JP2020200681A - Lowering method of ground water cut-off property - Google Patents

Abstract

To provide a lowering method of water cut-off property capable of lowering water cut-off property in a water cut-off region formed in a ground.SOLUTION: With a water cut-off region 5A which is solidified by utilizing an oxidation-reduction reaction in a ground 5 to have improved water cut-off property as an object, a chemical specie whose positive/negative of an oxidation-reduction potential is opposite to positive/negative of an oxidation-reduction potential of the water cut-off region 5A is made to be in contact with the water cut-off region 5A. By decomposing to dissolve an object contributing to solidification of the ground 5, a densified ground returns to a state before the solidification.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for lowering the water stopping property of the ground.

Conventionally, a chemical solution has been injected into the ground in order to improve the water stopping property of the ground. As a method of reducing the permeability of the ground (that is, improving the water stopping property) by expelling and solidifying the water existing in the gaps of the ground by the injection material as a chemical solution, for example, water glass is used as the main material and a curing agent is used. And those that add auxiliaries are known. Further, a method is known in which iron ions and an oxidizing agent are mixed and reacted in the ground to generate a sparingly soluble precipitate in the ground to improve water stopping property (see, for example, Patent Document 1).

Japanese Patent No. 360892

At present, the ground with improved water stopping property is left untreated without any special treatment after its use. However, if the water blocking area continues, the groundwater levels will be different from each other on both sides, so it may be desirable to restore the original state with respect to water stopping.

Therefore, an object of the present invention is to provide a method for reducing water stoppage, which can reduce the water stoppage of a water stoppage region formed in the ground.

The present invention targets a water-stopping region that is solidified by utilizing an oxidation-reduction reaction in the ground and has improved water-stopping properties, and the positive and negative of the redox potential is opposite to the positive and negative of the redox potential of the water-stopping region. Provided is a method for reducing the water-stopping property of the ground by bringing the seed into contact with the water-stopping area.

In this method, since a chemical species having an oxidation-reduction potential opposite to the oxidation-reduction potential of the still water region is used, the substance contributing to the solidification of the ground can be decomposed and dissolved by the redox reaction. .. As a result, the densified ground can be restored to the state before solidification, and the water stopping property of the water stopping area can be lowered.

In this method, the water blocking region can be one in which the water stopping property is improved by the formation of sulfide minerals, in which case the chemical species can be an oxidizing agent. This example is an example in which the redox potential of the still water region is negative and the redox potential of the chemical species is positive. At this time, the oxidizing agent is preferably oxygen or hydrogen peroxide, and is preferably brought into contact with the water blocking region as an aqueous solution having a dissolved oxygen concentration of 8 mg / L or more.

In the method of the present invention, it is preferable to inject the chemical species into the still water region. In this case, since the chemical species comes into direct contact with the water blocking region, the efficiency of redox reaction is high.

In the method of the present invention, it is preferable to provide a well on the downstream side of the groundwater with respect to the water stop region and confirm that the water stoppage of the water stop region is lowered. Further, a well may be provided on the upstream side of the groundwater with respect to the water stop region, and the chemical species may be injected from the well.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for lowering the water stopping property of a water stopping area formed in the ground.

It is a figure which shows the water stop system. It is a figure which shows the water-stopping reduction system of one Embodiment of this invention. It is a figure which shows the modification of the water-stopping reduction system of one Embodiment of this invention. It is a figure of the apparatus which carries out the water-stopping improvement test. It is a figure of the apparatus which carries out the water-stopping reduction test. It is a graph which shows the change of the hydraulic conductivity ratio in the water-stopping improvement test and the water-stopping lowering test.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same parts or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

The present invention is a method for reducing the water-stopping property of a water-stopping region that has been solidified by utilizing an oxidation-reduction reaction in the ground to improve the water-stopping property. By performing the redox reaction in the direction of canceling the redox reaction that occurred when improving the water stopping property, the ground returns to the state before solidification and the water stopping property is lowered. In this method, a chemical species having a negative redox potential is used when the redox potential of the water-stopping region is positive, and conversely, a positive redox potential is used when the redox potential of the water-stopping region is negative. Use a chemical species that has. In the embodiment shown below, a case where the redox potential of the water-stopping region is negative and the redox potential of the chemical species is positive will be described as an example.

First, a method for improving the water-stopping property of the ground will be described, and then a method for reducing the water-stopping property of the ground will be described.

