| 摘要 |
PROBLEM TO BE SOLVED: To enable the execution of work with a low cost and less collapse of a face on a site, where a pipe channel including a large diameter and a middle diameter part can not be laid because of a difficulty of ground improvement due to a little overburden ground. SOLUTION: A pilot pipe 5 having a small diameter is propelled toward a start pit 10 with an excavator 12 installed in an arrival shaft 11. When the pilot pipe 5 reaches the start shaft 10, an enlarged head 21 is mounted on the top of the pilot pipe 5. The enlarged head 21 has a non-rotational head cylinder and a facing plate, wherein a shaft integrally formed on the facing plate is welded to the pilot pipe 5 so that the facing plate rotates with the driving force of the excavator 12, excavating earth with an excavation bit attached to the facing plate. A Hume pipe 7 is supported with the enlarged head 21 and is propelled toward the arrival shaft 11 as the Hume pipe is pushed forward by a thrusting jack 18 arranged in the start shaft 10, while the excavation bit excavates earth.
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