JP2014171994A - Ground mix body, ground purification body, and purification method of contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground mix body and a ground purification body suitable for purifying contaminated soil of a subsoil formed of a sand layer, and an alternation of a silt layer and a clay layer, and a purification method of contaminated soil for purifying contamination substance of a whole contaminated section surely.SOLUTION: The ground mix body is a mixed body of soil of a subsoil of the site including sand, silt, and clay and water, and is formed on a subsoil of a sand layer contaminated by a harmful substance, and on an alternation contaminated subsoil of silt and clay layers, and the ground mix body has higher water permeability than that of the silt and clay layers. The ground purification body formed by forming a well for injecting agents on the ground mix body, is also provided.

Description

  The present invention relates to an underground kneaded body constructed in contaminated soil contaminated with harmful substances such as cyan and volatile organic compounds, an underground purifier, and a method for purifying contaminated soil using the same.

  In many cases, soil contamination and groundwater contamination due to toxic substances such as cyan and volatile organic compounds are contaminated in the ground consisting of sand, silt and clay layers. There are many examples of such contamination from the first aquifer to the second aquifer (see FIG. 10). In particular, in the silt / clay layer between the first aquifer and the second aquifer, harmful substances are often adsorbed and become highly contaminated. In FIG. 10, hatched portions indicate contamination by harmful substances.

  Conventional methods for purifying contaminated soil and groundwater with harmful substances include well-known methods for injecting wells into contaminated soil and injecting chemicals into the target layer to purify, decompose, and insolubilize them. There is known a purification method (Japanese Patent Laid-Open No. 2012-40476) in which contaminated soil is mixed and stirred while injecting a nutrient for use.

JP 2012-40476 A

  However, conventional known methods are difficult to apply to unsaturated regions above groundwater. In addition, there is a problem that the penetration of the drug into the contaminated area is not reliable because it is difficult to uniformly diffuse the drug into the silt / clay layer, which is a hardly water permeable layer. Moreover, the purification method of JP2012-40476 is a partial construction for a saturated layer that does not include a silt layer, and is not intended for purification of high-concentration contamination adsorbed on the silt layer. Moreover, the contaminated soil other than the stirring and mixing region 12 is still low in water permeability, and there is a problem that the nutrient is not sufficiently penetrated.

  Accordingly, an object of the present invention is to provide an underground kneaded body suitable for the purification of soil contaminated soil consisting of a sand layer and a silt / clay layer, and an underground purification body using the same. It is an object of the present invention to provide a method for remediating contaminated soil that can sufficiently infiltrate the entire contaminated area and reliably purify high-concentration contaminants adsorbed on the silt / clay layer.

  In such a situation, the present inventors have intensively studied, and as a result, are a mixture of local soil containing sand, silt and clay and water on the alternate layer ground of sand layer and silt / clay layer contaminated with harmful substances. If an underground kneaded body with high water permeability is formed, it is suitable for purification of soil contaminated with ground consisting of sand and silt / clay layers, and further, a well for injecting chemicals is formed in the underground kneaded body. The underground purifier has been found to be able to sufficiently penetrate the entire contaminated area and reliably purify the high-concentration pollutant adsorbed on the silt / clay layer, thereby completing the present invention.

  That is, the present invention is formed on an alternating layer ground of a sand layer and a silt / clay layer contaminated with a harmful substance, and is a kneaded mixture of local soil containing sand, silt and clay, and water. -The underground kneaded body characterized by having a water permeability higher than the water permeability of a clay layer.

  Moreover, this invention provides the underground purification body characterized by forming the well for chemical | medical agent injection | pouring in the said underground kneading body.

  Further, the present invention is a method for purifying an alternate layer ground of a sand layer and a silt / clay layer contaminated with harmful substances, using a stirrer and stirring and kneading while injecting chemicals and water into the contaminated soil And it provides the purification method of the contaminated soil characterized by forming the underground kneaded body which has water permeability higher than the water permeability of this silt clay layer by penetrating or pulling out to a predetermined depth.

