JPH09217599A - Large-cross-section tunnel and method for constructing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a large-cross section tunnel that is high in strength, while carrying out construction work smoothly for reductions in construction period and cost. SOLUTION: After a plurality of rectangular shield tunnels 20, 20,... are constructed at predetermined intervals in advance, circular shield tunnels 15 are constructed between the adjacent rectangular shield tunnels 20, 20 to construct a tunnel structure 11 in which the circular shield tunnels 15 and planar shield tunnels 16 are arranged alternately. Thereafter, the natural ground inside the tunnel structure 11 is excavated to form internal spaces 12, 13 therein. In this case, circular shield tunnels 15A are placed at the corners of the tunnel structure 11, the diameter of the circular shield tunnel 15A being greater than the thickness of the planar shield tunnel 16 and the diameter of the circular shield tunnel 15B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large cross section tunnel suitable for use in constructing a tunnel having a large cross section and having a rectangular cross section, and a method for constructing the same.

[0002]

2. Description of the Related Art As is well known, a shield construction method of excavating a ground with a shield excavator and constructing a tunnel having substantially the same diameter as the shield excavator behind the excavator is often used for construction of a tunnel. However, in the shield method, if a tunnel with a large cross section is to be constructed, the shield excavator used for the tunnel will naturally become large, and as a result, manpower and cost will be reduced in all aspects such as manufacturing, transporting and assembling the shield excavator. It becomes bulky.

For this reason, in recent years, a method of forming a large-sized tunnel structure from these small-diameter tunnels by constructing a large number of small-diameter tunnels along the shape of the large-section tunnel has been developed.

By the way, particularly when an attempt is made to construct a large-section tunnel having a large space inside, a tunnel structure 1 having a circular section is constructed as shown in FIG. Since the tunnel structure 1 is formed larger than the space S, the large-section tunnel T is formed.
If the site required to construct the building is large and the cost is high, or if the site cannot be secured, the space S with a predetermined size is required.
There is a problem that it is impossible to form.

Therefore, as shown in FIG. 9, if a large cross section tunnel T'having a rectangular cross section is constructed, a space S having a predetermined size is formed.
It is sufficient to secure the minimum required land for forming
Since the cost can be reduced, various construction methods have been developed for constructing such a large-section tunnel T ′ having a rectangular cross section.

[0006]

However, the conventional large-section tunnel and the method for constructing the same as described above have the following problems. When constructing the tunnel structure 2 of the large-section tunnel T ′ having a rectangular cross-sectional view as shown in FIG. 9, the horizontal section 2a and the vertical section 2b forming the four sides of the tunnel structure 2 are respectively cross-sectionally viewed. After being assembled in a square shape, it is necessary to connect the horizontal portion 2a and the vertical portion 2b adjacent to each other at the joint portion A. To this end, as shown in FIG. 10 (a), after the horizontal portion 2a and the vertical portion 2b of the tunnel structure 2 are constructed separately, first, the ground G1 between these horizontal portion 2a and the vertical portion 2b is removed. Ground improvement using chemical injection or freezing method. Then, as shown in FIG.
The connecting portion earth retaining material 3 that was incorporated at the end of the construction of a is extruded toward the vertical portion 2b. Then, after the connecting portion retaining material 3 reaches the vertical portion 2b, the segments 4 of the horizontal portion 2a and the vertical portion 2b are removed, and the connection bracket 5 is attached to the vertical portion 2b. In this way the horizontal part 2
After the a and the vertical portion 2b are integrally connected, as shown in FIG. 10 (c), the reinforcing bars 6 and the like are arranged inside and the concrete 7 is poured to complete the tunnel structure 2.

In such a construction method, first, the connection portion retaining material 3 is extruded. When the horizontal portion 2a is constructed, a back filling material such as mortar is injected into the outer periphery thereof. Therefore, it is difficult to extrude the connection portion retaining material 3. In addition, in order to stop the joint portion A from water and increase its strength, the ground is improved by injecting a chemical solution or a freezing method. Needless to say, such ground improvement is time-consuming, costly, and complete. It is difficult to obtain the water blocking effect. Furthermore, when connecting the horizontal portion 2a and the vertical portion 2b, the ground of the joint portion A is excavated and the reinforcing bars are laid and assembled there. At this time, the horizontal portion 2a and the vertical portion 2b are respectively The segment 4 forming the side surface must be partially dismantled and removed. These segment 4
In the first place, since the tunnel space is held against the earth pressure and groundwater pressure of the natural ground, it is necessary to provide other supporting works when removing the segment 4, which is troublesome. Further, in order to install such a support and the like in a long section in the axial direction of the horizontal portion 2a and the vertical portion 2b, the support and support will be a large scale. It is necessary to do this, which also leads to a longer construction period and an increase in cost.

