| 摘要 |
PROBLEM TO BE SOLVED: To efficiently jack pipes regardless of a bore diameter and length of a jacking pipe while being small-sized, easily move a push ring, reduce a cost accompanying construction of a starting shaft which can be made small as the result, shorten the number of construction days, and reduce load of workers. SOLUTION: A pair of retractable pushing devices for pushing jacking pipe in the starting shaft in an excavation direction are installed, and the next jacking pipe is hung from the upper side of the starting shaft to be installed between the pipe jacking pipes before starting with a pushing movable part front end of the pushing device. The detachable push ring transmitting push pressure force is locked by making contact with the rear end of the pipe jacking pipe on the movable part rear end of each pushing device. The movable part of each pushing device is advanced to jack the jacking pipe underground, and the movable part of each pushing device is retracted to an original position to remove the push ring from the movable part rear end of each pushing device to be re-locked to the front end. The movable part of each pushing device is advanced again to further jack the jacking pipe underground. COPYRIGHT: (C)2004,JPO&NCIPI
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