JP4511315B2 - Soil improvement method - Google Patents

Description

  The present invention relates to a soil improvement method. More specifically, the present invention purifies contaminated soil containing harmful volatile organic compounds (VOCs) and prevents deterioration of the ground strength of the original ground to ensure the trafficability of construction machinery. The present invention relates to a soil improvement method that makes it possible.

  As a method of purifying contaminated soil containing harmful volatile organochlorine compounds (VOC) such as trichlorethylene, tetrachlorethylene, perchlorethylene, and dichloromethane, a metal catalyst is added to the contaminated soil, and a low molecular weight is reduced by a reductive decomposition reaction using the metal catalyst. A method of decomposing into ethylene gas or acetylene gas and finally decomposing into carbon dioxide gas is adopted. As this metal catalyst, iron powder, colloidal iron powder, iron oxide powder or the like is used. In general, cheap iron powder is used, but since it is difficult to uniformly disperse if it is not mixed after it is supplied, it is difficult to oxidize, so the catalytic function and oxidizing power of iron are maintained. Colloidal iron powder is used. Moreover, in order to improve decomposition characteristics, iron oxide powder, electrolytic iron powder, iron powder having an increased specific surface area for reaction activity, and the like are used.

  As a method for efficiently purifying soil using these metal catalysts, a method of excavating soil in situ, supplying iron powder, and stirring and mixing the soil and iron powder has been proposed (for example, patents) Reference 1). In this method, for example, after excavating to a predetermined depth using a stirring member such as a loop bit, iron powder is injected from an injection pipe provided in the stirring member, and the soil and the soil are formed by blades provided around the stirring member. It can be uniformly dispersed by forcibly stirring and mixing the iron powder. The iron powder is supplied as a slurry dispersed in water or dispersed in compressed air. In this method, compressed air or water is supplied at the time of excavation in order to make the excavation easy by giving a lubricant effect of smoothly flowing the excavated soil. This compressed air or water also has the effect of reducing the impact on the ground during excavation and suppressing heat generation during excavation of the cutting member provided at the tip of the stirring member. Further, the compressed air can give excavation stirring effect to the stirring member to further facilitate excavation. In addition, this method has the advantage that it can be constructed without discharging the soil in the original position, and the contaminated soil in a predetermined range can be purified in a short period of time.

  However, although the above method can decompose and remove VOC contained in the contaminated soil, it is possible to supply water or compressed air at the time of excavation, supply water or compressed air at the time of iron powder supply, and further by stirring the soil. There is a problem that the ground strength of the ground is reduced. If ground with a predetermined strength is required after construction, it cannot be achieved by the above method. Therefore, a method has been proposed in which a solidified material is simultaneously supplied together with iron powder to obtain a ground having a predetermined strength along with soil purification (see, for example, Non-Patent Document 1 and Patent Document 2).

  In these methods, solidified materials such as low alkaline cement and calcined gypsum are supplied together with iron powder to the contaminated soil as a slurry, and the contaminated soil and the slurry are stirred and mixed to uniformly distribute the iron powder and the solidified material in the contaminated soil. The VOC is decomposed and removed by a reductive decomposition reaction of iron powder, and solidified by a solidifying material to obtain a ground having a predetermined strength. In these methods, since iron powder and a solidified material are supplied simultaneously, soil purification and ground improvement can be performed with few steps.

  However, when low alkaline cement is used as a solidifying material, even if it is said to be low alkali, it is alkaline, so that this alkali inhibits the reaction between iron powder and VOC, and in particular, water content that must supply a large amount of solidifying material. There is a problem that it cannot be sufficiently decomposed in contaminated soil with a high ratio.

  When calcined gypsum is used as a solidifying material, since it is neutral, the above reaction inhibition does not occur, and a large amount can be supplied even in contaminated soil having a high water content ratio, so that a ground with a predetermined strength can be obtained. In this method using calcined gypsum, the calcined gypsum and iron powder are dispersed and supplied in an amount of water 1 to 10 times that of calcined gypsum, so that the solidification rate by calcined gypsum can be delayed. Therefore, due to this delay effect, the reaction between the iron powder and VOC is sufficiently performed as compared with the case of using the low alkaline cement, and the contaminated soil can be sufficiently purified. In addition, when the slurry permeates into the soil, the water content ratio is reduced, solidification by the calcined gypsum is promoted, and a ground having a predetermined strength can be obtained.

  However, when iron powder or iron oxide powder and calcined gypsum are dispersed in air or nitrogen and supplied as gas, they are not solidified until they are supplied to the soil, but are supplied to the soil with a low water content. Since it immediately solidifies, there was a problem that the VOC could not be sufficiently decomposed.

  In cement, as a method of delaying the setting time, a small amount of retarder is generally added to the cement slurry. The curing time can be freely changed by the amount of the retarder added. The retarder can be delayed by suppressing the hydration of the cement when the hydrophobic group of the retarder adheres to the cement particles or hydrate when the cement comes into contact with water and undergoes a hydration reaction. However, since these cements and limes have alkalinity, there is a problem that, when supplied to the soil together with iron powder, the reaction between iron powder and VOC is hindered. Therefore, a retarder such as an organic acid such as amide polycarboxylic acids or citric acid, or a salt thereof can be supplied together with neutral calcined gypsum. In the case where the burned gypsum and the retarder are dispersed and supplied in a gas such as air or nitrogen, the setting time of the burned gypsum can be delayed by sufficiently stirring and mixing the soil, the burned gypsum, and the retarder. However, when the stirring and mixing is not sufficient, there are a portion that hardens immediately and a portion that is delayed, and the VOC cannot be sufficiently decomposed by iron powder in a portion that hardens immediately. There was a problem. In addition, although it becomes possible to spread to the soil and delay by adding a large amount of the retarder, there is a problem that the addition of a predetermined amount or more causes a significant delay and does not harden in some cases.

Japanese Patent Application No. 2003-251327 Japanese Patent Application No. 2004-261811 Gen Kimura, 5 others, “In-situ purification method of contaminated soil with volatile organochlorine compounds”, 9th Lecture Meeting on Groundwater / Soil Contamination and Prevention Measures, June 19-20, 2003, p. 38-39

  The present invention has been made in order to solve the above-described problems. The solidification of the soil by the solidification material is sufficiently delayed, the VOC is sufficiently decomposed and removed to purify the contaminated soil, and the ground strength of the original ground is improved. It aims at providing the soil improvement method which makes it possible to prevent the fall of soil and to improve a ground strength further.

  In the present invention, generally, the water-soluble polymer added for the purpose of allowing the baked gypsum and the wet soil not to have a aggregate structure and to have a property close to the soil disperses the iron powder and the baked gypsum. Even if it is supplied with gas, the solidification can be sufficiently delayed by suppressing the reaction between the calcined gypsum and the water in the soil, and the ground strength can be improved if dispersed in the soil. It was made by finding out.

