JPH09303088A - How to replace the cutter bit of the shield machine - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a method capable of easily exchanging a cutter bit in the ground on the way even when a shield tunnel having a long distance from a starting shaft to a reaching shaft is constructed. . SOLUTION: A cutter face 1 of a shield machine 10
A step of closing the 1 ′ sediment collecting slit 11b,
A step of retreating at least the cutter face of the shield machine for a predetermined length at the same time as or before or after the slit closing, and between the cutter face and the cutting face 31 at the same time as or before or after the slit machine is retracted after the slit closing. To
It includes a step of injecting a solidifying agent for solidifying the soil and mud, and a step of replacing the cutter bit 11a of the shield machine after the soil and mud between the cutter face and the face has solidified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for replacing a cutter bit of a shield machine in the ground.

[0002]

2. Description of the Related Art In a conventional shield machine, when the ground is excavated, the cutter bit wears, and as the wear progresses, it becomes difficult to cut the ground, and the amount of sediment taken in from the slits decreases, and the speed of excavation of the shield machine increases. However, the cutter bit had to be replaced. Although this cutter bit varies depending on the hardness of the ground, it is generally desirable to replace it every 1.5 to 2.0 km. Therefore, shafts should be provided at intervals of 1.5 to 2.0 km. A shield machine is excavated inside, and a worker enters the shaft to replace the cutter bit.
However, such a method of exchanging the cutter bit has a drawback that a large construction cost is required to form the vertical shaft.

Therefore, other methods have been implemented in place of the method of constructing the shaft. In other words, drilling from the ground up to the cutter bit replacement point, solidify the ground in advance by the freezing method, etc. to prevent infiltration of groundwater,
A shield machine is dug into this solidified ground, and further, solidifying agents such as cement grout material are injected from within the shield machine into this gap to solidify the soil and mud that enter the gap between the solidified ground and the shield machine. This is a method in which water is stopped and then a worker enters the chamber through the partition wall (bulkhead) inlet of the shield machine and replaces the cutter bit. However, such an exchange method has a drawback that it takes a lot of time and the construction cost is increased because the ground must be improved until the intrusion of groundwater or the like is surely prevented.

In addition to the above, there is a cutter bit exchanging mechanism in which a spare cutter bit is arranged inside a face plate (cutter face), and the spare cutter bit is fixed by a hydraulic jack or a link mechanism so as to be freely taken in and out. . First, the cutter bit fixed to the face plate is used for cutting.When the cutter bit reaches the wear limit, the hydraulic jack is extended to push out the spare cutter bit from the slit, and the spare cutter bit cuts the earth and sand. To dig in. However, the spare cutter bit also wears out when the shield machine excavates a predetermined distance (for example, about 1.5 to 2.0 km) and cannot be used. Bits need to be exchanged.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to construct a shield tunnel having a long distance from a starting shaft to a reaching shaft, on the way. It is an object of the present invention to provide a method capable of easily exchanging a cutter bit in the ground.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned object, and its gist is the step of closing the earth and sand intake slit of the cutter face of the shield machine, and the same or at the same time as the slit closing. A step of moving back and forth at least the cutter face of the shield machine for a predetermined length, and after closing the slit, at the same time as or before or after the shield machine retreats, solidify earth and sand or mud between the cutter face and the cutting face. A method of exchanging a cutter bit of a shield machine, comprising the steps of injecting a solidifying agent for causing the soil and mud to solidify between the cutter face and the face, and then exchanging the cutter bit of the shield machine.

In the method of exchanging the cutter bit of the present invention, in the excavation work of the shield machine which is the pre-process of the slit closing step, the enlarged excavation part having a diameter larger than the outer diameter of the skin plate is formed while excavating the shield machine. Alternatively, a digging pit having the same diameter as the outer diameter of the skin plate may be formed.

The shield machine to which the method for exchanging the cutter bit according to claim 1 of the present invention is applied as long as the earth / soil intake slit of the cutter face is formed so as to be openable / closable, such as a muddy water type shield machine or an earth pressure type shield machine. ,
It can be applied to any of the other types of shield machines. In addition to this, the shield machine to which the cutter bit replacement method according to claim 2 of the present invention is applied may be any machine provided with means capable of forming an enlarged scavenging portion in the natural ground.