<Method of improving water stopping of the ground>
(Water stop system)
In order to improve the water stopping property of the ground, the water stopping system 1 shown in FIG. 1 is used. The water stop system 1 is provided in and on the ground 5 to be stopped, and includes a plurality of adjacent wells 3 and a drug injection pump 15 installed on the ground.

The well 3 is formed by inserting a strainer 4 having a slit or a through hole in the wall surface through a boring hole 2 that excavates the ground 5 that is an aquifer and reaches the impermeable layer 17. In the water stop system 1, the groundwater existing in the ground 5 may or may not flow. Inside each well 3, the diameter of the strainer 4 is smaller than the diameter of the boring hole 2, and the space created as the difference in diameter is filled with sand 7.

In the space filled with sand 7, bentonite 9 as a water-shielding material is filled in place of sand 7 at a height position of about half the depth of the well 3. A water pump 11 is installed at a height position in the well where the bentonite 9 is filled. The water supply pump 11 can control the water supply direction up and down, and the flow rate of the water supply pump 11 is, for example, 10 to 100 L / min. Of the wells 3 in which a plurality of wells are arranged, one well 3a has a water supply direction upward, and the other well 3b has a water supply direction downward.

The bentonite 9 and the water supply pump 11 restrict the vertical movement of groundwater inside the well 3, and the inside of the well 3 is divided into an upper region 31 and a lower region 32 in the depth direction. Here, in order to ensure water shielding between the upper region 31 and the lower region 32, a packer (not shown) may be packed around the water supply pump 11 installed. The packer is an annular balloon with a hole in the center, and when it inflates, it comes into close contact with the inner peripheral wall of the water pump 11 and the well 3, so that the water shield between the upper region 31 and the lower region 32 in the well 3 Can be raised.

Each well 3 is provided with an instrument (not shown) capable of measuring the sulfate ion concentration and total organic carbon (TOC) concentration of groundwater, and the water level and flow velocity in each well 3.

A drug injection pump 15 is installed on the ground. A pipe 13a extends from the drug injection pump 15 toward each well 3, and the end of the pipe 13a reaches the inside of each well 3.

Through the drug injection pump 15, the first chemical species (excluding strong acids) that generate sulfate ions in water and the anaerobic bioagent are added into the well 3. Here, the anaerobic bioagent activates the microorganisms that inhabit the ground 5.

Specific examples of the "first chemical species (excluding strong acids) that generate sulfate ions in water" include sulfates. That is, ionized underground water is a chemical species that produce sulfate ion (SO 4 ^_2-), sodium sulfate, potassium sulfate, ferrous, ferric sulfate, magnesium sulfate, and aluminum sulfate and the like. These may be hydrates.

As the anaerobic bioagent, one having a high immediate effect may be selected, or one having a low immediate effect but a long duration may be selected. Specific examples of the former anaerobic bioagent include those containing one or more components such as lactic acid, glucose, ethanol, glycerol, acetic acid, butyric acid, propionic acid, formic acid, sorbitol, oligolactic acid, and shoe cloth. Be done. Examples of the latter anaerobic bioagent have a higher molecular weight than the former anaerobic bioagent, and specific examples thereof include one or more components such as polylactic acid, vegetable oil, emulsion oil, and higher fatty acid. Things can be mentioned. Here, the latter "sustained" of the anaerobic bioagent means that the onset of effect per fixed amount continues slowly for a long time even among the anaerobic bioagents. In this embodiment, it is preferable to use an anaerobic bioagent having a high immediate effect.

The first chemical species that produces sulfate ions in water and the anaerobic bioagent are each mixed with water and injected into the well 3 using a drug injection pump 15 at the time of use.

(Circulation flow formation process)
Hereinafter, the procedure of the method for improving the water stopping property of the ground using the water stopping system 1 will be shown. First, the water supply pump 11 in each well 3 is driven. At this time, the water supply direction is upward in one well 3a, and the water supply direction is downward in the other wells 3b adjacent to the well 3a (white arrows A and B in FIG. 1). Then, in the ground 5 between the adjacent wells 3a and 3b, the groundwater that connects the upper regions 31 and 31 and the lower regions 32 and 32 moves, and the direction of the movement is between the upper regions 31 and 31 and the lower region. The directions are opposite between the regions 32 and 32 (white arrows C and D in FIG. 1). As a result, the groundwater moves so as to circulate between the adjacent wells 3a and 3b. Further, each well 3 also has a flow of short-circuiting the upper region 31 and the lower region 32 (white arrow E in FIG. 1).

