JP3143097B2 - Excavation equipment for shield machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a shield excavator, in which a protruding portion (for example, a back-filling device) on an outer periphery is advanced into a tunnel, so that extra excavation is performed outside a range excavated by a cutter disk. The present invention relates to an extra digging device.

[0002]

2. Description of the Related Art A shield excavator has a rotary cutter disk at the forefront, and excavates a tunnel in the ground by advancing with the thrust of a propulsion means while rotating the cutter disk. Since the cutter disc excavates by rotation,
In principle, a tunnel having a cross section of a circle or a combination of a plurality of circles is excavated.

[0003] However, the outer periphery of the shield machine is filled with a mortar or the like between the hole drilled slightly larger by the cutter disk and the outer periphery of the shield machine itself (or the outer periphery of the wall of the segment constructed behind). There is a portion that protrudes outward from the peripheral surface, for example, a so-called simultaneous back-filling injection device is attached. FIG. 5 is a front view of the shield machine 1 as viewed from the front (a part of which is shown in a cross section).
It protrudes outward from the outer periphery 3a which is a cylindrical surface. In order for such a projecting portion to move forward smoothly, the shield machine 1 needs to form a partially projecting space outside the tunnel where the cutter disk 2 (having a plurality of cutter bits 2a) excavates. Sometimes it is necessary to do extra mining.

[0004] As a conventional apparatus for performing such over-digging, Japanese Patent Laid-Open Publication No. Hei 10-37679 describes a face milling type rotary cutter. The device 40 shown in FIG. 6 is configured such that a rotary cutter 41 whose central axis of rotation is extended along the radial direction of the shield machine 1 is put on the outer periphery of the machine 1 as shown in FIG. It is rotated by a driving source 42 such as. Reference numeral 43 in the figure
Is a telescopic means such as a hydraulic cylinder, which adjusts the amount of protrusion of the cutter 41 on the outer periphery 3a of the cylindrical wall 3 in the excavator 1. Note that reference numeral 4 in the figure is the above-described simultaneous back-filling injection device.

In addition, in the shield machine, a copy cutter (not shown) is provided on a cutter disk because it is necessary to excavate a part of the side more when excavating a curved tunnel. Things are not uncommon. A copy cutter is a device that extends a tool radially outward from a main body portion on a cutter disk to take out a tool onto an outer periphery. If such a copy cutter is used well, it is possible in some cases to make a space for a protruding portion such as a simultaneous back-filling injection device extra.

[0006]

When starting excavation of a tunnel, a shield machine is generally started from the inside of a shaft A as shown in FIG. Before the start, the shield excavator 1 is put in such a shaft A, cuts a part (starting portion A2) of the retaining wall A1 while pushing the starting stand A4 backward, and the shield excavator 1 starts excavating ahead. It is. The shaft A is formed by digging a hole from the ground to a predetermined depth, constructing a retaining wall A1 on the inner surface, and setting the starting stand A to a required height.
4, the starting portion A2 of the retaining wall A1 is often constructed of a special high-strength concrete member (such as a member generally called "NOMST") in recent years. The member is to increase the strength of the wall sufficiently in order to save the labor and cost of soil improvement of the earth and sand ahead of the starting portion A2 by injecting a chemical solution or the like,
The excavator 1 is made of a high-strength hard material including carbon fiber or the like instead of not using a steel frame or the like that cannot be excavated. Such a shaft A is provided not only at the start portion but also at a junction between long tunnels.

Considering that recent shield excavators often have to excavate and advance such hard concrete members as described above when starting from a shaft, etc. Has the following deficiencies.

A) In the case of a face mill type rotary cutter as shown in FIG. 6, a drive source for rotating the cutter is required as described above, and it is necessary to supply a considerably large energy to the drive source. Disadvantageous in terms of cost. If the supplied energy is insufficient when excavating the above-mentioned hard concrete member, the efficiency of surplus digging will be reduced, and the speed of the shield excavator will have to be reduced, and the excavation efficiency itself will be reduced. The reason why such a large amount of energy is required for extra digging is that the rotary cutter has a large area and comes into contact with the tunnel wall (such as the above concrete members), so that the rotation resistance is high, and one side of the contact area It is considered that the rotary cutter must once push the cutting material (earth and sand or the concrete member) forward (forward in the traveling direction of the excavator) in the part of (1).

