JP2001020677A - Tunnel boring machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and lighten a device while improving the reliability of excavation works in a tunnel boring machine. SOLUTION: In the TBM 10, a cutter head 13 is installed in front of a drum 11 in a manner that the cutter head can be driven and rotated while a parallel link mechanism 23 is built between the cutter head 13 and a press ring 19 disposed at a rear, and the front end section of a supporting frame 25 is fixed onto the press ring 19 and a movable type reaction receiver 26 is mounted longitudinally movably while a gripper supporting base 35 is connected at the rear section of the drum 11 and an angle is adjusted freely by a posture adjusting jack.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunnel excavator such as a tunnel boring machine or a shield excavator for excavating the ground to construct a tunnel.

[0002]

2. Description of the Related Art A conventional tunnel boring machine has a body composed of a cylindrical front body and a rear body.
A cutter head having a roller cutter is rotatably mounted on a front portion of the front body, and can be driven and rotated by a cutter turning motor. A chamber is formed in the front body by forming a bulkhead so as to prevent excavated waste from entering the interior, and a chamber is formed in the chamber. Is located.

A plurality of thrust jacks are provided between the front body and the rear body. The thrust jacks are expanded and contracted by supplying and discharging hydraulic pressure to the thrust jacks, so that a relative position between the front body and the rear body is provided. Can be changed. Further, a front gripper is mounted on the front body, and the front body can be held in position by extending the gripper shoe in the radial direction by a hydraulic jack. On the other hand, a rear gripper is mounted on the rear trunk, and the rear trunk can be held in position by radially extending the gripper shoe with a hydraulic jack.

Further, an erector device for attaching a support to the inner wall surface of the existing tunnel is mounted at the rear of the rear trunk.

Therefore, when the cutter head is rotated by driving the cutter rotating motor while the rear gripper is held immovable by the rear gripper, each thrust jack is extended to move the cutter head forward with the front body. Then, the roller cutter of the revolving cutter head shears and breaks the rock in front, and excavates the rock. When each thrust jack is extended by a predetermined stroke, the front body is held in position by the front gripper, while the rear body is held out of position by the rear gripper, and then the thrust jack is contracted to draw the rear body toward the front body. Then, again, the rear body is held in position by the rear gripper,
After releasing the position of the front body by the front gripper,
Each thrust jack is extended, the cutter head is moved forward together with the front body, and the rock is excavated by the roller cutter. The tunnel is continuously excavated by repeating this operation.

[0006] Then, the shear generated by the rock excavation is taken into the chamber and discharged to the outside by the belt conveyor. Also, in the process of excavating rock and excavating and forming a tunnel, if the wall surface of the excavated tunnel is stable, no support is required. Using a H-shaped steel or a wooden plate formed in a ring shape as a support, the tunnel is protected so that the rock fragments do not peel off from the wall surface.

[0007]

In the conventional tunnel boring machine described above, the thrust jack is extended while holding the rear body in position by pressing the gripper shoe of the rear gripper against the inner wall surface of the existing tunnel, The cutter head, which is driven to rotate together with the front trunk, is advanced to excavate the rock ahead. That is, the excavation reaction force generated by rock excavation of the cutter head is received by the pressing force of the rear gripper against the inner wall surface of the existing tunnel, and a large pressing force by the rear gripper is necessary for the cutter head to obtain sufficient excavation force. The gripper shoe of the rear gripper has a large pressure contact area.

However, in consideration of maintenance, transportation, assembly, and disassembly of the machine, the size of the machine itself is limited, and the gripper shoe cannot secure a large pressing area, and the pressing force increases accordingly. I have to deal with it by letting it do. However, if the pressing force of the gripper shoe against the inner wall surface of the existing tunnel is increased, the surrounding ground may induce collapse when excavating the soft collapsible ground, or the gripper shoe may cut into the soft ground, resulting in insufficient stroke,
In some cases, sufficient position holding cannot be obtained.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a tunnel excavator in which the size and weight of the device are reduced and the reliability of the excavation operation is improved.

[0010]

According to a first aspect of the present invention, there is provided a tunnel excavator having a tubular body, a cutter head rotatably mounted on a front portion of the body, and A cutter head driving means for driving and rotating the cutter head; a propulsion support portion disposed behind the fuselage; a fuselage propulsion jack provided between the fuselage and the propulsion support portion; A support frame fixed to the propulsion support portion and having a rear portion extending rearward in the excavation direction, supported movably back and forth along the support frame, and pressed against the inner wall surface of the existing tunnel to press the propulsion support portion. Movable reaction force receiving means for receiving the excavation reaction force by holding the position is provided.