Further, in the large-section tunnel T'having a rectangular cross section as shown in FIG. 9, stress concentrates particularly on the corner where the horizontal portion 2a and the vertical portion 2b are abutted, so that this corner portion Although it is usual to provide a haunch portion for increasing the thickness of the member, it is difficult to provide a haunch portion in the above construction method, and there is also a problem that the strength of the large cross-section tunnel T ′ becomes low.

The present invention has been made in consideration of the above points. The construction is performed smoothly to shorten the construction period and reduce the cost, and to construct a large-section tunnel having high strength. An object of the present invention is to provide a large cross-section tunnel and a method for constructing the same.

[0010]

The invention according to claim 1 is
A tunnel having a large cross section is composed of a tunnel structure formed in a substantially rectangular cross section and a tunnel space formed inside thereof, and the tunnel structures are respectively arranged in an axial direction of the tunnel. A rectangular shield tunnel having a rectangular cross section and a circular shield tunnel having a circular cross section are alternately arranged so as to extend, and a rectangular shield tunnel and a circular shield tunnel adjacent to each other are partially overlapped with each other. It is characterized by being configured to be integrated.

According to a second aspect of the present invention, in the large-section tunnel according to the first aspect, the circular shield tunnel is arranged at a corner of the tunnel structure, and the diameter of the circular shield tunnel is the rectangular shield tunnel. It is characterized by being larger than the thickness of the tunnel.

The invention according to claim 3 is the invention according to claim 1 or 2
In the large cross-section tunnel described above, one or both of the upper surface and the lower surface of the tunnel structure are formed so as to be convex with the widthwise central portion thereof facing outward, and the circular portion is formed in the central portion. It is characterized by a shield tunnel.

[0013] The invention according to claim 4 is the invention according to claims 1 to 3.
In the large cross-section tunnel described in any one of the above 1, the curable filler is filled inside the segments forming the rectangular shield tunnel and the segments forming the circular shield tunnel.

According to a fifth aspect of the present invention, in a plurality of rectangular shield excavators in a sectional view, a plurality of rectangular shield tunnels are pre-constructed at predetermined intervals, and then the ground between the adjacent rectangular shield tunnels. By excavating a mountain with a circular shield excavator and constructing a circular shield tunnel behind it, a rectangular shield tunnel with a rectangular cross section extending in the axial direction of the tunnel and a circular shield tunnel with a cross section A circular structure having a large cross section is constructed by constructing a tunnel structure in which circular shield tunnels are alternately arranged adjacent to each other, and then excavating the ground inside the tunnel structure to form a space there. It is configured to build a tunnel, and when constructing the rectangular shield tunnel in advance, in the segment that constitutes the rectangular shield tunnel, It is characterized by the use of those recesses to avoid interference with the circular shield tunnel is formed at the overlapping portion of the circular shield tunnel serial trailing building.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of a large cross section tunnel and a method of constructing the same according to the present invention will be described below with reference to FIGS. Here, as the large-section tunnel to be constructed, for example, a tunnel having an upper and lower two-layer structure will be described as an example.

As shown in FIG. 1, a large-section tunnel 10 to be constructed has a tunnel structure 11 that resists earth pressure from the surrounding ground, and upper and lower 2 formed inside the tunnel structure 11. The inner space (tunnel space) 12, 13 is formed.

