Lainzer Tunnel lot LT31 - tunnelling with side wall drifts in Vienna / Lainzer Tunnel Baulos LT31 - Ulmenstollenvortrieb in Wien

Tunnelling in inner-city areas demands a high level of safety and represents a great challenge for the responsible engineers. The challenges increase with the cross-sectional area of the excavation, with the density of building on the surface and with deteriorating quality of the geology, and are thus considerable for twotrack rail tunnel in the 12th and 13th districts of Vienna. The lot LT31 "Maxing" of the Lainzer Tunnel met this increased demand through tunnelling with side wall drifts. On account of the splitting of the project into two neighbouring lots, the lot LT31 can only be entered through two starting shafts. This results in enormous space restriction and difficulties having to be taken into account, particularly in the initial phase. It proved possible to make up construction delays by adapting the side wall drifts method in the form of a "parallel drive". The present report explains special features and difficulties, which have arisen in the course of tunnelling.