SHIELD EXCAVATOR

PURPOSE:To construct a curve section of a tunnel freely by providing a center drum frame provided with a curved surface between a front drum frame provided with a cutter to the front thereof and a rear drum frame assembling segments. CONSTITUTION:A center drum guide cylinder 7 provided to a rear drum frame 4 overlaps a center drum frame 3, and a front drum guide cylinder 10 provided to the center drum frame 3 overlaps a front drum frame 2. In the case of a straight line excavation, the rear drum frame 4 is connected to the center drum frame 3 with a connector 15 and, the front drum frame 2 is separated from a connector 17 of the front drum guide cylinder 10, an excavation center bent jack 19 is extended to advance. In the case of a curved line excavation, the connector 15 is separated, the connector 17 is connected to extend the jack 19 of the outside curved line, and is bent at a center bent curved surface 12. A reaction force receiving jack 23 is extended to advance. According to the constitution, the curved line section can be easily and freely executed.