| 摘要 |
PROBLEM TO BE SOLVED: To provide a cutter head which is essentially for use in excavating hard ground and takes measures against soft ground such as clay soil as a reserve function. SOLUTION: The cutter head is comprised of a first excavating section for excavating hard ground such as a rock, and a second excavating section for excavating soft ground such as clay soil. When the hard ground is excavated, the first excavating section maintains an excavating position, and the second excavating section withdraws to a non-excavating position. On the other hand, when the soft ground is excavated, the second excavating section moves and progresses more frontward than the first excavating section with respect to an excavating direction, to thereby carry out excavation of the ground prior to the first excavating section. |
