JP6989083B2 - Ground improvement structure - Google Patents

Description

The present invention relates to a ground improvement structure.

A grid-like ground improvement body formed in a grid pattern in a plan view is known (see, for example, Patent Document 1).

Japanese Patent No. 5919429

By the way, as a method for purifying contaminated ground, an injection liquid containing an activator or the like that proliferates and activates microorganisms that decompose pollutants in the contaminated ground (hereinafter referred to as "degrading microorganisms") is applied from the injection well to the contaminated ground. The method of injecting is known. In this type of purification method, an impermeable wall surrounding the contaminated ground is constructed in the ground in order to suppress the diffusion of pollutants.

Here, it is conceivable to use the above-mentioned grid-like ground improvement body as the impermeable wall.

However, in the grid-like ground improvement body, the ground is divided into a plurality of areas (hereinafter, referred to as "partition areas"). Therefore, for example, when the contaminated ground spans a plurality of compartment areas, an injection well must be provided in each compartment area, which may increase the construction cost.

Further, for example, when the contaminated ground is in a deep layer of the ground, if the grid-like ground improvement body is formed so as to reach the contaminated ground, the construction amount of the grid-like ground improvement body may increase and the construction cost may increase.

An object of the present invention is to reduce the construction cost in consideration of the above facts.

The ground improvement structure according to the first aspect is a ground improvement body having a partition wall portion for partitioning the ground into a plurality of section areas, an injection well provided in the section area, and one said section provided with the injection well. It is provided on the partition wall portion between the region and the other compartment area, and includes a water passage portion through which groundwater passes.

According to the ground improvement structure according to the first aspect , the ground improvement body has a partition wall portion for partitioning the ground into a plurality of partition areas. In addition, an injection well is provided in the compartment area.

Here, if there is no water passage in the compartment wall between one compartment area where the injection well is provided and the other compartment area, the injection liquid is injected into one compartment area and another compartment area. In order to do so, it is necessary to provide injection wells in one compartment area and another compartment area, respectively.

On the other hand, in the present invention, a water passage portion for passing groundwater is provided in the compartment wall portion between one compartment area where the injection well is provided and the other compartment area. As a result, the injection liquid injected from the injection well into one compartment region is supplied to the other compartment region via the water passage portion. Therefore, in the present invention, injection wells in other compartments can be omitted. Therefore, in the present invention, the number of injection wells can be reduced.

The ground improvement structure according to the second aspect includes a pumping well provided in the other section area in the ground improvement structure according to the first aspect.

According to the ground improvement structure according to the second aspect , a pumping well is provided in the other section area. From this pumping well, groundwater from other compartments containing contaminants is pumped.

Here, a water passage portion for passing groundwater is provided in the compartment wall portion between one compartment area where the injection well is provided and the other compartment area. As a result, the groundwater of one compartment area flows into the other compartment area through the water passage portion. Therefore, groundwater in one section area can also be pumped from a pumping well provided in another section area. Therefore, in the present invention, the number of pumping wells can also be reduced.

The ground improvement structure according to the third aspect includes a small section area, a ground improvement body that divides the ground into a large section area wider than the small section area, and an injection well provided in the large section area.

According to the ground improvement structure according to the third aspect , the ground improvement body divides the ground into a small section area and a large section area wider than the small section area. In addition, an injection well will be provided in the large compartment area.

Here, for example, when the areas of the ground compartments are all the same, the contaminated ground tends to span a plurality of compartments. In this case, since it is necessary to provide injection wells in each of a plurality of compartments over the contaminated ground, the number of injection wells increases.

On the other hand, in the present invention, by forming a large section area according to the size of the contaminated ground, it is possible to prevent the contaminated ground from straddling a plurality of section areas. Therefore, in the present invention, the number of injection wells can be reduced as compared with the case where the area of the partition area is the same.

The ground improvement structure according to the fourth aspect includes a pumping well provided in the large section area in the ground improvement structure according to the third aspect.

According to the ground improvement structure according to the fourth aspect , a pumping well is provided in the large section area. From this pumping well, groundwater and the like in a large plot area containing pollutants are pumped up.

Therefore, in the present invention, it is possible to reduce not only the number of injection wells but also the number of pumping wells by forming a large section area according to the size of the contaminated ground.

