| 摘要 |
PROBLEM TO BE SOLVED: To provide an excavation casing capable of corresponding to a hard rock layer from a soft rock layer. SOLUTION: The excavation casing is constituted by providing a plurality of roller bits 1 consisting of a cantilever supporting roller 8 to the lower end of a casing 4 having a circular section driven into soil, each roller bit 1 inclines a rotary shaft 17 of the roller 8 arranging bits 83 on the side in the vertical direction along the direction of a radius of the casing 4, there is the excavation casing 6 storing the supporting section 16 in a projective plane of the roller 8 in the direction of force-fit of the casing 4, and the roller bit 1 comprises an outward roller bit 102 making the rotary shaft 17 of the roller 8 have a downward slope in the vertical direction and supporting the rotary shaft 17 by the supporting section 16 from the radial inside of the casing 4 and an inward roller bit 101 making the rotary shaft 17 of the roller 8 have an upward slope and supporting the rotary shaft 17 by the supporting section 16 from the radial outside of the casing 4. COPYRIGHT: (C)2005,JPO&NCIPI
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