WO2007129693A1

WO2007129693A1 - Soil improvement method

Info

Publication number: WO2007129693A1
Application number: PCT/JP2007/059475
Authority: WO
Inventors: Shigeyoshi Takahashi; Tuyoshi Kohata
Original assignee: Asahi Techno Corp.
Priority date: 2006-05-09
Filing date: 2007-05-07
Publication date: 2007-11-15
Also published as: KR20090015025A; KR101138033B1

Abstract

[PROBLEMS] To provide a soil improvement method where the strength of soil is increased by supplying a grout material, such as air/cement grout and a foam material, from the ground into the soil and where polluted soil is purified by supplying fresh air or freshwater from the ground into the soil. [MEANS FOR SOLVING PROBLEMS] The soil improvement method has a step of extending, into the soil, piping (3a) for supplying a grout material, such as the air/cement grout and the foam material, from the ground surface (la) into the soil (lb), a step of pumping up underground water near the soil (lb) by the super well point method in which two or more wells (2) are formed in the soil (lb) at predetermined intervals and bringing the inside of the soil (lb) into an almost vacuum by reducing the pressure in the periphery of the soil, a step of supplying the grout material through the piping(3a), extended from the ground surface (la), into the soil (lb) or, alternatively, a step of repeating supply of air or fresh water through the piping (3a) into the soil (1b), and a step of returning the level of the underground water in the soil (lb) to a natural underground water level.

Description

Specification

Ground improvement method

Technical field

[0001] The present invention is a ground improvement method in soil improvement technology in the construction field, and improves the strength of the ground by supplying a grout material such as air cement milk or foaming material to the inside of the ground part force ground. For the purpose.

Background art

[0002] In general, the safety and economic efficiency of underground work such as civil engineering, architectural foundations, subways, and underground shopping malls are greatly affected by the quality of groundwater countermeasures.

[0003] Conventionally, as a countermeasure against groundwater, there has been known a water stoppage that prevents the inflow of groundwater with a water shielding wall, or a method for lowering the groundwater level by draining the groundwater to the ground. Yes.

[0004] The inventors and applicants of the present application own the following patented inventions.

Patent Document 1: JP 2000-27170 (Patent No. 3243501)

Patent Document 2: Japanese Patent Laid-Open No. 2001-11846 (Patent No. 3280935)

Disclosure of the invention

Problems to be solved by the invention

[0005] The above-mentioned patented invention relates to a ground improvement method by lowering a groundwater level called a so-called superwell point method.

The outline of the superwell point method is as follows. In other words, the strainer section has a double-pipe structure (special separate screen), which is a method of forced drainage while keeping the well in a vacuum.

Structure of special separate screen The separate screen has a double structure consisting of an inner tube and a shoreline strainer. Strain strainer force The groundwater that flows in is separated into air and water between the double pipes and flows into the well through the lower vent.

Continuous vacuum drainage is made possible by applying negative pressure to the inside of the double pipe with a vacuum pump. However, in the above-mentioned conventional invention, it is not a method of supplying grout material such as air cement milk foam material from the ground part to the inside of the ground, and therefore the strength of the ground by the method is improved. It was a great strength.

[0006] This has the following effects. First, the development of a special separate screen can exert a vacuum effect at a large depth, and can be propagated over a wide area for forced drainage. Secondly, unlike the well point method, which was limited to a depth of 6 to 7m, it became possible to forcibly drain in vacuum at the same depth as deep well. _Third , because the well effect is improved by the vacuum effect for deep wells, which have poor well efficiency due to gravity drainage and require a large number, the number of constructions can be reduced. Fourth, if the water level drops to the screen position by the vacuum deep wel method, air can enter the well and the vacuum effect can be reduced. Fifth, this construction method enables forced drainage due to the vacuum effect at a large depth, and the pumping volume is 1.2 to several tens of times higher than the conventional construction method, depending on the geology. This is a deep vacuum drainage and consolidation dehydration method.

Means for solving the problem

[0007] In the present invention, two or more wells are provided at a predetermined interval, and the ground is further improved by carrying out the above superwell point method.

