Breakthrough of the dual-mode 10.24m diameter Wirth TBM

A dual mode TBM designed by Wirth has reached its goal after a boring a distance of almost 4km. The machine excavated 330,000m³ of rock for a track-doubling project on the Frankfurt-Fulda section of the existing Schlüchtern railway in Germany. The breakthrough is a decisive step toward completing this technically challenging project.

The tunnel passes through the 'Distelrasen', a ridge near Fulda, that is a complex geological deposit of hard sandstone alternated in quick sequence with soft clay formations. For this excavation project, Wirth developed a special 'dual mode' TBM that was able to achieve good penetration rates in the alternating geological situations, while providing maximum operational safety. The 10.24m diameter machine is about 110m long and weighs more than 1,600 tonne.

The £190 million Schlüchtern Tunnel project requires construction of the new 4km long tunnel and refurbish the old parallel tube, and is part of a programme by Germany's national railway company Deutsche Bahn (DB) to restore its existing long-distance rail network and advance new extensions for high-speed train traffic.

Once electrical and mechanical services are installed, traffic will be routed in both directions through the new Schlüchtern Tunnel while the old parallel tunnel, built in 1914, undergoes complete refurbishment. When these operations are completed, the interim stage in the new tunnel will be dismantled and traffic will use both tunnels for single-track unidirectional traffic.

The traffic density in this sector of the DB network is high with as many as 260 train-passings per day. Following the refurbishment-new construction programme, both Schlüchtern tunnels will among the busiest rail tunnels in Germany.