JP2001082064A - Drilling tool and drilling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drilling tool and a drilling method capable of setting the rotating position of a casing inserted into a drilled hole at the prescribed position and requiring no vibrating device when the casing is extracted from the drilled hole. SOLUTION: Coupling recesses 15 capable of being coupled or released with or from coupling lugs 26 protruded on the inner periphery of the rear end section of a casing 21 are formed on the outer periphery of a tool body 2 inserted into the tubular casing 21, driven in the direction of the central axis O of the casing 21, and rotated around the axis O. The coupling lugs 26 are coupled with the coupling recesses 15 after a drilled hole is formed, the tool body 2 and casing 21 are integrally rotated while the tool body 2 is driven, or the casing 21 is extracted from the drilled hole together with the tool body 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool used to insert a cylindrical casing into a drilled hole while forming a drilled hole in the ground or the like, and to a drilling method using the drilled tool. is there.

[0002]

2. Description of the Related Art An excavating tool used to insert a cylindrical casing into a hole while forming a hole in the ground or the like as described above is disclosed in, for example, Japanese Patent No. 2599846. A plurality of blocks each having a cutting edge are arranged on a circumference centered on the axis at the tip of a tool body that is hit by a hammer in the direction of the center axis of the casing and rotated around the axis. One that is mounted rotatably about a central axis is known.
In such an excavating tool, when the tool body is rotated in the direction of rotation during excavation, these blocks rotate around the central axis so as to open to the outer peripheral side, and their outer diameters are equal to those of the casing. When the tool body is rotated in the direction opposite to the direction of rotation during excavation, the block is rotated so that the block closes and the outer diameter is adjusted to the inner diameter of the casing. Smaller than.

Therefore, according to such an excavating tool, when excavating, the block of the tool main body is protruded from the tip of the casing and rotated to form a drilled hole having an inner diameter larger than the outer diameter of the casing. After the excavation is completed, the outer diameter of the block becomes smaller than the inner diameter of the casing after the excavation is completed. It is possible to pull out only the tool main body from the hole while leaving the casing inside. A casing top is provided at the distal end of the casing so as to reduce the diameter by one step toward the inner peripheral side, and a step is formed at the outer periphery of the tool body so as to increase the diameter by one step. By hitting the rear end face of the casing top, as the tool body is hit, the casing also receives a striking force and is inserted into the hole.

[0004]

By the way, in recent years, a method of inserting an H-shaped steel pile having an H-shaped cross section into the casing inserted into the drilled hole and embedding it on the ground has been performed. Is coming. In such a construction method, in order to arrange the H-shaped steel pile at a predetermined rotation position with respect to the casing, for example, a notch into which the four edges of the H-shaped steel pile can be inserted into the inner periphery of the casing top, respectively. For example, a positioning portion for positioning the rotation position of the H-shaped steel pile is provided on the inner periphery of the distal end portion of the casing.

However, in the above-mentioned excavating tool, when the casing is hit by the tool main body via the casing top as described above, the casing is inserted into the hole while being rotated little by little with the rotation of the tool main body. Therefore, if the casing is simply inserted in response to the impact of the tool body, the rotational position of the casing itself with respect to the ground or the like will be random. Therefore, even if the casing is provided with the positioning portion as described above, if the rotational position of the casing itself cannot be positioned at a predetermined position, the H-shaped steel pile cannot be arranged at a desired rotational position with respect to the ground, For example, when a large number of H-shaped steel piles are built side by side, it has been difficult to insert and position the H-shaped steel piles in a casing in the same direction.

For example, when drilling holes in a fragile ground, the casing is inserted together with the tool body in order to prevent the drilling holes from collapsing during excavation. After the drilling holes are formed, the casing is removed from the drilling holes. In some cases, they may be extracted. However, in such a case, in order to remove the casing from the hole, the casing is tightened due to the pressure of the ground and cannot be easily removed even if the casing is simply lifted. I have to. Therefore, in such a case, such a vibration device must be prepared in advance and attached to the casing, and after the casing has been pulled out, the work of removing the vibration device from the casing must be performed, which impairs the working efficiency. However, there is a problem that a vibration device is required in addition to the drilling device.

The present invention has been made in view of such circumstances, and it is possible to set the rotation position of a casing inserted into a hole to a predetermined position, and to remove the casing from the hole. However, an object of the present invention is to provide a drilling tool that does not require a vibration device, and also provide a drilling method using the drilling tool.

