JPH09144474A - Excavator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of gallery excavation. SOLUTION: This excavator has a cutter 21 excavating a bedrock 14 in a specified sectional shape and a frame 22 bearing the peripheral walls of drifts 2, 3 formed by the cutter 21. The frame 22 is divided properly in the circumferential direction, and formed movably towards the inside of a machine body. The frame 22 is divided into front and rear sections in the direction of excavation, and a shield jack 50 for giving specified driving force is mounted between the front-section frame 23 and the rear-section frame 24. According to the constitution, the full face tunneling of the drifts 2, 3 is conducted while timbering can be performed in parallel, and an improvement in the operating efficiency of excavation is attained. This excavator can be carried out easily through a gallery by reducing the diameters of the frames after excavation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excavator for excavating underground to form a side gallery in a coal mine.

[0002]

2. Description of the Related Art Generally, a long-wall type mining method as shown in FIG. 13 is known as a method for mining underground coal. This long-wall type mining method excavates parallel roadway tunnels 2 and 3 on both sides of a coal seam 1 to be mined, and also connects the tips thereof to excavate a tip tunnel 4 and a cutter loader (drum) to the tip tunnel 4. An excavating machine such as a cutter is installed, the long wall of the tip gallery 4 is cut toward the front side (direction of arrow a in the figure), and the mine is scraped out to the gallery 2 or 3 and carried out by a belt conveyor or the like.

As a machine for excavating the roadside tunnels 2, 3, a tunnel excavator (continuous minor) 5 as shown in FIG. 14 is known. In this tunnel excavator 5, a truncated cone-shaped excavating head 8 is provided at the tip of a boom 7 extending in front of the machine body 6, and the boom 7 is swung up and down or left and right to have a predetermined cross-sectional shape. It is supposed to be drilled in. The excavated coal and rocks are scraped by a loading device 9 provided at the front of the machine body, transferred by a conveyor 10 extending rearward in the center of the machine body, and loaded on a transportation vehicle 11 that follows and travels rearward. It is supposed to be.
This tunnel excavator 5 is normally operated by an operator and runs on a crawler 12.

[0004]

The conventional shaft excavator 5 has a problem that the excavation efficiency is poor because the size of the excavation head 8 is smaller than the cross section to be excavated. The excavated tunnels 2, 3 and 4 are designed to be supported and maintained by driving rock bolts on the roof and side walls, but in order to ensure the safety of the driver of the tunnel excavator 7, a little excavation is required. There is no choice but to follow a construction procedure in which the operation of the excavation head 8 is stopped to drive the rock bolt, and then the operation of the excavation head 8 is restarted to excavate.
Therefore, the excavation speed becomes slower, and when the roadside tunnels 2 and 3 extend for several kilometers, much of the entire mining process had to be devoted to the tunnel excavation.

In order to solve such a problem, a shield machine having a proven track record is used for mountain tunnels, etc.
It is conceivable to excavate the entire cross-sections of the roadside tunnels 2 and 3 and excavate rock bolts in parallel. However, this type of shield excavator is designed so as to propel the segment built in the tunnel wall by reaction force, and therefore cannot be directly applied to the tunnel excavation without lining. Also, if the tunnel machine has reached the tip of the planned length (coal seam), it must return through the inside of the tunnel, but the shield machine does not have the function of retreat, so recovery is not possible. It's extremely difficult. If it is left on the tip side of the roadside tunnels 2 and 3, it is necessary to prepare an excavator for each coal seam, and the facility cost becomes excessive, which is unrealistic and difficult to use at all.

[0006]

In order to solve the above-mentioned problems, the present invention comprises a cutter for excavating the ground in a predetermined cross-sectional shape, and a frame for supporting the peripheral wall of the tunnel formed by the cutter. It is formed so as to be movable toward the inside of the body by appropriately dividing it in the circumferential direction. It is preferable that the frame is divided into front and rear in the excavation direction, and an expansion / contraction means for applying a predetermined propulsive force is provided between the front frame and the rear frame.

