JPS60144382A - Grouting method and grouting apparatus - Google Patents

Abstract

PURPOSE:To strengthen soft ground economically with good strength and durability without causing environmental pollution, by using a destabilized aq. silicic acid soln. as a grouting material obtd. by treating a water-soluble silicate with a cation exchange resin. CONSTITUTION:A water-soluble silicate (e.g. JIS No.3 sodium silicate which is diluted so as to give a destabilized aq. silicic acid soln. having an SiO2 content of 2-10%) in a reservoir 1 is passed through an alkali removing column packed with a cation exchange resin. The resulting destabilized aq. silicic acid soln. [SiO2/Na2O (molar ratio) of 50 or above, pH: 2-10] is fed to a stock soln. reservoir 4 and injected through an injecting pipe 3 into soft ground by means of a grout pump 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground injection method and an injection device that have excellent strength and durability and can prevent pollution.

A common method for improving soft ground is to inject wood containing water glass as the main ingredient.

Although water glass-based lumber is inexpensive and the gelation time can be easily adjusted, it has two major drawbacks.

One is that water glass is a strong alkaline substance, so is it an acidic reactant? Even when used, the cured product must be alkaline in order to obtain a practically acceptable gelling time, and the leached alkali contaminates groundwater.

Theoretically, a neutral hardened product can be obtained by adding an acidic substance equivalent to the amount of alkali contained in water glass to neutralize it, but adding such an amount of an acidic substance instantly causes a non-uniform gel. Since it is practically unusable, generally an acidic substance with an amount less than the alkali equivalent is used as a curing agent, and therefore, the problem of alkali contamination of ground water as mentioned above arises. Another major drawback is that the durability of the cured product is poor.

Unreacted water glass and salts produced by the reaction between the curing agent and water glass gradually elute from the cured product, resulting in a decrease in the strength of the cured product.

Therefore, there is no problem when the purpose is short-term ground improvement, but it is not preferable when durability is required, such as ground improvement during dam construction.

The following methods are available to improve these drawbacks of water glass-based lumber. One method is to add a hydrogel to a strong acid such as sulfuric acid to form an acidic silicic acid aqueous solution, and use this as a main ingredient to neutralize and harden with an alkaline curing agent.

This method is a preferable method for improving alkali contamination of groundwater, but since the main agent contains a large amount of salts such as N'a2S04 produced by acid and alkali of water glass, the elution of this salt is difficult. There is a problem with the accompanying changes in groundwater quality. Furthermore, the method of adjusting the gelation time by changing the Q PH using a strong acid has the problem that the gelation time changes too rapidly, making it difficult to adjust the gelation time.

In addition, the acidic silicic acid aqueous solution maintains a long gelation time in an acidic region, but if it is contaminated with alkali and gels in a neutral region, the gelation time is greatly shortened and the PH increases. Between 5 and 8, the gelation time is several minutes to several seconds, and there is a problem that sufficient permeability cannot be obtained.Q Another method Another method uses neutral colloidal silica as the main ingredient. This method generally involves condensing and stabilizing a commercially available product as a neutral silica sol, that is, an active silicic acid aqueous solution (unstable silicic acid aqueous solution) obtained through an ion exchange resin, to a molecular weight of several tens of thousands or more by heating, etc.
02 content is concentrated to 20-30% and has a diameter of 10
This method uses a dispersion of particles on the order of mμ as the main ingredient.

This neutral colloidal silica has traditionally been used as a textile treatment agent, paper anti-slip agent, and paint additive, so it has been stabilized by adjusting the stability, particle size, and concentration to meet these purposes. It's widespread.