Further, in the tunnel excavator according to the present invention, the movable reaction force receiving means includes a plurality of grippers capable of being pressed against the inner wall surface of the existing tunnel, and a movable jack for connecting the plurality of grippers to each other. It is characterized by having.

According to the third aspect of the present invention, a gripper support for supporting the plurality of grippers is connected to a rear portion of the body, and the angle of the gripper support can be freely adjusted by a posture adjusting jack. It is characterized by:

According to a fourth aspect of the present invention, in the tunnel excavator, the propulsion support portion has a butterfly shape in which an upper portion and a lower portion are cut, and the fuselage propulsion jacks are disposed on the left and right. .

According to a fifth aspect of the present invention, in the tunnel excavator, the support frame has a cylindrical shape, and a conveyor for discharging earth and sand excavated by the cutter head to the outside is provided inside the support frame. Features.

In a tunnel excavator according to a sixth aspect of the present invention, a conveyor for discharging the earth and sand excavated by the cutter head to the outside is disposed above the propulsion support section and the movable reaction force receiving means. It is characterized by:

Further, in the tunnel excavator according to the invention of claim 7, the movable reaction force receiving means can move two gripper shoes by one gripper jack and press against the inner wall surface of the existing tunnel. It is characterized by.

[0017]

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

FIG. 1 is a schematic side view of a tunnel boring machine as a tunnel excavator according to a first embodiment of the present invention, FIG. 2 is a II-II section of FIG. 1, FIG. 3 is a III-III section of FIG. FIG. 4 shows a cross section taken along line IV-IV of FIG.

In a tunnel boring machine (hereinafter referred to as TBM) 10 of the present embodiment, as shown in FIG. 1, a cutter head 13 is rotatably mounted on a front part of a cylindrical body 11 by a bearing 12. Have been.
A large number of roller cutters 14 for shearing and breaking rock are pivotally mounted on the front of the cutter head 13, and an opening 15 for taking in shear such as crushed rock fragments and earth and sand is formed. A ring gear 16 having internal teeth is integrally fixed to a rear portion of the cutter head 13, while an electric or hydraulic cutter turning motor 17 is fixed to the body 11. The drive gear 18 meshes with the ring gear 16.

Accordingly, when the cutter rotating motor 17 is driven to rotate the drive gear 18, the ring gear 16 meshing with the drive gear 18 rotates, and the cutter head 13 integrated with the ring gear 16 is rotated. Can be excavated by shearing, and the generated shear can be taken into the inside of the body 11 through the opening 15.

As shown in FIGS. 1 to 3, the body 1
1 is provided with a press ring 19 as a propulsion support portion, and a plurality of (here, eight) fuselage jacks are provided between the fuselage 11 and the press ring 19.
The thrust jack 20 is installed. in this case,
The press ring 19 has a butterfly shape in which an upper part and a lower part are cut out, and each thrust jack 20 is provided with the press ring 1.
9 are connected to both left and right sides. The thrust jack 20 expands and contracts by supplying and discharging hydraulic pressure.
One end of the thrust jack 20 is rotatably supported on the body 11 by a bearing 21, and the other end is a press ring 19.
The bearing 22 is swingably supported by a bearing 22. The slide jacks 20 are disposed adjacent to each other, for example, one of the adjacent slide jacks 20 is inclined in one circumferential direction of the cutter head 13 and the other thrust jack is inclined in the other circumferential direction. The parallel link mechanism 23 is configured by being arranged in a truss shape as a whole.

Therefore, in the parallel link mechanism 23, the relative position between the body 11 and the press ring 19 can be changed by expanding and contracting the drive rod of each thrust jack 20. In the parallel link mechanism 23, by changing each operation stroke of each thrust jack 20, the body 11 having the cutter head 13 can be bent with respect to the press ring 19, and the excavation direction can be changed.

The body 11 has a front gripper 24.
Are stored in the body 11 by jacks (not shown) during excavation, so that the body 11 can be moved freely and the cutter head 13 can be pressed against the front rock. On the other hand, at the time of the changing work, the body 11 can be fixed to the bedrock by projecting all the front grippers 24 with the jacks.