[0008] The first of the present invention is a method of extending a perforated pipe into the ground for supplying a ground surface force air cement milk or a grout material such as a foam material into the ground in the ground improvement method. By using the super-point construction method with two or more wells in the ground at predetermined intervals, groundwater in the vicinity of the ground is pumped up and at the same time the surrounding area in the ground is decompressed. It is a process that makes it almost vacuum, a process that supplies grout material through a perforated pipe extending from the ground surface into the ground, and a process power that returns underground water to the natural groundwater level. .

[0009] The second aspect of the present invention is a method for extending a perforated pipe for supplying fresh air or fresh water into the ground in the ground improvement method in the ground improvement method. By using the Superwell Point Method with two or more wells at predetermined intervals, the groundwater in the vicinity of the ground is pumped up and the surrounding area in the ground is decompressed at the same time. The process of making the inside almost vacuum, the process of repeatedly supplying fresh air or fresh water through a perforated pipe extending from the ground surface into the ground, and the process power to return the underground water to the natural groundwater level It will be.

[0010] A third aspect of the present invention is a ground improvement method according to the first aspect of the present invention, in which a ground surface is formed over the outer periphery of two or more superwell point method wells provided at predetermined intervals. Or concrete material 'Pavement made of asphalt material or airtight material such as new sludge is covered.

[0011] The fourth aspect of the present invention is the ground improvement method according to the first or second invention, wherein the operation of the superwell point method in which two or more wells are provided at predetermined intervals is stopped. Or on the surface of the ground with the suspension of Superwell Point method

——The airtight material covered is removed and air is supplied by natural air supply due to the pressure difference between the inside and outside of the ground and the ground surface.

[0012] The fifth aspect of the present invention is a ground improvement method, wherein, in an alternate layer ground of a viscous soil layer and a sand layer, the pore water pressure of the sand layer below the viscous soil layer is provided with two or more wells at predetermined intervals. In addition, the soil is sucked and depressurized by the Super Wel Point method, so that the stress load is applied to the viscous soil layer and the viscous soil is consolidated and dewatered.

[0013] A sixth aspect of the present invention is a superstructure in which in the ground improvement method, two or more wells are provided at predetermined intervals in a sandy layer below the cohesive soil layer in the cohesive soil of the cohesive soil layer and the sand layer. By vacuuming and depressurizing each other by the L-point method, a vacuum is created and the moisture in the viscous soil layer is evaporated and dehydrated.

[0014] A seventh aspect of the present invention is a superstructure in which in the ground improvement method, two or more wells are provided at predetermined intervals in a sandy layer below the cohesive soil layer in the alternating layered soil of the cohesive soil layer and the sand layer. The lower part of the existing structure installed on the unevenly settled ground surface is drilled with a boring machine by sucking each other by the L point method, and permanent grout material such as foaming material is injected into the drilled hole. In addition to improving the ground, the structure is further lifted up by unevenly sinking by injecting the permanent grout material.

[0015] An eighth aspect of the present invention is that in the ground improvement method, two or more sand layers are placed in the ground of the sand layer. The dynamic consolidation method is performed after lowering the water level in the ground by sucking each other down and reducing the pressure by using the superwell point method with wells provided at predetermined intervals.

[0016] In the ninth aspect of the present invention, in the ground improvement method, in the operation of the superwell point method in which two or more wells are provided at predetermined intervals in the ground of the sand layer, Among them, a water-tightening action is generated in the ground by repeating the relationship of giving a pumping action to one well and suctioning the other well every predetermined time.

The invention's effect

[0017] Since the present invention is configured as described above, the following effects are obtained. In other words, various pumping effects occur when pumping and compacting dewatering at a large depth and large vacuum degree Pv -0.085MP. Utilizing this effect, early consolidation dehydration is possible, and a new ground improvement can be achieved by using its features in combination.

