PURPOSE: To form a corrosionproof covering protection layer and to perform airtight holding by forming and vulcanizing a rubber base or synthetic resin cloth wound around the rubber based according to the shape and the size of a bent pipe part, and providing the bent pipe with a coupling part.

CONSTITUTION: In a protection tool 1, a joint part 2 and a straight pipe part 3 are integrally formed by using a molded product formed of chloroprene rubber having excellent ozone resistance and polyamide resin. A coupling part 4 has taper surfaces 6a and 6b superposed with each other at both end parts 5a and 5b, being the belly side and the back side, of the protection tool 1. A bent pipe part 14 is formed with an elbow joint 13 welded to a straight pipe 12 formed of a polyethylene lining pipe so that temperature shrinkage of the inverted siphon part of an embedded pipe extending through an abutment 11 and spanned between bridge beams when a gas conduit is installed in a manner to run over a channel is absorbed. An elbow coupling 13 for a double pipe formed with a bent part 14 formed with the elbow coupling 13 and a sheath pipe 15 secured to an extension-through part 11a of the abutment 11 is covered with the protection tool 1, which is used for prevention of the coupling 13 from contact with the sheath pipe 15.