JP2001288994A - Structure of connecting-hole forming section in tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure of a connecting-hole forming section in a tunnel in which strength at the place of the formation of an opening section is increased by using a connecting member without reducing the internal space of the tunnel at the place of the formation of the opening section. SOLUTION: In the structure of the connecting-hole forming section, in which the first segment S1 forming the opening section O for branching a connecting hole and a segment S3 for poles and the second segment S2 are installed to the tunnel T and a pair of indented sections for inserting the connecting members 20 are formed extending over the inner circumferential surfaces of the first and second segments S1, S2, the first segment S1 is composed of the first segments 1, 2 for an opening and the first segments 3, 4 for an intermediate section and the second segment S2 of the second segments 5, 6 for the opening and the second segments 7, 8 for the intermediate section, the first segments 1, 2 for the opening and the second segments 5, 6 for the opening have thick sections 18, and the indented sections, into which the connecting members 20 are inserted, are formed to the thick sections 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for forming an opening for branching a communication hole in a tunnel having an inner wall formed by connecting a number of segments in a circumferential direction and an axial direction and connecting them together. A first segment, a pair of column segments arranged on the wellhead side and the face side of the opening to form the opening, and the first segment sandwiching the pair of column segments from the circumferential direction of the tunnel. A pair of second segments arranged on the wellhead side and the face side of the segment, and the pair of recesses are provided in the state where the opening is sandwiched in the circumferential direction of the tunnel with respect to the opening; And a connecting member is fitted into each of the pair of concave portions, and the first and second segments are connected to each other by the pair of connecting members. That relates to a structure of contact hole forming portion of the tunnel.

[0002]

2. Description of the Related Art Such a structure of a communication hole forming portion is carried out, for example, in a subway tunnel construction. The strength against such an external load is reduced. Therefore, in order to improve the strength, as described above, a concave portion is provided over the inner peripheral surfaces of the first and second segments, and a connecting member is fitted into the concave portion to improve the strength at the location where the opening is formed. The specific structure was as follows:
Conventionally, the one shown in FIG. 11 is known.

According to the known structure, a pair of opening first segments 1A and 2A constituting the first segment are
A plurality of rows are arranged in the axial direction of the tunnel T with the opening O for branching sandwiched from the circumferential direction of the tunnel T, and the wellhead side and the face side of the opening first segments 1A and 2A arranged in the plurality of rows. And a pair of opening second segments 5A and 6A constituting the second segment are arranged, and the opening first O-side edges of the opening first segments 1A and 2A and the opening second segments 5A and 6A. Is provided with a recessed portion 18A that opens to the opening O side. And a pair of opening second segments 5A located on the wellhead side and the face side,
6A, a column segment SA is disposed, and the connecting member 20A is connected to the first opening segments 1A, 2A.
A is fitted into the recessed portion 18A of A, and both ends of the connecting member 20A are fitted between the recessed portion 18A of the second opening segments 5A and 6A and the end surface of the column segment SA.

[0004]

According to the conventional structure shown in FIG. 11, the connecting member 20A receives the load from the opening first segments 1A and 2A and transmits it to the column segment SA. Requires high strength,
Therefore, the cross-sectional shape of the connecting member 20A becomes considerably large. Since it is necessary to fit the connecting member 20A having a large cross-sectional shape into the concave portion 18A formed at the edge of the first and second segments 1A, 2A, 5A, 6A for the opening, the first and the second for the opening are required. 2 segments 1A, 2A, 5A,
The thickness in the radial direction of 6A, that is, the thickness T3 is larger than the thickness T4 of the segment in the right half in FIG. Accordingly, there is a problem that the inner diameter of the tunnel at the location where the opening O is formed becomes small.

The present invention focuses on such a conventional problem, and its object is to use a conventional connecting member without reducing the internal space of a tunnel at a location where an opening is formed. It is an object of the present invention to provide a structure of a communication hole forming portion in a tunnel which can improve the strength at the opening forming portion.