That is, according to the present invention , a soil improvement method for purifying contaminated soil containing a volatile organic chlorine compound (VOC) and preventing a decrease in ground strength of the original ground,
Excavating the soil by rotating and lowering the excavating member having a cutting member and at least one injection pipe at the tip end thereof in a rotatable and supportable manner;
While rotating the excavating member, iron oxide powder containing iron powder or magnetite (Fe ₃ O ₄ ) and roasted gypsum in the air or nitrogen from the at least one injection pipe toward the soil around the excavating member; and a step for ejecting gas is dispersed a water soluble polymer seen including,
The water-soluble polymer is selected from polyacrylamide, sodium polyacrylate, acrylamide-sodium acrylate copolymer, and mixtures thereof;
When the iron powder is dispersed, the mass ratio of the calcined gypsum to the iron powder is in the range of 1: 1 to 10: 1, and the mass ratio of the calcined gypsum to the water-soluble polymer is 100: 0.1. It is compounded to be in a range of ˜100 : 2, and the iron powder is supplied to the soil 1 m ^{3 so} that 10 kg to 100 kg is supplied ,
When the iron oxide powder is dispersed, the amount of the calcined gypsum is 2 to 20 times the mass of the iron oxide powder, and the mass ratio of the calcined gypsum and the water-soluble polymer is 100: 0.1 to 100. : A soil improvement method is provided , wherein the gas is supplied such that the iron oxide powder is supplied in an amount of 15 kg to 150 kg with respect to 1 m ³ of the soil. .

According to the present invention , the excavation member includes a blade on a peripheral portion thereof, and further includes a step of rotating the excavation member by the support means and mixing the soil and the gas by the rotation of the blade. An improved method is provided.

According to the present invention , the excavation member is a soil improvement which is a stirring member including a cutting member at a tip portion, a blade at a peripheral portion, and at least one injection pipe disposed toward an edge of the blade. A method is provided.

According to the present invention , there is provided a soil improvement method, wherein the excavating step and the spraying step are performed simultaneously .

According to the present invention , there is provided a soil improvement method, wherein the excavating step, the spraying step, and the mixing step are performed simultaneously.

  By providing the soil improvement method of the present invention, even when a gas in which calcined gypsum is dispersed is used, the solidification rate can be sufficiently delayed, and VOC can be sufficiently decomposed and removed to purify contaminated soil. At the same time, it is possible to prevent a decrease in the earth bearing capacity of the original ground and further improve the earth bearing capacity. Moreover, VOC can be reduced more effectively by using the iron oxide powder containing the magnetite mentioned above, and the period for purification | cleaning can be shortened significantly compared with iron content.

  The soil improvement method of the present invention is a method for purifying contaminated soil containing a volatile organochlorine compound (VOC) and preventing a decrease in ground strength of the original ground. In the present invention, the contaminated soil is purified using a method of reducing and decomposing VOC using iron powder or iron oxide powder, and the method of adding a solidifying material is used to prevent a decrease in soil strength. The present invention is characterized in that iron powder or iron oxide powder and a solidifying material are supplied at the same time, and soil purification and ground strength prevention are performed simultaneously. As the solidifying material, cement and lime that exhibit high strength are generally used to improve the ground strength, but these are alkaline, and alkali inhibits the reaction between iron powder or iron oxide powder and VOC. Therefore, it cannot be used. Accordingly, neutral calcined gypsum is used in the present invention. This calcined gypsum has a solidification rate that is delayed as the moisture content increases, and the solidification rate is further delayed by being dispersed in water together with iron powder or iron oxide powder and supplied as a slurry. This delay suppresses the slurry from solidifying during the supply of the slurry to the soil and enables the slurry to be reliably supplied as a slurry. In the soil, the slurry penetrates the soil particles. Make it possible.

  As described above, when the slurry is supplied, the solidification rate can be delayed by changing the water content ratio. However, in the case of supplying by dispersing in dry air or nitrogen, the water content ratio cannot be increased, so that the above method cannot be adopted. Therefore, it is necessary to mix and supply a retarder that gives a retarding effect. When the retarder is mixed and supplied, if the soil, the calcined gypsum, and the retarder are sufficiently stirred and mixed, this retarder uniformly delays the hardening of the soil, and iron powder or iron oxide powder and VOC. Can be reacted. However, when not mixed with stirring, the baked gypsum and retarder are not evenly distributed in the soil, so it hardens rapidly in places where only burned gypsum is present, and is delayed in places where baked gypsum is present. It will be in the state where it does not harden in the place where a large amount exists.

  Therefore, in the present invention, a small amount of water-soluble polymer is added to air or nitrogen in addition to iron powder or iron oxide powder and calcined gypsum. In the present invention, in general, baked gypsum and wet soil do not have a aggregate structure, and are used as a water-soluble polymer added in a small amount for the purpose of making it close to soil, particularly as a polymer flocculant. It has been found that the water-soluble polymer can be delayed so that the reaction between the iron and the like and the VOC can be sufficiently performed and the strength can be improved even when the gas is supplied as a gas. . Hereinafter, the present invention will be described in detail.

As volatile organic chlorine compounds contained in the contaminated soil, trichlorethylene (TCE), tetrachloroethylene (TeCE), perchlorethylene (PEC), 1,1-dichloroethylene (DCE), trans-1,2-DCE, cis-1 , 2-DCE, 1,1,1-trichloroethane (TCEt), 1,1,2-TCEt, dichloromethane (DCM) and the like. Dioxins and residual agricultural chemicals are also present in the contaminated soil. These pollutants cause air pollution and need to be decomposed and removed so that they are not released into the atmosphere. Generally, it is reduced and decomposed by spreading iron powder or iron oxide powder in the soil, and finally decomposed into harmless gases such as carbon dioxide, chlorine gas and water. In the present invention, iron powder or iron oxide powder containing iron powder or magnetite (Fe ₃ O ₄ ) is sprayed with a gas in which air or nitrogen is dispersed, whereby iron powder or iron oxide powder is widely dispersed in the soil. Pollutants are decomposed by the reductive decomposition reaction, and the contaminated soil can be purified.

The iron powder used in the present invention may have any particle diameter as long as it can be dispersed and supplied in air or nitrogen. For example, the particle diameter is 0.05 μm to 150 μm. Things can be used. In the present invention, those having a small particle diameter that are easily dispersed in air or nitrogen are preferred. Moreover, as a state which supplies iron powder to soil, it is preferable to supply in the state containing air or nitrogen between the particle | grains of iron powder, and to inject it toward soil. The amount of iron powder to be sprayed may be any amount, but in order to give a sufficient purification action, it can be set to, for example, 10 kg to 100 kg per 1 m ^{3 of} soil. It is preferable that the iron powder has a non-constant particle size and a particle size distribution because air and nitrogen are easily contained between the particles and are easily dispersed. In the present invention, as the pressure of the gas is higher, iron powder is not deposited in the middle of the supply line. Moreover, in this invention, the ratio which mixes the iron powder with respect to contaminated soil changes also with the density | concentration of VOC in contaminated soil, and can mix an appropriate quantity. When supplying with iron, the supply amount of iron powder must be less than the lower explosion limit concentration that does not cause dust explosion, and the iron powder concentration in 1 m ^{3 of} air must be 0.1 kg or less. Don't be.

