JPH112088A - Shield excavating machine and shield working method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a shield construction technique associated with a middle fold type shield construction method capable of changing-over so that a plurality of underground pits can be excavated after excavation of a single underground pit wherein no complicated procedures are required. SOLUTION: In a shield excavating machine having double circular section, the shield body is divided into a front trunk equipped with a cutter head in the front and a rear trunk having a segment assembling space, and screen walls 2c and 2d for front trunk are provided in the missing parts of a pair of cylinders 2a and 2b at the front trunk. In the missing parts of a pair of cylinders 3a and 3b at the rear trunk, screen walls 3c and 3d for rear trunk to enclose at least their forefront parts are provided so as not to partition the segment assembling space, and the tail of each surrounding wall formed from the screen wall 2c and 2d and the peripheral wall of cylinder 2a and 2b is fitted rotatably to the forefront of each surrounding wall formed the screen wall 3c and 3d and the peripheral wall of cylinder 3a and 3b, and a middle fold seal 7 is provided between the forefront of each surrounding wall and the tail of surrounding wall.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield excavator having a shield body formed by connecting a plurality of cylindrical bodies having a notch on a peripheral wall thereof in parallel so that the notches are adjacent to each other. The present invention relates to a shield method using such a shield machine.

[0002]

2. Description of the Related Art When constructing an underground pit such as a tunnel with a shield excavator, a thrust is applied to a shield body by a shield jack and a face is excavated by a cutter head provided in front of the shield body to excavate an underground pit. After excavating an underground pit having a predetermined unit length in this manner, segments are assembled in the segment assembling space at the rear inside the shield main body, and the excavated underground pit is lining. When constructing an underground pit, it is not always necessary to excavate an underground pit with a single circular cross section like a normal tunnel, and it may be necessary to dig an underground pit with a relatively large width and height . As a shield machine capable of meeting such requirements, a shield machine having an overlapping circular cross-section, in which a shield body has a shape in which a plurality of circles having different centers are overlapped with each other, is generally known. Have been. The shield body of this shield excavator is configured such that a plurality of cylindrical tubular bodies having a missing portion on a peripheral wall are arranged and connected in parallel so that the missing portions are adjacent to each other.

[0003] A typical example of constructing an underground pit with a shield excavator having an overlapping circular section is a subway tunnel construction in which a double track is laid. This overlapping circular section shield machine is ideal for constructing an underground pit with a constant width and height like a subway tunnel laying a double track, but the double track is used for the station platform. It is not always suitable when it is necessary to branch the underground pit halfway as in the case of branching to both sides of the mine. In order to respond to such demands, when using a shield tunneling machine with an overlapping circular cross section that connects two shield tunneling machines in a separable manner, when excavating a single underground tunnel and branching the underground tunnel along the way, Recently, a shield construction method has been attempted in which the shield excavators are separated from each other, and each of the separated shield excavators separately excavates two branched underground tunnels. Such a shield method is disclosed, for example, in Japanese Patent Application Laid-Open No. 2-144493.

[0004]

The above-mentioned Japanese Patent Application Laid-Open No. 2-144
In the conventional shield method disclosed in Japanese Patent No. 493, a plurality of underground tunnels to be branched have a relatively gentle curve, as in the case of performing tunnel construction in which a double track is branched to both sides of a station platform. However, when each of these underground shafts has a relatively sharp curve, it is not suitable because each shield excavator cannot excavate a sharply curved underground shaft. For example, when excavating a double-track tunnel in a subway tunnel construction, it may be necessary to branch the underground pit even at a place other than the platform of the station, depending on the surrounding conditions such as ground conditions. In such a case, it is desirable to always excavate directly under the road, so it is necessary to excavate an underground pit along one or more roads. Must. In the case of constructing such a branched underground tunnel with a sharp curve, the conventional shield method as disclosed in the above-mentioned publication cannot cope with the problem. In order to make such construction possible, each shield machine that separates after excavating a single underground mine, the shield body may be divided into a front body and a rear body, and it may be a folding type,
To do so, seal the space between the front and rear bodies to prevent intrusion of earth and sand when excavating a single underground pit with an overlapping circular section shield excavator. In addition, it is necessary to seal between the front body and the rear body so that earth and sand and the like do not enter while allowing the shield body to be bent in the middle. Therefore, when excavating a single underground pit, when switching to branching multiple underground pits so that they can be excavated by the mid-bend shield method, complicated work is required especially for remodeling the seal part of the shield machine. Until then, no such attempt had been made. As a shield excavator for excavating an underground pit with a relatively large width and height, in addition to such an overlapping circular section shield excavator, a rectangular shield excavator in which the shield body has a rectangular cross section is known, As for the rectangular shield machine, as long as the conventional shield method is applied,
The same problem as described above occurs.