According to research conducted by the inventor of the present invention, when attempting to use such stabilized neutral colloidal silica as a soil consolidation agent, the 5i02# degree must be extremely high to achieve the purpose of injection. In particular, since the initial strength is low, the gel is easily washed away by running water. That is, for the purpose of ground injection, the unconfined compressive strength of consolidated sand is usually required to be 2 kLi/cr1 or more, but for this purpose, normal water glass grout has a water glass concentration of 30% (by weight) or more. I am using it. In terms of 5I02 concentration, this corresponds to more than 9% (by weight). However, in order to obtain the above strength using the above-mentioned neutral colloidal silica, 5i02i degree is 20 (weight)
The present invention compensates for the drawbacks of the above-mentioned techniques, and provides a ground injection method using an economical soil improvement agent that is free from pollution, has excellent strength and durability, and implements this method. The present invention provides an injection device for

In order to achieve the above-mentioned purpose, the construction method of the present invention has the following characteristics:
Furthermore, according to the injection device of the present invention for carrying out the method, an alkali removal device filled with a cation exchange resin is provided in the injection system from the water-soluble silicate storage tank to the injection pipe. Hereinafter, the present invention will be specifically explained in detail.

The destabilized silicic acid aqueous solution according to the present invention is different from commercially available colloidal silica that has been stabilized.9 It contains a large amount of silicic acid colloid with a small molecular weight, so it is active and has high strength. Not only is it suitable for the purpose of injection, but it also has extremely excellent properties for preserving water quality as most of the salt has been removed through ion exchange.
102/N, l]20 molar ratio 50 or more, PH2~IO
, substantially all of the silicon atoms of all the silicic acids in the aqueous solution have at least one silanol group that can participate in condensation, and the silanol group has steric r,
clf! An aqueous solution of silicic acid with a molecular weight of 1000 or less that is not harmful, and whose Sio2 concentration is 12% by weight or less, preferably 2 to 10% by weight. Such a destabilized silicic acid aqueous solution is ion-exchanged by supplying water-soluble silicates stored in a storage tank, such as sodium silicate, ammonium silicate, etc., to an alkali removal device containing a cation exchange resin. Fig. 1 shows a specific example of a press-in device according to the present invention using a base or alkali removing device, in which 1 indicates a water-soluble silicate storage tank. , in which water-soluble silicate is stored. This water-soluble silicate passes through the injection system 2 and enters the injection pipe 3.
will be transferred to. 4 is an injection stock solution storage tank, 5 is a grout pump, and 6 is a base or alkali removal device. The base or alkali removing device 6 is provided at any point in the injection system 2, for example between the water-soluble silicate reservoir 1 and the injection stock solution reservoir 4 as shown in the first figure. The base or alkali removal device 6 consists of a column filled with a cation exchange resin, into which the water-soluble silicate in the storage tank 1,
For example, dealkalization is carried out through a diluted water glass solution. The tower 6 after dealkalization is regenerated with acid and water, washed and reused.In addition, in FIG. 1, a plurality of towers 6 may be provided,
(Not shown) By switching and using this, it is possible to continuously produce a dealkalization injection stock solution.

Note that a tank-type alkali removing device may be used instead of the base or alkali removing device. As shown in Figure 2, the ion exchange resin and a certain amount of diluted water glass are put into a tank 6 equipped with an ion exchange resin filtration device and a stirrer 7, stirred for a certain period of time, and then injected through the filtration device after dealkalization. The stock solution is transferred to the storage tank 4. The ion exchange resin in tank 6 is regenerated by acid and water and reused after cleaning. By providing a plurality of tanks 6 as described above, it is possible to continuously produce the dealkalization injection stock solution.

The injection stock solution (destabilized silicic acid aqueous solution) thus obtained is directly injected into the ground from the grout pump 5 through the injection pipe 3.

In addition, as shown in FIG. 3, a gel time adjustment tank 8'f is provided between the injection stock solution storage tank 4 and the grout pump 5, and the injection stock solution is fed into the tank 8 from the gel time adjustment agent storage tank 9 through the pump IO. After mixing with the regulating agent, it is injected using the grout pump 5.

Furthermore, as shown in FIG. 4, the injection stock solution and the gel time adjusting agent can be combined in the middle of the injection pipe 3 and injected using the so-called 1,5 shot method, and as shown in FIG. It is also possible to merge the adjusting agent at the outlet of the injection pipe 3 and inject it by a so-called two-shot method. In addition, in any case of FIG. 3, FIG. 4, and FIG. 5, a part or all of the gel time adjusting agent can be added to the injection stock solution storage tank 4 for use.

