Patent ID: 7040712

Claim:
A shield tunneling method wherein a turnable body is arranged in a skin plate so as to be turned about an axis perpendicular to an axis of the skin plate, an excavating drive with a rotor being arranged in said turnable body so as to be movable backward/forward, a cutter device being ahead of said rotor of said excavating drive and being accommodable in the turnable body, the turnable body with the cutter device accommodated therein being turnable to direct the cutter device backward for replacement of damaged bits on the cutter device backward, characterized in that said cutter device comprises a center cutter supported by the excavating drive and a plurality of face plate type expansion cutters fitted to an outer periphery of said center cutter such that the cutters may be pivoted backward/forward, tunneling being effected by the cutter device with an assembly of the expansion cutters being expanded due to the expansion cutters pivoted forward, replacement of the damaged bits being effected such that the expansion cutters are pivoted backward to contract the assembly of the cutters into a size accommodable in a turning trajectory of the turnable body; and then the turnable body is turned to direct the cutter device backward for replacement of the damaged bits.