PURPOSE: To connected pipes without discontinued sections in bending pipe laying by fitting a flexible collar between the sheath pipes on the side of a insertion port and the sheath pipes on the side of a reception port with one end of the collar externally fitted to the sheath pipes on the insertion port side and also the other end fitted to the sheath pipes on the reception side.

CONSTITUTION: A perforation pipes 1 comprises a main pipe 2 made of casting iron wherein sheath pipes 3 made of resin are insertedly arranged and mortar 4 charged around the sheath pipes 3 therein. Perforated pipes 1 are connected to each other with the reception port 5 of a perforated pipe 1 inserted by the insertion port 6 of another perforated pipe 6, with the shaft center inclined to each other, and a flexible collar 10 installed between the respective sheath pipes 3 on the respective sides of the insertion port 6 and the reception port 5. The perforated pipes 1 are connected to each other with the ends of the sheath pipes 3 of the first perforated pipe 1 externally fitted to the sheath pipes 3 on the side of the insertion port 6 of the second one and the other ends externally fitted to the sheath pipes 3 on the side of the reception port 5 of the third one. As a result, bending of flexible collars makes it possible to connect sheath pipes without discontinuity.