JPS60124686A - Pouring of grout into ground - Google Patents

Abstract

PURPOSE:To solidify ground to have high strength, excellent water stopping property and excellent durability comparable to that of cement, by pouring a first soln. obtained by ionizing silicic acid for activation and a specified second soln. into ground separately for confluence in the ground. CONSTITUTION:First soln. (A) which is an aqueous soln. of a compd. of formula, M2O.nSiO2 (where M is a univalent alkali metal) having a viscosity of 5-50cps and second soln. (B) which is an aqueous soln. of a metal (M') compd. (e.g. CaCl2) are poured into ground through separate pouring pipes for confluence and solidification in the ground. The compd. M2O.nSiO2 is obtained by adding a univalent alkali metal hydroxide to silicic acid for ionization and activation and has an SiO2/M2O molar ratio of 1.5-2.5 and a non-colloidal silica content of 60% or higher. The metal (M') compd. forms crystals of formula, xM'2O.ySiO2. 2H2O through interaction with alkali metal.

Description

[Detailed description of the invention]

[Technical Field of the Invention J] The present invention relates to a chemical injection method using a special alkaline silicate chemical for soil improvement. [Technical background of the invention and its problems 1 It is widely used to improve the strength and water-stopping properties of the ground by injecting a chemical solution into the ground. In this case, a water glass-based chemical is generally used from the viewpoint of pollution prevention and cost. Water glass is produced by a dry method in which silica sand and soda carbonate are reacted, or a wet method in which silica sand and sodium hydroxide are reacted, but the current mainstream method is the dry method. Regardless of the method, the water glass obtained is colloidal (
It is also glassy), and the 0 bonds of Si or SiO in water glass are bonded to other atoms and are not free or ionized.
Even in the wet method, after the silica sand and sodium hydroxide react, the total time required for stocking at the factory, transportation time, and waiting time for construction at the site is at least 1 month. On the other hand, although ice crows have the advantage of being inexpensive, penetrating well into soil particles, and being safe from the standpoint of pollution, there are limits to their strength and water-stopping properties even when combined with other materials or hardeners. An old method of reacting water glass with a hardening agent is the Joosten method. This method involves reacting calcium chloride (CaCl2) with ice crow, which instantly produces silicic acid gel. but,
This construction method is instant setting, and is intended to improve the water-stopping properties of the ground through gelation, and does not generate crystals as in the present invention. Furthermore, it is thought that the reason why it is not used much at present is that although it has excellent water-stop properties, it is not very effective in improving the strength of the ground. In any case, to date, no attempt has been made to improve the ground by reacting ice crow with other materials to generate crystals between soil particles. [Objective of the Invention] The object of the present invention is to take advantage of the advantages of water glass itself, such as its economic efficiency and good permeability, while solving its drawbacks that it does not necessarily have a high strength-increasing effect and water-stopping property. The aim is to ensure the same permanence as [Basic Findings of the Invention j The present inventor first discovered that when silica sand or a silica sand compound, such as water glass, is reacted with an alkali metal hydroxide or carbonate, the general formula M20·n5io□(M is an aqueous solution containing a monovalent alkali metal (monovalent alkali metal), and by adding a hydroxide of a -valent alkali metal, an activated liquid in which silicic acid is ionized and activated can be obtained, but after one day of the reaction, When the above period of time elapses, the silicic acid compound is divided in places and ionized. Furthermore, if 14 days or more pass after the reaction, the ionized silicic acid will polymerize, and secondly, as mentioned above, during the ionized state, M20・n5i
