JP4145212B2 - Tunnel construction method and shield excavator used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tunnel construction method and a shield excavator used therefor, and more particularly, to a tunnel construction method and a shield excavator used for the tunnel construction method capable of expanding and reducing the cross section of the tunnel during tunnel excavation.
[0002]
[Prior art]
Shield tunnels often require a tunnel with a widened section in the middle. For example, in a subway tunnel, a station must be provided every 500 to 1000 m, and in a road tunnel, an emergency parking zone must be provided every approximately 500 m. Therefore, as a method of widening the tunnel cross-section, the excavation method, the method of widening the ground by widening the ground, or the method of widening the cross-section partially from the inside of the tunnel, or the method of excavating by attaching the enlarged portion to the shield excavator Etc. were carried out.
However, the excavation method and the method of excavating with an enlarged portion attached to a shield excavator in a vertical shaft occupy the land for a long period of time, so the influence on the surrounding environment becomes very large. Moreover, the method of improving the ground and partially widening the cross section from the inside of the tunnel has many problems in terms of construction cost, construction period, and environment. For this reason, a shield excavator provided with a widening device has been proposed (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-329781 (page 3-6, FIG. 13)
[0004]
[Problems to be solved by the invention]
However, the conventional one in which the widening device is provided in the shield excavator may have a complicated mechanism or a limited excavation cross-sectional shape.
The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a tunnel construction method and a shield excavator used for the tunnel construction method that can easily widen and reduce the cross section of the tunnel, shorten the construction period, and reduce the construction cost. And
[0005]
[Means for Solving the Problems]
In order to achieve the above object, when the tunnel cross-section is widened, the tunnel construction method according to the present invention includes a cylindrical skin plate that forms an outer peripheral portion, and a standard well having a predetermined cross-sectional area at the front portion of the skin plate. And a widening member excavating the widening pit, a widening member that forms a part of the skin plate and can be projected and retracted in the widening direction of the widening pit, and a tail that forms a part of the skin plate and slides in the digging direction A first step of excavating the widening pit with the cutter using a shield excavator comprising a plate and a widening skin plate for forming a shield widening portion at a rear part of the shield excavator; and A second step of projecting toward the pit, and a predetermined number of the widening skin plate from the projecting widening member along the tail plate. A third step of forming a shield widening portion at the rear of the shield excavator, a fourth step of sliding the tail plate in the direction of excavation, and lining a widening pit segment inside the widening skin plate And a fifth step of constructing a widening tunnel.
Here, the standard mine is a mine having substantially the same outer diameter as the skin plate, and the widening pit is a mine having a partially larger outer diameter than the standard mine. The direction of the shield excavator is called “front”, and the opposite direction is called “rear”.
Moreover, in the tunnel construction method according to the present invention, in order to prevent the collapse of the natural ground due to the excavation of the widened portion, the excavated earth and sand of the widened portion is replaced with the natural ground retaining material together with the first step, and the second step It is preferable to collect the natural ground retaining material corresponding to the volume of the widening member protruding together and recover the natural ground retaining material between the widening member and the tail plate in the fourth step.
Here, the widened portion refers to a portion that is partially widened outward from the standard well.
Furthermore, in the tunnel construction method according to the present invention, in order to prevent sufficient earth and sand from entering even in an environment where earth pressure or water pressure is high, and to ensure water-stopping, when the construction of the widening tunnel is started, It is preferable to provide a water stop plate on the widening skin plate wife side of the last part of the shield excavator and to provide a water stop member on the widening skin plate in the vicinity of the water stop plate.
[0006]
On the other hand, when the tunnel cross-section is reduced, in the tunnel construction method according to the present invention, a cylindrical skin plate that forms an outer peripheral portion, and a standard mine and a widening pit having a predetermined cross-sectional area at the front portion of the skin plate. A cutter for excavation; a widening member that forms a part of the skin plate and can be projected and retracted in the widening direction of the widening pit; a tail plate that forms a part of the skin plate and slides in the excavation direction; and the shield A first step of sliding the tail plate in a direction opposite to the direction of excavation using a shield excavator provided with a widening skin plate for forming a shield widening portion at the rear of the excavator, and for a standard mine inside the tail plate A second step of lining a segment of a standard tunnel to build a standard tunnel and a predetermined number of the widened skin plates along the tail plate. A third step of sequentially pulling back to the front of the excavator and recovering the widened skin plate into the shield excavator using the protruding widening member as a recovery port; and a fourth step of immersing the protruding widening member into the shield excavator It is characterized by providing.