With the above structure, the excavation of the entire section of the roadway can be performed, and the support work such as the lock bolt can be performed in parallel, and the efficiency of the excavation work can be improved.
Further, after the excavation, the frame can be moved toward the inside of the machine body so that the entire machine body has a reduced diameter and can be easily carried out through the excavated tunnel. Then, by alternately reducing the diameters of the front and rear frames and driving the expanding and contracting means, it is possible to take a propulsion reaction force in the rear frame, and it is possible to excavate reliably and with high efficiency.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 4 show a case where the present invention is applied as a machine for excavating and forming a roadside gallery in a coal mine. This excavator includes a cutter 21 for excavating a natural ground (coal bed or bedrock) 14 in an oval cross-sectional shape that is long in the left-right direction when viewed from the front, and a roadside tunnel 2 formed by excavation that is connected to the rear of the cutter 21. Frame 22 that supports the surrounding walls
And is mainly composed of

The frame 22 is appropriately divided into front and rear in the direction of excavation, and the front frame 23 and the rear frame 24 thereof are substantially in contact with the floor surface 15 of the roadway shafts 2 and 3 and form a main body frame 25. And an upper frame 26 that supports the roof 13, and left and right side frames 27 and 28 that support the side walls. The frames 25 ... 28 are arranged at predetermined intervals in the circumferential direction and have an outer shape (oval shape) substantially corresponding to the cross section cut by the cutter 21. That is, the upper frame 26
Is assembled flat with an upper plate 29 having a straight cross section, and the side frames 27, 28 are assembled with outer plates 30, 31 having a circular cross section. The main body frame 25 includes a lower portion 33 formed in a rectangular shape having a bottom plate 32 having a straight cross section, a vertical portion 34 standing on both sides of the lower portion 33 in the longitudinal direction, and a vertical portion 34. It is composed of an upper horizontal portion 35 and an upper vertical portion 36 that connect the upper ends, and the whole is assembled into a substantially rectangular parallelepiped shape. A partition wall 37 is attached to the front end of the main body frame 25 to separate it from the cutter 21 side.

The body frame 25 and the upper frame 2
6 and the side frames 27, 28 are provided with expansion / contraction jacks 38, 39, respectively, so that the diameter can be reduced toward the inside of the body, and guides 40, 41 for guiding the expansion / contraction are provided. Has been. In the expansion / contraction jack 38 for the upper frame 26, as shown in FIG. 8, the cylinders 42 are vertically mounted in front of and behind the upper vertical portions 36 of the left and right of the main body frame 25, and are retracted from the cylinder 42. The tip of the piston rod 43 is connected to the lower surface of the upper frame 26. Ie upper frame 2
6 is movable within a predetermined lifting range within the distance between the lower surface of the upper frame 26 and the upper surface of the upper vertical portion 36 of the main body frame 25. The guide 40 is shown in FIG.
As shown in FIG. 9 and FIG. 9, each of the vertical portions 34 is composed of a cylindrical body 44 erected on the upper end of the vertical body 34, and a columnar body 45 suspended from the upper frame 26 coaxially with the cylindrical body 44. By sliding inside 44, the vertical movement of the upper frame 26 is guided. Further, the expansion / contraction jacks 39 for the left and right side frames 27, 28 are provided on the front and rear sides and on the upper and lower sides of the main body frame 25, respectively. As shown in FIG. The tip of the piston rod 47 is attached to the inner surfaces of the side frames 27 and 28, respectively. And guide 41
Are arranged side by side in the vicinity of the expansion / contraction jack 39, and as shown in FIG. 7, the pillar portion 48 horizontally projected from the inner surfaces of the side frames 27 and 28 and the pillar portion divided into the vertical portion 34. Four
It is formed of a tubular portion 49 on which 8 is slid.

Between the front frame 23 and the rear frame 24, there is provided a propulsion jack 50 which is an expansion / contraction means for applying a predetermined propulsive force required for excavation. The propulsion jacks 50 are arranged at the four upper, lower, left and right corners of the main body frame 25, and the jack main body 51 is provided on the lower portion 33 and the upper vertical portion 52 of the rear frame 24 along the longitudinal direction thereof. Therefore, especially the upper vertical portion 52
Is slightly stronger than the upper vertical portion 36 of the front frame 23 so that the propulsion jack 50 can be sufficiently supported. The left and right expansion / contraction jacks 39 and guides 41 of the rear frame 24 are provided at positions where they do not interfere with the propulsion jack 50. The tip of the piston rod 53 of the propulsion jack 50 is detachably connected to the rear end of the body frame 25 of the front frame 23. That is, the propulsion jack 50 is the expansion / contraction jacks 38, 39.
The expansion / contraction drive is appropriately interlocked with the expansion / contraction of the frame to drive the front frame 23 and the cutter 21 forward by the reaction to the rear frame 24, and the rear part with respect to the forward front frame 23. Frame 24
Are attracted to.