On the other hand, as shown in FIGS. 1, 3, and 4, a front end of a support frame 25 is fixed to a substantially central portion of the press ring 19. The support frame 25 has a quadrangular cylindrical shape, is located substantially at the center of the existing tunnel, and extends rearward from the press ring 19 in the excavation direction.

A movable reaction force receiving device 26 that can move independently of the body 11 is provided along the support frame 25 behind the press ring 19. The movable reaction force receiving device 26 has four sets of rear grippers 26a, 26b, 26c, 2 having substantially the same configuration.
6d. A movable jack 27 is provided between the press ring 19 and each of the rear grippers 26a, 26b, 26c, 26d. 26b, 26c, 26d
Can approach and separate, and each rear gripper 2
6a, 26b, 26c, 26d can approach and move away from each other.

That is, each of the rear grippers 26a, 26b, 2
6c and 26d, frame-like gripper boxes 28a, 28b, 28c and 28d are located outside the support frame 25, respectively.
Gripper jacks 29a, 29b, 29c, 29d are respectively disposed on the upper and lower parts of c and 28d.
d are connected to each other. Therefore, by extending each gripper jack 29a, 29b, 29c, 29d, each gripper shoe 30a, 30b, 30c, 30d.
Moves right and left, and the gripper shoes 30a, 30b,
30c and 30d can be pressed against the inner wall surface of the existing tunnel.

A pair of left and right anti-rotation grooves 31 are formed on the rear surface of the press ring 19, and inserted into the anti-rotation grooves 31 on the front surface of each gripper shoe 30a of the leading rear gripper 26a. Is formed with a rotation stopping projection 32 for preventing relative rotation. The detent groove 31 is formed slightly larger than the detent projection 32, and can be easily inserted when the rear gripper 26a approaches the press ring 19. A press jack 33 is mounted on the press ring 19 so as to be positioned above each of the rotation-stop grooves 31. At the tip of the drive rod of the press jack 33, a rotation fit loosely into the rotation-stop groove 31. A pressing member 34 for pressing the stopper projection 32 is attached. Therefore, during the excavation work, the rear gripper 2 is inserted into each rotation stopping groove 31 of the press ring 19.
6a, the rotation stopper projection 32 is loosely fitted, and the press jack 33 is extended to press the rotation stopper projection 32 by the pressing member 34, so that the rear gripper 26a is integrated with the press ring 19, and the cutter head is formed. Press ring 1 by rotating torque acting on body 11 from 13
9 rotation can be received.

Further, the front end of a gripper support base 35 for supporting the rear grippers 26a, 26b, 26c, 26d from below is connected to the lower rear end of the body 11 by connecting pins 36 so as to be rotatable up and down. The gripper support 35 is for mounting and holding rear grippers 26a, 26b, 26c, 26d which are not held on the inner wall surface of the existing tunnel, and is provided with a posture adjusting jack 37 provided between the gripper support body 35 and the body 11. The angle is adjustable.

Further, a hopper 39 for accumulating shears obtained by crushing the roller cutter 14 is fixed to a chamber 38 formed by the cutter head 13 and the body 11. And
The belt conveyor 40 that carries out the excavated waste is disposed in the support frame 25, and the belt conveyor 4
0 is connected to the lower part of the hopper 39, and the rear end extends rearward of the tunnel.

Although not shown, the TBM 10 according to the present embodiment includes a loading device for a support to be assembled on the inner wall surface of the existing tunnel, an elector device for temporarily assembling the loaded support, and a temporarily assembled support for the inner wall surface of the existing tunnel. The support expansion device which presses against is mounted.

Here, an excavating operation using the TBM 10 of the present embodiment will be described.

When excavating the ground with the TBM 10,
As shown in FIG. 1, the gripper jacks 29a, 29b, 29c, 29d are extended by the rear grippers 26a, 26b, 26c, 26d of the movable reaction force receiving device 26, and the respective gripper shoes 30a, 30b, 30c, 30d are moved. The position is maintained by pressing against the inner wall surface of the existing tunnel. In this state,
Each thrust jack 20 of the parallel link mechanism 23 is extended while the cutter head 13 is driven to rotate by the cutter turning motor 17. Then, the press ring 19 receives the excavation reaction force via the rear grippers 26a, 26b, 26c, 26d, and the body 11 moves forward and the cutter head 1 is moved.
Each of the roller cutters 14 crushes the ground in front. Thus, the excavation reaction force of the cutter head 13 is reduced by the press ring 19.
Is received by the movable reaction force receiving device 26, and the body 11 advances so that the cutter head 13 can excavate the ground without fail.