[0008]

In order to solve the above-mentioned problems and achieve such an object, a drilling tool according to the present invention comprises:
The outer peripheral surface of the tool body, which is inserted into a cylindrical casing and is struck in the direction of the central axis of the casing and rotated about the axis, engages with an engaging projection projecting from the inner periphery of the rear end of the casing. A detachable engaging recess is formed. Therefore, according to such an excavating tool, the tool main body and the casing can be integrally rotated or retracted by engaging the engaging projection with the engaging recess after the hole is formed. At the same time, since the casing is vibrated by hitting the tool body to reduce frictional resistance acting on the casing, the casing inserted into the drilled hole can be reliably and easily rotated to a predetermined rotational position, The casing can be pulled out of the hole without using any device.

Here, in order not to hinder the rotary impact of the tool body during excavation, an engaging pin is attached so as to penetrate the casing after a hole is formed or the like, and the inner peripheral end of the engaging pin is attached to the engaging pin. It is desirable to use an engaging projection, and in this case, in order to prevent the casing from being damaged by the engaging pin, a rotating jig is attached to the outer periphery of the casing,
It is desirable to support the outer peripheral end of the engaging pin on the rotating jig. Further, as the excavating tool, a block provided with a cutting edge at the tip of the tool main body is provided so that the outer diameter from the axis can be increased with the rotation of the tool main body during excavation, and the rotation during this excavation is performed. When the outer diameter from the axis is reduced so that the outer diameter can be reduced with the rotation of the tool body in the direction opposite to the direction, the inner diameter is larger than the outer diameter of the casing by the cutting edge of the block whose outer diameter is increased during excavation. Can form a large drilled hole and insert the casing into this drilled hole, which can secure the space between the casing and the drilled hole and reduce the ground pressure acting on the casing. The above-mentioned rotation of the casing and the removal from the drilled hole can be performed more easily.

On the other hand, the drilling method of the present invention uses such a drilling tool. First, the drill body is hit in the axial direction and rotated around the axial line to form a hole. While the casing is inserted into the hole, then the tool body is retracted to the rear end of the casing while the casing is inserted into the hole, and the engagement protrusion is formed on the inner periphery of the rear end of the casing. After the projecting portion is engaged with the engagement recess, the tool body is again struck and rotated to rotate the casing to a predetermined rotational position. Can be surely and easily rotated to a predetermined rotation position while vibrating. Therefore, after rotating the casing to the predetermined rotation position in this manner, the engaging projection is pulled out of the engaging recess, the tool body is pulled out of the casing, and then an H-shaped steel pile is inserted into the casing to build a hole. In this case, the H-shaped steel pile is provided with a positioning portion for engaging the edge of the H-shaped steel pile and positioning the rotation position of the H-shaped steel pile around the axis at the inner periphery of the tip of the casing. Even when a large number of H-shaped steel piles are laid side by side while being reliably positioned with respect to the casing, it is possible to lay the piles in the same direction.

In the excavation method of the present invention, secondly, the casing is inserted into the hole while the tool body is hit in the axial direction and rotated around the axis to form a hole. Then, the tool main body was retracted to the rear end of the casing while the casing was inserted into the hole, and the engaging projection was provided on the inner periphery of the rear end of the casing to engage with the engaging recess. Thereafter, the casing is extracted from the drilled hole by further retracting the tool body while hitting and rotating the tool body again. The tool body is also struck to vibrate the casing. This makes it possible to reliably and easily extract the casing from the hole without separately requiring a vibration device or the like. Further, in this case, when the casing is pulled out from the hole, the tool body is retracted while being rotated while being struck, so that the casing can be pulled out with a smaller pulling force.

[0012]

1 to 3 show an embodiment of a drilling tool according to the present invention. In the excavating tool 1 of the present embodiment, the tool main body 2 is formed in a substantially multi-stage cylindrical shape whose outer diameter increases one step toward the front end side, and the reduced rear end is attached to the hammer H. (In this embodiment, three blocks) in which a number of chips 4... Made of a hard material such as cemented carbide are implanted on the tip end surface and the outer peripheral side surface. Are attached to each other to form a cutting edge, which is hit by the hammer H toward the front end of the tool body 2 in the direction of the center axis O during excavation, and is denoted by a symbol T around the axis O in FIGS. The hole is formed by the cutting blade by being rotated in the rotation direction shown by. The inner peripheral portion of the tool main body 2 is a supply hole 6 for supplying compressed air or the like to the distal end side of the tool main body 2, and a foot valve 7 is attached to a rear end thereof.