The tunnel structure 11 has side walls 11a, 11a on both sides positioned substantially in a vertical plane, and these side walls 11a.
The upper and lower surfaces 11b and 11c are provided between the upper and lower ends of the upper and lower portions 11a and 11a, respectively, and are provided between the intermediate portions of the side walls 11a and 11a to partition the upper and lower internal spaces 12 and 13. And a partition surface 11d, and has a substantially Japanese character in cross section as a whole. The tunnel structure 11 has a circular shield tunnel 15 having a circular cross section.
And flat shield tunnels (rectangular shield tunnels) 16 having planes parallel to each other are arranged alternately in the circumferential direction, and these are integrated. The circular shield tunnel 15 has a larger diameter than the thickness of the flat shield tunnel 16. Furthermore, the circular shield tunnel 15A disposed at the four corners of the tunnel structure 11 and the portion where the plane shield tunnel 16 is joined on three sides has a larger diameter dimension than the shield tunnel 15B of the other portion. Things have been adopted. Also,
The upper surface 11b and the lower surface 11c of the tunnel structure 11 are each configured to have a convex shape with the circular shield tunnel 15B as an apex toward the outside.

In the tunnel structure 11 as described above, reinforcing bars 18 are arranged around the entire circumference thereof, and concrete (hardening filler) 19 is cast inside the reinforcing bars 18. . Here, the reinforcing bars 18 are not only arranged so as to be continuous in the cross-sectional direction of the tunnel structure 11, but also at the four corners of the tunnel structure 11, diagonal reinforcing bars 18a extending obliquely inside thereof are provided. It is arranged.

The radial dimension of the large-section tunnel 10 is, for example, a circular shield tunnel 1 having a large diameter in which the internal spaces 12 and 13 are about 15 m wide and 11 m long, respectively.
5A outer diameter of 5.5m, small diameter circular shield tunnel 1
The outer diameter of 5B is 3.5 m, and the thickness of the plane shield tunnel 16 is about 3 m.

Next, a method of constructing such a large section tunnel 10 will be described. For this, first, the plane shield tunnels 16, 16,
.. are formed, rectangular shield tunnels 20, 20, ... Are constructed in advance as shown in FIG. As shown in FIG. 3, in order to construct each rectangular shield tunnel 20, a rectangular hole 22 is drilled in the ground with a cutter 21a provided in a shield excavator 21 having a rectangular cross-section, and first, behind it. Assemble the segments 23, 23, .... As shown in FIG. 2, each segment 23 has two flat surfaces 2 facing each other.
3a and 23a, and both sides of the flat plate portion 23a are substantially arcuate recessed portions 23b and 23b. Each recess 23
b is formed such that the radius of curvature of its arc is slightly larger than the diameter of the circular shield tunnel 15 (see FIG. 1) constructed laterally. After assembling such a segment 23, a backfill filler 25 such as concrete, mortar, fiber concrete or the like is filled between the excavated hole 22 and the outer peripheral surface of the segment 23. As a result, in each hole 22, the rectangular shield tunnel 20 having a rectangular cross section is formed.
Is constructed.

Next, as shown in FIG. 4, the ground between the rectangular shield tunnels 20 and 20 adjacent to each other is cut into a circular hole 2 using a circular shield excavator (not shown) in cross section.
Drill holes 6, 26, .... The shield excavator (not shown) used at this time has a diameter substantially the same as that of the circular shield tunnels 15A and 15B to be constructed here. At this time, rectangular shield tunnel 2
Along with the ground between 0 and 20, the backfill fillers 25 and 25 outside the recesses 23b and 23b of the segments 23 and 23 are also shaved at the same time to form holes 26. As a result, the back filling material 25 outside the concave portion 23b of the rectangular shield tunnel 20 is shaved, and a state is obtained in which the plane shield tunnel 16 is formed. As shown in FIG. 5, each hole 2 is
While excavating 6, the circular segments (segments) 27, 27, ... Are assembled behind the shield excavator (not shown). Then, by filling the outside of the assembled segment 27 with a backfill filler 28 such as concrete, mortar or fiber concrete, each hole 2
Circular shield tunnels 15A and 15B are constructed in the inside 6. As a result, a circular shield tunnel 1 having a circular cross section
5 and the plane shield tunnels 16 are arranged alternately in the circumferential direction.

