Tunnel link to the future Main Station under the former Railway Directorate
The DB Projekt Stuttgart–Ulm GmbH is making rapid progress with one of the technically most complex parts of the Stuttgart 21 project. The building of the tunnel at the north head of the valley crossing has progressed so far that according to the estimate of DB at the end of January, the ground could be backfilled about one year later.
Between the portal of the Feuerbach/Cannstatt Tunnels and the building of the former federal railway directorate, a tunnel link to the future Stuttgart main station is currently being built in cut-and-cover. Under the Jägerstrasse, which currently runs over a temporary bridge, part of the trough for the approach tracks has already been formed, steel fixed and concreted. The four approach tracks spread like a fan at the north head to the eight tracks in the station.
The Subsoil under the Railway Directorate has not moved significantly
The continuation of the trough then runs under the railway directorate, two thirds of which has been laboriously underpinned on large-diameter bored piles, and under the Heilbronner Strasse. For this purpose, a former urban transit tunnel located between the east facade of the railway directorate and the Heilbronner Strasse is currently being broken out. The Heilbronner Strasse itself (which had been relocated several times during the construction period) has already been diverted onto the slab over the future trough; the base slab and side walls will be constructed later. In order to be able to construct part of the base slab in the north head, two urban transit tunnels running beneath it had to be exposed along a length of 80 m and a width of 4 m under continued operation. Parts of these tubes have already been built over. At the west end of the north head, the structure of a short part of the culvert has already been completed.
The greatest technical challenge at the north head is the underpinning of the former federal railway directorate. Its north wing with a weight of 15 000 tonnes was successfully underpinned in stages and provided with new foundations and now projects over the excavation for the north head. The building is supported on large-diameter bored piles. The installed hydraulic presses serve to compensate movement in the ground. No significant movements have been measured so far. In the second half of 2019, the load from the former railway directorate will be reloaded onto the trough, which should be ready by then. The handover of the former railway directorate to an investor is planned for early 2020.