The present invention has been made in view of the above situation, and a technical problem thereof is to provide a shield excavator having a shield body in which a plurality of cylindrical bodies are connected in parallel, such as a shield excavator having an overlapping circular cross section. In a shield method using such a shield machine, a single underground tunnel is excavated by the shield method, and then multiple branched underground holes are excavated by the mid-bend shield method without complicated work. It is an object of the present invention to provide a shield technology that can be switched as much as possible.

[0006]

In order to achieve the technical object of the present invention, the first invention of this application relating to a shield excavator employs the following technical means 1) and employs this application relating to a shield method. The second invention employs the following technical means 2).

[0007] 1) A shield body having an outer shape formed by connecting a plurality of tubular bodies having a missing portion on a peripheral wall in parallel so that the missing portions are adjacent to each other, and being connected to the front of each of the plurality of tubular bodies. Each has a cutter head, and has a segment assembly space in the rear part of the shield body, and after excavating an underground pit of a predetermined length, separates a plurality of cylindrical bodies into at least two blocks and excavates an independent middle bent shield excavation In a shield machine to be modified into a machine, the shield body is divided into a front body provided with a cutter head in front and a rear body having a segment assembly space, and at least one of the missing parts of the cylindrical body on the front body side A front body shielding wall for shielding at least the rear end portion is provided at each of the missing parts adjacent to the front body, and at least the rear body side tubular body is provided with a shielding part at a rear body side so as to follow each of these front body shielding walls. A rear trunk shielding wall for shielding the front end is provided so as not to partition the segment assembly space, and a rear trunk shielding wall formed by the front trunk shielding wall and the peripheral wall of the cylindrical body on the front trunk side is provided. The front end of each surrounding wall formed by the end portion, each rear body shielding wall, and the peripheral wall of the cylindrical body on the rear body side is rotatably fitted, and the front end of each of these surrounding walls is fitted. A center-fold seal is provided between the rear end of each part and each surrounding wall. 2) A first step of excavating an underground pit having a predetermined length by the shield machine configured as in 1), and after the first step, a plurality of tubular bodies on the front trunk side and the rear trunk side are removed. Separate for each block in which the surrounding wall is formed, and separate each separated block,
The underground pit is constructed through a second step of remodeling into a plurality of independent half-fold shield excavators and a third step of excavating an underground tunnel using the remodeled plural half-fold shield excavators.

[0008] The first invention of this application relating to a shield machine is configured as described in the above 1). Therefore, when constructing an underground pit, first, as a first step, simply using a shield machine is used. Drill one underground pit to the desired length. After excavating the underground pit of a predetermined length in this way, as a second stage, the plurality of cylindrical bodies on the front trunk side and the rear trunk side are separated for each block in which the surrounding wall is formed, and each of the separated blocks is separated. , Remodeling into independent multiple folding machine.
Thereafter, as a third step, the underground pits are respectively excavated by the plurality of converted bent shield excavators, and as a result, the branched underground pits can be separately excavated. In the first invention of this application, in particular, "the rear end of each surrounding wall formed by each front trunk cylindrical outer wall and each front trunk shielding wall, each rear trunk cylindrical outer wall, and each rear Along with the front ends of the respective surrounding walls formed by the torso shielding wall are rotatably fitted to each other,
A bent seal is provided between the front end of each of the surrounding walls and the rear end of each of the surrounding walls. " Can prevent earth and sand, groundwater, etc. from entering the shield body. In the second stage of converting each separated block into a plurality of independent mid-bend shield excavators, such a structure is provided. In addition, the structure of the bent portion is almost completed in advance, and the remodeling does not require complicated work.
Further, in the third stage of excavating the underground pit by each of the plurality of modified mid-bent shield excavators, the plurality of branched underground pits are relatively moved by these mid-bend shield excavators more than the conventional shield excavator. Each can be excavated in a sharp curve. The second invention of this application relating to the shield method is equivalent to the invention relating to the shield method implemented by directly using the shield excavator configured as described in the above 1). The same operation and effect as described above can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments showing how the invention relating to the shield machine of this application and the invention relating to the shield method of this application are actually embodied will be described below with reference to FIGS. By describing, embodiments of the present invention will be clarified. FIG. 1 is a longitudinal sectional view showing a shield machine according to an embodiment of the present invention, and FIG. 2 is a view of the shield machine shown in FIG. FIG. 3 is a view along arrow II-II of the shield machine shown in FIG. 1 and also shows a state after division of the shield machine, and FIG. 4 is an arrow III- of the shield machine shown in FIG. FIG. 5 is an enlarged view of a bent portion in the shield machine shown in FIG. 4, and FIG. 6 is a diagram showing a process of separating a shield body into two blocks in a shield method according to an embodiment of the present invention. It is a cross-sectional view of the shield main body for description. The shield machine according to the embodiment of the present invention is similar to the shield machine described in the section of "Prior Art", in which a plurality of cylindrical tubular bodies having a missing portion on the peripheral wall are adjacent to each other. Are arranged in parallel with each other, and are configured based on a shield body having a cross section of an overlapping circular shape.