[0006]

According to a first aspect of the present invention, as shown in FIGS. 1 to 6, a plurality of segments S are arranged in a circumferential direction and an axial direction and connected to each other. A first segment S1 arranged to form an opening O for branching a communication hole H in a tunnel T in which W is formed, and a wellhead side and a face side of the opening O to form the opening O. A pair of pillar segments S to be arranged
3 and a pair of second segments S2 arranged on the wellhead side and face side of the first segment S1 with the pair of column segments S3 sandwiched from the circumferential direction of the tunnel T, and the opening portion A pair of recesses 19 are provided over the inner peripheral surfaces of the first and second segments S1 and S2 with the opening O sandwiched in the circumferential direction of the tunnel T with respect to O. A connecting hole is formed in a tunnel in which the first and second segments S1 and S2 are connected to each other by a pair of connecting members 20 and the pair of connecting members 20,
A pair of first segments 1 and 2 for openings arranged adjacent to the opening O in a state where the first segment S1 sandwiches the opening O in the circumferential direction of the tunnel T; The second segment S2 is composed of a pair of second opening segments disposed adjacent to the column segment S3. The first and second opening segments are composed of segments 5 and 6 and intermediate second segments 7 and 8 disposed between the pair of second opening segments 5 and 6, respectively. In the state adjacent to O, a thick part 18 thicker than the thickness of the intermediate first segments 3 and 4 is provided, and the opening second segments 5 and 6 are adjacent to the column segment S3. , The intermediate second
A thick portion 18 thicker than the thickness of the segments 7 and 8 is provided, and a middle portion between the thick portions 18 of the first segments 1 and 2 for opening and the thick portion 18 of the second segments 5 and 6 for opening. And the middle portion of the recess is provided with the concave portion 19.

A characteristic feature of the second aspect of the present invention is that, as exemplified in FIG. 6, the pair of connecting members 20 are formed of a mold steel.

As shown in FIG. 6, the feature of the invention according to claim 3 is that, as exemplified in FIG. 6, the shape steel 20 is provided with a flange portion 20 a which abuts on a side wall 19 a of the recess 19 which is opposed to each other in the circumferential direction of the tunnel T. Where it is.

Note that, as described above, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the accompanying drawings by the entry.

According to the first aspect of the present invention, the first segment, which is arranged to form the opening for branching the communication hole, is formed so as to sandwich the opening. A pair of adjacent first segments for opening, and a first intermediate segment disposed between the pair of first segments for opening, with the pair of column segments interposed therebetween; A pair of second segments arranged on the wellhead side and the face side of the first segment are between a pair of opening second segments arranged adjacent to the column segment and the pair of opening second segments. The first segment for opening and the second segment for opening are adjacent to the opening and the segment for pillar, and the first segment for intermediate and the second segment for intermediate segment A thick portion that is thicker than the thick portion, and a recessed portion into which the connecting member is fitted is provided between the middle of the thick portion of the first segment for opening and the middle of the thick portion of the second segment for opening. Therefore, a connecting member having a relatively large cross-sectional shape is fitted into the concave portion provided in the middle of each thick portion, and the connecting member reliably receives the load from the first segment for opening to the column segment. Can tell. However, since each thick portion only needs to be provided in the pair of the opening first segment and the opening second segment, it is possible to prevent the inside diameter of the tunnel at the location where the opening is formed from becoming extremely small. .

According to the characteristic configuration of the second aspect of the present invention, since the pair of connecting members to be fitted into the recessed portions are made of a mold steel, for example, the connecting members are made of a solid body having a rectangular cross section. In comparison, while reducing the weight of the connecting member,
The load from the opening first segment can be effectively received and transmitted to the column segment.

According to the characteristic feature of the third aspect of the present invention, since the section steel as the connecting member is provided with the flange portions abutting on the side walls of the recessed portions facing each other in the circumferential direction of the tunnel, the flange having a large area is provided. By effectively using the portion, the load from the opening first segment can be more effectively transmitted to the column segment.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a structure of a communication hole forming portion in a tunnel according to the present invention will be described with reference to the drawings. This tunnel is used, for example, for subways, water and sewage systems, and various pipelines. As shown in FIG. 1 and FIG.
The inner wall W of the tunnel T is formed by arranging 1, S2, and S3 side by side in the circumferential direction and the axial direction of the tunnel T, and is connected to each other. The lateral wall of the tunnel T communicates with the tunnel T. An opening O for branching the communication hole H is provided. The segments S, S1, S2, and S3 are a normal segment S used to form a cylindrical inner wall W from a wellhead side to a face side, and the opening O is formed in the inner wall W. , A first segment S1, a second segment S2, and a column segment S3 used for the vehicle.

