Light Rail Dortmund, Lot S2/S3a

The Lot S2/S3a is an 820 m long part-section of the City of Dortmund's Stadtbahnlinie III, a new project. It is intended to replace the surface tram link from Dorstfeld via downtown Dortmund to Wickede. This section ran beneath the Rheinische Strasse from the Möllerstrasse to Kampstrasse Station. In addition to the 2 single-track tunnel tubes, the project also includes the roughly 135 m Langwestentor Station. As the conditions in the inner-urban area of Dortmund are most constricted, a 20 x 36 large and 14 m deep starting shaft was first constructed. This shaft was used for supplying all the material to the sections driven by mining means and was later incorporated in the station. The monocoque design of the single-track tunnel tubes represents a special technical feature of this construction lot. In the case of this single shell variant for the tunnel lining, the shotcrete support was rounded off by a steel fibre pumped concrete inner shell. Both shells were constructed in such a way that a monolithic bond was created and the shotcrete support was not installed merely as a temporary element but as a supporting one for the inner shell. Apart from its load-bearing function, the lining also serves the purpose of keeping groundwater and seepage water out. In order to avoid cracks resulting from intrinsic stress states on account of temperature deformations during the setting of the pumped concrete, a furnace cement CEM III A 42.5 was used to create the steel fibre concrete shell. Given a reduction in cement of so kg/m³ compared with the double-shell construction method, a temperature increase of less than 15 °C could be registered alongside a sufficient early strength. In order to obtain information pertaining to the bonding behaviour of the 2 layers, a test wall was set up near the starting shaft on which the conditions of the inner shell were simulated as far as possible. Thanks to the findings gained there relating to the increase in temperature and the bonding behaviour, it was possible to establish a concreting concept. The advantage of this monocoque construction method was that a smaller excavated cross-section was required thanks to the reduced overall shell thickness so that this special proposal won the day. In order to ensure that the required quality needed for this construction method was adhered to, the Ingenieurgesellschaft Prof Dr.Ing. B. Maidl, Dipl.-Ing. R. Maidl was also commissioned with providing advice during the execution of consulting in addition to the planning.

Country: Germany
Region: Nordrhein-Westfalen
Tunnel utilization: Traffic
Type of utilization: Underground, urban and rapid transit
Client: Stadt Dortmund, Stadtbahnbauamt
Main construction method: Trenchless
Type of excavation: Drill-and-blast
Lining: Shotcrete (single-shell shotcrete lining)
No. of tubes: 2
Tunnel total length: 820 m, including approx.135 m for the Westentor Station and 685 m of tunnel tubes
Cross-section: 2 x 34 m²
Construction start/end: 1997 till 1999