The destabilized silicic acid aqueous solution used in the present invention is preferably injected into the ground within a short period of time, but even if a portion of the condensation reaction occurs due to standing, the effect of the present invention may still be achieved. I can't hold on to it.

The water-soluble silicate used in the present invention preferably has a molar ratio of 1 to 5, and industrially it is preferable to use JI No. 83 sodium silicate, and its concentration is determined to facilitate the post-dealkalization process. The destabilized silicic acid aqueous solution obtained according to the present invention is preferably diluted so that the 5i02 content of the obtained destabilized silicic acid aqueous solution is 2 to 10%. It has a small particle size and good reactivity, and it gels in a short time, so in order to obtain an appropriate gelling time, a gel time regulator is added to delay the gelling time, and on the contrary, it gels. For example, 5i025 obtained by passing JI83 sodium silicate through a cation exchange resin.
%, pH 3.4, it takes about one day to gel, and it can be used as a grout material even if it is undiluted and injected. However, depending on the purpose of injection, construction conditions, and ground conditions, acid or alkaline The gelation time can be controlled by adjusting the pH or adding inorganic salts. Further, the destabilized silicic acid aqueous solution of the present invention can be used at an appropriate 5I02 concentration depending on the purpose, but the 5I02a concentration in the solution is 2 to 10% by weight.
By using a destabilized silicic acid aqueous solution, it is possible to obtain the same strength as conventional water glass grout at a lower concentration than the 5iOz concentration in conventional water glass grout, and it has excellent durability. You can get what you want. Of course,
5i is thinner than when using colloidal silica.
High strength can be obtained at 02a degrees.

Another notable feature of the present invention is that it has a longer gel time in the neutral range compared to conventional grout using an acidic silicic acid aqueous solution obtained by adding water glass to an acidic solution. The advantages are that higher consolidation strength can be obtained by adjusting the gelling time and Si02 concentration, and that the gelling time can be easily adjusted.

In addition, as a gel time adjusting agent, a small amount of acid, alkali, or inorganic salt, etc. can be used, and cement, lime, slag, etc. can also be used. Inorganic salts of are preferred. Among these, a small amount of polyvalent metal salt can shorten the gelation time. Examples of these inorganic salts include aluminum sulfate, magnesium chloride, sodium hydrogen carbonate, magnesium sulfate, aluminum nitrate, aluminum phosphate, and calcium chloride.

Since the destabilized silicic acid aqueous solution of the present invention has a low molecular weight and high reactivity, the addition rate of the gel time regulator may be small.
The gelation time can be reduced within several minutes by adding a valent metal salt in an amount of 0.1 to 1% by weight, and by adding a trivalent metal salt in an even smaller amount.

In addition, the destabilized silicic acid aqueous solution of the present invention is preferably injected in an acidic to neutral state; if it is acidic, an alkaline agent is used, and if it is alkaline, an acidic agent is used as a pH adjuster when injecting a small amount. Moreover, the destabilized silicic acid aqueous solution of the present invention does not solve the problem of pollution as mentioned above, but also can strengthen the ground with a low concentration of silica content and is excellent in durability.

In other words, with ordinary water glass grout, the strength decreases, but with the present invention, the strength of the obtained sand gel gradually increases, so it is possible to improve durability, such as when improving the ground when constructing a dam building. It can also be used for any purpose you require.

For example, when using commercially available silica gel to obtain the same glue strength as water glass grout, the 8i02 concentration in the injection solution must be 20% or more.
In the present invention, only about 5% is required.0 The destabilized silicic acid aqueous solution of the present invention is easy to manufacture, and since the silicic acid contained has a low molecular weight, there is a possibility that the destabilized silicic acid aqueous solution has little variation in hardenability and strength. It will be done.

Furthermore, the destabilized silicic acid aqueous solution of the present invention causes less salt elution and less change in groundwater quality than when using acidic silica sol. Furthermore, since the molecular weight of the silicic acid used is small and the concentration is low, the initial viscosity is low and the permeability is good.

Furthermore, the present invention has the advantage that greater strength can be obtained at a lower concentration of 5i02 and the change in gelation time due to water dilution is smaller than in the case of using commercially available colloidal silica.

