JP2003176529A - Method for lowering water permeability of ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for lowering the water permeability for the purpose of spring water prevention of the sand ground or gravel ground and improvement of the weak ground. <P>SOLUTION: Two or more kinds of aqueous solutions which permeate easily into the sand ground or the gravel ground, i.e., an aqueous solution containing + bivalent or + trivalent iron ions, and an aqueous solution which oxidizes it, are simultaneously or separately poured into the ground and mixed to react in the ground. Fine deposits sparingly water-soluble are thereby produced in the ground to lower the water permeability of the ground. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a method for lowering the water permeability of the ground for the purpose of preventing spring water in the sand ground or gravel ground or improving soft ground.

[0002]

2. Description of the Related Art Conventionally, as a measure for preventing water leakage from a defective portion of a mountain retaining wall, or for preventing spring water from excavating bottom in excavation work in a place where sand or gravel ground with good water permeability continues deep underground In many cases, the chemical injection method is implemented. As a chemical liquid material to be injected, a water glass-based material or a cement-based material is mainly used.

Since water glass materials are viscous,
The injection diameter into the ground (penetration radius corresponding to L / 2 in FIG. 1) is about 2 m at the maximum. Therefore, when constructing a water blocking layer in a wide range, many injection pipes (boring holes) must be installed at intervals of about 2 m to 4 m, and the construction cost becomes very high. Water glass and organic materials may generate methane gas under the influence of anaerobic microorganisms in the ground and pollute groundwater, so their use is limited.

Cement-based materials have a small injection diameter into the sand ground or gravel ground due to the size of the cement particles. Therefore, as in the case of the above water glass material, many injection pipes (boring holes) must be installed at intervals of about 2 m to 4 m, and the construction cost becomes very high.

As described above, artificially constructing a low water permeable layer by the conventional chemical liquid injection method has a drawback that it requires a great deal of labor, construction cost and a long construction period. Next, as a result of recent research and development, for example, (1) “Water-stopping material for ground and water-stopping method for ground” disclosed in Japanese Patent Laid-Open No. 2000-104066 discloses insoluble precipitates when mixed. A method for stopping water in a ground by separately injecting a water blocking agent composed of two or more aqueous solutions to be formed and two or more aqueous solutions forming an insoluble precipitate by mixing the above. It has contents. More specifically, it is explained that the two kinds of aqueous solutions are a calcium salt aqueous solution and a carbonate or hydrogen carbonate aqueous solution, and the insoluble precipitate is calcium carbonate. Also,
The two aqueous solutions are not mixed before injection, but are injected separately and mixed with each other in the void of the ground to form an insoluble precipitate, and the injection order of the two aqueous solutions is restricted. However, it is also accepted that the injection may be performed simultaneously, or may be injected from the same location or separately from locations separated by about 1 m to 10 m. (2) Next, Japanese Patent No. 2821049 (Heisei 10
The "ground injection method" disclosed on November 5, 2015)
It is intended for water stopping of so-called running ground, using a fiber dispersion aqueous solution in which water-swellable fibers are dispersed in water as an injecting material, and in some cases adding an electrolyte to the aqueous solution is described. . In short, when the fiber-dispersed aqueous solution is injected, the water-swellable fiber swells while being entangled with the surrounding sand and gravel while moving in the ground due to the water flow, blocking the gap (runoff channel) in the ground and blocking the water. Exert. It is described that the time until the water-swellable fiber starts to swell, that is, the gel time can be adjusted by increasing or decreasing the amount of the electrolyte.