Subsequently, the reinforcing bars 18 are arranged in the constructed tunnel structure 11. For this purpose, as shown in FIG. 6, the circular shield tunnel 15 that constitutes the tunnel structure 11 is formed.
A, 15B, plane shield tunnel 16, reinforcing bar 18
(See FIG. 1) Insertion hole 3 extending in the cross-sectional direction for passing
Form 0. For example, a boring machine, a core removing cutter, or the like is used to form each insertion hole 30. Then, as shown in FIG. 7, the reinforcing bar 18 is inserted into the formed insertion hole 30 and assembled. It should be noted that a joint fitting 31 may be used to assemble the reinforcing bar 18 as shown in this figure.
Alternatively, a lap joint may be used. When the insertion of the reinforcing bars 18 into the insertion holes 30 is completed, the space between the insertion holes 30 and the reinforcing bars 18 is filled with mortar, resin or the like, and these reinforcing bars 18 are integrated with the tunnel structure 11.

After that, as shown in FIG. 1, the circular shield tunnels 15A, 15 which constitute the tunnel structure 11 are formed.
B, the space in the segment 23 and the circular segment 27 of the plane shield tunnel 16 is poured and filled with concrete 19. Thereby, the tunnel structure 11 is completed.

After that, the ground inside the tunnel structure 11 is excavated and the internal spaces 12 and 13 are formed therein, thereby completing the construction of the large-section tunnel 10 having a predetermined shape.

In the large-section tunnel 10 described above, in the tunnel structure 11, the circular shield tunnels 15 and the plane shield tunnels 16 are alternately arranged adjacent to each other, and the circular shield tunnels 15 and the plane shield tunnels 16 adjacent to each other are formed. The parts are integrated with each other by polymerizing them. As a result, the circular shield tunnel 15 and the plane shield tunnel 16 are engaged with each other, so that the strong and stable large-section tunnel 10 can be formed. Further, concrete 19 is filled in the circular segment 27 that constitutes the circular shield tunnel 15 and the segment 23 that constitutes the plane shield tunnel 16. As a result, the rigidity of the tunnel structure 11 can be further increased.

Moreover, the circular shield tunnel 15A is arranged at the corner of the tunnel structure 11, and its diameter is larger than the thickness of the plane shield tunnel 16 and the circular shield tunnel 15B. . Further, the four corners of the tunnel structure 11 have diagonal reinforcing bars 18a extending obliquely inside thereof. As a result, a structure similar to that in which a haunch portion is provided at a corner of the large-section tunnel 10 is reinforced, and the high-strength large-section tunnel 10 capable of withstanding stress concentration is provided.
Can be configured.

In addition, the upper surface 11b of the tunnel structure 11,
The lower surface 11c is configured to be convex outward. As a result, the flat shield tunnels 16, 16 located on both sides of the upper surface 11b and the lower surface 11c are positioned diagonally with respect to the horizontal direction, so that the pressure acting in the vertical direction can be transmitted to the ground on the side surface. it can. As a result, the cross-sectional dimensions of the upper surface 11b and the lower surface 11c can be suppressed as compared with the case where the upper surface 11b and the lower surface 11c are simply provided horizontally.

In the method of constructing the large cross-section tunnel 10 described above, a plurality of rectangular shield tunnels 20, 20, ... Are pre-constructed at a predetermined interval, and then a circular shield is provided between the adjacent rectangular shield tunnels 20, 20. By constructing the tunnel 15 backward, a tunnel structure 11 in which circular shield tunnels 15 and plane shield tunnels 16 are alternately arranged adjacent to each other is constructed, and thereafter, the ground inside the tunnel structure 11 is excavated. Then, the internal spaces 12 and 13 are formed here. As a result, unlike the conventional large-section tunnel T'shown in FIGS. 9 and 10, smooth and efficient operation can be achieved without performing labor, cost, and time-consuming work such as joining the horizontal portion 2a and the vertical portion 2b. A large cross section tunnel 10 can be constructed. As a result, the effects of shortening the construction period and reducing the cost can be obtained.

Moreover, since the segment 23 of each rectangular shield tunnel 20 to be preliminarily constructed is formed with the recess 23b, when the circular shield tunnel 15 to be constructed later is constructed, it is already constructed on both sides thereof. Rectangle shield tunnel 20, segment 2 of 20
The recesses 23b and 23b of the holes 3 and 23 serve as guides for excavation of a circular shield excavator (not shown) and prevent the guides from coming off a predetermined excavation line to improve construction efficiency and construct a large-section tunnel. The quality of 10 can be ensured.