Further, in the method of exchanging the cutter bit of the present invention, when at least the cutter face of the shield machine is retracted by a predetermined length, for example, the entire shield machine is retracted or the length of the shield machine in the tunnel axis direction can be expanded or contracted. Can be realized by reducing the length of the shield machine, or by making only the cutter head of the shield machine retractable and retracting only the cutter head.

[0010]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. A shield machine to which the cutter bit replacing method of the present invention can be applied is shown in FIGS.
Is not limited to shield machines.

FIGS. 1 and 2 are vertical sectional views of the shield machine in one step of the method of exchanging the cutter bit of the present invention, and FIG. 3 is a front view of the cutter face of the shield machine of FIG. Is an enlarged view of the tail seal of FIG. 1, FIGS. 5 (a) and 5 (b) are explanatory views showing the opening / closing mechanism of the cutter face, and FIG. 6 (a) is a schematic view of a shield machine different from those of FIGS. FIG. 6 (b) (c) is a longitudinal sectional view.
FIG. 7 is an enlarged view of the tail portion of FIG.

In the shield machine 10 shown in FIG. 1, a cutter head 11 is arranged at the tip of a cylindrical skin plate 20, a partition 14 is provided behind the cutter head 11 by a predetermined length to form a chamber 12, and a partition 14 is provided.
A cutter driving device 15 is provided on the rear side of the cutter head 11, so that the cutter head 11 is driven to rotate. Here, the partition wall 14 is formed with an opening (not shown) sealed by a door (not shown), and a person enters or leaves the chamber 12 through the opening. A gas pumping device (not shown) communicating with the chamber 12 via a conduit (not shown) may be installed in the shield machine 10 behind the partition wall 14, whereby a cutter bit to be described later is provided. At the time of replacement, if gas such as air is pressure-fed into the chamber 12 for limited pressure, it is possible to more effectively prevent the infiltration of water or earth and sand into the chamber 12. Further, a pressure chamber, so-called Manlock (not shown) may be continuously provided at the opening of the chamber 12 together with the gas pressure feeding device.

Further, a jack 18 is arranged inside the rear end of the skin plate 20, and a spreader 18a abutting against the segment 40 is connected to the rear end of the jack 18 so as to apply a reaction force to the segment 40. Jack 1
When the extension operation of 8 is performed, the shield machine 10 can be advanced. Here, the spreader 18a is formed to be connectable to the segment 40. That is, if necessary,
Bolt holes (not shown) provided in the spreader 18a
By inserting a connecting bolt (not shown) into the joint bolt hole (not shown) of the segment 40 and fixing it with a nut (not shown), the spreader 18a and the segment 40 can be connected.

Further, the shield machine 10 is provided with a means for injecting a solidifying agent into the earth and sand or mud between the enlarged moat portion 30 and the cutting face 31 and the cutter head 11. For example,
A solidifying agent supply device (not shown) inside the shield machine 10.
And a solidifying agent injection pipe 19 is connected to the solidifying agent supply device via a pressure feed pump (not shown), and an injection nozzle (not shown) communicating with the solidifying agent injection pipe 19 is connected to the cutter face. The solidifying agent injecting means can be formed by disposing the solidifying agent in 11 '.

A well-known overcutter 13 having a hydraulic jack and a cutting blade is housed in the cutter head 11. When the hydraulic jack is extended, the cutting blade is moved from the outer periphery of the cutter head 11 toward the natural ground 32. The cutting blade can be housed inside the cutter head 11 by contracting the hydraulic jack. Therefore, when the overcutter 13 is projected toward the natural ground 32 for a predetermined length and the cutter head 11 is rotated, the enlarged cavern portion 30 having a diameter larger than the outer diameter of the skin plate 20 is formed as shown in FIG. can do.

The cutter face 11 'of the cutter head 11 has a cutter bit 11 facing the face 31.
a is projected, and the face plate 11f has a slit 11 as an opening for taking in earth and sand and mud into the chamber 12.
b is provided, and the slit 11b is formed so as to be opened and closed by the gate plate 11e as shown in FIGS. That is, the gate plate 11e which is slightly larger than the slit 11b and has a shape complementary to the slit 11b is
It is arranged inside the face plate 11f and is connected to the outer peripheral portion 11g of the cutter head 11 via a link 11d. Further, the tip of the jack 11c is fixed to the gate plate 11e, and the jack 11c can be expanded and contracted. The gate plate 11e by sliding the slit 11b
Can be opened and closed.

