JP2008106578A - Ground improvement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ground improvement method for uniformly increasing strength of the ground around a press-in pipe, simultaneously when preparing a uniform improvement body having the large effective cross-sectional area in target size and shape. <P>SOLUTION: This method for statically pressing in an improvement material, comprises an inserting process of inserting the press-in pipe 2 up to a target press-in starting position into the ground, a press-in process of pressing the improvement material 10 in the outward direction of a plurality of shaft diameters in the ground from the press-in pipe 2 by supplying the improvement material to a tip part on the ground side of the press-in pipe 2, and a pulling-up process of pulling up the press-in pipe 2, and is characterized by being compacted by push-expanding the ground around the pres-in pipe 2 by expanding the improvement material 10 flowing out of the press-in pipe 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ground improvement method by statically pressing an improvement material.

  As a ground improvement method by creating a consolidated body, there is a press-fit compaction method. This is performed by compressing the surrounding ground by joining together a plurality of blocks formed by press-fitting and filling the consolidated material with each other in the ground to be improved. This consolidated material has low slump, non-flowing and self-curing properties, and is axially downward from the tip of the press-fitting pipe of the press-fitting device, top-down or bottom-up, depending on the mode, and press-fitted into the ground. Then, the substantially bulbous blocks are joined together in a stacked manner (see Patent Document 1). This process is repeated after press-fitting until a predetermined ground level, pressure, or press-fit amount is reached, and the process proceeds to the next stage when the predetermined ground level, pressure, or press-fit amount is achieved.

  In addition, there is a column jet grouting method as a ground improvement method by creating another solidified body. For example, while rotating the injection rod, the first to third injection nozzles provided on the side surfaces of the injection rod are injected with fresh water or air at a high pressure to cut the surrounding ground to form a desired cavity. Later, the injection rod is rotated and raised, and the curing agent is horizontally injected from the first to third injection nozzles at a high pressure to fill the cavity with the curing agent (see Patent Document 2). That is, an improved body is formed by replacing earth and sand with a curing agent.

  On the other hand, there is a chemical solution injection method as another ground improvement method. This is performed by penetrating the injection tube into the ground and pressurizing and injecting the chemical solution from the bottom and side surfaces of the injection tube to infiltrate and inject the chemical solution into the ground to form a split vein (Patent Document 3). reference). That is, an improved body is formed by substituting the split water caused by pore water and a chemical solution. This chemical injection can be applied mainly to ground reinforcement and water stoppage.

Patent 2743232 (Claim 1, paragraphs 0034 to 0036, FIG. 1) JP-A-11-117287 (paragraphs 0018 to 0019, FIGS. 4 to 6) JP 2000-64266 (Claim 1, paragraph 0001, paragraph 0008, FIG. 3)

  According to the invention described in Patent Document 1, as shown in FIG. 7, after the consolidated material is discharged only in the axially downward direction from the discharge port at the tip end portion of the press-fitted pipe with respect to the ground, the upward and horizontal directions are mainly used. It is irregularly spread and press-fitted. This is because the discharge direction of the consolidated material coincides with the direction in which the stress in the soil is large, so that the consolidated material is difficult to be press-fitted and filled in the discharge direction, and is biased in a weak direction in the ground and escapes. Therefore, since the action of the consolidated material spreading in the horizontal direction is weak and unstable, the blocks are small and uneven in the horizontal direction. Along with this, the strength of the ground around the press-fit pipe is also small and non-uniform. That is, it is difficult to create a block having a target size and shape.

  Also, in this case, since the ground is pushed upward in the vertical direction, the ground is likely to rise, and the press-fit pipe is pushed to cause deformation such as buckling or even impossible to pull out. . In this way, when the press-fit pipe is deformed, the discharge direction of the consolidated material changes, so that the direction in which the block is formed becomes more irregular, and the effective cross section continuous in the vertical direction becomes smaller. In FIG. 7, the effective cross section is indicated by a broken line.

  Further, since press-fitting is performed in a stacked manner at a predetermined depth, constriction occurs between the stacked layers so that a substantially bulbous block is easily formed, and the effective cross section continuous in the axial direction is further reduced.

  In the invention described in Patent Document 1, in order to increase the effective cross section continuous in the axial direction, when the consolidated material is injected with high pressure in the horizontal direction as shown in Patent Document 2, the ground is cut, so the surrounding ground Cannot be compressed. In addition, since the equipment for high-pressure injection is large, the risk of ground collapse is particularly high in places where the improvement range is shallow or in soft ground. Therefore, it is not effective to apply the invention described in Patent Document 2 to the invention of Patent Document 1.