(B) With regard to the copy cutter provided on the cutter disk, since the arm extends outward from the main body portion on the cutter disk, it is difficult to provide structurally sufficient strength. This is because a large bending moment acts on the extended arm when the excavation resistance is applied to the tool that is extended on the outer periphery and extended to the outer periphery. Therefore, it is generally difficult to carry out extra dug by a copy cutter as described above when traveling through a hard and high excavation resistance portion such as the above-mentioned concrete member.

SUMMARY OF THE INVENTION An object of the present invention is to provide an extra excavation device for a shield machine capable of performing excavation reliably and smoothly without requiring a special driving force.

[0011]

According to a first aspect of the present invention, there is provided a shield excavating machine for excavating a tunnel machine with a tunnel wall accompanying advancement of the excavator by a propulsion means. The rotating blade rotates based on the speed difference between the rotating blades, and the rotation causes the cutting edge of the rotating blade to bite into the tunnel wall. The above-mentioned propulsion means is for advancing the shield machine and generally comprises a plurality of hydraulic cylinders and the like.

[0012] This over-digging device performs over-digging with a rotary tool (not limited to the face milling type shown in FIG. 6) as in the device of FIG. 6, but requires a dedicated drive source. Instead, the rotary blade is rotated based on a speed difference between the propulsion unit and the tunnel wall accompanying the advance of the excavator. The excavation speed of a shield excavator is generally 1-2 m /
min, and the speed difference accompanying the forward movement is also in agreement therewith and cannot be said to be a large value. However, the forward movement of the excavator is caused by the extremely large thrust (the size of the excavator) (Generally, one hundred to several thousand tons). Therefore, it is possible to apply an extremely large driving force (torque) to the rotary blade that rotates based on the speed difference accompanying the advance of the excavator as described above.

[0013] Even if the rotation speed is low, if a sufficiently large driving force can be applied, it is easy to make the cutting edge of the rotary blade bite into the tunnel wall to dug the outwardly projecting space. The same applies to the case where the tunnel wall is constituted by the above-mentioned hard / high-strength concrete member or the like. Therefore, as shown in FIG. 4, the shield machine excavates the concrete member at the time of starting or the like. In any case, the overdigging device can smoothly perform the necessary overdigging. The simultaneous back-filling injection device 4 shown in FIG.
It is needless to say that not only the over-digging for smoothly advancing the steel but also various types of over-digging for different purposes can be performed by the over-digging device.

According to a second aspect of the present invention, there is provided an overmining apparatus, wherein the rotary blade has a central axis of rotation along a circumferential direction of the shield machine and a plurality of saw-tooth-shaped projections around the rotary blade. A part which does not exceed is configured to be projected on the outer periphery of the shield machine, and the above-mentioned cutting edge is a traveling direction at a position of the serrated protrusion on the rotary blade, which is protruded on the outer periphery of the shield machine as described above. It is characterized in that it is formed at the front end portion (edge portion) at the rear. In addition, since the rotating blade only needs to be partially protruded on the outer periphery of the shield machine as described above at the time of use, the protrusion amount can be adjusted, or the entire rotating blade can be retracted under the outer periphery of the machine. Is also preferable.

As described above, such a rotary blade (for example, rotary blade 21 shown in FIG. 1) rotates based on a speed difference from a tunnel wall with the advance of the excavator, and the rotation causes the blade edge (for example, FIG. 1). The tip 23) can be cut into the tunnel wall. The details of the operation are as follows. That is, 1) the rotary blade always receives a rotational driving force in a fixed direction from a tunnel wall which moves relatively backward as the excavator advances. Since the central axis of rotation is along the circumferential direction of the shield machine and only a part that does not exceed the central axis is projected on the outer periphery of the shield machine, this rotary blade is relatively Due to the contact between the rearwardly moving tunnel wall and the serrated protrusion of the protruding portion, a force is applied in a certain direction (the direction in which the protruding portion moves rearward as shown in FIG. 1), and the tunnel wall rotates in that direction. Moreover, since the rotating blade has a plurality of serrated protrusions around it and is securely caught by the tunnel wall,
It receives strong force from the contacting tunnel wall with almost no slippage. The rotary cutter 41 shown in FIG.
Is different from the rotary blade in the excavator of the present invention in that, for example, it does not receive a rotational force in a specific direction depending on the contact with the tunnel wall because its entire circumference is on the outer circumference of the excavator.