The ground improvement structure according to the fifth aspect is formed by forming a ground improvement body that divides the ground into a plurality of compartmental areas and extending a part of the ground improvement body downward to surround the ground below the ground improvement body. It is provided with an extension portion and an injection well provided in the ground surrounded by the extension portion.

According to the ground improvement structure according to the fifth aspect , the ground improvement body divides the ground into a plurality of division areas. In addition, the ground improvement body is provided with an extension portion. The extension portion is formed by extending a part of the ground improvement body downward. The extension of the ground improvement body suppresses the diffusion of groundwater containing pollutants, for example, by surrounding the contaminated ground below the ground improvement body.

In addition, the injection well is provided in the ground surrounded by the extension. From this injection well, for example, an injection liquid containing an activator or the like can be injected into the contaminated ground.

As described above, in the present invention, as compared with the case where the impermeable wall is formed below the ground improvement body separately from the ground improvement body by surrounding the ground below the ground improvement body by the extension portion of the ground improvement body. , Construction cost can be reduced.

As described above, according to the ground improvement structure according to the present invention, the construction cost can be reduced.

FIG. 1 is a sectional view taken along line 1-1 of FIG. 2 showing the ground to which the ground improvement structure according to the first embodiment is applied. It is a plan sectional view which shows the grid-like ground improvement body shown in FIG. It is a vertical cross-sectional view which shows the partition wall part provided with the water passage part shown in FIG. (A) is a plan sectional view corresponding to FIG. 2 showing the first modification of the ground improvement structure according to the first embodiment, and (B) is the second modification of the ground improvement structure according to the first embodiment. It is a plan sectional view corresponding to FIG. 2 which shows an example. (A) is a plan sectional view corresponding to FIG. 2 showing a third modification of the ground improvement structure according to the first embodiment, and (B) is a fourth modification of the ground improvement structure according to the first embodiment. It is a plan sectional view corresponding to FIG. 2 which shows an example. (A) is a plan sectional view corresponding to FIG. 2 showing a grid-like ground improvement body of the ground improvement structure according to the second embodiment, and (B) is a modification of the ground improvement structure according to the second embodiment. It is a plan sectional view corresponding to FIG. 2 which shows. It is a cross-sectional view taken along line 7-7 of FIG. 8 which shows the ground to which the ground improvement structure which concerns on 3rd Embodiment is applied. It is a plan sectional view which shows the grid-like ground improvement body shown in FIG. 7. 9-9 is a sectional view taken along line 9-9 of FIG. 10 showing a ground to which a modified example of the ground improvement structure according to the third embodiment is applied. It is a plan sectional view which shows the grid-like ground improvement body shown in FIG.

(First Embodiment)
First, the first embodiment will be described.

(ground)
FIG. 1 shows a ground 10 to which the ground improvement structure 20 and the underground soil purification system 40 according to the first embodiment are applied, and a structure 12 constructed on the ground 10. The ground 10 has, for example, a non-liquefied layer 10A and a liquefied layer 10B deposited on the non-liquefied layer 10A. The arrow F shown in each figure indicates the flow of groundwater.

The liquefaction layer 10B is composed of sandy soil, and is considered to be a layer having a high possibility of liquefaction when an earthquake of a predetermined scale or more occurs. Further, the liquefied layer 10B is an aquifer having a higher water permeability than the non-liquefied layer 10A, so that groundwater can easily flow. On the other hand, the non-liquefaction layer 10A is a water-impermeable layer having a lower water permeability than the liquefaction layer 10B, and is a layer having a low possibility of liquefaction.

The liquefied layer 10B has a contaminated ground 10P containing a pollutant such as VOC (volatile organic compound). Contaminants include, for example, toluene and xylene contained in organic compounds (paints, printing inks, adhesives, cleaning agents, gasoline, thinner, etc., tetrachloroethylene, trichloroethylene, cis-1,2-dichloroethylene, chloroethylene (vinyl chloride). Volatile organic compounds such as monomer), heavy metal compounds, inorganic compounds, oils and the like can be mentioned.

The ground improvement structure 20 and the underground soil purification system 40 according to the present embodiment can be applied not only to the above ground 10 but also to various grounds in which the non-liquefied layer 10A does not exist, for example.

(Ground improvement structure)
The ground improvement structure 20 includes a grid-like ground improvement body 22, an injection well 14, and a pumping well 16. The lattice-shaped ground improvement body 22 suppresses the liquefaction of the liquefaction layer 10B at the time of an earthquake and also suppresses the diffusion of groundwater containing pollutants. The grid-like ground improvement body 22 is formed in the liquefaction layer 10B by, for example, a cement-based solidifying material.

