| 摘要 |
PROBLEM TO BE SOLVED: To reduce the cost and eliminate dangerous work by detecting the abrasion amount of a roller bit when it exceeds an allowable range to precisely determine the replacement time without a worker's entering a chamber. SOLUTION: Enclosing chambers different in depth from the knife edge are formed in plural places in the circumferential direction in the interior of a cutter edge of a roller bit 120 fitted to a cutter head 12 and fluorescent material 1 is enclosed in each chamber. As the natural ground is excavated, the cutter edge of each roller bit 120 is subjected to abraision with the passage of time, and when it reaches a designated abrasion amount, the fluorescent material 1 in the enclosing chamber flows out to mix in excavated sediment G, and is taken in a chamber 13 with the excavated sediment G to be discharged from a screw conveyer 14 to a belt conveyer 15. A fluorescent measuring device 2 is arranged on the belt conveyer 15, and the existence or absence of the fluorescent material 1 in the excavated sediment G is determined from the output signal. |
