JP2001055727A - Slant jet method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slant jet method wherein labor concerning the underground consolidation body formation extended in the approximately horizontal direction can be saved. SOLUTION: A boring-hole extended in the approximately horizontal direction is excavated by using an inner rod 1 having a monitor 3 at the front end and an outer casing 5, an area 50 of the end on the ground side of the outer casing 5 is removed, the outer casing 5 is drawn in by the area to be removed to expose the monitor 3 and the front end of an inner rod 1, soil improvement material is jetted from the monitor 3, the monitor 3 and inner rod 1 are drawn out while rotating them, and the outer casing 5 is drawn out by following the draw of the inner rod 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of the so-called "slant jet method".

[0002]

2. Description of the Related Art A jet method for forming an underground solid body extending in a substantially horizontal direction (more precisely, in a diagonal direction with a slight inclination angle with respect to a horizontal plane) in the ground. Is known by the name "Slant Jet Method".

In carrying out this method, first, a boring hole extending in a substantially horizontal direction (more precisely, an oblique direction with a slight inclination angle with respect to a horizontal plane) is drilled. Then, a monitor for injecting the ground improvement material jet into the excavated borehole and a pipe for supplying the ground improvement material to the monitor are inserted, and while the ground improvement material jet is jetted from the monitor, the pipe is And rotate the monitor and pull it up. By rotating and pulling up the pipe and the monitor, the ground is cut by the ground improvement material jet, and the cut ground and the ground improvement material are mixed.
Then, an underground consolidated body is formed by the mixture of the ground ground and the ground improvement material that has been cut.

[0004] Here, the formed underground consolidated body extends in a direction in which the borehole extends (in other words, a direction in which the pipe and the monitor are pulled up). As described above, the boring hole extends in a substantially horizontal direction (more precisely, an oblique direction with a slight inclination angle with respect to a horizontal plane). Therefore,
The formed underground compact also extends in a substantially horizontal direction (a diagonal direction with a slight inclination angle with respect to the horizontal plane).

In the prior art, a boring machine such as a rotary percussion boring machine is used for drilling a boring hole, and a ground improvement material supply device and a pipe (or rod) are used for forming an underground solidified body. ) Had to be used with an automatic pulling device. That is, at the same construction site, first install a boring machine, remove the boring machine when boring hole drilling is completed, install a ground improvement material supply device and an automatic rod pulling device, and then create an underground solidified body The process had to start.

In many cases, the formation of an underground consolidated body is performed over a plurality of lines. In such a case, a boring machine, a ground improvement material, The installation and removal of the supply device and the automatic rod pulling device had to be repeated, and the labor expended there was great.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned prior art, and is intended to reduce the labor required for forming an underground solid body extending in a substantially horizontal direction. The purpose is to provide the slant jet method.

[0008]

According to the slant jet method of the present invention, a boring hole extending in a substantially horizontal direction using an inner bit (1) provided with a monitor (3) at the tip and an outer casing (5). Excavation, and the area (50, 50) of the ground side end of the outer casing (5).
A, 50B, 50C) and the monitor (3) by retracting the outer casing (5) by the removed area (50, 50A, 50B, 50C).
And exposing the tip of the inner rod (1);
A step of injecting (GJ) the ground improvement material from the monitor (3) and pulling out the monitor (3) and the inner rod (1) while rotating the outer casing (5) following the pulling out of the inner rod (1); ).

In practicing the present invention, the area (50A) of the ground side end of the outer casing (5) is provided with a main body (5) formed by spirally arranging plate-like materials (53).
2) and upper and lower adapters (54, 56) connected to the main body (52), wherein the upper and lower adapters (54, 56) are formed with screw portions (58, 60), Further, a fixing pin (for example, three pins: 62) is configured to be insertable, and the fixing pin (62) restrains the plate-like material (53) and holds the main body (52) in a cylindrical shape. It is preferable to be configured in such a manner (FIGS. 3 to 7).

Alternatively, the area (50B) at the ground side end of the outer casing (5) is divided by dividing the pipe (5P) into a plurality of members (50B1, 50B2) (for example, halving). Individual parts (50B1, 50B
2) is preferably integrated into a single pipe by a separation preventing member (for example, a band 70) (FIG. 1).
0, FIG. 11).

