JP2001207784A - Underground obstruction removal method and tunnel boring machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a structure, reduce cost and improve workability concerning an underground obstruction removal method and a tunnel boring machine. SOLUTION: Five pieces of fixed spokes 15a-15e and a piece of a rotating spoke 16 are radially installed on a cutter head 12, a large number of cutter bits 20 are installed on the fixed spokes 15a-15e, a rotor 33 free to rotate at high speed by a hydraulic motor 37 is provided on the rotating spoke 16, and a cutter bit 44 and pile cutting bits 45, 46 are installed on an outer peripheral part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground obstacle removing method for crushing and removing an obstacle that is difficult to excavate with a cutter bit for excavation in the ground in front of the ground. And a tunnel excavator having an underground obstacle removing function.

[0002]

2. Description of the Related Art In a general shield excavator, a cutter head having a large number of cutter bits is rotatably mounted at a front portion of an excavator body and can be driven to rotate by a drive motor. A plurality of shield jacks are arranged side by side in the circumferential direction at the rear portion of the excavator body, and an erector device is mounted. Therefore, while rotating the cutter head by the drive motor, the shield jack is extended and the excavator body is advanced by the reaction force against the existing segment, so that each cutter bit of the cutter head excavates the ground in front, With the excavation of the ground, the elector device assembles the segments on the inner peripheral surface of the existing tunnel, thereby constructing the tunnel.

By the way, if an unexpected obstacle, for example, a sheet pile or a reinforced concrete pile, is found in the ground in front of a tunnel during excavation, it cannot be crushed by a cutter bit of a shield excavator. The cutter bit will be damaged. Therefore, it is necessary to detect this obstacle during excavation and remove it. When removing an obstacle buried underground such as this, an underground radar is used to search for obstacles existing in the ground in advance, and the ground above the tunnel is cut open to remove this obstacle. Or using a vibratory pile driver to remove obstacles. However, it takes a long time to remove such obstacles, and during this time, tunnel excavation work cannot be performed.
Work efficiency will be reduced.

Therefore, it has been considered to provide a cutter device for removing an obstacle in a tunnel excavator. A cutter head or a separate cutter device in the excavator body is accommodated, and when an obstacle is detected, the cutter device is accommodated. Generally, a cutter device is projected forward to cut and remove an obstacle. For example,
JP-A-10-25990 and JP-A-11-5078
No. 8, for example.

[0005]

However, in such a conventional tunnel excavator having a cutter device for removing an obstacle, the device is large in size because the cutter device is housed in the cutter head or the excavator body. It will be. In addition, the structure for accommodating the cutter device and for protruding the cutter device is complicated, and the manufacturing cost is increased.

SUMMARY OF THE INVENTION The present invention solves such a problem, and provides a method of removing an underground obstacle and a tunnel excavator, which can simplify the structure and reduce the cost and improve the workability. The purpose is to:

[0007]

According to a first aspect of the present invention, there is provided a method of removing an underground obstacle, wherein an axis of a cutter head is rotated or oscillated in a radial direction of the cutter head. By moving the cutter head forward in a state in which a rotating body provided along the axis is rotated around the axis,
An obstacle buried underground is crushed by an obstacle crushing bit attached to an outer peripheral portion of the rotating body.

Further, in the underground obstacle removing method according to the second aspect of the present invention, the rotating direction of the cutter head and the rotating direction of the rotating body are the same on the front side of the cutter head. .

According to a third aspect of the present invention, there is provided a tunnel excavator having a tubular excavator body, a propulsion jack for advancing the excavator body, and a cutter rotatably mounted on a front portion of the excavator body. A head, cutter head driving means for driving and rotating the cutter head, a number of cutter bits attached to the front surface of the cutter head and capable of excavating the ground,
A rotating body rotatably supported by the cutter head by an axial center along a radial direction, rotating body driving means for driving and rotating the rotating body, and an obstacle in the ground attached to an outer peripheral portion of the rotating body. And an obstacle crushing bit capable of crushing the object.

Further, in the tunnel excavator according to the invention of claim 4, the rotating body has a base end rotatably supported by a bearing on a center ring of the cutter head, while a tip end has an outer peripheral ring of the cutter head. And is rotatably supported by a bearing.

