METHOD FOR SUPPORTING NATURAL GROUND ABOVE TUNNEL BORING MACHINE

PROBLEM TO BE SOLVED: To avoid binding resulting from loosening of natural ground. SOLUTION: When a bag 30 is to be installed in a gap between the outer periphery of a rear shield part 13 and the excavated face 15 of the natural ground, a cord such as a rope is locked to one end of the bag 30 and is drawn into a through hole provided in the rear shield part 13 and is pulled from within the rear shield part 13, whereby the bag 30 is installed between the outer peripheral surface of the rear shield part 13 and the excavated face 15 of the natural ground. Thereafter, a fluid supply hose is connected to the bag 30 to expand the bag 30. When the upper and lower faces of the bag 30 expanded fill the gap between the outer peripheral surface of the rear shield part 13 and the excavated face 15 of the natural ground, temporary timbering for the excavated face 15 of the natural ground is constructed. The temporary timbering thus constructed makes it possible to avoid the binding of the tunnel boring machine 10 even if the natural ground is loosened at the stop of excavation during which the tunnel boring machine 10 is highly likely to be bound.