  Further, the present invention is a method for purifying an alternate layer ground of a sand layer and a silt / clay layer contaminated with harmful substances, using a stirring device, stirring and kneading the contaminated soil while adding water, I step for forming an underground kneaded body having water permeability higher than that of the silt / clay layer by penetrating or drawing out to a depth, and II step for forming a well for injecting a drug in the underground kneaded body And a method for purifying contaminated soil, characterized in that a step III is performed to purify the underground kneaded body containing harmful substances by injecting a chemical into the well.

  According to the present invention, it is possible to sufficiently permeate the entire contaminated area of the contaminated soil consisting of sand layers and silt / clay layers contaminated with harmful substances, and to ensure that high-concentration pollutants adsorbed on the silt / clay layers are absorbed It can be purified.

It is a figure explaining the purification method of the contaminated soil in embodiment of this invention. (A) is a schematic diagram showing the state of the alternating layer ground before construction, (B) is the state of the ground during stirring and kneading, and (C) is a schematic view showing the ground kneaded body after stirring and kneading. It is a boring simplified columnar figure of the ground for purification in an example. The particle size accumulation curve of the code | symbol A part of FIG. 3 is shown. The particle size accumulation curve of the code | symbol B part of FIG. 3 is shown. The particle size accumulation curve of the code | symbol C part of FIG. 3 is shown. The particle size accumulation curve of the code | symbol D part of FIG. 3 is shown. It is a figure explaining the purification method of an underground purification body and contaminated soil. It is a figure explaining the purification process in the purification method of the present invention. It is a schematic diagram of the contaminated alternate layer ground.

(Description of underground kneaded body)
Next, the underground kneaded body in the embodiment of the present invention will be described with reference to FIGS. The underground kneaded body 10 according to the present invention is formed on the soil layer 3 with the sand layers 33 and 35 and the silt / clay layer 34 contaminated with harmful substances. It is a water kneaded product and has a water permeability higher than that of the silt / clay layer.

The alternate-layer ground is a ground including a two-layer structure of a sand layer 33 and a silt / clay layer 34, in particular, a ground including a three-layer structure of a sand layer 33, a silt / clay layer 34, and a sand layer 35. An embankment layer mainly composed of gravel mixed sand may be present on 33. The silt / clay layer 34 is a silt layer, a clay layer, or a layer in which silt and clay are mixed. The water permeability coefficient of the sand layer 33 is approximately 10 ⁻⁴ to 10 ⁻² cm / second, the water permeability coefficient of the silt / clay layer 34 is approximately 10 ⁻⁷ to 10 ⁻⁴ cm / second, and the sand layers 33 and 35 are water permeable layers. Also, the silt / clay layer 34 is also referred to as a poorly permeable layer. The sand layer 33 is a normal aquifer. Therefore, in the present specification, in the case of a ground having a three-layer structure of the sand layer 33, the silt / clay layer 34, and the sand layer 35, the sand layer 33 on the surface layer side is the first aquifer and the sand layer 35 on the opposite surface side is the second aquifer. Also called a layer.

  The ground where the underground kneaded body is formed is an alternating layer ground contaminated with harmful substances. As the contaminated area, any harmful substance may be present as long as it exists in at least the silt / clay layer, and the harmful substance has at least three layers of sand layer 33, silt / clay layer 34, and sand layer 35, that is, from the first aquifer. What extends to the second aquifer exhibits the effect of the present invention remarkably. Hazardous substances include hydrocarbons such as benzene, toluene, ethylbenzene, xylene, and ketones; organochlorine compounds such as trichloroethylene, tetrachloroethylene, and dichloroethylene; cyanides such as cyanides of various cyanides and various metals such as iron, nickel, and copper Compound; Examples include oils and fats such as gasoline, light oil, kerosene, heavy oil, machine oil, and lubricating oil. These exemplified harmful substances include one kind or two or more kinds.