Further, in the tunnel construction method according to the present invention, in order to prevent the collapse of the natural ground due to the excavation of the widened portion, the tail plate and the widened skin plate are between the first step and the third step. It is preferable to fill the natural ground holding material in between and fill the natural ground filler in the space where the widening member protruded together with the fourth step.
Furthermore, in the tunnel construction method according to the present invention, in order to prevent sufficient earth and sand from entering even in an environment where earth pressure or water pressure is high and to ensure water-stopping, when the construction of the widening tunnel is finished, It is preferable to provide a water stop plate on the widened skin plate wife side of the rearmost part of the shield excavator.
[0007]
In the shield excavator according to the present invention, a shield excavator comprising a cylindrical skin plate that forms an outer peripheral portion, and a cutter that excavates a standard well and a widening well having a predetermined cross-sectional area at the front portion of the skin plate. A widening member that forms a part of the skin plate and can be projected and retracted in the widening direction of the widening pit, a tail plate that forms a part of the skin plate and slides in the advancing direction, and a rear part of the shield excavator A widening skin plate for forming a shield widening portion, and sequentially extruding a predetermined number of the widening skin plate from the protruding widening member along the tail plate to the rear of the shield excavator, and the rear portion of the shield excavator A shield widening portion is formed on the shield plate, and a predetermined number of the widening skin plates are disposed along the tail plate. Successively pulled back to the machine forward, and recovering the widening skin plate the widening member protruding as recovery port to said shield excavating machine.
In the shield excavator according to the present invention, in order to prevent the collapse of the natural ground accompanying the excavation of the widened portion, a filling means for filling the widened portion excavated by the cutter with the natural ground retaining material is provided at the rear of the cutter. It is preferable to provide in.
Furthermore, in the shield excavator according to the present invention, when the construction of the widening tunnel is started and in order to prevent sufficient earth and sand from entering even in an environment where the earth pressure or the water pressure becomes high and to ensure water-stopping, When finishing construction, it is preferable to provide a water stop plate to be provided on the widened skin plate wife side of the rearmost part of the shield excavator.
[0008]
According to the present invention, a predetermined number of widening skin plates are sequentially pushed out from the protruding widening member to the rear of the shield excavator along the tail plate to form a shield widening portion at the rear of the shield excavator, and a predetermined number of the above-mentioned The widening skin plate is sequentially pulled back along the tail plate to the front of the shield excavator, and the widening skin plate is recovered into the shield excavator by using the protruding widening member as a recovery port. Therefore, it is possible to easily build a widening tunnel and to easily return from the widening tunnel to the standard tunnel.
In addition, since the widening tunnel can be constructed any number of times in the long distance tunnel, the construction period can be shortened and the construction cost can be reduced.
Furthermore, since only the rear part of the shield excavator is widened by the widening skin plate, it is possible to simplify the construction, and it is easy to excavate the widening pit only on one side in the excavation direction without causing a strong adverse effect on the shield body. It can be carried out.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 are plan sectional views showing a method of widening a tunnel section. Since the shield excavator is an axis object, only one side is shown, but the portion not shown is also composed of similar components. 4 is a perspective view of the widened skin plate, and FIG. 5 is a perspective view of the shield excavator according to the present invention. Hereinafter, the same components as those in FIG.
As shown in these drawings, a shield excavator 1 according to the present invention includes a cylindrical skin plate 4 that forms an outer peripheral portion, a cutter 2 that is located at the front of the skin plate 4 and excavates a standard mine, A copy cutter 3 for excavating the widened portion is provided. The cutter 2 has a substantially disk shape, and a standard mine is excavated by rotating a cutter bit (not shown) provided at the tip. Further, the cutter 2 incorporates a bar-shaped copy cutter 3 that can be projected and retracted in a direction orthogonal to the excavation direction. This copy cutter 3 is immersed in the cutter 2 when excavating the standard pit, but protrudes from the cutter 2 when excavating the widening pit, and rotates around the axis in the protruding direction. The widened portion is excavated by a cutter bit (not shown) provided at the top.
