JP2011167619A - Contaminated soil cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contaminated soil cleaning method for cleaning contaminated soil, at the same time, performing ground strengthening and, even after the ground strengthening, cleaning contaminated soil and contaminated ground water. <P>SOLUTION: The contaminated soil cleaning method is a method of cleaning soil by vertically disposing an underground pile 54a to the contaminated soil 50, and includes: a process of digging a pit 51 up to a depth where contaminated earth 52 exists; and a process of charging, in the pit 51, mixed material C for underground pile formation made by mixing discharge earth discharged by digging or earth B for underground formation prepared beforehand and an alkali activation persulfate as a cleaning agent A selected from among any of sodium persulfate, potassium persulfate and ammonium persulfate into the pit, and burying the pit 51 back, and after charging the mixed material C for underground pile formation into the pit 51, sodium hydroxide or potassium hydroxide is charged into the pit 51, and thus the cleaning is performed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a contaminated soil purification method capable of simultaneously purifying contaminated soil in the ground and strengthening the ground.

Conventionally, as a method for purifying contaminated soil, as shown in Patent Document 1, an aqueous peroxide, for example, Fenton reagent and potassium permanganate are mixed in the contaminated soil to cause an oxidation reaction, and organic chlorine is used as the contaminant. It is known to mineralize compound oils (petroleum hydrocarbons, polycyclic aromatic hydrocarbons, etc.), benzene, toluene, xylene, chlorinated ethylenes (trichloroethylene, tetrachloroethylene, dichloroethylene, etc.).
Specifically, the purification method utilizing the Fenton reaction by the Fenton reagent generates a hydroxyl radical by reacting a hydrogen peroxide solution with a divalent iron ion as a catalyst, and reacts with the organochlorine compound. It decomposes into carbon dioxide, water, chlorine ions and hydrogen ions, mineralizes it and purifies contaminated soil.

As shown in Patent Document 2 and Patent Document 3, for example, a purification method using the above reaction is to excavate a fistula to a formation where contaminated soil exists by using an earth drill or an auger machine, As an aqueous solution of peroxide, it is made mineral by reacting with pollutants and purifying the formation around the fistula, and then backfilling with the purified soil discharged during excavation. Is called.
In addition, it is known that contaminated soil is widely seen in soft ground that contains a lot of moisture, such as groundwater flowing nearby, due to the diffusion of contaminants in a wide range due to the movement of moisture contained in the formation. When using or reusing such soil, it is necessary to improve the soil in conjunction with the purification of soil contamination. Generally, underground piles are created in the stratum after purification of the contaminated soil. Is done.

However, when an aqueous peroxide as a cleaning agent is directly injected or injected into the fistula, the reaction rapidly proceeds locally immediately after the pollutant and peroxide are introduced, and the reacted substance is ejected. There is a risk of doing. In addition, since the stratum that performs the purification treatment contains a lot of water and the groundwater often flows in the vicinity, the purification agent reacts locally or does not sufficiently react with pollutants and is washed away into the groundwater. Therefore, there is a problem that the contaminated soil cannot be purified efficiently.
In addition, there is a method of removing contaminated soil from the strata where the contaminated soil exists, transporting it to a treatment facility and purifying it, and then backfilling it again with soil that has been purified, or excavating and transporting the contaminated soil, Since it is necessary to transport and backfill the soil that has been subjected to the purification treatment, the labor and cost for the purification of the contaminated soil become enormous and a long construction period is required, which is economically inefficient.

JP 2004-183310 A JP 2002-188137 A JP 2009-56356 A

  In order to solve the above-described problems, the present invention provides a method for purifying contaminated soil that purifies contaminated soil and simultaneously strengthens the ground, and enables purification of contaminated soil and contaminated groundwater even after the ground is strengthened.

