JPS5844102B2 - Soil stabilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing soil quality using a silicate grout, and more specifically, the present invention relates to a method for stabilizing soil quality using a silicate grout. This invention relates to a method for stabilizing soil quality by injecting a sodium silicate aqueous solution into soil and allowing it to gel in the soil.

Conventionally, grouting methods have been known in which various chemical solutions are injected into soil and gelled in the soil in order to strengthen soft ground or stop leaking ground.

Various types of grout have been proposed for use in this method, but among them, sodium silicate aqueous solution (
In recent years, so-called silicate grouts made of a combination of Na2Si03aq) and a gelling agent have been widely put into practical use.

Sodium silicate aqueous solution exhibits strong alkalinity and easily gels when neutralized by adding an acid or a salt thereof.

Here, to explain the gelation mechanism of an aqueous sodium silicate solution by an acid or its salt using a diagram, FIG. 1 is a graph showing the relationship between the gel time of a grout made of a combination of an aqueous sodium silicate solution and phosphoric acid.

As shown in Figure 1, as the pH of the grout is lowered by increasing the amount of phosphoric acid added to the sodium silicate aqueous solution, the grout gels in a shorter time, and when the pH is around 8 to 9, it gels almost instantaneously. However, when the amount of phosphoric acid added is further increased to lower the value of -, the gel time becomes longer again, and the relationship between the pair of gel times of this grout becomes a curve resembling a parabolic line.

The gelling mechanism of grout using another acid or its salt as a gelling agent instead of phosphoric acid is the same as that of phosphoric acid, but the central part of the curve, i.e., p, which brings the grout into an instantaneous gelling state,
The H range (hereinafter referred to as instantaneous field pH) is slightly different.

As is clear from this relationship between u and gel time, grout made by combining an aqueous sodium silicate solution with an acid or its salt can be used in an area on the alkaline side (hereinafter referred to as the alkaline area) and an area on the acid side (hereinafter referred to as the neutral area) than the critical pH. Although it is possible to adjust the gel time in both the acidic and acidic regions, conventional soil stabilization work mostly focuses on the alkaline region (p) from the economic point of view of requiring less gelling agent. (approximately 10.5 to 11) grout was injected into the soil and allowed to gel.

However, if silicate grout is allowed to gel in an alkaline region in this way, it may make the soil alkaline, or the grout may flow into groundwater, well water, etc., contaminating the water with alkali and causing pollution problems. Recently, there has been a demand for silicate grouts to be gelled in a neutral to acidic range.

Therefore, as a method to meet this demand, a method has been proposed in which grout using phosphoric acid or a mixed acid of phosphoric acid and sulfuric acid as a gelling agent is gelled in the soil in a neutral or acidic region (Incorporated Association, Civil Engineering Edited by an academic society, 30th Annual Academic Conference Lecture Summary Part 3, pp. 446-447, 1932
Published October 0).

However, in order to gel a silicate grout in a neutral or acidic region, a considerably larger amount of gelling agent is required than in the case of gelling it in an alkaline region.

For example, when grout with a gel time of 1 to 5 minutes, which is most commonly used in actual construction, is gelled in a neutral or acidic region using phosphoric acid as a gelling agent, the gelling time is several times that of an alkaline region (usually 3 to 5 minutes). It requires the same amount of phosphoric acid as the main ingredient, sodium silicate (5 times).

Phosphoric acid is particularly expensive among gelling agents, so it is not only impractical to use such a large amount, but it is also difficult to handle large amounts of liquid strong acids such as phosphoric acid when preparing pharmaceutical solutions or other operations. There are dangers involved.

On the other hand, sulfuric acid is a powerful drug and its use is currently prohibited.

In view of this situation, the present inventors conducted various studies in an attempt to stabilize the soil by gelling a sodium silicate aqueous solution in the soil in a neutral or acidic region using agents that do not have such drawbacks. Alkali salts of hydrogen sulfate, such as potassium hydrogen and ammonium hydrogen sulfate, are solid acid salts that are easier to handle and less dangerous than phosphoric acid and other liquid strong acids, and are considerably cheaper than phosphoric acid. It has been found that gelling agents have various advantages over conventional gelling agents.

Therefore, we attempted to put into practical use a grout that combines Sodium sulfate with an aqueous solution of sodium silicate.

As shown in Figure 2, this grout gels in the alkaline to acidic range with a gel time depending on the amount of sodium hydrogen sulfate used, and maintains a uniform solution state until it gels in the alkaline range of about 8 or higher. I keep it, but
In a neutral or acidic region with a pH of about 7 or lower, as soon as an aqueous sodium silicate solution and sodium hydrogen sulfate are mixed, a fine gel is formed in the mixed solution and the grout becomes a gel-liquid mixture, which makes it difficult to inject the grout into the soil. When doing this, I often had trouble with the gel clogging the injection tube.

This phenomenon was similarly observed when an alkali hydrogen sulfate salt such as potassium hydrogen sulfate or ammonium hydrogen sulfate was used instead of sulfur hydrogen sulfate.