Further, as shown in the enlarged view of FIG. 4, a tube-shaped tail seal 21 made of an elastic member such as rubber is fixed to the tail portion of the skin plate 20, which is not shown. A fluid supply pipe communicating with a fluid supply device is connected to the tail seal 21, and the fluid can be pressed into the tail seal 21 to press the tail seal 21 onto the surface of the segment 40, and conversely,
The contact pressure of the tail seal 21 can be relaxed by extracting a predetermined amount of fluid. Since the shield machine 10 shown in FIG. 1 discharges earth and sand and mud by a muddy water system, the muddy water pipe 16 includes a muddy water supply device (not shown) and a chamber 12.
Further, the mud discharge pipe 17 is provided in communication with the chamber 12 and a mud discharge device (not shown).

Next, a method of exchanging the cutter bit in the shield machine 10 having the above structure will be described.

When the cutter bit 11a reaches the wear limit, the overcutter 13 is projected toward the ground 32,
The shield machine 10 is excavated while rotating the cutter head 11. As a result, the enlarged moat portion 30 (see FIG. 1), that is, the skin plate 2 is formed on the outer periphery of the skin plate 20.
It is possible to form an excavated portion having a diameter larger than the outer diameter of zero. The thickness of the enlarged extra moat 30 is formed to be about 10 cm to 20 cm, and the length in the tunnel advancing direction is about 80 cm to 100 cm.
Form to about cm.

After forming the enlarged slab 30, the rotation of the cutter head 11 is stopped and the slit 11b of the cutter face 11 'is closed. As described above with reference to FIG. 5, the slit 11b is closed by operating the inside of the shield machine 10 to extend the jack 11c and sliding the gate plate 11e toward the slit 11b.

After closing the slit 11b, the shield machine 1
A spreader 18a arranged at the tip of the jack 0 of 0 is brought into contact with the segment 40 and fixed with a bolt or a nut. When the jack 18 is contracted, the skin plate 20 slides in the gap between the ground 32 filled with the backfill material 33 and the segment 40 while the tail seal 21 is in contact with the outer surface of the segment 40, and the shield machine 1
0 retreats. At this time, if the fluid supply pressure applied to the inside of the tail seal 21 is increased / decreased and appropriately controlled, it is possible to prevent the backfill material 33 from entering the inside of the shield machine 10, so that the tail seal 21 warps inward. It is possible to prevent the tail seal 21 from being easily deformed and prevent damage, and to prevent the tail seal 21 from slipping on the outer surface of the segment 40 that comes into contact when the tail seal 21 retracts in advance in a factory or the like. If a surface-treating material such as Teflon for smoothing is provided, the warp prevention effect and the damage prevention effect of the tail seal 21 are further improved. Further, since the mud pressure or the earth pressure from the cutting face 31 acts on the cutter face 11 ', the retracting force required for the jack 18 itself is reduced, and the shield machine 10 can be easily retracted. Further, the gap between the ground 32 on which the skin plate 20 slides and the segment 40 is filled with a backfill material such as cement, bentonite, or water glass, which has plasticity and is easily fluidized and deformed again when an external force is applied after curing. However, if such a plastic backfill material is filled, the effect of preventing the tail seal 21 from warping inward is further improved.

After the slit is closed, the shield machine 10
While retreating, the solidifying agent such as bentonite or water glass is injected into the cement between the face 31 and the cutter face 11 ′ and the enlarged extra moat portion 30 to solidify the earth and sand or the mud. At this time, if the solidifying agent is injected while rotating the cutter head 11 or a gas such as air is ejected from the shield machine 10 into the earth and sand or the mud, the effect of mixing the solidifying agent with the earth and sand or the mud is improved. It can be something.

When the shield machine 10 is retracted by a predetermined distance, it is stopped. Here, the length for retracting the shield machine 10 varies depending on the characteristics of the earth pressure and water pressure of the face, the scale of the tunnel, and the like, but the point is that the shield machine 10 is located at a position where groundwater can be prevented from entering the chamber 12. If, for example, the shield machine 10 is retracted by about 50 cm, the chamber 12 is located in the section of the enlarged scavenging section 30 as shown in FIG. 2, and the groundwater contains the cutter head 11 and the skin plate. It is possible to prevent it from turning into the gap with 20.