A plurality of pressing jacks 9 are provided in the circumferential direction inside the skin plate 4 behind the shield excavator 1. The pressing jack 9 extends in the direction of excavation, thereby pressing the standard mine segment 20 or the thrust receiving piece 20a, which will be described later, lining the inside of the skin plate 4. It is something to dig up.
[0010]
In addition, the shield excavator 1 according to the present invention includes a widening member 5 that forms a part of the skin plate 4 and is capable of appearing in the widening direction of the widening pit, and a part of the skin plate 4 behind the shield excavator 1. And a tail plate 7 that slides in the direction of excavation, and a widening skin plate 6 for forming a shield widening portion at the rear of the shield excavator 1. The widening member 5 has a substantially box shape, and the widening member 5 is provided with a slide jack 10 for pushing and pulling back the widening skin plate 6. The shape of the widened skin plate 6 is substantially U-shaped (see FIG. 4), and a slit 5a for extruding and retracting the widened skin plate 6 is provided on the side surface of the widened member 5 on the rear side of the shield excavator 1. Is provided.
As shown in FIG. 5, a pair of upper and lower guide portions 11 that contact the widening member 5 are provided on the outer surface of the skin plate 4. The widening skin plate 6 and the tail plate 7 It is designed to slide along.
[0011]
Furthermore, in the shield excavator 1 according to the present invention, the skin plate 4 has a filling device (not shown) for filling the widened portion excavated by the copy cutter 3 with the natural ground retaining material S, The natural ground holding material S is discharged from the natural ground holding material discharge port 13 provided in the front part of the skin plate 4. The natural ground holding material S is mainly used for preventing collapse of the natural ground G accompanying excavation of the widened portion. As the material of the natural ground retaining material S, for example, a material in which bentonite and a substance having high fluidity and hardly flowing out to the groundwater flow (mineral oil, water-absorbing polymer, magnesium chloride solution, etc.) are used.
Further, in the shield excavator 1 according to the present invention, a water stop member 12a is provided on the inner side of the tail plate 7 in order to prevent a sufficient amount of earth and sand from entering even in an environment where the earth pressure or the water pressure becomes high and to ensure water stoppage. While being attached, it has the water stop plate 8 provided in the widening skin plate 6 wife side of the shield excavator 1 rearmost part.
[0012]
Next, a method for widening the tunnel cross section by the shield excavator 1 according to the present invention will be described with reference to FIGS. 1 to 3 and FIG.
First, as shown in FIG. 1, a predetermined widening pit is excavated by the cutter 2 and the copy cutter 3 protruding from the cutter 2. At this time, with excavation of the widened portion, the natural ground retaining material S is discharged from the natural ground retaining material discharge port 13 provided in the front portion of the skin plate 4, and the earth and sand in the widened portion is replaced with the natural ground retaining material S. . Further, a widening skin plate 6 is loaded in the wide box-shaped widening member 5.
When the widening pit is formed past the rear end position of the shield excavator 1, the shield excavation is stopped, and the widening loaded with the widening skin plate 6 is collected while collecting the natural ground retaining material S as shown in FIG. The member 5 is protruded from the skin plate 4 toward the widening pit. In addition, one ring of the standard well special segment 20b in which a slit for projecting the water blocking plate 8 is formed on the front surface of the standard well segment 20 behind the tail plate 7 is assembled, and the standard well special segment 20b is assembled. One ring of standard mine segments 20 is assembled on the front surface of the mine.
Then, as shown in FIG. 5C, a predetermined number of widened skin plates 6 are inserted from the slits 5 a on the rear surface of the widening member 5, and the outer surface of the skin plate 4 by the slide jack 10 provided in the widening member 5. Are sequentially pushed out from the slit 5a on the rear surface of the projecting widening member 5 to the rear of the shield excavator 1 to form a shield widening portion at the rear of the shield excavator 1. At this time, the widened skin plate 6 and the widened skin plate 6 are fastened with bolts (not shown).