(However, very dilute sodium silicate aqueous solution, such as Na
2 This phenomenon is not observed when sodium hydrogen sulfate is added to a sodium silicate aqueous solution with a S103 concentration of 1% by weight or less to adjust the pH to a neutral or acidic range. Even if it is gelled, it cannot provide sufficient strength to the soil, making it unsuitable for use as grout.

) Based on the above, the present inventors conducted various studies in an attempt to overcome the above-mentioned drawbacks of grout that is a combination of sodium hydrogen sulfate salt and sodium silicate aqueous solution. It has been found that when a mixture containing an appropriate amount of a compound or hydroxide is added to an aqueous sodium silicate solution to make the solution neutral to acidic, a uniform solution state is maintained until gelation occurs.

As a result of further research, a mixture of the above-mentioned alkali hydrogen sulfate and the respective oxides or hydroxides of magnesium and zinc, and an appropriate amount of phosphoric acid or hydrogen phosphate was added to an aqueous sodium silicate solution. If the solution is kept in a neutral or acidic region, it not only maintains a homogeneous solution state until gelation, but also preferably only a mixture of an alkali hydrogen sulfate salt and the respective oxides or hydroxides of magnesium and zinc is used. The inventors have discovered that the strength of the treated soil can be made even stronger than the above-mentioned grout, and have come up with the invention described below.

That is, the present invention has the following features: (1) A mixture of (a) hydrogen alkaline salt and (b) each oxide or hydroxide of magnesium and zinc is blended into a sodium silicate aqueous solution to make the field neutral or acidic. A method of injecting grout into soil and gelling it in the soil to stabilize the soil quality; )' A method in which a mixture of phosphoric acid or hydrogen phosphate is mixed with a sodium silicate aqueous solution, the grout is made into a neutral or acidic region, and the grout is injected into the soil, allowing it to gel in the soil and stabilize the soil quality. be.

As the sodium silicate used in these two inventions, sodium silicate which has been conventionally used in silicate grouts can be used.

For example, JIS-1408 No. 1 to No. 3 sodium silicate can be used, and No. 3 sodium silicate is particularly preferably used.

Sodium silicate is diluted with water before construction to make an aqueous solution with an appropriate concentration suitable for construction, but the concentration of sodium silicate (Na 2 SiO 3 ) in grout in both inventions is usually 5 to 13.
% by weight.

Examples of alkaline hydrogen sulfate salts (hereinafter referred to as component (a)) used in both inventions include hydrogen sulfate, potassium hydrogen sulfate, and ammonium hydrogen sulfate. Preference is given to using ammonium.

Component (a) is used in both inventions to make the sodium silicate aqueous solution neutral to acidic and to gel the grout in the soil.

The respective oxides or hydroxides of magnesium and zinc (hereinafter referred to as component (b)) used in both inventions specifically refer to magnesium oxide, magnesium hydroxide, zinc oxide, and zinc hydroxide.

Component (b) is used in both inventions to maintain a uniform solution state until the grout in the neutral to acidic region gels.

Hydrogen phosphate used in the invention (11) (hereinafter referred to as (C)
Components) include disodium monohydrogen phosphate, dipotassium monohydrogen phosphate, diammonium monohydrogen phosphate,
monosodium dihydrogen phosphate, monopotassium dihydrogen phosphate,
Monoammonium dihydrogen phosphate may be mentioned, but sodium salt or ammonium salt is usually used.

In the invention of (11), component (C) is used to strengthen the stabilized soil strength, and is
The grout according to the invention (11) in which the component (C) is added can make the treated soil stronger than the grout according to the invention (1) in which the component (C) is not added.

The grout in the invention (i) is made by blending a mixture of components (a) and (b) with an aqueous sodium silicate solution.

The amount of component (a) to be used varies depending on the concentration of the sodium silicate aqueous solution used and the time period for gelling the grout in the soil.

For example, in normal construction, grout using a sodium silicate aqueous solution with a Na2 S J 03 concentration of about 10% by weight is gelled in a few minutes to more than ten minutes in a neutral to acidic region. About 7 to 1
It is used in a range of 0% by weight.

The amount of component (b) used varies slightly depending on the type used, but it is usually a small amount <10% by weight based on component (a).
The amount within this amount is sufficient to achieve the purpose.

Even if each component (b) is added individually to a sodium silicate aqueous solution,
Although it is not about gelation, when added to a sodium silicate aqueous solution in combination with component (a), it not only corrects the aforementioned drawbacks seen when component (a) is used alone, but also The amount of component (a) used can be reduced compared to when a sodium silicate aqueous solution is gelled using component (a) alone.

That is, when component (b) is used in combination with component (a), it also acts as a gelling agent.

Therefore, in this grout, (b
) component can also be used on a plate for its intended purpose to adjust the gel time of the grout.

The grout in the invention (1j) is (a), (b)
It is produced by blending a mixture of components (c) and (c) into an aqueous sodium silicate solution.

