| 摘要 |
PROBLEM TO BE SOLVED: To prevent slurry from infiltrating by improving sealability of a slide gap.SOLUTION: While a roller bit 31 is moved back into an in/out hole 37a of a holding cylinder 37 from an excavation position, a moving-back space of the roller bit 31 is filled with a filler from a filler supply pipe 59A through a slurry space 41 of the roller bit 31. After the roller bit 31 is moved back, an opening surface 37b of the holding cylinder is closed with a gate plate 51, the filler in the in/out hole 37a is discharged through a filler discharge tube 59B, and the atmospheric pressure is applied. Consequently, the gate plate 51 is pressed against the opening surface 37b of the holding cylinder 37 with the pressure difference between working face collapse earth pressure of the front of te gate plate 51 and the atmospheric pressure on the back of the gate plate 51 to compress a cutoff seal material 40, thereby hermetically closing the in/out hole 37a. |