Then, a radar probe (not shown) such as an electromagnetic wave is measured from inside the shield machine 10 to check whether the soil or mud has solidified. When solidification of soil and mud is confirmed, put a worker into the chamber 12 through the opening of the partition wall 14, remove the bolt (not shown) fixing the cutter bit 11a, and replace the new cutter bit 11a with the bolt. Install and replace. In addition, after confirming the solidification of soil and mud, the shield machine 10 is further moved at a predetermined distance,
For example, it may be moved back by about 50 mm to 100 mm. By retracting the shield machine 10 in this way, a clearance is formed between the solidified sand and the cutter face 11 ', and the workability of exchanging the cutter bit can be further improved.

After exchanging the cutter bit 11a, the partition wall 1
The door of No. 4 is closed to open the slit 11b, and the fixing between the spreader 18a and the segment 40 is released. Then, solidified earth and sand and mud are excavated, and ordinary shield excavation is performed.

The tail portion of the shield machine 10 to which the cutter bit replacing method of the present invention is applied may be formed as shown in FIG. That is, in FIG. 6, the connecting member 23 is fixed to the rear end of the jack 18, and another jack 24 is connected to the connecting member 23. The rear end of the other jack 24 is fixedly formed on the segment 40 similarly to the shield machine 10 of FIG. Further, a connecting skin plate 25 is fixed to the connecting member 23 so as to be in contact with the inner surface of the rear end of the skin plate 20 and slidable, and an end skin plate 22 is fixed to the outer surface of the rear end of the connecting skin plate 25. A tail seal 26 is provided on the inner surface of the rear end of the end skin plate 22. As shown in FIG. 6 (b), the skin plate 20 and the end skin plate 2
The two are arranged on substantially the same plane so that their ends contact each other. In the shield machine 10 having the tail portion configured as described above, the jack 18 is extended and excavated as shown in FIG. The jack 18 is preferably in a stretched state when the enlarged squeeze portion 30 having a predetermined length is formed. That is, when retracting the shield machine 10, the shield machine 10 can be retracted by fixing the rear end of the jack 24 to the segment 40 and then retracting only the jack 18. At this time, the skin plate 20 slides along the surface of the connecting skin plate 25, and the other members of the tail portion (the end skin plate 22, the connecting member 2).
3, jack 24 and connecting skin plate 25),
It is fixed to the segment 40 and does not move. Therefore, since the force to wind inward as described above does not act on the tail seal 26 of the end skin plate 22,
It is sufficient to use a brush-like tail seal made of a general wire, and the backfill material can be smoothly retracted by using a general mortar without using a plastic backfill material. You can

Next, a shield machine having a structure different from those shown in FIGS. 1 and 6 will be described with reference to FIG. In the shield machine 10 of FIG. 1, the cutter head 11 and the skin plate 20 are formed to have substantially the same outer diameter, but in the shield machine 10 of FIG. 7, the outer diameter of the cutter head 11 is larger than the inner diameter of the skin plate 20. It is formed small, and the tube 28 is provided on the entire circumferential surface of the cutter head 11. Further, the length of the skin plate 20 between the cutter head 11 and the partition wall 14 is formed longer than that of the shield machine 10 of FIG. 1, and the cutter head 11 and the cutter driving device 15 are connected to each other to form a cutter head. Cutter movable connecting members 27 and 28 for supporting 11 are formed to be expandable and contractible.
The shield machine 10 of FIG. 7 is different from the shield machine 10 of FIG. 1 in the above points, but other than these differences,
It is formed similarly to the shield machine 10 of FIG.

Here, the tube 28 is formed of an elastic member such as rubber into a ring shape which is continuous over the entire circumference of the cutter head 11 or an intermittent ring shape, and a fluid (not shown) is formed through a conduit (not shown). Connect to supply device. In such a structure, when the fluid is supplied to the tube 28, the tube 28 expands, and the tube 28 is pressed against the inner surface of the skin plate 20 as shown in FIG. The clearance a can be closed. On the contrary, if a predetermined volume of fluid is extracted from the tube 28, the tube 28 contracts, and as shown in FIG. 8 (a), the tube 28 is housed in the outer peripheral surface of the skin plate 20 to open the clearance a. it can.

