| 摘要 |
PROBLEM TO BE SOLVED: To adjust the quantity of an over-bit by exchanging excavation members when a bedrock consisting of a gravel layer and a rock layer is excavated. SOLUTION: A shield body 1 and a tail shield 2 are connected through a hydraulic jack 4, and a cutter head 3 is installed at a front end, thus constituting an excavator A. The cutter head 3 has an outside diameter approximately the same as the shield body 1, a surface oppositely faced to a facing is formed in a truncated cone shape composed of tapered surfaces 31 and a flat surface 32, and roller bits 33 supported by support members 36 are set up onto an outermost circumferential section. A spacer plate is mounted and demounted to and from the seat of the cutter head 3 and the support members are fixed, and the quantities of projection (the quantities of an over-bit) of the projecting ends of the roller bits 33 are adjusted. The roller bits having different diameters are installed selectively to the support members 36, and the quantities of the over-bit are adjusted. |
