PROBLEM TO BE SOLVED: To enable preceding boring in parallel with TBM excavation by circumferentially movably providing a boring machine on the annular auxiliary working frame travelling on another rail and forwardly obliquely excavating a hole. ;SOLUTION: After a body mount a belt conveyor 3 through a gripper 2 and a carriage traction beam 8, a tunnel boring machine(TBM) hauls a succeeding carriage T to be excavated. In no interference therewith, another rail is provided in the outside, a boring machine 5 is circumferentially movably disposed on an annular auxiliary working frame 4 running thereon, the boring machine 5 on the auxiliary working frame 4 is fixed regardless of excavation of TBM body, and a preceding boring hole is excavated in inclination not exceeding 30 m in front of cutting. Clearance of approximately 7.7 m had better exist in the range of movement of the auxiliary working frame 4. Thus, TBM excavation and preceding boring are performed in parallel, and high speed excavation is enabled in the estimation of earth quality in front of cutting.;COPYRIGHT: (C)1998,JPO
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