JPS59152986A - Impregnation method for ground - Google Patents

Abstract

PURPOSE:To solidify the ground firmly and completely by easy operations without causing pollution, by injecting a primary grout material consisting of suspension containing an electrolyte substance of polyvalent metal to the ground, impregnating a secondary grout material containing colloidal solution of silicic acid to it. CONSTITUTION:The casing 2 is inserted through the injection hole 1 into the ground, the injection pipe 5 having the part of the extrusion hole 3 covered with the rubber 4 is then inserted into it, the space between the casing 2 and the injection pipe 5 is sealed with the sleeve grout 6, and casing 2 is pulled out. The strainer pipe 8 equipped with the packer 7 is inserted into the injection pipe 5, a primary grout solution consisting of suspension containing an electrolyte of polyvalent metal is injected into the ground, after which a secondary grout solution consisting of a colloidal solution of silicic acid is injected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a ground injection method using a colloidal solution of silicic acid.

[Prior art and its problems]

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, the alkali metal salt of silicic acid exhibits high alkalinity, and its gelation also occurs in the alkaline region, so 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 change.
It had the disadvantages of low strength and very short gelation time.

That is, typically 81 in the injection liquid in water glass grout.
The concentration of SiO2 must be 10% by weight or more from the viewpoint of strength (uniaxial crushing strength of consolidated sand of 1 #/ta or more), but if the concentration of SiO2 is 10% by weight or more, the gelation time will be shortened. It takes less than 1 minute near the neutral range (PH 4 to 8), but usually takes a few seconds. It has been empirically found that the gelation time suitable for good permeability and solidification without dispersing in the ground is 30 to 120 minutes, but if the gelation time is near the neutral region, 51 if you are trying to get about 30 to 120 minutes.
The concentration of 02 must be 5% by weight or less, and at this concentration, the consolidated sand strength does not even reach 0.5 k'i/cr/l, making it practically unusable for the injection method. In addition, water glass is added to the water glass grouting acidic solution in the neutral range to neutralize the alkali in the water glass to obtain the injection solution, so it is natural that the injection solution contains neutralized water. Many neutralized products, such as Na ions and acid radicals, remain, but from the standpoint of water quality conservation, nothing would be better if an injection method could be established that does not leave these Na ions or acid radicals.

Another known method is to add water glass to an acidic solution and use it in the ground injection method. This method takes advantage of the phenomenon of gelation through silicic acid.
In addition, 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.

[Purpose of the invention]

An object of the present invention is to provide a further developed technique to solve the above problems.

[Key points of the invention]

In order to achieve the above object, according to the present invention, an injection material containing a polyvalent metal electrolyte substance (a substance that dissociates polyvalent metal ions) is injected as a primary injection material, and then a secondary injection material containing a colloidal solution of silicic acid is injected. The method is characterized in that a next injection material is injected into the ground.

[Embodiments of the invention]

The colloidal solution of silicic acid (silica sol) in the present invention is one obtained by removing or reducing Na ions from water glass, for example, by passing the water glass through an ion exchange resin to remove Na ions in the water glass, or It is obtained by neutralizing water glass with sulfuric acid 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 resulting 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. A relatively fluffy (dilute) silica sol is obtained by ion exchange. 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 also used in which the mixture is heated under a suitable alkali and activated silica sol is further added thereto for stabilization.

In the silicic acid colloidal solution of the present invention, for example, most of the Na ions are separated and removed. Ill, the molar ratio is preferably 10 or more, the pH is usually adjusted to weak alkalinity of 8 to 10, and the content of 5i02 is IO to 60 (X
(weight) and molar ratio (S + 02/Na2O) adjusted to 50 or more is desirable. If the molar ratio is lower than 10, the silicate colloid will dissolve and become an aqueous solution of silicate.

Of course, acidic to neutral silicic acid colloids obtained by stabilizing with acids, aluminum, ammonium, etc. can also be used.

Further, the particle size of the silicic acid colloid is mainly about 6 to 50 mμ, and when the particle size of the colloid is 50 mμ or more, precipitation tends to occur.

Usually, silicic acid colloid has a molar ratio (S io2/Na2O)
1000 to 10, and the pH is preferably 8 to 10 in terms of colloid stability.

The silicic acid colloid solution 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 factory to the site or 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 reason why a silicic acid colloid solution is gelled by an electrolyte substance is that it is electrically neutralized by dissociated ions of the electrolyte substance and colloids bond together. Specifically, silicic acid colloids are normally negatively charged in water, but in this case, the silicic acid colloids are electrically neutralized by, for example, metal ions, and the colloids bond together. Alternatively, colloidal solutions of silicic acid are usually
It is stable at a pH of 8 or above, preferably between 9 and 10, and is most unstable at around PI (5). Therefore, when an acid is used as an electrolyte, the dissociated hydrogen ions cause a colloidal solution of silicic acid to become acidic at a pH around 5. This seems to be because it is oriented to the side, becomes unstable, and becomes easier to gel.