(First diffusion step)
The drug injection pump 15 is driven, and a first chemical species (hereinafter, simply referred to as “first chemical species”) that produces sulfate ions in water is added from at least one of the adjacent wells 3a and 3b. To do. Here, the amount of the first chemical species added is such that the concentration in the ground 5 is 0.001 to 1% by weight as the sulfur content with respect to the dry weight of the ground 5. The concentration can be calculated from an estimate of the total volume of the ground 5 to be reformed, the weight of the first chemical species to be added, and the weight of sulfur atoms in the first chemical species.

The addition amount may be 0.01 to 1% by weight, 0.001 to 0.1% by weight, 0.01 to 0.1% by weight, or 0. It may be 05 to 1% by weight, or 0.05 to 0.1% by weight. The lower limits of these numerical ranges are 0.02% by mass, 0.03% by mass, 0.04% by mass, 0.06% by mass, 0.07% by mass, 0.08% by mass, and 0.092% by mass. May be adopted. The upper limits of these numerical ranges are 0.2% by weight, 0.3% by weight, 0.4% by weight, 0.5% by weight, 0.6% by weight, 0.7% by weight, and 0.8% by weight. , 0.9% by weight may be adopted.

The added first chemical species is ionized in groundwater to generate sulfate ions, and diffuses into the ground 5 by riding on the circulation of groundwater formed by the action of the water supply pump 11. The water supply pump 11 is continuously driven so that the sulfate ions are sufficiently diffused in the ground 5.

(First measurement step)
A first measurement step is performed in parallel with the first diffusion step. That is, immediately after the addition of the first chemical species or after a lapse of a predetermined time, groundwater is collected from the well 3 and the concentration of sulfate ions is measured. At this time, in order to confirm that the sulfate ions are sufficiently diffused, it is preferable to measure the groundwater in the well on the opposite side of the well to which the first chemical species is added. As a result of the measurement, when the concentration of sulfate ion is a predetermined value, for example, the concentration of sulfate ion at the point where the first chemical species is added is 0.1% by weight, the concentration of sulfate ion in the groundwater in the well on the opposite side. When it reaches 0.1% by weight, the addition of the first chemical species, that is, the first diffusion step is completed. If it does not reach 0.1% by weight, the first chemical species is added again. Here, it is preferable to maintain the concentration of sulfate ions in the ground 5 at 0.001 to 1% by weight.

(Second diffusion step)
After completing the first diffusion step and the first measurement step, the anaerobic bioagent is added from at least one of the adjacent wells 3a and 3b. The amount of the anaerobic bioagent added is such that the amount adsorbed on the ground 5 is 0.3 to 3.0 kg / m ³ . The relationship between the addition amount and the adsorption amount can be determined in advance by a test using the excavated soil generated when the well 3 is installed, and can be set to, for example, 5 to 50 mg per 1 L of groundwater.

The added anaerobic bioagent rides on the circulation of groundwater formed by the action of the water supply pump 11 and diffuses into the ground 5. The water pump 11 is continuously driven so that the anaerobic bioagent is sufficiently diffused into the ground 5.

The added anaerobic bioagent activates the microorganisms in the ground 5, and the microorganisms reduce the sulfate ions originally contained in the ground 5 or the sulfate ions generated by the ionization of sulfate in the ground water to reduce the sulfate ions generated, and the hydrogen sulfide ion HS. ^- (Furthermore, sulfide ion S ^2- ) is changed. Hydrogen sulfide ions (and sulfide ions) further become sulfide minerals (for example, iron sulfide generated by reacting with iron ions existing in the ground 5) and precipitate. As a result, the ground 5 between the wells 3a and 3b is densified, and the water stopping property of the ground 5 is improved. At the same time, the redox potential of the ground 5 decreases and becomes a negative value. The region where the water stopping property is improved is referred to as a water stopping area 5A (see FIG. 2).

(Second measurement step)
A second measurement step is performed in parallel with the second diffusion step. That is, at the same time as adding the anaerobic bioagent, the sulfate ion concentration of the groundwater, the total organic carbon concentration, and the water level and the flow velocity in the wells 3a and 3b are measured. This measurement will continue thereafter. Here, since the total organic carbon concentration decreases as the activity of the microorganism is activated and the activity is increased, the anaerobic bioagent is used when the total organic carbon concentration is reduced to a predetermined value or less in order to maintain the activity of the microorganism. Is preferably added additionally. On the contrary, when the concentration of the anaerobic bioagent reaches a predetermined value, the addition of the anaerobic bioagent is stopped. Further, by measuring the water level and the flow velocity in the wells 3a and 3b, it is possible to confirm the degree of improvement in the water stopping property of the ground 5. In particular, the degree of improvement in water stopping property can be confirmed from the relationship between the water level difference in both wells 3a and 3b and the flow velocity in both wells 3a and 3b.