Next, the cutter 21 is, as shown in FIG.
A pair of left and right main cutters 61 and 62 that rotate around the axis of the excavation direction, and a pair of upper and lower trimming cutters 63 for excavating the portion left uncut by the main cutters 61 and 62 (indicated by the two-dot chain line in the figure). , 64. The main cutters 61 and 62 include a shaft 65 serving as a rotating shaft, three spokes 66 radially extending from the shaft 65, and bits (cutter picks) 67 protruding forward at a predetermined interval in the longitudinal direction of the spokes 66. It consists of and. A bit 68 is also planted in an arc shape at the front end of the shaft 65. Further, a water injection nozzle may be provided on the shaft 65 to inject a spray for dust suppression and cutting spark prevention on the face. The left and right main cutters 61 and 62 are the spokes 6
6 are arranged on the same plane and in a phase relationship such that one spoke 66 enters the middle of the other spoke 66.

As shown in FIG. 1, the shaft 65 extends rearward and is axially supported by the vertical portion 34 of the main body frame 26, and a gear 69 is provided at the extending end thereof. The gear 69 is meshed with a gear 71 of an electric motor 70 mounted on the lower portion 33 of the main body frame 26. A speed reducer 72 is provided between the gear 71 and the electric motor 70. That is, the rotational force of the electric motor 70 is appropriately transmitted to the pair of main cutters 61 and 62, and these are rotationally driven in the opposite directions to excavate the front face. Then, as shown in FIG. 3, the outer peripheral end side 66 a of the spoke 66 is detachably divided and is formed so as to become shorter in accordance with the diameter reduction of the frame 22. As for this division structure, for example, the division surfaces 73 of the spokes 66 may be formed in a concavo-convex shape so as to be fitted together, and then fastened with bolts and nuts (not shown). In FIG. 3, only the spokes 66 projecting upward or left and right when the diameter is reduced are shown as a structure that can be divided, but all the spokes 66 may be shortened.

Further, a bucket 74 is provided on the rear side of the spokes 66 so that the excavated coal or rock is picked up and thrown into a conveyor 76 for carrying out via a chute 75. Two chutes 75 are provided corresponding to the left and right main cutters 61, 62, and are inclined downward toward the center of the machine body. As shown in FIG. 1, the conveyor 76 is formed by an endless belt 78 wound around a roller 77 located below and in front of the chute 75. Then, as shown in FIG. 8, the endless belt 78
The conveyance surface side is supported by a guide roller 79 appropriately arranged in the main body frame 25, and after slightly rising, it extends horizontally rearward and is excavated to another conveyor or a transportation vehicle (not shown) located at the rear of the machine body. It is designed to transport coal or rocks.

The trimming cutters 63 and 64 are formed in a sawtooth shape by a cutter body 80 having a predetermined length and bits 81 planted at predetermined intervals along the longitudinal direction thereof, and the main cutters 61 and 62. It is provided at the front end of the front frame 23 near the rear of the bucket 74. That is, the upper trimming cutter 63 is located on the upper frame 26.
Further, the lower trimming cutters 64 are arranged on the lower portion 33 of the main body frame 25, respectively. As shown in FIG. 5, the cutter body 80 is accommodated in a box-shaped bracket member 82 with only the bit 81 exposed, and is supported by a guide rod 83 extending in the left-right direction via a moving block 84. ing. Both ends of the guide rod 83 are supported by the left and right side plates 82a of the bracket member 82. The moving block 84 is fitted to the guide rod 83 and is slidable in the longitudinal direction thereof. A return cylinder 85 is connected to the moving block 84. Return cylinder 85
Is provided in parallel with the guide rod 83, and the base end of the cylinder body 85 a of the base member 8 is the rear portion of the bracket member 82.
2b is supported via a bracket 86, and the tip of a piston rod 85b is connected to a moving block 84 via a bracket 87. That is, the trimming cutters 63 and 64 reciprocate in the left-right direction by expanding and contracting the return cylinder 85. The returning range is restricted by a stopper 83a provided on the guide rod 83.

