JPH0468356B2 - - Google Patents

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 grout has 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 has been a problem 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 has neutral solids and is suitable for underground water.
Although it is an injection material with excellent properties without any fluctuation in pH, it has the drawbacks of low strength and extremely short gelation time. In other words, normally, the concentration of SiO ₂ in the injection liquid for water glass grout needs to be 10 parts by weight or more from the viewpoint of strength (the unconfined compressive strength of consolidated sand is 1 Kg/cm ² or more). If the concentration of ₂ is 10% by weight or more, the gelation time will be within 1 minute in the neutral region (PH 4 to 8), and usually several seconds. It has been empirically determined that the gel time suitable for good permeability and solidification without dispersing in the ground is 30 to 120 minutes, but if the gel time is 30 to 120 minutes near the neutral region ~
If you want to obtain about 120 minutes, the concentration of SiO ₂ must be 5% by weight or less, and at this concentration, the consolidated sand strength will not reach 0.5 Kg/cm ² , making it practically unusable for the injection method. Can not. In addition, water glass grout in the neutral range is obtained by adding water glass to an acidic solution and neutralizing the alkali in the water glass to obtain the injection solution. Many neutralized products, such as Na ions and acid radicals, remain, but from the viewpoint of water quality conservation, these
If we could establish an injection method that leaves no Na ions or acid roots behind, nothing would be better than this. Also, there is a known method of using acidic water glass liquid, which is obtained by adding water glass to an acidic liquid, in the ground injection method. It takes advantage of the phenomenon of gelation through silicic acid, and contains 10wt% _SiO2 .
In order to obtain a formulation with a long gelation time of 30 minutes or more, it is necessary to adjust the pH to an acidic region around 3 before injection. An object of the present invention is to provide a further developed technique to solve the above problems. In order to achieve the aforementioned object, according to the present invention:
An injection solution obtained by adding the additives shown in the following groups 1 and 2 to a colloidal solution of silicic acid with a pH of 9 to 10 obtained by passing water glass through an ion exchange resin to remove most of the alkali content in the water glass. is injected into the ground, and the amount of the additives shown in the second group is 2% by weight or less of the total mixed liquid. Group: alkali metal salts. Group 2: polyvalent metal salts. Hereinafter, the present invention will be specifically explained in detail. The present inventor is a colloidal solution of silicic acid (silica sol)
If a polyvalent metal electrolyte substance (a substance that dissociates polyvalent metal ions) is mixed with the liquid, white turbidity or partial precipitation will occur, but if the mixed amount is within % of the total mixed liquid, fluidity will be improved by mixing. A solution that retains the They found this and completed the present invention. In other words, by using a combination of a polyvalent metal salt and an alkali metal salt within a double weight percentage of the total blended solution in a blended solution based on a colloidal solution of silicic acid, it is possible to easily control the gelation time from several hours to several seconds. It becomes possible. A homogeneous gel is produced. Since the amount of additives added is only a small amount, it does not affect the quality of groundwater. Further details of the present invention are as follows. The silicate colloid in the present invention is derived from water glass.
Na ions are removed or reduced, for example, by passing the water glass through an ion exchange resin to remove the Na ions in the water glass, or by neutralizing the water glass with sulfuric acid and then removing the Na ions from the sulfate ions. It can be obtained by For example, water glass is passed through an ion exchange resin such as a zeolite cation exchanger or an ammonium ion exchanger, and the resulting silica sol is heated at 80℃ to 90℃.
It is obtained by adding the silica sol to water glass at a temperature of .degree. C. and passing it through the ion exchange resin again for ion exchange, yielding a relatively pure (dilute) 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. A method is used in which the silica is heated under a suitable alkali, and activated silica sol is further added thereto for stabilization. In the silicic acid colloid solution in the present invention, almost all Na ions have been separated and removed, and the molar ratio is 10 or more. Usually, it is desirable that the content of SiO ₂ is adjusted to 10 to 60% (by weight), the molar ratio (SiO ₂ /Na ₂ O) is adjusted to 50 or more, and the PH value is adjusted to 8 to 10. When the molar ratio is less than 10, the silicate colloid dissolves and becomes an aqueous solution of silicate. In this case, the particle size of the silicic acid colloid solution is mainly about 6 to 50 mμ. When the particle size of the silicic acid colloid is 50 mμ or more, it tends to precipitate. The silicic acid colloid solution prepared in this way is stable semi-permanently, and when used as an injection solution, there is no risk of gelation during transport from the factory to the site and during injection operations. Even if this colloidal solution of silicic acid is directly injected into the ground, it will not gel itself within a practical period of time, so no practical consolidation effect will be obtained. The present inventor believes that the material for ground injection must be semi-permanently stable until just before mixing the injection liquid, but when the injection liquid is injected, some solids may be suspended. We focused on the fact that it is desirable to improve uneven ground effectively. This is because the injection ground usually has a complex structure of soil with different pores, so it is most desirable to fill the coarse parts with solid content and fill the narrow parts with the solution-like injection material. In this way, the permeable, more solution-like injectable material can penetrate between the fine soil particles without becoming deviated. 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 are 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 salt, and as a result, the following points were found. (1) When a trace amount of a polyvalent metal salt is added to a colloidal solution of silicic acid, cloudiness or white precipitation occurs instantaneously.The degree of this becomes more noticeable as the amount of the salt added increases, but the whole solution becomes homogeneous. If this is mixed, the gelation time will be unclear because the mixture will continue to flow while containing solid content. (2) If the concentration of the electrolyte substance is less than 2% (by weight), white turbidity, white precipitate, or partial gel will occur;
It can be injected as is without losing its fluidity, and when it is injected, the solution and solids will separate appropriately in the soil, solids will fill the coarse parts of the soil, and the solution will penetrate into the narrow parts. solid content
Excellent effects are obtained because gelation occurs as a whole centering on SiO ₂ . (3) When the concentration of the electrolyte substance exceeds 2%, white precipitate immediately becomes noticeable, fluidity cannot be obtained even by mixing, and even when injected, veins become the main component and solidification due to the solution content occurs. Almost no effect can be obtained. 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. Therefore, even if it is injected, the solution other than the solid content will not solidify, the strength will be extremely reduced, and the injection effect will not be obtained. On the other hand, as a result of various studies, the present inventors have found that the following problems occur in the reactions between colloidal solutions of silicic acid and various salts. The reaction between silicic acid colloid and acid takes the shortest time in the vicinity of neutral to weak acidity, 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 an acid, but there is a limit to this. When polyvalent metal salt is mixed with silicic acid colloid in an amount of less than 2% by weight of the total mixed solution, white turbidity or white precipitate will immediately occur, and fluidity can be obtained by mixing this, but overall gelation will occur. It is difficult to effectively control the gelation time because the gelation time is not clear and the obvious 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 Almost no penetration solidification effect can be obtained inside. Table 1 shows the characteristics of the silicic acid colloidal liquid used in the experiment, and Tables 2 and 3 show the experiments. (Composition is weight %).