In the present embodiment, the lower end of the grid-like ground improvement body 22 reaches the non-liquefaction layer 10A, but the lower end of the grid-like ground improvement body 22 does not reach the non-liquefaction layer 10A. Is also good. Further, the grid-like ground improvement body 22 is an example of the ground improvement body.

As shown in FIG. 2, the grid-like ground improvement body 22 is formed in a grid pattern in a plan view. Liquefaction of the liquefaction layer 10B is suppressed by imparting shear rigidity to the liquefaction layer 10B by the grid-like ground improvement body 22.

Specifically, the grid-like ground improvement body 22 has an outer peripheral wall portion 24 and a plurality of partition wall portions 26. The outer peripheral wall portion 24 is formed in a rectangular frame shape in a plan view and surrounds the ground 10. The arrow X direction and the arrow Y direction shown in FIG. 2 indicate two horizontal directions orthogonal to each other.

The partition wall portion 26 includes a plurality of partition wall portions 26A arranged along the arrow Y direction and a plurality of partition wall portions 26B arranged along the arrow X direction. The plurality of partition wall portions 26A are arranged at intervals in the arrow X direction. Further, the plurality of partition wall portions 26B are arranged at intervals in the arrow Y direction. The plurality of partition wall portions 26A and the partition wall portions 26B are connected in a grid pattern in a plan view. By these partition wall portions 26A and 26B, the inner region (liquefaction layer 10B) of the outer peripheral wall portion 24 is partitioned into a plurality of regions (hereinafter, referred to as “partition regions”) R. In the following, the section wall portions 26A and 26B will be collectively referred to as the partition wall portion 26.

Here, in the present embodiment, the contaminated ground 10P straddles one of the adjacent section areas R1 and the other section areas R2 among the plurality of section areas R. One compartment area R1 is provided with an injection well 14. On the other hand, a pumping well 16 is provided in the other compartment area R2.

A plurality of water passage portions W for passing groundwater are provided in the partition wall portion 26S between one partition area R1 and the other partition area R2. The section wall portion 26S is an example of a section wall portion located between one section area R1 and another section area R2.

As shown in FIG. 3, the water passage portion W is an unimproved ground portion partially provided on the partition wall portion 26S. The ground has not been improved in this water passage part W. That is, in the water passage portion W, a solidifying material such as a cement-based solidifying material is not injected into the ground 10. As a result, groundwater can flow in the water passage portion W. The water passage portion W is constructed by, for example, the following method.

That is, the partition wall portion 26S of the present embodiment has a plurality of columnar improved bodies 28A and 28B that are continuous in a wall shape. The columnar improved body 28A does not include the water passage portion W. The columnar improved body 28A is constructed by a mechanical stirring method. Specifically, the columnar improved body 28A excavates the ground 10 while injecting a solidifying material such as a cement-based solidifying material from the tip of an excavation auger (not shown), and agitates and mixes the excavated soil and the solidifying material. It has been created.

On the other hand, the columnar improved body 28B includes the water passage portion W. The columnar improved body 28B is constructed by a high-pressure injection stirring method. Specifically, the solidifying material is injected at high pressure from the tip portion 32T of the rotary rod 32 of the high-pressure injection device 30 driven into the ground 10, and the rotary rod 32 is pulled up while rotating. As a result, the solidifying material is injected into the ground 10 near the tip portion 32T of the rotary rod 32, and the columnar improved body 28B is formed in order from the lower end thereof.

Here, when the tip portion 32T of the rotary rod 32 passes through the water passage portion W, the high-pressure injection of the solidifying material from the tip portion 32T is temporarily stopped. As a result, in the water passage portion W, the solidifying material is not injected into the ground 10, and the water permeability of the ground 10 is maintained.

By creating the columnar improved body 28B while temporarily stopping the high-pressure injection of the solidifying material in this way, a plurality of water passage portions W are provided in the partition wall portion 26S. Further, in the high-pressure injection stirring method, as compared with the mechanical stirring method, it is easier to manage the switching between the injection and the stop of the solidifying material, so that the workability of the water passage portion W is improved. It is also possible to create the water passage portion W while temporarily stopping the injection of the solidifying material in the mechanical stirring method.

