| 摘要 |
PROBLEM TO BE SOLVED: To close a front surface in the direction of elongation even if a vertical shaft is not constructed on the arrival side of a small-cross-section tunnel group. SOLUTION: In this construction method for an underground structure, natural ground 8 is surrounded by the small-cross-section tunnel group 100 which is constituted by coupling side surfaces of a plurality of small-cross-section tunnels 1 etc. elongated in the same direction, and the underground structure is constructed by excavating the surrounded natural ground. Small-sized excavators 31 are housed inside a branched type shield machine 3 for use in the excavation of each of the pair of small-cross-section tunnels facing each other in the small-cross-section tunnel. One small-sized excavator 31A is started to perform spiral excavation; the other small-sized excavator 31B performs excavation between spiral tunnels 4A; the small-cross-section tunnel facing a gap between the two spiral tunnels 4A and 4B and a leading end of the small-cross-section tunnel is elongated and closes the gap, so as to cover an opened surface 101 of the small-cross-section tunnel group. COPYRIGHT: (C)2007,JPO&INPIT
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