2) Of the projections of the rotary blade, the cutting edge formed at the tip portion as described above surely bites into the tunnel wall with the rotation of the rotary blade. As described above, the rotary blade is rotated in a direction in which the portion protruding on the outer periphery of the excavator moves rearward due to the contact with the tunnel wall. Along with this, the saw-tooth-shaped projections around the rotary blade move from the inside of the excavator to the outside of the outer peripheral surface (that is, the inner surface of the tunnel wall). 1 (b) at the point 22a. Therefore, in this extra-drilling device in which the cutting edge is formed by providing a carbide tip at such a tip portion, the cutting edge can be reliably and smoothly cut into the inner surface of the tunnel wall based on the strong rotational force described above. Will be. In addition, the cutting edge always feeds the cutting material backward in the traveling direction, and does not push the cutting material toward the front unexcavated wall, so that the cutting can be performed smoothly.

According to a third aspect of the present invention, in order to widen the space dug by the rotary blade (that is, the excess dug area) in the circumferential direction of the tunnel, the extra excavation device according to the third aspect of the present invention is provided behind the rotary blade. (A front side), a cutting tool (a cutting tool) is fixedly arranged on the outer periphery of the shield machine.

When the shield machine 1 is started from inside the shaft A as shown in FIG. 4, for example, an annular packing (entrance packing) A3 is provided around the starting portion A2 of the retaining wall A1, and the packing A3 is provided. The excavator 1 is brought into close contact with the outer periphery. When the forefront part (cutter disk) of the excavator 1 penetrates the starting part A2, it is to prevent muddy water from entering the shaft A from the previous earth and sand part. In order to make such packing tightly adhere to the outer periphery of the excavator without any gap, the projecting portion on the outer periphery of the excavator such as the above-mentioned simultaneous backfilling device has an outer periphery 3a of the excavator 1 when viewed in the longitudinal direction as shown in FIG. It is often formed into a wide base with a smooth rise from the bottom. Therefore, it is often necessary to excavate a space extending in the circumferential direction of the tunnel in order to pass the projecting portion of such a shape into the overdigging device.

According to the third aspect of the present invention, since the cutting tool is fixedly arranged on the outer periphery of the shield machine behind the rotary blade as described above, the space extending in the circumferential direction as described above is reduced. It is suitable for forming. This is because, when the above-mentioned rotary blade is used, the rotary blade having a strong digging ability first forms a central central space portion having a height, and then a skirting field around the center (left and right). This is because it is efficient to cut off the part with a bite cutter. If the central portion is excavated first, there is also an advantage that the movement of the excavated waste by excavation of the bite cutter is smooth. The above-mentioned cutting tool is fixedly arranged on the outer periphery of the shield excavator so that a cut is made inside the tunnel wall, and as the excavator advances, the cutter relatively moves forward with respect to the tunnel wall. By doing so, a cutting speed is generated, so that the digging can be performed while scraping the tunnel wall.

According to a fourth aspect of the present invention, the biting cutter is disposed in a plurality of stages in the traveling direction of the shield machine, and the later one is provided with an increased width (circumferential dimension) of the excess cutting and a height (radius). (Dimensions in the direction).

In such an over-digging device, the base portion gradually widens in the circumferential direction while gradually reducing the amount of protrusion.
A space for passing the protruding portion having the shape as described above can be efficiently formed in the tunnel wall by overdigging. This is because it is rational to excavate the base part, whose height decreases as it moves away from the center part to the left and right, with a bite cutter arranged to gradually increase the width and reduce the height of the latter part. . Therefore, when the projecting portion on the outer periphery of the excavator is set in consideration of the adhesion with the packing for preventing inundation (entrance packing) in the starting shaft, the progress of the projecting portion is smoothened. It becomes possible to advance the shield machine while doing so.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG.
5 to FIG. FIG. 1 is a detailed view of the excavator 10, and FIG. 1A is a longitudinal sectional view showing the whole of the excavator 10 together with the front part (I part in FIG. 2) of the shield machine 1; Each figure of (b)-(e) is a function explanatory view about the rotary blade 21 in the extra-mining apparatus 10. FIG. 2 is a side view generally showing the shield machine 1, and particularly,
When starting from shaft A, the excavation device 10 is moved to the starting part A2.
This shows a state where the wall is being excavated. FIG. 3 is a side view showing a part of the shield machine 1, and FIG.
FIG. FIG. 4 is a longitudinal sectional view showing the structure of the starting shaft A together with the shield machine 1. Also, FIG.
It is the front view (part is shown in section) which looked at shield machine 1 from the front.