  Moreover, since patent document 2 uses the high-pressure injection nozzle, it is necessary to make a hardening | curing agent into a suspension form. Here, when a suspension-type curing agent is used in the invention described in Patent Document 1, the curing agent is separated in the ground, causing runaway or stray, and compressing the surrounding ground is improving the ground. Can not. Conversely, when a curing agent having a low slump value that can compress the surrounding ground is used for the high-pressure injection nozzle of Patent Document 2, the flow path connected to the nozzle in the injection rod is blocked by the curing agent and injected. Can not.

  On the other hand, in the inventions of Patent Document 1 and Patent Document 2, a block or an improved body is formed by a solidifying material or a curing agent. However, the chemical solution injection method described in Patent Document 3 injects a chemical solution into the gap portion of the ground to form a split vein to improve the natural strength and water stoppage. That is, Patent Literature 1 and Patent Literature 2 are different from Patent Literature 3 in terms of application and effect. Here, in the invention described in Patent Document 1, even if the consolidated material is injected in the horizontal direction as shown in Patent Document 3, a stacked block is not formed, and the surrounding ground cannot be compressed. Therefore, it is not effective to apply the invention described in Patent Document 3 to the invention of Patent Document 1.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to spread the improved material press-fitted into the ground outward in the axial radial direction so that the effective cross section is continuous in the axial direction. It is an object of the present invention to provide a ground improvement method in which an improved body having a uniform size is formed with a target size and shape, and at the same time, the strength of the ground around the press-fit pipe is uniformly increased.

  The ground improvement method of the present invention is a method of statically press-fitting the improved material, an insertion step of inserting the press-fitted pipe into the ground to the target press-fitting start position, and the improved material to the tip of the press-fitted pipe on the ground side. Supplying and introducing the improved material into the ground from the press-fit pipe into the ground by a plurality of shaft diameter outwards and the pulling-up process for lifting the press-fit pipe, the improved material is discharged from the press-fit pipe, and the ground around the press-fit pipe Is characterized in that it is spread and compacted (Claim 1). Here, the plurality of shaft diameters outward means an absolute press-fitting direction with respect to the ground, and means that the improving material is not press-fitted with respect to the ground from only one predetermined direction.

  The improved material is not pressed downward in the axial direction, but is statically pressed into the ground with multiple shaft diameters outward, so the press-fit direction is weak due to the density and hardness of the ground. It spreads widely and uniformly outward in the axial radial direction on the same plane perpendicular to the axis without accidentally spreading in a direction. Along with this, the strength of the ground around the press-fit pipe is uniformly increased on the same plane perpendicular to the axis.

  Further, since the press-fitting directions are outward from the plurality of shaft diameters, the press-fitting pipes are not pushed biased upward in the axial direction from the ground or the improved body via the press-fitting material. Accordingly, since the press-fit pipe is not deformed or shaken, the improved body is formed straight in the axial direction, and an improved body having a large effective cross-section continuous in the axial direction and a uniform shape can be formed. Can be easily pulled out.

  Further, since the improved material is not pressed in only in the vertical direction, there is little risk that the ground will be pushed only in the vertical direction to rise. Furthermore, since the improved material is statically press-fitted, there is little risk of the ground being disturbed and collapsing, so there is little impact on the surrounding ground and structures. Therefore, the present construction method can be applied even in a shallow area of the ground.

  If the press-fitting step and the pull-up step are performed continuously at the same time (Claim 2), the improved material is continuously press-fitted in the axial direction, and the improved body becomes uniform in the axial direction. Is further suppressed, and the ground strength is uniform in the axial direction. Therefore, since the improved body is formed in a substantially cylindrical shape and can be guaranteed as a pile body, an effect as a supporting force can be expected. On the other hand, it can be used as a composite ground considering strength. Moreover, since the improved body becomes a continuous large lump, it has excellent durability and is strong against shaking and vibration such as an earthquake. Here, the uniformity can be further improved by maintaining the pulling speed at a constant speed.

  If the press-fitting step and the pulling-up step are alternately repeated a predetermined number of times (Claim 3), the press-fitting amount of the improved material can be controlled and press-fitted while checking the target press-fitting amount by dividing each press-fitting step. .