The number, arrangement, shape, and size of the water passage portions W provided on the partition wall portion 26S can be appropriately changed. Further, when the rigidity of the partition wall portion 26S is reduced by the water passage portion W, the thickness of the partition wall portion 26S may be increased or the distance between the partition wall portion 26S and the other partition wall portion 26 may be narrowed. May be.

(Underground soil purification system)
As shown in FIG. 1, a bio method (biostimulation) is adopted in the underground soil purification system 40. In the bio method, for example, an injection liquid to which an activator (nutrient) such as a sustained-release hydrogen agent or a yeast extract is added is injected from the injection well 14 into the contaminated ground 10P to decompose the contaminated material in the contaminated ground 10P. It is a method of promoting the purification of pollutants by degrading microorganisms by proliferating and activating microorganisms (hereinafter referred to as "degrading microorganisms"). Further, in the present embodiment, the heated injection liquid is injected from the injection well 14 into the contaminated ground 10P to promote the growth and activation of degrading microorganisms.

The underground soil purification system 40 includes a water treatment device 42 and an injection tank 44. In the underground soil purification system 40, the groundwater that has passed through the contaminated ground 10P is pumped from the pumping well 16 and treated by the water treatment device 42. The water-treated groundwater is re-injected from the injection well 14 into the contaminated ground 10P after the above-mentioned activator is added in the injection tank 44.

As described above, in the underground soil purification system 40 according to the present embodiment, the contaminated ground 10P is purified while circulating the groundwater between the contaminated ground 10P and the water treatment device 42. At this time, the underground soil purification system 40 uses (also serves as) the grid-like ground improvement body 22 as an impermeable wall for suppressing the diffusion of groundwater containing pollutants.

Specifically, in the injection tank 44, the groundwater supplied from the water treatment device 42 is stored as an injection liquid. In the injection tank 44, the above-mentioned activator and the like are appropriately added to the injection liquid. That is, the injection tank 44 is an injection liquid adjusting tank that adjusts the injection liquid.

Further, the injection tank 44 is provided with a warmer such as a heater (not shown), for example. By this warmer, the groundwater stored in the injection tank 44 is heated to a predetermined temperature at which decomposing microorganisms can easily grow and activate.

The injection tank 44 is connected to the injection well 14 via the injection pipe 18C. The injection tube 18C is provided with an injection pump (not shown). By operating this injection pump, the injection liquid stored in the injection tank 44 is supplied to the injection well 14 via the injection pipe 18C. The injection liquid supplied to the injection well 14 is injected into one section region R1 in the grid-like ground improvement body 22.

The injection liquid injected into one compartment region R1 is supplied to the other compartment region R2 via the water passage portion W of the compartment wall portion 26S between the one compartment region R1 and the other compartment region R2. To. At this time, the grid-like ground improvement body 22 that partitions one partition area R1 and the other section area R2 functions as an impermeable wall that suppresses the diffusion of groundwater containing pollutants.

A pumping well 16 is connected to the water treatment device 42 via a pumping pipe 18A. The pumping pipe 18A is provided with a pumping pump (not shown). By operating this pumping pump, the groundwater in the other section region R2 in the grid-like ground improvement body 22 is supplied from the pumping well 16 to the water treatment device 42 via the pumping pipe 18A.

The water treatment device 42 includes, for example, a filtration device for filtering the groundwater pumped from the pumping well 16. The water treatment device 42 removes pollutants and the like from the groundwater pumped from the pumping well 16. An injection tank 44 is connected to the water treatment device 42 via a connecting pipe 18B. The connecting pipe 18B is provided with a supply pump (not shown). By operating this supply pump, the groundwater treated by the water treatment device 42 is supplied to the injection tank 44.

Next, the operation of the first embodiment will be described.

As shown in FIG. 2, the grid-like ground improvement body 22 according to the present embodiment has a plurality of partition wall portions 26. The liquefaction layer 10B of the ground 10 is partitioned into the plurality of partition areas R by the plurality of partition wall portions 26. As a result, the liquefaction of the liquefaction layer 10B at the time of an earthquake can be effectively suppressed.

Further, the underground soil purification system 40 according to the present embodiment uses the grid-like ground improvement body 22 as an impermeable wall. Specifically, the contaminated ground 10P straddles one section region R1 and another section area R2 in the grid-like ground improvement body 22. The grid-like ground improvement body 22 that partitions the one compartment area R1 and the other compartment area R2 suppresses the diffusion of groundwater containing pollutants.