Further, the area (50C) of the ground side end of the outer casing (5) is constituted by concentrically arranged multiple pipes (for example, double pipes: inner pipes 50C1L, 50C1R, outer pipe 50C2), The multiple pipe (inner pipe 50C1)
L, 50C1R, and outer tube 50C2) are mutually slidable (the inner tube 50C1R and the outer tube 50C2 are slidable), and the individual tubes (the inner tube 50C1R and the outer tube 50C2) are liquid-tightly configured (sealed). 74) (FIGS. 12 to 14).

[0012] In addition, when the present invention is implemented,
As the inner rod (1), it is preferable to use an ordinary inner rod modified for high pressure resistance. Also, a monitor at the tip of the inner rod (1) (3: monitor for excavation)
Is preferably provided with a so-called button bit.

[0013] Then, the monitor (3) may switch to inject cement milk or other soil improvement material during formation of the underground solidified body after drilling the boring hole by injecting drilling water. Preferably, it is configured to be possible. Here, in order to switch between the drilling water injection at the time of drilling and the ground improvement material injection at the time of underground consolidated formation, for example, a steel ball is dropped at the time of switching and the drilling water injection passage is closed. Is preferred.

A swivel joint for transmitting rotation to a double pipe composed of the inner rod (1) and the outer casing (5) is preferably constructed to withstand the impact of a rotary percussion.

According to the present invention having the above-described structure, it is possible to switch to inject the ground improvement material after injecting the drilling water and drilling the boring hole. By mounting the monitor, the boring hole drilling step and the underground solid body forming step can be performed by a single machine. As a result, there is no need to repeat the installation and removal of a boring machine, ground improvement material supply device, and automatic rod pulling device at each underground solidification site, and the labor required for the slant jet method is greatly reduced. Is done.

In the slant jet method, a boring hole extending in a substantially horizontal direction is drilled. Such a boring hole (extending in a substantially horizontal direction) is formed in comparison with a boring hole which is preceded in a vertical direction. , Easy to collapse. And when the boring hole is closed due to collapse, pull out of the rod,
Discharge of the slurry becomes difficult, and ground improvement becomes difficult.
Therefore, in the present invention, drilling of a boring hole and formation of an underground solidified body are performed using the outer casing (5) and the inner rod (1). That is,
The use of the outer casing (5) and the inner rod (1) allows the outer casing (5) to bear the earth pressure of the ground, thereby securing an annular space between both pipes and boring. The holes are prevented from collapsing and closing.

Here, since the boring hole is drilled and the underground solidified body is formed using the outer casing (5) and the inner rod (1), especially when the underground solidified body is formed. There is a demand that the monitor (3) for injecting the jet jet (GJ) of the ground improvement material must be exposed from the outer casing (5). If the monitor (3) is not exposed from the outer casing (5), the ground cannot be mixed with the cutting paper and the ground improving material by the jet jet (GJ) of the ground improving material.

However, if only the outer casing (5) is pulled out in order to cope with such a demand, the boring hole collapses, causing inconveniences such as clogging of the slurry and occurrence of a jamming phenomenon. On the other hand, since the outer casing (5) and the inner rod (1) have too different diameters, it is difficult to pull out both (1, 5) simultaneously with the current technology. Further, if the monitor (3) is housed in the outer casing (5) because the inner rod (1) is pulled out too far, the ground improvement material jet (GJ) ejected from the monitor (3).
Only collides with the inner wall surface of the outer casing (5), so that the ground cannot be cut and mixed.

On the other hand, according to the present invention having the above-described configuration, the area (50, 50A, 50B, 50C) of the ground side end of the outer casing (5) is removed.
The removed area (50, 50A, 50B, 50
C) The outer casing (5) for the amount (to the ground side)
Pull in the monitor (3) and inner rod (1)
The outer casing (5) is configured to be pulled out following the removal of the inner rod (1) after exposing the tip of the inner casing (5). The area (50, 50A, 50B, 50C) of the ground side end of the outer casing (5) is removed, and the outer casing (5) is retracted (to the ground side) by that amount and the monitor (3) and the inner rod (1) are pulled out. In the state where the tip of ()) is exposed, the tip of the outer casing (5) is pulled back to the ground side from the monitor (3) at the tip of the inner rod (1) by the length of the area (50). Therefore, the monitor (3) is exposed without being accommodated in the outer casing (5).