When an Oz aqueous solution is injected into the ground and reacted with calcium etc. between the soil particles in the ground, xsio□ yM'
o.ZH20 (M' is a metal, and if calcium is used, A° is C'a) crystals are formed, and with this crystal formation, there is an advantage never found in the conventional method of using a water glass-based chemical solution. It was found that the steel exhibits excellent durability, significantly improved strength, and high hydraulic conductivity. Although this reaction process is not necessarily clear, it is thought to be first-order. For example, consider the following case where an active solution obtained by reacting water glass and sodium hydroxide is reacted with a calcium chloride solution in the ground. (I) Contact between water glass and sodium hydroxide... (1) (II) Activated ionization accompanying contact according to (I) above, that is, water glass reacts with Na0)1, and the bonds of water glass are broken in places. and becomes the ionic state (A) or CB). While conventional general water glass is colloidal and nonionic, the active liquid according to the present invention has a special behavioral state of being noncolloidal and ionic. Moreover, since the molecules are fragmented, each molecular chain is short, with a size of about 0.1 μm to 1 μm. When the thus obtained active liquid comes into contact with calcium chloride in the ground, xcaO+, *ysio2 conflict 2H
20 (e.g. 3CaO* 2Si02 e 3H20
) to produce crystals. To schematically explain this process with reference to FIGS. 1 and 2, liquid B (
When cac12) is placed in the column, liquid B is adsorbed around the soil particles l. After that, when the A liquid is injected, the B liquid adsorbed on each soil particle comes into contact with the activated water glass, and the Ha content and the Ca content of the B liquid undergo a substitution reaction, and each soil particle l. Crystals are generated between the soil particles 1.1 and 1.1, and these crystals grow and densely fill the spaces between each soil particle. This makes it possible to maintain the permanence of the chemical solution, and also to improve the overall strength of the ground and its water-stopping properties. [Summary of the Invention J The present invention to achieve the above object is based on the general formula M20.n
5io2 (here, the wing is a monovalent alkali metal), and by adding a -valent alkali metal hydroxide, silicic acid is ionized and activated, and the first liquid is substituted with the alkali metal. TexH'Qa ysi02 War 2
This method is characterized by injecting a second liquid consisting of an aqueous solution of a metal (M') compound that forms crystals called H20 so that they do not merge in the injection pipe but in the ground. The above-mentioned activated alkali silicate reacts with, for example, a calcium salt to form crystals. However, in this case, it has been found that when both liquids are mixed in a beaker in a laboratory, they form a gel and the desired crystals are not produced, or even if some of them are produced, it is not sufficient. On the other hand, it has become clear that during on-site construction, if the injection tubes are not merged in or before the injection pipe, but are first merged in the ground, the formation of the desired crystals can be sufficiently prevented. The reason for this is that, as is clear from the above explanation of the crystal formation process, crystals are formed only by a relatively slow reaction between soil particles. Therefore, it is necessary to inject one liquid first and the other liquid later, or to inject the two liquids at different positions.

