JP3932562B2 - Ground injection agent - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a ground injection agent made of silica sol.
[0002]
[Prior art]
Conventionally, in order to strengthen the soft ground or to stop the groundwater from flowing out from the ground, a chemical solution is injected into the ground, and a gel of the chemical solution is generated in the ground. Such a chemical solution is called a ground injecting agent, and various types are already known. As such a ground injection agent, a chemical solution comprising water glass and its curing agent has been generally used, but various improved ground injection agents have been proposed in recent years.
[0003]
For example, an acidic silicic acid aqueous solution is prepared by removing alkali in this liquid from a liquid obtained by adding water glass to the acidic liquid, and the neutral consisting of this acidic silicic acid aqueous solution and an alkali as its curing agent. A ground injection that gels in the area has been proposed. Furthermore, Japanese Patent Application Laid-Open No. 54-73407 discloses a ground injecting agent comprising a silica sol obtained by removing most of the alkali content from a water glass aqueous solution by a cation exchange method and a curing agent thereof. Yes.
[0004]
[Problems to be solved by the invention]
The water glass-based ground injecting agent has the advantage of a short setting time and a high setting strength, but depending on the case, a large amount of sodium salt and hardening agent from the ground after the injection is injected There are many problems such as the acid used as leaching into the surrounding soil, contaminating the soil, and the ground once strengthened thereby loosening again over time.
[0005]
On the other hand, the silica sol-based ground injection obtained by removing the alkali in the water glass by the cation exchange method increases the strength of the gelled product over time, and the gelled product has a small water permeability. Although the coefficient is maintained, the durability is also excellent, but the silica in this gelled product is amorphous and shows a solubility of about 150 ppm in neutral water at room temperature. Silica in this gelled product is constantly eluted to the outside at a concentration and does not have complete durability.
[0006]
The present invention seeks to provide an improved silica sol-based ground injecting agent, particularly a ground injecting agent having sufficient durability so that silica does not elute from its gelled product.
[0007]
[Means for Solving the Problems]
Ground infusate invention, an aqueous silica sol having an adjusted concentration of SiO ₂ 1-50 wt% was to a pH of 4 to 9, from 0.5 to 15 wt%, adjusted to a pH of 4-9 Al ₂ O It is obtained by blending an aqueous alumina sol having ₃ concentrations in a ratio of 0.1 to 50 parts by weight of Al ₂ O ₃ in the alumina sol with respect to 100 parts by weight of SiO ₂ in the silica sol.
[0008]
Any conventionally known aqueous silica sol can be used, but colloidal silica having an average particle diameter of 3 to 20 nm is contained as SiO _{2 in} a concentration of 1 to 50% by weight. Acidic or alkaline aqueous silica sols are preferred. In particular, colloidal silica having an average particle diameter of 3 to 10 nm is preferably contained as SiO _{2 at} a concentration of 5 to 30% by weight and having a pH of 9 to 11.
[0009]
Such an aqueous silica sol can be easily obtained by a known method. For example, it can be obtained by removing the alkali in the aqueous glass solution by a cation exchange method or by removing the alkali in the solution obtained by adding water glass to the aqueous acid solution. Alternatively, it can also be produced by the methods described in US Pat. No. 3,711,419, US Pat. No. 3,714,064, Japanese Patent Publication No. 4-55127, and the like.
[0010]
Any conventionally known aqueous alumina sol can be used, but an acidic aqueous alumina sol having an Al ₂ O ₃ concentration of 0.5 to 15% by weight is preferred. Such an aqueous alumina sol is produced by, for example, a method of adding metal aluminum powder to an acid aqueous solution while stirring little by little, or a method of peptizing an aqueous dispersion of an alumina gel with an inorganic acid or an organic acid. be able to.
[0011]
The ground injecting agent of the present invention comprises the silica sol and the alumina sol in a ratio of 0.1 to 50 parts by weight, preferably 0.5 to 10 parts by weight of Al ₂ O _{3 in} the aqueous alumina sol with respect to 100 parts by weight of the SiO _{2 in} the aqueous silica sol. It is obtained by blending. This blending can be performed by sufficiently mixing the silica sol and the alumina sol with stirring.
[0012]
The ground injection agent of the present invention can contain an additive for adjusting the gelation time or increasing the strength of the gelled product. Examples of such additives include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and sulfamic acid; organic acids such as formic acid, acetic acid and citric acid; acidic salts such as acidic sodium sulfate, sodium bicarbonate and primary sodium phosphate Ammonium salts such as ammonium sulfate and ammonium bicarbonate; metal salts such as sodium chloride, calcium chloride, magnesium sulfate, aluminum sulfate, and sodium aluminate. In addition, the ground injection agent of the present invention can contain any component as long as the object of the present invention is achieved.
[0013]
By adjusting the SiO ₂ concentration, Al ₂ O ₃ concentration, pH, etc. in the ground injecting agent, a ground injecting agent having a gelation time from several minutes to several hours can be obtained.
When an aqueous silica sol is mixed with a highly soluble aluminum compound such as basic aluminum chloride or sodium aluminate, a heterogeneous gel is formed. Therefore, the chemical obtained by such mixing cannot be used as a ground injection agent.
[0014]
Highly active aluminum ions are present on the surface of the alumina sol, but the solubility of aluminum ions is extremely low at a neutral pH, so that the silica sol and the alumina sol can be uniformly mixed. When the above-described aqueous silica sol and aqueous alumina sol are mixed to prepare a chemical solution exhibiting a pH near neutral, this chemical solution can be used as a ground injection agent that gels uniformly.