Next, as shown in FIG. 3, the water stop plate 8 is protruded from the slit of the special segment 20b for the standard well toward the widening shaft, and the widening skin plate 6 wife side at the rearmost part of the shield excavator 1 is connected to the water stop plate. 8 is used to prevent the invasion of earth and sand and to prevent water. After confirming the water stoppage status, the ground retaining material S between the widened skin plate 6 and the tail plate 7 is collected, and the tail plate 7 is removed from the shield excavator 1 along the guide portion 11 provided on the outer surface of the skin plate 4. Slide forward. Then, one ring of the standard well segment 20 in the widened skin plate 6 is removed, and the water stop member 12b is attached to the widened skin plate 6 in the vicinity of the water stop plate 8.
Thereafter, the widening pit segment 21 is lined in the shield widening portion at the rear of the shield excavator 1. At this time, the first widening pit segment 21 has a wife. Moreover, the thrust receiving piece 20a is installed in the position of the segment 20 for standard wells in a shield widening part. Thereafter, the pressing jack 9 inside the skin plate 4 behind the shield excavator 1 presses the thrust receiving piece 20a, and the shield excavator 1 advances by the reaction force.
In this widening excavation, the widened portion is filled with the natural ground holding material S. However, in this embodiment, since the widening member 5 is located somewhat rearward from the copy cutter 3, the natural ground is expanded along with the widening excavation. The holding material S also moves, and the discharge of the natural ground holding material S is small.
[0013]
On the other hand, a first embodiment of a tunnel cross-section reduction method using the shield excavator 1 according to the present invention will be described with reference to FIGS. 6 to 9 are plan sectional views showing the first embodiment of the tunnel cross-section reduction method, but only one side is shown because the shield excavator is an axis object.
First, when the reduction position is reached, the shield excavator 1 stops digging. Then, as shown in FIG. 6, one thrust receiving piece 20 a is removed, and the shield excavator 1 is finally passed through the slit of the widening pit special segment 21 b in order to prevent the invasion of earth and sand in the widening portion and to ensure water stoppage. The water stop plate 8 is installed on the wide skin plate 6 wife side of the part. Therefore, one ring of the widening pit special segment 21b in which a slit for projecting the water blocking plate 8 is formed on the front surface of the widening pit segment 21 is assembled. Furthermore, one ring of the widening pit segment 21 is assembled on the front surface of the widening pit special segment 20b.
Subsequently, as shown in FIG. 7, the widening pit segment 21 ahead of the water stop plate 8 is disassembled, and the water stop member 12 b attached to the widening skin plate 6 at the rearmost part is removed. Then, the tail plate 7 is slid rearward of the shield excavator 1 along the guide portion 11 provided on the outer surface of the skin plate 4.
Next, as shown in FIG. 8, the standard mine segment 20 is lined on the extension of the thrust receiving piece 20a. Then, a natural ground retaining material S is discharged into the widened skin plate 6 from a natural ground retaining material discharge port (not shown) provided in the widening member 5, and the natural ground between the tail plate 7 and the widened skin plate 6 is discharged. The holding material S is filled. Thereafter, a predetermined number of widening skin plates 6 are sequentially pulled back to the front of the shield excavator 1 along the guide portions 11 provided on the outer surface of the skin plate 4 by the sliding jack 10 provided in the widening member 5. The widening skin plate 6 is collected in the shield excavator 1 from the slit 5a on the rear surface of the protruding widening member 5.
Finally, as shown in FIG. 9, the projecting widening member 5 is immersed in the shield excavator 1 while filling the natural ground retaining material S. Thereafter, the standard mine segment 20 is pressed by the pressing jack 9 inside the skin plate 4 behind the shield excavator 1, and the shield excavator 1 resumes digging by the reaction force.
[0014]
Next, a second embodiment of the tunnel cross-section reduction method using the shield excavator 1 according to the present invention will be described with reference to FIGS. Here, FIG. 10 to FIG. 13 are plan sectional views showing a second embodiment of the tunnel cross-section reduction method, but only one side is shown because the shield excavator is an axis object.
First, as shown in FIG. 10, a water stop plate 8 is installed on the widening skin plate 6 wife side at the rearmost part of the shield excavator 1 in order to prevent the invasion of earth and sand and the water stoppage in the widening portion.
