| 摘要 |
PROBLEM TO BE SOLVED: To prevent soil and sand from being blocked when a preparatory cutter bit is used. SOLUTION: The preparatory cutter of a shield machine 1 provides a cutter spoke 13 radially extending on the cutter head 6 of the front, and a preparatory cutter bit 20 is provided to be projected and retracted on the center part of the width of the cutter spoke. The cutter bit 18 and the preparatory cutter bit 20 can be moved in the width direction and the advance direction of the spoke 13 without being adjoined, and soil and sand can flow smoothly. |