The block 5 has a substantially sector shape when viewed from the front end side, and a mounting shaft 5A is vertically suspended from the rear end surface at a position eccentric from the center of the sector shape. A mounting groove 5B is formed in an annular shape. On the other hand, on the distal end surface of the tool main body 2, mounting holes 8 into which the mounting shaft 5A can be inserted are arranged at regular intervals in the circumferential direction on the circumference of a circle centered on the center axis O of the tool main body 2. 5, the tool body 2 is formed in parallel with the axis O.
A mounting pin hole 9 is formed so as to be in contact with the mounting hole 8 in a cross section orthogonal to the axis O from the outer periphery of the distal end of the block 5. The mounting shaft 5 </ b> A of the block 5 is fitted into the mounting hole 8. Above, by inserting the mounting pin 10 into the mounting pin hole 9 and mounting it and engaging with the mounting groove 5B,
It is attached to the tip of the tool body 2 so as to be rotatable around the center line X of the attachment shaft 5A.

When the blocks 5 are rotated clockwise around the center line X as viewed from the front end, the center of the sector is positioned on the axis O as shown in FIG. When the side surfaces contact each other, the axis O
When the outer diameter of the fan is rotated in a counterclockwise direction around the center line X when viewed from the distal end side, the center of the fan shape is set to the axis O as shown in FIG.
Is shifted to a position eccentric from the other, and the side surfaces abut each other, so that the outer diameter from the axis O is positioned in a reduced diameter, and in this reduced diameter state, the outer diameter from the axis O of the blocks 5. The outer diameter of the tip of the tool body 2 is substantially the same as or smaller than this. When the diameters of the blocks 5 are reduced, an equilateral triangular opening is defined on the axis O as shown in FIG. 3, and the tip of the supply hole 6 faces the opening. Let me do.

In the middle of the supply hole 6, three branch holes 6A extending toward the outer periphery toward the tip end are provided.
Are formed on the outer periphery of the tip end surface of the tool body 2.
When the diameter of the blocks 5 is increased, recesses 11 are formed so as to be exposed on the rotation direction T side of each block 5, and the bottom surface of the recess 11 is directed toward the rear end side toward the outer peripheral side. And each branch hole 6A is opened in these recesses 11. Further, the outer peripheral surface of the tool main body 2 is connected to the concave portion 11 and has a cross-section “
A groove 12 having a U-shape, and a groove 13 having a U-shaped cross section and extending in parallel with the axis O on the rotation direction T side of each groove 12, respectively, have an enlarged diameter of the tool body 2. It is formed so as to reach the rear end of the front end. On the outer peripheral surface of the enlarged distal end portion of the tool main body 2, a step portion 14 is formed on the rear end side, the diameter of which is increased by one step toward the outer periphery. A plurality of engaging holes 15 having a circular cross section extending in the radial direction with respect to the axis O are arranged at equal intervals in the circumferential direction so as to avoid the mounting holes 8, the mounting pin holes 9, and the concave grooves 12 and 13 (in the present embodiment, the blocks are blocks). 3 equal to 5
(1) It is formed as an engagement recess.

The casing 21 into which the excavating tool 1 is inserted has a thin cylindrical shape. The inner diameter of the casing 21 is large enough to fit the step 14 of the tool body 2. The outer diameter is made smaller than the outer diameter when the blocks 5 are enlarged, and a casing top 22 is attached to a tip end thereof. The casing top 22 is used for inserting an H-shaped steel pile, which will be described later, in the present embodiment, has an outer diameter that can be inserted into the inner periphery of the casing 21, and has a step at the tip end of the tool body 2. An outer multi-stage cylindrical shape comprising a rear end having an inner diameter that allows a portion closer to the front end than the portion 14 to be inserted, and a front end having an inner diameter equal to the rear end and an outer diameter equal to the casing 21. As shown in FIG. 4, four notches 23 extending parallel to the axis O from the rear end are formed at regular intervals in the circumferential direction as positioning portions, and these notches 23 are formed.
Is the casing top 2 at a depth equal to the thickness of this rear end.
2 and extends to the inner periphery of the tip and is opened at the tip. The casing top 22 thus formed is welded after the rear end of the casing 21 is inserted into the casing 21 from the front end side and the rear end of the front end is abutted against the front end of the casing 21. And attached to the casing 21.