  The underground kneaded body of the present invention is a kneaded product of local clay and water containing sand, silt and clay. That is, the underground kneaded body is a kneaded material of raw ground soil and water, and may contain gravel or the like contained in the embankment layer. The underground kneaded body naturally contains harmful substances. The underground kneaded body may contain a drug. By including the chemical in the underground kneaded body, the purification efficiency of the chemical injected from the well can be increased thereafter. Further, depending on the type and concentration of the harmful substance, the subsequent installation of the well for injecting the drug can be omitted. Examples of the drug include nutrients for accelerating the degradation of cyanide by microorganisms living in the contaminated soil. Water is groundwater and hydrolyzed water. Water that has been added includes water contained in the aqueous solution of the drug. The underground kneaded body is kneaded so that the whole is almost uniform. However, since the water permeability is extremely large, the coarse-grained soil tends to accumulate on the lower side and the fine-grained soil tends to accumulate on the upper side.

The underground kneaded body of the present invention has a water permeability higher than that of the silt / clay layer, preferably 10 times or more, more preferably 100 times or more, particularly preferably 1000 times the water permeability coefficient of the silt / clay layer. The high water permeability coefficient is shown above. Specifically, the hydraulic conductivity of the underground kneaded body is 10 ⁻⁶ cm / second or more, preferably about 10 ⁻⁶ to 10 ⁻³ cm / second. The permeability coefficient of the underground kneaded body is obtained by a known in-situ permeability test or indoor permeability test. When the underground kneaded body exhibits the above-mentioned water permeability, the alternate-layered ground becomes an ultra-soft ground, which facilitates the injection and penetration of chemicals and improves the purification efficiency.

  The underground kneaded body of the present invention can be constructed over a wide area by lap construction or contact circle construction. That is, the underground kneaded body is preferably constructed in the entire contaminated area. As a result, there is no unconstructed portion of the underground kneaded body in the contaminated area, and the drug reliably penetrates into the entire contaminated area. Moreover, the water permeability improves more in the overlapping construction part by lap construction. The shape of the underground kneaded body of the present invention is, for example, a columnar pile, a rectangular wall body, a continuous construction body, a lap construction body, or a contact construction.

(Underground purification body)
The underground purification body of this invention forms the well for chemical | medical agent injection | pouring in the underground kneaded body. Wells for drug injection may be known ones, and are formed in an appropriate number in the underground kneaded body. In the case of forming a plurality of wells for injecting medicine, it is preferable to install them at approximately equal intervals so that the medicine is evenly distributed throughout the contaminated area. Further, in the ground where the flow of groundwater is fast, the groundwater may be shifted to the upstream side. In the underground purification body of the present invention, an observation well may be formed in the underground kneaded body. As the observation well, a known well can be applied, and the groundwater is pumped up to monitor the concentration of nutrients in the groundwater, the concentration of contaminants, the water quality, the state of the groundwater such as microorganisms, and the like.

  The underground purification body of the present invention is preferably formed over the entire contaminated area. Thereby, there is no unconstructed portion of the underground purification body in the contaminated area, and the drug can penetrate into the entire contaminated area. The permeability coefficient of the underground purification body of the present invention is the same as that of the underground kneaded body of the present invention.

(Purification method of contaminated soil)
Next, the contaminated soil purification method (first method) according to the first embodiment of the present invention will be described. That is, the method for purifying contaminated soil in this example is a method for purifying the alternate layer ground 3 of the sand layer 33 and the silt / clay 34 layer contaminated with harmful substances. Whether or not it is the two-layered ground 3 can be determined by a known boring survey and soil survey. FIG. 1 shows an example of contaminated ground. From the surface side to the depth direction, it consists of the embankment layer 31 that is sand mixed with gravel, the sand layer 33 that is the first aquifer, the silt / clay layer 34, and the sand layer 35 that is the second aquifer. The saturated layer 32 is a saturated layer (see FIG. 2A). The contaminated layer X contaminated with harmful substances extends over these layers. In particular, in the silt / clay layer 34 between the first aquifer 33 and the second aquifer 35, harmful substances are adsorbed and become highly concentrated. Examples of the harmful substance are the same as those in the underground kneaded body of the present invention.

