Tunnel excavating process and tunnel excavator

摘要

Provided are a tunnel excavating process which can reduce pressure required in excavation and excavate under lower pressure than the prior art even if compressive strength of base rocks is high, and a tunnel excavator capable of suitably executing the process. A plurality of roller cutter groups are arranged at given intervals in an excavating direction and in a direction vertical thereto, and points of roller cutters belonging to each roller cutter group in contact with base rocks are located in the vicinity of a difference in level portion formed in the base rocks to excavate the base rocks. There is constituted a tunnel excavator 1 in which a plurality of roller cutter groups 3x are arranged at given intervals in an excavating direction and in a direction vertical thereto on a cutter head 2 having a substantially conical shape. A boring head 4 can be disposed coaxial with the cutter head 2 to bore a pilot tunnel 7. <IMAGE>