As shown in FIG. 4, the shield machine 1 has a rotary cutter disk 2 at the forefront and a cylindrical wall 3 at the rear thereof, and has a cylindrical shape as a whole.
A propulsion means (same as above) such as a hydraulic cylinder (not shown) is provided inside the cylindrical wall 3, whereby the starting frame A4 and the
A segment wall to be built later in the tunnel (not shown)
While pushing the end face backward, the tunnel is dug forward using the cutter disk 2. Shaft A as shown in FIG.
When starting from inside, the starting portion A2 constituted by a hard and high-strength concrete member (NOMST) penetrates a part of the retaining wall A1 first, and then excavates underground. The excavator 1 needs to excavate a similar concrete member when the vehicle advances into the shaft at the junction point or the final arrival point after the excavation. Fig. 5 on the front of the cutter disk 2.
Therefore, the cutter bits 2a arranged in a large number as described above have a shape and strength that enable not only excavation in the ground but also excavation of the concrete member.

Generally, a gap of several tens of millimeters is formed between the inner wall of the tunnel excavated by the cutter disk 2 and the outer periphery of the cylindrical wall 3 or the segment wall. It is desirable that the gap be filled with mortar or the like as soon as possible. Therefore, the shield excavator 1 is provided with the simultaneous back-filling injection device 4.
As shown in FIG. 5, the injection device 4 covers an injection pipe 4a such as mortar connected to an on-off valve 4b with a cover 4c, and protrudes above the outer periphery 3a of the cylindrical wall 3. However, the cover 4c is provided with an entrance packing A for preventing inundation into the shaft A when starting as shown in FIG.
As shown in FIG.
It has a trapezoidal cross section that rises smoothly from the top.

As described above, when the pouring device 4 protrudes above the outer periphery 3a, when excavating the above-mentioned concrete member at the time of excavation, especially at the time of starting or the like, the space protruding outward from the tunnel wall by the protruding amount. Unless 3c (see FIG. 1 or FIG. 3) is formed, the shield machine 1 cannot advance smoothly. For this reason, in the excavator 1, an extra excavator 10 in which a rotary cutter 20 and a bite cutter 30 are combined is arranged in front of the injection device 4 in the cylindrical wall 3 as shown in FIGS. 1 to 3.

As shown in FIG. 1 (a), the rotary cutter 20 provided at the front of the
Are arranged so that a part thereof protrudes on the outer periphery 3 a of the cylindrical wall 3 in the shield machine 1. As shown in FIG. 1B, the rotary blade 21 has a plurality of saw-tooth-shaped protrusions 22 around the periphery thereof. A cutting edge 23 made of a chip is provided (the cutting edge 23 in the figure is the tip 2 of the projection 22).
Although the blade is attached to 2a, it is also possible to form a groove and insert the blade. And, among the rotary blades 21, a back surface 22 that is on the front side in the traveling direction opposite to the blade edge 23
b has an inclined surface that is greatly inclined from the surface along the radius toward the cutting edge 23. Further, the above-described injection device 4
Since there is a considerable width (see FIG. 5), the width of the rotary blade 21 is also provided close to 100 mm as shown in FIG. The central axis 24 of the rotary blade 21 is rotatably supported by a bracket 25, and the bracket 25 has a hollow portion along the radial direction of the excavator 1 as shown in FIG.
Are slidably disposed in a support box 5a integrated with the frame 5 and connected to a hydraulic cylinder 26. When the cylinder 26 pin-connected to the frame 5 is expanded and contracted, the bracket 25 moves in the radial direction of the excavator 1 while sliding with respect to the support box 5a, and accordingly, a part of the rotary blade 21 ( ) Appears on the outer periphery 3a. Since the bracket 25 is supported by the support box 5a in the front-rear direction and the circumferential direction of the excavator 1 and is supported by the thrust of the cylinder 26 in the radial direction of the excavator 1, the rotary blade 21 resists external force. You can keep that position.