As shown in FIG. 6, the bracket member 82 is provided with an actuator 88 for appropriately moving the trimming cutters 63 and 64 inward and outward of the machine body. The actuator 88 has a cylinder portion 88.
The base end of a is pivotally supported inside the lower frame 33 or the upper frame 26 via a bracket 89, and the tip of the piston rod 88b is pivotally supported on the back side of the base plate 82b via a bracket 90. And in the vicinity of the fulcrum,
The board 82b is attached to the frames 33, 2 via the bracket 91.
A support shaft 92 for supporting 6 is provided in the left-right direction. In other words, by extending and retracting the actuator 88 to raise and lower the bracket member 82 about the support shaft 92,
The trimming cutters 63 and 64 are movable in and out of the machine body. Therefore, as shown in FIG. 6A, during normal excavation, the bit direction of the trimming cutters 63 and 64 is held at a predetermined angle θ with respect to the vertical direction, for example, 45 degrees, and if necessary, The actuator 88 is retracted, and the bracket member 82 is rotated clockwise in the drawing as shown in FIG. 6B, so that the bit 81 is directed toward the inside of the machine body and the entire bracket member 82 is machined. It is designed to be located inside the body. In addition, for example, when adjusting the amount of excess digging or performing bending digging, the actuator 88 is extended vertically or both or more than usual, and the bit 81 is rotationally moved so as to largely project to the outside of the fuselage. ) Can be held. When the trimming cutters 63 and 64 are directed toward the inside of the machine body, the bracket member 82 may interfere with the partition wall 37. Therefore, in order to avoid this, FIG.
As shown in FIG. 5, the portions of the frames 33 and 26 supporting the actuator 88 may be formed to be slidable in the front-rear direction, and the other actuator 93 may be extended to advance this portion by the appropriate distance L. Good. In addition, an inclined guide plate 82c for appropriately guiding excavated coal or the like is formed on the inner side of the bracket member 82 in the body,
On the upper side, it leads to the chute 75, and on the lower side, it pushes forward according to the excavation so that the main cutter 6
1, 62 buckets are scooped. Further, the bracket member 82 is provided with an auxiliary guide 94 in parallel behind the guide rod 83 in order to sufficiently receive the excavation reaction force of the trimming cutters 63 and 64.

In addition, as shown in FIG. 1, the upper frame 26 of the front frame 23 is provided with a covering member 95 which moves along the roof 13 of the roadside tunnels 2 and 3 formed by the cutter 21. Has been. The cover member 95 is the upper plate 2
9 is formed as an outer plate of the two stacked plates and is slidable with respect to the inner plate 96. A cylinder 97 is provided in the upper frame 26, and the tip of the piston rod 97a is connected to the cover member 95, and by extension thereof, projects toward the front of the cutter 21. That is, when exchanging bits during excavation or when performing maintenance and inspection, an operator enters between the face and the cutter 21, but at this time, a rock fall from the roof 13 immediately after excavation is prevented and the operator is prevented. You can ensure the safety of.

Further, as shown in FIG. 9, the main body frame 2
5 is provided with a vent pipe 98 for ventilation. The rear frame 24 has jacks (38,
39, 50 ...) and an operator's cab (not shown) for controlling the excavation. This operator's cab may be provided on the side of the wellhead separated from the frame 22 so that the excavation operation can be performed by remote control. Further, a lock bolt 99 is attached to the rear deck (not shown) of the rear frame 24 to form the roof 13 of the roadside tunnels 2 and 3.
And a bolt insertion device 100 for insertion into the side wall. The bolt inserting device 100 is not necessarily provided in the rear deck, but may be separately mounted in a traveling vehicle that follows the excavation.