In the present invention, in addition to iron powder, iron oxide powder that is lightweight and can impart a higher purification action can be used. The iron oxide powder used in the present invention preferably contains about 70% by mass to about 90% by mass of magnetite (Fe ₃ O ₄ ). In addition, about another component, it can be set as pure iron (Fe), bivalent iron (Fe2 ⁺ ), etc., for example. As the divalent iron, divalent iron oxide (FeO) or the like can be used. In soil remediation using iron powder, when iron powder is mixed into contaminated soil, for example, TCE produces intermediate by-products such as cis-1,2-DCE, and finally, most of them decompose into ethylene and acetylene. However, when this iron oxide powder is used, decomposition does not stop at ethylene gas or acetylene gas, but the decomposition reaction proceeds to carbon dioxide gas. In the present invention, by using this iron oxide powder, by-products such as ethylene and acetylene are not generated in the purification treatment process, so that other processes and devices for treating these by-products are not required, and the treatment is performed. It is preferable to use this iron oxide powder because the period can be greatly shortened.

  As the iron oxide powder containing magnetite, one having an average particle diameter of 0.05 μm to 0.2 μm can be used. This iron oxide powder has a specific gravity of 4 to 5 smaller than that of iron powder with a specific gravity of 7.8, and by using the fine particle size described above, it can be easily dispersed in water to form a stable slurry. can do. The supply pressure may be any pressure as long as it can be supplied in a state dispersed in water, and can be supplied at a lower pressure than iron powder. Therefore, in the present invention, by using this iron oxide powder, a predetermined amount of iron oxide powder required for purification can be supplied with a smaller amount of water and at a low pressure.

In the present invention, the ratio of mixing the iron oxide powder for contaminated soil, varies depending on the concentration of volatile organic chlorine compounds in the contaminated soil, to soil 1 m ^3, it can be 15Kg～150kg. As the amount of iron oxide powder increases, more pollutants can be decomposed. However, since it is more expensive than iron powder, the cost is reduced and the amount of air or nitrogen accompanying the increase in iron oxide powder is reduced. In order to suppress a decrease in the earth bearing capacity due to the increase, the above value is preferable.

  Here, when the iron oxide powder is mixed so that the initial concentration of PCE is about 6000 ppm and has a pH of 7.5 containing 30% by mass of water so as to be 5% by mass, after 4 months, 20 to PCE can be decomposed to 30 ppm, can be decomposed to about 0.01 ppm after one month at an initial concentration of about 300 ppm, and can be decomposed to about 0.001 ppm after two weeks at an initial concentration of about 20 ppm. did it. Incidentally, in order to mix the same amount of iron powder and decompose to the above concentrations, a period of 10 times or more was required.

  In the present invention, neutral calcined gypsum is added to the gas in order to prevent a decrease in ground strength. By using the gas containing iron powder or iron oxide powder to which this calcined gypsum is added, in addition to the purification of contaminated soil, it is possible to prevent a decrease in ground strength of the ground that is softened by gas supply or stirring and mixing. This calcined gypsum does not exhibit strength compared to cement and lime, and is expensive, but it exhibits strength that can prevent a decrease in ground strength, and is alkaline that inhibits the reaction between iron powder or iron oxide powder and VOC. It is adopted because it does not have.

The calcined gypsum used in the present invention does not exhibit strength due to hydration reaction like cement, etc., so it develops strength immediately after mixing with soil, and is also applicable to ground with a high water content ratio can do. For example, after mixing for 3 days, a ground strength of about 0.5 MN / m ² can be obtained. As described above, when strength is developed immediately, sufficient agitation and mixing cannot be performed after feeding the soil. Therefore, in the present invention, a water-soluble polymer having a delay effect described below is added to the gas.

The calcined gypsum used in the present invention can be obtained by heat-treating calcium sulfate dihydrate (CaSO ₄ .2H ₂ O) at a low temperature. For example, waste sulfuric acid generated when producing titanium oxide by the sulfuric acid method is adjusted to pH 5 with calcium carbonate, and the product produced by setting the pH to 5 is 1 at 150 ° C. in a non-oxidizing atmosphere. It can be obtained by baking for a certain period of time. In the present invention, the mass ratio between the calcined gypsum and the iron powder can be determined by the amount of moisture in the soil, and can be, for example, 0.01: 1 to 200: 1. In the present invention, considering the amount of iron powder of 10 kg to 100 kg per 1 m ^{3 of} soil required for decomposing VOC, the mass of calcined gypsum and iron powder in order to obtain a predetermined strength and to carry out at low cost The ratio is preferably 1: 1 to 10: 1. For example, when the amount of calcined gypsum in the gas is large, the strength can be increased, but in order to supply this, it is necessary to increase the supply pressure of air or nitrogen, thereby enhancing the capacity of the supply means. A need arises and a lot of power is consumed. On the other hand, when the amount of calcined gypsum is small, the strength is insufficient. Therefore, the addition amount in the above range is preferable from the viewpoint of strength and equipment cost.

  The amount of calcined gypsum added when using the iron oxide powder is preferably the same as or more than the mass of the iron oxide powder, and more preferably 2 to 20 times. Moreover, the addition amount of baked gypsum can be determined by the amount of water supplied with iron oxide powder and this baked gypsum, and the amount of water contained in soil. The calcined gypsum used in the present invention is preferably in the form of powder dispersed in water.

  In the present invention, a small amount of a water-soluble polymer is added to air or nitrogen in addition to the iron powder or iron oxide powder and the calcined gypsum. A water-soluble polymer is a polymer that can be dissolved in water, and functions when added to water or water-containing dispersions, slurries, emulsion suspensions, pastes, thickeners, dispersants, It can be used as a fluidizing agent, lubricant, excipient, binder, adhesive, spreading agent, coating agent, water retention agent, gelling agent, and flocculant. In the ground improvement, a small amount of a water-soluble polymer is added as a polymer flocculant for the purpose that the calcined gypsum and wet soil do not have a aggregate structure and can be made to have properties similar to soil. In the present invention, it has been found that the addition of a small amount of this water-soluble polymer prevents the reaction between the calcined gypsum and water and delays solidification. In addition, it has also been found that when a slurry containing a water-soluble polymer is supplied into the soil, the ground strength can be increased as compared with the case where only burned gypsum is sprayed. This is because the water-soluble polymer gathers on the surface of the powder particles of the calcined gypsum and adheres so as to surround the surface, thus preventing the reaction between the calcined gypsum and water, that is, the reaction of hemihydrate gypsum to dihydrate gypsum. This is considered to be delayed. In addition, the water-soluble polymer is characterized by high mechanical strength because it has a chain-like molecular structure, and includes a polymer having high mechanical strength. Since it does not become a structure, it is considered that the soil containing this polymer solidified by calcined gypsum can impart a higher strength than the soil just sprayed with calcined gypsum. In addition, when the gas which does not add this water-soluble polymer is supplied, since the water content ratio of soil is low as mentioned above, it solidifies rapidly, and the decomposition reaction of VOC hardly progresses.

