The German rail network is continuing to undergo long-term expansion and upgrade and it is therefore appropriate that tunnel construction as well as many other aspects of rail infrastructure should be represented at the InnoTrans trade fair, to be hosted by Berlin, over 20-23 September.

But rail transport is an expanding sector internationally and therefore the trade fair draws interest from all over, especially after the postponement of the event from its originally scheduled date of 2020, then 2021, due to the covid pandemic.

A key partner in InnoTrans 2022, which is held at Messe Berlin, is STUVA which is organising its International Tunnel Forum to be held at the trade convention. Held over two days (21-22 Sep), the Forum this year has two themes as follows – tunnel renewal under rail operating conditions in Germany, Austria and Switzerland; and, the developing use of Building Information Modelling (BIM) in tunnels in Germany.

Many lines are being improved on the being improved on the German rail network, including Karlsruhe-Basel and Stuttgart-Ulm within the borders of the country. TBMs from Herrenknecht played key roles in much of the tunnelling work for the projects by rail authority Deutsche Bahn (DB).

Improvements are also planned to the cross-border route between Germany and the Czech republic, on the Dresden to Prague line. The improvements include many possibilities for major new tunnel construction projects.

Karlsruhe-Basel

Deutsche Bahn is advancing its plans to construct the Offenburg Tunnel on the Rheintalbahn line between Karlsruhe to Basel rail it is remodelling, in south west Germany. The improvement works for the entire line are to increase capacity, reduce journey times, and separate long-distance high-speed trains from more local as well as freight trains.

The twin-tube Offenburg Tunnel is to be approximately 11km and will be the longest of all existing and new rail tunnels along the route which is almost 200km long. It will be used mainly for freight traffic. Other tunnels on the route are Rastatt and Katzenberg. Public consultation was launched in July for the project by DB.

The new rail tunnel at Offenburg forms Lot 7.1 of the rail upgrade and will pass under a major freight yard, the west side of the city of Offenburg and a major highway where it reaches a maximum depth of approximately 25m. South of the city the tunnel alignment follows waterways and another major road before surfacing beyond a business park.

While cut and cover construction is involved in the project, the majority of tunnelling is to be executed by tunnel boring machine (TBM), driving northwards for logistical reasons. The single-track tunnels are to be connected by 15 cross passages, constructed at regular intervals and no more than 500m. Further underground works on the project will involve construction of 10 emergency exits.

Rastatt Tunnel is Lot 1.2 on the northern end of the upgrade route, located in the 24.3km long section from Karlsruhe to Baden-Baden. The tunnel is 4270m long and is closest to Baden-Baden. Passing under existing rail tracks, design and construction of the tunnel involved first use of Building Information Modelling (BIM). The construction works involved overcoming some particular tunnelling challenges, involving some segment displacement, said DB. The recovery works involved some re-routing of existing traffic and then open construction.

Main excavation works for Katzenberg Tunnel were completed by TBMs 15 years ago. The tunnel is just over 9km long.

Stuttgart-Ulm

Key redevelopment of the rail infrastructure in Stuttgart, including the orientation of the main deep station itself plus tying in associated underground works, are all part of the large scale improvement to the Wendlingen-Ulm route on the network. The works form part of one of the strategic axes in the high speed rail TEN-T network under development across Europe. This particular axis runs broadly west to east, from Paris to Budapest.

By the end of this year, the entire Wendlingen-Ulm line is expected to be fully commissioned and brought into service. Tests have been underway throughout the year so far.

The principal excavations and tunnelling works for this project were performed a few years ago, supporting the highly unusual radical realignment of the main rail station in Stuttgart plus construction of a number of major twin tube tunnels.

The twin tunnels closest to Stuttgart station are in the Filder section of the project. Tunnelling works constructed the approximately 9.5km long Filder Tunnel in two sections, with an intermediate cavern where the geology split. The single TBM used for the drives was also turned around as part of the works. Contractor was a JV of Porr, Hinteregger, Ostu-Stettin and Swietelsky.

Apart from Filder, further key tunnels built for the high speed section between Stuttgart and Ulm were located at Bossler, Steinbuhl, and Albvorland.

The Bossler twin tube tunnel was built by a combination of TBM and conventional tunnelling with shotcrete lining. The main excavations on the 8.8km long tunnel were completed in 2018. Main fit-out works began in late 2020. Contractor was the JV of Porr, Hinteregger, Ostu-Stettin and Swietelsky.

Steinbuhl Tunnel is almost 5km long and was constructed by conventional tunnelling.

The project also involved works for Albastieg Tunnel.

Tunnelling of the almost 8.2km long twin tube Albvorland Tunnel was performed by Implenia.

Dresden-Prague

Early planning work for the Dresden-Prague line upgrade is underway and is expected to include Germany’s longest rail tunnel, at 15km long, according to InnoTrans 2022 Report.

The Dresden-Prague line will be part a key part of another axis – this time a north-south axis – of the developing TEN-T high speed rail network across Europe. But unlike the works on Wendlingen-Ulm route, the massive Dresden-Prague project is very much still on the drawing board.

This particular north-south axis will link northern Germany – itself to be linked farther north by other projects to Scandinavia – to south east Europe. To help do so, the Dresden-Prague project is a strategic crossing to improve on the mountainous German-Czech border. The improved cross-border route is expected to call for a twin tunnel of at least 25km in length, potentially, a slight majority of which would be on the German side.

Improvement options on the Dresden-Prague project, though, range from combining both surface with some underground elements all the way up to having the link run entirely and continuously in tunnel below the Ore mountains.

With deep tunnels under high cover being a distinct possibility, early geological investigations are important and they have been underway since 2020, involving about 130 boreholes to depths of up to 400m in the first drilling campaign. The second campaign is currently being executed, to mid-2023, with some boreholes planned to reach depths of up to 500m.

The next InnoTrans trade fair is scheduled for 24-27 September 2024.