[0006]

[Problems to be Solved by the Invention] In the case of the "water-stopping material for ground and water-stopping method for ground" disclosed in the above (1), 2
When an aqueous solution of seeds, that is, an aqueous solution of calcium salt and an aqueous solution of carbonate or hydrogen carbonate are mixed, insoluble calcium carbonate (CaCO ₃ ) is precipitated, and sodium chloride (NaCl) is further produced as a by-product precipitate. . Note that this sodium chloride (NaCl) is water-soluble and does not contribute to the decrease in water permeability. Generally speaking, in the above technique (1), the by-product precipitate is water-soluble, and
Since the effect of bacteria in the ground cannot be expected, the effect of lowering the water permeability of the ground and the improvement of durability cannot be expected. Further, according to the embodiment of (1), the concentration of the first aqueous solution is 500 g of calcium chloride (CaCl ₂ ) mixed per liter, and the concentration of the second aqueous solution is sodium carbonate (Na ₂ CO _{2). 3} ) was mixed in an amount of 80 g per 0.92 liter, and each was a combination of relatively high-concentration aqueous solutions. That is, since the two types of aqueous solutions have relatively high concentrations, a large amount of injection material is required, resulting in high cost. Therefore, there is a concern that hardness of groundwater and salt concentration may increase.

Next, the "ground injection method" disclosed in the above (2) is intended for water stopping of so-called running ground, and is a fiber dispersion aqueous solution in which water-swellable fibers are dispersed in water as an injection material. Therefore, it is not applicable to sand ground or gravel ground with good water permeability instead of running ground. That is, because of the presence of the water-swellable fiber, the injection diameter into the ground is limited to a small value. Therefore, when constructing a water blocking layer over a wide area, many injection pipes (boring holes) must be installed at narrow intervals, which requires much labor and cost for construction.

The object of the present invention is to inject fine and water into the ground by injecting into the ground two or more kinds of aqueous solutions which easily permeate into the sand or the gravel ground simultaneously or separately and reacting in the ground. It is an object of the present invention to provide a method of generating a sparingly soluble precipitate to reduce the water permeability of the ground.

[0009]

As a means for solving the above-mentioned problems of the prior art, a method for lowering the water permeability of the ground according to the invention as set forth in claim 1 is such that it can be easily carried into a sand ground or a gravel ground. By injecting into the ground two or more kinds of permeating aqueous solutions, that is, an aqueous solution containing +2 or +3 valent iron ions and an aqueous solution that oxidizes them, the ground is mixed and reacted in the ground to react. It is characterized in that a fine and hardly water-soluble precipitate is generated therein.

According to the second aspect of the present invention, two types of aqueous solutions of ferrous sulfate aqueous solution (dissolved iron) and potassium permanganate aqueous solution (oxidizing agent) are infiltrated into the sand ground or gravel ground, and the two liquids are ground. It is characterized in that iron hydroxide, which is hardly soluble in water, is deposited in the ground by mixing and reacting in the ground.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the method for reducing the water permeability of the ground according to the present invention will be described below. The gist of the present invention is to provide two or more kinds of aqueous solutions that easily penetrate into the sand ground or gravel ground, for example, an aqueous solution containing +2 or +3 iron ions and an aqueous solution for oxidizing the same in the ground or separately. It is a method of decreasing the water permeability of the ground by injecting into the ground, mixing and reacting in the ground to generate fine and sparingly water-soluble precipitates (iron hydroxide) in the ground (claim 1). invention).

More specifically, two kinds of aqueous solutions of ferrous sulfate aqueous solution (dissolved iron) and potassium permanganate aqueous solution (oxidizing agent) are permeated into the sand ground or gravel ground, and the two liquids are ground in the ground. This is a method of precipitating poorly soluble iron hydroxide in water in the ground by mixing and reacting to lower the water permeability of the ground (the invention according to claim 2).

As an example, FIG. 1 shows an embodiment of a method for reducing the water permeability of the ground. The injection pipe 3A and the pumping pipe 3B are installed in the ground at intervals L. Injecting the first aqueous solution X (for example, the above ferrous sulfate aqueous solution) and the second aqueous solution Y (for example, the above potassium permanganate aqueous solution) from the injection pipe 3A, while pumping water from the pumping pipe 3B. Creates a local hydraulic gradient in the groundwater in the ground,
Promotes the penetration and mixing of the two aqueous solutions. Incidentally, in FIG. 1, the permeation flow y of the second aqueous solution Y having a large specific gravity is injected in the upper layer, and the permeation flow x of the first aqueous solution X having a small specific gravity is injected in the lower layer at the same time to mix them in the boundary region of both aqueous solutions. The case where the accompanying reaction region 5 is formed is shown.