  The water-soluble polymer is preferably added in a small amount, for example, 0.01 to 2% by mass, based on the amount of calcined gypsum. The reason why the amount is small is that even if the amount is small, the above-mentioned delay effect and strength can be sufficiently increased, the property can be made close to the actual soil, and it is economically advantageous. For example, when a large amount of a water-soluble polymer such as 10% by mass is added, a large flock (aggregate) is formed in the middle of the supply line and deposited on the bottom of the line. This buildup clogs the line and interferes with the gas supply. Therefore, it must be a small amount as described above. In the present invention, the water-soluble polymer can also be used in the form of a powder, like calcined gypsum and iron powder. When the slurry to which about 1% by mass of the amount of calcined gypsum is added is supplied to the soil, the slurry can be delayed for about 1 hour as compared with the case where it is not added. Due to the delay of about 1 hour, iron powder and the like contained in the gas can be widely dispersed, and the VOC can be sufficiently brought into contact with iron powder or iron oxide powder to be decomposed and removed. By the way, when the baked gypsum is supplied to the soil as a powder, it solidifies within 30 minutes. Therefore, the addition of this water-soluble polymer will delay the solidification time by at least about 3 times.

  The water-soluble polymer used in the present invention is preferably an anionic, nonionic (nonionic), cationic or amphoteric polymer flocculant used as a polymer flocculant having an aggregating effect. For example, as anionic and nonionic, polyacrylamide, polyacrylic acid soda, copolymers thereof, polyacrylic acid soda salt, and as cationic ones, dimethylaminoacrylate, dimethylaminoethylmethacrylate Examples of the polyamidine, epoxyamine, and amphoteric ones include dimethylaminoethyl methacrylate. In the present invention, any kind of water-soluble polymer may be used as long as it surrounds the surface of the calcined gypsum particles in the slurry and can delay solidification, but it can delay and improve the strength. The polymer flocculant is preferable, and polyacrylamide is particularly preferable. Moreover, since polyacrylamide is used also as a thickener, when it disperses in soil, it can provide a ground which imparts viscosity and does not easily collapse.

  Next, the apparatus used in order to implement | achieve the soil improvement method of this invention is demonstrated. FIG. 1 is a diagram showing an outline of an apparatus used in the soil purification method of the present invention. The apparatus shown in FIG. 1 has a stirring member 4 provided with a cutting member 1 at the tip, a spiral blade 3 on the peripheral portion of the shaft body 2 and an injection pipe for injecting gas, and the stirring member 4 rotatably supported. And a support means 5 having a line connected to an injection pipe of the stirring member 4 and the like, and a mixture of iron powder or iron oxide powder and calcined gypsum and a water-soluble polymer are accommodated. The container 6 is configured to include a supply unit 7 for supplying air or nitrogen, a support unit 5 and a supply unit 7 to communicate with each other, and a line 8 that also communicates with the container 6. In the embodiment shown in FIG. 1, after excavating the soil while supplying compressed air from the supply means 7, the mixture is dropped from the lower part of the container 6 to disperse the mixture in the compressed air, and the mixture is dispersed. The injected gas is jetted from the stirring member 4 toward the surrounding soil, and the soil and the jetted mixture are stirred and mixed by the rotation of the stirring member 4.

  A stirring member 4 shown in FIG. 1 has a cutting member 1 for excavating soil at a tip portion facing in the excavation direction, and a shaft body 2 that allows compressed air to be injected from the tip portion in the excavation direction. And the spiral blade 3 provided around the shaft body 2 that enables smooth excavation and enables the agitation of the soil, and the spiral so as to penetrate from the inside of the shaft body 2 to the outside. And at least one injection pipe (not shown) disposed toward the edge of the blade 3. The agitating member 4 is connected to the rod 9 and can excavate the soil and agitate the soil by rotating and raising and lowering the rod 9. Injecting compressed air through the shaft body 2 in order to reduce the impact on the ground during excavation, to give the agitating member 4 a rocking agitation effect to facilitate excavation, and to suppress heat generation during excavation of the cutting member 1 Can be done. This compressed air is supplied from the supply means 7 through a line (not shown). In addition, in order to purify the soil by allowing the mixture to spread over a wide range in the soil, gas can be injected from the injection pipe toward the soil together with the stirring of the soil by the spiral blade 3. The agitating member 4 can change the direction of rotation so as not to discharge soil during descent during excavation and during ascending and descending during agitation. The details of the stirring member 4 will be described below with reference to FIG.

  The support means 5 shown in FIG. 1 supports the traveling unit 10, the rod 9, the clamping unit 11, the arm 9 that supports the rod 9 and allows the angle of the rod 9 to be changed, and the elevation that enables the rod 9 to be raised and lowered. And means 13. The traveling unit 10 moves to the soil position to be purified and allows the position to be changed. The rod 9 enables rotation and elevation of the stirring member 4 disposed at the lower end facing the ground. The clamping part 11 clamps the rod 9 so as to be movable and rotatable. The clamping unit 11 is capable of rotating the rod 9 in both forward and reverse directions by hydraulic drive or the like.

  The rod 9 shown in FIG. 1 includes a line for connecting the line 8 and the line 13 and connecting the shaft body 2 of the stirring member 4 and the injection pipe. Moreover, the rod 9 can connect another rod according to the depth of the soil.

  A container 6 shown in FIG. 1 contains a mixture of iron powder or iron oxide powder, calcined gypsum, and a water-soluble polymer, and is provided to disperse the mixture in air or nitrogen flowing through the lower line 8. It is done. The mixture accommodated in the container 6 is discharged from the lower part through a valve and dispersed in air or nitrogen supplied from the supply means 7. In the present invention, a scale for measuring the mass of the container 6 is installed, and by measuring the mass of the container 6, the opening of the valve can be adjusted, and the amount of the mixture to be supplied can be adjusted.

  In the present invention, the container 6 may have any capacity and may have any shape. Moreover, the container 6 can use steel hoppers, such as stainless steel, for example. In addition, when the free fall from the container 6 is insufficient, a lid can be provided on the top of the container 6 to pressurize the inside of the container 6. Moreover, the container 6 can be equipped with a vibrator, and clogging with a valve etc. can be eliminated. As the supply means 7, an air compressor can be used when air is supplied, and a nitrogen cylinder or a nitrogen curdle can be used when nitrogen is supplied.