Although the large-section tunnel 10 has the upper and lower two-layer structure in the above embodiment, it may have a single-layer structure or a structure of three or more layers. Further, the cross-sectional shape is not limited to the perfect rectangular shape, and may be another shape such as a part having a curved shape. In addition, the upper surface 11b and the lower surface 11 of the tunnel structure 11
d, the circular shield tunnel 15 is arranged at the center of the partition surface 11d in the width direction. However, if the width of the large cross-section tunnel 10 is narrow, this may be arranged. The number of circular shield tunnels 15 may be increased. Further, if the segment 23 and the circular segment 27 forming the tunnel structure 11 are made of steel and integrated with the concrete 19 to be placed inside, the number of the reinforcing bars 18 can be reduced or omitted. It is also possible.

In the above embodiment, the rectangular shield tunnel 2 is used when constructing the large-section tunnel 10.
The circular shield tunnel 15 is constructed after 0 is constructed in advance. At this time, after the construction of all the rectangular tunnels 20 over the entire circumference of the tunnel structure 11, the circular shield tunnel 15 is constructed. When the construction of the rectangular shield tunnels 20, 20 adjacent to each other is completed, the construction of the circular shield tunnel 15 between them can be started. By adopting such a construction method, it becomes possible to further shorten the construction period. The same applies to the reinforcement of the reinforcing bar 18. Even if the entire circumference of the tunnel structure 11 is not completed, the reinforcing bar 1 is parallel to the construction of the circular shield tunnel 15.
It is also possible to perform the bar arrangement work of 8. Furthermore, the placing of the concrete 19 can also be performed in parallel with the progress of the reinforcing work of the reinforcing bar 18.

[0032]

As described above, according to the large-section tunnel according to the first aspect, the tunnel structure has rectangular shield tunnels and circular shield tunnels alternately adjacent to each other and adjacent to each other. The circular shield tunnel and the circular shield tunnel are partially integrated with each other and integrated. As a result, the rectangular shield tunnel and the circular shield tunnel are engaged with each other, and a strong large-section tunnel can be configured.

According to the large section tunnel according to claim 2,
A circular shield tunnel is arranged at the corner of the tunnel structure, and its diameter is larger than the thickness of the rectangular shield tunnel. As a result, a structure similar to that in which a haunch portion is provided at the corner of the large-section tunnel is reinforced, and a high-strength large-section tunnel that can withstand stress concentration can be configured.

According to the large section tunnel according to claim 3,
A circular shield tunnel is arranged on the upper surface or the lower surface of the tunnel structure at the center portion in the width direction, and the circular shield tunnel is configured to be convex outward. As a result, the upper and lower horizontal portions of the tunnel structure are inclined, and the pressure acting in the vertical direction can be transmitted to the ground on the side surface. As a result, the cross-sectional dimensions of the members forming the horizontal portion of the tunnel structure Can be suppressed.

According to the large section tunnel according to claim 4,
A curable filler is filled inside the segment forming the rectangular shield tunnel and the segment forming the circular shield tunnel. As a result, the rigidity of the tunnel structure can be further increased, and an even stronger large-section tunnel can be configured.

According to the method for constructing a large-section tunnel according to claim 5, after a plurality of rectangular shield tunnels are pre-constructed at predetermined intervals, circular shield tunnels are formed between the adjacent rectangular shield tunnels. A tunnel structure is constructed by constructing a trailing structure, and then the ground inside the tunnel structure is excavated to form a space here, thereby constructing a large cross-section tunnel, and a rectangle When constructing the shield tunnel in advance, the segment that forms the shield tunnel has a recessed portion that avoids interference with the circular shield tunnel. As a result, unlike the conventional large-section tunnel, a large-section tunnel can be constructed smoothly and efficiently without performing labor, cost, and time-consuming work such as joining the horizontal portion and the vertical portion. As a result, the effects of shortening the construction period and reducing the cost can be obtained. Moreover, since the structure is used in which the recess is formed in the segment of the rectangular shield tunnel to be constructed in advance, when the circular shield tunnel to be constructed in the subsequent stage is constructed, the segment of the rectangular shield tunnel constructed earlier on both sides of the segment is used. However, it serves as a guide during the excavation of the circular shield excavator, and it can be prevented from coming off the predetermined excavation line to improve the construction efficiency and ensure the quality of the tunnel to be constructed.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a large-section tunnel according to the present invention.

