JP2020070689A - Tunnel excavator and tunnel excavation method - Google Patents

Abstract

To reduce the amount of excavation.SOLUTION: A tunnel excavator 100 comprises: a body 10 for supporting an inner wall surface of a tunnel T; a tubular body 20 mounted on the body 10, having a cutter bit 21 for excavating an outside of an existing pipe OP and internally containing the existing pipe OP; and a motor 30 for rotating the tubular body 20 with respect to the body 10. The motor 30 is arranged inside a virtual extension inner peripheral surface obtained by extending the inner peripheral surface of the cutter bit 21 rearward along the axial direction of the tunnel T.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tunnel excavator and a tunnel excavation method.

  If the existing pipe constructed in the ground is deteriorated, it is necessary to construct a new pipe body in the ground. When constructing a new pipe in the ground while leaving the existing pipe, it is necessary to have sufficient space in the ground, and it is difficult to secure sufficient space in urban areas and urban areas where underground structures are dense. There is a case. For this reason, it has been proposed to dismantle the existing pipe and construct a new pipe in the space formed by dismantling the existing pipe.

  Patent Document 1 discloses a tunnel excavator that excavates a tunnel along an existing pipe. This tunnel excavator includes a tubular body, a cutter bit provided at the front end of the body, and a drive unit that rotates the cutter bit. The cutter bit is rotated with respect to the body by the driving means to excavate the ground outside the existing pipe. As the tunnel is dug, the existing pipe is enclosed in the body. The existing pipe is dismantled by the dismantling means in the body, and a new pipe is built on the inner wall surface of the tunnel.

JP 2002-13386 A

  In the tunnel excavator disclosed in Patent Document 1, the driving means for rotating the cutter bit has an inner wall surface of an excavation space formed by excavating the cutter bit and an outer peripheral surface of an existing pipe when the tunnel bit is excavated. It is placed between and. Therefore, it is necessary to form a space for passing the drive means by excavating the cutter bit, which increases the amount of excavation by the cutter bit.

  The present invention aims to reduce the amount of excavation.

  The present invention is a tunnel excavator for excavating a tunnel along an existing pipe, which has a body supporting an inner wall surface of the tunnel, and an existing pipe having an excavation unit attached to the body for excavating the outside of the existing pipe. The drive unit includes a tubular body to be enclosed and a drive unit that rotates the tubular body with respect to the body. The drive unit is a virtual extension inner circumference in which the inner circumferential surface of the excavation unit is extended backward along the axial direction of the tunnel. It is located inside the surface.

  Further, the present invention is a tunnel excavation method for excavating a tunnel along an existing pipe by using the tunnel excavator, wherein the tunnel excavator includes a body supporting an inner wall surface of the tunnel and an existing pipe installed on the body. A tubular body having an excavation portion for excavating the outside of the existing pipe and a drive portion for rotating the tubular body with respect to the body, and the tunnel excavation method is a tubular body using the drive portion. An excavating step of excavating the outside of the existing pipe by advancing the tubular body while rotating the tubular body and inserting the existing pipe inside the tubular body, and a disassembling step of disassembling the existing pipe inside the tubular body, Equipped with.

  According to the present invention, the amount of excavation can be reduced.

It is sectional drawing of the tunnel excavator which concerns on 1st Embodiment of this invention. It is sectional drawing which follows the II-II line shown in FIG. It is an enlarged view of the III section shown in FIG. It is sectional drawing of the tunnel excavator which concerns on 2nd Embodiment of this invention. It is sectional drawing of the tunnel excavator which concerns on 3rd Embodiment of this invention. It is sectional drawing of the tunnel excavator which concerns on 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
First, with reference to FIG. 1 to FIG. 3, a tunnel excavator 100 and a tunnel excavation method according to a first embodiment of the present invention will be described. The tunnel excavator 100 is a device for excavating a tunnel T along an existing pipe OP constructed in the ground, and dismantles the existing pipe OP to provide a new pipe body NP in a space formed by dismantling the existing pipe OP. Used when building. Hereinafter, a hole formed by using the tunnel machine 100 and exposing the wall surface of the natural ground is referred to as a "tunnel T".