  FIG. 2 is a diagram illustrating a stirring member used in an apparatus that can be used in the present invention. FIG. 2A shows a perspective view of the stirring member 4, and FIG. 2B shows a cross-sectional view. The stirring member 4 shown in FIG. 2 includes a tip 20 having a cutting member 1 at the tip, and a hollow shaft body 2 in which the diameter at the center along the length direction is increased and the diameter at both ends is decreased. The spiral blade 3 provided around the outer surface of the shaft body 2, the plurality of projecting members 21 provided on the upper and lower surfaces of the spiral blade 3, and the diameter of the shaft body 2 in the length direction are increased. In the center part, it is composed of two injection pipes 22 and 23 that pass through the shaft body 2 and are arranged toward the edge of the spiral blade 3. In the present invention, one injection tube or three or more injection tubes may be used.

  The tip conduit 20 shown in FIG. 2 is connected to the shaft body 2 using a connecting member such as a flange 24, and the cutting member 1 is provided at the tip. Further, the cutting member 1 a is also provided on the flange 24 so as to face the same direction as the direction of the cutting member 1. The cutting member 1, 1 a shown in FIG. 2 has a sharply pointed tip, can cut hard soil, stone, etc., and is welded to the tip of the tip conduit 20 and the flange 24. Can be joined together. The tip conduit 20 shown in FIG. 2 may be a pipe having any diameter and length, but can have the same diameter as that of both end portions of the shaft body 2. The shape, structure and material of the cutting members 1 and 1a may be any as long as they can excavate the soil appropriately. Further, any number of the cutting members 1 and 1a may be provided at the distal end portion of the leading conduit 20 and the flange 24.

  The shaft body 2 shown in FIG. 2 has a shape in which the diameter of the central part is increased, the diameter is constant at a predetermined length of the central part, and the diameter decreases at a constant rate toward both ends. It is said that. Moreover, it is hollow and a part of injection | pouring pipes 22 and 23 for supplying and injecting gas inside is inserted. Compressed air is allowed to flow in the space excluding the injection pipes 22 and 23, and a shaft body is mainly used to facilitate excavation by providing a lubricant effect that allows the excavated soil to flow smoothly. Compressed air is injected from the tip through the inside of 2. In addition, the jet of compressed air can reduce the impact on the ground during excavation, give the stirring member 4 a rocking stirring effect, further facilitate excavation, and suppress the heat generation of the cutting member 1. . In the present invention, for example, the shaft body 2 has a constant diameter of 0.8 m in the entire length of 0.8 m, a length of 0.4 m in the center length of 0.16 m, and 0 in the range of both end portions in the length direction of 0.32 m. A structure that is enlarged at a constant rate from a diameter of .14 m to 0.4 m can be obtained. In this case, the taper angle that expands at a constant rate is 22 °.

  The shaft body 2 shown in FIG. 2 is provided with a spiral blade 3 formed in a spiral shape on the outer surface. The spiral blade 3 is formed so that the diameter of the spiral blade 3 increases toward the center of the shaft body 2, and a plurality of projecting members 21 are provided on the upper and lower surfaces of the spiral blade 3. . Similar to the shaft body 2, the spiral blade 3 is formed so that the diameter of the blade increases from both end portions in the length direction of the shaft body 2 toward the center portion, and smoothly moves up and down in the soil. The structure can be agitated.

  The protruding member 21 shown in FIG. 2 has a rectangular plate shape, and is disposed so that the rectangular surface faces the shaft body 2. Further, the protruding member 21 is provided at the edge of the spiral blade 3 and the inner edge near the shaft body 2, and has a structure in which a rectangular corner is chamfered. By adopting a structure in which the corners on the side facing the rotation direction of the rectangular plate-shaped protruding member 21 are chamfered, the rotation of the spiral blade 3 can be made smooth and effectively stirred. In the stirring member 4 shown in FIG. 2, when excavating soil, the protruding member 21 provided on the lower surface of the spiral blade 3 sharply impregnates the soil while effectively stirring the soil, and the protruding member 21 provided on the upper surface. Can smoothly feed the cut and agitated earth and sand, and even if the soil contains stones and the like, it is difficult to chew. Further, when the stirring member 4 is raised from the ground toward the ground surface, the protruding member 21 provided on the upper surface of the spiral blade 3 effectively cuts and stirs, and the protruding member 21 provided on the lower surface. Can smoothly send earth and sand backwards. Therefore, when excavating soil using the stirring member 4 shown in FIG. 2, the excavated earth and sand are not discharged to the ground. In the present invention, any number of the projecting members 21 may be provided, and the shape is not the above-described rectangular plate shape, and the rectangular plate is bent along the spiral shape of the spiral blade 3. May be. In the present invention, in order to raise the stirring member 4 smoothly, it is preferable to change the rotation direction of the rod 9.

  In the hollow portion of the shaft body 2 shown in FIG. 2, a part of the injection tubes 22 and 23 is inserted as described above, and the hollow portion of the shaft body 2 other than the injection tubes 22 and 23 receives compressed air. It can be passed. The injection tubes 22 and 23 shown in FIG. 2 are bent vertically at the central portion in the longitudinal direction of the shaft body 2, penetrate the shaft body 2, and toward the edge of the spiral blade 3. It has an extended structure. Further, the injection tubes 22 and 23 are 180 in the circumferential direction from the back surface of one surface of the injection tube 23, that is, the position where the injection tube 22 protrudes, so that the injection tube 22 penetrates one surface of the shaft body 2. It is provided at an angle of °. In the present invention, in order that the gas containing the mixture can be sprayed over a wide range in the soil, the longer the length of each of the injection tubes 22 and 23 protruding from the shaft body 2 along the spiral blade 3, the longer the length. preferable. However, when projecting from the edge of the spiral blade 3, the projecting portion directly contacts the soil and may be damaged such as bending, so the length to the edge of the spiral blade 3 is at most. It is preferable. The diameters of the injection tubes 22 and 23 may be any diameter, and for example, those having a diameter of 1 inch to 1.5 inches can be used.

  In the present invention, the injection tubes 22 and 23 do not have to extend to the edge of the spiral blade 3, and may be up to the center or inner edge of the spiral blade 3. When this stirring member 4 is used as an excavation member, the mixture and the soil can be mixed by the spiral blade 3, so that it is possible to simply supply a gas containing this mixture. It is preferable to inject and inject from the injection pipes 22 and 23.

  Not only the agitating member described above but also soil can be improved by using other members as excavation members. 3 and 4 illustrate other drilling members. FIG. 3 shows a drilling member having a cutting member and at least one injection pipe at the tip, FIG. 3 (a) is a perspective view of the drilling member, and FIG. 3 (b) is the drilling thereof. Sectional drawing of a member is shown, respectively. In the excavating member 30 shown in FIG. 7, a plurality of cutting members 32 are provided at the distal end portion of a hollow rod-shaped rod 31, a hole 33 having a predetermined diameter is provided at a predetermined position, and an injection tube 34 having a distal end inserted through the hole 33. Is arranged. The hollow rod-like rod 31 is connected to a support means (not shown) directly or connected to another rod supported by the support means, and is rotated and lowered by the support means to excavate the soil using the cutting member 32 at the tip. Have been able to. When excavating the soil, compressed air or water is supplied between the rod 31 and the injection pipe 34 and can be excavated while being injected from the tip of the rod 31. By doing so, it is possible to provide a lubricant effect that allows the excavated soil to flow smoothly, reduce the impact on the ground during excavation, facilitate excavation, and suppress the heat generation of the cutting member 32.