When each of the thrust jacks 20 extends a predetermined stroke and the cutter head 13 digs a tunnel of a predetermined length, the front gripper 24 is protruded outward by the jack, thereby fixing the body 11 to the bedrock. While the rear grippers 26a, 26b, 26c, 2
6d gripper jacks 29a, 29b, 29c, 29
d to contract each gripper shoe 30a, 30b, 30
The positions c and 30d are separated from the inner wall surface of the existing tunnel to release the position holding. In this state, the thrust jacks 20 are contracted to pull the press ring 19 forward with respect to the body 11, and the movable jacks 27 are extended and contracted so that the rear grippers 26a, 26b, 26c, 26d are placed on the gripper support 35. Move forward along. At this time,
Each rear gripper 26a, 26b, 26c, 26d slides forward on the gripper support 35 in a free state with respect to the existing tunnel.

Next, when excavating, the rear grippers 26a, 26b, 26c, and 26d are held on the inner wall surface of the existing tunnel, and the holding of the body 11 by the front gripper 24 is released, as described above. In this state, the thrust jack 20 is rotated while driving the cutter head 13.
The press ring 19 extends the rear gripper 2.
Excavation reaction force is received via 6a, 26b, 26c, and 26d, and the fuselage 11 advances and the cutter head 13 crushes the ground in front. By this repetition, tunnel excavation work is performed continuously.

The driving method of the movable reaction force receiving device 26 differs depending on the excavation ground. That is, when the excavation ground is a healthy rock, the gripping force of the gripper shoe on the inner wall surface of the existing tunnel can be increased, so that only the leading rear gripper 26a functions to receive the excavation reaction force. On the other hand, if the excavated ground is soft and defective,
Since the gripping force of the gripper shoe on the inner wall surface of the existing tunnel cannot be increased, all the rear grippers 26 are required.
a, 26b, 26c, 26d function to receive the excavation reaction force.

In this embodiment, during the excavation work, the support is carried into the existing tunnel by the carry-in device, and the erector device temporarily assembles the support in a ring shape, and simultaneously with the end of the excavation by the support expansion device. This temporary assembly support is assembled by pressing against the inner wall surface of the existing tunnel.

As described above, in the TBM 10 of the present embodiment, the cutter head 13 is mounted on the front part of the body 11, while the press ring 19 is connected to the rear part via a plurality of parallel link mechanisms 23. The movable reaction force receiving device 2 with the front end of the support frame 25 fixed to the press ring 19
6 is mounted so as to be movable back and forth, and a gripper support base 35 is connected to a rear portion of the body 11 so that an angle can be adjusted by a posture adjusting jack 37. Accordingly, while the structure can be simplified, the movable reaction force receiving device 26 can be reliably and stably supported and can be adjusted to an appropriate angle, so that the excavation work can be performed stably. In addition, since the press ring 19 has a butterfly shape and the parallel link mechanisms 23 are disposed on both left and right sides, a space is formed above the parallel link mechanism 23, the press ring 19, and the movable reaction force receiving device 26. As a result, the accessibility to the inside of the body 11 from the rear is improved. Further, by disposing the belt conveyor 40 in the support frame 25, the belt conveyor 40 is disposed above the parallel link mechanism 23, the press ring 19, and the movable reaction force receiving device 26 without disturbing the operator. The space formed is used more effectively, and the accessibility to the inside of the body 11 from the rear is further improved.

FIG. 5 is a schematic side view of a tunnel boring machine as a tunnel excavator according to a second embodiment of the present invention, FIG. 6 is a sectional view taken along line VI-VI of FIG. 5, and FIG. 7 is a schematic view of a movable reaction force receiving device. Show. Note that members having the same functions as those described in the above-described embodiment are denoted by the same reference numerals, and redundant description will be omitted.

In the TBM 10a of this embodiment, FIG.
As shown in FIG. 7 to FIG. 7, a cutter head 13 is rotatably mounted on a front portion of the body 11 and can be driven and rotated by a cutter turning motor 17. This torso 11
A parallel link mechanism 23 composed of a plurality of thrust jacks 20 is provided between a press ring 19 provided behind the
Has been erected. In this case, the press ring 19 has a butterfly shape with an upper part and a lower part cut out, and each thrust jack 20 is connected to both left and right sides. And the body 1
1 is provided with a plurality of front grippers 24 for fixing the body 11 to the bedrock.