As a first embodiment according to the present invention, a method for purifying soil by erecting underground piles in contaminated soil, a step of excavating a fistula to a depth where contaminated soil exists, and discharged by excavation An underground pile building mixed material in which discharged soil or previously prepared underground pile building soil and alkali-activated persulfate selected from sodium persulfate, potassium persulfate, and ammonium persulfate are mixed And a step of filling the borehole and filling the borehole, and after charging the underground pile building material into the borehole, sodium hydroxide or potassium hydroxide is put into the borehole. .
According to the present invention, by mixing alkali-activated persulfate as a purification agent for contaminated soil into the soil for discharging soil or underground pile construction, it is backfilled in the excavated borehole, and the underground pile is erected. The purification substance that purifies the soil exudes from the created underground pile, and it becomes possible to purify the contaminated soil existing around the underground pile. Furthermore, since the pollutant contained in the groundwater passing through the underground pile is purified, the contaminant can be purified over a long period of time even after the underground pile is installed.
In addition, if the cleaning agent is an alkali activated persulfate selected from sodium persulfate, potassium persulfate, and ammonium persulfate, the alkaline activated persulfate is normally solid and discharged. And mixing with the soil for underground construction, the mixing work becomes safe, and the mixing work can be done not only at the facility to purify the contaminated soil, but also at the site where the underground pile is created .
In addition, by introducing sodium hydroxide or potassium hydroxide as a catalyst for reacting alkali-activated persulfate and pollutants contained in the underground pile building mixture, reaction with pollutants can be chained. It becomes possible to carry out, and it can purify | clean efficiently.
As a second form according to the present invention, the step of refilling the fistula is to insert the underground pile forming mixed material into the casing penetrating into the fistula, and to add the underground pile forming mixed material to the inside of the casing. It was made into the form which the mixture material for underground pile construction was compacted in the fistula by the rotational force of a thrust screw.
According to the present invention, the underground pile forming mixed material is compacted in the borehole by the rotational force of the thrust screw, so that the underground pile forming mixed material forming the underground pile is compressed, and the strong underground It becomes possible to create a medium pile.
As a third aspect of the present invention, the alkali-activated persulfate is coated with a water-soluble polymer.
According to the present invention, the alkali-activated persulfate is coated with the water-soluble polymer, so that the alkali-activated persulfate does not immediately react with moisture in the ground. The alkali-activated persulfate can be gradually leached from the soil to allow the alkali-activated persulfate to permeate a wide range of contaminated soil.
As a fourth embodiment according to the present invention, sodium hydroxide or potassium hydroxide is charged and compaction of the underground pile forming mixture is alternately performed. It was made to reach the height where the contaminated soil exists in the hole.
According to the present invention, by introducing sodium hydroxide or potassium hydroxide and compacting the underground pile forming mixed material alternately, water is uniformly distributed to the ground pile forming mixed material to be compacted. It becomes possible to spread sodium oxide or potassium hydroxide.
As 5th form which concerns on this invention, sodium hydroxide or potassium hydroxide is thrown in after making the compacted underground pile formation mixed material reach the height where the contaminated soil exists in the borehole. did.
According to the present invention, the alkali-activated persulfate is gradually leached from the coating of the water-soluble polymer, and the alkali-activated persulfate is infiltrated into a wide area of the contaminated soil, and then sodium hydroxide or potassium hydroxide. Can be used to purify a wide range of contaminated soil.
As a sixth embodiment according to the present invention, the range of the height where the contaminated soil exists in the fistula is expanded by compaction.
According to the present invention, it is possible to increase the ratio of underground piles per unit area in the formation where the contaminated soil exists by expanding the range of the height where the contaminated soil exists in the fistula, A wider range of purification is possible.
As a seventh embodiment according to the present invention, in the case where a plurality of underground piles are erected in the contaminated soil, the hole diameter of the fistula is a hole diameter that the fistulas after diameter expansion wraps when the contaminated soil is viewed in plan view. I tried to do it.
According to the present invention, since a plurality of underground piles erected on the contaminated soil overlap in a range where the contaminated soil exists, the proportion of underground piles per unit area in the stratum where the contaminated soil exists is further increased. A wider range of purification is possible.

Schematic which shows the contaminated soil improvement apparatus used for the contaminated soil purification method which concerns on this invention. The process drawing of the contaminated soil purification method which concerns on this invention. The process drawing of the contaminated soil purification method which concerns on this invention. The top view which shows the underground pile creation position which concerns on this invention. The process figure of the contaminated soil purification method of the other form which concerns on this invention. The top view which shows the underground pile creation position of the other form which concerns on this invention.

  Hereinafter, the present invention will be described in detail through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included in the invention. It is not necessarily essential to the solution, but includes a configuration that is selectively adopted.