Next, by using the excavator with the above-mentioned structure,
The process of excavating No. 3 will be described. As shown in FIG. 10, first, in a state where the propulsion jack 50 is contracted,
The front frame 23 contracts the expansion / contraction jacks 38, 39 into a reduced diameter state so that the outer frame has an outer shape slightly smaller than the cross section excavated by the cutter 21. That is, an appropriate gap S is provided between the roof 13 and the upper surface of the upper frame 26.
₁ is formed, side wall and side frame 2
Similar gaps (not shown) are also formed between 7, and 28. Then, the rear frame 24 is brought into a state in which, in addition to the main body frame 25, the frames 26 ... 28 are appropriately pressed against the peripheral wall over the entire circumference by the extension of the expansion / contraction jacks 38, 39 (a in FIG. 10). . In this state, the main cutters 61 and 62 and the trimming cutters 63 and 64 are driven, and the conveyor 76 is driven. Then, when the propulsion jack 50 is extended, the main cutters 61 and 62 excavate substantially the entire face by the rotation and the pressing force, and the trimming cutters 63 and 64 cause the main cutter 6 to excavate.
The portion left uncut by 1, 62 is excavated (Fig. 10).
B). At this time, the trimming cutters 63 and 64 only cut at the positions where the upper ends and the lower ends of the pair of main cutters 61 and 62 are tangentially connected to each other. Due to the nature of the coal seam, when a crack is formed, it is easily separated from the natural ground 14 due to its own weight or vibration. The coal or rock excavated by the cutter 21 is scooped by the bucket 74 and is carried out rearward by the chute 75 and the conveyor 76.

When the propulsion jack 50 is dug to the maximum extent (c in FIG. 10), the front frame 23
The expansion / contraction jacks 38, 39 of FIG. 2 are extended to bring the upper frame 26 and the side frame 27 into pressure contact with the peripheral wall (S ₂ ), and the expansion / contraction jacks 38, 39 of the rear frame 24 are contracted. , Each frame 26, 27
Is separated from the roof 13 and the side wall. That is, an appropriate gap S ₁ is formed between the top surface of the upper frame 26 of the rear frame 24 and the roof 13. In this state, the propulsion jack 50 is retracted, and the rear frame 24
Is pulled forward (d in FIG. 10). In parallel with this pulling, or after pulling is completed, a hole for inserting a lock bolt is made in the roof 13 and the side wall of the dug section with a drill provided in the bolt inserting device 100, and the hole is used to stabilize. The chemical liquid for the purpose of injection is injected, and the lock bolt 99 is inserted and fixed with the nut. In this support, a net or the like may be used together to fix the lock bolt 99. When the propulsion jack 50 is contracted to the minimum (e in FIG. 10), the front frame 23 is contracted again,
The diameter of the rear frame 24 is expanded to the initial state (see FIG. 10).
Return to a) and continue the excavation.

When the excavation reaches the planned length, the expansion / reduction jacks 38, 39 are retracted to the maximum extent as shown in FIG. 11, and the frame outer shape is significantly smaller than the cross section of the roadside tunnels 2, 3. Reduce the diameter so that That is, the frame 26 ...
A large gap S ₃ is formed between 28, the roof 13 and the side wall. Then, the connection between the piston rod 53 of the propulsion jack 50 and the front frame 23 is released,
The towing vehicle 101 traveling along the roadways 2 and 3 is connected to the connecting member 102.
The rear part frame 24 is connected via (a in FIG. 11). Then, the rear frame 24 is carried out by causing the towing vehicle 101 to travel to the pit side. At this time, the rear end of the rear frame 24 is slightly lifted so that only the front end is in contact with the ground and the frictional resistance is reduced (FIG. 11).
B). A roller or the like may be provided below the front end of the rear frame 24 for this pulling. If the natural ground 14 is a coal bed, the excavation surface (floor surface 15) is smooth and the friction coefficient μ is about 0.4, so it does not cause a major obstacle in towing, and it is a relatively small towing vehicle. You can quickly carry out at 101. When this unloading is completed, the towing vehicle 101 is subsequently connected to the front frame 23. At this time, if the lower trimming cutter 64 is in the same position as the outer surface of the frame or is left in a protruding state, the friction resistance due to grounding increases and the cutter may be damaged. Fig. 6
As shown in (b), it is in a state of being housed inside the body. Then, as the towing vehicle 101 travels, the rear frame 2
Carry out in the same manner as 4 (c). In some cases, as shown in FIG. 12, the front frame 23 and the rear frame 24 are connected to the towing vehicle 101 in the connected state,
You may carry it out.