Furthermore, the inactivated silicic acid aqueous solution of the present invention can be easily obtained by simply passing a diluted solution of, for example, JI No. 83 sodium silicate through an alkali removal device filled with an ion exchange resin;
It is much more economical than commercially available neutral colloidal silica because a high strength cured product can be obtained even if the content is small.

Examples of the present invention below? show.

Preparation of unstable arsenicic acid aqueous solution> Preparation example 1 Sodium silicate JI83 product (Asahi Denka Kogyo ■ product 5iOz
A diluted sodium silicate aqueous solution containing 29.0%, i''Ja209.OX) fr water and containing 5iOz 5.8% and Na201.8% was stored in a storage tank. Hydrogen type cation exchange grease resistant prepared by method (Organo ■ product, Amberly) I
R-120B) Pass the liquid through the tower (alkali removal device) and
A destabilized silicic acid aqueous solution having an Oz content of 5.8% was obtained. The pH of this aqueous solution was 2.5.

At this time, S i 02 / Na20-t-Ratio 150
0 T, the gelation time of this solution was 72 hours 0 Preparation Example 2 Instead of the diluted sodium silicate aqueous solution of Preparation Example 1, S t 0
2 7.2
The gelation time of this solution was 48 hours.

The destabilized silicic acid aqueous solution produced in Preparation Example 1.2 was transferred from the alkali removal device to the gel time adjustment tank, a gel time adjustment agent was added thereto, and the gel time was measured for the resulting injection solution, the compressive strength of the sand gel was measured, The elution of SiO2 from the homogel was measured.

The prescription is as shown in Table-10 The raw materials used in Table 1 are the following ACs.

l) Neutral silica sol: Applied AT- manufactured by Asahi Denka Kogyo ■
Sword 2) Acidic silica sol: While vigorously stirring an aqueous solution of 95% sulfuric acid 6.3 f and water 53°7 f, Si IJI No. 83 (manufactured by Asahi Denka Kogyo ■) 3
A solution of 18 f of water was poured into Of. 8i02 concentration8.
0X% PH1,83) Silica soda (JI No. 83): manufactured by Asahi Denka Kogyo ■ Other raw materials used were reagent grade 1.

The 5i02 concentration, PH, and gel time in the chemical solution in the above example are shown in Table 2.

Table 2 The chemical solution of the above prescription was poured into a mold of 5.0 brocade diameter x 10 ern L and solidified with Toyoura standard sand to obtain a sand gel for strength measurement.

The strength measurement was performed according to JI8A1216 soil unconfined compressive strength. The compressive strength of the sand gel is shown in Table 3.

Table 3 From Table 3, it can be seen that each Example of the present invention can obtain significantly greater strength at a lower concentration of 8i02 than the neutral silica sol grout (Comparative Examples 3 and 4).

From the text, Tables 2 and 3, it can be seen that each of the Examples of the present invention can be adjusted to a gelation time that allows for sufficient penetration into the ground, compared to the acidic silica sol grout (Comparative Example 2).

Furthermore, it is found that the strength is greater and the long-term strength is superior compared to the alkaline water glass grout (Comparative Example 1).

Table 4 shows the measurement results of the elution amount of 8i02, which is one measure of the durability of the cured product.

The test specimen was prepared by preparing 20 of homogels using the above-mentioned drug solution and immersing them in 10 times the amount of distilled water.

After a specified number of days, take a 200f water test and add 200f of distilled water.
Added f.

8i02 was analyzed by evaporation to dryness and weight measurement.

Table 4 The elution rate of Si02, except for Comparative Example 1, showed a constant value at the (9) cutout, and almost no elution was observed thereafter. From this, it can be seen that the product of the present invention has a low elution rate and excellent durability.Next, in order to compare the properties of the destabilized silicic acid aqueous solution and the acidic silica sol as grout according to the present invention, the 8i0z concentration was the same for both. , The relationship between PI value, gelation time, and compacted sand strength was measured. The results are shown in Tables 5 and 6.