1 to 6, reference numeral 1 denotes a cutter head for excavating a face provided at a front portion of a shield body, and 2 denotes a shield provided with a cutter head 1 for excavating a face for excavating the ground. A front body 3 forming a front part of the main body, a rear body 3 having an assembly space 3f of a segment and forming a rear part of the shield main body, 4 a shield jack for propelling a shield main body composed of the front body 2 and the rear body 3; Reference numeral 5 denotes a center bending jack which is pivotally connected to the front trunk 2 and the rear trunk 3 to connect them.
A bent portion composed of a rear end portion, a front end portion of the rear body 3 and a center folding seal 7. The earth and sand, groundwater, and the like are formed between the rear end portion of the front body 2 and the front end portion of the rear body 3. A bendable seal for preventing intrusion, 8 is an erector that is installed across the assembly space 3f of the segment of the rear trunk 3 and assembles the segment, and 9 is a shield body that divides the shield body into an outer space on the digging side and an inner space for work. A bulkhead 10 as a sealing partition is a screw conveyor attached to the bulkhead 9 and serving as a discharging device for discharging excavated earth and sand. Shield jack 4
Are installed in the shield main body, and propell the shield main body while taking a reaction force at an existing segment (not shown). Similarly, a plurality of half-fold jacks 5 are installed in the shield main body, and a desired one of the plurality of middle-fold jacks 5 is extended and contracted with a stroke difference, so that the front trunk 2 is moved relative to the rear trunk 3. By rotating the shield main body, the shield main body can be bent.

As described above, the shield body of the shield machine according to the embodiment of the present invention is configured by arranging a plurality of cylindrical tubular bodies having a missing portion on the peripheral wall in parallel such that the missing portions are adjacent to each other. In this case, the front body 2 provided with the cutter head 1 at the front and the rear body 3 having the segment assembling space 3f are divided. To be more specific about this point, the front body 2 has a pair of cylindrical tubular bodies 2a, 2b having notches 2e, 2e in the peripheral wall arranged in parallel such that the notches 2e, 2e are adjacent to each other. Then, they are connected via the upper and lower constricted portions 2g to form an overlapping circular cross section. Similarly, the rear body 3 is formed by arranging a pair of cylindrical tubular bodies 3a and 3b having notches 3e and 3e in the peripheral wall in parallel so that the notches 3e and 3e are adjacent to each other, and forming an upper and lower constricted portion. 3
By connecting through g, the cross section has an overlapping circular shape. And the front body 2 having such a cross section overlapping circular shape
And the cylindrical body 2a, 2b on the front body side based on the rear body 3
Each of the missing portions 2e, 2e has a front body shielding wall 2c,
2d, and each of the missing portions 3 of the rear body-side tubular bodies 3a, 3b so as to follow the front body shielding walls 2c, 2d.
e and 3e are also provided with rear trunk shielding walls 3c and 3d, respectively.