In claims 1 to 5, it is possible to expect a large drop in the water level in part by attracting each other by two or more superwell point methods due to the vacuum effect. In addition, it can be loaded by increasing the stress load by lowering the lifting pressure of the lower part of the viscous soil, which is not the same as the method of pressurizing with the embankment, as a ground improvement of the viscous soil. In claim 2, it has the effect of efficiently purifying contaminated soil.

[0018] According to claim 6, by sucking each other by the two or more superwell point methods, the settlement of the residual subsidence of the viscous soil can be promoted even under the existing structure.

[0019] According to claim 7, the uneven settlement of the generated structure can be corrected by lifting it with a permanent grout material.

[0020] In claim 8, the combination of two or more superwell point methods and dynamic consolidation methods reduces the water level to a deep location, creates an unsaturated ground, and propagates the impact deeply. It was possible to improve the ground in a wide range.

[0021] According to claim 9, it is expected that the sand ground will be watertight due to the swing cleaning effect of the superwell point method. In addition, the super-well cleaning effect can strengthen the ground by removing clay and colloids from loose sand ground. BEST MODE FOR CARRYING OUT THE INVENTION

[0022] In the above-described configuration, the present invention has the following best modes for carrying out the invention.

As a best mode for carrying out the present invention, a case where two wells with high pumping efficiency are excavated as a means for pumping groundwater and the superwell point method is used will be described with reference to the drawings.

[0023] FIG. 1 is a flowchart showing a method for preventing liquid irritation of the ground according to the present embodiment. In this figure, in the soil improvement work for clay soil in the present embodiment, as a step (1): preparation, a impermeable wall is constructed so as to surround the target ground. Process (2): Install multiple wells (superwell points). Process (3): Air cement milk or foaming material supply equipment will be installed on the ground and in the ground. Process (4): Cover the ground surface with an airtight material. Step (5): Ground water is pumped up and air bubbles are degassed by the superwell point method installed in step (2). Step (6): The liquid material is supplied into the ground by the supply equipment for the liquid material such as air cement milk or foamed material in the above step (3). Step (7): Remove all or part of the airtight material covered in the step (4). Step (8): Remove the supply equipment installed in step (3) above. Process (9): Condensate groundwater to the natural water level. Step (10): Remove the two wells installed in step (2). Step (11): Remove the impermeable wall constructed in step (1).

[0024] In the above embodiment, depending on the structure of the target ground, the structure existing on the ground, the state of the ground surface, etc., the steps (1) · (4) and the steps (7) corresponding to these, respectively. · In some cases, (11) can be omitted. In the following, each of the above steps will be described in detail, followed by a description of the underground state change.

Example

[0025] "Process (1): Construction of impermeable wall 5"

As shown in Fig. 2, the alternate ground is composed of sand layer 1 · 1 and cohesive soil layer 1 to be improved.

1 3 2

Construction of the impervious wall 5 with steel sheet piles, etc. to the required depth so as to surround 1 lb of underground. At this time, the height of the top edge of the impermeable wall 5 is constructed so as to protrude from the ground surface la, and water shielding is ensured between members such as steel sheet piles constituting the impermeable wall 5. You The

[0026] “Process (2): Installation of Well 2 (Super Wel Point)”

Next, a plurality (two in the illustrated example) of wells 2 (superwell points) are installed inside the impermeable wall 5 constructed in the above step (1).

[0027] Here, as shown in Fig. 8, well 2 (superwell point) consists of casing 2a, airtight lid 2b, strainer 2c, earth and sand pit 2d, pumping pump 2e, vacuum pump 2g, piping 2h, 2i, Large-capacity and high-head pumping that uses a vacuum pump 2g and a pumping pump 2e to satisfy the functions of collecting water into the well 2 and pumping out of the well 2, with the water tank ¾ as the main component. This is a system proposed by the present applicant (see Patent Document 1). Fig. 8 shows the state of the groundwater surface lc decreasing, and the arrows in the figure indicate the direction of groundwater and air flow. In addition, the negative pressure is propagated in the lower part of well 2 in the figure. In FIG. 2, the ground facilities shown in FIG. 8 are omitted.