The destabilized silicic acid aqueous solution according to Preparation Example 2 was adjusted with caustic soda and the PL (value was varied, and the 8i02 concentration was kept constant at 5% by weight).

On the other hand, the acidic silica sol shown in Table 1 was used, the pH was changed by 1 with caustic soda, and the concentration of 8i02 was kept constant at 5% by weight.

From Tables 5 and 6, it can be seen that the destabilized silicic acid aqueous solution of the present invention can obtain the gelation time necessary for sufficient penetration even in the neutral region, and has high consolidation strength.

Table 5 In case of destabilized silicic acid aqueous solution Table 6 In case of acidic silica sol Next, in order to compare the grout properties of the destabilized silicic acid aqueous solution according to the present invention and the neutral silica sol, PI ), and the gelation time is a constant value (is 10
The unconfined compressive strength (strength after curing in a wet room for 1 day) of the consolidated standard sand was measured by varying the SiO2 concentration.
To what was obtained, water was added to change the Si02 concentration, and caustic soda was added to solo the PI value.
Add NaCt and gel time 1'! In addition, in the case of neutral silica sol, use the one shown in Table 1 and add water to change the 5i02 concentration, and add sulfuric acid to solo the PI value. Table 7 shows the results obtained by adding aluminum sulfate and adjusting the gelation time to 10 minutes. More than 2Ay/c
In order to obtain a consolidated sand strength of rA or more, in the case of neutral silica sol, the 5I02 concentration must be 20% by weight or more.
It can be seen that the strength cannot exceed #/ca.

On-site construction was carried out using the injection device shown in Figure 1. Sodium silicate JI83 product (Kadenka Kogyo ■Product 5iO229,
OX, Na2O9, OX) 1301 k 5201
The solution was diluted with water and stored in reservoir l.

Next, a hydrogen-type cation exchange resin (Organo product, Amberly) was prepared in the usual manner with 10% hydrochloric acid.
The resin 1 was applied to a built-in alkali removal device 6 of 300 tons, and the diluted water glass solution was passed through it at a rate of 6 seconds and 7 hours to obtain 650 tons of a destabilized silicic acid aqueous solution in the injection stock solution storage tank 4. In order to wash away the destabilized silicic acid aqueous solution remaining in the alkali removal device 6, 350 tons of
water was drained, and this washing liquid was added to the destabilized silicic acid aqueous solution already stored in the injection stock solution storage tank 4. The obtained destabilized silicic acid aqueous solution 1000 L C+ content u S io2 concentration 5.0% by weight, SiO2/Na2O molar ratio 1500.
The pH was 2.6.

This was injected into the ground through the injection vibrator 3 by operating the grout pump 5.

Construction Example 2 A destabilized silicic acid aqueous solution was stored in the injection stock solution storage tank 4 in the same manner as in Construction Example 1 using the apparatus shown in FIG. - Next, this aqueous solution is mixed with the diluted water glass solution (gel time regulator) in the gel time regulator storage tank 9 in the gel time regulator tank 8 to reach a pH of 6.
and adjust the injection pipe 3 to operate the grout pump 5.
It was injected into the ground through.

The gel time of this injection solution was 10 minutes.

Construction Example 3 An injection test was conducted using sandy ground with a hydraulic conductivity of K = 1073 cm/jec.

Three types of injection liquid were used: a destabilized silicic acid aqueous solution, a neutral silica sol, and an acidic silica sol, and each was injected at a distance of 2 fJm. The injection depth was 5 to 3 m below the ground surface, and 250 t was injected at each stage of 0.5 m, for a total of 10,001 injections.

The injection solutions were formulated so that the Si02 concentration was 5.0% by weight. For the destabilized silicic acid aqueous solution and neutral silica sol, use the same formulation as symbol 8 in Table 7.
The gelation time was 10 minutes, and the pH value was 6.

Regarding acidic silica sol, as shown in Table 6, KP
'H6, gelation time stamp seconds formulation.

As shown above, the pH value and 8102 concentration of the three types of mixed solutions can be kept constant, but the gelation time of acidic silica sol should be the same as the others because the gelation time is faster in the neutral region. is impossible.