  First, a method of excavating a tunnel T using the tunnel machine 100 will be briefly described with reference to FIG. Here, a case will be described in which the existing pipe OP is formed of a plurality of segment rings SR, and the backing material BM is filled between the outer peripheral surface of the segment ring SR and the inner wall surface of the ground. In such an existing pipe OP, the segment rings SR adjacent to each other in the axial direction of the tunnel T are connected to each other.

  As shown in FIG. 1, a tunnel machine 100 includes a body 10 that supports an inner wall surface of a tunnel T, a tubular body 20 rotatably mounted on the body 10, and the tubular body 20 with respect to the body 10. And a motor 30 as a drive unit for rotating the motor. A cutter bit 21 as an excavation portion for excavating the natural ground is formed at the tip of the tubular body 20. The outer diameter of the cutter bit 21 is substantially equal to the outer diameter of the body 10, and by rotating the tubular body 20 using the motor 30 while the cutter bit 21 is pressed against the ground, the ground is outside the body 10. It is excavated with an inner diameter approximately equal to the diameter.

  The cutter bit 21 of the tubular body 20 is pressed against the ground by using the propulsion jack 40 provided inside the body 10. Specifically, the propulsion jack 40 obtains a reaction force from the end surface of a new pipe body NP that is sequentially constructed by newly assembling the segment ring NSR inside the body 10 as the tunnel T is dug, and then the body 10 is obtained. Also, the tubular body 20 is pushed in the excavation direction, and the cutter bit 21 is pushed against the natural ground.

  A tail seal 15 is provided on the rear end side of the body 10 along the inner circumference of the body 10. The tail seal 15 closes the gap between the new segment ring NSR and the body 10 to prevent the earth and sand from flowing into the body 10. In the first embodiment, the new segment ring NSR is assembled inside the fuselage 10 between the propulsion jack 40 and the tail seal.

  The method of constructing the tubular body NP inside the body 10 and obtaining a reaction force from the tubular body NP to push the body 10 and the tubular body 20 forward is also called a shield construction method. The body 10 and the tubular body 20 may be pushed together with a new segment ring NSR. That is, the body 10 and the tubular body 20 may be pushed by a so-called propulsion method instead of the shield method which is the first embodiment.

  In the following, the direction in which the tubular body 20 and the body 10 are pushed forward is referred to as “front”, and the opposite direction to the front is referred to as “rear”.

  The cutter bit 21 is formed in an annular shape having an inner diameter larger than the outer diameter of the existing pipe OP, and excavates the ground and the backfill material BM outside the existing pipe OP. The segment ring SR of the existing pipe OP is formed of, for example, a concrete material or a steel material so as to support the wall surface of the natural ground, and its hardness is higher than that of the natural ground and the backing material BM. Therefore, as compared with the case where the segment ring SR is cut and the tunnel T is excavated, wear and breakage of the cutter bit 21 of the tubular body 20 can be reduced.

  When the tubular body 20 is pushed in the excavation direction while excavating the natural ground and the backfill material BM using the cutter bit 21, the existing pipe OP is inserted into the tubular body 20. The existing pipe OP is disassembled for each segment ring SR using a device (not shown) (for example, a concrete cutter, a water jet, or the like).

  In the existing pipe OP including a plurality of segment rings SR, cutting of the connecting portion that connects adjacent segment rings SR is easier than cutting of the segment rings SR. Therefore, the workability can be improved by cutting the connecting portion of the adjacent segment rings SR and disassembling the existing pipe OP for each segment ring SR.

  The dismantled existing pipe OP is carried out through the inside of the undisassembled existing pipe OP. The tunnel T is excavated along the existing pipe OP by excavating the rock mass on the outside of the existing pipe OP and the backfill material BM and disassembling the existing pipe OP.