The injection tube 34 shown in FIG. 3 is inserted into the hollow rod 31 along the length direction of the rod 31, and the tip is bent in the direction perpendicular to the length direction of the rod 31. The hole 33 is inserted. In the embodiment shown in FIG. 3, the tip of the injection tube 34 and the outer wall of the rod 31 are configured to be substantially flush with each other. However, in the present invention, the injection tube 34 is separated from the rod 31. You may be comprised so that it may extend. In the embodiment shown in FIG. 3, the number of injection tubes 34 is one. However, two or more injection tubes 34 can be provided, and in the case of two, one extends in a predetermined direction. The book can be configured to extend in the direction of 180 ° with respect to one injection tube. In the embodiment shown in FIG. 3, as described above, the rod 31 is rotated by supporting means (not shown) and lowered to excavate the soil, into the injection pipe 34 inside the rod 31, in compressed air or nitrogen, Supplying a gas in which iron oxide powder containing iron powder or magnetite (Fe ₃ O ₄ ), calcined gypsum, and a water-soluble polymer are dispersed, and injecting the rod 31 toward the surrounding soil while raising the rod 31 it can. In the present invention, not limited to this, gas can be injected at the time of excavation, and gas can be injected from the injection pipe 34 toward the soil at the same time as excavation. In addition, gas can be supplied by being injected into the soil both during excavation and when the rod 31 is raised. In addition, the supply pressure of gas can be supplied with the pressure of about 0.7 Mpa similar to the case where the stirring member mentioned above is used.

  In the embodiment shown in FIG. 3, iron powder or iron oxide powder, calcined gypsum, and water-soluble polymer are dispersed and supplied in compressed air or nitrogen, and sprayed to disperse them widely in the soil. Can be made. Since this gas contains a water-soluble polymer, it is possible to surround the calcined gypsum particles, delay the solidification, and sufficiently decompose the VOC with iron powder or iron oxide powder. In addition to solidification with calcined gypsum, ground strength can also be improved by agglomeration with water-soluble polymers. In the present invention, the rod 31 is, for example, a 2-5 inch steel pipe, and the cutting member 32 shown in FIG. Can be used as a drilling member.

  FIG. 4 shows an excavation member in which blades are further provided around the rod shown in FIG. 4, the excavation member 40 is provided with a cutting member 42 at the tip of a hollow rod-like rod 41, a hole 43 is provided in the peripheral portion thereof, and an injection pipe through the hole 43, like the excavation member 30 shown in FIG. 44, and blades 45a, 45b, 45c, 45d are provided around the rod 41. By rotating the blades 45a, 45b, 45c, 45d, soil, iron powder or iron oxide powder, Gypsum and water-soluble polymers can be mixed. In the embodiment shown in FIG. 4, the blades 45 a, 45 b, 45 c, and 45 d are plate-shaped, and in the length direction of the rod 41 so that they can be smoothly inserted into the soil with respect to the rotation direction of the rod 41. It is not perpendicular to the surface but is inclined by 10 ° to 45 ° when the vertical direction is 0 °, and the surfaces of the blades 45a, 45b, 45c and 45d are also inclined. In the case where the rod 41 rotates counterclockwise, the blades 45a, 45b, 45c, and 45d viewed from the rod 41 side can be all inclined such that the left side is lower than the right side. The inclination of the surface can be set to 5 ° to 30 °, for example.

  Further, in the embodiment shown in FIG. 4, the blades 45 a and 45 b disposed on the excavation direction side, that is, the side on which the cutting member 42 of the rod 41 is provided, have the cutting member provided on the tip portion of the rod 41. The cutting member 46 similar to 42 is provided, and the soil can be excavated by the blades 45a and 45b during excavation. The rod 41 is supported by support means (not shown), and can be excavated by being rotated and lowered by the support means. In the embodiment shown in FIG. 4, the soil can be excavated by the cutting member 42 provided at the tip of the rod 41 and the cutting member 46 provided on the blades 45a and 45b. As described above, the gas injection can be performed during excavation and / or when the rod 41 is raised. In the embodiment shown in FIG. 4, the rotation of the blades 45a, 45b, 45c, and 45d allows the gas to be injected into the surrounding soil while stirring, thereby mixing the soil and the gas. Note that the rotation directions of the blades 45a, 45b, 45c, and 45d during excavation and ascending may be the same or reverse. Further, the gas supply pressure can be supplied at a pressure of about 0.7 MPa, which is the same as in the case where the above-described stirring member is used.

  As in the embodiment shown in FIG. 3, the embodiment shown in FIG. 4 supplies iron powder or iron oxide powder, calcined gypsum, and a water-soluble polymer dispersed in compressed air or nitrogen, and injects it. Therefore, it can be widely dispersed in the soil. In the embodiment shown in FIG. 4, since the excavation member 40 includes blades 45a, 45b, 45c, and 45d, iron powder or iron oxide powder, calcined gypsum, water-soluble polymer, and soil can be sufficiently mixed. . Thereby, iron powder etc. will be in the state uniformly disperse | distributed in soil, the contaminated soil can be purified more effectively, and the ground which improved the intensity | strength compared with the original ground can be obtained. . In the present invention, the blades 45a, 45b, 45c, 45d are steel plates of a predetermined length and thickness, or have a predetermined length and are sharpened at one end so that they can be easily inserted into soil during excavation. It is possible to use a steel plate formed so as to increase in thickness toward the surface and welded to a predetermined position of the rod 41 so as to have the above-mentioned predetermined angle.

  FIG. 5 illustrates an apparatus that supplies air in a dispersed manner and will be described in detail. The apparatus shown in FIG. 5 includes a container 51 that contains a mixture 50 of iron powder or iron oxide powder, calcined gypsum, and a water-soluble polymer, and a valve 52 that discharges a predetermined amount of the mixture from the container 51. The In order to supply the mixture 50 using the air supply means 53 that supplies air at the time of excavation, the line connected to the air supply means 53 is branched into a line 54 and a line 55. Are connected via a valve 52.

  The air supply means 53 sucks air, compresses it to a predetermined pressure, and separates moisture through an adsorption layer filled with a drain separator, an adsorbent such as activated alumina, silica gel, or synthetic zeolite. Supply air with water separation. The reason why air separated in this way is used is to prevent iron powder from being oxidized and rusting during gas supply. This rust reduces the reductive decomposition action.