On the other hand, a front end of a support frame 25 is fixed to a substantially central portion of the press ring 19, and a movable counter member which can move independently of the body 11 behind the press ring 19. The force receiving device 41 is a support frame 2
5 are arranged. This movable reaction force receiving device 4
1 is a set of four rear grippers 41 having substantially the same configuration.
a, 41b, 41c, and 41d. The press ring 19 and each rear gripper 41a, 41b, 41c,
A moving jack 27 (not shown) is provided between the moving jack 27 and the outer jack 41d.
Has been erected.

That is, each of the rear grippers 41a, 41b, 4
1c and 41d, frame-shaped gripper boxes 42a, 42b, 42c and 42d are located outside the support frame 25, respectively.
Gripper jacks 43a, 43b, 43c, and 43d are provided in c and 42d through the support frame 25,
The gripper jacks 43a, 43b, 43c, 43d
Has a pair of left and right gripper shoes 44a, 44b, 44
c and 44d are connected to each other. Therefore, by extending each gripper jack 43a, 43b, 43c, 43d, each gripper shoe 44a, 44b, 44
c and 44d move right and left, and the gripper shoe 44
a, 44b, 44c and 44d can be pressed against the inner wall surface of the existing tunnel.

A pair of left and right anti-rotation grooves 31 are formed on the rear surface of the press ring 19, and inserted into the anti-rotation grooves 31 on the front surface of each gripper shoe 44a of the leading rear gripper 41a. Is formed to prevent relative rotation of the press ring 1.
When the pressing member 34 of the press jack 33 mounted on the presser 9 presses the rotation stopping projection 32, the rotation torque can be received integrally with the rear gripper 41 a with respect to the press ring 19. Further, the rear grippers 41a, 41b, 41c, 41
The front end of a gripper support base 35 supporting d from below is connected rotatably up and down by a connecting pin 36,
The angle can be freely adjusted by a posture adjusting jack 37.

A hopper 39 for accumulating crushed shears of the roller cutter 14 is fixed to a chamber 38 formed by the cutter head 13 and the body 11, and a belt conveyor 40 is provided with a press ring 19 and a movable reaction force. Receiving device 41 (rear grippers 41a, 41b, 41c, 41
d) is disposed above bracket 45 via a bracket 45,
The front end is connected to the lower part of the hopper 39, and the rear end extends rearward of the tunnel. Note that a bracket 46 is interposed between the gripper support 35 and the support frame 25.

The TBM 10a of this embodiment differs from the TBM 10 of the first embodiment only in the configuration of the movable reaction force receiving device, and the operation of the excavator itself is almost the same. .

As described above, in the TBM 10a of this embodiment, the press ring 19 is formed in a butterfly shape, and the parallel link mechanisms 23 are disposed on both the left and right sides. Since a space is formed above the reaction force receiving device 26, the accessibility to the inside of the fuselage 11 from the rear is good, and since the belt conveyor 40 is disposed here, the maintenance and inspection work of the belt conveyor 40 is performed. Becomes easier. Also, gripper jack 4
By arranging one 3a, 43b, 43c, 43d at the center, the working stroke can be increased.

[0046]

As described in detail in the above embodiment, according to the tunnel excavator of the first aspect of the present invention, the cutter head is rotatably mounted on the front portion of the cylindrical body by the cutter head driving means. A fuselage propulsion jack is erected between the fuselage and the propulsion support disposed behind the fuselage, and the front portion is fixed to the propulsion support and extends along the support frame extending rearward in the excavation direction. Since the movable reaction force receiving means that receives the excavation reaction force by holding the propulsion support part by pressing against the inner wall surface of the existing tunnel is movably supported,
The fuselage having the excavation mechanism and the reaction force receiving means for receiving the excavation reaction force are separately configured and movably supported on the support frame behind the propulsion support unit, so that the body can be reduced in size and weight and made compact. be able to.

According to the second aspect of the present invention, the movable reaction force receiving means includes a plurality of grippers capable of being pressed against the inner wall surface of the existing tunnel, and a movable jack for connecting the plurality of grippers to each other. By setting the number of grippers to function according to the type of excavated ground, it is possible to cope with various types of ground and to facilitate control by not using unnecessary jacks. be able to.

According to the third aspect of the present invention, a gripper support for supporting a plurality of grippers is connected to the rear portion of the fuselage, and the angle of the gripper support can be freely adjusted by the attitude adjusting jack. In addition, the movable reaction force receiving device can be reliably and stably supported, and can be adjusted to an appropriate angle. By performing the excavation work stably, reliability can be improved.

