JPH1113389A - Excavator for implementing the same method as propulsion by shield jack - Google Patents

Abstract

(57) [Summary] [Problem] To excavate mainly by excavating only a shield jack between a segment wall and a support assembled behind a machine body in an excavator such as a shield excavator or a tunnel excavator for rock mass. An excavator having a simple structure can easily prevent and correct rolling when it is performed. SOLUTION: A base end of each shield jack 11 is swingably attached via a spherical bearing 13 to a ring girder 12 fixed along an inner peripheral wall of a rear trunk 3, and is separately provided along a rear end of the inner peripheral wall. While fixing the ring girder 14 of
An oval hole 15 is formed in the ring girder 14 in the vicinity of the tip of each shield jack 11 in the circumferential direction, and the tip of the main body of the shield jack 11 at a position corresponding to each oval hole 15 is loosely inserted. A rolling support jack 18 is interposed between the distal end of each shield jack 11 and the ring girder 14 so that the distal end of the shield jack 11 can be rotationally moved in the opposite direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield type and an open type tunnel excavator for rock excavation, and a cutter disk (also referred to as a cutter head) having a cylindrical shield and generally referred to as a shield excavator. The present invention relates to an excavator for excavating a tunnel, such as an excavator equipped with an excavator. More specifically, the present invention relates to an excavation method using a shield jack provided at a rear end of an excavator body and an excavator for performing the method.

[0002]

2. Description of the Related Art The above-described shield machine is usually used for tunnel excavation on ordinary ground or soft ground.
As shown in FIG. 7, there is a type in which the cutter bit of the cutter disk 35 is replaced with a cutter roller 36 corresponding to the rock to enable excavation on the rock. Shield machine 31
As is well known, a method is known in which an erector 33 for assembling a segment is provided at the rear part, a segment wall S is constructed behind the machine main body 32, the segment wall S is used as a reaction force receiver, and a shield jack 34 is pressed against the propulsion. Therefore, unlike the tunnel excavator, there is no gripper mechanism for pressing against the excavated tunnel pit wall to receive the reaction force of the machine body 32. For this reason, the machine body may roll in the opposite direction to the rotation of the cutter disk due to the rotational force of the cutter disk.In this case, the cutter disk is rotated in the opposite direction to cancel the rolling. Therefore, the cutter disk is provided with two inlets on both sides of the cutter bit so that the excavated earth and sand can be taken into the disk regardless of the direction of rotation.

On the other hand, a tunnel excavator (see FIG. 1) is provided with a gripper mechanism and receives a reaction force of the machine body by pressing against a tunnel well wall, so that rolling does not occur. The disc usually only needs to rotate in one direction.

[0004] Japanese Patent Publication No. Hei 7-35914 is a prior art document. In the excavator described in the publication, the tip side of the shield jack can be swung in the radial direction of the tunnel, and the tip of the shield jack (spreader) is used. ) Is pressed against the segment wall to prevent the segment piece from moving in the radial direction and preventing the spreader from coming off the end face of the segment piece. In other words,
The shield jack of the excavator described in the publication cannot generate a force opposing the torque reaction force against the rotation of the cutter disk, and therefore cannot bear the torque reaction force.

[0005]

However, when the above-described conventional excavator is used to excavate a tunnel particularly in a rocky ground, there are the following problems to be solved.

[0006] In the case of a shield machine, the proportion of the double intake hole for the excavated earth and sand in the cutter disk increases, which complicates the structure, and the layout of the cutter disk is restricted by the mounting position of the cutter bit.

In the case of a tunnel machine, ground (ground)
If it is not good, it will support the entire circumference of the tunnel wall including the construction of the segment wall, the gripper mechanism does not work, and the excavation work is performed by the shield jack and the support method. When rolling occurs, there is no longer a way to correct the rolling.

[0008] The excavator described in the above publication has no function of preventing a torque reaction force when the cutter disk rotates. Further, the segment wall against which the shield jack is pressed ensures thrust not on the segment wall assembled in the rear part of the machine body but on the segment wall directly assembled on the pit wall behind the machine body.

The present invention has been made in view of the above points, and is mainly used for excavators such as a shield excavator and a tunnel excavator for rocks, which are shielded between a segment wall or a support assembled behind the machine body. Provided is an excavator which can easily prevent and correct rolling when excavating by propulsion of a jack alone and has a simple structure, and a method of excavating using a shield jack provided at a rear end of the excavator body. It is intended to be.