  At the time of excavation, air is sent to the rod 9 shown in FIG. 1 through the line 54, and the air sent to the rod 9 is jetted from the tip of the stirring member 4 shown in FIG. 1 to give a lubricant effect. Further, even after excavation is completed, air is continuously supplied in order to smoothly raise the stirring member 4 shown in FIG. 1 and prevent soil from entering the shaft body 2 shown in FIG. 1 from the tip. The When the excavation is completed, air is also supplied to the line 55, the valve 52 of the container 51 is opened, and the mixture is dropped and dispersed in the air. The gas in which the mixture is dispersed is sent to the rod 9 shown in FIG. 1 through the line 55 and sent to the injection pipes 22 and 23 of the stirring member 4 shown in FIG. 2 and directed from the injection pipes 22 and 23 to the surrounding soil. Is injected.

The supply amount of the mixture obtained by mixing iron powder or iron oxide powder, calcined gypsum, and water-soluble polymer can be adjusted using a scale that measures the mass of the container 51 and the valve 52. For example, when supplying a mixture of a predetermined amount of soil 1 m ^3, the soil 1 m ³ and a rising speed of the rod 9 shown in agitation mixing area and Figure 1 which is represented by a circle in FIG. 6 of the stirring member 4 shown in FIG. 1 The time for stirring and mixing is obtained, and the opening of the valve 52 is adjusted so that a predetermined amount of the mixture is supplied into the air within that time. The mass of the supplied mixture can be confirmed with a scale. For example, assuming that the stirring and mixing region is a circle having a diameter of about 1 m, the rising speed of the rod is about 0.15 m / min, and about 200 kg of the mixture needs to be supplied to 1 m ³ of soil, about 8.5 About 200 kg of mixture must be supplied per minute. The opening degree of the valve 52 can be adjusted to a desired opening degree immediately by testing and marking in advance.

  The container 51 is a hopper whose cross section is reduced toward the lower part, and since the valve 52 is provided, the container 51 is easily clogged. Supply and stop of compressed air is performed through a line 56 connected to the upper part of the container 51. The clogging can be eliminated by repeating the pressurization and depressurization in 51. The supply and stop of compressed air can be performed by opening and closing a valve (not shown).

  Here, the soil improvement method of this invention is demonstrated using the apparatus shown in FIG. 1 using the stirring member shown in FIG. First, the rod 9 is arranged at a position to be purified by the traveling unit 10, and the arm 12 is used to adjust the rod 9 to be perpendicular to the ground. Since the original ground has not yet been implemented, it has sufficient strength even if the device is placed on the ground. The rod 9 is rotated by the holding part 11 and the rod 9 is lowered by the lifting means 13 to excavate the soil. The excavation of the soil can be performed using the cutting member 1 provided at the tip of the stirring member 4. In addition, it is supplied through a line (not shown) in order to provide a lubricant effect for smoothly flowing the excavated soil, to reduce the impact on the ground during excavation, and to give the agitating member 4 a rocking agitation effect to facilitate excavation. Compressed air is supplied from the means 7. The compressed air is injected from the tip through the line in the rod 9 and the shaft 2 of the stirring member 4.

  In the present invention, a hole to the extent that the stirring member 4 enters is excavated in advance, and the earth and sand generated by the excavation are temporarily placed in another place so that the earth and sand rising during the excavation by the stirring member 4 does not overflow from the hole. It can also be. The temporarily placed earth and sand can be backfilled by adding a predetermined amount of iron powder or iron oxide powder, calcined gypsum, and water-soluble polymer using a backhoe or the like, mixing, and mixing.

  Next, after excavating the soil to a predetermined depth, the direction of rotation of the rod 9 by the clamping unit 11 is changed. Until the gas is supplied, the rod 9 can be stopped without being raised, or the rotation of the rod 9 can be stopped. A mixture of iron powder or iron oxide powder, calcined gypsum, and water-soluble polymer is dropped from the container 6 into the air or nitrogen supplied from the supply means 7, and is sent to the stirring member 4 in a dispersed state.

  If the gas containing a mixture is supplied to the stirring member 4, as shown in FIG. 1, it will inject toward each soil from each injection pipe. The gas is continuously jetted in the circumferential direction of the spiral blade 3, and is stirred and mixed with the soil by the rotating spiral blade 3. The gas supply and the stirring by the spiral blade 3 are continuously performed while the stirring member 4 is raised at a predetermined speed by the lifting means 13. By doing so, iron powder, iron oxide powder, calcined gypsum, and water-soluble polymer can be uniformly dispersed in the soil up to a predetermined depth in the original position without accompanying soil. In the present invention, in order to sufficiently mix the soil, iron powder or iron oxide powder and calcined gypsum and water-soluble polymer, it is preferable that the rising speed is small, but if it is too small, the working efficiency is reduced, for example, , 0.05 m / min to 0.3 m / min. In the present invention, the slurry can be supplied not only when the rod 9 is lifted but also when excavating and sprayed toward the surrounding soil, and the slurry can be supplied and sprayed both when excavating and when rising. You can also

  When the stirring member 4 rises to near the ground surface, the supply means 7 is stopped. After the stirring member 4 is further raised and the stirring member 4 is separated from the ground surface, it is moved to the next purification position by the traveling unit 10, and again as described above, excavation, gas supply and injection, stirring It can be performed. For example, in the rectangular purification range shown in FIG. 6, the soil purification has a range indicated by a circle in which iron powder or iron oxide powder and calcined gypsum and a water-soluble polymer are supplied, stirred and mixed at a time. It is preferred that they are selected to overlap. The range of supply and mixing of iron powder or iron oxide powder, calcined gypsum and water-soluble polymer is a circular range having a diameter several tens of centimeters larger than the diameter of the spiral blade 3. In FIG. 6A, in order to completely decompose and remove the VOC, positioning is performed so that there is no range where iron powder or iron oxide powder is not supplied. The rod 9 is positioned at the center of each circle, and excavated, stirred, and mixed by the stirring member 4 so that iron powder or iron oxide powder, calcined gypsum, and water-soluble polymer are mixed in the circular range. . When the range ends, the rod 9 is moved to the center of the range indicated by the adjacent circle, and excavation, supply of iron powder or iron oxide powder and calcined gypsum and water-soluble polymer, and mixing with soil are performed again. In FIG. 6A, the range in which the iron powder or iron oxide powder, the calcined gypsum, and the water-soluble polymer are already supplied and the range in which the supply is performed later are positioned so as to largely overlap each other.

  In FIG. 6A, the overlapping range of the circular ranges is large, but in FIG. 6B, positioning is performed so that the circular ranges are adjacent to each other. This is because the range already solidified by the gypsum that has already been supplied to the soil and stirred and mixed will be stirred and mixed again, so that it will not be possible to obtain the predetermined ground strength, so do not perform the range that has already been treated. Is positioned adjacent to In this case, there is a range in which iron powder or iron oxide powder and calcined gypsum and water-soluble polymer are not supplied, but iron powder or iron oxide powder, calcined gypsum and water-soluble polymer are around the spiral blade 3. As a result, the range in which the iron powder or iron oxide powder and the calcined gypsum and the water-soluble polymer are not supplied is small. In the present invention, if sufficient and uniform mixing is possible, it is preferable to reduce the number of times of excavation, and therefore it is preferable to position as shown in FIG.

