THRUST REDUCING DEVICE FOR PROPULSION PIPE

摘要

PROBLEM TO BE SOLVED: To expand the void around a propulsion pipe during the jacking work so as to prevent an increase of propulsion resistance caused by the shrinkage of the void and to reduce thrust. SOLUTION: This propulsion pipe is a composite pipe formed with a concrete propulsion pipe body 1 and a steel protective pipe 2 applied on its outer periphery. A plurality of slits 5 and 5' are provided at the prescribed interval in the peripheral direction on the protective pipe 2, rubber lugs 7 and 7' inserted into the slits 5 and 5' are protruded from the inner diameter face side of the protective pipe 2, and their base parts 9 and 9' are fixed between the protective pipe 2 and the propulsion pipe body 1. Lubricant injection holes 13 and 13' are provided behind the lugs 7 and 7', and the void is expanded by the lugs 7 and 7'.