Here, the total organic carbon concentration is preferably maintained in the range of 100 to 1000 mg / L, and more preferably maintained in the range of 100 to 600 mg / L. If it exceeds 1000 mg / L, the pH tends to decrease and the environment tends to be less prone to microbial activity, while if it is less than 100 mg / L, the microbial activity tends to be less likely to occur.

When the concentration of sulfate ions drops to a predetermined value, for example, 0% by weight, and when it is estimated that the degree of improvement in water stopping property has reached a desired degree, the drive of the water supply pump 11 is stopped. Stop the circulation of groundwater. That is, the second diffusion step is completed. On the other hand, if the concentration of sulfate ions has not decreased below a predetermined value, or if it is estimated that the degree of improvement in water stopping property has not reached a desired value, the water supply pump 11 is continuously driven and the first Additional additions of chemical species and anaerobic biologics may be made.

(Water permeability test)
After completing the above procedure, for example, an in-situ water permeability test is performed to confirm the degree of water stoppage. For example, water is pumped from the well 3a to lower the groundwater level. From there, time is measured to measure the time course of water level recovery. The time course of the obtained water level recovery is shown in a graph (horizontal axis: time, vertical axis: water level recovery amount), and the hydraulic conductivity is calculated from the slope of the water level change obtained from the graph. The water stopping performance is confirmed by comparing the water permeability tests before and after the use of the water stopping system 1.

(effect)
In this method for improving water stoppage using the water stoppage system 1, since a circulating flow of groundwater is generated between the wells 3a and 3b, the first chemical species and anaerobic bioagent added to the groundwater in the wells 3a and 3b Can be efficiently diffused into the ground 5. Since the reaction rate of the reduction reaction involving microorganisms is slower than that of the reaction involving only the compound, it is concentrated near the wells 3a and 3b where the first chemical species and the anaerobic bioagent are injected. The first chemical species and the anaerobic bioagent are likely to spread over a wide area in the ground 5. Therefore, the ground can be uniformly and sufficiently reformed to the target reforming range.

Further, if the anaerobic bioagent is first diffused into the ground 5, sulfate ions will infiltrate into the place where the microorganisms in the ground 5 are activated by the anaerobic bioagent, and the well 3a, It is conceivable that the peripheral region of 3b may be particularly concentrated and the reaction may occur. On the other hand, in the present embodiment, since the first chemical species is added first, sulfate ions can infiltrate into the ground when the activation of microorganisms is not sufficient, and therefore the homogeneity of ground modification is improved. improves. The first chemical species and anaerobic bioagent used in the present embodiment have an advantage of having a small environmental load.

<Method of reducing water stopping of the ground>
The method for lowering the water-stopping property of the ground of the present embodiment uses the water-stopping water-stopping system 100A shown in FIG. The water stoppage lowering system 100A includes a plurality of wells 3 and 3 used in the above water stoppage improvement method, and a high-concentration oxygen water generator 16 installed on the ground. A pipe 13b extends from the high-concentration oxygen water generator 16 toward each well 3, and the end of the pipe 13b reaches the inside of each well 3. In FIG. 2, the ground 5 has a water-stopping region 5A formed by the above-mentioned water-stopping improving method, whereby the water-stopping region 5A flows on the upstream side of the groundwater flowing in the direction orthogonal to the extending direction. Is strong (white arrow F), and the flow is weak on the downstream side (white arrow G). Further, the water stoppage lowering system 100A is provided with a downstream well 30a on the downstream side (left side in the drawing) of groundwater and an upstream well 30b on the upstream side (right side in the drawing) with respect to the water stoppage region 5A.