If the outer casing (5) is pulled out following the pulling-out of the inner rod (1), the inner rod (1) and the monitor (3) can be extended to a length corresponding to the area (50). Only after pulling out to the ground side and the monitor (3) is positioned near the tip of the outer casing (5), the outer casing (5) is pulled out to the ground side by the same length, and thereafter, the same operation is repeated. . Thereby, the monitor (3) is maintained in an exposed state without being accommodated in the outer casing (5). Moreover, the length of the inner rod (1) including the monitor (3) exposed from the outer casing (5) is at most only the length of the area (50).
Therefore, the length of the region of the boring hole in which the outer casing (5) does not support the earth pressure is much shorter than when the inner rod (1) is completely exposed,
The possibility of blockage due to collapse is low.

In addition to this, according to the present invention described above,
In the area of the ground side end of the outer casing (5) (50,
50A, 50B, and 50C) are variously devised so as to be extremely easily removed.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the same members are described with the same reference numerals.

FIGS. 1 and 2 show a drilling hole excavating step in the slant jet method according to the present invention (FIG. 1).
And a step (FIG. 2) of jetting a jet to form an underground solid body extending in an oblique direction.

In FIG. 1, a machine indicated by reference numeral 10 is configured as a rotary percussion boring machine in the illustrated embodiment, and can be moved by moving means (for example, wheels) 12. However, as described later, this machine 10 also functions as a lifting device for the inner rod 1, the monitor 3, and the outer casing 5.

A base 12 is mounted on an upper part of the machine 10. An inner rod grip 16 for gripping the inner rod 1 and an outer casing 5 are mounted on the base 12.
And an outer casing connecting portion 18 connected to the outer casing.

Here, the inner rod 1 is obtained by modifying a normal inner rod for high pressure resistance. A monitor 3 (excavation monitor) at the tip of the inner rod 1 is provided with a so-called button bit. The monitor 3 is configured to be capable of switching to inject cement milk or other soil improvement material at the time of forming an underground solidified body after drilling a boring hole by injecting drilling water. And, in order to switch between excavation water injection at the time of drilling and ground improvement material injection at the time of underground consolidated formation, for example,
It is preferable to drop the steel ball at the time of switching to close the drilling water injection passage.

Further, the outer casing connecting portion 18
This is a swivel joint for transmitting rotation to a double pipe composed of the inner rod 1 and the outer casing 5, and has a structure that can withstand the impact of a rotary percussion.

The inner rod holding portion 16 is
A through-hole that is configured to be slidable on the top and that penetrates the end of the inner rod 1 is formed to grip the inner rod 1. On the other hand, the outer casing connecting portion 18 has drilling water for boring hole drilling (FIG. 1).
In FIG. 1, there is provided a supply pipe 20 for supplying a slurry (shown by an arrow W), and a discharge pipe 22 for discharging slurry (shown by an arrow S in FIG. 1) generated during drilling of a boring hole. In addition, the supply pipe 20 and the discharge pipe 22 are not used only at the time of drilling a boring hole. Details will be described later.

Drilling water W supplied through supply pipe 20
Is jetted from the monitor 3 at the tip of the inner rod 1 as a drilling water jet CJ, excavates the ground and drills a boring hole. Then, the slurry S generated during drilling
Flows through an annular space between the inner rod 1 and the outer casing 5 and is discharged to a slurry processing mechanism (not shown) via a discharge pipe 22.

In FIG. 1, reference numeral 24 denotes a laser device. The laser device 24 includes target rods 26 (points near the face 30) and 28 (points behind the machine 10), the inner rod 1, and the moat. The cutting monitor 3 and the outer casing 5 have an effect of measuring the direction of excavation of a boring hole excavated by the outer casing 5.
That is, by irradiating the laser beam from the laser device 24 to the point 26 provided on the face and the point 28 behind the machine, the boring operation can be performed while monitoring the drilling direction.

When excavating the borehole, the monitor 3
Excavation water jet CJ is blown out from the ground to excavate the ground.
At the same time, the monitor 3, the inner rod 1, and the outer casing 5 are pushed in by the grip portion 16 sliding on the base 14 toward the face 30, and a boring hole is drilled. As described above, since the underground solid body extending in the substantially horizontal direction is formed, the boring hole is excavated in the substantially horizontal direction (more specifically, in the oblique direction slightly descending to the left in FIG. 1). .

In the boring hole drilling step, the outer casing 5 is added in a region between the face 30 and the outer casing connecting portion 18. On the other hand, in the underground consolidated body formation process shown in FIG.
Is cut off in a region between the face 30 and the outer casing connecting portion 18.