  The new pipe body NP is constructed in the space formed by disassembling the existing pipe OP. Therefore, it is possible to easily secure a space for constructing a new pipe body NP, as compared with a case where a new pipe body NP is constructed in the ground while leaving the existing pipe OP.

  Next, the structure of the tunnel machine 100 will be described in detail.

  As shown in FIG. 1, the tubular body 20 includes a casing 22 provided with a cutter bit 21 at its tip end and extending along the axial direction of the tunnel T, and a small diameter portion 23 arranged inside the body 10. An annular connecting portion 24 that connects the casing 22 and the small diameter portion 23 is provided.

  The small diameter portion 23 is rotatably supported by the body 10 via a bearing 11. Further, the small diameter portion 23 is connected to the motor 30 via a speed reducer (not shown). Therefore, the torque of the motor 30 is transmitted to the cutter bit 21 through the small diameter portion 23, the connecting portion 24, and the casing 22.

  As shown in FIGS. 1 and 2, the motor 30 is fixed to the body 10 via an annular protruding portion 12 that protrudes radially inward from the inner peripheral surface of the body 10, and the inner peripheral surface of the cutter bit 21. Is arranged inside the virtual extension inner peripheral surface that extends rearward. Therefore, at the time of excavation of the tunnel T, the motor 30 passes through the space inside the virtual extension inner peripheral surface of the cutter bit 21 in the internal space of the tunnel T. Therefore, the space through which the motor 30 passes can be formed by disassembling the existing pipe OP instead of excavating by the cutter bit 21. As a result, the thickness of the cutter bit 21 in the radial direction of the tunnel T can be reduced, and the amount of excavation can be reduced.

  In the tunnel machine 100, the outer diameter of the body 10 is substantially equal to the outer diameter of the casing 22, and the outer peripheral surface of the body 10 substantially coincides with the virtual extended outer surface of the casing 22. When the tunnel T is being advanced, the body 10 passes through the inner space of the tunnel T, which is an excavation pit formed by excavating the cutter bit 21, so that the body 10 can proceed without great resistance from the ground. ..

  In addition, as shown in FIG. 1, the outer diameter of the casing 22 is substantially equal to the outer diameter of the cutter bit 21, and supports the inner wall surface of the tunnel T. The inner diameter of the casing 22 is larger than the inner diameter of the cutter bit 21, and contains the existing pipe OP.

  The width L1 of the casing 22 in the axial direction is larger than the width L2 of the segment ring SR of the existing pipe OP, and the casing 22 can include at least one segment ring SR. Therefore, the existing pipe OP can be disassembled inside the casing 22 for each segment ring SR. That is, in the tunnel machine 100, the space for disassembling the existing pipe OP (hereinafter referred to as “disassembly space”) is formed by the casing 22. Note that FIG. 1 shows a state in which the casing 22 includes the two segment rings SR of the existing pipe OP.

  The motor 30 is arranged behind the casing 22. In other words, the dismantling space is arranged in front of the motor 30. Therefore, it is possible to prevent the device for disassembling the existing pipe OP and the motor 30 from interfering with each other inside the casing 22. Therefore, the disassembly workability can be further improved.

  As shown in FIG. 3, the inner peripheral surface of the casing 22 is provided with a seal 50 that comes into close contact with the backing material BM or the segment ring SR remaining after excavation by the cutter bit 21. With the seal 50, the casing 22 and the remaining backfill material BM or segment ring SR can be closed, and muddy water in the ground can be prevented from flowing into the tubular body 20 and the body 10. ..

  The seal 50 wears as the tubular body 20 rotates. Therefore, when the amount of muddy water in the ground is small and the blocking between the casing 22 and the backing material BM or the segment ring SR is unnecessary, the close contact of the seal 50 to the backing material BM or the segment ring SR is released, It is preferable to prevent wear of the seal 50 due to rotation of the tubular body 20.