  While the improvement material is being press-fitted into the ground, there is a case where a rotation process is performed in which the press-fitting pipe is rotated in the circumferential direction of the shaft. The term “rotation” as used herein refers to a method in which either one of clockwise or counterclockwise rotation with respect to the axial direction is continuously rotated and a method of alternately rotating clockwise and counterclockwise in succession.

  In this case, since the improved material is press-fitted outward in the axial radial direction continuously from the entire circumference of the shaft, the improved material spreads more uniformly on the same plane perpendicular to the shaft, and further, an improved body close to a cylindrical shape is formed. be able to. Along with this, the strength of the ground around the press-fit pipe is uniformly increased on the same plane perpendicular to the axis. Furthermore, since the reaction force that the press-fit pipe receives from the surrounding ground becomes uniform, the influence on the press-fit pipe such as deformation is reduced.

Further, in principle, the improvement material is press-fitted into the ground from a discharge port provided on the side surface of the tip side of the press-fit pipe on the ground side and having a total area equal to or larger than the cross-sectional area of the press-fit pipe. In this case, since the improving material does not spray from the discharge port, the ground is expanded without forming a hollow portion in the ground, and is statically pressed into the ground while maintaining the pressure. Moreover, the inside of the press-fit pipe is hardly blocked by the improving material. Here, in order for the improvement material to be press-fitted outward in a plurality of shaft diameters, a plurality of discharge ports are provided in principle.

  Further, in order to allow the improved material flowing out from the press-fit pipe to be press-fitted from the press-fit pipe so as to push the surrounding ground, the slump value of the improver is specifically set to 5 cm or less (claim 6). . According to this setting, the improvement material penetrates into the ground even when it is difficult to spread the ground with the improvement material because it contains a lot of water and gaps such as soft ground and gravel layer. Or solidified in a vein shape, and the improved material can be stably press-fitted outward in the axial diameter of the press-fit pipe.

  A ground improvement method for compressing the ground between the improved bodies formed by hardening the improvement material press-fitted into the ground by performing the ground improvement method according to any one of claims 1 to 6 at a plurality of locations. (Claim 7). According to this method, the portion sandwiched between the improved materials and compacted is uniform along the axial direction of the press-fit pipe, the same strength if the distance between the improved materials is equal and the ground conditions are the same. Have In addition, when the diameter of the improved body is increased as described above, when a plurality of improved bodies are formed, the distance between adjacent improved bodies becomes longer, so the number of improved bodies in the improved range is reduced, the process is shortened, and the construction cost is reduced. Can be reduced.

  As described above, the present invention is composed of the press-fitting process for press-fitting the improvement material into the ground from the press-fitting pipe into the ground and the lifting process for lifting the press-fitting pipe. Providing a ground improvement method that uniformly increases the strength of the ground around the press-fitted pipe while simultaneously creating a uniform improved body with a large effective cross-sectional area with the target size and shape by pushing outward in the axial radial direction. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 4 show a ground improvement method by press-fitting of an improvement material. In order to carry out this construction method, there are a press-fitting pipe insertion device 1a and a press-fitting device 1b.

  As shown in FIG. 1, the press-fitting pipe insertion device 1 a includes a boring machine 3 that rotates the press-fitting pipe 2, a water tank 14, a water supply hose 12, and a water supply pump 13. As shown in FIG. 3, the press-fitting device 1 b is connected to an improved material production facility 4 and an improved material production facility 4 that create the improved material 10, and a press-fitting pump 5 that supplies the improved material 10 to the press-fitted pipe 2. Press-fitting pipe lift device 6 for improving the pressure, the flow rate pressure monitoring device 7 for measuring the press-fitting status when the improved material 10 is press-fitted, the hose 8 for connecting the flow pressure monitoring device 7 and the press-fitting pump 5, and the flow pressure monitoring device 7 and the press-fitting pipe 2 A hose 9 is provided.

(Embodiment 1)
The construction procedure for performing the ground improvement method when the press-fitting pipe 2 is vertically inserted into the ground and the low-fluidity improving material 10 is pressed into the ground in the horizontal direction will be described. First, as shown in FIG. 1, the boring machine 3 is installed at a target set position by a lifting machine (not shown), and the press-fitting pipe 2 is inserted into the press-fitting pipe insertion hole 11 a provided in the boring machine 3. The end of the water supply hose 12 is connected to the upper end via the connecting pipe 23. The other end of the water supply hose 12 is connected to a water tank 14 via a water supply pump 13.