According to the research of the present inventor, the reactivity of silicic acid colloid and various electrolytes is as follows. It is difficult to reduce this to within a few hours.

(2) When silicic acid colloid and alkali metal salt are mixed, the gelation time can be made shorter than when using an acid, but there is a limit to this.

(3) When a polyvalent metal electrolyte is mixed with silicic acid colloid within 2% by weight of the total mixed solution, it immediately becomes cloudy or scuttling, and fluidity can be obtained by mixing the mixture, but overall gelation is It is difficult to effectively control the gelation time because the gelation time is not clear and the obvious gelation time is unclear.

Among the above reactions, the present inventor focused on the reaction between silicate colloid and polyvalent metal electrolyte, and as a result of research, found the following.

■ Polyvalent metal electrolytes react most easily with silicate colloids.

■ As a result of the reaction, scuttling occurs immediately and fluidity is lost, but
The strength of the resulting gel itself is significantly higher than that of other electrolyte-based gels. The presence of scuttling as a result of the O.sub.2 reaction inhibits the fluidity of the injection solution and inhibits its penetration into fine-grained soil.

■ Polyvalent metal electrolytes do not cause silicic acid colloids to scuttle in very small amounts, but they have a significant effect on promoting gelation of silicic acid colloids.

In order to effectively utilize the above-mentioned characteristics for the purpose and means of the injection method, the present inventor has proposed the following method: (1) When a suspension containing a polyvalent metal electrolyte is used as the primary injection material, While the above suspension is filled mainly in the rough part,
A liquid corresponding to the supernatant liquid of the suspension permeates into the rough areas. Furthermore, since the secondary cloud is a suspension, it is filled mainly in rough areas, so it is difficult to escape.

When silicic acid colloid is injected as a secondary injection material, a reaction between the silicic acid colloid and the polyvalent metal electrolyte caused by the secondary injection material immediately occurs in the rough areas of the ground, forming a strong gel, which creates a strong framework in the ground. At the same time, it prevents the silicic acid colloid from escaping and allows the silicic acid colloid to penetrate in the direction of the thin portion. Although the content of polyvalent electrolyte substance in the thin part is small, it nevertheless has the effect of promoting gelation of silicate colloid, so it cannot be gelled by silicate colloid with a sufficiently long gelation time or alone. Even if silicic acid colloid is used as a secondary grout, it is possible to firmly consolidate a predetermined area.

and polyvalent metal electrolytes in the present invention - chlorides, sulfates, phosphates, nitrates of alkaline earth metals, aluminum, transition metals, or rare earth metals, or their hydroxides, oxidized substances, etc. Cement is also included because it contains calcium hydroxide.

What is the suspension in the present invention, such as cement, quicklime, etc.? I'1
lime, gypsum, calcium silicate, calcium carbonate,
Slag, bentonite, fly ash, stone powder, etc.

The reason why the electrolyte substance (metal ion) is highly reactive with the silicic acid colloid and produces a large gel strength is thought to be that it chemically combines with the silicic acid colloid to form a water-insoluble metal salt of silicic acid. That is, when this colloidal solution of silicic acid is treated with, for example, cement or Ca(OH), it is thought that the colloids are linked together via Ca to form a polymeric insoluble calcium silicate compound and gel. Table 2, Table 3,
Table 4 and Table 5 show the gel strength and compacted sand strength measurement results shown in Table 6. Note 18i02: Z3X H2804: 0.3%
Cement: 25N Note 2 8i0z: 23X Hz8
04: 0.3% Ca(OH)z: 35% Note 38i
02:23% H2SO,: 0.3% Ca C70
: 2.5% slag: 20% Note 48i0a: 23% H2SO: 0.3% A
k (804)3: 2.5% fly ash: 30
%ff58i0z: 23X H2804: 0.3%
Ca (OH)2: 20X slag: 20% Tables 1 to 6, especially Table 6, show the following.When using hydrochloric acid or alkali metal salt as a reactant, the strength of the gel is small 0 (■,
■)0 On the other hand, when using a polyvalent metal electrolyte and the mixture is so thick that it loses its fluidity, the gel strength shows a large value, (■, ■; @l@)% Especially Suspension type materials such as cement and lime have great strength.

(■.

■,■,■).

Furthermore, even in the case of water-soluble polyvalent metal salts, the strength increases when used in combination with other suspensions such as slag and fly ash. l + @ + [phase]) Q If you use a suspension containing a polyvalent metal electrolyte as the primary grout and inject a mixed solution containing silicate colloid as the secondary grout, it will react in the ground and become solid. It can be seen that it solidifies.

The above-mentioned construction method of the present invention requires the construction method shown in Fig. 1 or 2 during construction.
This is done using the injection tube shown in the figure. In other words, the injection tube has a discharge port that allows re-injection at a predetermined depth of the injection tube (Fig. 1).
Either the primary injection material is injected into the ground through the holes, and then the secondary injection material is injected in a layered manner, or a multi-pipe rod is used to prevent the secondary injection material from escaping outside the designated area. Next, it is possible to use a method in which the injection materials are overlapped and injected.