In a tunnel excavator according to a fifth aspect of the present invention, a large number of cutter bits capable of excavating the ground are attached to the outer peripheral portion of the rotating body along a longitudinal direction, and the cutter bit row is normally provided during excavation. A lock device for locking the rotating body at a position facing forward in the digging direction is provided.

In a tunnel excavator according to a sixth aspect of the present invention, an obstacle crushing bit is provided at an outer peripheral end of the rotating body so as to protrude outward.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a tunnel excavator having an underground obstacle removing function according to an embodiment of the present invention, FIG. 2 is a front view of the tunnel excavator of the present embodiment, and FIG.
FIG. 4 is a sectional view taken along line III-III, FIG. 4 is a sectional view of a rotary spoke, FIG. 5 is a sectional view taken along line VV in FIG. 4, FIG. 6 is a description of an obstacle detection method, and FIG.

In the tunnel excavator of the present embodiment, as shown in FIGS. 1 and 2, a cutter head 12 is rotatably mounted at the front of an excavator body 11, and can be driven to rotate by a drive motor 13. It has become. Then, five fixed spokes 15a to 15e and one rotating spoke 16 are radially mounted from a center ring 14 located at a central portion of the cutter head 12, and an outer peripheral portion is an outer peripheral ring 17.
Are linked by

Each of the fixed spokes 15a to 15e has substantially the same configuration. As shown in FIGS. 2 and 3, a mounting base 19 is fixed to an upper portion of a box-shaped spoke body 18, and both sides of the mounting base 19 (see FIGS. A cutter bit 20 is rotatably mounted on a mounting pin 21 at the front and rear of the cutter head 12 in the rotation direction. This cutter bit 20 is a fixed spoke 1
Although a large number are mounted on both sides of the cutter head 12 along the radial direction of the cutter head 12, the mounting positions in the radial direction are slightly shifted for each of the fixed spokes 15a to 15e. Can be drilled.

A widened portion 22 is formed on the front surface of the fixed spoke 15b.
Is installed. Although not shown, the underground radar 23 has a transmission antenna for transmitting electromagnetic waves and a reception antenna for receiving reflected electromagnetic waves, and can detect the position of the obstacle H based on the reception level of the reception antenna. it can.

Further, on the front surface of the fixed spoke 15d,
A first detecting member 24 which can be moved in and out in the excavation direction is mounted at a radially outermost position of the cutter head 12, and a second detecting member 25 which can be moved in and out in the excavating direction is mounted at an innermost position. The first detection member 24 and the second detection member 25 have substantially the same configuration, and the detection member main body 26 having a cylindrical shape and a spherical end portion is attached to the mounting base 1 of the spoke main body 18.
9 is movably supported by a seal member 27 and a metal bearing 28, and is movable by a hydraulic jack 29 mounted in the spoke body 18. When a normal excavator is used, the hydraulic jack 29 is contracted so that the tip of the detection member main body 26 is located behind the cutter bit 20 in the excavation direction. When an obstacle H is detected, the hydraulic jack 29 is extended and detected. The tip of the member body 26 is
It is arranged to be located ahead of 0 in the excavation direction. In addition, grease is injected into a mounting portion of the sealing material 27 to enhance waterproofness.

On the other hand, in the rotary spoke 16, the seal member 3 is attached to the center ring 14 by a rotary joint 30.
A base end of the rotary cylinder 33 is rotatably supported via the first and metal bearings 32, and a distal end of the rotary cylinder 33 is supported by a support ring 34 of the outer peripheral ring 17 via a seal material 35 and a metal bearing 36. It is rotatably supported. The drive shaft 38 of the hydraulic motor 37 mounted on the center ring 14 is fixed to the base end of the rotary cylinder 33. A slide cylinder 40 is movably supported by a support cylinder 39 fixed to the distal end side in the rotary cylinder 33 via a seal material 41 and a metal bearing 42. A hydraulic jack 43 is provided between them.