[0010]

In order to achieve the above object, a propulsion method using a shield jack according to the present invention (Claim 1) includes the steps of: a) rotating a cutter disk provided at a front end while rotating a cutter disk provided at a front end thereof; In an excavator such as a tunnel excavator or a shield excavator for excavating a tunnel by pushing a spreader at a rear end against a segment wall or a reaction receiving member to be constructed and extending a shield jack to propell the machine body, A method of propelling the machine body by jacks, b) arranging a plurality of bases of the shield jacks at intervals in a circumferential direction of the machine body and swingably swinging in a circumferential direction with respect to the machine body; The tip side of the jack is inclined in advance, and c) the cutter disc is turned to the machine body by extending all the shield jacks simultaneously. This is to generate a torque reaction force against the rolling (force in the direction opposite to the rotating force of the cutter disk).

According to the excavating method of the present invention having the above-described structure, the excavator does not have a torque reaction force supporting mechanism such as a gripper mechanism, or the excavator does not function sufficiently due to poor ground or the like. In the case where the excavator does not move, the tip side of all shield jacks for excavator propulsion is swung (inclined) in the direction opposite to the rotation of the cutter disk in advance, and in this state the cylinder is mounted on the segment wall assembled behind the excavator. By pushing the rod end to extend all shield jacks at the same time, eccentric thrust acts on the segment wall in the rotation direction of the cutter disk,
As the reaction force, the tunnel excavator applies a forward propulsion force (a force in the direction opposite to the arrow L in FIGS. 3 and 6) and a circumferential component force in the same direction as the cutter disk rotation direction (FIGS. 3 and 3). 6
Respectively, the excavator is excavated by the cutter disc in such a way as to negate the force that would cause the body to be turned in the opposite direction.

Further, by adjusting the inclination (oscillation) angle of the excavator on the tip end side of each shield jack with respect to the axial direction of the excavator, the magnitude of the torque reaction force against the cutter disk can be changed. Rolling of the excavator can be prevented or corrected depending on the condition.

[0013] Furthermore, by enabling the rolling correction by the shield jack, the operation of rotating the cutter disc by rotating the cutter disk in the conventional direction, which has been conventionally performed by the shield excavator, is no longer necessary. In addition to the above, the gripper mechanism does not function for supporting the entire circumference when the ground is defective, and the rolling which has been impossible with a tunnel excavator can be corrected.

An excavator (claim 2) for carrying out the method of claim 1 comprises: A) a cutter disk rotatably provided at a front end, and a plurality of shield jacks at a rear end spaced apart in a circumferential direction. For tunnel excavators such as tunnel excavators and shield excavators that are arranged backward, B)
The base end of each of the shield jacks is swingably attached via a spherical bearing to a ring girder fixed along the inner peripheral wall of the machine body, and C) another is provided along the inner peripheral wall at the rear end of the machine body. A ring girder is fixedly mounted, and D) an oblong hole is formed in the circumferential direction in the vicinity of the end of each of the shield jacks of the ring girder, and E) a tip of the body of the shield jack at a position corresponding to each of the oval holes. And F) a rolling support jack is interposed between the tip of each shield jack and the ring girder at the rear end so that the tip of the shield jack can be rotated.

According to the excavator of the present invention having the above structure, by extending the rolling support jack, the tip end of the main body of the shield jack is rotated in the circumferential direction by using the inner peripheral wall of the oblong hole as a guide. The tip side of the jack is inclined at a predetermined angle with respect to the axis of the excavator. Therefore,
In this state, the tip of the cylinder rod is pressed against the segment wall assembled behind the excavator, and all shield jacks are extended at the same time. The forward propulsion force is applied to the tunnel excavator as the force (Fig. 3
Excavation because a force in the direction opposite to the arrow L in FIG. 6) and a component in the circumferential direction in the same direction as the rotation direction of the cutter disc (force in the direction opposite to the arrow M in FIGS. 3 and 6) act respectively. The machine is dug by the cutter disc to counteract the force that would cause the body to turn in the opposite direction.

In addition, since the rolling correction by the shield jack is enabled, the operation of rotating the cutter disk in the direction opposite to the direction of rotation of the cutter disk, which has been conventionally performed by the shield excavator, becomes unnecessary. (Excavation debris) It is only necessary to provide the intake port in only one direction, so that the structure of the cutter disk is simplified and the durability is improved.