Embodiment 1
Hereinafter, the purification method for contaminated soil of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a contaminated soil improvement device for purifying contaminated soil 50. In the figure, the contaminated soil improvement device includes a crane 1 used for ground improvement or the like. The crane 1 includes a crawler 2 that can be moved to an arbitrary work position, a horizontally-movable cart 3 that is mounted on the crawler 2, and a post 4 that is erected vertically above the front of the cart 3. The back stay 5 extends from the rear portion of the carriage 3 and is connected to the post upper portion 4a to support the post 4, and the winch 6 that winds and unwinds the wire 7. The wire 7 is hung on a pulley of a sheave portion 8 provided on the winch 6 and the post upper end portion 4b, and a casing auger machine 11 and a thrust screw auger machine 12 for excavating the contaminated soil 50 on the wire tip 7a. Is suspended.

As shown in FIG. 1, the casing auger machine 11 includes a hollow casing 14, a motor (not shown) that rotates the casing 14, and a hopper 15 that feeds the underground pile building mixture C described later. The casing 14 is installed substantially perpendicular to the ground surface of the contaminated soil 50 by being suspended by the wire 7.
The auger machine 12 for thrust screw is provided in the upper part of the auger machine 11 for casings, and includes a shaft 16 that penetrates the casing 14 in the extending direction and a motor (not shown) that rotationally drives the shaft 16. The shaft 16 has a through hole 18 penetrating in the extending direction of the shaft 16 inside, and an upper end portion of the through hole 18 is connected to the fluid supply means 20. The fluid supply means 20 is a device that discharges sodium hydroxide or potassium hydroxide as a catalyst D described later from the tip end portion 18 a of the through hole 18. The shaft 16 includes a thrust screw 17 on the outer peripheral surface on the contaminated soil 50 side, and is disposed at the center of the casing 14 so that the tip 17a of the thrust screw 17 and the tip of the casing 14 are substantially flush with each other.
When excavating the borehole 51 in the contaminated soil 50, the load is applied to the ground surface of the contaminated soil 50 by the weight of each auger machine 11 and 12, and the casing 14 is rotated by driving the motor outside the figure. Then, while discharging the soil from the outer surface of the casing 14 to the ground, the fistula 51 is formed up to the formation including the contaminated soil 52 in the contaminated soil 50. This will be specifically described below.

  First, as shown in FIGS. 2A and 2B, the fistula 51 is formed by penetrating the casing 14 while rotating the casing 14 until reaching the formation where the contaminated soil 52 exists in the contaminated soil 50. Specifically, the casing 14 is penetrated until the bottom 51a of the hole 51 reaches the deepest part of the formation where the contaminated soil 52 exists. Further, the soil including the contaminated soil 52 discharged when forming the fistula 51 is conveyed to a soil purification treatment facility (not shown) by, for example, a dump truck, and constitutes an underground pile building mixed material C described later. Used as underground pile.

Next, as shown in FIG. 2 (c), after the dredging hole 51 is formed to a predetermined depth, the underground pile forming mixed material C is put into the dredging hole 51 through the hopper 15 and below the casing 14. . The underground pile creation mixed material C is constituted by mixing the purification agent A and the underground development soil B, and as the purification agent A, sodium persulfate, potassium persulfate, ammonium persulfate, etc. Alkaline-activated persulfate is preferable, and as the soil B for underground construction, the discharged soil discharged when forming the borehole 51 or purified sand or crushed stone prepared separately from the discharged soil is mixed. The soil for building underground piles is adopted.
The purification agent A is an alkali-activated persulfate because the alkali-activated persulfate is a solid, for example, a powder as a normal state, so that it can be easily mixed with the underground soil B, and When it is backfilled in the fistula 51, it reacts with the water present in the contaminated soil 50 and liquefies, and the liquefied alkali-activated persulfate and the pollutant react gently so that it can be safely backfilled. It is because it can be performed.