No dedicated drive source is connected to the rotary blade 21 of the rotary cutter 20. The rotary blade 21 rotates based on the speed difference between the rotary blade 21 and the tunnel wall as the shield machine 1 advances, and the rotation causes the cutting edge 23 to bite into the tunnel wall. Details of such a function can be described as follows based on FIGS. 1B to 1E. That is, when the excavator 1 advances with a part of the rotary blade 21 extended on the outer periphery 3a, as shown in FIG.
The rotary blade 21 hits a tunnel wall such as (see FIG. 4).
At this time, the tunnel wall comes into contact with one of the serrated protrusions 22 protruding on the outer periphery 3a and the back surface 22b located forward in the traveling direction.

When the excavator 1 is further advanced, the back surface 22b of the saw-tooth-shaped projection 22 is pushed by the tunnel wall, so that the rotary blade 21 rotates clockwise in FIG. Along with this, as shown in FIG. 1C, the cutting edge 22a of the adjacent serrated projection 22 starts to bite into the inner surface of the tunnel wall.

The excavator 1 further advances and the rotary blade 21
When the blade rotates, the cutting edge 22a cuts deeply into the tunnel wall as shown in FIG. 1 (d) and scrapes (or peels or crushes) a part of the tunnel wall.

After that, when the excavator 1 advances further, the saw-tooth-shaped projections 22, which have been cut off the tunnel wall by the cutting edge 22a as described above, are pushed from the back surface 22b to the tunnel wall, and the rotary blade 2
1 rotates, whereby the cutting edge 22a of the adjacent serrated projection 22 cuts into the tunnel wall as shown in FIG. 1 (e). By repeating the above, the rotary blade 21 forms the space 3c protruding outward with respect to the wall surface of the cylindrical tunnel wall as shown in FIG.
The earth and sand generated by excavating the space 3c is discharged by, for example, flowing a muddy water into the gap 3b between the outer periphery 3a and the tunnel wall and the space 3c due to the extra dug.

The starting portion A2 in FIG. 2 (or FIG. 4)
When the shield machine 1 digs into soft ground after passing through, the injection device 4 may be able to move forward without performing extra digging with the rotary cutter 20. In this case, the hydraulic cylinder 26 shown in FIG. 1 is contracted to retract the rotary blade 21 into the cylindrical wall 3, and the gate plate 6 disposed immediately below the cylindrical wall 3 is closed by the operating hydraulic cylinder 6a. By doing so, the rotary blade 21 is brought into contact with the earth wall.
Therefore, smooth excavation can be performed again when excavating a wall made of a hard concrete member at a junction point or a final arrival point.

The cutting tool 30, which is provided behind the rotary cutter 20, has a plurality of cutting tools 31, 32, 33 provided in two rows on the left and right as shown in FIG. It was established. By cutting the left and right sides of the portion first excavated by the rotary cutter 20 with these blades 31, 32, 33,..., The space 3c through which the injection device 4 can smoothly pass (FIG. 1)
(See (a)) is the purpose of the bite cutter 30. Corresponding to the trapezoidal shape in which the lateral cross-sectional shape of the injection device 4 becomes lower toward the left and right sides (see FIG. 5), the blades 31, 32, 33,. The arrangement is such that the circumferential dimension of the excavator 1 is increased (see FIG. 3) and the height (the radial dimension of the excavator 1) is reduced (see FIG. 2). That is, with respect to the interval between the outer sides of the cutting edge in each stage, while the interval in the foremost blade 31 is almost equal to the width of the rotary blade 21, the latter is gradually widened, while the height from the outer periphery 3 a is increased. Is set to be lower in the later stage.

The cutting tool 30 excavates outside of the tunnel wall by moving relatively to the front of the tunnel wall as the excavator 1 advances, thereby forming a space 3c.
And The surplus digging device 10 is provided with the above-described digging action by the rotary cutter 20 and the bite cutter 30,
A trapezoidal excavation space 3c through which the injection device 5 can pass can be formed.

In the illustrated shield machine 1, the case where the overdigging device 10 digs into the space 3 c for the simultaneous backfilling device 4 has been introduced, but such an overdigging device 10 is used for other purposes. Of course, it is also possible to arrange it on the excavator. In other words, the overdigging device of the invention is used not only for passing objects other than the injection device protruding on the outer periphery of the excavator, but also for excavating a tunnel curved (curved) in a certain direction. be able to.