[Specific examples of the invention]

The present invention will be explained in more detail below. According to the present invention, first, the general formula M zO・n5iOz (
Here, a is an aqueous solution of a monovalent alkali metal), and by adding a -valent alkali metal hydroxide, silicic acid is ionized and activated.
(hereinafter also referred to as active liquid) is the basis. Here, potassium, sodium, lithium, etc. are used as the alkali metal. Although other high-level alkalis can be used, they are not suitable because they are expensive and emit radiation. In order to obtain an active liquid, silica may be directly dissolved in an alkali hydroxide such as NaOH-KOH-LiOH, or a commercially available activated alkali silicate such as water glass may be reacted with an alkali hydroxide. As the silica, pyrogenic silica, diatomaceous earth, Geso or silica aerogel can be used. A practical alkali hydroxide is sodium hydroxide. If silica is simply dissolved in sodium hydroxide, it may be thought at first glance that it is the same as water glass produced by a wet method, but while conventional water glass is in a stable state, the present invention Water glass has a distinct difference in its activated state. In reality, water glass is often used for soil improvement and the like, and is commercially available at low cost. Therefore, it is preferable to react this commercially available product with alkali hydroxide to produce an active liquid. As commercially available water glass, use a size 3 or so to obtain the desired 5iOz
/Na2Q molar ratio may be adjusted. The active solution thus obtained must be used within 1 to 14 days after its production. Figure 3 shows the time change in uniaxial compressive strength when a liquid obtained by reacting No. 3 water glass with a molar ratio of 3.4 and 30% sodium hydroxide was reacted with an aqueous calcium chloride solution. From the same figure, the target of 10kg/
In order to obtain a strength of 1-14 cm or more, the pot life must be 1-14 cm
It turns out that it is necessary to do it during the day. Particularly preferred is 1 to 7 days. This pot life is stipulated by the fact that it takes at least 24 hours to break one molecular chain, and if it exceeds 14 days,
This is thought to be due to recombination occurring. The same thing is
It is also seen when water glass is reacted with KOH and LiOH. In order to ensure the formation of crystals, it is desirable that the active liquid contains 6 oz, especially 80% or more, of non-colloidal silica.The viscosity of the active liquid is such that it can penetrate between soil particles. 5-50cps, especially 20-30c
p s is preferred; water may be used to adjust the viscosity if necessary. Active liquid cy) 5iOz/NazO molar ratio is 1.
5 to 2.5 is preferred. The smaller the molar ratio, the better the separation of silicic acid molecules and the greater the crystallization effect; however, if the molar ratio is too small, the amount of NaOH used will be large, resulting in high costs, and the alkali will not completely react with the Ca salt, causing water to fall into the soil. There are also concerns that they may remain in the water and cause alkali pollution. If the purpose is to improve initial physical properties and reduce material costs, the molar ratio should be between 2.0 and 2.5. Figure 4 shows the change in strength over time as the molar ratio changes. Indicated. A typical reaction solution that reacts with such an active solution is a calcium salt solution. Examples of the calcium salt include calcium chloride, calcium formate, calcium acetate, and calcium propionate. The chemical solution as a whole has no eah/5i (h ratio is 0.3
-1.5 is desirable, and among these, calcium chloride is optimal because it has excellent solubility and is inexpensive. However, Mg, Zn, AI and trivalent Fe
Chlorides, hydroxides or carbonates selected from the group of can also be used. Even if the active solution and the reaction solution are reacted in a beaker in the laboratory, crystals will not be formed or not enough. Even if they are combined before the injection tube or inside the injection tube, the reactivity of both solutions is high, so a gel will not form. Since a compound is generated and this is injected into the ground, no crystals are generated, and it is similar to injecting ordinary water glass-based chemicals, creating a permanent and strong solid. On the other hand, if both liquids are injected separately and brought into contact for the first time in the ground, it is possible to produce the desired crystals. As a specific example of such a separation injection method, as shown in FIG.
This is done by injecting the reaction solution (solution B) in one step, and then injecting the active solution (solution A) in the same step, preferably within 30 minutes, and if necessary, injecting the reaction solution (solution B → solution A) in the same step. You may repeat the injection of (→). Once the construction of the same step is completed, step up and inject liquid B → liquid A. As shown in Figure 6, connect the two wooden injection pipes in parallel. Alternatively, the two liquids may be combined. As shown in FIG. 7, each liquid may be injected from injection ports at different injection positions using the same injection tube. P is packer. When injecting the active liquid and the reaction liquid with a time difference, the active liquid may be injected first, but since the viscosity of the reaction liquid is generally low, it will be pushed by the following highly viscous active liquid and escape from between the soil particles. Sometimes. On the other hand, if the active liquid is used first, it has a high viscosity, so it remains suitably between the soil particles and is not pushed out by the subsequent reaction liquid. As a result, an improved body with high strength and excellent water-stopping properties can be created. In addition, when performing this type of ground improvement, the ground is often treated in some way first, a typical example of which is treatment with cement. In this case, free calcium remains in the cement, so when the active liquid is injected,