Alternatively, as in the excavator according to the third aspect, A) a cutter disk is rotatably provided at a front end, and a plurality of shield jacks are arranged rearwardly at intervals at a rear end in a circumferential direction. B) In a tunnel excavator such as a tunnel excavator or a shield excavator, the base end of each of the shield jacks is swung through a spherical bearing with respect to a ring girder fixed along the inner peripheral wall of the machine body. C ') A swivel ring is arranged rotatably in the circumferential direction along the inner peripheral wall at the rear end of the machine body, and D') at a position corresponding to the tip of each shield jack of the swivel ring. Openings slightly larger than the outer diameter of the shield jack main body are opened at intervals in the circumferential direction, E ') Loosely insert the ends of the main body of the shield jack at positions corresponding to the respective openings, and fix the slewing ring to a predetermined position. angle A driving device may be provided so as to be capable of reciprocating rotation within the range described above.

According to the excavator of the present invention having the above-described structure, the tip of the shield jack is rotated together with the swivel ring by rotating the swivel ring by the driving device by a predetermined angle in the direction opposite to the direction of rotation of the cutter disk. The tip of the shield jack is inclined at a predetermined angle with respect to the axis of the excavator. Therefore, similarly to the excavator of claim 2, the tip of the cylinder rod is pressed against the segment wall assembled behind the excavator in the above-described state, and all the shield jacks are simultaneously extended, so that the cutter disk is attached to the segment wall. An eccentric thrust acts in the rotation direction, and as a reaction force, a forward propulsion force (a force in the direction opposite to the arrow L in FIGS. 3 and 6) and a rotation in the same direction as the cutter disk rotation direction are applied to the tunnel excavator. Circumferential component force (Fig. 3
The excavator is excavated by the cutter disc so as to counteract the force that would cause the body to be turned in the opposite direction, as each force (opposite direction of arrow M in FIG. 6) acts.

Further, in the excavator according to the third aspect, the angle of rotation of the swing ring from the normal position to the direction opposite to the rotation of the cutter disk is changed, so that the tip of the shield jack is inclined with respect to the excavator axis. Is kept constant, the magnitude of the torque reaction force on the cutter disk can be adjusted according to the state of the ground. Further, all the shield jacks can be inclined by the same angle with respect to the excavator axis by rotation of the swivel ring, which is advantageous in operation. As in the case of the excavator according to the second aspect, the magnitude of the torque reaction force against the cutter disk can be adjusted by adjusting the thrust of the shield jack. In, by changing the inclination direction of the tip end of the shield jack and changing the thrust of the shield jack, the torque reaction force can be accurately adjusted according to the state of the ground. Other advantages (operations) are common to those of the second aspect.

According to a fourth aspect of the present invention, in the excavator according to the second or third aspect, it is preferable that a spreader is swingably attached to a tip of a cylinder rod of each of the shield jacks via a spherical bearing.

According to the excavator of the present invention, even if the angle of inclination of the tip end of the shield jack changes, the entire surface of the spreader can always be pressed against the end face of the segment wall, and the propulsion force of the excavator can be reduced. The torque reaction force can be exerted accurately.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an excavator and a method of excavating a shield jack according to the present invention.

FIG. 1 is a central longitudinal sectional view showing a general tunnel excavator, FIGS. 2 and 3 are perspective views showing a main part of a rear part of the tunnel excavator according to an embodiment of the present invention, and FIG. FIG. 3 shows a rolling correction state.

First, the present embodiment is applied to a tunnel excavator 1. As shown in FIG. 1, the tunnel excavator 1 has a main body 1a divided into a front body 2 and a rear body 3, and one body (2 Or 3), the other body (3 or 2) is connected via a plurality of thrust jacks 4 so as to be relatively approachable / separable. A cutter disk 5 provided with a rock cutter 5a for rock excavation is rotatably disposed at the tip of the front body 2, and the cutter disk 5 is moved in one direction by a plurality of driving devices 6 via a speed reduction mechanism 6a. (In the example, counterclockwise). A front gripper 7 is provided on the front body 2, and a main gripper 8 is provided on the rear body 3 so as to be able to freely enter and exit from the outer peripheral surface of the shield. An erector turning ring 9 is provided in the vicinity of the rear end of the rear trunk 3 so as to be rotatable in a circumferential direction, and the whirl ring 9 is provided with an erector 10.