Hereinafter, the underground pile creation mixed material C is prepared using sodium persulfate as the purification agent A, and the underground pile creation mixed material C is put into a range where the contaminated soil 52 in the borehole 51 exists. The chemical reaction will be described.
(1) Hydration reaction: Na ₂ S ₂ O ₈ (sodium persulfate) + H ₂ O → S ₂ O ₈ ² − + Na ² +
Due to this reaction, the powdered sodium persulfate reacts with moisture contained in the formation around the fistula 51 to form an aqueous solution, which becomes sulfate ions and sodium ions in the aqueous solution.
(2) By injecting sodium hydroxide or potassium hydroxide as an alkali activator into the aqueous solution as a reaction catalyst D with a pollutant, the reaction is promoted to show the following reaction.
S ₂ O ₈ ² − + Na ² + + OH− ↓
SO ₄ − · (sulfuric acid radical) + H ₂ O → HSO ₄ ² − + OH · (hydroxy radical)
In this reaction, the hydroxyl radical and the pollutant react in a chain reaction, so that the pollutant becomes RH → R ·.
RH indicates a pollutant and is made mineral by reacting with oil (petroleum hydrocarbon, polycyclic aromatic hydrocarbon), benzene, toluene, xylene, chlorinated ethylene (trichloroethylene, tetrachloroethylene, dichloroethylene, etc.), for example. For example, it becomes H ₂ O, CO ₂ , a halogen substance, etc. and is converted into a harmless substance, and the soil is purified.

  Returning to FIG. 2D, the backfilling process of the underground pile building mixed material C will be described. The underground pile forming mixed material C charged into the casing 14 accumulates on the upper end surface of the thrust screw 17. In this state, the thrust screw 17 is rotated in the direction to be discharged into the hole 51, the underground pile forming mixed material C is filled between the plurality of screw fins, and the thrust screw 17 is further rotated to make the hole. The underground pile building mixed material C is discharged toward the bottom 51a of 51. Further, simultaneously with the start of rotation of the thrust screw 17, the casing 14 is rotated in the direction opposite to the rotation direction of the thrust screw 17, and the thrust screw 17 and the tip of the casing 14 are gradually moved to the ground surface side, so that the bore 51 The space between the bottom 51a and the tip of the casing 14 is filled with the underground pile forming mixed material C. After backfilling the underground pile building material C, the catalyst D supplied from the tip 18a of the shaft 16 through the through hole 18 is injected into the backfilled underground pile building material C. In addition, you may perform discharge | emission of the mixing material C for underground pile construction, and injection | pouring of the catalyst D simultaneously. That is, if the injection of the catalyst D is started simultaneously with the start of the discharge of the underground pile building mixed material C, and the catalyst D is included in the discharged underground pile building mixed material C, the underground pile building use The catalyst D can be more uniformly permeated into the mixed material C.

As shown in FIG.2 (e), after completion | finish of the backfilling process of the said underground pile formation mixed material C, the compacting process of the underground pile formation mixed material C is performed. Specifically, after the rotation of the casing 14 is stopped, a rotational force is applied only to the thrust screw 17, the underground pile building mixed material C is discharged toward the bottom 51 a of the bore 51, and the bottom of the bore 51 The underground pile building mixed material C filled in 51a is compacted. Further, by introducing the underground pile forming mixed material C and rotating the thrust screw 17, the initial hole diameter D1 of the bore 51 can be expanded to the hole diameter D2. By the compaction step, the catalyst D injected into the underground pile building mixture C permeates downward, so that the catalyst D can be uniformly diffused into the underground pile building mixture C.
If the resistance acting on the thrust screw 17 is detected as a change in the driving torque of the motor (not shown) in the above-described work of expanding the diameter by backfilling and compacting, the diameter is expanded by compaction by measuring the torque change. Since the change in torque until the hole diameter is increased from the hole diameter D1 to the hole diameter D2 is stored in, for example, the motor control device of the auger machine 12 for thrust screw (not shown), the diameter expansion work can be easily performed. It can be performed.