Next, as shown in FIG. 11, the widening skin plate 6b covering the foremost widening pit segment 21a is left, and the connection with the previous widening skin plate 6a is released. Subsequently, the tail plate 7 is slid rearward of the shield excavator 1 along the guide portion 11 provided on the outer surface of the skin plate 4. Then, the standard mine segment 20 is lined on the extension of the thrust receiving piece 20a. Further, the natural ground retaining material S is discharged from a natural ground retaining material discharge port (not shown) provided in the widening member 5, and the natural ground retaining material S is filled between the tail plate 7 and the widening skin plate 6. .
After that, as shown in FIG. 12, the widening skin plate 6 b covering the foremost widening pit segment 21 a is left, and a predetermined number of widening skin plates 6 are attached to the sliding jack 10 provided in the widening member 5. The widened skin plate 6 is collected in the shield excavator 1 from the slit 5a on the rear surface of the widening member 5 that is sequentially pulled back to the front of the shield excavator 1 along the guide portion 11 provided on the outer surface of the skin plate 4.
Finally, as shown in FIG. 13, after the projecting widening member 5 is immersed in the shield excavator 1, the standard mine segment 20 is pressed by the press jack 9 inside the skin plate 4 behind the shield excavator 1. The shield excavator 1 resumes excavation by the reaction force.
The present embodiment is different from the first embodiment in that one ring of a part of the widening skin plate 6 and the widening pit segment 21a is left.
[0015]
In the tunnel construction method according to the present embodiment and the shield excavator used therefor, a predetermined number of widened skin plates 6 are projected from the projecting widening member 5 along the guide portions 11 provided on the outer surface of the skin plate 4. The guide 5 is extruded from the slit 5a on the rear surface of the member 5 to the rear of the shield excavator 1 to form a shield widened portion at the rear of the shield excavator 1, and a predetermined number of widened skin plates 6 are provided on the outer surface of the skin plate 4. 11 is a mechanism for sequentially pulling back the shield excavator 1 along the front and the slit 5a on the rear surface of the projecting widening member 5 to collect the widened skin plate 6 into the shield excavator 1, without complicated work. Easily build widening tunnels and easily return from widening tunnels to standard tunnels.
In addition, since the widening tunnel can be constructed any number of times in the long distance tunnel, the construction period can be shortened and the construction cost can be reduced.
Furthermore, since only the rear part of the shield excavator 1 is widened by the widening skin plate 6, it is possible to simplify the structure and to dig a widening pit only on one side in the excavation direction without causing a strong adverse effect on the shield body. It can be done easily.
[0016]
【The invention's effect】
As described above, according to the tunnel construction method and the shield excavator used therefor according to the present invention, the tunnel cross section can be easily widened and reduced, and the construction period can be shortened and the construction cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a plan sectional view showing a method for widening a tunnel section.
FIG. 2 is a plan sectional view showing a method for widening a tunnel section.
FIG. 3 is a plan sectional view showing a method for widening a tunnel section.
FIG. 4 is a perspective view of a widened skin plate.
FIG. 5 is a perspective view of a shield excavator.
FIG. 6 is a plan sectional view showing a first embodiment of a tunnel cross-section reduction method.
FIG. 7 is a plan sectional view showing a first embodiment of a tunnel cross-section reduction method.
FIG. 8 is a plan sectional view showing a first embodiment of a tunnel cross-section reduction method.
FIG. 9 is a plan sectional view showing a first embodiment of a tunnel cross-section reduction method.
FIG. 10 is a plan sectional view showing a second embodiment of a tunnel cross-section reduction method.
FIG. 11 is a plan sectional view showing a second embodiment of a tunnel cross-section reduction method.
FIG. 12 is a plan sectional view showing a second embodiment of a tunnel cross-section reduction method.
