Austria – Tunnel Excavation concluded for the new Lower Inn Valley Railway

Since 2003 the Lower Inn Valley Railway has been accorded a 4-track upgrade as the northern access route for the Brenner Base Tunnel. In mid-May 2009 the tunnel excavation work for the new Lower Inn Valley Railway had largely been completed. As a result more than 29 km of twin-track railway tunnels – mostly with evacuation tunnels and shafts – has been finished in carcass state. The development of the railway in the Tyrolean Unterland is forging ahead according to schedule and the new rail route will become operational in 2012.
As a first step the tunnels in the vicinity of the communities of Vomp, Terfens and Brixlegg were embarked on in 2003 and 2004 and the construction sections at Fritzens and Stans tackled in 2005, for which a number of special construction methods were applied. On account of the high groundwater level work often progressed using compressed air. Then in 2007, two tunnelling machines with 13  m cutterhead diameter began their work operating as hydro-shields – on account of the high groundwater level. Parallel to the mining and mechanised tunnelling operations, the construction of the Terfens gallery, tunnel sections via cut-and-cover and a 700 m long tunnel for accommodating existing railway tracks were embarked on, which have largely been successfully completed.
Europe’s currently biggest tunnelling machine used between Münster and Wiesing arrived at its target at the beginning of February 2009, six months ahead of schedule. Only 585 working days were required to drive the twin-track tunnel tube – given a daily rate of advance of almost 10 m in the prevailing soft ground, mainly in groundwater. The second tunnelling machine attained its goal in the Tyrolean Unterland at the end of April 2009.
Challenges were posed by the proximity to other infrastructural facilities, paying heed to nearby built-up areas and the influence of underground water and groundwater. For instance when undertunnelling the Inn, utility lines, the Inn Valley motorway, the existing rail route and the foundations of 2 bridges near Stans and Jenbach had to be tackled. The tunnels, which are lined with reinforced concrete segments, are to be provided with an in situ concrete shell by 2010 – with almost 10  km of them being equipped with a special fire protection shell. Then the tunnels are to be furnished with the rail technology (vibration measures, track, communication and signalling equipment, power supply/catenary lines and evacuation facilities). A 4-track junction is to be established at Kundl by 2011. With a total length of 40 km – 32 km of which run through tunnels – the new Lower Inn Valley Railway after it becomes operational in 2012 will provide an additional environmentally friendly rail link on the European high-speed network. 
G. B.