Through the above-described backfilling step and compaction step, one creation step of the underground pile formed in a part of the height range where the contaminated soil 52 exists in the borehole 51 is completed. By repeating, the underground pile made of the underground pile forming mixed material C is formed so as to reach the height T1 where the contaminated soil 52 exists. That is, as shown in FIGS. 3 (f) to 3 (j), the second stage underground is obtained by refilling and compacting the hole 51 above the underground pile 54 a created by a single preparation process. At least contaminated soil 52 exists by creating the pile 54b, filling back the hole 51 above the second-stage underground pile 54b, and forming the third-stage underground pile 54c by compaction. The underground pile 54 expanded in diameter over the range of height can be created.
That is, the underground pile 54 is backfilled by introducing the underground pile formation mixed material C into the borehole 51 formed by excavating the boundary 52a on the underground side where the contaminated soil 52 exists. The catalyst D is injected into the mixed material for building underground piles C and compacted, and the diameter is expanded to form the first-stage underground pile 54a, and the underground pile forming mixed material is formed on the underground pile 54a. The material C is injected and backfilled, and the catalyst D is injected into the backfilled underground pile building material C to be compacted, and the hole 51 is expanded to form the second-stage underground pile 54b. The underground pile forming mixed material C is put on the underground pile 54b and backfilled, and the catalyst D is injected into the backfilled underground pile forming mixed material C to be compacted. The diameter of the hole 51 is expanded to create a third-stage underground pile 54c, and in this way, injection of the catalyst D and compaction of the underground pile-forming mixed material C are performed. It is Construction by performing one another to the height range to reach the surface side of the boundary 52b that is contaminated soil 52 present.
The remaining portion in the hole 51, that is, the portion corresponding to the formation 53 where the contaminated soil 52 does not exist may be compacted without being expanded in diameter.

FIG. 4 is a diagram showing the positional relationship of the various local piles 54 when the contaminated soil 50 is viewed in plan when a plurality of underground piles 54 are created with respect to the contaminated soil 50.
As shown in FIG. 4, when the contaminated soil 50 is viewed in plan, the hole diameter D1 of the dredging hole 51 is a hole diameter where the dredged holes wrap, that is, the hole diameter D2 by compacting the dredging hole 51 having the hole diameter D1. The boreholes 51 are excavated in the contaminated soil 50 so that the enlarged diameter portions of the underground piles 54 formed by expanding the diameter of the piles overlap each other. Specifically, a plurality of underground piles 54 are formed in a staggered or square shape with respect to the contaminated soil 52 so that the enlarged diameter portions of adjacent underground piles 54 are continuous with each other. Since the plurality of underground piles 54 erected on the contaminated soil 50 overlap in a range where the contaminated soil 52 exists, the piles 54 are formed in a plan view in the formation where the contaminated soil 52 exists. The proportion of underground piles per unit area increases, and a wide range of purification can be performed efficiently.
In addition, since the plurality of underground piles 54 standing in the contaminated soil 50 act like a filter in the ground, the contaminants pass through the region where the underground piles 54 are provided together with the groundwater. Contaminants can be purified.

In addition, in the said embodiment, the underground in which the purified sand and the crushed stone prepared beforehand separately from the discharge soil discharged | emitted when forming the fistula 51 or the said discharge soil are mixed as the soil B for underground preparation Although it was set as the soil for pile construction, it is good also as soil B for underground creation by mixing discharge soil and the soil for underground pile preparation prepared previously.
Further, the sodium hydroxide or potassium hydroxide as the catalyst D for performing the purification reaction in a chain is not limited to being injected after the backfilling and before the compaction, but during the compaction by the thrust screw 17 or the compaction. It may be injected later.

Embodiment 2
In the first embodiment, the underground pile formation mixed material C in which the underground formation soil B and the powder alkali-activated persulfate as the purification agent A are mixed is introduced into the borehole 51 and the borehole is introduced. In the second embodiment, it is described that the underground pile 54 is formed by alternately filling back and filling 51 and injecting and compacting sodium hydroxide or potassium hydroxide as the catalyst D to form the underground pile 54. The ground pile mixing material C ′, in which the purification agent A ′, which is obtained by coating the alkali-activated persulfate of the body with a water-soluble polymer such as chitosan or sodium alginate, and the underground soil B, is pre-mixed. It is put into 51 and the underground pile 54 is created.
The purification agent A ′ according to the present invention is, for example, a powdery purification agent A encapsulated by a predetermined amount with a thin film made of a water-soluble polymer. The method of coating the purification agent A is not limited to the above, and it may be sealed in a capsule made of a water-soluble polymer, or coated with the water-soluble polymer in the process of producing the powder purification agent A. May be.