By using the grid-like ground improvement body 22 as a liquefaction countermeasure as the impermeable wall of the underground soil purification system 40 in this way, the construction cost of the impermeable wall can be reduced.

Further, by using the grid-like ground improvement body 22 as an impermeable wall, it is possible to purify the contaminated ground 10P while constructing the structure 12 on the grid-like ground improvement body 22. Therefore, in the present embodiment, the construction period of the structure 12 can be shortened as compared with the case where the structure 12 is constructed on the ground 10 after purifying the contaminated ground 10P. As a result, it is possible to accelerate the time when the structure 12 can be moved in.

Here, as a comparative example, when there is no water passage portion W in the partition wall portion 26 between the one partition area R1 and the other section area R2, the one section area R1 and the other section area R2 , It is necessary to provide the injection well 14 and the pumping well 16, respectively. Therefore, the number of injection wells 14 and pumping wells 16 increases.

On the other hand, in the present embodiment, the water passage portion W for passing groundwater is provided in the partition wall portion 26 between one partition area R1 provided with the injection well 14 and the other section area R2. There is. As a result, the injection liquid injected from the injection well 14 into one compartment region R1 is supplied to the other compartment region R2 via the water passage portion W. Therefore, in the present embodiment, the injection well of the other compartment area R2 can be omitted. Therefore, in the present embodiment, the number of injection wells 14 can be reduced.

Further, a pumping well 16 is provided in the other section area R2. From this pumping well 16, groundwater of another section area R2 containing a pollutant is pumped up. At this time, the groundwater of one partition area R1 flows into the other section area R2 via the water passage portion W. Therefore, the groundwater in one section area R1 can also be pumped from the pumping well 16 provided in the other section area R2. Therefore, in the present embodiment, the number of pumping wells 16 can also be reduced.

(Modified example of the first embodiment)
Next, a modified example of the first embodiment will be described.

In the first modification shown in FIG. 4A, the contaminated ground 10P straddles the three section regions R1 to R3 in the grid-like ground improvement body 22 arranged in a straight line (arrow X direction) in a plan view. There is. In this modification, the injection well 14 is provided in one of the three compartment areas R1 to R3 on the one end side. Further, a pumping well 16 is provided in the other compartment area R3 on the other end side of the three compartment areas R.

Here, in the three compartment areas R1 to R3 arranged on a straight line, the water passage portions W are respectively in the two compartment wall portions 26S between one compartment area R1 and the other compartment area R3. It is provided. Thereby, in the present embodiment, the number of the injection well 14 and the pumping well 16 can be reduced as compared with the case where the injection well 14 and the pumping well 16 are provided in each of the three compartment areas R1 to R3.

Next, in the second modification shown in FIG. 4B, it is located at the corner of the four compartment regions R1 to R4 arranged in two directions (arrow X direction and arrow Y direction) in a plan view. An injection well 14 is provided in one compartment area R1, and a pumping well 16 is provided in another compartment region R4 at a corner diagonal to one compartment area R1. Water passage portions W are provided in each of the four partition wall portions 26S located between the one partition area R1 and the other section area R4. Thereby, in the present embodiment, the number of the injection well 14 and the pumping well 16 can be reduced as compared with the case where the injection well 14 and the pumping well 16 are provided in each of the four compartment areas R1 to R4.

In the second modification shown in FIG. 4B, for example, as shown by arrows F1 and F2, there are two routes (shortest paths) from one compartment region R1 to another compartment region R4. do. When there are a plurality of routes in this way, the water passage portion W can be provided in the partition wall portion 26S on any of the routes. In other words, in the second modification shown in FIG. 4B, for example, the water passage portion W can be omitted from the two partition wall portions 26S on the path indicated by the arrow F1 or the arrow F2.

Next, in the third modification shown in FIG. 5 (A), one of the nine compartment areas R1 to R9 arranged in a grid pattern in a plan view, one compartment region at the corner. The injection well 14 is provided in R1. Further, a pumping well 16 is provided in another section area R9 at a corner diagonal to one section area R1. A water passage portion W is provided in each of the twelve compartment wall portions 26S located between the one compartment region R1 and the other compartment region R9. Thereby, in the present embodiment, the number of the injection well 14 and the pumping well 16 can be reduced as compared with the case where the injection well 14 and the pumping well 16 are provided in each of the nine compartment areas R1 to R9.