High-concentration oxygen water is injected into the well 3 from the high-concentration oxygen water generator 16 using a pump in the same manner as in the circulation flow forming step and the first diffusion step in the above water-stopping improvement method, and the water-stopping region Diffuse and circulate within 5A. The high-concentration oxygen water is preferably ultrafine bubble water or microbubble water containing microbubbles of oxygen. Further, the dissolved oxygen (DO) concentration of the high-concentration oxygenated water is preferably 8 mg / L or more, more preferably 20 mg / L or more, further preferably 25 mg / L or more, and 30 mg / L or more. It is particularly preferable that it is L or more. Here, the measurement of the DO concentration can be performed using, for example, a fluorescent dissolved oxygen meter. In the scene where high-concentration oxygen water is injected into the well 3 and the scene where the DO concentration of high-concentration oxygen water is measured, oxygen does not necessarily have to be dissolved in water, and when it contains fine bubbles of oxygen. Is the value when measured in that state as the DO concentration value.

The high-concentration oxygenated water to be injected has a positive redox potential, and is preferably about +100 to +500 mV. The oxidation-reduction potential here is a value measured using a platinum electrode and a comparative electrode (silver / silver chloride electrode) or a composite electrode.

Here, high-concentration oxygenated water is used to diffuse and circulate in the water-stopping region 5A, but any oxidant that has a positive redox potential and can oxidize the inside of the ground. , Other chemical species may be used. Other oxidants that have a positive redox potential and can oxidize the inside of the ground (hereinafter simply referred to as "second chemical species") include, for example, hydrogen peroxide. Examples include ozone, sodium peracetate, and sodium percarbonate. When hydrogen peroxide is added, it is preferably used as a hydrogen peroxide solution, and the amount thereof is preferably in the above range when converted to the DO concentration. The second chemical species is preferably a chemical species containing an oxygen atom. When injecting the oxidizing agent, it is preferable to inject it as an aqueous solution.

When the high-concentration oxygenated water comes into contact with the water-stopping region 5A, the redox reaction proceeds, the precipitate of the sulfide mineral formed by the above-mentioned water-stopping improving method is dissolved, and the sulfate ion is liberated. As a result, the densified ground returns to the state before solidification, and the water stopping property of the water stopping area 5A is lowered. At the same time, the liberated sulfate ions move downstream along with the flow of groundwater.

Along with the injection of high-concentration oxygenated water, the sulfate ion concentration is monitored in the downstream well 30a. When the sulfate ion concentration becomes high (for example, 500 mg / L or more), groundwater is pumped from the downstream well 30a to recover the sulfate ion. If the sulfate ion concentration is still detected at a high concentration even after this pumping, the diffusion of sulfate ions in the ground 5 can be prevented by pumping groundwater even in the well 3.

Whether or not the water stopping property of the water stopping area 5A has decreased can be confirmed by performing an in-situ water permeability test using the downstream well 30a and the upstream well 30b. In addition, it can be confirmed that the water stoppage has decreased by confirming that the amount of circulating water has returned to the state before the water stoppage improvement between the plurality of wells 3 and 3. These tests allow detailed assessment of the restoration of water stopping properties and increase the reliability of the results.

In this method for reducing water stoppage, when it is considered that the amount of circulating water is extremely small and the diffusion and permeation of high-concentration oxygen water is slow, as in the water stoppage reduction system 100B shown in FIG. 3, between a plurality of wells 3 and 3. A new injection well 40 may be provided in the water stop region 5A of the above, and high-concentration oxygen water may be injected there as well. Thereby, the supply of oxygen to the water stop region 5A can be promoted.

In addition, high-concentration oxygen water may be injected into the upstream well 30b. In this case, oxygen is supplied from a direction different from the circulating flow in the water stop region 5A, and the dissolution efficiency of the sulfide mineral can be improved.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. In the above embodiment, the case where the redox potential of the water-stopping region is negative and the redox potential of the chemical species is positive has been described as an example, but it is carried out in a situation where the relationship between the redox potentials is reversed. You can also. For example, in a method for improving water-stopping, ferrous sulfate or ferric sulfate (and its hydrate is also acceptable) and oxygenated water are used to solidify the ground to make the redox potential of the water-stopping region positive, and then In the method for lowering the water stopping property, instead of adding an oxidizing agent such as oxygen or hydrogen peroxide, reduced water such as hydrogen water or an anaerobic bioagent may be added.

Since the present invention is a water-stopping reduction method for a water-stopping region that is solidified by utilizing an oxidation-reduction reaction in the ground and has improved water-stopping properties, for example, a ground solidified using water glass as a main material or , Ground solidified using cement-based solidifying material is not included.

Hereinafter, the contents of the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples.

