| 摘要 |
PROBLEM TO BE SOLVED: To reduce frictional resistance working on a propulsion pipe by forming a tunnel hole formed of viscous material, on the outer periphery of the propulsion pipe by an excavator at the tip to ensure a uniform void between the tunnel hole and the outer periphery of the propulsion pipe, and filling a lubricant in the void. SOLUTION: An excavator 1 is composed of excavating mechanism 2 equipped at the tip of an outer cylinder 4 of the excavator; a wide ring 3 fixedly provided at the front outer periphery of the outer cylinder 4; a primary injection hole provided at the rear end face of the wide ring 3, with a specified circumferential space; and an outer periphery of the outer cylinder 4. Simultaneously with the excavation of this excavator 1, viscous material 7 is filled from the primary injection hole to the outer periphery of the excavator 1, and the viscous material 7 is enlarged in diameter to form a self-supported tunnel hole 11 at the outer periphery of a propulsion pipe.
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