In the third modified example shown in FIG. 5 (A), the route (shortest path) from one compartment area R1 to the other compartment region R9 is the same as in the second modified example shown in FIG. 4 (B). There are multiple. In this case, as described above, the water passage portion W can be provided in the partition wall portion 26S on any of the routes.

Next, in the fourth modification shown in FIG. 5B, the ground improvement body 50 is formed in the shape of a “day” in a plan view. The ground improvement body 50 has an outer peripheral wall portion 52 and a partition wall portion 54 that partitions the inner region of the outer peripheral wall portion 52 into two partition areas R1 and R2. It is also possible to provide the water passage portion W on the partition wall portion 54. Further, although not shown, it is also possible to provide a water passage portion on the partition wall portion of the ground improvement body formed in the shape of a “rice field” in a plan view.

(Second embodiment)
Next, the second embodiment will be described. In the second embodiment, the members and the like having the same configuration as the first embodiment are designated by the same reference numerals as those of the first embodiment, and the description thereof will be omitted as appropriate.

As shown in FIG. 6A, the ground improvement structure 60 according to the second embodiment includes a grid-like ground improvement body 22, an injection well 14, and a pumping well 16.

The grid-like ground improvement body 22 is formed in a grid pattern in a plan view. The grid-like ground improvement body 22 has an outer peripheral wall portion 24 and a plurality of partition wall portions 26. The inner region (liquefaction layer 10B) of the outer peripheral wall portion 24 is partitioned into a plurality of compartment regions R by the partition wall portion 26.

The plurality of compartment areas R include a small compartment area Rs and a large compartment area Rb. The large section area Rb is formed according to the range of the contaminated ground 10P, and is wider than the small section area Rs. Specifically, as shown by the alternate long and short dash line, a large section is omitted by omitting a part of the section wall portions 26K (partition wall portions 26A and partition wall portions 26B) that are regularly arranged. The region Rb is formed.

As a result, the omitted partition areas R (small section areas Rs) on both sides of the omitted section wall portion 26K are merged (combined) to form one large section area Rb. The contaminated ground 10P is surrounded by this large section area Rb. The size of the large section area Rb is about twice the size of the small section area Rs.

An injection well 14 is provided at one corner (corner) of the large section region Rb. Further, a pumping well 16 is provided at another corner portion (corner portion) of the large section region Rb diagonal to one corner portion.

Next, the operation of the second embodiment will be described.

According to the ground improvement structure 60 according to the present embodiment, the grid-like ground improvement body 22 divides the liquefied layer 10B of the ground 10 into a small division region Rs and a large division region Rb wider than the small division region Rs. do. An injection well 14 and a pumping well 16 are provided in this large section region Rb.

Here, for example, when the area of the division area R by the grid-like ground improvement body 22 is all the same, the contaminated ground 10P tends to straddle the plurality of division areas R. In this case, since it is necessary to provide the injection well 14 and the pumping well 16 in each of the plurality of compartment areas R over which the contaminated ground 10P straddles, the number of the injection well 14 and the pumping well 16 increases.

On the other hand, in the present embodiment, a large section area Rb is formed according to the area of the contaminated ground 10P. This makes it possible to prevent the contaminated ground 10P from straddling a plurality of compartment areas R (small compartment areas Rs). Therefore, in the present embodiment, the number of injection wells 14 and pumping wells 16 can be reduced as compared with the case where the area R of the partition areas R is all the same.

(Modified example of the second embodiment)
Next, a modified example of the second embodiment will be described.

In the modified example shown in FIG. 6B, the ground improvement body 62 has an outer peripheral wall portion 64 and a plurality of partition wall portions 66. The partition wall portion 66 has a plurality of partition wall portions 66A and a partition wall portion 66B. The liquefaction layer 10B of the ground 10 is partitioned by the partition wall portion 66 into a small partition region Rs, a plurality of medium compartment regions Rm, and a large compartment region Rb.

The middle compartment area Rm is wider than the small compartment area Rs. The large compartment area Rb is wider than the medium compartment area Rm. This large section area Rb is formed according to the area of the contaminated ground 10P and surrounds the contaminated ground 10P. As described above, the large section region Rb can be formed according to the size and arrangement of the contaminated ground 10P. Further, the size, arrangement, and number of the small section area Rs and the medium section area Rm can be changed as appropriate.