A cutter bit 44 is fixed to both sides of the outer peripheral portion of the rotary cylinder 33 (front and rear in the rotation direction of the cutter head 12), and a pile cutting bit 45 is spirally fixed along the longitudinal direction. A pile cutting bit 46 is attached to the tip of the slide cylinder 40 so as to be able to protrude and retract by a hydraulic jack (not shown). In addition, each pile cutting bit 45,
46 is set longer than the cutter bits 20 and 44. A lock device 47 is mounted on the center ring 14, and a movable lock pin 48 is fitted into a lock hole 49 of the rotary cylinder 33 so that the left and right cutter bits 44 are fitted.
The rotary cylinder 33 can be locked at a position where is located forward in the digging direction. In FIG. 4, the locking device 47 is described as being located on the side of the center ring 14 so that the structure can be understood in detail. It is what is being done.

Therefore, when the excavator is normally used, the locking device 4
7, the rotary cylinder 33 is locked at a position where the cutter bit 44 is located in the forward direction in the excavation direction. By moving the cutter head 12 forward while rotating, the cutter bit 44 can excavate the ground in front. On the other hand, when cutting the obstacle H, the lock unit 47 unlocks the rotary cylinder 33 and drives the hydraulic motor 37 to rotate the rotary cylinder 33 at a high speed to move forward. The obstacle H buried therein can be cut.
At this time, the hydraulic jack 43 is extended and the slide cylinder 40 is extended.
Of the excavator main body 11 located behind the cutter head 12 by cutting the obstacle H outside the outer peripheral ring 17 by moving the
Can be facilitated.

Also, as shown in FIG.
Is mounted with a rotary encoder 50, which can detect the rotation angle of the cutter head 12. Furthermore,
A plurality of shield jacks 51 are arranged in the rear part of the excavator body 11 in the circumferential direction.
1 includes a stroke sensor 52 for detecting an operation stroke.
Is installed.

In this embodiment, the control device 53
The detection result of the underground radar 23, the fluctuation of the hydraulic pressure of the hydraulic jack 29 of the first detection member 24 and the second detection member 25, the fluctuation of the current of the drive motor, the detection result of the rotary encoder 50, the detection result of the stroke sensor 52 Is entered. As a result, the control device 53 can detect a collision between the first and second detection members 24 and 25 and the obstacle H from the fluctuation of the hydraulic pressure of each hydraulic jack 29 and the fluctuation of the current of the driving motor (collision detecting means). The position of the obstacle H can be obtained based on the detection results of the rotary encoder 50 and the stroke sensor 52 (obstacle position detecting means).

Here, a method of removing an underground obstacle by the tunnel excavator according to the present embodiment will be specifically described with reference to a flowchart of FIG. In the tunnel excavator, while the cutter head 12 is rotated by the drive motor 13, the shield jack 51 is extended and the excavator main body 11 is advanced by the reaction force against the existing segment, and the cutter bit 20,
The ground in front is excavated by 44. At this time, by operating the underground radar 23, it is detected whether there is an obstacle H or the like in the ground in front. That is, as shown in FIG. 7, in step S1, the underground radar 23 moves the obstacle H
After detecting the like, in step S2, the hydraulic jack 29
To make the first detection member 24 and the second detection member 25 protrude forward.

First, in step S3, it is determined whether the hydraulic jack 29 of the first detecting member 24 has a pressure fluctuation. In this case, as shown in FIGS. 1 and 2, if there is an obstacle H longer than the diameter of the cutter head 12,
It collides with the first detection member 24 before the detection member 25.
Then, if there is a pressure fluctuation in the hydraulic jack 29 of the first detecting member 24, in step S4, the load fluctuation of the rotational torque of the cutter head 12 at this time (the driving motor 13
Is determined to be greater than or equal to a predetermined value. That is, if the obstacle H colliding with the first detection member 24 is a mere gravel, it can be crushed by the cutter bits 20 and 44, and the load fluctuation is smaller than a predetermined value. On the other hand, if the obstacle H cannot be crushed by the cutter bits 20 and 44, such as a sheet pile or a reinforced concrete pile, the load fluctuation of the cutter head 12 becomes a predetermined value or more and it is determined that the obstacle H has occurred. The first detecting member 24 is immersed in the spoke 15d by contracting 29.