Here, the monitor 3 needs to be exposed from the outer casing 5 when forming the underground solid compact. Therefore, when the boring hole drilling is completed, the region of the outer casing 5 at the end on the connecting portion 18 side can be easily removed. In FIG. 1, the region of the outer casing 5 at the end on the side of the outer casing connecting portion 18 is represented by hatching, and only the region is represented by reference numeral 50. The area 50 of the outer casing 5 at the end on the outer casing connecting portion 18 side will be described later in detail.

When the drilling of the boring hole is completed, the supply of the drilling water W is stopped, the steel ball is dropped from the boring machine 10 side, and the monitor 3 is switched. The area 50 of the outer casing 5 (the area shown by hatching in FIG. 1) according to various aspects described later.
Is removed, and the outer casing 5 is pulled out toward the machine 10 by a length corresponding to the area 50. Thereby, the monitor 3 is exposed from the outer casing 5.

After the monitor 3 is exposed from the outer casing 5, as shown in FIG. 2, the ground improvement material is jetted from the monitor 3 as a jet (the jet is denoted by GJ), and the ground is cut and the ground improvement material is removed. Mix. as a result,
An underground solidified body indicated by reference numeral GI is created. Here, as described above, the borehole is excavated in a substantially horizontal direction (more precisely, in FIGS. 1 and 2, an oblique direction in which the left side is slightly lowered and the right side is slightly raised). Body GI
Are also formed so as to extend in a substantially horizontal direction (slightly oblique direction).

When forming the underground solidified body GI, the supply pipe 2
0 is connected to a source of cement milk or other soil conditioner. On the other hand, the slime that appears during the formation of underground
The area from the monitor 3 to the tip of the outer casing 5,
It is discharged to a slurry processing mechanism (not shown) via a discharge pipe 22 and an annular space between the inner rod 1 and the outer casing 5.

At the time of construction shown in FIG. 2, the outer casing 5 is pulled out following the pulling-out of the inner rod 1. If only the outer casing 5 is pulled out, as described above, the boring hole collapses, causing inconveniences such as clogging of the slurry and occurrence of a jamming phenomenon.
On the other hand, if the inner rod 1 is pulled out too much and the monitor 3 is accommodated in the outer casing 5, it becomes impossible to cut and mix the ground with the ground improvement material jet GJ. On the other hand, if the outer casing 5 is pulled out following the pull-out of the inner rod 1, the outer casing 5 is larger than the inner rod 1 by the length of the hatched area 50 in FIG. Since it is short, a state where the monitor 3 is not accommodated in the outer casing 5 is ensured. Moreover, the length of the inner rod 1 including the monitor 3 exposed from the outer casing 5 is at most
It is only the length of the area 50. Therefore, as compared with the case where the inner rod 1 is completely exposed, the length of the boring hole that is not held by the outer casing 5 is much shorter, and the possibility of blockage due to collapse is reduced.

Next, a region 50 of the outer casing shown by hatching in FIG. 1 (a portion to be removed for forming an underground solid body after completion of boring hole drilling).
And the manner of removal thereof will be described with reference to FIGS.

The area 50A of the outer casing shown in FIG. 3 to FIG. 7 is formed by applying a plate-like material having a width dimension α (hereinafter simply referred to as “plate”) in the longitudinal direction (vertical direction in FIGS. 3 and 4).
4 is formed in a roll shape (spiral shape).
(Refer to FIG. 2) The general configuration is made up of a main body 52, an upper adapter 54 and a lower adapter 56 connected to the main body 52. The upper adapter 54 has a female screw 58 and the lower adapter 56 has a male screw 60.

Here, the plate 53 constituting the main body 52 is
It is made of a metallic material such that when the restraint is released, an elastic repulsion acts to expand the diameter outward in the radial direction. Therefore, if nothing is restrained, it spreads as shown in FIG. 4 and cannot function as the outer casing 5 (FIG. 1). Therefore, a plurality (for example, three as shown in FIG. 3) of fixing pins indicated by reference numeral 62 are inserted from the upper adapter 54 to the lower adapter 56.
If the fixing pin 62 is fixed by any means in the lower adapter 56, the plate 53 can be restrained from the radially inner side (right side in FIG. 6) as shown in FIG. As a result of being constrained by the fixing pins 62 from the radial inside and being constrained by a plate located at a position deviated in the longitudinal direction by the width dimension α, the plate 53 becomes cylindrical as shown in FIG. It is in shape. In the state shown in FIG. 3, the longitudinal dimension of the region 50A is represented by a reference numeral L1. Note that, as shown in FIG. 5, it is preferable that the fixing pins 62 are arranged at equal intervals in the circumferential direction, as shown in FIG.