  The press-fit pipe 2 is formed in a cylindrical shape, but is preferably circular and the same diameter over the entire length. As shown in FIG. 5, the press-fitting pipe 2 is constituted by a drilled part 21 and a single pipe part 22, which are connected and integrated. A bit 24 is provided on the outer surface of one end of the hole-cutting portion 21, a male screw is provided on the other end, and a discharge port 25 is provided on the side surface of the central portion between both ends. The discharge ports 25 are, for example, elliptically long in the axial direction of the press-fit pipe 2 and are provided evenly in the circumferential direction, for example, three in the circumferential direction. The total area of the discharge ports 25 is larger than the cross-sectional area of the press-fit pipe 2.

  One end of the single tube portion 22 is provided with a female screw, and the other end portion is provided with a male screw. The male screw of the hole drilling portion 21 and the female screw of the single tube portion 22 are screwed together to form a hole. The press-fit tube 2 is inserted into the press-fit tube insertion hole 11a so that the portion 21 is positioned below. Here, it is desirable that the outer periphery of the drilled portion 21 where the bit 24 is installed is larger than the outer periphery of the single tube portion 22 so that the press-fit pipe 2 can be inserted into the ground without resistance when drilling. Further, the number of discharge ports 25 is not limited to three, and it is sufficient that the total area of the discharge ports 25 is larger than the cross-sectional area of the press-fit pipe 2.

  The boring machine 3 is operated while water is being sent from the water tank 14 to the drilling part 21 by the water pump 13, and the press-fitting pipe 2 is inserted into the ground while drilling with the bit 24. When the target drilling length is longer than the press-fitting pipe 2 that is first inserted into the press-fitting pipe insertion hole 11a, when the connection part between the single pipe part 22 and the connection pipe 23 descends above the press-fitting pipe insertion hole 11a, The press-fit pipe 2 is extended by adding another single pipe part 22 having the same shape and structure between the pipe part 22 and the connection pipe 23.

  When the ground is drilled by the bit 24, the soil and sand in the drilled ground and the water discharged from the press-fit pipe 2 are mixed, and as muddy water, the outer periphery of the hole to be drilled and the outside of the press-fit pipe 2 are mixed. It is discharged to the ground from between the sides. The drilling and the extension of the press-fit pipe 2 are repeated until the center of the discharge port 25 reaches the target press-fit start position (in FIG. 2, the extension of the single pipe portion 22 is repeated three times).

  As shown in FIG. 2, when the hole is drilled until the center of the discharge port 25 reaches the target press-fitting start position, the water supply pump 13 is stopped and the water supply hose 12 is removed. Thereafter, as shown in FIG. 3, the boring machine 3 and the press-fitting pipe lifting device 6 are replaced by a lifting machine (not shown), and the hose 9 is connected to the end of the connection pipe 23.

  As shown in FIGS. 3 and 4, the press-fit pump lifts the low-fluidity improver 10 produced by the improver production facility 4 while continuously pulling up the press-fit pipe 2 at a constant speed while rotating the press-fit pipe 2 by the press-fit pipe lift device 6. 5 is pressure-fed to the hole-drilling portion 21 and is press-fitted outwardly from the discharge port 25 into the ground. As shown in FIG. 4, the improvement material 10 is press-fitted until the center of the discharge port 25 reaches the target press-fitting end position. The pulling speed is appropriately determined according to the target press-fitting amount, press-fitting flow rate, ground hardness, and the like.

  Next, when the single pipe part 22 screwed to the connection pipe 23, that is, the uppermost single pipe part 22 and the connection part of the single pipe part 22 connected thereto are positioned above the press-fit pipe insertion hole 11b. The press-fitting pump 5 and the press-fitting pipe lifting device 6 are stopped once. In this state, the uppermost single pipe portion 22 is removed, the connection pipe 23 is connected to the single pipe portion 22 inserted through the press-fit pipe insertion hole 11b, and the press-fit pipe lift device 6 and the pressure feed pump 5 are restarted.

  Even after the press-fitting is completed, the press-fitting pipe 2 is pulled up and the single pipe part 22 is repeatedly removed until the tip of the drilled part 21 comes out to the ground. Thus, since the press-fitting of the improved material 10 can be completed by one drilling and pulling up by one press-fitting pipe 2, the number of operations and the number of facilities are small, and the working time and facility cost can be suppressed. .