Further, the cutter movable connecting member 27 is
Cylindrical support material 2 with one end fixed to the cutter head 11
7a and a cylindrical supporting member 27 whose one end is fixed to the partition wall 14
c, the cylindrical support member 27a is formed such that the inner diameter thereof is slightly larger than the outer diameter of the cylindrical support member 27c, and the mutual end portions are fitted and slidably arranged. . Also,
A telescopic jack 27b is arranged inside the tubular supporting members 27a and 27c fitted to each other.
Both ends of 7b are fixed to the cutter head 11 and the partition wall 14, respectively. The cutter movable connecting member 28 is
Is it formed in the same configuration as the cutter movable connecting member 27, or
Alternatively, it may be formed only from members corresponding to the tubular supporting members 27a and 27c.

Next, a method of exchanging the cutter bit in the shield machine 10 of FIG. 7 will be described.

When excavating the shield machine 10, as shown in FIG. 8, the over cutter 13 is extended to the position of the outer surface of the skin plate 20, and the shield machine 10 is excavated while rotating the cutter head 11. This makes it possible to form an excavation pit having substantially the same diameter as the outer surface of the skin plate 20.

After the excavation process, when the cutter bit 11a reaches the wear limit, the rotation of the cutter head 11 is stopped and the slit 11b of the cutter face 11 'is stopped.
To close. After closing the slit 11b, the jack 18 of the shield machine 10 is fixed to the segment 40 with a bolt or a nut.

Next, the cutter head movable connecting member 27,
When the telescopic jack 27b of 28 is contracted, the skin plate 20 remains in the same position and the cutter head 11
Only gradually recede. Here, since the outer diameter of the cutter head 11 is formed smaller than the inner diameter of the skin plate 20, the cutter head 11 gradually fits inside the skin plate 20 as it retracts.

The cutter head 11 is retracted, and the tube 2
When 8 enters the skin plate 20, the cutter head 11 is temporarily stopped, fluid is supplied to expand the tube 28, and the tube 28 is crimped to the inner surface of the skin plate 20 as shown in FIG. Thus, if the clearance a is closed with the tube 28, the solidifying agent, which will be described later,
It is possible to prevent groundwater, sediment and mud from entering the chamber 12.

After closing the clearance a by the tube 28, the solidifying agent is injected while retracting the telescopic jack 27b and retracting the cutter head 11. In this solidifying agent injecting step, a solidifying agent obtained by mixing cement with bentonite, water glass or the like is injected between the face 31 and the cutter face 11 'to solidify the earth and sand or mud. In addition,
At the time of injecting the solidifying agent, if the solidifying agent is injected while rotating the cutter head 11 or gas such as air is blown from the inside of the shield machine 10 into the earth and sand or the mud, the effect of mixing the solidifying agent with the earth and sand or the mud Can be good.

The cutter head 11 is attached to the skin plate 2
Telescopic jack 27b when retracted to a predetermined position within 0
Stop contracting. Here, the length for retracting the cutter head 11 varies depending on the characteristics of the earth pressure and water pressure of the face, the scale of the tunnel, etc., but the point is that the cutter head 11 can reach the position where groundwater can be prevented from entering the chamber 12. Should be set back.

Then, after confirming the solidification of the soil and mud, a worker is put in the chamber 12 and the cutter bit 11a
Perform the replacement work. As in the case of FIG. 1 and FIG. 6 above, after confirming the solidification of soil and mud, the cutter head 1
1 may be retracted by a predetermined distance to create a replacement space for the cutter bit 11a.

After replacing the cutter bit 11a, the partition wall 1
The door of No. 4 is closed to open the slit 11b, and the fixing between the spreader 18a and the segment 40 is released. Then, while loosening the tube 28 and rotating the cutter head 11, the expansion jack 27b of the cutter head movable connecting members 27, 28 is extended to excavate the solidified earth and sand or mud. When the cutter head 11 is advanced to the position shown in FIG. 7, the over-cutter 13 is again extended to the position of the outer surface of the skin plate 20, and normal shield excavation is performed while rotating the cutter head 11.