As shown in FIG. 3A, the first segment S1 has a pair of openings for opening arranged adjacent to the opening O in a state of sandwiching the opening O in the circumferential direction of the tunnel T. One segment 1, 2 and a plurality of intermediate first segments 3, 4 arranged between the pair of opening first segments 1, 2. The pair of opening first segments 1 and 2 are classified into two types, an opening first segment 1 having a short circumferential length and an opening first segment 2 having a long circumferential length. Two types of opening first segments 1 and 2 are arranged so as to sandwich the opening O, and an intermediate first segment 3 and an intermediate first segment between the pair of opening first segments 1 and 2. And a key segment 4 functioning as
2, 3, 4 are connected by bolts and nuts not shown,
Except for the opening O, the whole is configured to be partially annular.

Such a partially annular first segment S1
Is a plurality of rows in the axial direction of the tunnel T. In this embodiment, four rows are provided.
The first segments S1 which are arranged side by side and adjacent to each other,
They are connected to each other by bolts and nuts not shown. However, between the adjacent first segments S1, the first segment 1 for the opening having a short length and the first segment 1 for the opening having a long length are provided.
The segments 2 are arranged so as to be adjacent to each other and alternately, whereby the segments 1, 2, 3, and 4 constituting each first segment S1 are arranged in a staggered manner and connected to each other, An opening O is formed, and a pair of column segments S3 are arranged on the wellhead side and the face side of the opening O.

As shown in FIG. 3B, the second segment S2 is disposed in a pair on the wellhead side and the face side of the first segment S1 with the column segment S3 sandwiched in the circumferential direction of the tunnel T. Each of the second segments S2 also has a pair of second opening segments 5, 6 arranged adjacent to the column segment S3, that is, a second opening segment having a short circumferential length.
The segment 5 and the opening second segment 6 having a long circumferential length are arranged so as to sandwich the column segment S3,
A plurality of intermediate second segments 7 and a key segment 8 functioning as an intermediate second segment are arranged between the pair of opening second segments 5, 6, and these segments 5, 6, 7, 8, The column segment S3 is connected to the column segment S3 by bolts and nuts (not shown) so that the whole is formed in a ring shape. Further, also between the second segment S2 and the first segment S1, the second opening segment 6 having a longer length than the first segment 1 having a shorter opening becomes the first segment 2 having a longer opening. On the other hand, the short second opening segments 5 are arranged adjacent to each other, and the first and second segments S1 and S2 are also connected to each other by bolts and nuts (not shown).

The two types of opening first segments 1 and 2 are:
As shown in FIG. 3A, although there is a difference in the length in the circumferential direction, the structure is almost the same, and the two types of second segments 5 and 6 for opening are also the same. The first and second segments 1, 5 for the short opening are substantially the same, and the first and second segments 2, 6 for the long opening are also substantially the same. 1,
Details of 2, 5, and 6 will be described collectively with reference to FIGS. Note that (b) of FIG. 4 is (a) of FIG.
FIG. 5B is a cross-sectional view taken along a line B in FIG.
FIG. 4 is a cross-sectional view taken along a line B in FIG.

These segments 1, 2, 5, 6 are segments made of ductile cast iron having a large number of irregularities called a corrugated type, and a pair of left and right plate-like side walls 9, along the longitudinal direction. 10 and a plate-shaped front wall 11 and a rear wall 12 connecting the two side walls 9 and 10, and an outer peripheral wall 13.
As appropriate, a concave hole 14 is provided and concrete C is embedded. Then, both side walls 9, 10 and front and rear walls 11, 1
2 and the outer peripheral wall 13 are integrally connected and reinforced by a plurality of reinforcing ribs 15, and a plurality of bolt insertion holes 16 are formed in both lateral side walls 9, 10 and front and rear walls 11, 12. The outer peripheral wall 13 is provided with a grout injection hole 17 as appropriate.