[0028] "Process (3): Installation of grout supply equipment 3"

Next, as shown in Fig. 2, the required number of perforated pipes 3a are installed inside the impermeable wall 3d constructed in (1) above using a drilling method such as Boringe. Pipe 3b, 3b and valve 3c are installed at the upper end of pipe 3a, and supply equipment 3 is constructed to function as a grounding grout material introduction path. Note that the valve 3c is closed at the installation stage of the grout material supply equipment 3 such as air cement milk or foam material. Here, the arrows indicate the flow direction of the grout material 9 from the ground surface la to the ground lb. The supply equipment 3 can also be used to supply fresh air or fresh water.

[0029] "Process (4): Covering of airtight material 6"

Subsequently, the airtight material 6 is covered on the ground surface la of the underground lb that is the target of liquid irritation surrounded by the impermeable wall 3d constructed in the step (1), and the end of the airtight material is covered. The supply equipment installed in (3) above for the distribution route of the grout material 9 with ground force by processing so that airtight material can be retained in some openings generated by the head and perforated piping 3a and well 2 Limit to 3 lines. The airtight material 6 may be an airtight sheet, pavement made of asphalt material or concrete material, new sludge that does not emit bad odors, and the like. The grout material 9 includes air cement milk or foam material. [0030] By going through the above steps (1) to (3), the target underground lb is constructed in a certain range in which the sides and the upper part are sealed.

[0031] "Process (5): Groundwater pumping, air bubble deaeration"

Here, the well 2 installed in (2) above is made to function using the superwell point method, so that groundwater existing in the underground lb is collected into the well 2 and collected from the well 2. Pump and drain the drained groundwater to the ground, and lower the groundwater level lc to the required groundwater level. At this time, the state of underground lb is that groundwater that was present in underground lb in the region above groundwater surface lc is pumped out and is also present in underground lb. At the same time, the escape is eliminated, and although the soil particles that make up the underground lb exist, a very high vacuum state (hereinafter referred to as “substantially vacuum”) is formed. Fig. 8 shows the state of decrease in the groundwater level lc, which is the natural groundwater level.

[0032] “Process (6): Supply of grout material 9 such as air cement milk or foaming material”

Next, with the supply equipment 3 installed in the above step (3), the ground force also opens the valve 3c through the piping 3b, 3b and the perforated piping 3a through the grout material 9 such as air cement milk or foaming material. Then supply to the underground lb using the pressure difference. However, the pumping and draining and degassing functions of well 2 must be stopped before moving to this process for supplying grout material 9 to underground lb. Here, since the underground lb is almost in a vacuum state as described above, the underground lb is uniformly filled at a very high diffusion rate. In addition, when supplying fresh air or fresh water instead of the grout material 9, the above-described supply equipment 3 is used.

[0033] "Process (7): Removal of airtight material 6"

Next, the airtight material 6 covered in the step (4) is removed. At this time, the air pressure in the vicinity of the ground surface la of the underground lb approaches the atmospheric pressure by the process of the above step (3), and therefore, there is no difference in the internal and external pressure between the underground lb and the ground, and it can be easily removed. It becomes.

[0034] "Process (8): Removal of grout material supply equipment 3"

Subsequently, the grout material supply facility 3 is removed and the pipe pit is refilled.

[0035] "Process (9): Condensate"

Here, the groundwater pumped in the above step (5) is condensed using the well 2 to the groundwater surface lc at the natural groundwater level. In this process, groundwater surface after pumping groundwater lc For construction properties with a small water head difference from the natural groundwater surface lc, it may be determined according to the construction scale that can proceed to the next step (10) without returning the groundwater taken from well 2.

[0036] “Process (11): Removal of Well 2 (Super Tool Point)”

Next, remove well 2 and refill the well.

[0037] "Process (12): Removal of impermeable wall 5"

Finally, the impermeable wall 5 is removed and the series of processes is completed. Here, if it is necessary to periodically repeat the improvement measures for ground 1, it is left to reduce the number of man-hours for the next construction without removing the perforated piping 3a, well 2 and water barrier 5 of the supply facility 3. You just have to.

