JPH037236B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a grouting method using a special alkali silicate and a chemical that reacts with the alkali silicate for soil improvement. [Prior Art] 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 is reacted with sodium hydroxide, but the current mainstream method is the dry method. In either method, the resulting water glass is colloidal (and also glassy). And Si or SiO in water glass
The O bond in is bonded to another atom and is not free or ionized. Even in the wet method, after the silica sand and sodium hydroxide have reacted, the total time required for stock time in the factory, transportation time, and waiting time for construction at the site is at least one month. On the other hand, although water glass has the advantage of being inexpensive, penetrating well into soil particles, and being safe in terms of pollution, there are limits to its strength and water-stopping properties even when combined with other materials or hardeners. The Joosten method is an old method of reacting water glass with a hardening agent. This method involves reacting water glass with calcium chloride, CaCl ₂ , to instantly produce silicate gel. [Problem to be solved by the invention] However, this construction method is instantaneous and aims to improve the water-stopping properties of the ground by producing a gel. It's not something you can do. 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 water glass with other materials to generate crystals between soil particles. The purpose 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 disadvantages that it does not necessarily have a high strength-increasing effect and water-stopping properties, and to achieve the same level of permanence as cement. The aim is to ensure that [Means for solving the problem] The above problem was solved by using an activated liquid obtained by adding alkali hydroxide to silica or alkali silicate and leaving it for 1 to 14 days to age, and magnesium chloride, zinc chloride, aluminum chloride, or dichloride. Using a reaction solution consisting of an aqueous solution of 2 iron, first inject the reaction solution into the target ground, then inject the active solution between 1 and 14 days after adding the alkali hydroxide, so that it comes into contact with the soil for the first time. The solution is to inject it into [Function] First, the present inventor 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 M ₂ O.
nSiO ₂ (M is a monovalent alkali metal) is an aqueous solution in which silicic acid is ionized and activated by adding a hydroxide of a monovalent alkali metal (hereinafter also referred to as activated liquid). ) is obtained, but if one day or more passes after the reaction, the silicic acid compound is fragmented in places and ionized. Also after the reaction
If 14 days or more pass, the ionized silicic acid will polymerize.Secondly, as mentioned above, if an aqueous solution of M ₂ O・nSiO ₂ is injected into the ground while it is in an ionized state, the soil in the ground will be When the particles are reacted with calcium, etc., a crystal of xM′O・ySiO ₂・zH ₂ O (M′ is a metal, and if calcium is used, M′ is Ca) is formed, and along with this crystal formation, It has been found that this method exhibits excellent permanence, significant strength improvement, and high hydraulic permeability, which are not seen in the conventional methods using water glass-based chemicals. Although this reaction process is not necessarily clear, it is thought to be as follows. For example, consider the case where an active liquid obtained by reacting water glass and sodium hydroxide is reacted with a calcium chloride solution in the ground. () Contact of water glass with sodium hydroxide () Activation (ionization) due to contact according to () above That is, water glass reacts with NaOH, and the bonds of water glass are broken in places, resulting in the ionic state of (A) or (B). Whereas conventional general water glass is colloidal and nonionic, the present invention
The ionic state liquid (active liquid) of (A) or (B) above is
It has a special behavioral state of being non-colloidal and ionic. Moreover, because the molecules are fragmented, the molecular chains are short. This size is approximately 0.1 mμ to 1μ. When the activated liquid thus obtained comes into contact with calcium chloride in the ground, xCaO ₂ ySiO ₂ .
A crystal of zH ₂ O (for example, _3CaO.2SiO 2.3H ₂ O) is generated. This process will be schematically explained with reference to FIGS. 1 and 2. Using an injection tube, liquid B (for example,
When CaCl ₂ ) is injected, liquid B is adsorbed around the soil particles 1. After that, when the A liquid as the first liquid according to the present invention is injected, the B liquid adsorbed on each soil particle and the activated water glass come into contact, and the Na content of the B liquid and the B liquid are mixed.
Ca content undergoes a substitution reaction, and crystals are generated between soil particles 1, 1..., which grow, and each soil particle 1, 1...
...Fill the gaps closely. 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. The inventor recognized that activated alkali silicate reacts with calcium salts to form crystals, but after further research to see if other reactants could be used, it was found that the active alkali silicate reacts with calcium salts and forms crystals. We have found something that is practical. The present invention is therefore proposed. That is, in the present invention, magnesium chloride, zinc chloride,
It turned out to be aluminum chloride or ferric chloride. [Specific Structure of the Invention] The present invention will be explained in further detail below. According to the present invention, first, an aqueous solution of the general formula M ₂ O·nSiO ₂ (where M is a monovalent alkali metal),