Each of the segments 1, 2, 5, 6 has a thickness T1 on the front wall 11 side larger than a thickness T2 on the rear wall 12 side. ,
6, a thick portion 18 is formed on the front wall 11 side, and on the inner peripheral surface in the middle of the thick portion 18 in a state of crossing both lateral side walls 9, 10, in other words, each segment 1, In the state perpendicular to the longitudinal direction of 2, 5, 6
9 is formed, and an H-shaped steel 20 as a connecting member can be fitted into the recess 19. Then, the flange portion 20a of the H-section steel 20 is placed on the side wall 19a of the recess 19, that is, on a pair of side walls 19a facing each other in the longitudinal direction of each of the segments 1, 2, 5, and 6.
, And a plurality of bolt holes 21 are formed in the side wall 19a.

The first and second intermediate segments 3, 7 are:
Both the segments 3 and 7 have almost the same structure, and the front and rear walls located in the longitudinal direction are parallel to each other as shown in FIG. 7, and one of the front and rear walls is inclined as shown in FIG. There are two types, one adjacent to the key segments 4 and 8, and the front and rear walls are inclined. One is shown in FIG. 8 and the other is inclined in the opposite direction to FIG. But,
Since the other parts are almost the same, they will be described collectively with reference to FIGS. 7B is a cross-sectional view taken along the line B-B of FIG. 7A, and FIG.
FIG. 9 is a cross-sectional view taken along the line B-B in FIG.

These intermediate segments 3 and 7 are also usually
A pair of ductile cast iron segments called corrugated type, and a pair of left and right plate-like side walls 22 and 23 along the longitudinal direction.
And a plate-shaped front and rear wall 2 connecting the two side walls 22 and 23 thereof.
The front and rear walls 24 and 25 shown in FIG. 7 are parallel to each other, and one of the front and rear walls 24 and 25 shown in FIG. There are two types, one in which one of the front and rear walls 24, 25 is inclined, the one shown in FIG. 8 and the one inclined in the opposite direction to FIG. In either case, a concave hole 27 is provided in the outer peripheral wall 26, concrete C is embedded therein, and the concrete C is reinforced by a reinforcing rib 28, and both lateral side walls 22, 23 and front and rear walls 24, 24 are provided. 25, a plurality of bolt insertion holes 29 are formed, and a grout injection hole 30 is provided in the outer peripheral wall 26, and the thickness of the grout injection hole 30 is set to the first and second segments 1, 2, 5 for opening. , 6 rear wall 12
The thickness T2 is the same as the thickness T2 on the side.

First segment S1 and second segment S2
Key segments 4 and 8 have almost the same structure,
These key segments 4 and 8 are also made of a ductile cast iron usually called a corrugated type, and as shown in FIG. 9, a pair of left and right plate-like side walls 31 and 32 along the circumferential direction of the tunnel T, The front and rear inclined walls 33 and 34 connecting the two side walls 31 and 32 are integrally formed with an outer peripheral wall 35 and the like.
6, concrete C is embedded and reinforced by reinforcing ribs 37, and both side walls 31, 32 are provided.
A plurality of bolt insertion holes 38 are formed in the front and rear walls 33 and 34, and the thickness of the bolts 38 is the thickness T2 of the first and second segments 1, 2, 5, 6 for opening on the rear wall 12 side. And has the same thickness T2. Note that, in FIG.
FIG. 9B is a cross-sectional view taken along the line B-B of FIG.

The pair of column segments S3 is also made of a ductile cast iron usually called a corrugated type.
As shown in FIG. 5, a pair of left and right plate-shaped side walls 39, 40 along the longitudinal direction, plate-shaped front and rear walls 41, 42 connecting the both side walls 39, 40, and an outer peripheral wall 43 are integrally formed. In the outer peripheral wall 43, a concave hole 44 is provided, concrete C is embedded and reinforced by a reinforcing rib 45, and both lateral side walls 39, 40 and front and rear walls 41, 41 are provided.
A plurality of bolt insertion holes 46 are drilled in the hole 42, and a grout injection hole 47 is formed in the outer peripheral wall 43. The thickness of the grout injection hole 47 is the first and second segments 1, 2, 5, 6 for opening. Is the same thickness T1 as the thickness T1 on the front wall 11 side. In FIG. 10, (b) of FIG.
FIG. 11 is a sectional view taken along the line 2-2 in FIG.