  In the tunnel machine 100, the seal 50 can be switched between a state in which the closing function is effective and a state in which the closing function is released. Specifically, the seal 50 is made of an annular elastic tube member, and is connected to a pump (not shown) as a fluid supply means through a pipe 51 provided on the inner peripheral surface of the casing 22. When a fluid (for example, air) is supplied to the inside of the seal 50, the seal 50 expands and comes into close contact with the backfill material BM or the segment ring SR, and the closing (sealing) function becomes effective. When the fluid is discharged from the inside of the seal 50, the seal 50 contracts, the close contact with the backfill material BM or the segment ring SR is released, and the closing (sealing) function is released.

  By rotating the closed state of the seal 50 between the effective state and the released state according to the amount of muddy water, the rotation of the tubular body 20 is prevented while preventing the inflow of muddy water into the tubular body 20 and the body 10. It is possible to reduce wear of the seal 50 due to the above. The switching of the state of the seal 50 depending on the amount of muddy water may be performed by an operator or a controller.

  Although not shown, a seal is also provided between the connecting portion 24 of the tubular body 20 and the body 10, and the muddy water of the natural ground passes through the interior of the body 10 through the space between the tubular body 20 and the body 10. To prevent it from flowing into.

  Next, a method of excavating the tunnel T using the tunnel machine 100 will be described.

  First, the cutter bit 21 is pressed against the rock mass and the backfill material BM outside the existing pipe OP, the cutter bit 21 is rotated, and the tubular body 20 is moved forward to excavate the rock mass and the backfill material BM. The existing pipe OP is inserted into the tubular body 20 (excavation step). At this time, the body 10 moves forward together with the tubular body 20.

  When the casing 22 of the tubular body 20 inserts at least one segment ring SR into the casing 22 of the tubular body 20 and the tip of the casing 22 is partially inserted into the next segment ring SR, excavation by the cutter bit 21 is performed. And the segment ring SR is disassembled inside the casing 22 (disassembly process). Thereby, the space through which the motor 30 passes can be formed. The casing 22 of the tubular body 20 is supported by the segment ring SR next to the segment ring SR being dismantled, and prevents the earth and sand from flowing into the internal space where the segment ring SR is dismantled.

  Next, the cutter bit 21 is rotated again to restart excavation of the natural ground and the backfill material BM. The tunnel excavation process 100 is completed by repeating the excavation process and the disassembly process until the tunnel machine 100 reaches the end of the existing pipe OP.

  The new pipe body NP is successively constructed as the tunnel T is dug. A new backfill material NBM is filled between the outer peripheral surface of the tubular body NP and the inner peripheral surface of the tunnel T.

  The filling amount of the backfill material NBM increases as the inner diameter of the tunnel T is larger than the outer diameter of the new tubular body NP. Therefore, it is preferable that the difference between the inner diameter of the tunnel T and the outer diameter of the new tubular body NP is small. On the other hand, when excavating the ground outside the existing pipe OP and the backfill material BM to advance the tunnel T, the inner diameter of the tunnel T is at least the cutter bit 21 with respect to the outer diameter of the existing pipe OP. The thickness increases. For this reason, when the new pipe body NP is constructed with an outer diameter substantially equal to the outer diameter of the existing pipe OP, it is preferable to reduce the thickness of the cutter bit 21.

  In the tunnel machine 100, as described above, the motor 30 passes through the space inside the virtual extension inner peripheral surface of the cutter bit 21, so that the cutter bit 21 can have the necessary minimum thickness. Therefore, when the new pipe body NP is constructed with an outer diameter substantially equal to the outer diameter of the existing pipe OP, the difference between the inner diameter of the tunnel T and the outer diameter of the new pipe body NP can be reduced, and The filling amount of the material NBM can be reduced.

  According to this embodiment described above, the following operational effects are exhibited.

  In the tunnel machine 100, the motor 30 is arranged inside the virtual extension inner peripheral surface of the cutter bit 21. Therefore, when excavating the tunnel T, the motor 30 passes through the space inside the virtual extension inner peripheral surface of the cutter bit 21. Therefore, the space through which the motor 30 passes can be formed by disassembling the existing pipe OP. As a result, the thickness of the cutter bit 21 in the radial direction of the tunnel T can be reduced, and the amount of excavation can be reduced.