In this embodiment, the front body shielding walls 2c, 2d
Are the bulkheads 9a, 9a as shown in FIG.
The cylindrical bodies 2a and 2b are each formed into a sealed section by extending to the position b. These front body shielding walls 2c, 2d
As described later, when the two cylindrical bodies 2a and 2b on the front trunk side are separated and remodeled into two independent half-folded shield excavators, the point that becomes a member constituting the half-folded portion 6 is the largest. Therefore, at least the rear ends of the cutouts 2e, 2e in which the center bent portion 6 is formed may be provided.
Similarly, the rear trunk shielding walls 3c and 3d also have the greatest role in that they become the members constituting the half-fold part 6 when remodeling into two independent half-fold shield excavators. What is necessary is just to provide so that the front end part of the notch parts 3e and 3e in which the center bending part 6 is formed may be shielded. In this case, the rear body shielding walls 3c and 3d are provided so as not to partition at least the segment assembly space so that the segments can be smoothly assembled in the assembly space 3f of the segments of the rear body 3. In this embodiment, the front-body shielding wall 2c and the rear-body shielding wall 3c are:
Each has an arc-shaped wall in cross section, and the other front body shielding wall 2
The d and the rear-body shielding wall 3d are formed so as to form a wall having an inverted arcuate cross section so as to accommodate the front-body shielding wall 2c and the rear-body shielding wall 3c, respectively. However, the shapes of the front-body shielding wall 2c and the rear-body shielding wall 3c and the front-body shielding wall 2d and the rear-body shielding wall 3d may be reversed. It may be formed as follows. When the front-body shielding wall 2c, which forms a wall having an arc-shaped cross section, is extended to the location of the bulkhead 9a and is provided over the entire missing portion 2e, a complete cylindrical body is used for the cylindrical body 2a from the beginning. It may be provided.

[0013] When forming a bent portion in the shield body,
The rear end of the surrounding wall formed so as to be surrounded by the front body shielding wall 2c and the peripheral wall of the front body side cylindrical body 2a, and the peripheral wall of the rear body shielding wall 3c and the rear body side cylindrical body 3a. And a surrounding wall formed so as to be rotatably fitted with a front end portion of a surrounding wall formed so as to be surrounded by the front body shielding wall 2d and the peripheral wall of the cylindrical body 2b on the front body side. The rear end of the wall and the front end of a surrounding wall formed so as to be surrounded by the rear trunk shielding wall 3d and the peripheral wall of the cylindrical body 3b on the rear trunk side are rotatably fitted. In this case, in this embodiment, the front end of each of the surrounding walls on the rear trunk side is inserted into the rear end of each of the surrounding walls on the front trunk side. May be inserted into the front end of each surrounding wall on the rear trunk side. Further, as best shown in FIG. 5, the front end of each of the surrounding walls on the rear trunk side is attached to the front end of each of the surrounding walls on the rear trunk side. Are provided between the rear ends of the surrounding walls. In this case, in the present embodiment, the middle bend seal 7 is attached to the front end of each of the surrounding walls on the rear trunk side. Conversely, the middle bend seal 7 is attached to the rear end of each of the surrounding walls on the front trunk side. The same effect can be obtained even if it is attached to the camera. The front body 2 and the rear body 3 forming the shield main body are constituted by a pair of cylindrical bodies 2a and 2b and a pair of cylindrical bodies 3a and 3b, respectively.
b, the erectors 8 are provided in pairs 8a and 8b, and the bulkheads 9 are provided in pairs as shown by reference numerals 9a and 9b, respectively. Similarly, a pair of screw conveyors 10 are provided. In addition, a pair of left and right cutter heads 1a, 1b
Can be rotationally driven so as not to interfere with each other.

Since the shield machine according to this embodiment has such a structure, when constructing an underground pit, first, as a first stage, the lower stage of FIG. 6 shown in FIGS. By excavating a face with the cutter head 1 while propelling the shield body with the shield jack 4 using a shield excavator having such a cross-sectional shape, a single underground pit having a wide width is excavated to a desired length. In that case, the underground pit can be excavated with a sharp curve by driving the center bending jack 5 as needed. In the process of excavating the underground pit, the segments are moved along the inner surface of
To assemble into an overlapping circular cross-sectional shape similar to the cross-sectional shape of the rear trunk 3. As described above, the front end of each of the surrounding walls on the rear trunk side and the rear end of each of the surrounding walls on the front trunk side are rotatably fitted to each other. Since the seal 7 is provided, even in the first stage of excavating this single underground pit, such a structure can prevent earth and sand, groundwater, and the like from entering the inside of the shield main body. Further, the missing portion 2 of the cylindrical body 3a, 3b on the rear trunk side.
In the case where the rear body shielding walls 3c and 3d are provided in e, especially when the segments are assembled by the erector 8 in the segment assembling space 3f, the rear body shielding walls 3c and 3d are provided so as not to partition the segment assembling space 3f. The segments can be smoothly assembled along the entire inner periphery of the rear trunk 3 without the walls 3c and 3d becoming barriers.