  In the method for purifying contaminated soil of this example, the step I uses the stirring device 1 to stir and knead the contaminated soil X while adding water, and penetrates or pulls out to a predetermined depth. It is a step of forming an underground kneaded body having higher water permeability than water permeability. As the stirring device 1, the stirring device 1 provided with the well-known stirring blade 11 used by a deep-layer mixing process method or an underground columnar pile construction method, or a well-known trencher can be used. As the stirring blade 11 in the stirring device 1 including the stirring blade 11, a two-stage blade of two blades (two) or a horizontal stirring blade of a three-stage blade is preferable. By using such a stirring device 1, the contaminated soil X (alternate ground) can be stirred and mixed at a predetermined depth and a predetermined diameter. Reference numeral 2 denotes a water supply device or a chemical aqueous solution supply device. Hereinafter, the purification method in the case of using the stirring apparatus 1 provided with the stirring blade 11 is demonstrated.

  In step I, the axis of the rotating shaft 12 of the stirring device 1 is made to coincide with the center of the stirring and kneading point of the contaminated soil X. Next, the rotating shaft 12 is penetrated into the ground while the stirring device 1 is driven to rotate the stirring blade 11. At this time, the mixture is stirred and kneaded while adding water. By stirring and kneading while adding water, an ultra-soft ground with high water permeability can be formed. In addition, although the amount of water is determined in consideration of the moisture content contained in the soil, the stirring region, the hydraulic conductivity of the obtained kneaded material, and the like, it is approximately 5 to 20% by volume with respect to the stirring kneaded ground.

  The stirring and kneading is at the time of penetration or at the time of withdrawal or at the time of penetration and at the time of withdrawal, preferably both at the time of penetration and at the time of withdrawal. The penetration speed and the drawing speed may be determined as suitable speeds for obtaining a highly uniform kneaded product. By such an operation, gravel, fine-grained soil and coarse-grained soil are sufficiently stirred, and a kneaded product having high uniformity and water permeability is obtained. As shown in FIG. 2 (B), the agitation and kneading zone has no distinction between the sand layer and the silt / clay layer, and becomes ultra-soft soil with high water permeability. In addition, fine-grained soil tends to accumulate upward. In step I, the chemicals may be added simultaneously while stirring and kneading. When the pretreatment with a chemical | medical agent is required for a hazardous | toxic substance, if the pretreatment chemical | medical agent is inject | poured and performed in the I process, the purification process in subsequent III processes can be performed efficiently. In addition, when inject | pouring a chemical | medical agent in I process, when a chemical | medical agent contains water, injection | pouring of single water can be skipped.

In the step I, the ground kneaded body 10a having water permeability higher than that of the silt / clay layer 34 is obtained by stirring and kneading (FIG. 2C). That is, by stirring and kneading, an underground kneaded body 10a exhibiting a water permeability of 10 times or more, more preferably 100 times or more, particularly preferably 1000 times or more that of the silt / clay layer is obtained. Specifically, the hydraulic conductivity of the underground kneaded body is 10 ⁻⁶ cm / second or more, preferably about 10 ⁻⁶ to 10 ⁻³ cm / second. The hydraulic conductivity is determined by the volume ratio of sand and clay in the alternating layer ground. The amount of water added is adjusted according to the water content of the original ground.

  A large number of columnar underground kneaded bodies 10a are formed in the contaminated ground X, and preferably formed in the entire contaminated area. As a result, the entire contaminated area can be made into an ultra-soft ground with high water permeability, and contamination can be reliably purified. When a large number of columnar underground kneaded bodies 10a are formed in the contaminated ground X, it is preferable to form them by lapping. As a result, the entire contaminated ground can be efficiently made into an ultra-soft ground. Moreover, the water permeability improves more in the overlapping construction part by lap construction or contact circle construction.