The casing 21 thus formed has
The excavating tool 1 is coaxially inserted together with the hammer H from the rear end side of the casing 21 with the block 5 reduced in diameter.
The block 5 is made to protrude from the front end of the casing top 22 with the step portion 14 in contact with the rear end of the casing top 22. Then, from this state, the hammer H
By rotating the tool body 1 together with the hammer H by an auger (not shown) while hitting the tool body 1 of the excavating tool 1 by the
Are enlarged in diameter as shown in FIG. 2 to form a hole in the ground or the like, and the step portion 14 and the casing top 22 engage with the tip side in the direction of the axis O, and the casing is inserted into the hole. 2
1 is inserted. In addition, a drilled hole having a depth greater than the length of the single casing 21 is formed, and the
When the first casing 21 is inserted into the hole, the next casing 21 is inserted at the rear end.
Are added by welding or the like, and a rotary impact force is again applied to the tool main body 2 by the hammer H and the auger, and the casings 21 are inserted while forming holes.

In the present embodiment, of the casings 21 sequentially inserted in this manner, the outer periphery of the rear end of the casing 21 inserted last is provided with a cylindrical shape having a larger thickness than the casing 21 as shown in FIG. Are attached by welding or the like. From the jig for rotation 24 to the casing 21, the same number of the through holes 25 penetrating the jig for rotation 24 and the casing 21 are formed at equal intervals in the circumferential direction as the number of the engagement holes 15. Each of the holes 25 has an outer peripheral end supported by the rotating jig 24 and has an engaging pin 26.
Can be attached in the radial direction with respect to the axis O, and the inner peripheral ends of these engaging pins 26 are attached to the tool body 2.
And is projected into the inner periphery of the casing 21 so as to be an engagement projection in the present embodiment. However, at least these engaging pins 26 ...
Are removed during excavation by the excavating tool 1 so as not to interfere with the rotary impact of the tool body 2.
A mark indicating the rotational position of the notch 23... Of the foremost casing top 22 with respect to the axis O is provided at the rear end of the casing 21 to be added.

Next, a description will be given of a first embodiment of the excavation method according to the present invention in the case where the H-shaped steel pile S is further inserted into the casing 21 inserted into the drilled hole so as to face a predetermined rotation position. I do. However, the H-shaped steel pile S inserted in the present embodiment has the same height and width as the H-shaped cross section. First, a hole is formed to a predetermined depth, and a casing 2 is formed in the hole.
When the tool 1 is inserted, the block 5 at the tip of the tool body 2 remains in an expanded state, and the auger is used to rotate the tool body 2 together with the hammer H in a direction opposite to the rotation direction T during excavation. As shown in FIG. 3, the blocks 5 are reduced in diameter and are retracted toward the rear end side in the axis O direction.
Then, when the tool main body 2 is pulled up to the rear end of the rearmost casing 21, the engaging holes 15 and the casing 21 and the rotating jig 24 as shown in FIG.
Are aligned so that the through holes 25 are coaxial with each other, and the engaging pin 26 is inserted from the outer peripheral side to support the outer peripheral end thereof on the rotating jig 24 and to form the inner peripheral end thereof. Into the engagement hole 15 to engage the tool body 2 with the casing 21.

Then, the tool body 2 is again struck by the hammer H from this state, so that the casing 21 is vibrated through the engaging pins 26..., And the mark attached to the rear end of the casing 21 is formed. On the basis of the,
The auger rotates the casing 21 together with the tool body 2 via the engaging pins 26 so that the position of the notch 23 of the casing top 22 becomes a predetermined rotational position.
However, when the casing 21 is rotated to the predetermined rotational position in this way, the rotation impact of the tool body 2 by the hammer H and the auger is terminated, and the engagement pin 26
After removing the tool body 2 from the casing 21, the H-shaped steel pile S is inserted into the casing 21, and the four edges E are cut into the notches 23 of the casing top 22 as shown in FIG. By engaging, the axis O
The H-shaped steel pile S is housed in the casing 21 and is built in the drilled hole with the rotation position with respect to the predetermined position.