Next, an embodiment in an environment different from the steps (1) to (10) will be described. However, the overlapping parts in the above steps are omitted, and only the changed parts are explained.

[0039] As shown in Fig. 3, when the ground surface la is made of concrete or asphalt and the airtight material is paved, the structural foundation 7 and the large oil tank will be added to the underground lb to be further improved. Each case, such as a ground structure 8 such as a lime tank or a lime tank, and a wide range of underground lbs to be improved, will be explained together.

[0040] In such an example, the steps (1) · (4) · (7) · (11) can be omitted, and the reasoning force covering a wide range of underground lbs It is possible to cope with this by reducing the groundwater surface lc over the surrounding area of the target underground lb, which is the purpose of constructing the impermeable wall 5 in 1), and the impermeable wall 5 described in the above step (11). The removal of is also unnecessary. In addition, the air-tight material 6 is applied to the ground surface la. The materials include vinyl sheets, waterproof tents, paving with cement and asphalt, and fresh sludge that does not emit bad odors. It shall be used accordingly. In addition, even when no airtight material 6 has been constructed, the ground structure is such that a highly airtight impermeable layer is formed in the upper layer of the underground lb for the purpose of improving the ground. In this case, this impermeable layer can be an alternative material for the airtight material 6 (not shown).

[0041] However, the existing structural foundation 7 and the ground structure 8 are subject to the sand layer 1 · 1 and viscosity to be improved. Since the soil layer is located at the la position of 1 lb of ground, the above-mentioned process (3

2

), Change the configuration of the supply facility 3 and perform a curved boring of the lower ground of the structure foundation 7 instead of the perforated pipe 3a with the vertical arrangement as shown in Fig. 2, and pass the right and left of the structure foundation 7 to the right and left. By installing the perforated pipe 3a in the form, it becomes possible to supply the permanent grout 9 such as the effective foaming material described in the step (6).

[0042] Other configurations are the same as those in the steps (2), (3), (5), (6), and (8) to (10).

[0043] From here on, the superwell point method will be adopted as the groundwater pumping process of this embodiment, and the explanation will work more effectively. The physical phenomenon is explained microscopically.

[0044] As shown in Fig. 4, in the steady state before ground improvement, soil particles 4a, the main constituent material of underground lb, ground water 4b in the form of free water, physics (electrical) There are adsorbed water 4c adsorbed on the soil particles 4a with a strong bonding force, and air bubbles 4d intervening in the free water 4b.

[0045] Next, as shown in Fig. 5, in the above-mentioned step (5), the ground water 4b is free in the state of the underground lb after the decompression action of the underground lb and the pumping and draining of the ground water 4b. Since the power to be in the state of water 4b is also collected in well 2, only soil particles 4a and adsorbed water 4c exist. Here, the field pressure of the soil particles 4a and the adsorbed water 4c is almost in a vacuum 4e state. This improvement in the vacuum level is the difference between the general well point method and the super well point method, and the underground material lb in the underground lb described in the following paragraphs is used. Since the supply can be performed smoothly and the supply amount of the grout material is also maximized, it is a very effective means under the conditions where the superwell point method can be adopted.

[0046] Next, as shown in FIG. 6, in the step (6), the state in which the grout material is supplied to the underground lb from the ground surface la is temporarily placed in a substantially vacuum _4e state. The area that had been filled is filled with the supplied air.

Next, as shown in FIG. 7, in the step (9), the groundwater 4b is condensed into the underground lb and the groundwater surface lc is restored to the groundwater level in the steady state. Since free water 4b is submerged in the filled area, the amount of air intervening in groundwater 4b increases, so The air content of water 4b increases. As a result, since the degree of unsaturation of groundwater 4b, which is generally unsaturated, further progresses, the water ratio is relatively reduced to suppress the increase in the water pressure of the pore water existing between the soil particles. The ground can be improved by avoiding the reduction of the inter-friction force.