(Water stoppage improvement test)
As shown in FIG. 4, a glass column 51 having a length of 10 cm and an inner diameter of 3 cm was prepared, and 146.24 g of raw soil S containing microorganisms was filled therein. 0.15% by mass of sodium sulfate decahydrate as a chemical species that produces sulfate ions (% by mass as sulfur content with respect to the dry weight of the raw soil), and nutrient salt as an anaerobic bioagent (total organic carbon content in 1 g) 900 mg (the amount required to adjust the total organic carbon amount to 100 mg / L) of 0.37 g). If it greatly exceeds 100 mg / L, the pH is lowered and microbial activity is unlikely to occur. An aqueous solution 52a in which microbial activity is not generated when the amount is significantly lower than 100 mg / L) is prepared, and the hydraulic gradient is 0.5 with respect to the glass column 51 filled with the raw soil S. And passed water. The driving force for this water flow depends on the difference in water level from the aqueous solution 52b stored on the leaching side. The aqueous solution 52b stored on the leaching side was returned to the original aqueous solution 52a side by the pump 53 at a flow rate of 1 mL / min. With this configuration, water was circulated for 60 days. The hydraulic conductivity (k) was determined from the amount of water passed, the water flow time, the hydraulic gradient, and the cross-sectional area of the glass column at each time point for 60 days. For 60 days, the redox potential was in the range of 0-300 mV.

(Water stoppage reduction test)
Then, as shown in FIG. 5, high-concentration oxygen water (microbubble water, DO concentration = 30 mg / L) 54 was passed through the glass column subjected to the above water-stopping improvement test. The running water gradient at the start was 0.5, and water was passed for 40 days. The high-concentration oxygenated water 54 through which water was passed was not recycled and was stored in the liquid reservoir 55. The hydraulic conductivity (k) was determined from the amount of water passed, the water flow time, the hydraulic gradient, and the cross-sectional area of the glass column at each time point for 40 days.

The results of the water-stopping improvement test and the water-stopping lowering test are also shown in the graph of FIG. In this graph, the hydraulic conductivity (k ₀ ) before the start of the water stopping property improvement test is set to 1, and the ratio of the hydraulic conductivity to this at each measurement time point (permeability coefficient ratio) is used as an index of hydraulic conductivity. The elapsed time shows the hydraulic conductivity ratio in the water-stopping improvement test up to 60 days, and then shows the hydraulic conductivity ratio in the water-stopping lowering test up to 100 days.

From the results shown in FIG. 6, it was found that an aqueous solution in which a chemical species that produces sulfate ions and an anaerobic bioagent are dissolved can be modified to enhance water stopping. It was also found that the raw soil whose water-stopping property was increased (water permeability was decreased) by that method was subsequently exposed to a high concentration of oxygen to restore the water-stopping property to the state before modification.

The present invention can be used when it is desired to restore the ground once solidified and improved in water stopping property to the original state.

1 ... Water stop system, 2 ... Boring hole, 3 (3a, 3b) ... Well, 4 ... Strainer, 5 ... Ground, 7 ... Sand, 9 ... Bentnite, 11 ... Water pump, 13a, 13b ... Pipe, 15 ... Chemical Injection pump, 17 ... impervious layer, 30a ... downstream well, 30b ... upstream well, 31 ... upper region, 32 ... lower region, 40 ... injection well, 51 ... glass column, 52a, 52b ... aqueous solution, 53 ... Pump, 54 ... High concentration oxygenated water, 55 ... Liquid reservoir, 100A, 100B ... Water stoppage reduction system, S ... Raw soil.

Claims (6)

Targeting the water-stopping area that is solidified by utilizing the redox reaction in the ground and has improved water-stopping
A method for lowering the water-stopping property of the ground by bringing a chemical species whose redox potential is opposite to the positive / negative of the redox potential in the water-stopping region into contact with the water-stopping region. The water blocking region has improved water stopping due to the formation of sulfide minerals.
The method according to claim 1, wherein the chemical species is an oxidizing agent. The method according to claim 2, wherein the oxidizing agent is oxygen or hydrogen peroxide, and the aqueous solution having a dissolved oxygen concentration of 8 mg / L or more is brought into contact with the water-stopping region. The method according to any one of claims 1 to 3, wherein the chemical species is injected into the waterproof region. The method according to any one of claims 1 to 4, wherein a well is provided on the downstream side of the groundwater with respect to the water blocking area, and it is confirmed that the water stopping property of the water stopping area is lowered. The method according to any one of claims 1 to 5, wherein a well is provided on the upstream side of the groundwater with respect to the still area, and the chemical species is injected from the well.

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