| 摘要 |
PROBLEM TO BE SOLVED: To provide a segment which improves its strength without increasing the thickness of the segment, or reduces the thickness without impairing strength or functions, thus improving comparative strength. SOLUTION: The segment S is of a box shape (four girder type) formed of seven walls composed of a pair of axils walls 1 and 2 which are arranged along a tunnel axis direction so as to face an adjacent segment in a tunnel periphery direction, a pair or more of almost fan-shaped peripheral walls 3 and 4 arranged along the tunnel periphery direction, a peripheral wall 5 arranged along the tunnel periphery direction to compose a tunnel wall, and a pair of vertical ribs 6 and 6 identical in shape with the peripheral walls 3 and 4. On the peripheral walls 3 and 4, flanges 3f and 4f are formed on the part that is opposite with regard to a tunnel radius direction to the part where the peripheral wall 5 is arranged, the flanges 3f and 4f projecting in the tunnel axis direction along the whole or almost whole of the tunnel periphery direction length of the peripheral walls 3 and 4. Thus, the segment S made of a ductile cast iron is constructed. COPYRIGHT: (C)2008,JPO&INPIT
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