  In addition, while the improved material 10 is being pressed into the ground, the flow rate pressure monitoring device 7 measures the improved material pumping pressure, the improved material pumping flow rate, and the improved material pumping total amount in real time so that the press-fitting is performed appropriately. to manage. By measuring the improved material pumping pressure, it is possible to indirectly monitor the change of the ground during the press-fitting, and thus it is possible to prevent the surrounding ground from rising. On the other hand, by measuring the improved material pumping flow rate and the improved material pumping total amount, the press-fitting amount of the improving material 10 can be managed while confirming the target press-fitting amount.

  As shown in FIGS. 5 and 6, a substantially conical branch portion 26 whose apex is positioned on the upper side in the axial direction is formed inside the hole-cutting portion 21, and continuously below the bottom surface of the branch portion 26. A columnar blocking portion 27 is formed. The discharge port 25 is provided on the upper side in the axial direction from the bottom surface of the branch portion 26. Therefore, the improving material 10 that is pumped to the hole drilling portion 21 is press-fitted outward in the shaft diameter from the discharge port 25 into the ground along the shape of the branch portion 26.

  In this way, when the press-fit pipe 2 is inserted vertically into the ground and the improved material 10 is pressed in the horizontal direction, the improved material 10 is pushed outward in the shaft diameter in order to press-fit in the direction with the smallest stress in the soil. Since it spreads greatly, an improved body with a large effective cross-sectional area can be molded. Further, along with this, the horizontal stress of the ground can be increased efficiently. Here, the change in the state of the ground after the press-fitting is completed before press-fitting is shown in FIGS.

  The total area of the discharge ports 25 is preferably equal to or greater than the press-fit pipe area, and more preferably about 1.5 to 4 times for the most effective press-fitting. In this case, the pressure for press-fitting the improved material 10 into the ground from the discharge port 25 is about 2 to 8 MPa, which is the same as the pressure in the press-fit pipe 2, so that the improved material 10 is effectively press-fitted statically into the ground. In addition, the ground is spread outward in the axial diameter. Further, it is possible to prevent a decrease in strength of the press-fit pipe 2 due to an increase in the number of discharge ports 25. Here, when the total area of the discharge ports 25 is 6 times or more the area of the press-fit pipe 2, the press-fit pressure becomes small and it is difficult to push the ground. On the other hand, when the total area of the discharge port 25 is made smaller than the area of the press-fitting pipe 2, the improved material 10 is blocked by the discharge port 25 and cannot be press-fitted, or the press-fitting pressure becomes larger than necessary. Eruption occurs, making it easier to run away in a vein or destroy the ground. In addition, when the press-fitting pressure becomes larger than necessary, material separation that causes the press-fitting pipe 2 to be blocked easily occurs.

  Moreover, since the improvement material 10 is press-fitted while pulling up the press-fit pipe 2 continuously, it is press-fitted continuously in the axial direction by the length of one single pipe portion 22 which is the removal interval of the press-fit pipe 2. For this reason, it is possible to form an improved body that is continuous in the axial direction, and it is possible to create an improved body that is advantageous for shaking such as an earthquake. Although there is no particular provision for the single tube portion 22, a standard having a diameter of 5 to 10 cm and a length of about 1 to 3 m is appropriate.

  Moreover, it is desirable that the improving material 10 has low fluidity. Here, the low fluidity refers to the hardness of the improving material 10 that is harder than the target ground and that can push the expanding material 10 around the press-fitted pipe by the press-fitting of the improving material 10. If the slump value is 5 cm or less, even if it is a soft ground or a gravel layer, the density will be increased by expanding the ground without forming a split vein with the improved material 10 or destroying the ground. be able to.

  By creating a plurality of improved bodies at a predetermined interval by the above-described method, the ground compaction due to the formation of each improved body interferes with the ground between the improved bodies, so that the density and strength of the ground between the improved bodies are reduced. Increase. Here, the method of forming the improved body at a plurality of locations may be formed sequentially one by one or at the same time, and may be applied as appropriate depending on the progress of the process and the construction cost. When it is necessary to shorten the process, it is effective to create an improved body at the same time by adding equipment.

(Embodiment 2)
Next, a press-fitting method other than the first embodiment will be described. Therefore, the method other than the press-fitting method is performed in the same manner as in the first embodiment.