In this example, as shown in FIGS. 2 and 3,
A plurality of shield jacks 11 are mounted on the tunnel excavator 1 as follows. That is, the ring girder 12 is fixedly provided at a rear portion of the rear trunk 3 inside the cylindrical shield 3a. In the ring girder 12, the base ends of the shield jack 11 are arranged at equal intervals in the circumferential direction, and are mounted to be swingable in all directions via a spherical bearing 13 as shown in FIG. . Another ring girder 14 is fixedly provided at the rear end in the shield 3a. The ring girder 14 has a flange 14a bent at a right angle forward along the inner peripheral edge. An oval hole (an oval hole) 15 is provided near the tip of each shield jack 11 of the ring girder 14.
1 are provided at equal intervals in the circumferential direction in a counterclockwise direction from a position where the extruder 1 extends in the front and rear direction (axial direction) of the excavator 1 in a backward and parallel direction. The distal end of the main body 11a of each shield jack 11 is loosely inserted into the corresponding one of the elliptical holes 15 so that the inner peripheral surface of the elliptical hole 15 serves as a guide so as to be slidably rotatable. . From the opening at the tip of the body 11a of the shield jack 11, the cylinder rod 1
1c protrudes rearward so as to be able to freely move in and out, but a spreader 16 is mounted at the tip of the cylinder rod 11c via a spherical bearing 17 so as to be swingable in all directions, as shown in FIG.

The inner flange 14 of the ring girder 14
a, rolling support jacks 1 at equal intervals in the circumferential direction;
8 is pivotally connected via a U-shaped bracket 19, and a cylinder rod 18 c of the jack 18 is pivotally connected via a U-shaped bracket 29 to the tip of the main body 11 a of each shield jack 11. . As a result, each jack 18 is arranged with its tip facing counterclockwise with respect to the ring girder 14.

As described above, the tunnel excavator 1 according to the present embodiment is configured. An example of the excavation mode of the tunnel excavator 1 will be described together with the excavation method using the shield jack 11.

In FIG. 1, in a state where the thrust jack 4 is contracted to bring the rear trunk 3 closer to the front trunk 2, the rear end shield jack 11 is extended to receive a reaction force on the segment wall constructed rearward. The tunnel is excavated by propelling the tunnel excavator 1. At this time, the cutter disk 5 at the tip is rotating counterclockwise. As shown in FIG. 2, the rolling support jacks 18 are contracted, and the shield jacks 11 are arranged parallel to the axial direction of the excavator 1, so that the excavator 1 receives a thrust L ′ parallel to the axial direction. Drilled forward.

At the time of the above-mentioned excavation work, if the tunnel excavator 1 rolls clockwise under the influence of the rotational force of the cutter disk 5 or there is a possibility of rolling, the tunnel jacking machine 1 is turned off as follows. use. That is, as shown in FIG. 3, all the rolling support jacks 18 are extended, and the tip side of each shield jack 11 is rotated clockwise along the oblong hole 15.
Here, the cylinder rod 11c is extended, and the tip spreader 16 is pressed against the end face of the cylindrical segment wall S. The spreader 16 swings via the spherical bearing 17, and the entire outer surface of the spreader 16 abuts on the end face of the segment wall S so as to be in close contact therewith. By extending the cylinder rod 11c while rotating the cutter disk 5 in this state, a thrust L ′ eccentric in the clockwise direction as viewed from the rear is generated, and a circumferential component force in the counterclockwise direction as viewed from the rear. Under the reaction force of M, the excavator 1 moves forward by the reaction force of the axial thrust L so as to cancel the force of the excavator 1 being turned in the opposite direction by the rotation of the cutter disk 5, and excavates the tunnel. The work is performed.

After the cylinder rod 11c is extended to the maximum, a space is created between the cylinder rod 11c and the assembled segment wall S by retracting the cylinder rod 11c. Assemble the cylinder rod 11c
The tunnel is excavated by repeating the above series of operations of extending the tunnel.

FIGS. 5 and 6 are perspective views showing a main part of a rear portion of a tunnel excavator according to another embodiment of the present invention. FIG. 5 is a partially cutaway view showing a normal excavation state. Reference numeral 6 denotes a rolling correction state.

What is the difference between the tunnel excavator 1 'of the present embodiment and the above embodiment? The points are as follows. That is, the turning ring 20 is provided instead of the ring girder 14 on the rear end side. The position at which it is provided does not change, but a pair of front and rear rails 21 are fixedly provided at predetermined intervals along the rear end of the inner peripheral wall of the shield 3a, and the outer peripheral edge of the turning ring 20 having an inverted L-shaped cross section is fixed. It is slidably fitted between the rails 21. Also, the inner peripheral flange 2 of the swing ring 20
A rotating ring gear 22 is fixed in the circumferential direction along the lower side 0a, a driving motor (hydraulic motor in this example) 23 is mounted on the inner peripheral wall of the shield 3a, and a drive attached to a driving shaft of the driving motor 23. The gear 23a is meshed with the ring gear 22. By rotating the drive motor 23 with this configuration, the turning ring 20 rotates. In addition, the swing ring 20 has a main body 1 corresponding to each shield jack 11.
Openings 20b slightly larger in diameter than 1a are opened at equal intervals in the circumferential direction, and the distal end of the main body 11a of the shield jack 11 at the corresponding position is loosely inserted into each opening 20b.