The basic product is an activated alkali silicate (activated liquid) in which silicic acid is ionized and activated by adding a monovalent alkali metal hydroxide. 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. To obtain an active liquid, silica may be directly dissolved in an alkali hydroxide such as NaOH, KOH, or LiOH, or a commercially available activated alkali silicate such as water glass may be reacted with an alkali hydroxide.
As silica, pyrogenic silica, diatomaceous silica, gaze 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 a commercially available water glass, one approximately No. 3 may be used and the molar ratio of SiO ₂ /Na ₂ O may be adjusted to a desired value. The activated liquid thus obtained is 1 to 14 hours after its manufacture.
Must be used during the day. Figure 3 shows the molar ratio
The graph shows the time change in unconfined compressive strength when the liquid obtained by reacting 3.4 No. 3 water glass with 30% sodium hydroxide was reacted with an aqueous calcium chloride solution. From the figure, it can be seen that in order to obtain the target strength of 10 Kg/cm ² or more, it is necessary to set the pot life to between 1 and 14 days. Particularly preferred is 1 to 7 days. This pot life is specified because it takes at least 24 hours for the molecular chains to cleave, and recombination occurs after 14 days. A similar thing is seen when water glass is reacted with KOH and LiOH. In order to reliably generate crystals, it is desirable that the active liquid contains 60%, especially 80% or more of non-colloidal silica. The viscosity of the active liquid is 5 to 50 cps, in order for it to penetrate between soil particles.
Especially desirable is 20-30cps. If necessary, water may be used to adjust the viscosity. The SiO ₂ /Na ₂ O molar ratio of the active liquid is preferably 1.5 to 2.5. The smaller the molar ratio is, the better the silicic acid molecules are divided and the greater the crystallization effect, but if the molar ratio is too small,
It is expensive because the amount of NaOH used is large,
Furthermore, there remains a concern that alkali may not completely react with Ca salt and remain in the soil, causing alkali pollution. If the purpose is to improve initial physical properties and reduce material costs, the molar ratio should be 2.0 to 2.5. Figure 4 shows the change in strength over time as the molar ratio changes. A typical reaction liquid that reacts with such an active liquid is a calcium salt solution, but although it cannot be expected to have much strength, the present invention can be used when the primary purpose is to stop water in the ground. According to
Aqueous solutions of magnesium chloride, zinc chloride, aluminum chloride or ferric chloride are used. The CaO/SiO ₂ ratio of the entire chemical solution is preferably 0.3 to 1.5. On the other hand, even if the active liquid and the reaction liquid are reacted in a beaker in a laboratory setting, crystals will not be formed or the reaction will not be sufficient.
Even if they are combined before or inside the injection tube, the reactivity of both liquids is high, so a gelatinized product will form.
Since this is injected into the ground, no crystals are formed, and it is similar to injecting ordinary water glass-based chemicals, making it impossible to create 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, desired crystals can be produced. As a specific example of such a separate injection method, as shown in FIG. 5, the reaction solution (solution B) is injected in a certain step, and then the active solution (solution B) is injected in the same step, preferably within 30 minutes. This is done by Furthermore, if necessary, the injection of liquid B→liquid A (→) may be repeated in the same step. After completing the construction in the same step, step up and inject liquid B → liquid A. As shown in FIG. 6, two injection pipes may be arranged side by side and the two liquids may be mixed at different injection timings. As shown in FIG. 7, the same injection pipe may be used to inject each liquid from injection ports at different injection positions at different times, and the liquids may be merged in the ground. P is for Pazka. When injecting the active liquid and the reaction liquid with a time difference, the active liquid may be injected first, as explained above using Figures 1 and 2, but generally the viscosity of the active liquid is low. Therefore, it may be pushed away by the subsequent highly viscous reaction liquid and escape from between the soil particles. On the other hand, according to the present invention, when the reaction liquid is brought first, it has a high viscosity so that it remains suitably between the particles and is not pushed out by the succeeding active liquid. As a result, an improved body with high strength and excellent water-stopping properties can be achieved. [Example] Next, the effects of the present invention will be explained with reference to Examples. Reference example 1 Water glass with a Na ₂ O/SiO ₂ molar ratio of 3.4 (SiO ₂ : 24.8
%, H ₂ O; 67.7%, Na ₂ O; 7.5%) commercial product 80
and 48% NaOH to 30% 22 were reacted and left for 36 hours. Thereafter, in order to adjust the viscosity, this was diluted with 1/4 volume of water to obtain an active liquid. On the other hand, 75 kg of calcium dihydroxide was dissolved in 10 7 of water to obtain a reaction solution. After that, both liquids were injected into the mold at a ratio of 100:110 and the order of injection was determined, and the other liquid was injected 15 minutes after the first liquid was injected. We investigated the changes. The results are shown in Table 1.