FIG. 7 shows the relationship between the amount of baked gypsum added and the corn index, and the water-solubility of about 1% by mass with respect to the amount of baked gypsum added for each moisture content expressed as a percentage of the mass of moisture relative to the mass of dry soil A case where a polymer is added and a case where a polymer is not added will be described. The ordinate indicates the corn index (kN / m ² ), and the abscissa indicates the amount (kg) of baked gypsum added to 1 m ³ of soil. In addition, iron oxide powder containing magnetite was added to the soil in an amount of about 1/10 to 1/7 of the amount of roasted gypsum, and polyacrylamide was added as a water-soluble polymer. In FIG. 7, the moisture content 60% is indicated by a circle, 80% is indicated by a rectangle, 100% is indicated by a triangle, those containing polyacrylamide are outlined, and those not containing are filled. The cone index is a value obtained by dividing the penetration resistance of the cone by the bottom area of the cone, and is a measure that allows the construction machine to run several times. For example, an ordinary bulldozer (about 21 tons) requires a cone index of 0.7 MN / m ² , a small self-propelled scraper of 1.0 MN / m ² , and a dump truck of about 1.2 MN / m ² . As shown in FIG. 7, it was found that the corn index decreased as the water content ratio increased, and increased as the amount of calcined gypsum added increased. For example, at a water content ratio of 100%, increasing the amount of calcined gypsum does not significantly increase the corn index, but at a water content ratio of 60%, the corn index is greatly increased by increasing the amount of addition. I was able to. Moreover, when polyacrylamide was added, it was found that the corn index was increased by about 10% at any water content ratio. As described above, it is considered that polyacrylamide has a large mechanical strength, and that the strength can be increased by suppressing the agglomeration by the addition of polyacrylamide. As a result, it was found that the ground strength can be increased by adding a small amount of water-soluble polymer.

  Although the present invention has been described in detail with the embodiment described above, the soil improvement method of the present invention is not limited to the embodiment described above, and can obtain the same effect, The stirring member is not limited to the shape described above, and may have any size, the number of turns of the spiral blade, the position where the iron powder and oxidant injection pipes are disposed, and the container may have any shape and structure. The blending ratio of iron powder or iron oxide powder, water, and calcined gypsum can be set to an appropriate value depending on the moisture content of the soil, the mass of the soil to be purified, and further the cost. Furthermore, although it is preferable to rotate the rod reversely during excavation and when the rod is raised, it can also be in the same direction of rotation.

  Further, in the excavation member used in the embodiment shown in FIG. 4, the length, width, thickness, number, and inclination angle of the blades 45a, 45b, 45c, 45d are the strength of the ground to be excavated, slurry or gas is injected. In consideration of the range to be mixed, the size, number, and angle can be set appropriately. The injection tube 44 may be provided so as to be adjacent to the blades 45a and 45b and extend along the direction protruding from the rod 41, that is, along the length direction of the blades 45a and 45b. , 45b instead of the blades 45c and 45d and extending along the length direction of the blades 45c and 45d. In the present invention, in order to obtain a sufficient purification effect and ground strength with a small amount of iron powder or iron oxide powder and calcined gypsum, the excavation member preferably has blades, and the stirring member is more preferable.

The figure which illustrated the apparatus which implement | achieves the soil improvement method of this invention. The figure which illustrated the stirring member which can be used for the apparatus which implement | achieves the soil improvement method of this invention. The figure which showed 1st Embodiment of the excavation member which can be used for the apparatus which implement | achieves the soil improvement method of this invention. The figure which showed 2nd Embodiment of the excavation member which can be used for the apparatus which implement | achieves the soil improvement method of this invention. The figure which illustrated the apparatus distributed and supplied to air. The figure which showed each position which excavates soil using the apparatus shown in FIG. 1 and FIG. 2, injects slurry, and mixes soil and slurry. The figure which showed the relationship between the addition amount of grilled gypsum and the corn index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ... Cutting member 2 ... Shaft body 3 ... Spiral blade 4 ... Stirring member 5 ... Support means 6 ... Container 7 ... Supply means 8 ... Line 9 ... Rod 10 ... Traveling part 11 ... Nipping part 12 ... Arm 13 ... Elevating Means 14 ... line 20 ... tip conduit 21 ... projecting members 22, 23 ... injection pipe 24 ... flange 30, 40 ... excavation members 31, 41 ... rods 32 and 42 ... cutting members 33 and 43 ... holes 34 and 44 ... injection pipe 45a 45b, 45c, 45d ... blade 46 ... cutting member 50 ... mixture 51 ... container 52 ... valve 53 ... air supply means 54, 55, 56 ... line

Claims (5)

A soil improvement method for purifying contaminated soil containing volatile organochlorine compounds (VOC) and preventing a decrease in the ground strength of the original ground,
Excavating the soil by rotating and lowering the excavating member having a cutting member and at least one injection pipe at the tip end thereof in a rotatable and supportable manner;
While rotating the excavating member, iron oxide powder containing iron powder or magnetite (Fe ₃ O ₄ ) and roasted gypsum in the air or nitrogen from the at least one injection pipe toward the soil around the excavating member; and a step for ejecting gas is dispersed a water soluble polymer seen including,
The water-soluble polymer is selected from polyacrylamide, sodium polyacrylate, acrylamide-sodium acrylate copolymer, and mixtures thereof;
When the iron powder is dispersed, the mass ratio of the calcined gypsum to the iron powder is in the range of 1: 1 to 10: 1, and the mass ratio of the calcined gypsum to the water-soluble polymer is 100: 0.1. It is compounded to be in a range of ˜100 : 2, and the iron powder is supplied to the soil 1 m ^{3 so} that 10 kg to 100 kg is supplied ,
When the iron oxide powder is dispersed, the amount of the calcined gypsum is 2 to 20 times the mass of the iron oxide powder, and the mass ratio of the calcined gypsum and the water-soluble polymer is 100: 0.1 to 100. : it is blended so that the second range, the relative iron oxide powder is the soil 1 m ^3, wherein the gas to be 15kg~150kg supply is supplied, soil improvement method. The wear member has peripheral portion provided with vanes to rotate the該掘cutting member by said supporting means, further comprising the step of mixing the gas with the soil by the rotation of the blades, according to claim 1 Soil improvement method. The soil according to claim 2 , wherein the excavation member is a stirring member including a cutting member at a tip portion, a blade at a peripheral portion, and at least one injection pipe disposed toward an edge of the blade. Improvement method. The soil improvement method according to any one of claims 1 to 3 , wherein the excavating step and the jetting step are performed simultaneously. Wherein the steps of the mixing step to the injection step of the excavation are performed simultaneously, soil improvement process according to claim 1 or 2.

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