Hereinafter, the creation method of the underground pile 54 of Embodiment 2 which concerns on this invention is demonstrated. In addition, since it is the same as that of Embodiment 1 about the process until formation of the fistula 51, description is abbreviate | omitted. In Embodiment 2, the catalyst D is not charged in the backfilling process of Embodiment 1.
That is, as shown in FIGS. 3 (f) to 3 (j), the underground pile 54 is used to create an underground pile in the borehole 51 formed by excavating the boundary 52 a on the underground side where the contaminated soil 52 exists. The mixed material C ′ is introduced and backfilled, and the backfilled underground pile formation mixed material C ′ is compacted and expanded to form a first-stage underground pile 54a. The underground pile formation mixed material C ′ is injected and backfilled, the backfilled underground pile formation mixed material C ′ is compacted, and the bore 51 is expanded to expand the second-stage underground pile 54b. The ground pile building mixture C 'is put on the underground pile 54b and backfilled, and the backfilled underground pile building mixture C' is compacted and the hole 51 is enlarged. Thus, the third-stage underground pile 54c is formed, and in this way, the ground pile-forming mixed material C ′ is compacted alternately on the surface side where the contaminated soil 52 exists. Ground pile 54 is reclamation by performing up to the height range to reach the field 52b.
The portion corresponding to the formation 53 in which the remaining contaminated soil 52 does not exist in the borehole 51 is compacted without expanding the diameter.

Next, after the step shown in FIG. 3 (j), the center of the underground pile 54 formed as shown in FIG. 5 (k) is drilled to the depth of the boundary 52 a, and a part of the narrow tube 25 is the surface of the formation 53. From the boundary 52a to the surface of the formation 53, the narrow tube 25 is built in the underground pile 54, and the liquid supply means 20 is connected to a part of the narrow tube 25 protruding to the ground surface as shown in FIG. The extended tube is connected, and the catalyst D supplied from the fluid supply means 20 is injected into the underground pile 54.
Specifically, a plurality of holes 25a penetrating the outer peripheral surface of the thin tube 25 in the radial direction are formed in the thin tube 25 built in the underground pile 54 from the boundary 52a to the boundary 52b and supplied into the thin tube 25. The catalyst D is caused to flow out of the plurality of holes 25a and permeate into the underground pile building mixed material C ′. That is, the underground pile forming mixed material C ′, in which sodium hydroxide or potassium hydroxide as the catalyst D is compacted, is introduced after reaching the height where contaminated soil exists in the borehole 51.
Therefore, prior to the supply of the catalyst D, the thin film of the purifier A ′ reacts with the moisture of the underground pile building mixture C ′ to dissolve and is formed from the underground pile building mixture C ′. The cleaning agent A gradually permeates into the contaminated soil 50 that is not. Then, the contaminated soil 50 is purified over a wide area by reacting with the catalyst D supplied from the narrow tube 25 and permeating through the underground pile building mixture C ′ with respect to the purification agent A that has permeated over a wide area. Is done.
By performing the above-described process in a range where the contaminated soil 50 is purified, a wide range of contaminated soil 50 can be reliably purified and the ground can be strengthened.

FIG. 6 is a diagram showing an example in the case where the underground pile 54 is created by the above process over a wide range. This figure shows a case where the distance between the centers of the underground piles 54 is set to be 2 m with respect to a range of 400 m ² of 20 m × 20 m.
In this case, as shown in FIG. 6, the total number of underground piles 54 to be constructed is 100, and if the number of construction man-hours per day is 10, the total construction days will require 10 days.
First, the ground can be strengthened by creating the underground pile 54 using the underground pile creation mixed material C ′ in which the purification agent A ′ and the underground creation soil B according to the present invention are mixed. . Next, by allowing the catalyst D to permeate all the underground piles 54 at the same time, the contaminated soil 50 can be purified over a wide range at once.
That is, the purification agent A ′ of the mixed material C ′ for underground pile construction, which was created on the first day of the purification of the contaminated soil 50 and the strengthening of the ground in the above range, is immediately covered with the water-soluble polymer. All the purification agent A reacts gradually without reacting with moisture in the ground, and the purification agent A penetrates from the inside of the underground pile 54 to the contaminated soil 50 that has not been created. Thereby, the purifier A can be permeated slowly over a wide range until the 10th day after the completion of construction.
Then, after the formation of all the underground piles 54 is completed, the catalyst D is injected into all of the underground piles 54 at a time, so that the catalyst D from the mixed material C ′ for underground pile formation to the contaminated soil 50 is obtained. The cleaning agent A and the pollutant are allowed to react with each other so that a wide range can be purified at once.
In addition, although it demonstrated that the thin tube 25 which inject | pours the catalyst D was built in the underground pile 54, the thin tube 25 was set in the center (position of the point P shown by the black circle of FIG. 6) of the underground pile 54 located mutually diagonally. The catalyst D may be injected, and the catalyst D may be permeated into the ground of the contaminated soil 50 to react with the purifier A leached from the thin film portion in which the purifier A ′ is dissolved. Thus, by installing the thin tube 25 and allowing the catalyst D to permeate, the number of steps for providing the thin tube 25 can be reduced, so that the work period can be shortened.
In addition, after the underground pile 54 is built up to the boundary 52b in the entire range, the catalyst D is put into a hole opened in the formation 53, and the catalyst D is allowed to permeate in the direction of gravity to react with the purifier A ′. . In this case, since it is not necessary to install a thin tube for supplying the catalyst D, the number of man-hours can be further reduced.
That is, according to the second embodiment, since the cleaning agent A ′ is coated with the water-soluble polymer, the cleaning agent A ′ does not immediately react with moisture in the ground, so that the cleaning agent A ′ is purified. The time during which the cleaning agent A permeates the contaminated soil 50 can be set by gradually exuding the agent A. Therefore, even if the range of purification of the contaminated soil 50 is wide, it is possible to prevent the area that has been purified from being contaminated again as when partially purified, and to prevent the generation of areas that are not purified by the contaminated soil 50. .

