JPH0362749B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention aims to inject a grouting agent obtained by mixing a silicate aqueous solution and a cement suspension into soil and gel it, thereby solidifying soil particles to strengthen the soil and make it impermeable to liquids. This relates to construction methods that stabilize soil quality. It has been well known that soil quality can be stabilized by grouting agents using silicate. As silicate-based grouting agents, silicate-cement-based suspension types and silicate-water-soluble hardener-based solution types are known. Regarding the suspension type, it is difficult to adjust the gelation time, and in particular, it is difficult to gel in a short time.
In addition, it has the advantage of being less expensive and highly effective in stabilizing the soil compared to solution-type grouting agents, but in recent years, there has been a demand to further increase the gel strength of the grout itself and the strength of the stabilized soil. There is. However, it is known that an alkali metal salt of aluminate is added to a cement suspension as a hardening agent in order to shorten the gelation time of the grout, but in this case, the stability of the cement suspension may be affected. There was a drawback that the suspension tended to gel during storage or transportation. In view of the current state of the conventional soil stabilization treatment methods mentioned above, the present invention provides soil stabilization treatment that allows gelation time to be easily adjusted over a wide range by using a cement suspension with good storage stability, and has good workability. The purpose of this invention is to provide a soil stabilization method that can achieve gel strength and compacted soil strength equivalent to or better than conventional methods. Therefore, the gist of the present invention is as follows: Solution A: aqueous solution of alkali metal salt of silicic acid Solution B: contains blast furnace colloidal cement, alkali metal salt of aluminate, water, and a chelating agent, and the weight ratio of water to cement is 1. - 6 Aqueous Suspension A soil stabilization treatment method characterized by injecting into soil an aqueous mixed solution obtained by mixing both solutions A and B above. Examples of the alkali metal salt of silicic acid in liquid A include sodium silicate, potassium silicate, etc., and sodium silicate (also known as water glass) is particularly suitable.
Standardized in JIS K 1408 as an aqueous solution 1
Sodium silicate No. 2, No. 3 is commonly used. The amount to be used is determined appropriately depending on the condition of the soil to be injected and the purpose. For example, when using sodium silicate No. 1 to No. 3 based on the above JIS,
The amount is 5 to 50% by volume, preferably 10 to 40% by volume, based on the aqueous mixture. The blast furnace colloidal cement used for liquid B has different components from general cement, and has the characteristics of being resistant to seawater and having good permeability due to its fine particle size. The amount of blast furnace colloidal cement used is usually expressed as the weight ratio of water to cement in the cement suspension (hereinafter abbreviated as W/C), and in the present invention, W/C in liquid B is 1 to 1.
6. The larger the amount of blast furnace colloidal cement, the stronger the solidified soil strength and the strength of the gelled material of the injected liquid itself. However, if the W/C is too small, the fluidity of the water suspension will deteriorate, and if it is too large, the injected liquid will become stronger. The gel strength and compacted soil strength will decrease. Examples of the alkali metal salt of aluminate used in the B solution include potassium salt, sodium salt, lithium salt, etc. of aluminate, and sodium aluminate is particularly frequently used. These aluminates are used alone or in an appropriate mixture; if the amount used is too small, the strength of the gelled product of the aqueous mixture and the strength of the compacted soil will be low, and if the amount is too large, no particular effect will be produced. Therefore, the content of aluminum oxide (AI ₂ O ₃ ) is usually 0.3 to 25% by weight based on the above aqueous mixture.
It is preferably used in a range of 0.5 to 18% by weight. The chelating agent used in Solution B is an inorganic substance that can combine with metal ions generated when blast furnace colloidal cement is suspended in water to form a chelate compound.
Organic substances are widely used, and specific examples of organic substances include polybasic acids such as oxalic acid, malonic acid, succinic acid, maleic acid, and itaconic acid, lactic acid, β-oxyacid, glyceric acid, gluconic acid, malic acid, tartaric acid, Oxyacids such as citric acid and salicylic acid, their sodium acids and potassium salts, ethylenediamine,
Aliphatic amines such as diethylenetriamine, N,N-di-ethylenediamine, ethylenediaminetetraacetic acid, aromatic amines such as α,α′-dipyridyl,
Examples of inorganic substances include amino acids such as alanine, asparagine, aspartic acid, glucine, glutamic acid, and serine, and nitrocarboxylic acids such as nitroacetic acid. Specific examples of inorganic substances include condensed phosphoric acids such as pyrophosphoric acid, tetrametaphosphoric acid, trimetaphosphoric acid, and triphosphoric acid. , its sodium and potassium salts. Among these chelating agents, ease of handling,
Oxyacids and dibasic acids are commonly used from the viewpoint of ease and economy in producing chelate compounds, and tartaric acid, citric acid, and their sodium and potassium salts are particularly preferred. In the present invention, a part of the metal ions generated when the blast furnace colloidal cement used in the B liquid is suspended in water combine with the chelating agent, thereby forming a bond between the metal ions and the alkali metal salt of aluminate. It is presumed that the reaction is inhibited or delayed and as a result, the B solution is stabilized. Also, although the reason is unknown, when using the same amount of the above aqueous mixture as a conventional suspended soil stabilizer to which no aluminate or chelating agent is added,
It was found that a larger amount of soil was consolidated than before, and that the strength of the consolidated soil was higher. If the amount of the above chelating agent used is too small, B
Since the stability of the liquid deteriorates and coagulates are formed if the amount is too high, generally 0.03~
The amount is 1.5% by weight, preferably 0.05-1.2% by weight. For example, in a conventional suspension grouting agent that uses a curing agent that does not contain an alkali metal salt of aluminate, which is made only of water and cement, a silicate aqueous solution and a cement suspension are mixed and then gelled. Even if it was quick, it would take about 2 minutes,
If necessary in the present invention, the composition of B liquid and A,
By appropriately adjusting the mixing ratio of both liquids B, it is possible to make the gelation time several seconds. Next, in order to stabilize soil quality according to the present invention, an aqueous liquid mixture obtained by mixing the above-mentioned liquids A and B is injected into the soil. Injecting the aqueous mixture into the soil is usually carried out by using an injection pump to force the mixture through a pipe inserted into the soil. In the present invention, it is preferable that a fixed amount of both liquids A and B, which are prepared separately, are simultaneously sent to the injection pipe, where the two liquids are brought together and mixed. In the present invention, the B liquid does not usually gel for several hours at room temperature, so it does not solidify in the pipe before being mixed with the A liquid. Of course,
In some cases, it is also possible to introduce the A and B solutions into a mixing tank, stir and mix them, and then feed them to the pipe. The mixture thus injected into the soil becomes a hydrogel when it reaches a preset gelation time depending on the amount of blast furnace colloidal cement, alkali metal salt of aluminate, etc. contained therein, and the mixture is injected into the soil. This stabilizes the soil quality by immobilizing soil particles within a range, imparting high unconfined compressive strength to the soil, and imparting liquid impermeability to the soil. The soil stabilization treatment method of the present invention is configured as described above, and is characterized by injecting into the soil an aqueous liquid mixture obtained by mixing the above-mentioned liquid A and liquid B, which has good storage stability. Therefore, there is no need to mix the B solution with the A solution immediately after adjustment, the B solution does not gel in the injection pipe, and the gelation time of the aqueous mixture can be extended from a short time to a long time. Workability is good in that it can be easily adjusted over a wide range, and since the W/C is specified, the fluidity of the B solution and even the aqueous mixed solution is good, and according to the present invention, the alkali of aluminate Compared to construction methods using conventional suspension grouting agents that do not contain metal salts, it is possible to consolidate a large amount of soil and obtain consolidated soil with high unconfined compressive strength. This makes it possible to obtain a gelled product of the injection liquid that has the high strength required for injections and the like. In particular, since the blast furnace colloidal cement used in the present invention has fine particles compared to general cement, it has greater permeability and has the advantage of being able to immobilize soil particles over a wider area, and is also a gel that has high resistance to seawater. Because it can give monsters,
It is also suitable for stabilizing soil quality where seawater contamination is expected. Examples of the present invention are shown below. The term "parts" or "%" refers to parts by weight or percentages by weight. Examples 1 to 4 Solution A consisting of 112 parts of No. 1 sodium silicate based on JIS K 1408 and 25 parts of water, and sodium aluminate (powder, containing ₃₇ % Al ₂ O) having the composition shown in Table 1.
A chelating agent and a B solution prepared by adding water to blast furnace colloidal cement were prepared. The stability of this B solution at 20°C and the volume ratio of A and B solutions of 1:1.
The unconfined compressive strength measured when gelur time and the cured product were mixed at a ratio of 1:1 and cured in wet sand for 7 days were as shown in Table 1.

