JP2879385B2 - Ground improvement or reinforcement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving or strengthening soft ground, and more particularly to a method for press-fitting a self-hardening material such as a cementitious material having a high viscosity into a once loosened ground. The present invention relates to a construction method that aims to increase the diameter of a solidified column.

[0002]

2. Description of the Related Art Various types of ground improvement methods of this type are known. A typical example is a chemical liquid injection method. In this method, as is well known, a chemical solution is injected at a low pressure through an injection pipe inserted into the ground. In this case, the basic idea is that the chemical solution is osmotically injected without disturbing the ground.

On the other hand, in recent years, a high-pressure injection method represented by a so-called jet grout method has been widely used. In this high-pressure injection method, grout is injected into the ground at the same time as the ground is disturbed by the high pressure of grout or water. This high-pressure injection method can be said to be an agitation method for the ground. On the other hand, as a pure stirring method, mainly for the viscous ground, while a stirring shaft having stirring blades is inserted into the ground, the cement-based material is supplied through the stirring shaft or from a separate supply system,
While stirring the ground with stirring blades, the stirring region is replaced with a cement-based material or stirred and mixed with earth and sand.

[0004]

However, in the first chemical solution press-in method, in order to perform osmotic press-in, a low-viscosity material,
Since a water glass-based material is mainly used, the improved strength is low and the durability is poor. Furthermore, the reason that the improvement strength is low is that the ground is not replaced by the improvement material, but the permeation injection or splitting injection is preferable, so that the improvement material occupies a low per unit volume and is non-uniform. doing.

[0005] To further add a problem, in the case of a normal sandy soil layer, infiltration can be performed, but due to a slight difference in injection conditions, splitting injection is performed, and infiltration cannot be performed. There are many things. On the other hand, when injected into a cohesive soil layer, splitting is performed, and the improved material often escapes. For this reason, it is difficult to reliably improve only the target area, and there is a lot of material loss due to the runaway. Further, the desired improved diameter cannot be made uniform, and often becomes a tree-like (tree-like or vein-like) shape.

In the second high-pressure injection method, the ground is extremely disturbed, and slime (muddy water) treatment requires a great deal of labor and cost. Furthermore, if cutting and pouring are to be performed uniformly, and if slime is to be sufficiently discharged, the improvement rate must be reduced, which is a time-consuming method. Moreover, for sandy ground, the strength is 30kg /
cm ² or more, in the case of viscous soil is to target a 10 kg / cm ² or more, the variation in intensity due to the position variation and improvement of strength due to geological nature is extremely large problem. In particular, in the case of a viscous ground, there is a large variation due to embedment of the earth mass due to insufficient cutting.

[0007] The third stirring method is a major drawback in that the equipment becomes large, and in the case of a viscous soil layer, the mixture of the soil particles and the improving material co-rotates with the stirring blade, and the stirring effect is reduced. Not very high, thus lacking in uniformity of improved strength. On the other hand, this stirring method targets the viscous ground as described above. Application to sandy ground is not impossible, but it cannot be applied unless a huge stirring means is used because the resistance of the stirring shaft and stirring blade to the ground is large.

Accordingly, the main objects of the present invention are to improve the strength and the uniformity of the improved body, to make it possible to carry out the construction with simple and small-sized equipment, and to limit or achieve the object of the compaction effect. An object of the present invention is to form a strong improved body only at a specific location, and to increase the diameter of the improved body.

On the other hand, in order to solve this problem, the present inventors have previously disclosed in Japanese Patent Application No. 3-129473 a high pressure water injection nozzle provided on the outer peripheral surface of the tip of an injection pipe inserted into the ground. A method was proposed in which high-pressure water was injected to loosen the target ground, or after loosening, a hardened self-hardening material was pressed into the loose ground to form an improved body. However, the reaching distance from the high-pressure water injection nozzle has a limit in relation to the injection pressure and the like, and therefore, there is a limit in the relaxation diameter or the improved diameter of the ground. On the other hand, it has been considered that the ground is agitated to a large diameter by the above-described stirring method, but in this case, the above-described problem is accompanied.