  Step II is a step of forming a well for drug injection in the underground kneaded body. That is, as shown in FIG. 9, a well 13 for injecting a drug is formed in the underground kneaded body 10b constructed in the contaminated area. As the well for drug injection, a known well in which a tubular body whose tip is a screen tube is built can be used, and examples include those described in JP-A-2009-6304. Wells for injecting chemicals are formed in an appropriate number in the underground kneaded body. When forming a plurality of wells for injecting drugs, it is preferable to install them at equal intervals so that the drugs are evenly distributed throughout the contaminated area.

  Step III is a step of purifying contaminated soil by injecting chemicals into the well 13. The drug is the same as the drug in the underground purification body, and examples thereof include a nutrient for promoting the decomposition of cyanide compounds by microorganisms living in the contaminated soil. As a method for injecting a chemical into the well 13 to purify the contaminated soil, known methods such as a natural flow method and a double packer method which is pressure injection can be applied. As shown in FIG. 9, the drug injected into the well 13 penetrates the entire contaminated ground X because the underground kneaded body 10 b subjected to lapping has high water permeability. And since the chemical | medical agent osmose | permeates the contaminated ground X whole area, the microorganisms which inhabit in the contaminated soil will be activated, and decomposition | disassembly of the cyanide by microorganisms will be accelerated | stimulated.

  Next, a method for purifying contaminated soil (second method) according to the second embodiment of the present invention will be described. That is, the method for purifying contaminated soil in this example is a method for purifying an alternate layer ground of a sand layer and a silt / clay layer contaminated with harmful substances, using a stirring device equipped with stirring blades, This is a method of forming an underground kneaded body having a water permeability higher than that of the silt / clay layer by stirring and kneading while injecting a drug and water, and penetrating or withdrawing to a predetermined depth. The second method is different from the first method in that the injection of the drug is performed in the I step, the well for the drug injection is not installed, and the contaminated ground is purified.

  In the second method, only differences from the first method will be described. That is, the drug is injected into the stirring zone during stirring and kneading. The injection of the drug may be the same as or different from the injection of water as long as it is during stirring and kneading. The drug and water may be a drug and water alone or a drug containing water. Therefore, in the case of a medicine containing water, it may be possible to omit injection of single water. By stirring and kneading while pouring the chemical into the contaminated soil, the underground kneaded body contains the chemical uniformly. Similarly, the wrap construction body in which the underground kneaded body is lapped also contains the drug uniformly. The hydraulic conductivity of the underground kneaded body obtained by this second method is the same as the hydraulic conductivity of the underground kneaded body obtained by the first method. The underground kneaded body obtained by the second method contains harmful substances adsorbed particularly on the silt / clay layer in the alternate layered ground, and the harmful substances can be purified by the injection effect of the drug.

  In the contaminated soil purification method of the present invention, a step of forming an observation well in the underground kneaded body may be further performed. The observation well is the same as the observation well described above.

(Example)
EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

(Formation of underground kneaded body)
The alternate ground (test ground) was selected by the boring survey and soil survey. FIG. 3 shows a simplified boring column diagram of the alternate layer ground. The ground shown in Fig. 3 has an embankment (sand mixed with gravel) layer, an embankment (sand mixed with sand and charcoal sand) layer, an embankment (silty sand) layer, and a buried (fine sand) layer in the depth direction from the surface. And a buried (clay) layer and a buried (sand) layer. Among these, the particle size accumulation curve of the embankment (silty sand) layer (symbol; A) is shown in FIG. 4, and the particle size accumulation curve of the buried soil (fine sand) layer (symbol; B) is shown in FIG. FIG. 6 shows the particle size accumulation curve of the upper part of the buried soil (clay) layer (symbol; C), and FIG. 7 shows the particle size accumulation curve of the lower part of the buried soil (clay sand) layer (symbol; D). . The groundwater level of this ground was -1.2 m, and the hydraulic conductivity (indoor kneading test) of the buried (clay) layer was 2.25 × 10 ⁻⁷ cm / sec. In addition, the initial TOC (total organic carbon) elution concentration in the alternating layer ground was 8.2 mg / L. In addition, this alternate layer ground is for a test, and sees the osmosis | permeation diffusion state of a chemical | medical agent.