It can react with free calcium in cement to form crystals. Furthermore, even if the ground itself is originally calcareous ground, it can be reacted with the active liquid. However, since the remaining amount of such calcium content is small, it is often necessary to supplementally inject the reaction solution. In the well-known tretanche injection method, the area around the injection pipe is packed with cement bentonite, and the active liquid reacts favorably to this. As a modification of the case where the reaction solution is injected in advance, a calcium chloride solution is first injected, and then sodium hydroxide is injected to form precipitates of calcium hydroxide between soil particles.
It is also an effective method to inject the active liquid after a certain period of time. The reaction formulas are expressed by formulas (3) and (4). CaG12 +NaOH+Ca(OR')z ↓+2N
aCl −・(3)Ga(OH)z +NazO'i
n5iOz −+xCaO* ysiOz e 2H2
0--(4) Since the reaction in equation (3) is a reaction that causes Ca(OH)z to precipitate, it will not be pushed out from between the soil particles by the active liquid. Only Ca
By pre-forming a precipitate of (OH)z, the active liquid and Ca(E12
It is effective as an auxiliary method for the main reaction with reaction liquids such as In addition, the order of injection of the active liquid and the reaction liquid is preferably that the active liquid precedes the rough layer, the reaction liquid precedes the medium sand layer, and the active liquid precedes the active liquid in the ground where there is a lot of groundwater. By the way, in addition to using the activated liquid at room temperature, if you heat it to 40°C or higher to increase the amount of dissolved reactants such as calcium chloride, and then inject it, the liquid will become liquid at the time it is poured into the ground. As the temperature decreases, a supersaturated state occurs, and it is an effective method to utilize this to create a state where it is easy to react with the active liquid. Note that the active liquid according to the present invention can also be used for repairing cracks in concrete structures. [Example J] Next, the present invention will be explained in detail with reference to Examples. (Example 1) Maze/5if2(1)% Le ratio 3.4 no water gara
Si02: 24.8'X, HzO: 87.7X,
NazO Near, 5$) (7) Commercial product 80Jl 48%
30% NaOH was reacted with 22 sentences, 3
It was left for 6 hours. Then, to adjust the viscosity, add 1
An active solution was obtained by diluting with 4 times the amount of water. On the other hand, 75 kg of calcium chloride dihydrate was dissolved in 1071 g of water to obtain a reaction solution. After that, add both liquids to the mold at 100%
The other solution was injected 15 minutes after the previous solution in an amount of 110% and the order of injection was determined. - Changes in axial compressive strength and hydraulic conductivity over time were investigated. The results are shown in Table 1. Table 1 The formulations of conventional examples are shown in Table 2. From the results shown in Table 2 and Table 1, it is clear that the method of the present invention can produce improved bodies that have higher compressive strength, better water-stopping properties, and are more permanent than the conventional method. It can also be seen that the strength is generally higher when the activation liquid is used first. Furthermore, in the present invention example, formation of crystals was observed when observed under an electron microscope. (Example 2) The same water glass as in Example 1 was reacted with KOH and LiOH to obtain an active liquid, which was then injected with calcium chloride in advance. Table 3 shows the results. Table 3 The strength results are shown in Table 4. Table 4 (Example 4) U associated with activation retention time (When the relationship between usage time and liquid temperature was investigated, the results shown in Figure 8 were obtained. Effects of the invention) As described above, the present invention Because activated alkali silicate is used, it is possible to create a permanent improved product through crystal formation, and it is also possible to improve the strength and water-stopping properties.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of the crystal formation process according to the present invention, FIG. 3 is a correlation diagram showing time changes in activation maintenance, and FIG.
The figure shows the intensity-time correlation diagram when the NazO/5i02 molar ratio is changed, and Figures 5 (a) to (C), Figures 6 and 7 show the separate injection method (merging method in the ground). Schematic diagram, No. 8
The figure is a correlation diagram of the degree of activation based on the difference in liquid temperature. Figure 1 qa3 Figure 4 Figure 5 (0) (b) (C)

Claims (5)

[Claims] (1) It is an aqueous solution of the general formula M2011nsr02 (where N is a monovalent alkali metal), and by adding a hydroxide of a -valent alkali metal, silicic acid is ionized. Replace the alkali metal with the first liquid which has been converted into a phosphor and has been activated. and a second liquid consisting of an aqueous solution of a metal (Mo) compound that forms crystals of °0.2S io□.zHzo. Injection method. (2) The chemical liquid injection method according to claim 1, in which the second liquid is heated to 40° C. or higher. (3) The chemical liquid injection method according to claim 1, wherein the times of injection of the first liquid and the second liquid are staggered. (4) The chemical liquid injection method according to claim 1, wherein the injection positions of the first liquid and the second liquid are separated from each other in the injection pipe. (5) The chemical liquid injection method according to claim 1, in which the injection of the first liquid and the second liquid is repeated in the same injection zone while shifting the timing of injection.