The same can be said about the amounts of component (a) and component (b) used and the role played by component (b) as in the case of the grout of the invention (i).

The amount of component (C) to be used varies depending on the type used, but it is not necessary to use a large amount, and an amount of about 20 to 25% by weight based on component (a) is usually sufficient.

In addition, other acids and salts such as boric acid, sodium tetraborate, sulfuric acid, ammonium sulfate, hydrochloric acid, ammonium chloride, sodium bicarbonate, and sulfur-IJium carbonate were tried in place of component (C), but soil Strength did not improve at all.

The construction method for soil stabilization is the same as the conventional method in both inventions, and before construction, a sodium silicate aqueous solution (a) is applied.

(b) a mixture of both components (or (a), (b),
(c) Aqueous solutions of the three-component mixture) are prepared separately, and both are mixed at the time of soil injection, and the mixture is injected into the soil using a pump.

In carrying out both inventions, the most common method for adjusting the gel time of grout is to increase or decrease the amount of (a) component in various ways;
It is also possible to adjust the amounts of the ingredients used by varying them.

Furthermore, it has been known that adding common salt, mirabilite, potassium sulfate, etc. to silicate grout makes it easier to adjust the gel time.

Therefore, in the present invention, it is also possible to use these as necessary.

These two methods of invention gel the grout in the neutral or acidic region of the soil, so unlike the conventional gelling method in the alkaline region, the soil does not become alkaline, and well water, groundwater, etc. There is no contamination.

(Grout with a gel time of 1 to 5 minutes, which is most often used in actual construction, has a pH of about 5°2 to 6.1, and gels at a pH close to neutrality.) In addition, both inventions can be used as gelling agents. Since a solid drug is used, the handling and drug preparation work are less dangerous than when using only a liquid strong acid (such as phosphoric acid) as a gelling agent, which is advantageous.

For these reasons, both inventions can be said to be pollution-free soil stabilization methods that are one step more advanced than conventional methods.

Next, the present invention will be explained with reference to comparative examples and examples.

Comparative Example JI8 135 cc of water was added to 65 cc of No. 3 sodium silicate to dissolve it, and this was used as liquid A.

On the other hand, 200 CC of aqueous solutions of component (a) at various concentrations as shown in Table 1 were prepared and used as Solution B.

Table 1 shows the properties of the mixed solutions A and B (grout) and the relationship between pH and gel time.

As is clear from Table 1, the grout made by combining only the sodium silicate aqueous solution and hydrogen sulfate gels at various gel times even in the neutral to acidic range, but as soon as parts A and B are mixed, the grout gels. A fine gel forms in the liquid.

Examples 1-2 (method of the present invention) A liquid A similar to that of the comparative example was prepared.

On the other hand, 200 CC of an aqueous mixture of the two components (a) and (b) at various concentrations as shown in Tables 2 and 3 were prepared, and this was designated as Solution B.

Tables 2 and 3 show the properties of the mixed solutions A and B (grout), the relationship between pH and delta rice, and the soil test results.

As is clear from the description in Tables 2 and 3, grout made by adding both components a and b to an aqueous sodium silicate solution maintains a uniform solution state until it gels even in a neutral to acidic region.

Examples 3 to 8 (method of the present invention) A liquid A similar to that of the comparative example was prepared.

On the other hand, (a) at various concentrations as listed in Tables 3 and 4
, (b) and (c) 3 component mixture aqueous solution 200C
Solution C was prepared and used as Solution B.

Table 4 shows the properties of the mixed solutions A and B (grout), the relationship between n and gel time, and the soil test results.

As is clear from the descriptions in Tables 3 and 4, (a), (
b) Grout made by adding component (c) to a sodium silicate aqueous solution in addition to the surrounding component not only maintains a uniform solution state until it gels in a neutral to acidic region, but also (C)
The strength of the treated soil can be increased compared to grout with no added ingredients.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between gel time and pH of grout made with a combination of sodium silicate aqueous solution and phosphoric acid, and Figure 2 is a graph showing the relationship between pH and gel time of grout made with a combination of sodium silicate aqueous solution and hydrogen sulfate. This is a graph showing the relationship between.

Claims (1)

[Claims] 1(a) Alkaline hydrogen sulfate salt. (b) The respective oxides or hydroxides of magnesium and zinc in amounts up to 10% by weight relative to component (a). Stabilization of soil quality characterized by mixing a mixture of the above two components (a) and (b) with an aqueous sodium silicate solution, injecting grout with - in the neutral to acidic range into soil, and gelling in the soil. cation law. 2(a) Alkaline hydrogen sulfate salt. (b) The respective oxides or hydroxides of magnesium and zinc in amounts up to 10% by weight relative to component (a). (C) Phosphoric acid or hydrogen phosphate in an amount of about 20-25% by weight, based on component (a). The method is characterized in that a mixture of the above three components (a), (b) and (C) is blended into a sodium silicate aqueous solution, and the grout whose pH is in the neutral to acidic range is injected into the soil and gelled in the soil. Soil stabilization method.