Further, in the modified example shown in FIG. 6B, it is possible to surround the contaminated ground 10P by the medium section area Rm instead of the large section area Rb. In this case, the medium compartment area Rm is a large compartment area wider than the small compartment area Rs.

In the large compartment region Rb, the liquefaction prevention performance of the liquefaction layer 10B may deteriorate. Therefore, in the large section area Rb, for example, the wall thickness of the section wall portion 66 may be made thicker than that of the small section area Rs, or the improved strength of the section wall portion 66 may be made higher than that of the small section area Rs.

Further, in the second embodiment, the injection well 14 and the pumping well 16 are provided in the large section region Rb. For example, when the small section area Rs also has contaminated ground, the injection well is provided in the small section area Rs. It is also possible to provide a pumping well.

(Third embodiment)
Next, the third embodiment will be described. In the third embodiment, the members and the like having the same configuration as the first embodiment are designated by the same reference numerals as those of the first embodiment, and the description thereof will be omitted as appropriate.

As shown in FIGS. 7 and 8, the ground improvement structure 70 according to the third embodiment includes a grid-like ground improvement body 22. The grid-like ground improvement body 22 partitions the liquefaction layer 10B of the ground 10 into a plurality of section regions R.

Here, as shown in FIG. 7, among the plurality of division areas R, the ground below the division area R1 located at the center of the grid-like ground improvement body 22 is regarded as the contaminated ground 10P. An extension portion 72 is provided in the partition wall portion 26 (rectangular partition wall portion 26 surrounded by the alternate long and short dash line in FIG. 8) that partitions the partition area R1. The extension portion 72 is formed by extending the partition wall portion 26 downward. The contaminated ground 10P is surrounded by the extension portion 72.

More specifically, the extension portion 72 is formed by improving the ground 10 below the partition wall portion 26. The extension portion 72 is located below the other partition wall portion 26 and the outer peripheral wall portion 24. In this embodiment, the extension portion 72 is formed in the non-liquefaction layer 10A. The extension portion 72 is formed in a frame shape in a plan view and surrounds the contaminated ground 10P.

As shown in FIG. 8, an injection well 14 is provided at one corner (corner) of the compartment area R1. Further, a pumping well 16 is provided at the other corner portion (corner portion) of the section region R1 diagonal to one corner portion. As shown in FIG. 7, the injection well 14 and the pumping well 16 penetrate the partition area R1 (liquefaction layer 10B) and reach the contaminated ground 10P (non-liquefaction layer 10A) surrounded by the extension portion 72. There is. Further, an underground soil purification system 40 is connected to the injection well 14 and the pumping well 16.

The injection port 14A of the injection well 14 is provided only at the portion (lower end side) of the injection well 14 that reaches the extension portion 72. Similarly, the pumping port 16A of the pumping well 16 is provided only at the portion (lower end side) of the pumping well 16 that reaches the extension portion 72. As a result, the flow of groundwater in the compartment area R1 (liquefaction layer 10B) is suppressed.

Next, the operation of the third embodiment will be described.

According to the ground improvement structure 70 according to the present embodiment, the grid-like ground improvement body 22 partitions the liquefaction layer 10B of the ground 10 into a plurality of division regions R. Further, the grid-like ground improvement body 22 is provided with an extension portion 72. The extension portion 72 is formed by extending the partition wall portion 26 that partitions the central partition area R1 of the grid-like ground improvement body 22 downward. By surrounding the contaminated ground 10P below the grid-like ground improvement body 22 by the extension portion 72, the diffusion of groundwater containing pollutants is suppressed.

Further, an injection well 14 is provided in the contaminated ground 10P surrounded by the extension portion 72. The injection well 14 penetrates the central section region R1 of the grid-like ground improvement body 22 and reaches the contaminated ground 10P surrounded by the extension portion 72. From this injection well 14, for example, an injection liquid containing an activator or the like can be injected into the contaminated ground 10P.

As described above, in the present embodiment, the extension portion 72 of the grid-like ground improvement body 22 surrounds the contaminated ground 10P below the grid-like ground improvement body 22, so that the grid-like ground is separated from the grid-like ground improvement body 22. The construction cost can be reduced as compared with the case where the impermeable wall is formed below the improved body 22.

Further, the injection port 14A of the injection well 14 is formed only on the lower end side of the injection well 14 that reaches the extension portion 72. As a result, the injection liquid containing the activator and the like can be efficiently injected into the contaminated ground 10P. The number and arrangement of the injection ports 14A can be appropriately changed. For example, the injection port 14A may be provided above the injection well 14.