【table】

[Table] Comparative Examples 1 to 6 Soil stabilizers were prepared in exactly the same manner as in Examples 1 to 4, except that liquid B having the composition shown in Table 2 was used, and the gelation time and strength of each gelled product were measured. .

[Table] * Sodium citrate The results are shown in Table 2.
In Comparative Examples 2 and 4, the compressive strength of the gelled product was significantly inferior to that of Examples 1 and 2, which had the same amount of blast furnace colloidal cement, and in Comparative Examples 3 and 4, which contained sodium aluminate in liquid B but did not contain a chelating agent. The gelation time of the liquid was too fast to be of practical use. In addition, Comparative Example 5, in which the ratio of water to cement in liquid B is too small, has a short gelation time of liquid B, resulting in poor fluidity; conversely, in Comparative Example 6, in which the ratio of water to cement in liquid B is too large, liquid A. The compressive strength of the gelled product of liquid B was extremely low. Examples 5 and 6, Comparative Example 7 Approximately 30 Toyoura standard sand was placed in an iron cylinder with a diameter of 5 cm.
Filled to cm length. Next, 250 c.c. of the injection solution having the composition shown in Table 3 was poured into the upper part at a pressure of 1 kg/cm ² and after curing, it was cured in a closed state for 7 days. After 7 days, the cured product was demolded and used as Toyoura standard sand. The consolidated volume of and its unconfined compressive strength were measured.

[Table] The results are shown in Table 3. According to the method of the present invention, the volume of soil consolidated and its It was confirmed that the unconfined compressive strength increased significantly.

Claims (1)

[Scope of Claims] 1 Solution A: Aqueous solution of alkali metal salt of silicic acid Solution B: Contains blast furnace colloidal cement, alkali metal salt of aluminate, water, and a chelating agent, and the weight ratio of water to cement is 1 to 1. 6. Aqueous Suspension A soil stabilization treatment method characterized by injecting into the soil an aqueous mixed solution obtained by mixing both the above-mentioned solutions A and B. 2. The method according to item 1, wherein the alkali metal salt of silicic acid is a sodium salt or a potassium salt. 3. The method according to item 1 or 2, wherein the alkali metal salt of aluminic acid is a sodium salt, potassium salt, or lithium salt. 4 The amount of chelating agent is approximately 0.03% of the aqueous mixture.
~ about 1.5% by weight, the method according to any one of paragraphs 1 to 3. 5. The method according to any one of Items 1 to 4, wherein the chelating agent is at least one of an oxyacid, a sodium salt of an oxyacid, and a potassium salt of an oxyacid. 6. The method according to item 5, wherein the oxyacid is tartaric acid or citric acid.