JPS59124986A - Solidification of ground - Google Patents

Abstract

PURPOSE:To cause slow gelation of a grout and increase the strength of the gel, by pouring into ground a non-alkaline water glass grout which contains a neutral salt of an alkali metal, a salt of an alkaline earth metal or an aluminum salt. CONSTITUTION:0.2-7wt% at least one salt selected from among a neutral salt of an alkali metal (e.g. NaCl), an alkaline earth metal salt (e.g. NaHCO3) and an aluminum salt (e.g. AlCl3) is added to a non-alkaline water glass grout obtained by adding liquid water glass having an SiO2/M2O molar ratio of 1.5- 5.0 to a water solution of an acid reactant. The grout is pourced into soft ground or watery ground for solidification.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground consolidation method in which a consolidation liquid is injected into soft or leaking ground to consolidate or stop the ground (hereinafter simply referred to as consolidation). Regarding the construction method using a non-alkaline silicic acid aqueous solution, in detail, if the pH value is set to an arbitrary value in the acidic (5 or less) or neutral range (around 5 to 9), an arbitrary gelation time can be obtained. This invention relates to a construction method using a non-alkaline silicic acid aqueous solution.

Conventionally, the ground injection method using water glass has been to add a reactive agent to water glass.

This utilizes the gelation of water glass in the alkaline region.

However, in this method, the strength is several Kq to 10
In order to obtain a consolidation strength of /ca or higher, the concentration of water glass must be increased, and as a result, the pH of the injection solution is around 12 to 11, which causes the problem of making the groundwater alkaline. arise.

Furthermore, since unreacted water glass is present in the gel, leaching of unreacted hydraulic lath occurs over a long period of time, and as a result, the solidity cannot be expected to be permanent and its strength decreases over time. Problems also arise.

In general, if an acidic reactant aqueous solution is gradually added to a water glass aqueous solution while stirring, gelation will occur at the water glass concentration normally used in the injection method, and gelation will occur within the alkaline pH range. Even if an aqueous solution is added until the pH reaches 7 or acidic, the blended solution will solidify and fluidity cannot be maintained. 17'i, of course, if the water glass concentration is very high, the gelation time can be extended to several tens of minutes, but in this case, the strength of the consolidated sand will be reduced to IJ and below I Kg/crA. ,.

The present inventor has already added and mixed water glass into an acidic reactant aqueous solution, removed the alkali in the water glass without causing the silicic acid content in the water glass to precipitate in lumps during mixing, and obtained a non-alkaline silicic acid aqueous solution. We have invented a ground injection method in which a non-alkaline silicic acid aqueous solution is adjusted to a predetermined pH value in the acidic or neutral range and then injected.

This grout is very good because it does not change the pH value of the groundwater in the ground where it is injected, but when adjusting the gelation time, 1) Adjust the gelation time by adjusting the H value from acidic to neutral. This is intended to shorten the time.

That is, as shown in Figure 1, first, a hydraulic lath is added to the acidic liquid to form acidic water glass with a pH of around 1, and then an alkali is added to it to increase the pH value until the pH value reaches around 8 or higher. was set to a predetermined value to shorten the gelation time and then inject.

In this case, as is clear from the curve in Figure 1, the adjustment must be made on a sharp curve from a convex inflection curve (PH around 1) to a downward convex curve (PH around 8). There was a point where a small difference in the amount of alkali added caused a huge difference in gelation time.

In other words, it is good to obtain a very short gelation time when the pH value is a neutral value of 5 to 8, but it is better to obtain a slow gelation time when the pH value is in the acidic region or in the neutral region. It was almost impossible.

The present inventor has conducted research to solve these problems, and as a result, has focused on the following points.

In other words, neutral salts of alkaline metals, alkaline earth metal salts, and aluminum salts, which instantly precipitate silica in the hydroglass even if added in small amounts to water glass in the alkaline region, are in the PH region of non-alkaline water glass. Under quantitative conditions, it can exist in non-alkaline water glass aqueous solutions without producing cloudiness, and it also gently promotes gelation.
The present invention was completed based on the discovery that it also has the effect of increasing gelation strength.

The present invention described above is a ground injection method in which non-alkaline water glass grout is injected into the ground using a chemical solution obtained by adding water glass to an acidic aqueous solution. The soil consolidation method is characterized by containing 0.2 to 7% by weight of one or more salts selected from the group of natural salts, alkaline earth metal salts, and aluminum salts.

Examples of metal salts in the present invention include neutral salts of alkali metals such as NaC1z Na2SO4, I(C1,
Alkaline earth metal salts such as K12804 include Ca salt, M
? Examples of aluminum salts include aluminum chloride and sulfate.

These salts are water glass in the alkaline range, and at a water glass concentration of 20% to 60% by weight, which is normally used in waterglass grout, the total mixed liquid has M0.
．． When more than 2% is added, white turbidity immediately occurs, and when more than 1% is added, a heterogeneous precipitate is formed, making it impossible to obtain a solution-like mixture having a gelation time of at least several minutes.

However, when these salts are made to exist in a non-alkaline mixed solution that gels in any PH range using an acidic water solution obtained by adding water glass to an acidic solution and removing the alkali in the water glass, 0.2% to 7% by weight of the total blended liquid
It was found that within a range of % by weight, the blended solution could maintain a homogeneous solution without causing any scuttling, gelation was gently promoted, and the strength due to gelation was also greatly increased.

It is unclear why scuttling occurs immediately in the alkaline region and not in the non-alkaline region when using the same concentration of the above metal salts, but the presence or absence of OH ions causes the silicic acid in water glass and these metal salts to In the non-alkaline region, silicic acid and these metals react or combine slowly, or polymerization of silicic acid occurs slowly, which causes gelation to occur slowly or to form a strong gel. It is thought that this is helpful in forming the .