Further, a pumping well 16 is provided in the contaminated ground 10P surrounded by the extension portion 72. The pumping well 16 penetrates the central section region R1 of the grid-like ground improvement body 22 and reaches the contaminated ground 10P surrounded by the extension portion 72. From this pumping well 16, groundwater in the contaminated ground 10P surrounded by the extension portion 72 can be pumped up.

Further, the pumping port 16A of the pumping well 16 is formed only on the lower end side of the pumping well 16 reaching the extension portion 72. As a result, the groundwater in the contaminated ground 10P can be efficiently pumped to the ground. The number and arrangement of the pumping ports 16A can be changed as appropriate. For example, a pumping port 16A may be provided above the pumping well 16.

(Modified example of the third embodiment)
Next, a modified example of the third embodiment will be described.

In the modified examples shown in FIGS. 9 and 10, the contaminated ground 10P is located below the grid-like ground improvement body 22. As shown in FIG. 10, the contaminated ground 10P straddles three compartment areas R1 to R3 arranged in a straight line (direction of arrow X) in a plan view.

Here, when the three compartment areas R1 to R3 are merged, the outer peripheral wall portion 24 and the compartment wall portion 26 located on the outer periphery of the merged three compartment areas R1 to R3 (the area surrounded by the alternate long and short dash line). Is provided with an extension 74, as shown in FIG. The extension portion 74 is formed by extending the outer peripheral wall portion 24 and the partition wall portion 26 downward, respectively. The contaminated ground 10P is surrounded by the extension portion 74.

Further, an injection well 14 and a pumping well 16 are provided in the contaminated ground 10P surrounded by the extension portion 74. The injection well 14 is provided in the partition area R1 on one end side of the three section areas R1 to R3. On the other hand, the pumping well 16 is provided in the partition area R3 on the other end side of the three section areas R1 to R3. These injection wells 14 and pumping wells 16 penetrate the compartment area R1 or the compartment area R3 and reach the contaminated ground 10P surrounded by the extension portion 74.

In this way, the extension portion 74 can be provided on the grid-like ground improvement body 22 according to the size of the contaminated ground 10P.

(Other variants)
Next, other modification examples will be described. In the following, various modifications will be described by taking the first embodiment as an example, but these modifications can be appropriately applied to the second and third embodiments.

In the first embodiment, biostimulation is used as the bio method, but the bio method is not limited to this. For example, bioaugmentation may be used in which an externally cultivated microorganism is injected into the contaminated ground 10P together with an activator or the like. Further, in the first embodiment, the injection liquid to be injected from the injection well 14 into the contaminated ground 10P is heated, but the injection liquid does not have to be heated.

Further, the arrangement and number of the injection well 14 and the pumping well 16 can be changed as appropriate. Further, the pumping well 16 may be provided as needed and may be omitted as appropriate.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and one embodiment and various modifications may be used in combination as appropriate. Of course, it can be carried out in various embodiments as long as it does not deviate.

10 Ground 14 Injection well 16 Pumping well 20 Ground improvement structure 22 Lattice ground improvement body (ground improvement body)
26 Section wall part 26K Section wall part 26S Section wall part 50 Ground improvement body 54 Section wall part 60 Ground improvement structure 62 Ground improvement body 66 Section wall part 70 Ground improvement structure 72 Extension part 74 Extension part R Section area R1 Section area (1) Section area)
R2 compartment area (other compartment area)
R4 compartment area (other compartment area)
R9 compartment area (other compartment area)
Rs small section area Rb large section area W water passage

Claims (3)

A ground improvement body having a section wall portion that divides the liquefied layer of the ground into a plurality of section areas, and a ground improvement body.
An injection well provided in the compartment and injecting an activator that activates degrading microorganisms that decompose contaminants in the liquefaction layer into the compartment.
Groundwater provided in the section wall portion located in the liquefaction layer, which is the section wall portion between the section area where the injection well is provided and reaches the other section area. The water passage part through which it passes, and
A pumping well provided in the other section area to pump groundwater in the section area ,
Ground improvement structure equipped with. The water passage portion is provided above the lower end portion of the partition wall portion.
The ground improvement structure according to claim 1. A plurality of the water passage portions are provided on the partition wall portion at intervals in the vertical direction.
The ground improvement structure according to claim 1 or 2.

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