Generally, the water permeability of sand or gravel ground depends on the content of fine particles in the ground. Focusing on this point, the present invention is based on the idea of artificially generating fine particles (fine particles having a diameter) in the ground to reduce the water permeability.

In the present invention, +2 or +3 iron
As an aqueous solution containing ON, ferrous sulfate (FeSO 4_Four)
An aqueous solution can be used, which is oxidized to form iron hydroxide (Fe (O
H) _Two, Or Fe (OH)_Three) As an aqueous solution for precipitation
For potassium permanganate (KMnO_Four) The aqueous solution
It can be preferably used in view of the large amount of precipitation.

The above-mentioned potassium permanganate (KMn)
O ₄ ) produces sparingly water-soluble manganese dioxide (MnO ₂ ) as a by-product precipitate in the ground. This manganese dioxide (MnO ₂ ) has a property of being poorly water-soluble and contributes to the reduction of the water permeability of the ground.

As the oxidizing agent, in addition to potassium permanganate (KMnO ₄ ), an ozone aqueous solution, hydrogen peroxide, a magnesium peroxide aqueous solution, saturated dissolved oxygen water (aerated water), galionella or leptothlix is used. Similarly, by using water containing iron bacteria, it is possible to deposit the hardly soluble iron hydroxide as a by-product deposit.

By the above-mentioned reaction action, iron bacteria existing in the groundwater in the natural world are propagated to form viscous iron colloids and iron flocs based on iron hydroxide, which further promotes the decrease of the permeability of the ground. You can expect an effect.

In the case of the present invention, the oxidizing agent for precipitating iron hydroxide may be used not only in one kind but also in combination of two or more kinds. Further, when an aqueous solution having the same concentration is infiltrated into the ground, it is possible to deposit a larger amount of iron hydroxide in a short time by raising the temperature of the aqueous solution.

In the present invention, the two kinds of aqueous solutions to be infiltrated into the ground are shown in FIG. 1 and injected in parallel at the same time as described above, or separately injected at the same depth with a time difference. It is feasible. Whichever it is, 2
It is possible to lower the water permeability of the ground by infiltrating the liquid into the ground, mixing and reacting in the ground. In the case of simultaneous and parallel injection, the permeation radius depends only on the hydraulic conductivity of the original ground and reaches about 50 m. When injected separately, the decrease in hydraulic conductivity when mixing the two liquids,
It depends on the hydraulic conductivity at the time of the final drop. When the hydraulic conductivity changes in 3 hours, the permeation coefficient is about 6 m. In the case of separately permeating into the ground, the order of which kind of aqueous solution is permeated first does not matter.

Since the aqueous solution used in the method of the present invention has a composition that easily penetrates into the sand or gravel ground, the injection diameter (penetration radius) into the ground is sufficiently large as described above.
When constructing the water blocking layer in a wide range, it is sufficient to install the injection pipes (boring holes) at sufficiently large intervals (for example, 6 m to 50 m), and the construction cost can be reduced. Also,
The material used is composed of elements (Fe, K, Mn, etc.) that are contained in the soil or groundwater to a large extent, and the adverse effect on soil and groundwater pollution can be controlled by changing the concentration of the aqueous solution. Therefore, it has almost no impact on the surrounding groundwater environment. For example, ferrous sulfate in a small amount is not harmful as it is recognized as a food additive. When the concentration of potassium permanganate is 0.1 to 0.2%, it is not harmful as used in mouthwashes and the like. Further, both ferrous sulfate and potassium permanganate have almost the same viscosity as that of water.

[0022]

[Examples and results of water permeability test] The concentration of the ferrous sulfate aqueous solution was 5 g per liter and 0.
5g and 5g were prepared, and the concentration of the potassium permanganate aqueous solution was set to 0.1g per liter, and this was added to Toyoura standard sand (permeability was 2.3 x ^10-2 cm / sec).
It was permeated alternately every minute and a test for confirming a decrease in water permeability was conducted. The water permeability test is a constant water level water permeability test (JIS A1218).
It carried out according to. The test results are shown in FIGS. 2 and 3.