Accordingly, by turning the drive motor 23 by a predetermined number of rotations from a state in which each shield jack 11 faces rearward in parallel with the axial direction of the excavator 1 '(see FIG. 5), the swing ring 20 is rotated by a predetermined angle. As a result of the rotation, the distal ends of all the shield jacks 11 are simultaneously inclined clockwise around the base spherical bearing 13 (see FIG. 6). This state is the same as the state in which the rolling support jacks 18 are extended in the first embodiment (see FIG. 3).
Therefore, in this state (FIG. 6), the cutter disk 5
While rotating the cylinder rod 11c, a thrust L ′ eccentric in a clockwise direction as viewed from behind is generated, and a circumferential component M in a counterclockwise direction as viewed from behind is generated.
The excavator 1 ′ moves forward by the reaction force of the axial thrust L so as to cancel the force of the excavator 1 ′ being turned in the opposite direction by the rotation of the cutter disk 5, Excavation work is performed.

In the tunnel excavator 1 'of this embodiment, the turning ring 20 is set at the normal position (the shield jack 11).
Is parallel to the axis of the excavator 1 ′), the angle of rotation of the cutter jack 5 in the direction opposite to the rotation of the cutter disc 5 is changed, so that the inclination angle of the tip end of the shield jack 11 with respect to the axis of the excavator is kept constant. Therefore, the magnitude of the torque reaction force against the cutter disk 5 can be adjusted not only by changing the thrust of the shield jack 11 but also by changing the inclination angle of the shield jack 11 according to the state of the ground. Further, the point that all the shield jacks 11 can be tilted by the same angle with respect to the axis of the excavator only by rotating the revolving ring 20 is advantageous as compared with the first embodiment. The same components as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted.

Although two embodiments of the present invention have been described above, the present invention can be implemented as follows.

(A) The present invention can be applied not only to the shield type but also to an open type tunnel excavator and also to a shield type excavator. It is mainly used for tunnel excavation on rock, but it goes without saying that it can also be used for tunnel excavation on soft ground.

(B) The base end of the shield jack 11 is attached to the ring girder 12 instead of the spherical bearing 13.
A pivot pin (not shown) can be used.

[0038]

As described above, the excavating method and the excavator using the shield jack according to the present invention have the following excellent effects.

(1) According to the excavating method of the present invention, when rolling occurs due to poor ground or the like, the tip sides of all shield jacks for excavating the excavator are inclined in advance, and the excavator is mounted on the segment wall behind the excavator. By pushing the tip of the cylinder rod and extending all shield jacks simultaneously, the force to propel the tunnel excavator forward and the circumferential component in the same direction as the rotation direction of the cutter disk are applied, respectively. The machine can be excavated to counteract the force by which the body is turned by the cutter disc in the opposite direction.

The magnitude of the torque reaction force on the cutter disk can be changed by adjusting the inclination (oscillation) angle of the tip end of each shield jack with respect to the axial direction of the excavator. In addition, by enabling rolling correction with a shield jack, the operation of rotating the cutter disk in the reverse direction, which was conventionally performed with a shield excavator, is not required, and the operation is simplified. If the mountain is bad, the gripper mechanism will not work to support the entire circumference, and it will be possible to correct the rolling that was impossible with a tunnel excavator.

(2) In the excavator according to the second aspect, the excavation method according to the first aspect can be reliably performed, and the tip of the shield jack is tilted in the circumferential direction using the inner peripheral wall of the oblong hole as a guide. Can be. In addition, since the rolling correction by the shield jack is enabled, the operation of rotating the cutter disk in the reverse direction, which has been conventionally performed by the shield excavator, becomes unnecessary. ) The intake port needs to be provided only in one direction, so that the structure of the cutter disk is simplified and the durability is improved.

