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ILF Consulting Engineers has been working on the large-scale project Stuttgart 21 (S21) since being awarded a contract by the Deutsche Bahn, at the end of 2009, to carry out the construction supervision for various sections of the project. With the planned construction works, the entire floor plan of the Stuttgart Central Station will be rotated by approx. 90 degrees and laid underground. This requires the construction of numerous new interconnections and many modifications on existing lines in the inner-city area, as well as the construction of new tunnel sections as feeder lines to the future Stuttgart station.

ILF’s scope of services comprises the design sections 1.2 and 1.6a of the S21 project (see overview below), which are interconnected to the new central station by tunnels ending in the future high-speed track of the new Stuttgart–Ulm line, which is currently being constructed in the South of Stuttgart. In addition there are underground connections to the existing railway lines towards Untertürkeim and Obertürkheim in the East.

ILF’s experts have now been successfully involved in this large-scale project for more than 10 years and will continue to work on this project for some years to come. The commissioned services mainly comprise technical and construction contract-related services as the construction supervisor, railway operational services in the vicinity of the facilities in operation, as well as services for project completion including handover of the entire concrete and structural works prior to the commencement of works on the track bed structures being carried out by other contractors.

So far, a total of approximately 28 km of single-track tunnel tubes have been driven using mining methods (NATM) and tunnel boring machines (TBMs). The tunnel cross sections are approximately 8 to 9 m in diameter, with underground bifurcations as well as approximately 30 emergency connection structures. In addition, 3 large portal structures are being constructed using the cut-and-cover method, each approximately 300-500 m long with trough and rectangular cross-sections in partly confined conditions next to railway lines that are already in operation.

Currently, the last tunnel sections are being driven towards Obertürkheim. Parallel to this, the inner linings in all sections of the tunnels and the cut-and-cover works in the portal areas are nearing completion. The next major milestone is expected to be reached by mid-2021, which will comprise the initiation of the subsequent track works on several tunnel sections around Stuttgart.