【table】 The formulations of conventional examples are shown in Table 2.

[Table] From the results in Table 1, it is clear that according to the method of the present invention, it is possible to create an improved body that has higher compressive strength, excellent water-stopping properties, and is more permanent than the conventional method. It can also be seen that the strength is higher when the reaction solution is applied first, although the water-stopping properties are inferior. In addition, the formation of crystals was observed in the obtained solid body when observed under an electron microscope. Reference example 2 The same water glass as in reference example 1 was mixed with KOH and
Table 3 shows the results of reacting with LiOH to obtain an active solution and injecting calcium chloride first.

[Table] Table 4 shows the strength results. The amounts of the active liquid and the reaction liquid were the same as in Reference Example 1, and the injection order was that the reaction liquid was first injected, and then the active liquid was injected after 15 minutes had elapsed. Furthermore, Example 1 and Reference Example 3 Changes in strength and hydraulic conductivity were investigated in cases where a reactant different from the reactant according to the present invention was used, and the results shown in Table 4 were obtained. The active solution was the same as in Reference Example 1, and the reaction solution was pre-injected and
This is an example of active liquid injection after 15 minutes.

〔Effect of the invention〕

As described above, according to the present invention, the active liquid and the reaction liquid are not combined in the injection tube, but the reaction liquid is first injected, and then the active liquid is injected with a time difference. As a result, the active liquid is injected while the metal ions in the previously injected reaction liquid are adsorbed to the soil particles, ensuring sufficient gaps between the soil particles and ensuring that the reaction liquid is well-prepared. This prevents the instantaneous caking that occurs when both liquids are injected at the same time, preventing them from penetrating between soil particles. can be generated. Furthermore, along with the formation of such crystals, it is possible to create an improved ground structure that is excellent in permanence, durability, and water-stopping properties. Furthermore, since an inexpensive material is used as a reactant with the active liquid, even if the strength is not sufficient, it is still strong enough for practical use when compared with conventionally used water glass modifiers. It is true.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams of the crystal formation process according to the present invention, Figure 3 is a correlation diagram showing changes in activation maintenance over time, and Figure 4 is a case where the Na ₂ O / SiO ₂ molar ratio is changed. Figures 5 a-c, 6, and 7 are intensity-time correlation diagrams for the separate injection method (merging method in the ground).
8 to 10 are graphs showing the compressive strength when using the improver of the reference example in relation to the case when using the conventional improver.

Claims (1)

[Claims] 1 Activated liquid obtained by adding alkali hydroxide to silica or alkali silicate and leaving it to mature for 1 to 14 days,
Using a reaction solution consisting of an aqueous solution of magnesium chloride, zinc chloride, aluminum chloride, or ferric chloride, first inject the reaction solution into the target ground, then add the active solution within 1 to 14 days after adding the alkali hydroxide. A grout injection method characterized by injecting the grout so that it makes contact with the ground for the first time.