FIG. 13 is a plan sectional view showing a second embodiment of a tunnel cross-section reduction method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Shield excavator 2 ... Cutter 3 ... Copy cutter 4 ... Skin plate 5 ... Widening member 6, 6a, 6b ... Widening skin plate 7 ... Tail plate 8 ... Water stop plate 9 ... Pressing Jack 10 …… Sliding jack 11 …… Guide part 12a, 12b …… Water-stop member 13 …… Stone retaining material discharge port 20 …… Standard well segment 20a …… Thrust receiving piece 20b …… Standard well special Segments 21, 21a ... Widening pit segment 21b ... Widening pit special segment G ... Natural mountain S ... Natural mountain retaining material

Claims (9)

A cylindrical skin plate forming an outer peripheral portion, a cutter for excavating a standard pit and a widening pit having a predetermined cross-sectional area at the front of the skin plate, and a widening of the widening pit forming a part of the skin plate Shield comprising: a widening member capable of appearing and retracting in a direction; a tail plate that forms a part of the skin plate and slides in a digging direction; and a widening skin plate for forming a shield widening part at the rear of the shield excavator A tunnel construction method with a widening of a tunnel cross section using an excavator,
A first step of excavating the widening pit with the cutter;
A second step of projecting the widening member toward the widening pit,
A third step of sequentially extruding a predetermined number of the widening skin plate from the projecting widening member to the rear of the shield excavator along the tail plate and forming a shield widening portion at the rear of the shield excavator;
A fourth step of sliding the tail plate in the direction of excavation;
A tunnel construction method comprising: a fifth step of constructing a widening tunnel by lining a segment for a widening pit inside the widening skin plate. The excavated earth and sand of the widened portion is replaced with a natural ground retaining material together with the first step, and the natural ground retaining material corresponding to the volume of the widening member protruding together with the second step is collected, and the fourth step is performed, The tunnel construction method according to claim 1, wherein the ground retaining material between the widening member and the tail plate is collected. When the construction of the widening tunnel is started, a water stop plate is provided on the widening skin plate wife side of the shield excavator last part, and a water stop member is provided on the widening skin plate in the vicinity of the water stop plate. The tunnel construction method according to claim 1 or 2, characterized by the above-mentioned. A cylindrical skin plate forming an outer peripheral portion, a cutter for excavating a standard pit and a widening pit having a predetermined cross-sectional area at the front of the skin plate, and a widening of the widening pit forming a part of the skin plate Shield comprising: a widening member capable of appearing and retracting in a direction; a tail plate that forms a part of the skin plate and slides in a digging direction; and a widening skin plate for forming a shield widening part at the rear of the shield excavator A tunnel construction method that uses a excavator to reduce the cross section of the tunnel,
A first step of sliding the tail plate in a direction opposite to the excavation direction;
A second step of lining a standard mine segment on the inside of the tail plate to build a standard tunnel and a predetermined number of the widening skin plates are sequentially pulled back to the front of the shield excavator along the tail plate and protruded. A third step of collecting the widened skin plate into the shield excavator using the widening member as a collection port;
And a fourth step of immersing the protruding widening member into the shield excavator. Between the first step and the third step, a ground retaining material is filled between the tail plate and the widening skin plate, and the ground member is projected into the space where the widening member protruded together with the fourth step. 5. The tunnel construction method according to claim 4, wherein a pile filler is filled. 6. The tunnel construction method according to claim 4, wherein when the construction of the widening tunnel is finished, a water stop plate is provided on the widening skin plate wife side of the rearmost part of the shield excavator. In a shield excavator comprising a cylindrical skin plate that forms an outer peripheral portion, and a cutter that excavates a standard pit and a widening pit having a predetermined cross-sectional area at the front portion of the skin plate,
A widening member that forms a part of the skin plate and can be projected and retracted in the widening direction of the widening pit, a tail plate that forms a part of the skin plate and slides in the digging direction, and a shield at the rear of the shield excavator A widened skin plate for forming the widened portion;
A predetermined number of the widening skin plates are sequentially pushed out from the protruding widening member along the tail plate to the rear of the shield excavator to form a shield widening portion at the rear of the shield excavator, and a predetermined number of the widening skins. A shield excavator, wherein the plate is sequentially pulled back along the tail plate to the front of the shield excavator, and the widened skin plate is recovered into the shield excavator using the protruding widening member as a recovery port. The shield excavator according to claim 7, wherein filling means for filling the widened portion excavated by the cutter with a ground retaining material is provided behind the cutter. The water stop plate for providing at the widening skin plate wife side of the last part of the shield excavator at the time of starting construction of the widening tunnel and finishing construction of the widening tunnel, or The shield excavator according to 8.

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