When the excavation of the roadside tunnels 2 and 3 is completed, the tip tunnel 4 connecting the tips thereof is excavated (see FIG. 13 above). At the time of this excavation, the direction may be changed to a right angle so that the same excavator can be used to continue excavation in the roadside roads 2 and 3, but it is difficult to change the direction in a narrow space, and the tip roadway 4 is Since it is extremely short compared to the layer tunnels 2, 3, the conventional tunnel excavator (see FIG. 14) is carried in and excavated after the excavator of the present invention is carried out. When this excavation is completed, the drum cutter is carried in and installed in the tip tunnel 4 to excavate the coal seam between the two roadside tunnels 2 and 3, and full-scale coal mining is performed.

In this way, the cutter 21 for excavating with an oval cross section, and the roadway 2, formed by the cutter 21,
Since the frame 22 supporting the peripheral wall of No. 3 and the frame 22 are formed so that the diameter can be freely reduced, the excavation of the entire cross section of the tunnel can be performed efficiently at the same time, and the construction of the lock bolt 99 can be performed in parallel. The efficiency is greatly improved, and the unloading after the excavation can be carried out very easily and quickly, which can contribute to the drastic reduction of the construction period for the excavation of the roadside tunnels 2 and 3 and the coal mining. Then divide the frame 22 into front and back,
Since the propulsion jack 50 is provided between them, the propelling reaction force can be reliably obtained without depending on the frictional force with the bottom wall of the tunnel due to the weight of the machine body, in combination with the structure in which the frame can be freely expanded and contracted, and the excavation speed can be increased. A further improvement of is achieved.

The circumferential spacing and expansion / contraction range of the frame 22 need only be such that they do not interfere with excavation and retreat, and are set according to the size of the excavation cross section, the protruding length of the head of the lock bolt 99, and the like. It should be appropriately selected. Further, in this embodiment, the frame is divided into four substantially vertically and horizontally, but it is sufficient that the frame is divided and formed so as to be expandable and contractible as a whole. Further, the divided frames are not necessarily spaced apart in the circumferential direction, and may be configured to keep a substantially sealed state in the excavation state and partially overlap each other in the reduced diameter state. Further, the case of digging along the underground gallery 22 of the coal mine is illustrated, but the present invention is not limited to this, and can be widely applied to tunnel excavation under similar construction conditions.

[0026]

In summary, according to the present invention, the excavation efficiency is greatly improved and the post-excavation can be carried out very easily and quickly, which contributes to a significant reduction in the work period of the coal mining process. In addition, the propulsion reaction force can be reliably obtained, and the excavation speed can be further improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a view taken along the line AA of FIG. 1;

FIG. 3 is a front view for explaining the operation of FIG.

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

5 is a plan view showing a main part of FIG. 1. FIG.

FIG. 6 is a side view of FIG. 5;

7 is a cross-sectional view taken along the line CC of FIG.

8 is a cross-sectional view taken along the line DD of FIG.

FIG. 9 is a cross-sectional view taken along the line EE of FIG.

FIG. 10 is a side sectional view showing an excavation process by the excavator of FIG. 1.

FIG. 11 is a side sectional view showing a step of collecting and removing the excavator of FIG. 1.

FIG. 12 is a side cross-sectional view showing another recovery and removal method of FIG.

FIG. 13 is a perspective view for explaining a long-wall mining method in a coal mine.

FIG. 14 is a perspective view showing a conventional machine.

[Explanation of symbols]

 2, 3 Layer mine (road) 13 Roof (circumferential wall) 14 Ground 21 Cutter 22 Frame 23 Front part frame 24 Rear part frame 25 Main frame 26 Upper frame 27, 28 Side frame 38, 39 Expansion / contraction jack 50 Propulsion Jack (expansion and contraction means) 61,62 Main cutter 63,64 Trimming cutter 95 Covering member

Claims (2)

[Claims] 1. A cutter for excavating a ground in a predetermined cross-sectional shape, and a frame for supporting a peripheral wall of a tunnel formed by the cutter, the frame being appropriately divided in the circumferential direction and moved toward the inside of the machine body. An excavator characterized by being freely formed. 2. The excavator according to claim 1, wherein the frame is divided into front and rear in the direction of excavation, and expansion and contraction means for applying a predetermined propulsive force is provided between the front frame and the rear frame. .