Therefore, it is desirable to relax the ground with high-pressure water as much as possible. Therefore, another object of the present invention is to basically relax the ground with the energy of high-pressure water and increase the improved diameter.

[0011]

According to a first aspect of the present invention, there is provided, as a first aspect, an overhanging injection portion which is provided at least at a tip end portion of an injection tube so as to protrude to the outside of the tube in a state where the diameter is expanded and ejected. An injection nozzle for injecting high-pressure water outward with respect to the axis is provided, and a spout of a self-hardening material is formed on the tip side from the injection nozzle.The injection pipe is inserted into the ground to be improved, In the process of rotating around the center and pulling up in the axial direction, high-pressure water is injected from the injection nozzle in a state where the overhanging injection portion is projected outward of the pipe, and the ground outside the injection direction of the injection nozzle is relaxed. This problem can be solved by forming a sludge with a slump discharged from the spout through a slump, and then press-fitting the sludge into or out of the sludge mud column.

According to a second aspect, a first injection nozzle for jetting high-pressure water in a radial direction is provided on an outer peripheral surface at a distal end portion of the injection pipe, and at least a large-diameter ejection state is provided at a base side of the first injection nozzle. In the above, an overhanging injection section is provided which protrudes outside the pipe, and the overhanging injection section is directed outward with respect to the improved axis.
The second injection nozzle high-pressure water that reach injecting farther than outer end of ChoIzuru噴morphism portion provided to further form a spout self-hardening material from the distal end side of the first injection nozzle, the injection Inserting the pipe into the ground to be improved, and in the process of rotating around the axis and pulling up in the axial direction, at least the second of
High-pressure water is injected from the injection nozzle to relax the ground outside of the injection direction of the second injection nozzle to form a loose mud column, or to form the loose mud column, and then to perform self-hardening of the stiffening from the spout. The problem can also be solved by discharging the material and press-fitting it to form an improved body.

[0013] In the second aspect, the reaching distance of the high-pressure water from the first injection nozzle is made longer than the protruding length of the overhanging injection portion, and at least the first injection tube is inserted into the ground. The injection pipe can be inserted while loosening the ground by injecting high-pressure water from one injection nozzle. Furthermore, at the time of insertion of the injection pipe into the ground, after digging the casing with a diameter having a radius larger than the distance between the tip of the overhanging injection section and the axis of the injection pipe, or With the injection pipe inserted and the casing removed,
The arrival distance of the high-pressure water from the first injection nozzle is set farther from the outer surface of the casing, and the high-pressure water is injected from the first injection nozzle to loosen the ground, and the arrival distance of the high-pressure water from the second injection nozzle is reduced. It is also possible to make the ground farther than the reach from the first injection nozzle and to inject high-pressure water from the second injection nozzle to loosen the ground. On the other hand, in the first and second aspects, the overhanging injection unit is configured to be able to expand and contract between a folded position along the axis of the injection tube and a position protruding outward by an operation from the ground, and It can be in a contracted state at the time of insertion, and can be made to protrude at the time of injection of high-pressure water from an injection nozzle provided in the overhanging injection section.

[0014]

According to the present invention, the present invention is intended to provide a "fluid injection agent having a large amount of water per unit and having a large amount of water per unit when the ground is once loosened and then press-fitted into the loosened portion, for example, as in the jet grouting method. The strength after the improvement is improved by the replacement action and the consolidation action of the improving material as compared with the case of using. "

According to the present invention, the target ground can be loosened by injecting high-pressure water. The loosening of the ground is mainly performed by breaking the connection between the large soil particles and the surrounding fine soil particles connecting these soil particles.