After excavating a wide underground pit of a desired length in the first stage, as shown in the middle stage of FIG. 6, as a second stage, the front body side cylindrical body 2a and the rear body side cylindrical body are excavated. The body 3a and the front body-side cylindrical body 2b and the rear body-side cylindrical body 3b are separated together with the bulkheads 9a and 9b and separated into blocks each having a surrounding wall formed therein, and two independent mid-fold shield excavations are performed. Convert it to a machine. That is, as shown in the upper part of FIG.
A front-body-side cylindrical body 2b and a rear-body-side cylindrical body 3b provided with a front-body-side shielding wall 2d and a rear-body-side shielding wall 3d having an inverted arc-shaped cross section,
By fixing the additional shielding wall ₆₁ shaped to match the front torso for blocking wall 2d and rear body for blocking wall 3d respectively, the cylindrical body 2b
And it remodels so that the outer surface of the cylindrical body 3b may form a circumferential surface.
At the same time, with respect to the other front-body-side cylindrical body 2a and the rear-body-side cylindrical body 3a, the cylindrical bodies 2a, 3a that are not shielded by the front-body shielding wall 2c and the rear-body shielding wall 3c. A shield wall is provided at the missing part of the vehicle, and these outer surfaces are modified to form a circumferential surface. In this way, two independent mid-bent shield excavators are completed. In this case, of course, the shield jack 4 and the middle jack must be used so that the propulsion of the shield body and the mid-bend operation can be performed without difficulty in each mid-bend shield excavator. Add as many folding jacks 5 as needed. When performing such remodeling work, the front end of each of the surrounding walls on the rear trunk side and the rear end of each of the surrounding walls on the front trunk side are rotatably fitted to each other, and a middle fold seal is provided therebetween. Since the structure of the middle bend portion of the two independent mid-bend shield excavators is almost completed in advance, no complicated work is required for the remodeling.

After modifying the shield machine in the second stage,
As a third step, the cutter heads 1a and 1b and the shield jack 4 are separately driven to excavate underground wells respectively by using the remodeled two-folded shield excavator, and as a result, a plurality of branched underground wells are obtained. Can be drilled separately. In this case, by driving the center bending jack 5 as needed, the two branched underground tunnels can be excavated at a steeper curve than the conventional shield machine. As described above, according to the present embodiment, in the overlapping circular section shield excavator and the shield method implemented using the same, after excavating a single underground tunnel by the shield method, without complicated work, It is possible to switch so that a plurality of branched underground tunnels can be excavated by the mid-bend shield method.

In this embodiment, as a shield machine,
Although only an example of a mud pressure type shield excavator with a circular cross section is shown, the present invention is naturally applicable to this type of shield excavator of a muddy water type, and the model to which this is applied is not limited. In the present embodiment, as a shield machine having a shield body formed by arranging and combining cylindrical bodies in parallel, only an example of a shield machine in which two cylindrical tubular bodies are combined is shown. However, the present invention can naturally be applied to a shield machine in which three or more cylindrical tubular bodies are connected. Further, the plurality of cylindrical bodies may have a rectangular cross-sectional shape, and the shield body may have a rectangular cross-sectional shape. As long as the shield excavator has a shield body having an outer shape that is arranged and connected in parallel so as to be adjacent to each other, the present invention can be applied to any type of machine.
In this embodiment, only an example of a shield machine in which cylindrical bodies are connected in the left-right direction is shown. However, the present invention can naturally be applied to a case in which cylindrical bodies are connected in the vertical direction.
In this embodiment, when excavating a single underground pit with a wide width using an overlapping circular section shield excavator, the shield body can be folded in the middle. It is only necessary to make it possible to excavate the shield body using the center-bending shield method, and to enable the shield body to be folded during excavation with the overlapping circular section shield excavator,
It is not an essential requirement for the present invention.

[0018]

As is apparent from the above description, the first invention of this application relating to the shield machine and the second invention of this application relating to the shield method, respectively,
Since the technical means described in 1) and 2) of "Means for Solving the Problems" are employed, a shield excavator having a shield body in which a plurality of cylindrical bodies are connected in parallel and such a shield excavator are provided. After excavating a single underground tunnel using the shield method, a switch is made so that multiple branched underground tunnels can be excavated using the mid-bend shield method without complicated work. be able to. In addition, when the rear body shielding wall is provided in the missing portion of the cylindrical body on the rear body side, particularly, since it is provided so as not to partition the segment assembly space, the segment assembly space is excavated when excavating a single underground pit. When assembling segments within
The segments can be assembled smoothly along the entire inner periphery of the rear trunk without the rear trunk barrier becoming a barrier.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a shield machine according to an embodiment of the present invention.