When the cutter head 11 is retracted, the inner surface of the skin plate 20 with which the tube 28 comes into contact is preliminarily provided with a surface treatment material such as Teflon for smooth sliding in a factory or the like. It is possible to prevent the warp and damage of the. Further, since the mud pressure or earth pressure from the face 31 acts on the cutter face 11 ', the retracting force required for the telescopic jack 27b itself is reduced,
The cutter head 11 can be easily retracted.

The cutter bit replacement method in the shield machine 10 of FIG. 7 has been described above. Prior to the step of retracting the cutter head 11 and storing it in the skin plate 20, the outer periphery of the skin plate 20 is shown in FIG. You may perform the process of forming the expansion extraneous part 30 as shown. Further, the cutter bit replacement method in the shield machine 10 of FIGS. 1 and 6 has been described above on the premise that the expanded overhang portion 30 is formed, but the geology of the excavated ground is good, and the soil, mud, and groundwater. Chamber 12
When there is a low possibility of intrusion into the inside, the step of forming the enlarged scavenging portion 30 may be omitted in the shield machine 10 of FIGS. 1 and 6 as well as the shield machine 10 of FIG. 7.

[0041]

According to the present invention, even when a shield tunnel having a long distance from the starting shaft to the reaching shaft (longer than about 2.0 km) is constructed, at least the cutter face of the shield machine is retracted by a predetermined length. From inside the shield machine, a solidifying agent is injected between the face and the cutter face to solidify soil and mud, thereby improving the ground, and after solidifying, the cutter bit is replaced in the chamber. Therefore, unlike the conventional cutter bit replacement method, it is not necessary to form a shaft for exchanging cutter bits other than the starting shaft and the reaching shaft, and there is no need to provide a boring hole from the ground for ground improvement. Since the above process can be performed from the inside of the shield machine, the cutter bit can be easily replaced.

Further, in the present invention, the cutter head is retracted to be housed in the skin plate, and further, an enlarged moat is formed in the ground around the outer periphery of the shield machine to improve the ground between the face and the cutter face. Therefore, the effect of stopping water in the chamber can be further improved.

Further, in the present invention, since the cutter bit can be easily replaced in the ground on the way, if the replacement of the cutter bit is repeated a proper number of times, the excavation continuation distance is limited like the conventional spare cutter bit. It will not be done.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a shield machine in one step of a method of exchanging a cutter bit according to the present invention.

FIG. 2 is a vertical cross-sectional view of the shield machine in one step of the method of exchanging a cutter bit according to the present invention.

3 is a front view of a cutter face of the shield machine of FIG. 1. FIG.

FIG. 4 is an enlarged view of the tail seal of FIG.

5A and 5B are explanatory views showing an opening / closing mechanism of a cutter face.

6 (a) is a vertical cross-sectional view of a shield machine having a tail portion different from those in FIGS. 1 and 2, and (b) (c) is (a).
It is an enlarged view of the tail part of.

FIG. 7 is a vertical cross-sectional view of a shield machine different from FIGS. 1, 2 and 6.

FIG. 8 is a partially enlarged sectional view of the shield machine shown in FIG.

9 is a cross-sectional view showing a state in which the cutter head portion is retracted in the shield machine shown in FIG. 7.

10 is a partially enlarged cross-sectional view of the shield machine shown in FIG.

[Explanation of symbols]

 10 Shielding Machine 11 Cutter Head 11 'Cutter Face 11a Cutter Bit 11b Slit (Soil-and-Soil Intake Slit) 12 Chamber 13 Overcutter 14 Partition Wall 20 Skin Plate 30 Enlarged Excess Portion 31 Cutting Face 32 Natural Rock

Claims (2)

[Claims] 1. A step of closing a soil intake slit of a cutter face of a shield machine; a step of retracting at least the cutter face of the shield machine for a predetermined length at the same time as or before or after the slit closure; and after the slit is closed, the shield. At the same time as or before or after the retreat of the machine, a step of injecting a solidifying agent for solidifying the soil and mud between the cutter face and the cutting face, and solidifying the soil and mud between the cutter face and the cutting face. And then replacing the cutter bit of the shield machine. 2. The method of exchanging a cutter bit for a shield machine according to claim 1, further comprising a step of forming an enlarged digging portion having a diameter larger than an outer diameter of the skin plate while excavating the shield machine before the slit closing step.