Since the ordinary segment S has no direct relation to the gist of the present invention, a detailed description thereof will be omitted.
The normal segment S is also formed of a ductile cast iron segment or a key segment usually referred to as a corrugated type, and has a wall thickness of the first and second openings.
Thickness T on the rear wall 12 side in the segments 1, 2, 5, 6
2, and each segment can be connected to each other by bolts and nuts.

Next, a description will be given of a construction procedure for forming an opening O for the tunnel T and the communication hole H using the various segments described above. As before, using a normal segment S while drilling a tunnel, i.e., arranging a number of segments circumferentially and axially and connecting them together, the tunnel T Is formed. At the location where the opening O is formed, the column segment S3 is arranged on the wellhead side of the opening O and connected to the adjacent segment S by a bolt and a nut. In a state where the pillar segment S3 is sandwiched from the circumferential direction of the tunnel T, the opening second segments 5, 6 are arranged,
Using the bolts and nuts, the second segments 5, 6 for opening are connected to the adjacent segment S and also to the column segment S3. Then, the intermediate second segment 7 is arranged between the pair of opening second segments 5 and 6, and finally the key segment 8 is arranged, and these segments 7 and 8 are adjacent to each other by bolts and nuts. While being connected to the segment S, the segments 7 and 8 are also connected to each other.

After that, the first opening segments 1 and 2 are arranged adjacent to the second opening segments 5 and 6, but the second opening segment 5 having a shorter length has a longer opening second segment 5. One segment 2 is adjacent and the second for the long opening
A short first opening segment 1 is arranged adjacent to the segment 6, and each opening first segment 1, 2 is connected to the second opening segments 5, 6 using bolts and nuts.
And the intermediate first segment 3 and the key segment 4 are arranged between the pair of opening first segments 1 and 2 and the segments 3 and 4 are connected to each other by the bolts and nuts. It is connected to the segment 7 and the key segment 8, and each of the segments 3 and 4 is also connected. By repeating such operations, the first segments S1 are arranged in four rows, and the column segments S3 are also provided on the face side.
And the second segments 5 and 6 for opening, the second segment 7 for middle and the key segment 8 are arranged and connected, and the normal segment S is connected to the second segment S2. .

At this time, the first segments for short openings 1 and the first segments for long openings 2 are alternately adjacent to each other, and
By adjoining the long opening second segment 6 to the short opening first segment 1 and the short opening second segment 5 to the long opening first segment 2, the segments are connected in a staggered manner. Thus, an opening O is formed. As a result, the opening first segments 1 and 2 and the opening second segments 5 and 6 are arranged side by side in the axial direction of the tunnel T, and are formed on the inner peripheral surfaces of the opening segments 1, 2, 5 and 6. The provided recessed portions 19 are vertically arranged in a pair with the opening O sandwiched in the circumferential direction of the tunnel T, and the H-shaped steel 20 is fitted between the pair of recessed portions 19 respectively.

When the H-shaped steel 20 is inserted, as shown in FIG.
9, so as to be in contact with the side wall 19 a, and using the bolt holes 21 provided in the side wall 19 a, the opening segments 1, 2, 2, and 2 are bolted to the H-shaped steel 20 by bolts and nuts.
5 and 6 are connected. Thereby, the opening first segments 1 and 2 are arranged in a state where the thick portion 18 is adjacent to the opening O in a state where the opening O is sandwiched in the circumferential direction of the tunnel T, and the column segment is With the thick portion 18 adjacent to S3, the second segments 5, 6 for opening are disposed, and the first segments 1, 2 for opening and the second segments 5, 6 for opening are thick. Since the concave portion 19 is provided in the middle of the portion 18, the connecting member 20 having a relatively large cross-sectional shape can be fitted into the concave portion 19 provided in the thick portion 18. 18
Need only be provided in the first segments 1 and 2 for opening and the second segments 5 and 6 for opening, so that the inside diameter of the tunnel T at the location where the opening O is formed is prevented from becoming extremely small.