According to the tunnel excavator of the fourth aspect of the present invention, the propulsion support portion is formed in a butterfly shape with the upper and lower portions cut out, and the fuselage propulsion jacks are disposed on the left and right. Since the space is formed above the support portion and the movable reaction force receiving means, the accessibility to the body from the rear is improved, and the workability of various operations by the operator can be improved.

According to the tunnel excavator of the fifth aspect of the present invention, the support frame has a cylindrical shape, and the conveyor for discharging the earth and sand excavated by the cutter head to the outside is disposed inside the support frame. There is no need to provide a separate space for disposing the conveyor, and the inside of the fuselage can be used effectively.

According to the tunnel excavator of the present invention, the conveyor for discharging the earth and sand excavated by the cutter head to the outside is disposed above the propulsion support section and the movable reaction force receiving means. As a result, the conveyor is exposed in the fuselage, so that maintenance work can be facilitated.

According to the tunnel excavator of the present invention, the movable reaction force receiving means can be pressed against the inner wall surface of the existing tunnel by moving two gripper shoes by one gripper jack. Therefore, by disposing the gripper jack at the center of the existing tunnel, the working stroke can be increased and the gripper shoe can be reliably pressed against and separated from the inner wall surface of the existing tunnel.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a tunnel boring machine as a tunnel excavator according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 1;

FIG. 5 is a schematic side view of a tunnel boring machine as a tunnel excavator according to a second embodiment of the present invention.

FIG. 6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a schematic view of a movable reaction force receiving device.

[Explanation of symbols]

10, 10a Tunnel boring machine (TBM) 11 Body 13 Cutter head 17 Cutter turning motor (Cutter head driving means) 19 Press ring (Propulsion support part) 20 Thrust jack 23 Parallel link mechanism (Body propulsion jack) 24 Front gripper 25 Support frame 26, 41 Movable reaction force receiving devices 26a, 26b, 26c, 26, 41a, 41b, 41
c, 41d Rear gripper 31 Detent groove 32 Detent projection 33 Press jack 34 Pressing member 35 Gripper support 37 Position adjustment jack 40 Belt conveyor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takushi Sato 2-1-1 Shinhama, Arai-machi, Takasago-shi, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Kazuyuki Okamoto Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Prefecture 1-1-1 1-1 Mitsubishi Heavy Industries, Ltd. Kobe Shipyard F-term (reference) 2D054 AD17 DA02

Claims (7)

[Claims] 1. A tubular body, a cutter head rotatably mounted on a front portion of the body, cutter head driving means for driving and rotating the cutter head, and a propulsion disposed behind the body. A support portion, a fuselage propulsion jack provided between the fuselage and the propulsion support portion, a support frame having a front portion fixed to the propulsion support portion and a rear portion extending rearward in the excavation direction; Movable reaction force receiving means which is supported movably back and forth along the frame and which receives the excavation reaction force by pressing against the inner wall surface of the existing tunnel and holding the propulsion support portion in position. And tunnel excavator. 2. A tunnel excavator according to claim 1, wherein said movable reaction force receiving means comprises: a plurality of grippers capable of being pressed against an inner wall surface of an existing tunnel; and a movable jack connecting said plurality of grippers to each other. A tunnel excavator, comprising: 3. The tunnel excavator according to claim 2, wherein a gripper support for supporting the plurality of grippers is connected to a rear portion of the fuselage, and the angle of the gripper support is adjustable by a posture adjusting jack. A tunnel excavator. 4. The tunnel excavator according to claim 1, wherein the propulsion support portion has a butterfly shape with an upper part and a lower part cut out, and the fuselage propulsion jack is disposed on the left and right. Excavator. 5. The tunnel excavator according to claim 1, wherein the support frame has a cylindrical shape, and a conveyor for discharging earth and sand excavated by the cutter head to the outside is provided inside the support frame. And tunnel excavator. 6. A tunnel excavator according to claim 4, wherein a conveyor for discharging earth and sand excavated by said cutter head is disposed above said propulsion support section and said movable reaction force receiving means. A tunnel excavator. 7. The tunnel excavator according to claim 1, wherein the movable reaction force receiving means is capable of moving two gripper shoes by one gripper jack and pressing against the inner wall surface of the existing tunnel. Features a tunnel excavator.