An improved material (self-hardening material) having a small slump value is press-fitted into the loose ground so as to gradually accumulate from the bottom of the mud column preferably formed of the loose ground. By this press-fitting, the improvement material is injected so as to push the loose ground. Since the improved material according to the present invention has a slump value of about 15 cm or less, the escape of the improved material is prevented, and the loose ground portion is replaced with the improved material exactly. Because the ground part is compacted, a lot of improvement material is pressed into the soft part, while the strength of the ground is less loose in the high strength part. It is possible to form an improved body that is press-fitted and thus has a uniform strength as a whole and a uniform improved diameter.

On the other hand, as equipment to be used, a thin tube, for example,
It is possible to respond sufficiently by using a thing of about 70 mm,
Equipment costs are lower than high-pressure injection method and stirring method. Moreover, since high-pressure water is used to loosen the ground, the slime is not a mixed slime of cement and soil particles, as in the high-pressure injection method, but a mixture of water and soil particles. There is an advantage that is easy. Moreover, if it is a slime consisting only of water and soil particles, it is separated and the water is added as high-pressure water for relaxing the ground. By using it, the overall
Lai-time processing costs can be significantly reduced. In addition, the present invention can be easily applied to a sandy ground, and this point has a remarkable difference from the conventional stirring method. In addition, since the relaxation of the target area of the ground and the press-fitting of the improvement material are performed in a separate step or another stage, the variation in the improvement strength seen in the high-pressure injection method is eliminated.

Further, in the present invention, the most characteristic is given to increase the improvement diameter by injecting high pressure water from ChoIzuru噴morphism unit. As described above, in order to loosen the target ground to a large diameter simply by injecting high-pressure water from the high-pressure water injection nozzle provided on the outer peripheral surface of the tip end of the injection pipe, it is necessary to increase the pressure and increase the discharge amount. Is reduced to reduce the ejection amount. However, increasing the pressure to increase the discharge rate increases the discharge amount of mud, increases the size of the sludge treatment apparatus, and increases the processing cost. When the discharge amount is reduced by reducing the nozzle diameter, the energy of the high-pressure water is rapidly reduced after discharge into the ground, and a sufficient relaxation effect cannot be obtained.

However, according to the present invention, when an overhanging injection portion protruding from the outer surface of the injection tube is provided, high-pressure water is injected from the overhanging injection portion, so that it is not necessary to increase the pressure or reduce the nozzle diameter. Or even if the discharge flow rate is not excessive, compared to the case of discharging from a simple pipe without an overhanging injection part, by the protruding length of the overhanging injection part (exactly from the outer surface of the pipe to the injection nozzle) Distance), and the improved diameter can be increased.

On the other hand, according to a second aspect of the present invention, a first injection nozzle for jetting high-pressure water in a radial direction is provided on the outer peripheral surface at the tip of the injection pipe, and the base side of the first injection nozzle is provided outside the pipe. The use of an injection pipe provided with a projecting overhanging injection section and a second injection nozzle provided at the overhanging injection section has a great advantage. That is, when high-pressure water is injected from the first injection nozzle at the time of insertion of the injection pipe, the ground corresponding to the reaching distance can be loosened, so that the injection pipe is inserted as it is by press-fitting, that is, without requiring casing digging. Because it is possible, it is excellent in workability.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings and specific examples. 1 to 3 show a first specific example, as shown in FIG. 1, a relaxation pipe 2 having a drill bit on the front surface of the tip and a jet nozzle 1 for high-pressure water on the peripheral wall of the tip portion. Insert to a certain depth and then, as shown in FIG.
In the process of pulling up the relaxation tube 2 while rotating it, the high-pressure water W is sprayed from the injection nozzle 1 at a pressure corresponding to the properties of the ground (soil, softness, etc.) and the desired improved diameter, preferably generally 50 kg / cm ^2. Above pressure, especially preferably 80-350 kg
Injects with a pressure of / cm ² to loosen the target ground and form loose mud columns. Show this loose primary relaxation area by the symbol S _1. When the improvement area is below the groundwater level, the reaching distance of high-pressure water becomes extremely small. For example, even if injection is performed at a pressure of 200 kg / cm ² , the improvement diameter is about 40 cm. Alternatively , the relaxation tube 2 may be formed as a double tube, and the injection distance may be increased by distributing the jet air around the high-pressure water.