[0015]
In the chemical obtained by this mixing, very few aluminum ions are released from the surface of the alumina particles into the liquid, breaking the electric balance of the silica sol, causing the silica sol to gel, and It is considered that stable allophane is formed on the surface of the silica particles by combining with the silica particles. Since the silica particles covered with allophane no longer elute silica, the gelled product of the chemical obtained by this mixing exhibits durability.
[0016]
When silica sol and alumina sol are mixed at a ratio of 0.1 part by weight or less of Al ₂ O ₃ part of aqueous alumina sol to 100 parts by weight of SiO ₂ part of aqueous silica sol, the above-described silica elution preventing effect is not sufficient. The higher the Al ₂ O ₃ / SiO ₂ weight ratio in this mixture, the earlier and completely the silica elution can be prevented, but even if it is increased to an Al ₂ O ₃ / SiO ₂ weight ratio of 50 or more, it corresponds to that. The effect is not obtained.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
When blending the aqueous silica sol and the aqueous alumina sol, it is preferable to adjust the pH of the sol to 4 to 9 by adding an inorganic acid or an organic acid to the sol before mixing. The ground injection obtained by mixing the sol so adjusted produces a uniform gelled product. The SiO ₂ concentration in the ground filler is also preferably 10-30% by weight. If this concentration is 1% or less, the strength of the ground, prevention of water permeation, etc. cannot be sufficiently increased, and this concentration is increased to 30% or more. However, the equivalent effect cannot be obtained.
[0018]
【Example】
As the aqueous silica sol used, an aqueous silica sol having a SiO ₂ concentration of 15% by weight and a pH of 6.0 by adding 5% by volume of sulfuric acid to a commercially available aqueous silica sol having a pH of 9.5 and a particle size of 4-6 nm. (S ₁ ) was prepared.
As the aqueous alumina sol used, a commercially available acidic aqueous alumina sol having an Al ₂ O ₃ concentration of 10% by weight is diluted with water to produce an acidic aqueous alumina sol (A ₁ having an Al ₂ O ₃ concentration of 3.5% by weight). ) Was prepared.
[0019]
Separately, as an aqueous alumina sol to be used, an acidic aqueous alumina sol (A ₂ ) having an Al ₂ O ₃ concentration of 10.4 wt% is obtained by peptizing alumina powder having a boehmite structure in 0.5 wt% hydrochloric acid. Prepared.
Example 1
A ground injection agent (G ₁ ) was prepared by mixing 90 ml of the silica sol (S ₁ ) and 10 ml of alumina sol (A ₁ ). This injectant (G ₁ ) had an Al ₂ O ₃ / SiO ₂ weight ratio of 0.024 and exhibited a gel time of 6 minutes.
[0020]
After the gelled product was cured in a sealed container at 23 ° C for 7 days, the gelled product was transferred to a 200 ml polystyrene bottle, and 50 ml of ion-exchanged water was added to the bottle. Soaked in water. The bottle was then sealed and the gel was cured in water at 23 ° C. for 7 days. After opening the bottle, collecting water from the bottle, filtering the water with a filter paper, and measuring the concentration of dissolved silica in the water using an inductively coupled plasma emission spectrometer, it was 54 ppm. It was.
[0021]
Example 2
67 ml of the silica sol (S ₁ ) is designated as A liquid, and 1 ml of the above alumina sol (A ₂ ), 17 ml of water and 15 ml of 50 wt% magnesium sulfate aqueous solution are designated as B liquid, and these A liquid and B liquid are mixed. The ground injection agent (G ₂ ) was prepared. This injectant (G ₂ ) had an Al ₂ O ₃ / SiO ₂ weight ratio of 0.01 and exhibited a gel time of 80 minutes.
[0022]
In the same manner as in Example 1, the concentration of dissolved silica in the water soaked with the gelled product was measured and found to be 65 ppm.
Comparative Example 1
A ground injection agent (G ₃ ) was prepared by mixing 67 ml of the silica sol (S ₁ ) and 10 ml of a 50 wt% magnesium sulfate aqueous solution. This infusate (G ₃ ) showed a gel time of 30 minutes. In the same manner as in Example 1, the concentration of dissolved silica in the water soaked with the gelled product was measured and found to be 153 ppm.
[0023]
Comparative Example 2
A ground injection agent (G ₄ ) was prepared by mixing 67 ml of the above silica sol (S ₁ ) and 33 ml of 20% by weight potassium chloride aqueous potassium chloride solution. This infusate (G ₄ ) showed a gel time of 10 minutes. In the same manner as in Example 1, the concentration of dissolved silica in the water soaked with the gelled product was measured and found to be 15300 ppm.
[0024]
【The invention's effect】
The ground injecting agent of the present invention can be injected by adopting a construction method similar to the conventional method to the ground that has been conventionally constructed, such as clay ground, sand ground, and gravel ground. Since the amount of silica eluted from the gelled product of the ground injecting agent of the present invention is extremely small, by using this injecting agent, it is possible to perform ground improvement with extremely excellent durability. And according to this ground injection agent, the soil around the ground which injected this is not polluted with an acid, an alkali, a salt, etc.

Claims (1)

4-9 of an aqueous silica sol having an adjusted concentration of SiO ₂ 1-50 wt% were in pH, an aqueous alumina sol having a regulated 0.5 to 15% by weight of Al ₂ O ₃ concentration pH of 4-9 A ground injection agent formed by blending 0.1 to 50 parts by weight of Al ₂ O ₃ in the alumina sol with respect to 100 parts by weight of SiO ₂ in the silica sol.