Then, in step S6, the control device 53
Is the rotation angle of the cutter head 12 by the rotary encoder 50, that is, the angle θ ₁ from the reference position to the collision position between the first detection member 24 and the obstacle H as shown in FIG.
With read, at step S7, read the propulsion stroke S ₁ of the tunneling machine by the stroke sensor 52, on the three-dimensional coordinates based on the rotational angle theta ₁ of the cutter head 12 and the propulsion stroke S ₁ first The collision position between the detection member 24 and the obstacle H is calculated.

Next, in step S8, similarly to step S3, it is determined whether or not the hydraulic jack 29 of the second detecting member 25 has a pressure fluctuation. In S9, it is determined whether or not the load fluctuation (current value fluctuation of the drive motor 13) of the rotational torque of the cutter head 12 at this time is equal to or more than a predetermined value. Obstacles H that cannot be crushed by the cutter bits 20 and 44
Is determined, and in step S10, the hydraulic jack 29 is contracted so that the second detection member 25 is immersed in the spoke 15d.

Then, in step S11, the control device 5
3 is the rotary encoder 50 for the cutter head 12
The rotation angle, that is, as shown in FIG.
Angle θ to collision position between second detection member 25 and obstacle H
_TwoIs read, and in step S12, the stroke
The propulsion stroke S of the tunnel excavator by the sensor 52 _Two
And the rotation angle θ of the cutter head 12_TwoAnd push
Advance stroke S_TwoThe second inspection on the three-dimensional coordinates based on
The collision position between the knowledge member 25 and the obstacle H is calculated. Soshi
In step S13, the control device 53 determines that the obstacle H
Three-dimensional seat of the collision position with the first and second detection members 24 and 25
It is determined that there is an obstacle H on the straight line connecting the targets, and step S
At 14, the cutter head 1 according to the position of the obstacle H
2 is driven to crush the obstacle H.

That is, as shown in FIGS. 2 and 4, while the cutter head 12 is being rotated at a low speed, the lock device 47 pulls out the lock pin 48 from the lock hole 49 and rotates the rotary cylinder 3.
3 and the hydraulic jack 43 is extended to move the slide cylinder 40, and the pile cutting bit 46
To drive the hydraulic motor 37 to rotate the rotary cylinder 33 at high speed. When the excavator body 11 is advanced by extending the shield jack 51 in this state, a large number of pile cutting bits 4
Obstacle H in a state where 5, 46 are moving at high speed and rotating
, The obstacle H can be cut and crushed. In this case, by setting the rotation direction of the cutter head 12 and the rotation direction of the rotary cylinder 33 to be the same, the obstacle H
The contact speed of the pile cutting bits 45, 46 to the pile cutting bit is doubled. Further, since the pile cutting bits 45 and 46 are longer than the cutter bits 20 and 44 in the excavation direction, the cutter bits 20 and 44 do not come into contact with the obstacle H and are not damaged. Furthermore, since the pile cutting bit 46 cuts the obstacle H outside the outer peripheral ring 17, the excavator body 11 located behind the cutter head 12 can be easily propelled.

Although not described in the flowchart of FIG. 7, there is no pressure change in the hydraulic jack 29 of the first detecting member 24 in step S3.
When the pressure fluctuation occurs in the hydraulic jack 29 of No. 5,
The obstacle is judged to be gravel because it is not long. In addition, by setting the standby time in steps S8 and S9, even if the predetermined time has elapsed, the hydraulic jack 29 of the second detection member 25 does not change in pressure even if the predetermined time has elapsed, or the cutter head does not change in step S9. If there is no load fluctuation of the rotation torque of No. 12, the obstacle that collided with the first detection member 25 is not long and is determined to be gravel.

As described above, in the tunnel excavator of the present embodiment, five fixed spokes 15
a to 15e and one rotary spoke 16 are radially mounted, and a number of cutter bits 20 are mounted on the fixed spokes 15a to 15e.
7, a rotating body 33 capable of high-speed rotation is provided, and a cutter bit 44 and pile cutting bits 45 and 46 are attached to the outer peripheral portion. Therefore, if an obstacle H is detected in the ground in front, the rotating body 33 is advanced while rotating the rotating body 33 at a high speed while the cutter head 12 is rotating at a low speed, so that the pile cutting bit 45 of the rotating body that rotates at a high speed. , 46 allows the obstacle H to be reliably cut and crushed.