  The motor 30 is arranged behind the casing 22. Therefore, it is possible to prevent the device for disassembling the existing pipe OP and the motor 30 from interfering with each other inside the casing 22. Therefore, the disassembly workability can be improved.

  The motor 30 is attached to the protrusion 12 that protrudes from the inner peripheral surface of the body 10 to the inside of the virtual extension inner peripheral surface. Therefore, the motor 30 can be arranged inside the virtual extension inner peripheral surface. Therefore, the cutter bit 21 can be made thinner, and the amount of excavation can be further reduced.

  The tunnel machine 100 includes a seal 50 provided on the tubular body 20 and in close contact with the backing material BM or the segment ring SR remaining after excavation by the cutter bit 21. Therefore, the seal 50 can close (seal) the casing 22 and the remaining backing material BM or the segment ring SR, and the muddy water of the natural ground can be prevented from flowing into the tubular body 20 and the body 10. Can be prevented.

  The seal 50 is in close contact with the backing material BM or the segment ring SR remaining after excavation by the cutter bit 21 and can switch between a state in which the closing function is effective and a state in which the closing function is released. Therefore, the degree of adhesion of the seal 50 can be changed according to the amount of muddy water in the ground. Therefore, the wear of the seal 50 due to the rotation of the tubular body 20 can be reduced while preventing the muddy water from flowing into the tubular body 20 and the body 10.

<Second Embodiment>
Next, with reference to FIG. 4, a tunnel machine 200 according to a second embodiment of the present invention will be described. Hereinafter, points different from the first embodiment will be mainly described, and the same or corresponding configurations as the configurations described in the first embodiment will be denoted by the same reference numerals as those in the first embodiment in the drawings. The description is omitted.

  The tunnel machine 200 further includes a partition 260 provided inside the body 10. The partition wall 260 is fixed to the protrusion 12, and forms a chamber 261 that receives the existing pipe OP together with the tubular body 20. The existing pipe OP is disassembled inside the chamber 261. A space 264 for constructing a new pipe body NP is separated from the chamber 261 by a partition wall 260.

  In the method for excavating the tunnel T using the tunnel excavator 200, the partition wall 262 is formed at the end of the existing pipe OP in the excavation direction, and the partition walls 260, 262, the existing pipe OP, and the tubular body 20 form the air chamber 263. It is formed. By supplying air to the air chamber 263 using an air supply unit (not shown), the pressure in the air chamber 263 can be increased. As a result, it is possible to prevent the muddy water in the ground from flowing into the tubular body 20, and it is possible to omit the seal 50 (see FIG. 3) of the first embodiment.

  Note that the seal 50 (see FIG. 3) of the first embodiment may be provided in the tunnel machine 200, and in this case, it is possible to more reliably prevent the muddy water of the natural ground from flowing into the tubular body 20. be able to.

  In the method of excavating the tunnel T using the tunnel excavator 200, it is preferable that the dismantling work of the existing pipe OP is performed remotely. In this case, the frequency with which the worker enters and leaves the air chamber 263 can be reduced, and the state in which the pressure inside the air chamber 263 is increased can be continued.

<Third Embodiment>
Next, with reference to FIG. 5, a tunnel machine 300 according to a third embodiment of the present invention will be described. Hereinafter, points different from the first embodiment will be mainly described, and the same or corresponding configurations as the configurations described in the first embodiment will be denoted by the same reference numerals as those in the first embodiment in the drawings. The description is omitted.

  In the tunnel machine 100 (see FIG. 1) according to the first embodiment, the motor 30 is arranged inside the virtual extension inner peripheral surface of the cutter bit 21, so that the motor 30 is installed between the existing pipe OP and the tunnel T. The total length of the tunnel machine 100 is longer than that in the case where the tunnel machine 100 is arranged. Therefore, when the existing pipe OP is curved and constructed, the cutter bit 21 may hit the existing pipe OP and it may not be possible to excavate the outside of the existing pipe OP.

