| 摘要 |
PROBLEM TO BE SOLVED: To enhance safety in the execution of work and reduce a construction period and construction costs, by enabling a bifurcated section to be surely connected in ground, without using a cut and cover tunneling method etc. concurrently employing an auxiliary construction method, or securing the great length of a merging section; and to enable construction to be surely performed even under high water pressure. SOLUTION: Branch-line tunnels 4 are constituted as three circular tunnels wherein two tunnel structures 10 with a diameter smaller than that of the branch-line tunnel 4 are annexed so that the positional relationship of bringing respective outer peripheral walls of the branch-line tunnels 4 and the two tunnel structures 10 into almost concurrent and partial contact with an outer peripheral wall of a main-line tunnel 2 at the point of merging with the main-line tunnel 2 can be established. After freezing treatment is applied to a section where the outer peripheral wall of the main-line tunnel 2 and the respective outer peripheral walls of the two tunnel structures 10 come into contact with one another, at a point where the maine-line tunnel 2 merges with the three circular tunnels, an opening communication section is opened by removing opposed wall sections of the main-line tunnel 2 and the branch-line tunnel 4. COPYRIGHT: (C)2006,JPO&NCIPI
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