Next, when this step is completed, FIG.
As described above, the injection pipe 3 is pressed into the loose mud column. The previously end of the injection tube 3, and overhanging injector 30 projecting abluminal at least the enlarged diameter ejection state is provided outward with respect to improvements axis on the projecting jetting portion 30 An injection nozzle 31 for injecting high-pressure water is provided, and a spout 32 of a self-hardening material is formed on the tip side of the injection nozzle 31.

After this injection pipe 3 is inserted into the ground to be improved, as shown in FIG. 3, in the process of rotation around the axis and pulling up in the direction of the axis, the projecting injection section 30 is projected outside the pipe. Then, high-pressure water is injected from the injection nozzle 31 to relax the ground outside the injection direction of the injection nozzle 31. Shown as letter S ₂ designates the relaxation area as a secondary relaxation zone.

While forming this loose ground, a stiff material, preferably a slump value (JIS
A 1101) is press-fitted with a self-hardening material G having a size of 15 cm or less.
Create The formation of the improved body A can be performed up to the ground surface or a certain depth position.

In this case, the lower limit of the slump value of the self-hardening material is 5 cm or more, more preferably 8 cm or more. In addition, when the self-hardening material is press-fitted, the injection pipe 3 is gradually pulled upward from the bottom of the mud column, and the self-hardening material G is filled so as to gradually accumulate from the bottom.
In addition, it is preferable to perform press-fitting while maintaining the immersion length of the injection pipe 3 in the self-hardening material G. The immersion length is preferably at least 30 cm, more preferably at least 50 cm.

FIGS. 4 and 5 show the manner in which the self-hardening material G is press-fitted. 5 in FIG. 5 indicates aging. From these drawings, it will be understood that when the self-hardening material of the present invention is pressed, the material is pressed into a cream. In the present invention, as the self-hardening material, a self-hardening material such as a cement mortar type, a cement clay type, and a lime type can be used, and a material having a high viscosity is used as described above. Among them, cement mortar is most preferable, and other inorganic materials such as fine particle slag and bentonite, and various additives such as a foaming agent, a foaming agent, a separation preventing agent, and a water reducing agent can be added thereto. . Furthermore, water glass and its hardener can be added in a certain ratio.

The first embodiment has a relaxation tube 2 and an injection tube 3.
6 and FIG. 7, the formation of the primary relaxation region S ₁ and the secondary relaxation region S ₂ is performed using the same injection pipe 3A.
And the injection of the self-hardening material G is also performed by the injection pipe 3A. In the second specific example, for example, the inner pipe 33 and the outer pipe 34 shown in FIG.
In addition, a flow path 35 is provided in the gap between them, and the inside of the inner pipe 33 is used as a flow path for the self-hardening material G. The flow path 35 allows the flow path of each high-pressure water to the first injection nozzle 31A and the second injection nozzle 31B. It is formed.

The first injection nozzle 31A is provided on the outer peripheral surface of the injection pipe 3A, and at the base side of the first injection nozzle 31A, as in the first specific example described above, an overhanging injection part protruding outside the pipe. 30 are integrated. Outward relative improvement axis on the projecting jetting portion 30, a second injection nozzle 31B is provided a high-pressure water that reach injecting farther than outer end of ChoIzuru噴morphism 30 I have. Further, a spout 32 for the self-hardening material is formed on the tip side from the first injection nozzle 31A.