In the boring hole excavation step shown in FIG. 1, when attached to the outer casing 5, the area 50A (corresponding to reference numeral 50 in FIG. 1) is in a state as shown in FIG. When the drilling of the boring hole is completed and the monitor 3 (FIGS. 1 and 2) has to be exposed from the outer casing 5, the fixing pins 62 are removed from the state of FIG. Plate 5 as shown
Let it be in a state where the constraint acting on 3 has disappeared.

In the state shown in FIG. 4, the plate 53 in an unconstrained state can be easily disconnected from one of the adapters 54 and 56. Then, if the plate 53 is removed, as shown in FIG. 7, the longitudinal dimension of the remaining portion is the longitudinal length of the upper and lower adapters 54 and 56 (connected by the connecting member 64 in FIG. 7). , And its length is indicated by a symbol L2 in FIG. As is apparent from a comparison between FIGS. 3 and 7, L1> L2
Therefore, the length in the longitudinal direction is reduced by “L1−L2”. As a result, the tip of the inner rod 1 (the monitor 3
The side) is exposed from the outer casing 5 by a longitudinal distance “L1-L2”. Note that the adapter 5
The parts 4 and 56 can also be configured so that they can be split in half and can be removed. In that case, the length of the end of the inner rod 1 (the monitor 3 side) exposed from the outer casing 5 is L2.

FIGS. 8 to 11 illustrate another example (the member denoted by reference numeral 50B in FIGS. 10 and 11; hereinafter, referred to as a "member") in the area 50 of the outer casing 5 described above. It is. A member obtained by dividing the normal pipe 5P shown in FIGS. 8 and 9 in half is indicated by a reference numeral 50B in FIGS. 10 and 11 as a whole. In this member 50B, the respective halved parts are 50B1, 50B.
The area 5 of the outer casing 5 is represented by B2.
When used as 0B, the components 50B1 and 50B2 are integrated with a band 70 so that they do not separate. Here, the members for preventing the components 50B1 and 50B2 from being separated are not limited to the bands 70. The components 50B1 and 50B2 may be integrated using members other than the band as long as they do not protrude significantly from the outer peripheral surface of the outer casing 5 and have a necessary strength.

When the drilling of the boring hole is completed, the monitor 3
When exposing (FIGS. 1 and 2) from the outer casing 5, the bands 70 are removed from the state of FIGS. 10 and 11, and the member 50B may be divided into components 50B1 and 50B2. Other steps and processes are the same as described above.

FIGS. 12 to 14 show another example (FIGS. 12 to 14) of the region 50 of the outer casing 5 described above.
, A member denoted by reference numeral 50C: hereinafter, referred to as a “member”). The member 50C shown in FIGS. 12 to 14 is configured as a so-called “nested type (telescopic type)”.

In FIG. 12, members indicated by the reference numeral 50C are the inner tube 50C1L (the inner tube on the left in FIGS. 12 and 14) and 50C1R (the inner tube on the right in FIGS. 12 and 14) and the outer tube. And a tube 50C2. The outer pipe 50C2 is configured to be slidable with respect to the right inner pipe 50C1R in FIGS.

Here, in order to determine the slide position between the inner tube 50C1R and the outer tube 50C2, stoppers 72, 76 are provided.
Is provided. Also, the inner pipe 50C1R and the outer pipe 50C
2 and seals 74 for ensuring a liquid-tight state between them.
Are provided on the inner peripheral surface of the outer tube 50C2.

When drilling a boring hole shown in FIG.
As shown by 2, the inner tube 50C1R is located outside (to the right in FIG. 12) with respect to the outer tube 50C2, and the longitudinal length of the member 50C is maximum. Here, as shown in FIG. 13, a key and a keyway for transmitting rotation are provided at the boundary between the inner pipe 50C1 and the outer pipe 50C2 (in FIG.
Is provided, the member 50C is
The necessary rotation is performed as a part or area of the outer casing 5.

