Importance

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Abstract

When laying a conduit comprised of double-wall pipes A, each of which comprises inner pipe 1 and outer pipe 2, the smooth propulsion of double-wall pipes is possible by injecting lubricant into a space between the outside of double-wall pipes and the ground on a scheduled line along which conduit B to be laid is divided into section, each having a given length based upon the distance over which the effect of the lubricant can be maintained. Lubricant is injected from the double-wall pipes which is to be positioned at the heads in the respective sections 1 to n of supply pipes 3 which are provided between inner pipe 1 and outer pipe 2 of double-wall pipe A. Supply pipes of double-wall pipe A which has been propelled are connected with supply pipes of a new double-wall pipe, wherein the number of supply pipes connected with each other is determined for the respective sections. Lubricant is supplied from the upstream side and from the downstream side of the propelling direction to double-wall pipes. After conduit B has been laid, back-filling material as a filler is supplied to supply pipes 3 so that a space formed between the outside of double-wall pipes 23 and the ground is filled with filler. Sheath pipes 23 are provided between inner pipes 1 and outer pipes 2. After conduit B has been laid, back-filling material, as inside-filling material, is supplied to sheath pipes 23 so that a space between the outside of double-wall pipes and the ground is filled with inside-filling material.

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First Claim