  The tunnel machine 300 according to the present embodiment is configured to be capable of being folded in the middle. Therefore, the tunnel machine 300 can be bent according to the bending of the existing pipe OP, and the tunnel T can be dug along the existing pipe OP that is curved and constructed. Hereinafter, the structure of the tunnel machine 300 will be specifically described.

  In the tunnel machine 300, the body 310 includes a front body 313 on which the tubular body 20 is mounted, and a rear body 314 connected to the front body 313. The front end 314a of the rear body 314 is inserted into the rear end 313a of the front body 313.

  The outer peripheral surface of the front end 314a of the rear body portion 314 is formed in an arc shape so as to be convex outward in the radial direction of the tunnel T. Therefore, even when the rear body portion 314 is inclined with respect to the front body portion 313, contact between the outer peripheral surface of the front end 314a of the rear body portion 314 and the inner peripheral surface of the rear end 313a of the front body portion 313 is maintained. To be done. That is, the front torso portion 313 and the rear torso portion 314 are connected so as to be tiltable, and the torso 310 can be bent in the middle.

  The middle folding of the body 310 is performed by a plurality of middle folding jacks 370 provided in the circumferential direction of the body 10. Each of the middle folding jacks 370 is provided across the front body portion 313 and the rear body portion 314. For example, in FIG. 5, the upper middle folding jack 370a contracts and the lower middle folding jack 370b extends, whereby the front end 313b of the front body portion 313 can be directed upward.

  A tail seal 315 is provided on the rear end side of the rear body 314 along the inner circumference of the body which is the rear body 314. The tail seal 315 closes the gap between the new segment ring NSR and the body that is the rear body 314 to prevent the earth and sand from flowing into the body 10 that is the rear body 314. In the third embodiment, the new segment ring NSR is assembled inside the rear barrel 314 between the propulsion jack 40 and the tail seal 315.

  As described above, in the tunnel machine 300, since the front body portion 313 and the rear body portion 314 are tiltably connected to each other, even when the existing pipe OP is curved and constructed, it follows the existing pipe OP. The tunnel T can be dug forward.

  Also in the tunnel machine 300, the motor 30 is arranged inside the virtual extension inner peripheral surface of the cutter bit 21, similarly to the tunnel machine 100. Therefore, the space through which the motor 30 passes can be formed by disassembling the existing pipe OP. Therefore, the thickness of the cutter bit 21 in the radial direction of the tunnel T can be reduced, and the amount of excavation can be reduced.

<Fourth Embodiment>
Next, with reference to FIG. 6, a tunnel machine 400 according to a fourth embodiment of the present invention will be described. Hereinafter, points different from the first embodiment will be mainly described, and the same or corresponding configurations as the configurations described in the first embodiment will be denoted by the same reference numerals as those in the first embodiment in the drawings. The description is omitted.

  The tunnel machine 400 differs from the tunnel machine 100 in that the outer diameter of the casing 422 of the tubular body 420 is smaller than the outer diameter of the cutter bit 421, and the casing 422 is included in the body 410. That is, the body 410 protects the casing 422 from the tightening of the ground due to the deformation of the tunnel T. Therefore, the torque required to rotate the tubular body 420 can be reduced.

  Also in the tunnel machine 400, the motor 30 is arranged inside the virtual extension inner peripheral surface of the cutter bit 421 as in the tunnel machine 100. Therefore, the space through which the motor 30 passes can be formed by disassembling the existing pipe OP. Therefore, as compared with the case where the motor 30 is arranged between the existing pipe OP and the tunnel T, the thickness of the cutter bit 421 in the radial direction of the tunnel T can be reduced, and the amount of excavation can be reduced.

