Abstract: There is provided a double walled pipe having an inner pipe and an outer pipe which is movable relative to the inner pipe in a longitudinal direction of the inner pipe. Acting on only the outer pipe with a pipe jacking power makes it possible to bury the double walled pipe, without damaging the rear end of the inner pipe and also generating an internal stress on the inner pipe. Consequently, it is avoided such a situation that even in use pinholes, cracks, etc. occur on the inner pipe, and thus it is possible to expect an execution with higher reliability.

Abstract: There is provided a double walled pipe having an inner pipe and an outer pipe which is movable relative to the inner pipe in a longitudinal direction of the inner pipe. Acting on only the outer pipe with a pipe jacking power makes it possible to bury the double walled pipe, without damaging the rear end of the inner pipe and also generating an internal stress on the inner pipe. Consequently, it is avoided such a situation that even in use pinholes, cracks, etc. occur on the inner pipe, and thus it is possible to expect an execution with higher reliability.

Abstract: There is provided a double walled pipe having an inner pipe and an outer pipe which is movable relative to the inner pipe in a longitudinal direction of the inner pipe. Acting on only the outer pipe with a pipe jacking power makes it possible to bury the double walled pipe, without damaging the rear end of the inner pipe and also generating an internal stress on the inner pipe. Consequently, it is avoided such a situation that even in use pinholes, cracks, etc. occur on the inner pipe, and thus it is possible to expect an execution with higher reliability.

Abstract: A conduit comprised of double-wall pipes A is laid in the ground by the pipe-jacking method. Each of double-wall pipes A comprises inner pipe 1 and outer pipe 2 and is provided with sheath pipe 4 between inner pipe 1 and outer pipe 2 and with check valve 7. Winch 11 is mounted in tunneling machine 6. Wire 12 wound on winch 11 is inserted into sheath pipe 4 and the forward end of wire 12 is sent to start vertical shaft C through sheath pipe 4, and connected with cleaning member 24, injecting member F, and supply pipe 14. Cleaning member 21, injecting member F, and supply pipe 14 are moved in sheath pipes 4 by driving winch 7. When injecting member F is opposed to check valve 7, packing means 19, 20 are inflated to be brought into contact with the inside of sheath pipe 4 by which injecting member F is fixed to sheath pipe 4.

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.