As described above, according to the excavating tool 1 configured as described above and the excavation method using the excavating tool 1, the casing 21 inserted into the drilled hole is rotated by using the The rotation position of the H-shaped steel pile S positioned and inserted into the casing 21 can be adjusted to a predetermined position. For example, when a large number of H-shaped steel piles S are built, as shown in FIG. It is possible to accurately match the orientation of the piles S with a certain orientation. When the casing 21 is rotated, in the excavating tool 1 and the excavation method, the casing 21 is vibrated through the engaging pins 26 by hitting the tool body 2. Reduces the frictional resistance when rotating in the borehole, and makes it possible to rotate the casing 21 reliably and easily even with a relatively small rotational force. Moreover, in the excavating tool 1 of the present embodiment, the outer diameter from the axis O is increased by the rotation of the tool body 2 at the time of excavation, so that the block 5 provided at the tip end of the tool body 2 has a larger outer diameter. The casing 21 is inserted into such a hole so that an appropriate gap can be secured between the hole and the outer periphery of the casing 21. As a result, the ground pressure acting on the casing 21 can be reduced, so that the frictional resistance can be further reduced and the casing 21 can be more reliably and easily rotated.

In the excavating tool 1 of the present embodiment, when the casing 21 is rotated in this manner, the tool body 2
A rotating jig 24 having a large thickness is attached to the outer periphery of the rear end of the casing 21 with which the outer peripheral end is supported by the rotating jig 24. The engaging projection is engaged with an engaging hole (engaging recess) 15 of the tool body 2. Therefore, even if the thickness of the casing 21 is reduced in order to secure the clearance between the inner periphery of the casing 21 and the H-shaped steel pile S and facilitate the insertion of the H-shaped steel pile S, the engagement from the tool main body 2 occurs. When vibration or rotational force due to impact is applied to the casing 21 via the pin 26, an excessive load acts on the casing 21, particularly around the through hole 25, and the casing 21 may be damaged. Can be prevented, and the direction of the H-shaped steel pile S can be adjusted more reliably by rotating the casing 21 to a predetermined rotation position.

On the other hand, in the excavation method of the present embodiment, the casing top 22 attached to the tip of the casing 21
Notches 23 are formed as positioning portions, and when the H-shaped steel pile S is inserted into the casing 21 by being rotated to a predetermined rotation position, the edge E at the tip thereof is cut off by the notch 23.
, The orientation of the H-shaped steel piles S can be more easily adjusted to a certain direction. In the present embodiment, the height and the width of the H-shape formed by the cross section of the H-shaped steel pile S are equalized, and accordingly, the four edges E are arranged at equal intervals in the circumferential direction. The notches 23 are also formed at equal intervals in the circumferential direction. However, if the cross-sectional shape of the H-shaped steel pile S to be inserted is different from this, the casing top 22 also matches the notches 23. The positions may be appropriately different.

In the excavation method according to the first embodiment, the case where the H-shaped steel pile S is further inserted and built into the casing 21 inserted into the drilled hole has been described. Can be used when the casing 21 inserted into the hole is extracted from the hole as in the second embodiment of the excavation method of the present invention described below. That is, in the excavation method according to the second embodiment, the casing 21 is inserted into the bore while forming the bore with the excavating tool 1, and then the rear end portion of the casing 21 as shown in FIG. The tool main body 2 is retracted until the engagement pins 26 are inserted into the engagement holes 15 and the tool main body 2 and the casing 21 are engaged with each other. If necessary, the tool body 2 is further retracted together with the hammer H while the tool body 2 is being rotated by the auger.
The casing 21 is pulled out of the hole through 6.

However, according to the excavation method of the second embodiment, the casing 21 is also vibrated by the hammer H from the tool body 2 via the engaging pins 26. In addition, the frictional resistance acting on the casing 21 by the tightening force due to the pressure of the ground or the like can be reduced, and the casing 21 can be reliably and easily pulled out from the drilled hole. In particular, if the casing 21 is rotated together with the tool body 2, the casing 21 can be pulled out with a smaller pulling force.
If the block 5 at the distal end can be expanded or reduced in diameter, the casing 21 can be pulled out with even less force. Therefore, according to such an excavation method, the excavating tool 1 used for forming the drilled hole and the excavating device such as the hammer H for driving the same are prepared without preparing a vibration device or the like for vibrating the casing 21 in advance. The casing 21 can be pulled out by utilizing it, and economical and efficient work can be achieved.

When the H-shaped steel pile is not positioned and inserted into the casing 21 as in the first embodiment, as in the excavation method of the second embodiment, the casing top 22 is not used. May not have the notches 23... Formed as described above. In the excavating tool 1 of the above embodiment, three engaging holes 15 are formed as engaging recesses on the outer periphery of the tip of the tool main body 2, and three engaging holes 15 are formed on the rear end of the casing 21 in accordance with the engaging recesses. Of the engagement pins 26 ...
And the inner peripheral end thereof is used as an engagement projection. The number and shape of these engagement recesses and engagement projections are determined by the tool body 2
It may be appropriately changed depending on the size of the casing 21 and the like.

