| 摘要 |
PROBLEM TO BE SOLVED: To prevent the central portion of a cutter head from being stuck with cohesive soil. SOLUTION: In an ordinary drive, the central cutter 12 is positioned at the center of a cutter head 11, and the excavating work is performed by rotating both the center cutter 12 and an outer peripheral ring cutter 13 in one united body. If cohesive soil sticks to the surfaces of the central cutter 12 and the thrust of a shield boring machine or the torque of the cutter head 11 rises during excavation work, then the central cutter 12 is positioned to the outer side of the radial direction and the excavation work is performed. The central cutter 12 rotates at a peripheral velocity higher than that at the center position when it is located at a position deviated from the center of the cutter head 11, so that cohesive soil stuck can be removed. |
