of silicic acid and an acid or various salts.

(2) The reaction between silicic acid colloid and acid is shortest at neutral to weakly acidic conditions, but it is difficult to shorten the gelation time to within a few hours.

■ Mixing a silicic acid colloid with an alkali metal salt can shorten the gelation time compared to the case of an acid, but there is a limit to this.

■ When polyvalent metal electrolyte is mixed with silicic acid colloid in an amount of less than 2% by weight of the total mixed solution, white turbidity or scuttling occurs immediately, and fluidity can be obtained by mixing this, but overall gelation is not achieved. It is difficult to effectively control the gelation time because the gelation time is not clear and the apparent gelation time is unclear.

If the content of polyvalent metal salt is 2% by weight or more of the total blending amount, the amount of solid content will be too large and fluidity will not be obtained.If the concentration of silicate colloid is low, fluidity will be obtained, but the soil There is almost no penetration solidification effect inside.

Table 1 shows the characteristics of the silicic acid colloid liquid used in the experiment.
Experimental results are shown in Tables 2, 3, 4, and 5.

(Composition is weight %).

- It turned out that it is possible.

From the above experimental results, the content of the polyvalent metal electrolyte in the present invention is 2% by weight or less, preferably 0.00% by weight of the total mixed solution.
It is essential that the content be 5 to 2% by weight.

The polyvalent metal electrolyte material in the present invention refers to chlorides of alkali metals, aluminum, transition metals, rare earth metals, etc.
It refers to substances that dissociate ions of polyvalent metals, such as sulfates, phosphates, nitrates, and their hydroxides, oxides, and cement (including aluminum hydroxide). It is thought that these act on the silicate colloid to make it unstable or to form a polyvalent metal silicate.

Acids used in the present invention include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; organic acids such as formic acid, acetic acid, and succinic acid; aluminum chloride, aluminum sulfate, monocalcium phosphate, and monophosphoric acid.
Sodium, sodium hydrogen sulfate, aluminum sulfate,
Acidic salts such as aluminum chloride; Nisel; amides; aldehydes such as glyoxal; Substances that generate acid groups by hydrolysis in the presence of alkali; Substances whose aqueous solution exhibits acidity such as carbon dioxide gas, etc. It is not limited to these. However, strong acids are the most economical.

In addition, examples of the alkali metal salts in the present invention include alkali metal chlorides, chlorates, sulfates, aluminates, carbonates, bicarbonates, nitrates, bisulfates, bisulfites, and silifluorides. Examples include inorganic salts such as silicates, phosphates, hydrogen phosphates, pyrophosphates, dichromates, permanganates, and any organic salts.

The grout used in the present invention has properties that promote gelation in the ground and are difficult to deviate from due to the presence of solids due to cloudiness and scuttling. If so, this grout can be used as a secondary grout, and is injected after the secondary grout has previously been injected into the injection area.

As the above-mentioned primary injection material, a suspension containing an electrolyte substance that dissociates calcium ions, such as cement or lime, is preferred.

Example 1 Table 4 was found in the ground in the Tokyo area where fine sand and green sand are interposed in a complex manner.
A water permeability test was carried out by injecting 3000 ml of a mixed Na9 solution, and excavation was conducted to examine the consolidation status and the unconfined compressive strength of the consolidated body. According to the water permeability test results, k = 3.
After injection, k = 4.5 x]0-' cm/θec, which was 5 x 10-3 cm/sec, and a sufficient water stopping effect was obtained.

Additionally, the results of the excavation survey show that the diameter around the injection port is 1.2 mm.
A roughly cylindrical solid of ~1.3 m and approximately 10 m3 was obtained. When examining the excavated cross section, it was found that the coarse sand part was filled with white granular solids, and the fine sand part was solidified by the mixed liquid in the solution part. In addition, when we conducted an unconfined compressive strength test of the solidified material, we found that it was 6.
．． We were able to obtain a strength of 8Kg/cd, and 7.2Kg/cd in the coarse soil area.

For comparison, the formulation Nα36 in Table 4 was injected using a double tube.

That is, a 20% SiO
A mixed solution containing 5% of CaCl2 and 0.2% of 97% sulfuric acid as the B solution is sent from the inner pipe line, and is mixed at a ratio of 1:1 at the tip of the injection pipe.
(volume ratio) and injected. When we excavated the area after the injection, we found that massive precipitates were spread over a wide area in the form of veins, and although some consolidation was observed, no overall consolidation was observed, and no obvious improvement in the hydraulic conductivity was obtained. Ta.

Example 2 - Table-3 mixture Nl12 and Table-4 on sandy ground in Tokyo area
A comparative test was conducted by injecting 1.000 t of grout with a composition Nα16 into each grout, and measuring the quality of groundwater in an inspection hole set 5 m apart before and after the injection.

The results are shown in Table-6.

The numerical value indicates the number of milligrams in the groundwater volatilization sample 12.

From Table 6, the present invention not only contains less salt in the silicic acid colloid, but also requires only a small amount of additives, so it can be considered that there is virtually no change in the quality of groundwater. As mentioned above, the present invention focused on the fact that when a silicic acid colloidal solution and a polyvalent metal salt are mixed, it immediately becomes cloudy, and discovered the relationship between fluidity in grouting methods from the amount of polyvalent metal salt mixed, and further By using acids and alkali metal salts in combination to create a homogeneous gel, the gelation time can be controlled arbitrarily, and only a small amount of electrolyte is added, so there is almost no change in the quality of groundwater. This makes it possible to use non-polluting grout.

Claims (1)

[Claims] It is characterized by injecting into the ground an injection liquid obtained by adding additives shown in the following groups 1 and 2 to a colloidal liquid of silicic acid. A ground injection method characterized by the addition amount being 2% by weight or less of the total mixed liquid. Group 1: One or more selected from the group of alkali metal salts and acids. Group 2: Polyvalent metal electrolyte materials.