(3) In the excavator according to the third aspect, similarly to the excavator according to the second aspect, the tip ends of all the shield jacks for excavating the excavator are inclined in advance and the cylinder rod tip is attached to the segment wall behind the excavator. By pressing all of the shield jacks simultaneously, the excavator can be excavated so as to cancel the force of the main body being turned in the opposite direction by the rotation of the cutter disk.

By changing the rotation angle of the swing ring, the inclination angle of the tip end of the shield jack with respect to the axis of the excavator can be kept constant. Can be adjusted. Furthermore, all the shield jacks can be tilted by the same angle with respect to the excavator axis by rotating the swivel ring, which is advantageous in operation.

(4) In the excavator according to the fourth aspect, the entire surface of the spreader can be constantly pressed against the end face of the segment wall even if the inclination angle of the tip end of the shield jack changes, so that the propulsion force of the excavator And the torque reaction force can be accurately exhibited.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional view showing a general tunnel excavator as an example to which the present invention is applied.

FIG. 2 is a perspective view showing a main part of a rear portion of the tunnel excavator according to the embodiment of the present invention, and shows a normal excavation state.

FIG. 3 is a perspective view showing a main part of a rear part of the tunnel excavator in FIG. 2 in a rolling correction state.

FIG. 4 (a) is a partial cross-sectional view schematically showing a base end mounting portion of the shield jack 11, and FIG. 4 (b) is a portion schematically showing a mounting portion of a spreader 16 at a distal end of the shield jack 11. It is sectional drawing.

FIG. 5 is a perspective view, partially cut away, showing a main part of a rear portion of a tunnel excavator according to another embodiment of the present invention, showing a normal excavation state.

6 is a perspective view showing a main part of a rear portion of the tunnel excavator in FIG. 5 in a rolling correction state.

FIG. 7 is a central longitudinal sectional view showing a general shield machine.

[Explanation of symbols]

 1.1 'Tunnel excavator 1a Machine body 2 Front trunk 3 Rear trunk 5 Cutter disk 10 Elector 11 Shield jack 11c Cylinder rod 12.14 Ring girder 13.17 Spherical bearing 15 Oval hole 16 Spreader 18 Rolling support jack 20 Swirl ring 20b opening 21 rail 22 turning ring gear 23 drive motor (drive device)

Claims (4)

[Claims] 1. While rotating a cutter disk provided at a front end, a spreader at a rear end is pressed against a segment wall or a reaction force receiving member constructed at the rear of the machine main body, and a shield jack is extended to propel the machine main body. In an excavator such as a tunnel excavator or a shield machine for excavating a tunnel, a method of propelling a machine body by the shield jack, wherein a base end of the shield jack is spaced in a circumferential direction of the machine body, and A plurality of shield jacks are arranged so that they can swing freely in the circumferential direction with respect to the machine body, the tip side of all shield jacks is inclined in advance, and all shield jacks are extended at the same time. A propulsion method using a shield jack, which generates a reaction force. 2. A tunnel excavator or a shield excavator having a cutter disk rotatably provided at a front end thereof and a plurality of shield jacks arranged rearwardly at a rear end thereof at intervals in a circumferential direction. In the excavator, the base end of each of the shield jacks is swingably attached to a ring girder fixed along the inner peripheral wall of the machine body via a spherical bearing, along the inner peripheral wall of the rear end of the machine body. Along with fixing another ring girder, an oval hole is opened in the circumferential direction near the tip of each shield jack of the ring girder, and the tip of the main body of the shield jack at a position corresponding to each oval hole is formed. A rolling support jack is inserted between the tip of each shield jack and the ring girder at the rear end so that each can be loosely inserted and the tip of the shield jack can be rotated. An excavator characterized by interposing. 3. A tunnel excavator or a shield excavator having a cutter disk rotatably provided at a front end thereof and a plurality of shield jacks arranged rearwardly at a rear end thereof at intervals in a circumferential direction. In the excavator, the base end of each of the shield jacks is swingably attached to a ring girder fixed along the inner peripheral wall of the machine body via a spherical bearing, along the inner peripheral wall of the rear end of the machine body. The swing ring is arranged so as to be rotatable in the circumferential direction, and openings slightly larger than the outer diameter of the shield jack main body are opened at positions corresponding to the tips of the shield jacks of the swing ring at circumferential intervals. A drive device is provided so that the distal end of the main body of the shield jack at a position corresponding to each of the openings is loosely inserted, and the swivel ring can reciprocate within a predetermined angle range. An excavator, characterized in that: 4. The excavator according to claim 2, wherein a spreader is swingably attached to a tip of a cylinder rod of each of the shield jacks via a spherical bearing.