  The improved material 10 created by the improved material production facility 4 is pumped to the drilling portion 21 by the press-fitting pump 5 and at the same time, the improved material 10 is pressed into the ground in a plurality of shaft diameters outwardly, and the target press-fitting amount is press-fitted. Then, the press-fit pipe 2 is pulled up by the target length. This operation is repeated until the center of the discharge port 25 reaches the target press-fit end position. The target press-fitting amount is calculated from the target improved body volume and the target length for lifting the press-fitting pipe 2.

  In this way, by dividing the press-fitting stage from the target press-fitting start position to the press-fitting end position, it is possible to press-fitting while confirming the press-fitting range over the entire length in the axial direction, so the effective cross section of the improved body continuous in the axial direction. Can be formed uniformly. In this method, the fixed interval is usually about 30 cm. Therefore, since the press-fitting amount of the improved material 10 press-fitted into the ground is confirmed about every 30 cm, an error from the target press-fitting amount can be reduced. Further, since the axially outward press-fitting is performed, the improved body is not constricted between the target lengths, and the effective cross section is not reduced.

  In the embodiment, the shape of the discharge port 25 is described as an ellipse, but the shape is not limited thereto. Furthermore, if the protrusions 25 have the same shape and are evenly arranged on the same cross section, the reaction force received by the press-fit pipe 2 from the surrounding ground cancels out, so there is no risk of the press-fit pipe 2 being deformed. Therefore, this setting is desirable, but not limited to this.

  Further, the shape, size, number of installed bits, and installed location of the bit 24 are not limited to the above case, and the setting can be appropriately changed according to various conditions such as the target ground.

The insertion process construction situation figure in the ground improvement method by static press-fitting of the improvement material is shown. The insertion process completion situation figure in the ground improvement method by static press-fitting of the improvement material is represented. The press-fit process construction situation figure in the ground improvement method by static press-fit of the improvement material is shown. The press-fit process completion situation figure in the ground improvement method by static press-fit of the improvement material is represented. The longitudinal cross-sectional view in the press-fit pipe lower end part in press-fitting is represented. The AA sectional view in the press-fitting pipe lower end part during press-fitting is shown. The longitudinal cross-sectional view in the press-fitting pipe lower end part in the press-fitting of a prior art is represented. A state diagram of the ground before press-fitting is shown. A state diagram of the ground during press fitting is shown. The state diagram of the ground after completion of press-fitting is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... Press-in pipe insertion apparatus 1b ... Press-in apparatus 2 ......... Press-in pipe 3 ......... Boring machine 4 ......... Improvement material production equipment 5 ......... Press-in pump 6 ...... Press-in pipe lift device 7 ......... Flow rate pressure monitoring device 8, 9 ... hose 10 ... improved material 11a ... press-fit pipe insertion hole (boring machine)
11b ... Press-fit pipe insertion hole (press-fit pipe lifting device)
12 ... Water hose 13 ... Water pump 14 ... Water tank 21 ... Drilled hole 22 ... Single pipe 23 ... Connecting pipe 24 ... Bit 25 ... Discharge port 26 ... Branch 27 ... Blockage Part

Claims (7)

A method of statically press-fitting the improved material,
An insertion step of inserting the press-fit pipe into the ground up to a target press-fit start position; supplying the improvement material to the ground-side tip of the press-fit pipe; and a plurality of shaft diameters of the improvement material from the press-fit pipe into the ground A press-in process for press-fitting outward and a pull-up process for pulling up the press-fit pipe,
A ground improvement method characterized by causing the improvement material to flow out from the press-fit pipe, and expanding and compacting the ground around the press-fit pipe.   2. The ground improvement method according to claim 1, wherein the press-fitting step and the pulling-up step are performed continuously at the same time.   The ground improvement method according to claim 1, wherein the press-fitting step and the lifting step are alternately repeated a predetermined number of times.   The ground improvement method according to any one of claims 1 to 3, further comprising a rotating step of rotating the press-fitting pipe in a circumferential direction of the shaft while the improvement material is press-fitted into the ground.   The improvement material is press-fitted into the ground from a discharge port that is provided on a side surface of a tip portion on the ground side of the press-fit pipe and has a total area equal to or larger than the cross-sectional area of the press-fit pipe. The ground improvement method according to any one of 4   The ground improvement method according to any one of claims 1 to 5, wherein a slump value of the improvement material is 5 cm or less.   By performing the ground improvement method according to any one of claims 1 to 6 at a plurality of locations, the improvement material formed by curing the improvement material press-fitted into the ground by the ground improvement method. A ground improvement method characterized by compressing the ground.

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