FIG. 2 is a diagram showing the shield machine in a state where the shield machine has been divided, as viewed in the direction of arrows II in FIG. 1;

3 is a view of the shield machine shown in FIG. 1 along arrow II-II and also shows a state after division of the shield machine.

FIG. 4 is a cross-sectional view of the shield machine shown in FIG. 1, taken along the line III-III.

FIG. 5 is an enlarged view of a center bent portion in the shield machine shown in FIG.

FIG. 6 is a cross-sectional view of the shield main body for illustrating a step of separating the shield main body into two blocks in the shield method according to the embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 cutter head 2 front body 2a, 2b front body-side cylindrical body 2c front body shielding wall having an arc-shaped cross section 2d front body shielding wall having an inverted circular cross section 2e missing portion 3 rear body 3a, 3b rear body Side cylindrical body 3c Rear-wall shielding wall having an arc-shaped cross section 3d Rear-wall shielding wall having an inverted arc-shaped cross section 3e Missing portion 3f Segment assembly space 4 Shield jack 5 Center bent jack 6 Center bent portion 6 ₁ Additional Shield wall 7 Folded seal 8 Electa 9 Bulkhead

Continued on the front page (72) Inventor Miya Kiyoshi 2-3-3 Kandaji-cho, Chiyoda-ku, Tokyo Co., Ltd. Obayashi-gumi Tokyo Head Office (72) Inventor Yoshihiro Tanaka 2-3-3 Kandaji-cho, Chiyoda-ku, Tokyo, Ltd. Obayashi Tokyo head office

Claims (6)

[Claims] 1. A shield body having an outer shape formed by connecting a plurality of cylindrical bodies having a missing part in a peripheral wall in parallel so that the missing parts are adjacent to each other, and a front part of each of the plurality of cylindrical bodies. Each has a cutter head, and has a segment assembly space in the rear part of the shield body, and after excavating an underground pit of a predetermined length, separates a plurality of cylindrical bodies into at least two blocks and excavates an independent middle bent shield excavation In a shield machine to be modified into a machine, the shield body is divided into a front body provided with a cutter head in front and a rear body having a segment assembly space, and at least one of the missing parts of the cylindrical body on the front body side A front body shielding wall that shields at least the rear end portion with a missing part adjacent to the front body is provided, and at least a part of the rear body side cylindrical body is provided so as to follow each of these front body shielding walls. Previous After shielding the end part, a trunk wall is provided so as not to partition the segment assembly space,
A rear end of each surrounding wall formed by each front fuselage shielding wall and the peripheral wall of the cylindrical body on the front trunk side, and formed by each rear trunk shielding wall and a peripheral wall of the cylindrical body on the rear trunk side. And the front ends of the surrounding walls are rotatably fitted to each other, and a center-fold seal is provided between the front end of each of the surrounding walls and the rear end of each of the surrounding walls. Shield machine. 2. A first step of excavating an underground pit of a predetermined length by the shield machine according to claim 1, and after completion of the first step, a plurality of cylindrical bodies on a front trunk side and a rear trunk side are formed. Separate for each block in which the surrounding wall is formed, and separate each separated block,
The underground pit is constructed through a second step of converting into a plurality of independent bent-shield shield excavators and a third step of excavating each of the underground pits using the converted plurality of bent-shield shield excavators. Shield construction method characterized by the following. 3. The shield machine according to claim 1, wherein each of the plurality of cylindrical bodies has a circular cross section, and the shield body has an overlapping circular cross section. 4. The shield machine according to claim 1, wherein each of the plurality of cylindrical bodies has a rectangular cross section, and the shield body has a rectangular cross section. 5. A shielding wall for a front trunk and a shielding wall for a rear trunk are characterized in that one of them has an arc-shaped wall in cross section and the other has a wall having a sectional shape capable of accommodating the wall. Claim 3
The shield machine described. 6. The shield excavator according to claim 3, wherein each of the front fuselage shielding wall and the rear trunk shielding wall has a cross-sectionally straight wall.