[0035]

According to the first aspect of the present invention, the excavating device for a shield excavator rotates the rotary blade by an extremely large force accompanying the advance of the excavator by the propulsion means, and the rotation causes the cutting edge to bite into the tunnel wall. Therefore, even when the shield excavator excavates a hard / high-strength concrete member, a necessary extra excavation space outside the tunnel wall can be reliably and smoothly formed. Since a dedicated drive source is not used, it is advantageous in terms of equipment cost and running cost.

In the second aspect of the present invention,
The rotary blade has a structure that rotates reliably when the excavator advances, based on the direction of the central axis, the protruding state on the outer periphery of the excavator, and the difficulty of sliding on the tunnel wall, and further, toward the inner surface of the tunnel wall. The cutting edge is provided at the most protruding part. Therefore, this over-digging device can perform the over-digging by making the cutting edge bite into the inner surface of the tunnel wall reliably and smoothly.

According to the third aspect of the present invention, since the cutting tool is fixedly arranged on the outer periphery of the shield machine behind the rotary blade, an extra dug space extending in the circumferential direction of the tunnel is formed. It is suitable for

According to a fourth aspect of the present invention, a space for allowing a protruding portion having a width in the circumferential direction of the tunnel and having a widened base to pass through the tunnel is efficiently and smoothly formed outside the tunnel wall by the overdigging. can do. Therefore,
When the protruding part on the outer periphery of the excavator is set in consideration of the adhesion with the packing for preventing inundation (entrance packing) in the starting shaft, etc., shielding is performed while smoothing the progress of the protruding part. It becomes possible to advance the excavator.

[Brief description of the drawings]

1 is a detailed view showing one embodiment of the present invention, and FIG. 1 (a) is a vertical cross-section showing the entire front excavator 10 together with the front part (part I in FIG. 2) of a shield machine 1; FIG. Each of FIGS. 1B to 1E is a diagram for explaining the function of the rotary blade 21 in the extra-drilling device 10.

FIG. 2 is a side view showing the entire shield excavator 1, particularly showing a state where the excavation device 10 is excavating the starting portion A2 when starting from the shaft A.

FIG. 3 is a side view showing a part of the shield machine 1 and is a view taken along the line III-III in FIG.

FIG. 4 is a longitudinal sectional view showing the structure of the starting shaft A together with the shield machine 1;

FIG. 5 is a front view (partly shown in cross section) of the shield machine 1 as viewed from the front.

FIG. 6 is a longitudinal sectional view showing a conventional excavation device 40 and the like provided in the shield machine 1 ′.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shield excavator 3a Outer periphery 10 Excavation apparatus 20 Rotary cutter 21 Rotary blade 22 Sawtooth-like projection 23 Cutting edge 24 Central axis of rotation 30 Byte cutter

Claims (4)

(57) [Claims] 1. An excavation device provided near an outer periphery of a shield machine for excavating a tunnel while advancing by a propulsion means, and forming a space protruding outside from a wall surface of the tunnel. An excavation device for a shield machine, wherein the propulsion unit rotates based on a speed difference from a tunnel wall due to advancement, and the rotation causes the cutting edge of the rotary blade to bite into the tunnel wall. 2. The above-mentioned rotary blade has a central axis of rotation along the circumferential direction of the shield machine and is provided with a plurality of saw-tooth-shaped protrusions around the peripheral part, and a part not exceeding the central axis of the shield machine is used. It is projected on the outer periphery, and among the respective saw-tooth-shaped projections of the rotary blade, the above-mentioned cutting edge is provided at a tip portion which is rearward in the traveling direction at a position protruding on the outer periphery of the shield machine as described above. The over-digging device for a shield machine according to claim 1, wherein 3. A cutting tool is fixedly arranged on the outer periphery of the shield machine behind the rotary blade in order to widen the space dug by the rotary blade in the circumferential direction of the tunnel. Item 3. An excavation device for a shield machine according to item 1 or 2. 4. The cutting tool according to claim 1, wherein the cutting tool is disposed in a plurality of stages in the traveling direction of the shield machine, and the latter is provided so as to increase the width of the extra hole and reduce the height thereof. An excavation device for a shield machine according to claim 3.