The Brenner Pass forms a vital component of the Berlin-Nurnberg-Munich-Verona rail corridor, one of 14 priority projects identified by the EC for the realisation of the TEN-T (Trans-European Transport Network). The project will provide a much needed strengthening of the Munich–Verona rail link, which crosses Austria to link southern Germany and northern Italy.
On Austrian soil, there are two feeder line sections and the 55km long Brenner Base Tunnel section crossing the border into Italy. Upgrade works on the railway axis have already begun, with some sections operational, others under construction, in planning, or in a very preliminary project stage.
Northern feeder line
The Brenner Eisenbahn GmbH (BEG), Brenner Railway Company, was founded in 1995 to plan and build the additional two tracks of the Austrian section. The new tracks, with independent alignment, are being added to the existing two tracks of line in this area.
The Lower Inn Valley is narrow and densely populated, with towns lined up along the Inn River like a string of beads, so that 32 of the 40 total kilometres of new track on this first section of the feeder line will have to run underground. Two main roads, a motorway and the existing railway line all run through the floor of the same valley, through which the river Inn winds from one side to the other.
The new railway section now under construction between Kundl/Radfeld and Baumkirchen will accommodate train speeds of up to 250km/h, making the minimum curve radius normally 3000m, which is significantly straighter than other traffic carriers. The resulting route will make the new stretch frequently cross under roads, the motorway and the existing railway.
The A12 motorway and the existing Munich-Verona railway axis are extremely important international traffic routes as they constitute vital trade links between Central Europe and Italy, or as applicable, south-eastern Europe. For obvious reasons, construction of the new tracks under these existing infrastructures must be carried out without interrupting overland traffic.
Placing the majority of the route underground also helps maintain the landscape and almost fully precludes noise pollution. Plans call for links to the existing railway tracks in Radfeld, Stans and Baumkirchen to achieve an optimum integration of rail traffic.
The major eight construction lots of the first lower Inn Valley section can be seen in Table 1. From the east of the project area, trains will feed into the new railway at the border between the built up areas of Kundl and Radfeld (Figure 1). The entrance to the 13.078km long Radfeld-Wiesing tunnel will lie in the middle of the valley floor. The tunnel crosses under the community of Brixlegg and then leads to the Münster community after crossing under the river Inn, under the existing railway line, and three times under the motorway.
In the west, this tunnel ends in a solid rock formation called “Tiergarten” only to continue underground in the 4.312km long Wiesing-Jenbach tunnel, which crosses under the mentioned “Tiergarten”, the Jenbach train station and twice under the motorway. This is followed by the Stans link, which will enable an exchange between the new railway line and the existing one. The existing tracks will also be moved parallel to the motorway between Jenbach and Stans.
The tracks then begin to go underground on the approach to the new works that reach Stans. In future, long-distance trains will avoid the Vomp urban area via the 11.055km long Stans-Terfens tunnel. The tracks will then swing directly over to the embankment of the river Inn, roughly in the area of Terfens, before leading into the 1.33km long Terfens tunnel.
The 4.474km long Fritzens-Baumkirchen underground section will then run directly under the Fritzens train station. At the Baumkirchen link, the trains will travel either directly to the Innsbruck by-pass and onwards to the Brenner Base tunnel or continue towards Innsbruck.
Current status of the project
BEG started the major work on the new Inntal railway in October 2002, with substantial preparation work. The first tunnel construction lot was awarded and tunnelling of the Fiecht-Terfens section started in August 2003.
In the meantime, the Terfens tunnel lot and the first lot for the Radfeld–Wiesing tunnel have been awarded and are now under construction. Plans call for all of the work associated with the calls to tender for the six remaining main construction lots to be carried out in the next one-and-a half years. BEG expects to complete the first section of the feeder line towards the Brenner Base tunnel by 2010.
In the early spring of 2005 BEG plans to release the call for tenders for two large construction lots that involve tunnelling with large diameter slurry TBMs. At present the BEG is in the final planning procedure and still trying to optimise the size of the single bore double track tunnel. It has not yet been decided whether to combine both lots into one single lot.
Both lots are going to be built in similar ground conditions. The subsoil is composed of the highly porous gravel beds of the river Inn, into which alluvial fans cut in from the flanks of the Inn Valley. Silty flood plain sands, up to 5m thick, overlie this sequence. The ground water is situated approximately 3m to 5m below ground level.
The lengths of the sections to be tunnelled using a shield machine are 5.78km and 3.7km. The standard cross-section of the double-track tunnel with the escape paths requires a diameter of 12.16m including tolerances.
The geology encountered, with porosity values of up to 10-2m/s, requires a shielded TBM with a slurry-supported face. The possibility of boulders up to 1m in diameter and the need for advance grouting, constitute further general conditions for the shield design. The soil parameters encountered and the overburden conditions indicate a lining segment thickness of 500mm, a ring gap of 200mm and a 300mm thick inner lining as protection against fire. Therefore the total diameter of the TBM is currently planned to be 14.16m. Due to the high porosity of the ground, stringent demands have been placed on the composition of any additives.
The advance will be monitored using continuous surface deformation measurement, on the motorway and railway tracks where they are crossed.
For the duration of advance, a speed limit will be set up for railway traffic along the existing route and a track tamping machine will correct any minor settlement. In addition vibration measurement will be carried out to validate any monitoring data.
The combination of deformation measurement on the surface with constant monitoring of current advance data, with all data always being available on-line, should go a long way to ensuring a safe and risk-free tunnel advance.
The Münster – Wiesing lot (H3)
This lot has an overall tunnelling length of 6.463km and begins at a box to the west of Brixlegg, which will be constructed by the lot that started work in June of this year. The machine will start in a westerly direction and cross under the river Inn after 450m. After crossing the river, which is also the lowest point of the alignment, the TBM will make its way towards the target area near the so called “Tiergarten” hard rock formation.
On its way it has to pass under the existing railway line and cross the existing motorway twice. The 675m long drill and blast tunnel at the end of this lot will be constructed in advance so the TBM can either be dismantled in the tunnel, or carry on to bore the adjacent H4 lot.
The Jenbach – Stans lot (H4)
The new tracks will have to cross under the railway tracks at the train station at Jenbach and the A12 motorway at a very shallow angle. The building housing the Zillertalbahn AG’s headquarters, has to be tunnelled under, as do the two narrow gauge lines of the Zillertalbahn railway system, the two secondary railway tracks and the two main railway tracks of the Austrian Railway (ÖBB), and the motorway that follows shortly after them. On the whole this 3.7km stretch of tunnel will require the skills of a highly professional tunnelling company and their best workmanship.
Escape shafts and rescue tunnels
In case of emergency, escape shafts with an inner diameter of 8m and a maximum depth of 32m, connected to the main tunnel by 4.8m diameter rescue tunnels will be built. The rescue tunnels will be constructed by pipe jacking in combination with slurry TBM machines.
BEG expects to have the tender documents on the market by early spring 2005 and hopes to attract a wide range of European companies to bid for these lots, as they constitute some of the most interesting and challenging tunnelling to be done in the near future in Europe.
Related Files
Table 1: Construction lots of the first lower Inn Valley section
Ariel view of the Lower Inn Valley showing the line’s route
Cross section of a typical emergency escape shaft
Typical cross section