[0048] FIG. 9 and FIG. 10 show a portal-type structure 8 like a crane that supports a horizontal girder 8 "with two right and left support posts ^. After permanent dewatering by vacuum dewatering using two or more Superwell point methods for uneven settlement, the permanent grout material 9 that allows foaming is formed by the curved perforated pipe 3 in Fig. 3 above. By injecting below the base, it can be lifted up to push the base upward.

[0049] Fig. 11 shows a comparison of ground improvement works for loose sand ground. In other words, with the conventional dynamic consolidation method (Fig. 11 (b)), the strength under the groundwater surface due to the dynamic consolidation method is weak and the increase in strength is small. . Therefore, in addition to the above-mentioned dynamic consolidation method, as shown in Fig. 11 (a), using two or more superwell point methods reduces the groundwater level by consolidating and dehydrating early by vacuum dehydration. By doing so, the impact of the dynamic consolidation method can be transmitted to deeper depths, and the viscous soil layer 1 has a vacuum effect.

2 to dehydrate.

[0050] Figure 12 shows that with two or more superwell point methods, a large amount of water (Q ^ l to 4.0t / min) is pumped into the ground, and then a high degree of vacuum (Pv = —0.1 to 0.08) Perform a vacuum suction I with MP). Water and suck in at the same time.

By removing the fine particles of the sand, the particle matrix is adjusted and the strength of the sand is increased (see Fig. 13). The decrease in strength of the sand ground is due to the inclusion of a large amount of colloid and silt component S in the sand. Moreover, the effect of watertightness can be expected by the swing effect.

Brief Description of Drawings

FIG. 1 is a flowchart showing a ground improvement method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a well, a blocking wall, a vertical perforated pipe, and an airtight sheet in the ground improvement method according to the embodiment of the present invention.

[Fig. 3] Wells, ground structures, and curves in the ground improvement method according to the embodiment of the present invention. It is sectional drawing which shows the structure by hole piping and pavement.

圆 4] It is a partial cross-sectional view showing the relationship between soil particles, free water, adsorbed water and air bubbles in a steady state of the ground improvement method according to the embodiment of the present invention.

[5] FIG. 5 is a partial sectional view showing the relationship between the ground water (free water) and the soil particles and the adsorbed water in the air bubble exclusion state in the ground improvement method according to the embodiment of the present invention.

圆 6] It is a partial cross-sectional view showing the relationship between soil particles, adsorbed water and air in the air supply state of the ground improvement method according to the embodiment of the present invention.

[7] FIG. 7 is a partial cross-sectional view showing the relationship among soil particles, free water, adsorbed water, and air bubbles in the condensate state of the ground improvement method according to the embodiment of the present invention.

[8] FIG. 8 is a cross-sectional view showing a well (superwell point method) used in the step of pumping ground water and the pressure reducing step in the ground in the ground improvement method according to the embodiment of the present invention.

FIG. 9 is a schematic diagram showing a lift-up work in which a structure injects a permanent grout material into the foundation of a portal crane according to the present invention.

FIG. 10 is an enlarged cross-sectional view of a part of FIG.

[11] It is an explanatory diagram of the conventional method for sandy ground improvement.

[12] It is an explanatory diagram of the sandy ground improvement method according to the present invention.

圆 13] It is a schematic explanatory view of the present invention adopting a swing cleaning system.

FIG. 14 is a schematic explanatory view of the present invention in which a swing cleaning system is adopted with two or more wells (superwell point method).

FIG. 15 is an analysis diagram showing the particle size of the soil particles after the swing cleaning shown in FIG.