In the above embodiment, the cutter head 12 is provided with five fixed spokes 15a to 15e and one rotating spoke 16 in a radial manner. However, the number of fixed spokes is not limited to five. No more than 4 or 6
More than two or two or more rotary spokes 16 may be provided in consideration of the space for disposing the hydraulic motor 37 in the rotary spokes 16. Further, the underground radar 23 is provided on the fixed spoke 15b, but may be provided on the excavator body 11. Furthermore, although the first and second detection members 24 and 25 are provided on the fixed spoke 15d, other fixed spokes may be provided. Alternatively, the first detection member 24 is provided on the fixed spoke 15a, and the second detection member is provided on the fixed spoke 15b. May be provided on the rotating spokes 16. The number of detection members may be three or more. In this case, it is desirable that the third detection member is provided at a middle portion in the longitudinal direction of the spoke.

In the above-described embodiment, the fluctuation of the hydraulic pressure of the hydraulic jack 29 of the first detecting member 24 and the second detecting member 25 and the fluctuation of the load of the driving motor 13 of the cutter head 12 (the fluctuation of the current value of the driving motor 13) are considered. Based on the determination, it was determined whether the obstacle H was mere gravel or an obstacle H that could not be crushed by the cutter bits 20 and 44, such as a sheet pile or a reinforced concrete pile. Only the hydraulic pressure fluctuation, or only the load fluctuation of the drive motor 13 may be used, and other conditions may be used.

Furthermore, by rotating the rotary cylinder 33 at a high speed while rotating the cutter head 12 at a low speed, the obstacle H is cut by a large number of pile cutting bits 45 and 46.
By rotating the cutter head 12 within a predetermined angle range while the rotating cylinder 33 is rotating at a high speed, that is, reciprocatingly rotating, the rotating cylinder 33 is moved by the range where the obstacle H exists, and the pile cutting bits 45 and 46 are moved. When the obstacle H is at a position passing through the center of the cutter head 12, the rotary cylinder 33 stops the cutter head 12 at a position overlapping the obstacle H when the obstacle H passes through the center of the cutter head 12. The obstacle H may be cut by rotating only the rotating cylinder 33 at high speed. In this case, it is necessary to rotate the cutter head 12 every time a predetermined cutting time of the obstacle H elapses and to excavate the ground in front by the cutter bits 20 and 44.

[0035]

As described above in detail in the embodiment, according to the method for removing underground obstacles according to the first aspect of the present invention,
By rotating or swinging the cutter head and moving the rotating body provided along the radial direction forward while rotating about the axis, the ground is broken by the obstacle crushing bit attached to the outer periphery of the rotating body. Since the obstacles buried therein are crushed, there is no need to provide a separate cutter device, so that the structure can be simplified, the cost can be reduced, and the workability can be improved.

According to the method of removing underground obstacles according to the second aspect of the present invention, the rotation direction of the cutter head and the rotation direction of the rotating body are the same on the front side of the cutter head. Can improve the efficiency of cutting obstacles.

According to the tunnel excavator of the third aspect of the present invention, the excavator body can be advanced by the propulsion jack, and the cutter head mounted on the front part of the excavator body is controlled by the cutter head driving means. It can be driven and rotated,
While a large number of cutter bits capable of excavating the ground are mounted on the front surface of the cutter head, the rotating body is rotatably supported on the cutter head by an axial center extending in a radial direction, and is rotatable by rotating body driving means. Since an obstacle crushing bit that can crush obstacles underground was attached to the outer periphery of the rotating body,
It is sufficient to rotate the rotating body to remove obstacles, and it is not necessary to house the obstacle crushing bit in the cutter head or the excavator body, so that the structure can be simplified and the cost can be reduced and workability can be improved. Can be improved.