During injection, an observation well was set up 10 meters away from the injection point, and groundwater was sampled before (January ago), during, and after injection (3 days and 1 week later) to investigate changes in groundwater quality. did.

In addition, the hydraulic conductivity before and after injection was measured, and after the injection, excavation was conducted to observe the consolidation status, and the consolidation was collected to measure the unconfined compressive strength.

The results are as follows.

The water quality test results are shown in Table 8, and it can be seen that the activated silicic acid aqueous solution shows almost no change before, during, and after injection compared to the acidic silica sol.

Table 8 Comparing the hydraulic conductivity before and after injection, the results are as shown in Table 9, and it can be seen that the improvement in the hydraulic conductivity is extremely excellent in the case of the cine-stabilized silicic acid aqueous solution.

Table 9 In addition, the solidification status according to the excavation survey shows that in the case of a destabilized silicic acid aqueous solution, a semi-cylindrical solid with a diameter of 1m was obtained, and the unconfined compressive strength of the solidified sand was ys4#/ In the case of neutral silica sol with crl, a cylindrical body with a diameter of approximately 80 cm was obtained, but the strength of the solid body was 0.8 kfl/ca.
It was about. In the case of the acidic silica sol, the gelation time was short, so pulsatile injection was observed considerably, and the sol solidified with a diameter of 0.5 to 1.5 m, and its strength was 4.5 words/ctrl.

Construction example 4: 1 o'o of destabilized silicic acid aqueous solution prepared in the same manner as construction example 1
Aqueous solution 2 containing 4 types of Mg C12・6F■20 in oA
fJt was added to make a homogeneous solution. The above solution and aqueous caustic soda solution were injected using the apparatus shown in Figure 4 while controlling the flow rate so that the PI of the injection port was 6.5. The gel time of this injection solution was 6 minutes. 0 construction example 5 0 silicate soda J constructed according to the present invention using the equipment shown in Fig. 2
Product I83 (Asahi Denka Kogyo ■Product 5iO229.0%, N
120 t of a2O (9.0%) was diluted with 480 t of water and stored in storage tank 1.

It was then adjusted with 10% hydrochloric acid in a conventional manner. 600 t of the diluted sodium silicate was added to the alkali removal device 6 containing 300 t of hydrogen-type cation exchange resin (Organo ■ product, Amberlite 1R120B) and stirred for 15 minutes. After transferring the stabilized silicic acid aqueous solution to the injection stock solution storage tank 4, 300 tons of water was added to the device 6 and stirred in order to wash the aqueous solution adhering to the ion exchange resin, and this washing liquid was also transferred to the storage tank 4. Unstable molar ratio 1000, PH2,
It was 8.

This aqueous solution was injected into the ground through the injection pipe 3.

Construction example 6 Destabilized silicic acid aqueous solution 60 obtained in the same manner as construction example 5
0 t fIt is stored in the storage tank 4 shown in Fig. 3, and a solution of 2401 A4 (S 04 )a・181 (20 dissolved in 5 tons of water) is added thereto to make a homogeneous solution, and this solution and gel time adjuster are added. The diluted sodium silicate solution stored in the storage tank 9 was mixed in the gel time adjustment tank 8, adjusted to pH 6, and injected into the ground through the injection pipe 3 by the operation of the grout pump 5.The gel time of this injection solution is 2.5 minutes. Met.

[Brief explanation of the drawing]

1 and 2 illustrate a typical injection device according to the present invention, and FIGS. 3, 4, and 5 each illustrate a typical injection device according to the present invention with a gelling modifier reservoir. A specific example of an injection device will be shown. 1...Water-soluble silicate storage tank, 2...Injection system, 3.
... Injection pipe, 4. Injection stock tank, 5. Grout pump, 6. Alkali removal device, 7. Stirrer, 8. Gel time adjustment tank, 9. Gel time adjustment agent storage tank, 10...Pump answer 3 s Note q ff answer 1

Claims (1)

[Claims] A ground injection method characterized by: (2) A ground injection device characterized in that an alkali removal device filled with a cation exchange resin is provided in the injection system from the water-soluble silicate storage tank to the injection pipe.