| 摘要 |
PROBLEM TO BE SOLVED: To provide a downward shield capable of preventing a collapse of the ground around a bottom panel concrete, capable of obtaining the sufficient water-cut performance, and capable of pulling the whole of a cutter up, and to provide a shaft constructing method using the downward shield. SOLUTION: This downward shield is provided with a sheath pipe 3, which is provided in a shield frame 1 slidably forward in the excavating direction to cover the periphery of the shield frame 2, and a cutter device 5 retractably provided in the shield frame 2 and to be removably connected to the sheath pipe 3 to project the sheath pipe 3 toward a position in front of the shield frame 2. COPYRIGHT: (C)2004,JPO
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