First, FIG. 2 shows that the concentration of the ferrous sulfate aqueous solution is 1
The test results are shown when the concentration of the aqueous solution of potassium permanganate is 5 g per liter and the concentration of the aqueous potassium permanganate solution is 0.1 g per liter. It was confirmed that the hydraulic conductivity of Toyoura standard sand decreased to about 1/21 in about 120 minutes.

FIG. 3 shows the test results when the concentration of the ferrous sulfate aqueous solution was 0.5 g per liter and the concentration of the potassium permanganate aqueous solution was 0.1 g per liter as in the previous example. . It was confirmed that the hydraulic conductivity of Toyoura standard sand was reduced to about 1/15 in about 180 minutes.

The above results show that the method of the present invention has the effect of lowering the water permeability of the ground in a short period of time with the combination of very low concentration aqueous solutions.

[0026]

Effects of the Invention The method for lowering the water permeability of the ground according to the first and second aspects of the invention has the following effects. 1. Since at least two kinds of aqueous solutions having the same specific gravity and viscosity as water are permeated into the ground, the injection diameter is large and the installation intervals of the injection holes (boring holes) can be increased. Therefore,
It is extremely useful for constructing a wide range of impaired water permeability (stopping water). 2. Since the concentration of the aqueous solution to be permeated can be controlled, adverse effects on ground soil and groundwater pollution can be controlled, and there is almost no effect on the surrounding groundwater environment. 3. Reduce the water discharge (spring water flow) due to underground construction by reducing the water permeability of the ground directly below the root cutting bottom of the area surrounded by the impermeable walls, and Reduction (implementation of groundwater level lowering method) is possible. 4. If there is a defect such as groundwater leakage in the impermeable wall, artificial impermeable layer, etc., even if the location of the defect cannot be specified specifically, the two aqueous solutions will not be permeable. Good and the injection diameter is large enough to easily repair the water stoppage in the defective area by using the flow of groundwater.

[Brief description of drawings]

FIG. 1 is a sectional view conceptually showing an embodiment of a method for reducing water permeability of the present invention.

FIG. 2 Concentration of ferrous sulfate aqueous solution is 5 per liter.
9 is a graph showing the result of a water permeability test when the concentration of the potassium permanganate aqueous solution is 0.1 g per 1 liter.

FIG. 3 is a graph showing the results of a water permeability test when the concentration of ferrous sulfate aqueous solution is 0.5 g per liter and the concentration of potassium permanganate aqueous solution is 0.1 g per liter.

[Explanation on the sign]

3A injection tube 3B pumping pipe X First aqueous solution Y second aqueous solution 5 reaction area L interval

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshio Hirai             Chiba Prefecture Inzai City 1-5 Otsuka 1 Stock Association             Takenaka Corporation Technical Research Institute (72) Inventor Masaji Aoki             Chiba Prefecture Inzai City 1-5 Otsuka 1 Stock Association             Takenaka Corporation Technical Research Institute (72) Inventor Nobuyasu Okuda             Chiba Prefecture Inzai City 1-5 Otsuka 1 Stock Association             Takenaka Corporation Technical Research Institute (72) Inventor Kunimitsu Mori             Chiba Prefecture Inzai City 1-5 Otsuka 1 Stock Association             Takenaka Corporation Technical Research Institute F-term (reference) 2D040 AA04 AB01 AC02 AC03 CA10                       CB03 DB01 DC00                 4H026 CA06 CB01 CB07 CC04

Claims (2)

[Claims] 1. It easily penetrates into sand or gravel ground.
At least one kind of aqueous solution, that is, an aqueous solution containing +2 or +3 iron ions and an aqueous solution that oxidizes it are simultaneously or separately injected into the ground, and mixed and reacted in the ground to make fine particles in the ground. A method for decreasing the water permeability of the ground, characterized in that a hardly soluble precipitate is generated in water. 2. A ferrous sulfate aqueous solution (dissolved iron) and a potassium permanganate aqueous solution (oxidizing agent) are infiltrated into the sand ground or gravel ground, and the two liquids are mixed and reacted in the ground. A method of decreasing the water permeability of the ground, which comprises depositing a sparingly soluble iron hydroxide in the ground.