| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of reducing the friction of propulsion pipes which can be propelled for cutting smoothly all the time, with a low friction resistance and at a low power, which are easy and inexpensive to fabricate, and which can be smoothly propelled even in a ground consisting of alternate layers of gravels and boulders or cobbles, by reducing its bit resistance; to provide a device therefor. SOLUTION: When jacking pipes 52 of the required length are interconnected and buried into the ground while excavation is carried out from a starting shaft, an endless drive chain 4 is disposed at the connection between the required propulsion pipes 52 via an attached pipe 1 equipped with a guide groove 3, in such a way that the chain is capable of rotating back and forth circumferentially. Bits 5 are attached to the drive chain 4 at predetermined intervals. While the chain 4 is actuated to rotate circumferentially, a tail void 64 is cut by the bits 5 and softened to reduce the friction between the propulsion pipes 52 and the natural ground. COPYRIGHT: (C)2004,JPO
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