JPH05340200

PURPOSE:To drain surely leakage of water in a tunnel through a drain ditch and to promote heat insulation efficiency in the drain ditch to dissolve problems such as freezing of water in the drain ditch, etc. CONSTITUTION:In drainage construction of leakage of water in a tunnel having a drain ditch 10 with a U-shaped section in the internal wall of the tunnel, the front open face of the drain ditch 10 is covered to mount a seal member 16 with a U-shaped section to the inside of the drain ditch 10 with the open face as the back. The side walls of the seal member 16 are made to adhere to both internal walls of the drain ditch 10 mentioned above.