| 摘要 |
PROBLEM TO BE SOLVED: To damage no shield jack by providing a cover member covering the exposure part of an oblong hole at the time when a gripper extends. SOLUTION: When a shield jack 9 is used to be jacked, excavation is performed while reaction force is taken on a structure rearward of a tunnel excavator by the shield jack 9. When a gripper 7 is used to be excavated, a gripper shoe 7a is extended toward a tunnel adit wall and excavation is performed while jacking reaction force is taken. When the gripper shoe 7a is extended, a part of an oblong hole 7b in which the shield jack 9 is penetrated in the gripper shoe 7a, the exposure part of the oblong hole 7b is covered with a cover member 10 by accompanying the extension of the gripper shoe 7a. Thus, a muck is sandwiched between the shield jack 9 and the gripper shoe 7a by the contraction operation of the gripper 7, and the shield jack is prevented from being damaged. |