When using the injection pipe 3A, first, as shown in FIG. 6, the injection pipe 3A is inserted to a certain depth in the ground while high-pressure water is injected from the first injection nozzle 31A. At this time, drilling water can be discharged from the spout 32. Next, when a certain depth is reached, FIG.
As shown in, while raising rotating the injection pipe 3A, to inject high-pressure water only from the second discharge nozzle 3 1 B, the secondary relaxation zone to form a S ₂ to the outside of the primary relaxation zone S _1, The self-hardening material G is press-fitted from the spout 32. The improved body A is formed from the self-hardening material G to a certain length.

FIGS. 9 and 10 show a third specific example. Prior to inserting the injection pipe 3 into the ground, the distance between the tip of the overhanging injection section 30 and the axis of the injection pipe is determined in advance. After digging the casing using the casing 4 with a diameter having a large radius, the injection pipe 3 is inserted into the casing 4,
With the casing 4 removed, in the process of rotating and raising the injection pipe 3, high-pressure water is injected from the injection nozzle 31 to relax the ground, and the self-hardening material G can be press-fitted from the spout 32.

As shown in FIG. 11, a plurality of, for example, two overhanging injection sections of the present invention can be provided separately in the length direction. In this case, the high pressure water from the first injection nozzle 31A, the high pressure water from the second injection nozzle 31B, the high pressure water from the first injection nozzle 31A, and the high pressure water from the second injection nozzle 31B, respectively, are relaxed. Formed and finally the third
The high-pressure water from the injection nozzle 31C promises to create an improved body having a radius larger than the overhang length of the overhang injection section 30B. Further, in this example, as in the examples shown in FIGS. 1 to 3, after the ground is first relaxed by the relaxation pipe 2, it is not necessary to insert the injection pipe 3 again, and only the injection pipe 3C is used. Thus, the insertion, the relaxation of the ground, and the injection of the self-hardening material from the spout 32 after reaching the lowermost portion can be performed.

If this idea is developed, as shown in FIG. 12, for example, a protruding injection section 30C formed by triangular blades is provided, and injection nozzles 31E, 31E.
Can be used for relaxing the insertion of the injection pipe 3C, and in order to increase the improved diameter, an example in which high-pressure water is injected from the injection nozzle 31D of the outermost diameter portion to the periphery can be adopted.

Further, as shown in FIG. 13, downward spray nozzles 31E, 31E... Are provided on the lower surface of the overhanging spray section 30, and can be used for relaxation for inserting the spray pipe 3C.

FIG. 14 shows a structure in which a stirring blade 40 is provided above the overhanging jetting section 30. The stirring blade 40 further loosens the loose ground, and if the rotation resistance of the injection pipe 3C is excessively large. For example, since it can be determined that the diameter does not have a predetermined relaxation diameter, it can be used as a determination index member.

In the above example, the overhanging injection portion protrudes outward from the tube from the beginning, but at least the overhanging injection portion only needs to "project outside the tube in the expanded diameter ejection state". As shown in FIG. 15 and FIG. 16, it does not protrude to a certain depth, and when it reaches a predetermined depth, for example, by providing a wing expanding link mechanism blade 41, and starting at the time when it is necessary to expand the diameter, FIG. Thus, the blade 41 of the blade link mechanism can be expanded.拡翼linkage blade 41 may拡翼by pushing the outer tube 42 from the ground. 4
3 is a drilling blade.

When the diameter is to be increased only in a certain length in the depth direction in the ground, as shown in FIG. 17, the diameter of the hole at the mouth is small, and the diameter of the portion for forming the improved body is large. it can.

In the examples shown in FIGS. 11 to 16, the self-hardening material is inserted into the injection port 32 of the injection pipe inserted to a certain depth.
To form an improved body. Although it is not impossible to press-fit a self-hardening material using a separate press-fitting pipe, workability is significantly reduced.

In the above example, the distance between the lowermost injection nozzle and the self-hardening material spout 32 should be at least 50.
When about cm, preferably 1 m or more is secured, there is no interference between the high-pressure water and the self-hardening material G, and a good improved body can be obtained.