  Next, using a stirrer equipped with a three-stage stirrer blade on both blades, the above-mentioned alternate layer ground is stirred and kneaded at the time of penetration and withdrawing while adding 20% by volume of water. A 3 m underground kneaded body was formed. The stirring device penetrated from the surface layer while stirring, and the substantial stirring and kneading area for obtaining high water permeability was 5 m from a depth of 2 m to 7 m. The stirring and kneading time was 20 minutes. The rotational speed of the rotating shaft was 19 rpm when penetrating, 38 rpm when pulling, the penetrating speed was 0.4 m / min to 0.7 m / min, and the pulling speed was 0.6 to 1.1 m / min.

  Next, soil at points A, B, C, and D in the depth direction of the underground kneaded body was collected and subjected to particle size analysis. The particle size accumulation curve of the corresponding portion of the embankment (silty sand) layer (symbol; A) in the underground kneaded body is shown in FIG. 4, and the corresponding portion of the buried (fine sand) layer (symbol; B) in the underground kneaded body 5 shows the particle size accumulation curve, and FIG. 6 shows the particle size accumulation curve of the upper part (sign: C) of the buried (clay) layer in the underground kneaded body. The particle size accumulation curve at the lower part of the (sand) layer (symbol: D) is shown in FIG. In addition, although the particle size analysis before and behind stirring kneading | mixing of each layer shown by code | symbol AD was performed also in three different different places in the same alternating layer ground area, each showed the same particle size accumulation curve.

From the result of point B in FIG. 5, it can be seen that the fine sand layer was homogeneous fine sand but became non-homogeneous and coarse particles by stirring and kneading. Moreover, it can be seen from the results of points C and D in FIGS. 6 and 7 that the clay layer was made of a homogeneous high-plastic clay and contained coarse particles by stirring and kneading. Moreover, although the upper part of the stirring kneaded material was heterogeneous and contained more coarse particles than the lower part, it was generally homogeneous. In addition, the hydraulic conductivity of the underground kneaded body is 3.34 × 10 ⁻⁶ cm / sec (indoor kneading test), 3.85 × 10 ⁻⁶ cm / sec (in-situ kneading test), and the original clay layer The water permeability was about 10 times higher. Thus, the alternate layer ground caused dramatic composition change by the hydro-kneading.

(Underground kneaded body with lapping)
As shown in FIG. 8, seven underground kneaded bodies having a height of 5 m having a diameter of 1.3 m and a depth of 2 to 7 m were lapped on a virtual contaminated ground area Y having a diameter of about 3.5 m. The underground kneaded body subjected to wrapping is obtained by lapping six columnar underground kneaded bodies arranged in the circumferential direction with respect to one central columnar underground kneaded body.

(Infiltration and diffusion test of underground purifiers and drugs)
An injection well 81 was formed in the center of the underground kneaded body shown in FIG. Moreover, the commercially available chemical | medical agent containing glucose and various amino acids was inject | poured with respect to the injection well 81 by the double packer method. Immediately after drug injection, boring is performed at predetermined positions in three directions (A direction, B direction, and C direction) extending radially from the injection well 81, and the soil is collected and the TOC concentration in the soil (mg / kg) ) Was measured. The measurement results are shown in Tables 1 to 3. The boring positions are 0.5 m, 1.0 m, and 1.5 m from the injection well 81 in the A direction (A1, A2, and A3, respectively), and 0.5 m from the injection well 81 in the B direction. The positions are 0 m and 1.5 m (B1, B2, and B3, respectively), and 0.5 m, 1.0 m, and 1.5 m from the injection well 81 (C1, C2, and C3, respectively) in the C direction. Further, in the table, the upper part of the depth means the depth of 2.27 m to 3.68 m, and the lower part of the depth means the depth of 4.42 m to 5.23 m, which are shown as average values at three different points in the depth direction. The reason for collecting the soil by drilling immediately after the injection of the drug is that although the TOC derived from the drug penetrates and diffuses into the kneaded ground, the value decreases due to microbial decomposition over time. This is to avoid as much as possible. In addition, the reference TOC concentration to be compared with the measured TOC concentration was the TOC concentration in the underground kneaded body under the same water addition conditions where no chemical was added. The reference TOC concentration is a ground TOC concentration (31.01 mg / kg) separately obtained by experimentally reproducing an underground kneaded body of an alternating layer ground and under the same water conditions. The underground kneaded body is considered to be ideally uniform in both the upper and lower depths, and an increasing tendency of the drug-derived TOC concentration is seen with respect to the TOC concentration of 31.01 mg / kg as the background value. In Tables 1 to 3, the reference TOC concentration is shown as “reference value”.