Furthermore, according to the inventor's experiments, no effect was observed when the content of the above-mentioned metal salt was less than 0.2% by weight of the total blended solution, while on the other hand, when it exceeded 7% by weight, the content of the metal salt in the blended solution It was found that the silicic acid content caused immediate scuttling.

It has also been found that the gelation time can be easily adjusted by using water glass or an alkaline salt in the presence of the metal salts mentioned above.

An experimental example is shown below.

Experiment 1: Prepare an acidic solution using an acid such as sulfuric acid or sulfate, and mix it with an aqueous solution of n = 3 water glass without rapid stirring to produce a non-alkaline silicic acid aqueous solution.

An experimental example of the relationship between the ratio of sulfuric acid (98%) and water glass (undiluted solution) and the P value of a non-alkaline silicic acid aqueous solution is shown below.

Sulfuric acid (98%) - Water moth, 7 (.=, 3.0) (weight ratio) In this way, a non-alkaline silicic acid aqueous solution with an arbitrary pH value can be prepared.

However, in general, the gelation time of a non-alkaline silicic acid aqueous solution corresponds well to the pH, but as is clear from the relationship between α and PH above, it is necessary to accurately adjust the pH by adjusting the amounts of water glass and acidic reactant. It is almost impossible to do this; small differences in quantity can cause large fluctuations in pH, and therefore the gelation time is likely to vary widely. In order to solve this problem, conventionally, in the first step, water glass and an acidic reactant are mixed by measurement to determine an approximate pH value of 5. on the other hand,
In the second step, the gelation time was controlled mainly by controlling the pH while adding a pH adjuster such as water glass or alkaline salt.

In contrast, in the present invention, gelation is controlled by adding the above-mentioned salt. According to this, since the pH value hardly changes, the gelation time can be controlled very easily.

According to the method described above, using sulfuric acid as the acidic agent, in the first step, the water glass concentration was 4Qwt% and the pH was 2%.
．． Examples of cases in which the pH value is slightly adjusted using sodium bicarbonate or water glass in the second step after preparing 5 to 30 mixed solutions, and the case in which the gelation time is controlled using the salt mentioned above. show.

In addition, the resulting mixed solution was used to solidify mountain sand, and the unconfined compressive strength was measured one week later.

The experimental results are shown in Table-1 and Table-2.

Table 1 Table 2 If you try to adjust the gelation time by adding water glass or alkaline salt to it, it is very difficult to adjust the gelation time, but if you use the salts mentioned above, the gelation time will be It can be seen that the adjustment is easy and the strength is greatly increased. It can also be seen that the gelation time can be effectively controlled by using salts exhibiting alkalinity1. Experiment 2 In the same manner as Experiment 1, the hydrolase concentration was 40% and the pH was adjusted to 40%.
An acidic water glass solution exhibiting a value of 24 was prepared and contained a predetermined amount of aluminum salt.

Take 70 cc of this solution with A solution and 1 to 1, and then make 30 cc of water glass aqueous solution as B solution, and check the aluminum salt content in the blended solution (mixed solution A and B), the water glass content in B solution, and the PH value. We investigated the relationship between the changes in the gelation time and the gelation time. The results are shown in FIG.

This shows that when acidic water glass containing aluminum salts (d1 water glass) or alkaline salts are added, the pH value and gelation time do not vary widely and the formulation can be adjusted very easily.

In particular, adjusting acidic water glass with a pH value of around 3 to 4,
It turns out that the area is suitable for grouting.

Further, Table 3 shows an example in which the gelation time of an alkaline salt aqueous solution (Liquid B) is adjusted to the acid water glass (Liquid A) containing the aluminum salt prepared in this way.

The composition of liquid A is as follows.

Solution A: Water glass concentration 40% Aluminum chloride concentration 1.0% PHf direct 32 Kelization time 250 minutes Table-3 From the above, the present invention provides an extremely excellent technique for adjusting the gelation time.

The reason why there is little variation in pH value and gelation time due to water glass and alkaline salts is thought to be due to the ampholytic value of aluminum salts.

Acidic agents 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 monochloride, aluminum sulfate, monocalcium phosphate, monosodium phosphate, and sodium hydrogen sulfate. , acidic salts such as aluminum sulfate and aluminum chloride; substances that generate acid groups by hydrolysis in the presence of an alkali, such as esters, aldehydes such as aldehydes, glyoxal, etc.; aqueous solutions such as carbon dioxide gas However, strong acids are the most economical.

In addition, the water glass in the present invention has a molar ratio n(Si
O2/MzO): Any 1.5 to 5.0 liquid water glass is used.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the pH of acidic water glass and gelation time, and FIG. 2 is a graph showing the relationship between the amount of water glass and the PH value of the chemical solution used in the present invention. Patent Applicant: Reinforced Soil Engineering Co., Ltd. Procedural Amendment (February 7, 1948, Director General of the Patent Office Akine, 5 years old) Husband 1, Indication of Incident 1 □IT Japan Tough Year Special R Wishing sword Z Noketo No. 2゛4°IB
o＞t 4! r,, also work hard: 3. Supplementary, Relationship with the case of the patent applicant

Claims (1)

[Claims] In a ground injection method in which a non-alkaline water glass grout is injected into the ground using a chemical solution obtained by adding water glass to an acidic aqueous solution, the non-alkaline water glass grout is a neutral salt of an alkali metal, an alkali metal salt and One or more salts selected from the group of aluminum salts.
A ground consolidation method characterized by containing 2 to 7% by weight.