Explanation of symbols

1 …… Ground

la …… Surface

lb …… Underground

lc …… Water table

Sand layer

Cohesive soil layer 1 …… Sand layer below viscous soil layer

Three

2 …… Well (Super Tool Point)

2a …… Casing

2b …… Airtight lid

2c …… Strainer

2d …… Sediment pit

2e …… Pumping pump

2f …… Drain pump

2g …… Vacuum pump

2h, 2i …… Piping

¾ …… Water tank

3 ... Air cement milk or foam grout supply equipment

3a …… Perforated piping

3b …… Piping

3c …… Valve

a …… Soil particles

b …… Free water (groundwater)

c …… Adsorbed water

d …… Air or air bubbles

e …… Vacuum part

5 …… Impermeable wall

...... Airtight material

7 …… Structure foundation

...... Ground structure

r …… Post

〃 …… Horizontal girder

...... Grout material

Claims

The scope of the claims

[1] A process of extending a perforated pipe (3a) for supplying grout material (9) from the ground surface (la) of the ground (1) to the ground (lb), and underground (lb) The groundwater in the vicinity of the ground (lb) is pumped up by the single point construction method with two or more wells (2) at a predetermined interval, and at the same time the surrounding area in the ground is decompressed. The process of evacuating the inside (lb) and the ground surface (1 a) force through the perforated pipe (3a) extending in the ground (lb) A ground improvement method consisting of a supply process and a process of returning underground (lb) groundwater to the natural groundwater level.

[2] Ground in contaminated soil (1) The process of extending a perforated pipe (3a) that supplies fresh air or fresh water from the ground surface (la) to the ground (lb), and the underground The groundwater near the ground (lb) is pumped up and the surrounding area is depressurized at the same time by the Superwell Point Method with two or more wells (2) provided at a predetermined interval in (lb). The process of making the underground (lb) almost in a vacuum state and the process of repeatedly supplying fresh air or fresh water through the perforated pipe (3a) extending from the ground surface (la) to the underground (lb) And ground improvement method consisting of the process of returning underground water (lb) to the natural groundwater level.

[3] Two or more superwell point method wells provided at predetermined intervals (2) Pavement with an airtight sheet, concrete material or asphalt material on the ground surface (la), or new sludge, etc. The ground improvement method according to claim 1, wherein said airtight material (6) is covered.

[4] Stop operation of the superwell point method with two or more wells (2) provided at a predetermined interval, or cover the ground surface (la) when the operation of the superwell point method is stopped. The ground improvement method according to claim 1 or 2, wherein the airtight material (6) is removed and air is supplied by natural air supply due to a difference in pressure between the ground (lb) and the ground surface (la). .

[5] The viscous soil layer (1 sand layer (1))

The pore water pressure of 2 1 3 2 3 is reduced to a viscous soil layer (1) by suctioning and reducing pressure by superwell point method in which two or more wells (2) are provided at predetermined intervals. Apply stress load

2

Cohesive soil layer (1)

A ground improvement method characterized by dehydrating 2

[6] In the cohesive ground of the viscous soil layer (1) and sand layer (1) · (!) Superwell point method with two or more wells (2) at predetermined intervals for layer (1)

Three

Create a vacuum by creating a vacuum by sucking each other together and reducing the pressure (1)

A ground improvement method characterized by vaporizing the water in 2 and dehydrating it.

[7] The sand layer (1) below the cohesive soil layer (1) in the alternating layer ground of the viscous soil layer (1) and sand layer (1) · (1)

2 1 3 2 3 The surface of the ground that has subsided unevenly (la) by sucking and reducing pressure by using the Superwell Point Method with two or more wells (2) provided at a predetermined interval. The lower part of the existing structure (8) installed in is drilled with a boring machine, and permanent grouting material (9) is poured into the drilling hole to improve the ground, and permanent grouting material (9) is further removed. A ground improvement method characterized by lifting up a structure (8) that has been sunk unevenly by pouring.

[8] In the ground of the sand layer, the water level in the ground (lb) is reduced by sucking the sand layer by using the Superwell Point method with two or more wells (2) spaced apart from each other. A ground improvement method characterized by performing a dynamic consolidation method after lowering.

[9] Sand layer (1) · Super with two or more wells (2) in the ground (lb) at a predetermined interval

13

In the operation of the single-point method, one of two pairs of wells is given a pumping action to one well and a suction action is given to the other well alternately. A ground improvement method characterized by generating a water-tightening action on (lb).