  From the results of Tables 1 to 3, although there are variations at almost all points and depths excluding a part of the A direction, B direction, and C direction, they are much higher than the reference TOC concentration and are derived from drugs. The presence of TOC was confirmed. In addition, it has been confirmed by laboratories or the like that harmful substances such as hydrocarbon compounds can be purified with the TOC concentrations derived from the drugs shown in Tables 1 to 3. In addition, when the target concentration that can completely purify harmful substances at each point is small, an increase in the amount of drug used may be increased, and when large, a decrease in the amount of drug used may be handled.

  According to the present invention, it is possible to sufficiently permeate the entire contaminated area of the contaminated soil consisting of sand layers and silt / clay layers contaminated with harmful substances, and to ensure that high-concentration pollutants adsorbed on the silt / clay layers are absorbed It can be purified. For this reason, the use of the ruins of the ground contaminated with harmful substances such as VOCs and cyan is advanced.

DESCRIPTION OF SYMBOLS 1 Stirring device 2 Water supply device 3 Alternating ground 10 Underground kneaded body 33, 35 Sand layer 34 Silt and clay layer 81 Injection well 82 Boring position

Claims (11)

  It is formed in the alternate ground of sand layer and silt / clay layer contaminated with harmful substances, and is a kneaded mixture of local soil and water containing sand, silt and clay, and water permeability of the silt / clay layer An underground kneaded body characterized by having higher water permeability.   The underground kneaded body according to claim 1, wherein the underground kneaded body has a water permeability of 10 times or more higher than that of the silt / clay layer.   3. The underground kneaded body according to claim 1 or 2, wherein the underground kneaded body is formed by lapping or circle contact processing.   The underground kneaded body according to any one of claims 1 to 3, further comprising a drug.   The underground purification body which formed the well for chemical | medical agent injection | pouring in the underground kneading body of any one of Claims 1-4.   6. The underground purification body according to claim 5, wherein the underground purification body is formed over the entire contaminated area.   A method for purifying an alternating layer of a sand layer and a silt / clay layer contaminated with harmful substances, using a stirrer, stirring and kneading the chemical and water into the contaminated soil, to a predetermined depth A method for purifying contaminated soil, characterized by forming an underground kneaded body having a permeability higher than that of the silt / clay layer by penetration or extraction.   The said chemical | medical agent and water are chemical | medical agents and independent water, or are chemical | medical agents containing water, The purification method of the contaminated soil of Claim 7 characterized by the above-mentioned. It is a method for purifying the alternate layer ground of sand layer and silt / clay layer contaminated with harmful substances, using a stirrer, stirring and kneading while adding water to the contaminated soil, and penetrating or extracting to a predetermined depth. And the I step of forming an underground kneaded body having a water permeability higher than that of the silt / clay layer,
II step of forming a well for drug injection in the underground kneaded body,
A method for purifying contaminated soil, comprising performing a step III of purifying an underground kneaded body containing harmful substances by injecting a chemical into the well.   The method for purifying contaminated soil according to claim 9, wherein a chemical is injected in the stirring and kneading in the step I.   The method for purifying contaminated soil according to any one of claims 7 to 10, wherein a permeability coefficient of the underground kneaded body is 10 times or more higher than a permeability coefficient of the silt / clay layer.

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