| 摘要 |
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.
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