FIG. 2 is a view showing a method of constructing the large-section tunnel, which is a vertical cross-sectional view showing a state in which a rectangular shield tunnel forming a tunnel structure is pre-constructed.

FIG. 3 is a side sectional view and a plan sectional view showing a state where the rectangular shield tunnel is constructed.

FIG. 4 is a vertical cross-sectional view showing a state in which a hole for constructing a circular shield tunnel is excavated between the rectangular shield tunnels.

FIG. 5 is a vertical cross-sectional view showing a state where the circular shield tunnel is constructed.

FIG. 6 is a vertical cross-sectional view showing a state where holes for reinforcing bar arrangement are formed in the tunnel structure.

FIG. 7 is a vertical cross-sectional view showing a state where reinforcing bars are arranged in the tunnel structure.

FIG. 8 is a vertical cross-sectional view showing an example of a conventional large-section tunnel.

FIG. 9 is a vertical cross-sectional view showing an example of a conventional large-section tunnel having a rectangular cross section.

FIG. 10 is a process drawing showing the method of constructing the large cross-section tunnel shown in FIG.

[Explanation of symbols]

 10 Large Section Tunnel 11 Tunnel Structure 11b Upper Surface 11c Lower Surface 12, 13 Internal Space (Tunnel Space) 15 Circular Shield Tunnel 16 Flat Shield Tunnel (Rectangular Shield Tunnel) 19 Concrete (Hardening Filler) 20 Rectangular Shield Tunnel 23 Segment 23a Recess 27 circular segment (segment)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Miyazawa 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Fusao Kawakami 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Yasuhiko Shigeta 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Hiroyuki Kubo 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Hisao Arai 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Hisa Takenaka 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Invention Inoue Onoue 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Hiroyuki Hotta 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction (72) Invention Yoshihiko Akao 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Hiroshi Miyanami 1-2-3 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Minoru Imai Tokyo Shibaura 1-3-2, Minato-ku Shimizu Construction Co., Ltd. (72) Inventor Shimizu Ichiba 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Hidetake Ishizaki Shibaura, Minato-ku, Tokyo 1-3-2 Shimizu Construction Co., Ltd.

Claims (5)

[Claims] 1. A tunnel having a large cross section comprises a tunnel structure formed in a substantially rectangular cross section and a tunnel space formed inside thereof, wherein the tunnel structure is the tunnel. Respectively extending in the axial direction of, the rectangular shield tunnel having a rectangular cross section and the circular shield tunnel having a circular cross section are alternately arranged, and the rectangular shield tunnel and the circular shield tunnel adjacent to each other are provided. A large cross-section tunnel characterized by being configured by superimposing parts of each other and integrating them. 2. The large-section tunnel according to claim 1, wherein the circular shield tunnel is arranged at a corner portion of the tunnel structure, and the diameter dimension of the circular shield tunnel is larger than the thickness dimension of the rectangular shield tunnel. A large cross-section tunnel characterized by being also large. 3. The large-section tunnel according to claim 1 or 2, wherein one or both of an upper surface and a lower surface of the tunnel structure is formed so that a center portion in a width direction thereof is outwardly convex. And the circular shield tunnel is arranged in the central portion of the tunnel. 4. The large-section tunnel according to claim 1, wherein a curable filler is filled inside the segments forming the rectangular shield tunnel and the segments forming the circular shield tunnel. A large cross-section tunnel. 5. A shield excavator having a plurality of rectangular cross sections,
After constructing a plurality of rectangular shield tunnels at a predetermined interval in advance, excavate the ground between the rectangular shield tunnels adjacent to each other with a circular shield excavator in cross section, and place the circular shield tunnel here. By constructing a line, a tunnel structure is constructed in which a rectangular shield tunnel having a rectangular cross section and a circular shield tunnel having a circular cross section that extend in the axial direction of the tunnel are alternately arranged adjacent to each other. By constructing a space here by excavating the ground inside the tunnel structure, a tunnel having a large cross section is constructed, and when constructing the rectangular shield tunnel in advance, In the segments that make up the rectangular shield tunnel,
A method for constructing a large-section tunnel, characterized in that a recessed portion that avoids interference with the circular shield tunnel is formed in an overlapping portion with the circular shield tunnel to be constructed later.