In the present invention, the pressure of the high-pressure water is
It usually refers to the pressure of a gauge provided near the injection pipe or on the outlet side of the injection pump. The pressure is 50 kg / cm ²
Although it is preferable to set it as above, in some cases, 100 kg / cm ²
It may be preferable to make the above. The amount of water injected is preferably 5 to 150 liters / minute, particularly preferably 20 to 100 liters / minute. As the injection tube in the present invention, one having an outer diameter of usually 120 mm or less, more preferably 80 mm or less can be used.

On the other hand, as high-pressure water for relaxing the ground,
The use of water is preferred in terms of availability and cost, but the addition of a surfactant to water enhances the machinability of the ground. Further, after the mud generated by the injection of the relaxed / self-hardening material is separated into a supernatant and a concentrated mud, the supernatant can be used. For example, as shown in FIG. 18, by providing a mud pit 50 on the mouth of the high-pressure injection pipe 3 A, with the substitution by self-hardening material G, a high-pressure injection pipe 3
The mud 51 that has risen between A and the hole wall is pumped up by a pump 52 and separated into a supernatant 51A and a concentrated mud 51B by a separator 53, and the supernatant 51A is temporarily stored in a tank 58 by a pump 54. Store and use as high-pressure water for subsequent loose mud column formation. When the supernatant is used for cutting, small particles are included, so that the cutting property is improved. On the other hand, the concentrated mud 51B passes through the hopper 55,
After being supplied to the mixing drum 56 and mixed therewith with the self-hardening material G, the high pressure injection pipe 3A
Can be supplied as a self-hardening material for filling or replacement. Further, when the concentrated mud is reused, muddy water treatment is reduced correspondingly. In addition, the mud 51 can be added to the self-hardening material G without processing.

According to the present invention, a high strength improved body can be obtained, so that a high strength pile can be formed. In addition, by continuously connecting the piles, as shown in FIG.
Pillar piles or pillar rows (continuous walls) can also be created. In this case, the improved body is formed only by the self-hardening material, and the improved body is reinforced by inserting one or a plurality of reinforcing bars or appropriately shaped steel (referred to as reinforcing bars) into the improved body. Is preferred. Furthermore, since one injection pipe has a small diameter and light weight when constructing a pillar row or a pillar row wall, a plurality of pipes are gripped by one elevator,
The ground can be improved by raising and lowering the injection pipe group at the same time.

In the above example, after the ground is relaxed, the injection of the high-pressure water from the injection pipe is stopped, and the injection pipe is fixed at the depth position, and only the self-hardening material is poured out. May be performed.

[0043]

As described above, according to the present invention, the improvement strength is increased, the construction can be performed with simple and small equipment, and the uniform and strong improvement limited only by the consolidation effect or only at the intended portion is achieved. Advantages are obtained such that the body can be formed and the diameter of the improved body can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a first step showing a first specific example in the order of construction.

FIG. 2 is a schematic diagram of a second step showing a first specific example in the order of construction.

FIG. 3 is a schematic diagram of a third step showing a first specific example in the order of construction.

FIG. 4 is a schematic diagram of a press-fit state of a self-hardening material.

FIG. 5 is a schematic sectional view of a press-fitting mode of a self-hardening material.

FIG. 6 is an insertion state diagram of another example.

FIG. 7 is a state diagram of a lifting process of the example.

FIG. 8 is a longitudinal sectional view of an example of an injection tube.

FIG. 9 is a vertical cross-sectional view of a state in which the casing is installed.

FIG. 10 is a longitudinal sectional view of a subsequent pulling process.

FIG. 11 is another view of a modified example of the injection tube.

FIG. 12 is another view of a modified example of the injection tube.

FIG. 13 is a view of still another example of the injection tube.

FIG. 14 is a schematic diagram of an example of an injection tube having an agitating blade.

FIG. 15 is a schematic diagram of an example of a wing expansion type.

