SHIELD EXCAVATOR

PURPOSE:To eliminate necessity of soil improvement work by forming an opening for excavation of a branch route in a shield plate of a tunnel excavator which has a branch shield excavator which has a built-in direction-changeover and by blocking the opening with concrete materials. CONSTITUTION:After a horizontal tunnel has been excavated to a specified position by a shield excavator 1 for a main line excavation, all bolts 21 are removed to release a branch line shield excavator 11. Then, both wires 33 that are tied to wire-tying pieces 32 are pulled by a winch and a rest 29 is moved until the center of a pin 30 coincides with the center axis of a concrete material 36, and the branch line shield excavator 11 is turned by 90 deg. while one of the wires 33 is being pulled, and a cutter disk 14 is faced to the plate surface of the concrete material 36. When the center axes of the concrete material 36 and the branch shield excavator coincide, a reaction force bearing is temporarily provided within the shield excavator 1, and shield excavation is performed by a shield jack. Then, the concrete material 36 is cut to advance toward outside.