In Embodiment 2 described above, the purifier A is encapsulated with a thin film. However, the purifier A ′ and the underground preparation soil B, in which the number of thin films to be encapsulated is changed according to the construction schedule, You may make it comprise the mixed material C 'for intermediate pile creation. By comprising in this way, after all the creation of the underground pile 54 is completed and ground reinforcement is carried out, the catalyst D can be penetrate | infiltrated and all the area | regions of the contaminated soil 50 can be purified at once.
In addition, even when standing a plurality of underground piles in the contaminated soil, as shown in FIG. 4, the hole diameter of the fistula is a hole diameter that the fistulas after diameter expansion wraps when the contaminated soil is viewed in plan. It may be erected.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the above embodiment.

1 crane, 11 auger machine for casing,
12 auger machine for inner screw, 14 casing, 15 hopper,
16 shaft, 17 thrust screw, 18 through hole, 20 fluid supply means,
50 contaminated soil, 51 fistula, 52 contaminated soil, 54 underground pile,
A: A ′ cleaning agent, B underground soil, C; C ′ mixed material for underground pile formation.

Claims (7)

A method of purifying soil by setting up underground piles in contaminated soil,
Drilling a hole to a depth where contaminated soil exists;
The underground soil in which the discharged soil discharged by the excavation or a previously prepared soil for underground pile formation and an alkali activated persulfate selected from sodium persulfate, potassium persulfate, and ammonium persulfate are mixed And a step of filling the pile formation mixed material into the hole and backfilling the hole.
A contaminated soil purification method, wherein sodium hydroxide or potassium hydroxide is introduced into the borehole after the underground pile building mixed material is introduced into the borehole.   In the step of refilling the borehole, the underground pile building mixed material is put into a casing penetrating into the borehole, and the underground pile building mixed material is moved by the rotational force of the thrust screw inside the casing. The contaminated soil purification method according to claim 1, wherein the underground pile building mixed material is compacted in the borehole.   The contaminated soil purification method according to claim 1 or 2, wherein the alkali-activated persulfate is coated with a water-soluble polymer.   The introduction of the sodium hydroxide or potassium hydroxide and the compaction of the underground pile formation mixed material are alternately performed, and the ground soil pile mixed material is contaminated soil in the borehole. The contaminated soil purification method according to claim 2, wherein the method reaches the height.   The said sodium hydroxide or potassium hydroxide is thrown in after making the compacted underground pile formation mixed material reach the height where the contaminated soil exists in the borehole. Contaminated soil purification method.   The contaminated soil purification method according to any one of claims 2 to 5, wherein a diameter range of the contaminated soil in the fistula is expanded by the compaction.   In the case where a plurality of underground piles are erected on the contaminated soil, the hole diameter of the fistula is set to a diameter that wraps the fistulas after the diameter expansion when the contaminated soil is viewed in plan. Item 7. A method for purifying contaminated soil according to Item 6.

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