In the new Stuttgart 21 rail construction project, injections to seal anhydrite-bearing rock had to be carried out in the 3,200 m long twin-tube Feuerbach Tunnel. This article explains the further development of the equipment and technology and the implementation of digitalisation of the grouting works.


The Feuerbach tunnel is an approximately 3,200-metre long twin railway tunnel and part of the Stuttgart 21 rail project. It connects the existing regional and intercity railway line in the north of Stuttgart to the city's new main station. It is currently under construction.

The tunnel runs through strata of the Gypsum Keuper. If water comes into contact with the anhydrite-bearing Gypsum Keuper, a swelling can arise. Consequently, the conventional tunneling is done without using water in these sections. Despite this, water can get through the excavation-disturbed zone to the dry, unleached Gypsum Keuper underneath it. If there is anhydrite-bearing rock in these areas, it can swell. Due to this, many tunnels incurred damage in the past, for example in the form of heaves, which can reach the surface of the ground even of deep-lying tunnels.

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