[0027]

As described above, in the excavating tool according to the present invention, the engaging concave portion is formed on the outer periphery of the tool main body so as to be disengageable from the engaging convex portion projecting from the inner periphery of the rear end of the casing. Therefore, when the casing is rotated to a predetermined rotation position as in the excavation method of the present invention, or when the casing is pulled out from the drilled hole, the engagement uneven portion is hit by hitting the tool body. Vibration is applied to the casing via the casing, whereby the frictional resistance acting on the casing can be reduced, so that the casing can be reliably and easily rotated to a predetermined rotational position, and the casing is bored without the need for a vibration device or the like. It can be pulled out from the device.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a drilling tool 1 according to an embodiment of the present invention.

FIG. 2 is a front view showing a state in which blocks 5 of the excavating tool 1 shown in FIG.

3 is a front view showing a state in which blocks 5 of the excavating tool 1 shown in FIG. 1 are reduced in diameter.

4 is a casing 2 relating to the excavating tool 1 shown in FIG.
FIG. 2 is a partially cutaway perspective view of the casing 1 and a casing top 22.

FIG. 5 is a diagram showing a first embodiment of the excavation method of the present invention.

6 is a cross-sectional view showing a state in which the H-shaped steel pile S is positioned on the casing top 22 in the embodiment shown in FIG.

FIG. 7 is a view showing a state in which a large number of H-shaped steel piles S are installed with their orientations being fixed in the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Excavation tool 2 Tool main body 5 Block 14 Step part 15 Engagement hole (engagement concave part) 21 Casing 22 Casing top 23 Notch (positioning part) 24 Jig for rotation 26 Engagement pin (engagement convex part) O Tool main body 2 T axis of rotation of tool body 2 during excavation H hammer S H-shaped steel pile E Edge of H-shaped steel pile S

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Fujifun 1528 Nakashinda, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture F-term in Mitsubishi Materials Corporation Gifu Works (reference) 2D029 EB04 EC01

Claims (7)

[Claims] 1. A tool which is inserted into a cylindrical casing, is struck in the center axis direction of the casing, and is provided on the outer periphery of a tool body which is rotated about the axis at a rear end inner periphery of the casing. An excavating tool, wherein an engaging concave portion that can be engaged and disengaged is formed in the mating convex portion. 2. The engaging projection is an inner peripheral end of an engaging pin attached through the casing, and an outer peripheral end of the engaging pin is a rotating pin attached to an outer periphery of the casing. The excavating tool according to claim 1, wherein the excavating tool is supported by a jig. 3. A block provided with a cutting edge at a tip end of the tool main body so that an outer diameter from the axis can be increased with rotation of the tool main body during excavation, and a rotation direction during this excavation. The outer diameter from the axis is reduced so that the outer diameter from the axis can be reduced with rotation of the tool body in a direction opposite to the above.
Or the drilling tool according to claim 2. 4. An excavation method using the excavation tool according to claim 1, wherein the drill body is hit in the axial direction and rotated around the axis to form a hole. While forming, insert the casing into the drilled hole, then, with the casing inserted into the drilled hole, retract the tool body to the rear end of the casing. And excavating the casing to a predetermined rotational position by hitting and rotating the tool body again after engaging the engaging recess. 5. After rotating the casing to a predetermined rotation position, the engaging projection is pulled out of the engaging recess, the tool body is pulled out of the casing, and an H-shaped steel pile is inserted into the casing. 5. The excavation method according to claim 4, wherein the H-shaped pile is rotated around the axis by engaging an edge of the H-shaped steel pile with an inner periphery of a tip end of the casing. An excavation method characterized by providing a positioning portion for positioning a work. 6. An excavation method using the excavation tool according to claim 1, wherein the drill body is hit in the axial direction and rotated around the axis to form a hole. While forming, insert the casing into the hole, then retract the tool body to the rear end of the casing while inserting the casing into the hole, and place the engaging projection on the inner periphery of the rear end of the casing. An excavation method wherein the casing is extracted from the hole by projecting and engaging with the engaging recess, and further retreating while again hitting the tool body. 7. The excavation method according to claim 6, wherein the casing is extracted from the hole by further retreating while hitting and rotating the tool main body.