  Although the embodiment of the present invention has been described above, the above embodiment merely shows a part of the application example of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  In each of the above-described embodiments, the cutter bits 21, 421 excavate the rock mass and the backfill material BM outside the existing pipe OP, but only the rock mass may be excavated, or only the backfill material BM is excavated. May be. That is, the cutter bits 21, 421 may be formed so as to excavate the outside of the existing pipe OP. Further, the cutter bits 21, 421 may excavate a part of the existing pipe OP in the circumferential direction.

  In the tunnel machine 100, the seal 50 (see FIG. 3) is in close contact with the backing material BM remaining after excavation by the cutter bit 21, but the present invention is not limited to this form. The seal 50 may be in close contact with the ground remaining after excavation by the cutter bit 21, or in close contact with the existing pipe OP. That is, the seal 50 may be formed so as to be in close contact with the outside of the existing pipe OP and close the space between the tubular body 20 and the outside of the existing pipe OP.

  In the tunnel machine 100, 200, 300, 400, the entire motor 30 is arranged inside the virtual extension inner peripheral surface of the cutter bit 21, but according to the present invention, a part of the motor 30 is virtual of the cutter bit 21. It may be arranged inside the extended inner peripheral surface.

100, 200, 300, 400 ... Tunnel excavator 10 ... Body 20 ... Cylindrical body 21 ... Cutter bit (excavation part)
22 ... Casing 30 ... Motor (drive unit)
50 ... Seal 260 ... Partition 261 ... Chamber 310 ... Body 313 ... Front body 314 ... Rear body 410 ... Body 420 ... Cylindrical body 421 ... Cutter bit (excavation section)
422 ... Casing BM ... Backing material NBM ... Backing material NP ... New pipe OP ... Existing pipe T ... Tunnel

Claims (9)

A tunnel machine that excavates a tunnel along an existing pipe,
A body supporting the inner wall surface of the tunnel,
A tubular body mounted on the body, having a digging portion for digging the outside of the existing pipe, and including the existing pipe.
A drive unit that rotates the tubular body with respect to the body,
The tunnel excavator, wherein the drive unit is arranged inside a virtual extension inner peripheral surface obtained by extending the inner peripheral surface of the excavating unit rearward along the axial direction of the tunnel. The tubular body further has a casing in which the excavation portion is provided at a tip end portion and extends along an axial direction of the tunnel,
The tunnel excavator according to claim 1, wherein the drive unit is disposed behind the casing. The casing is contained in the body,
The tunnel excavator according to claim 2. The tunnel excavator according to any one of claims 1 to 3, wherein the drive unit is attached to a protrusion that protrudes from the inner peripheral surface of the body to the inside of the virtual extension inner peripheral surface. The tunnel excavator according to any one of claims 1 to 4, further comprising a seal that is provided on the tubular body and closes a gap between the tubular body and an outer side of the existing pipe. The tunnel machine according to claim 5, wherein the seal is switchable between a state in which the seal is in close contact with the outside of the existing pipe and a state in which the seal is in close contact with the outside of the existing pipe. The tunnel excavator according to any one of claims 1 to 6, further comprising a partition wall provided inside the body to form a chamber that receives the existing pipe together with the tubular body. The body includes a front body portion to which the tubular body is attached, and a rear body portion connected to the front body portion,
The tunnel machine according to any one of claims 1 to 7, wherein the rear trunk is tiltable with respect to the front trunk. A tunnel excavation method for excavating a tunnel along an existing pipe using a tunnel excavator,
The tunnel machine includes a body supporting an inner wall surface of the tunnel, a tubular body mounted on the body and having an excavation portion for excavating the outside of the existing pipe, and the tubular body including the existing pipe. A drive unit for rotating a body with respect to the body, the drive unit being disposed inside a virtual extension inner peripheral surface that extends the inner peripheral surface of the excavating section rearward along the axial direction of the tunnel. Has been done,
The tunnel excavation method is
By excavating the outside of the existing pipe and inserting the existing pipe into the inside of the tubular body by rotating the tubular body using the drive unit and advancing the tubular body, and a digging step,
A tunnel excavation method, comprising: a disassembling step of disassembling the existing pipe inside the tubular body.

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