(Figure 2).

To explain FIG. 1, first, a casing 2 is inserted into a predetermined ground through an injection hole 1. Next, after inserting the injection pipe 5 whose discharge port 30 is surrounded by rubber 4, the space between the casing 2 and the injection pipe 5 is sealed with sleeve grout 6, and the casing 2 is pulled out. - Insert the pipe 8 into the injection tube 5 and inject the next ground injection agent from the injection pump (not shown). Then,
After this injection is completed, a secondary grouting agent is injected.

To explain Fig. 2, Fig. 2(a) shows a situation in which a double pipe is used to send poling water from the lower discharge port 12 of the inner pipe [O] to drill a hole to a predetermined depth.

13 is a metal crown. Thereafter, as shown in FIG. 2(b), the primary injection material is sent through the outer pipe 9 and injected into the ground through the upper discharge port 11, while the secondary injection material is sent through the inner pipe 10 and is injected into the ground through the lower discharge port 12. By moving from the bottom of the injection stage to the top while injecting it into the ground, the secondary injection material is superimposed on the area where the primary injection material was injected.

Example The following comparative injection test was conducted on sandy ground in the Tokyo area.

For primary grau) CG-1), the following formulation was used per I-.

G-10 slaked lime 100 units, remaining water.

G-1■ Slaked lime 50#, cement 50%, remaining water.

Cr-1 ■ 100 kg of cement, remaining water.

G-1■ Calcium chloride 50 stain, residual water.

G-1■ Calcium chloride 25#, cement 25kg
, residual water.

G-1■ Slaked lime 50kg, plaster 50#, residual water.

G-10 slaked lime 50kg, slag 50kg, remaining water.

The following formulation was used for the secondary glau (G-2).

G~2■ Colloidal solution of silicic acid shown in Table-1.

A colloidal solution of silicic acid shown in Formulation No. 4 in Table G-20.

G-2 ■ A colloidal solution of silicic acid shown in Formulation No. 8 in Table 4.

G-2■ A colloidal solution of silicic acid shown in Formulation No. 5 in Table-5.

The injection amount was 50t for the sequential injection per 1m depth, 250t for the secondary injection, and 2m intervals with a pitch of 25cm, and the injection method (H) was as follows.〇Primary injection is not performed. In this case, the secondary injection per meter is 30
It was set to 0t.

H-■ Method using the injection tube shown in Figure 1.

H-■ Method using the injection tube shown in Figure 2.

H-■ Rod injection.

One day after the first injection, a second injection was performed, and a water permeability test was conducted at the center the next day. The results are shown in Table-7.
8.

The permeability coefficient of the ground without injection is = 2.5XIo cm/sec.

Table-7 Water permeability test results when using G-2(b) (k:cn1
/ viscera) Table 8 Results of water permeability test using G-]■ (k: cm
/sea) The following was found from the results of the post-injection test.

The injection effects by injection method are in the order of H-■, H-■, and H-■.

In addition, as secondary injection materials, G-2■, G-2■, G-2■,
Comparing G-2■, it is found that the hydraulic permeability coefficients of the others are approximately 1/100 to 1/5 smaller than G-2■, and when the silicic acid colloid is destabilized and injected Furthermore, it was found that the injection effect was improved.

Furthermore, only the secondary injection is performed without performing the next injection at an injection depth of 30
When 0 t was injected at a time, almost no consolidation effect was obtained by G-2■. Although the consolidation effect of G-2■, G-2■, and G-2■ was observed, the hydraulic conductivity was 10 to 100 times the size of a deer compared to the case of primary injection. Indicated.

Also, after adjusting the excavation and performing the primary injection, H-■
In , H-■, a cylindrical solidified material with a diameter of approximately 1 m was obtained, but in the case where the second injection was not performed and the rod injection, the diameter was 0.3 m to 2.0 m. [Effects of the Invention] As described above, the present invention is based on the following method: after injecting the above-mentioned primary injection material, a secondary injection material containing a silicate colloid solution is layered. Since it is injected into the ground, it is possible to solidify the ground firmly and completely, and furthermore, it is easy to operate and non-polluting, making it extremely useful in practice.

[Brief explanation of drawings]

Both FIGS. 1 and 2 show a specific example of an injection pipe for carrying out the construction method of the present invention, and FIG. 2(a) shows a concrete example of the injection pipe. (b) shows a process diagram of the method of the present invention 0 1...Injection hole, 3...Discharge port, 5...Injection pipe, 9
...outer pipe, 10...inner pipe, 11...upper discharge port,
12...Lower discharge port. Patent applicant: Uki2Koku Reinforced Soil Engineering Co., Ltd.

Claims (1)

[Claims] A ground injection method characterized by injecting a primary grout material made of a suspension containing a polyvalent metal electrolyte into the ground, and then injecting a secondary grout material containing a colloidal solution of silicic acid into the ground.