Tunnel Farchant – Abdichtungs- und Entwässerungssystem

In the Tunnel Farchant near Garmisch-Partenkirchen for the first time in a German road tunnel a pressure controlled drainage system is used. With this system the high underground water pressure in the central area of the tunnel is reduced to a minimum pressure of 2.5 bar. This was possible by an installation of a rising pipe in the ventilation shaft of the tunnel, equipped with an overflow. By the reduction of the pressure load it was possible to do without an enlargement of the concrete lining as well as without a large-scale sealing system in the central area. The article presents the planning and undertaking of the sealing and drainage system, with special emphasis on alternative solution possibilities. Then the installations for maintenance of the pressure control installation are described. Finally the measuring devices, with which the functionality of the pressure control is checked, are presented.