When the drilling of the boring hole is completed, the monitor 3
When exposing (FIGS. 1 and 2) from the outer casing 5, the stopper 72 is released and the inner tube 50C1R is released.
May be slid with respect to the outer tube 50C2 and inserted into the outer tube 50C2. Fig. 14
In the state shown in FIG. 12, the longitudinal dimension of the member 50C is reduced by the sliding distance. The sliding distance is the length of the inner rod 1 (FIGS. 1 and 2) including the monitor 3 exposed from the outer casing 5. Other operations are the same as described above.

The illustrated embodiment is merely an example,
It is not a statement to limit the technical scope of the present invention. It is noted that the illustrated embodiment can be modified or changed without reducing the technical scope of the present invention.

[0051]

The effects of the present invention are listed below. (1) Drilling boring holes with a single machine,
Underground solidification can be created. (2) At the time of forming an underground solidified body, it is necessary to prevent boring holes from collapsing and to cut and mix the ground with the ground improvement material jet when jetting the ground improvement material jet. You can do it. (3) There is no need for complicated work, and there is no possibility of increasing construction costs. (4) Necessary and sufficient work accuracy can be maintained.

[Brief description of the drawings]

FIG. 1 is a front view showing a boring hole excavation step in an embodiment of the present invention.

FIG. 2 is a front view showing an underground consolidated body forming step in the embodiment of the present invention.

FIG. 3 is a front view showing a state of a boring hole excavation step in an example of a machine-side end region of an outer casing used in the present invention.

FIG. 4 is a front view showing an example of a machine-side end region of the outer casing shown in FIG. 3 with a fixing pin removed.

FIG. 5 is a side view of FIG. 3;

FIG. 6 is a partial enlarged view showing an example of a machine-side end region of the outer casing shown in FIG. 3, showing a state where the outer casing is restrained by fixing pins.

FIG. 7 is a diagram showing an example of a machine-side end region of an outer casing used in the present invention, showing a state of an underground solid body forming step.

FIG. 8 is a front view of a normal pipe.

FIG. 9 is a side view of the pipe of FIG. 8;

FIG. 10 is a front view showing another example of a boring hole excavating step in a machine-side end region of the outer casing used in the present invention.

FIG. 11 is a side view of FIG. 10;

FIG. 12 is a front view showing another example of a boring hole excavation step in a machine-side end region of the outer casing used in the present invention.

FIG. 13 is a side view of FIG. 12;

FIG. 14 is a front view showing an example of an underground solid body forming step in an example of an end portion region on the machine side of the outer casing in FIG. 12;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inner rod 3 ... Monitor 5 ... Outer casing 10 ... Machine 12 ... Base 16 ... Inner rod gripping part 18 ... Outer casing connecting part 20 ... Supply pipe 22 ... Discharge pipe W ... Drilling water CJ ... Drilling water jet S ... Slurry 24 ... Laser devices 26 and 28 ... Target point 30 ... Face GJ ... Ground improvement material jet GI ... Underground solidified body 52 ... Main body 53 ... Board 54 ... Upper adapter 56 ... Lower adapter 58 ... Female screw 60 ... Male screw 62 ... Fixing pin 5P ... Normal pipe 50B1, 50B2 ... Half-split parts 70 ... Band 50C1L, 50C1R ... Inner pipe 50C2 ... Outer pipe 72, 76 ... Stopper 74 ... Seal 78 ... Key

Claims (4)

[Claims] A step of excavating a boring hole extending in a substantially horizontal direction using an inner bit provided with a monitor at an end thereof and an outer casing; and removing a region of a ground side end of the outer casing; A step of retracting the outer casing by an amount corresponding to the removed area to expose a tip of the monitor and the inner rod; a step of injecting a ground improvement material from the monitor, and a step of rotating and pulling the monitor and the inner rod; A step of pulling out the outer casing following the pulling out of the rod. 2. An area of the ground side end of the outer casing includes a main body configured by arranging a plate-like material in a spiral shape, and upper and lower adapters connected to the main body. Threads are formed on the upper and lower adapters,
The slant jet method according to claim 1, wherein a fixing pin is configured to be insertable, and the fixing pin is configured to restrain the plate-shaped material and hold the main body in a cylindrical shape. 3. The ground-side end region of the outer casing is formed by dividing a pipe into a plurality of members, and integrating the divided parts into a single pipe by a separation preventing member. Item 1. Slant jet method. 4. The area of the ground end of the outer casing is constituted by concentrically arranged multiple tubes which are slidable relative to one another and which are liquid-tight between the individual tubes. The slant jet method according to claim 1, wherein