FIG. 16 is a view showing a state of a wing expansion in an example of a wing expansion system.

FIG. 17 is a schematic diagram of another example of a ground improvement mode.

FIG. 18 is a schematic diagram of an example of reusing mud.

FIG. 19 is a plan view of an example of forming a pillar row or pillar wall.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Injection nozzle 2 ... Relaxation tube 3, 3A, 3B, 3C ...
Injection tube, 30, 30A, 30B ... overhanging injection portion, W: high-pressure water, G: self-hardening material.

Continuation of front page (72) Inventor Masatoshi Ogita 3-19-19 Higashi 3-chome, Kunitachi-shi, Tokyo (56) References JP-A-5-255925 (JP, A) JP-A-57-3911 (JP, A ) Special table 63-503230 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02D 3/12 101

Claims (5)

(57) [Claims] 1. An overhanging injection portion projecting at least at the tip end of an injection tube in a state of expanded diameter injection is provided, and high-pressure water is injected outward from the improved injection center to the overhanging injection portion. The injection nozzle of the self-hardening material is further formed on the injection pipe at the tip side of the injection nozzle, and the injection pipe is inserted into the ground to be improved, and is rotated around the axis.
In the process of raising in the axial direction, high-pressure water is injected from the injection nozzle in a state where the overhanging injection portion is protruded outward from the pipe, thereby relaxing the ground outside the injection direction of the injection nozzle to form a loose mud column. A method for improving or strengthening the ground, characterized in that a hardened self-hardening material is discharged from the spout port into or out of the loose mud column while forming or after forming to form an improved body. 2. A first injection nozzle for jetting high-pressure water in a radial direction is provided at an end portion of an injection pipe on an outer peripheral surface, and protrudes outward from the pipe in at least an expanded diameter injection state at a base side of the first injection nozzle. overhanging injection portion provided outward with respect to improvements axis on the projecting jetting portion, the second injection nozzle high-pressure water that reach injecting farther than outer end of ChoIzuru噴morphism portion And a spout of a self-hardening material is formed on the tip side from the first injection nozzle. This injection pipe is inserted into the ground to be improved, and the rotation around the axis is performed.
In the process of raising in the axial direction, high-pressure water is jetted from at least the second jet nozzle among the jet nozzles in a state where the overhanging jet portion is projected outside the pipe, so that the jet jet direction of the second jet nozzle is shifted outward. While forming or forming a relaxed mud column by relaxing the ground, the improved self-hardening material is discharged from the spout into the relaxed mud column by press-fitting to form an improved body. Improvement or reinforcement method. 3. The high-pressure water reaching distance from the first injection nozzle is made longer than the projecting length of the overhanging injection portion, and at least when the injection pipe is inserted into the ground, the high-pressure water is transmitted from at least the first injection nozzle. 3. The method for improving or strengthening the ground according to claim 2, wherein the injection pipe is inserted while loosening the ground by injecting water. 4. When the injection pipe is inserted into the ground, the casing is excavated with a diameter having a radius larger than the distance between the tip of the overhanging injection section and the axis of the injection pipe, or The injection pipe is inserted into the casing, and in a state where the casing is removed, the reaching distance of the high-pressure water from the first injection nozzle is set farther from the outer surface of the casing, and the high-pressure water is injected from the first injection nozzle to form the ground. And the distance of the high-pressure water from the second injection nozzle is made longer than the distance from the first injection nozzle.
3. The method for improving or strengthening ground according to claim 2, wherein the ground is loosened by injecting high-pressure water also from the injection nozzle. 5. An overhanging injection section is configured to be able to expand and contract between a folded position along an axis of the injection pipe and a position protruding outward by operation from the ground, and to be in a contracted state when the injection pipe is inserted. 3. The method for improving or strengthening the ground according to claim 1, wherein the projection is made to protrude when high-pressure water is injected from an injection nozzle provided in the overhanging injection section.