[Another Embodiment] (1) In the above embodiment, a pair of opening first segments 1 and 2 constituting the first segment S1 are formed of two different lengths.
Although an example in which the first segment 1 and the second segment 1 are configured with segments having the same length and the same structure can be used as the pair of first segments 1 and 2 for the opening, a pair of segments forming the second segment S2 may be used. The same applies to the opening second segments 5 and 6. Further, the pair of opening first segments 1 and 2 and the pair of opening second segments 5 and 6 are all segments having the same length and the same structure. It can also be configured. In addition, although the example in which the first segments S1 are arranged in four rows to form the openings O is shown, the number of rows in the first segments S1 is arbitrary, and the axial width of the tunnel T in the first segments S1 is reduced. By increasing the width, the opening O can be formed by the first segments S1 in one row.

(2) In the above embodiment, the opening and intermediate first segments 1 and 1 constituting the first segment S1
2, 3, 4, the opening and intermediate second segments 5, 6, 7, 8, and the column segment S3, which constitute the second segment S2, and the normal segment S are all called corrugated types. Although an example in which the segment is made of ductile cast iron segments is shown, some or all of these segments are segments other than corrugated type, for example, steel or cast iron having an outer peripheral wall and a plurality of main girders for reinforcement. The present invention can be implemented by replacing a segment or a concrete segment.

(3) In the above embodiment, the example in which the H-shaped steel is used as the connecting member 20 has been described. However, a solid rod or a hollow cylindrical body can be used. In this case, besides the H-shaped steel, various shapes such as a channel-shaped steel and an angle-shaped steel can be used.

[Brief description of the drawings]

FIG. 1 is a front view of a communication hole forming portion from the inside of a tunnel.

FIG. 2 is a perspective view of a communication hole forming part in a tunnel.

FIG. 3 is an end view of a first segment and a second segment.

FIG. 4 is a plan view and a sectional view of an opening segment.

FIG. 5 is a plan view and a sectional view of an opening segment.

FIG. 6 is a perspective view of a main part of the opening segment.

FIG. 7 is a plan view and a sectional view of an intermediate segment.

FIG. 8 is a plan view and a cross-sectional view of an intermediate segment.

FIG. 9 is a plan view and a sectional view of a key segment.

FIG. 10 is a plan view and a sectional view of a column segment.

FIG. 11 is a front view and a side view showing a conventional communication hole forming portion.

[Explanation of symbols]

 1, 1st segment for opening 3, 4 1st segment for intermediate 5, 6 2nd segment for opening 7, 8 2nd segment for intermediate 18 Thick portion 19 Recessed portion 19a Side wall of recessed portion 20 Mold steel as connecting member 20a Flange section of section steel H Connection hole O Opening S segment S1 First segment S2 Second segment S3 Column segment T Tunnel W Inner wall of tunnel

Claims (3)

[Claims] 1. A first segment arranged to form an opening for branching a communication hole in a tunnel having an inner wall formed by connecting a number of segments in a circumferential direction and an axial direction to each other, and the opening. A pair of pillar segments arranged on the wellhead side and the face side of the opening to form a portion, and a state in which the pair of pillar segments are sandwiched from the circumferential direction of the tunnel, And a pair of second segments disposed on both sides of the tunnel, with the pair of recessed portions being inner peripheral surfaces of the first and second segments while sandwiching the opening in the circumferential direction of the tunnel with respect to the opening. A connecting member is fitted into each of the pair of concave portions,
A structure of a communication hole forming portion in a tunnel in which the first and second segments are connected to each other by the pair of connecting members, wherein the first segment sandwiches the opening in a circumferential direction of the tunnel. A pair of opening first segments arranged adjacent to the opening, and a pair of opening first segments.
An intermediate first segment arranged between the segments, wherein the second segment is a pair of opening second segments arranged adjacent to the column segment and a pair of opening second segments. A first thickening portion that is thicker than a thickness of the first middle segment in a state where the first opening segment is adjacent to the opening. The opening second segment is provided with a thick portion that is thicker than the intermediate second segment in a state adjacent to the column segment, and the opening first segment has a thick portion. The structure of the communication hole forming part in the tunnel in which the recess is provided in the middle of the middle of the second segment and the middle of the thick part of the second segment for opening. 2. The structure of a communication hole forming part in a tunnel according to claim 1, wherein said pair of connecting members are made of a steel shape. 3. The structure of a communication hole forming part in a tunnel according to claim 2, wherein the steel mold has a flange part which comes into contact with a side wall of the concave part facing each other in a circumferential direction of the tunnel.