According to the tunnel excavator of the present invention, the base end of the rotating body is rotatably supported by the center ring of the cutter head by a bearing, while the tip end is supported by the outer ring of the cutter head. As a result, the rotating body is firmly supported and the rotation is smoothly supported, and an obstacle can be reliably cut.

According to the tunnel excavator of the invention of claim 5, a large number of cutter bits capable of excavating the ground are attached to the outer peripheral portion of the rotating body along the longitudinal direction, and at the time of normal excavation, the cutter bit row is moved in the excavating direction. A lock device that locks the rotating body at the position facing forward is provided, so that the ground can be reliably excavated with the cutter bit by locking the rotating body with the locking device during normal excavation, while the locking device is used when cutting obstacles By unlocking the rotating body, the obstacle crushing bit can cut and crush the obstacle, so that a space for accommodating the obstacle crushing bit becomes unnecessary, and the device can be reduced in size and weight.

According to the tunnel excavator according to the sixth aspect of the present invention, an obstacle crushing bit protruding to the outer peripheral side is provided at the outer peripheral end of the rotating body. Cuts an obstacle outside the cutter head, so that the obstacle does not hinder the propulsion of the excavator body, and the excavating operation can be easily performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a tunnel excavator having an underground obstacle removal function according to an embodiment of the present invention.

FIG. 2 is a front view of the tunnel excavator according to the embodiment.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a sectional view of a rotating spoke.

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 is an explanatory diagram of an obstacle detection method.

FIG. 7 is a flowchart of an obstacle detection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Excavator main body 12 Cutter head 13 Drive motor (Cutter head drive means) 14 Center ring 15a, 15b, 15c, 15d Fixed spoke 16 Rotating spoke 17 Outer ring 20 Cutter bit 23 Underground radar 24 First detection member 25 Second detection Member 29 Hydraulic jack (fluid pressure jack) 33 Rotating cylinder (rotating body) 32, 36, 42 Metal bearing 37 Hydraulic motor (rotating body driving means) 40 Slide cylinder 43 Hydraulic jack 44 Cutter bit 45, 16 Pile cutting bit (obstacle) Crushing bit) 51 shield jack (propulsion jack) 53 control device H obstacle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisao Arai 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Kazuo Miyazawa 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation Co., Ltd. (72) Inventor Minoru Suzuki 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Hiroshi Kazama 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation F Terms (reference) 2D054 BA25 BB04 GA17 GA65 GA84 GA92

Claims (6)

[Claims] 1. A cutter head is moved forward with a rotating body provided along a radial direction of the cutter head being rotated about the axis while rotating or swinging the cutter head. Thus, an underground obstacle removing method is characterized in that an obstacle buried in the ground is crushed by an obstacle crushing bit attached to an outer peripheral portion of the rotating body. 2. The underground obstacle removing method according to claim 1, wherein the rotation direction of the cutter head and the rotation direction of the rotating body are the same on the front side of the cutter head. Medium obstacle removal method. 3. A cylindrical excavator main body, a propulsion jack for advancing the excavator main body, a cutter head rotatably mounted on a front portion of the excavator main body, and a cutter for driving and rotating the cutter head. A head driving means, a number of cutter bits attached to the front surface of the cutter head and capable of excavating the ground, a rotating body rotatably supported by the cutter head by an axial center along a radial direction, A tunnel excavator comprising: a rotating body driving means for driving and rotating a body; and an obstacle crushing bit attached to an outer peripheral portion of the rotating body and capable of crushing an underground obstacle. 4. The tunnel excavator according to claim 3, wherein the rotating body has a base end rotatably supported by a bearing on a center ring of the cutter head and a tip end mounted on an outer peripheral ring of the cutter head. A tunnel excavator, which is rotatably supported by a bearing. 5. The tunnel excavator according to claim 3, wherein a plurality of cutter bits capable of excavating the ground are mounted along the longitudinal direction on an outer peripheral portion of the rotating body, and the row of cutter bits is excavated during normal excavation. A tunnel excavator provided with a lock device for locking the rotating body at a position facing forward in a direction. 6. The tunnel excavator according to claim 3, wherein an obstacle crushing bit is provided at an outer peripheral end of the rotating body so as to protrude outward.