[Table] From Table 2, it can be seen that even if a silicic acid colloid and a polyvalent metal electrolyte are mixed, it is difficult to achieve homogeneous gelation and control the gelation time. From Table 3, it can be seen that when a silicic acid colloid and an alkali metal salt are mixed, a homogeneous gel is formed and it is possible to control a long gelation time, but it is difficult to control a short gelation time. Furthermore, Table 3 shows that when less than 2% by weight of alkali metal salt and alkaline earth metal electrolytes are added to silicic acid colloid, a homogeneous gel is formed although it becomes cloudy, and the gelation time can be controlled from around 100 minutes to several seconds. I understand what happened.

【table】

[Table] From the above experimental results, it is essential that the content of the polyvalent metal salt in the present invention is 0.005 to 2% by weight of the total liquid mixture. In the present invention, polyvalent metal salts include chlorides, sulfates, phosphates, nitrates of alkaline earth metals, aluminum, transition metals, rare earth metals, etc., as well as their hydroxides, oxides, and cement (aluminum hydroxide). A substance that dissociates ions of polyvalent metals (including polyvalent metals). It is thought that these act on the silicate colloid to make it unstable or to form a polyvalent metal silicate. 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. , silicates, phosphates,
Examples include inorganic salts such as hydrogen phosphate, pyrophosphate, dichromate, permanganate, and any organic salts. The grout used in the present invention has the property that gelation is promoted in the ground and is difficult to deviate from due to the presence of solid content due to white turbidity and white precipitation. If so, this grout can be used as a secondary grout and is injected after the primary 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 particularly suitable. Example 1 A water permeability test was conducted by injecting 3,000 ml of the mixture No. 19 in Table 3 into the ground in Tokyo, where cells and sand intersect in a complex manner, and the soil was excavated to determine the consolidation status and consolidation. The uniaxial compressive strength of the body was investigated. The water permeability test results showed that k = 3.5 x 10 ^-3 cm/sec before injection, but k = 4.5 x 10 ^-6 cm/sec after injection, and a sufficient water stopping effect was obtained. Furthermore, the results of the excavation survey revealed that a solid substance of about 10m3 in diameter was approximately cylindrical and had a diameter of ^{1.2 to 1.3m} centered on the injection port. When the excavated cross section was examined, 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 a uniaxial compressive strength test on the compact, we were able to obtain a strength of 6.8 Kg/cm ² in the thin soil area and 7.2 Kg/cm ² in the coarse soil area. As mentioned above, the present invention focused on the fact that when a silicic acid colloid solution and a polyvalent metal salt are mixed, it immediately becomes cloudy, and discovered the relationship between fluidity in grouting methods based on the amount of polyvalent metal salt mixed, and further developed an acid solution. A non-polluting grout that can create a homogeneous gel using a combination of alkali metal salts and alkali metal salts, and allows the gelation time to be controlled arbitrarily, and because only a small amount of electrolyte is added, there is almost no change in the quality of groundwater. This made it possible.

Claims (1)

[Claims] 1. PH9 to 10 obtained by passing water glass through an ion exchange resin to remove most of the alkaline content in the water glass.
It is characterized by injecting into the ground an injection liquid obtained by adding additives shown in the following groups 1 and 2 to the silicic acid colloid liquid of A ground injection method characterized in that the amount is within the range of 0.005 to 2% by weight. Group 1: Alkali metal salts Group 2: Polyvalent metal salts.