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Pragsattel/Löwentor Tunnel

The Pragsattel serves as an important traffic hub in the Stuttgart road network from the north towards the downtown area and into the Neckartal valley. The tunnelling schemes embraces the undertunnelling of the Pragsattel for through traffic on the B 10 with two 2-lane tunnel bores as well as changes to the road network in the vicinity. The tunnel tubes are some 720 m long, each with two lanes and emergency footpaths per direction. The tunnel was largely produced by cut-and-cover and furnished in accordance with the RABT 2003. In the Stuttgart urban area there are no diversion possibilities for the B 10 on account of the topographical situation. In order to build the tunnel far-ranging measures had to be taken for provisional rerouting of traffic so that as little interference was caused to the existing lanes during the construction measures as possible. Any alterations that were necessary for the lanes or the surface facilities of the Stuttgarter Straßenbahnen AG (SSB AG) were undertaken as required either at night or over the weekend. In addition extensive considerations were accorded the logistical handling of the construction scheme as the surrounding federal road network could not be negatively affected. The 2-cell tunnel cross-section took the shape of an open frame as the tunnel floor lay considerably above the groundwater level. The frame structure was founded on base piles. A 30 cm thick in situ concrete slab was required on the tunnel floor for static reasons. The tunnelling scheme is set in gypsum keuper in layers of the middle gypsum zone. Artificial fills were found towards the surface. They largely comprised stiff to semi-solid clay with foreign substances such as stones, sand or concrete and brick residues. In parts, however, rubble from the war with considerable amounts of bomb splinters was located. No duds were found although suspicions were raised on several occasions on account of advance investigations. The shoring and excavation work was supervised by qualified special firms in accordance with the bomb disposal service unit down to a depth of 6 m below the ground surface. The gypsum keuper layer was encountered there. The gypsum keuper was found mainly in weathered unleached state. In the foundation zone, however, very resistant, only slightly weathered gypsum keuper was discovered. As a result there was no need for a bored pile foundation in a part-section.

 

  • Country: Germany
  • Region: Baden-Württemberg
  • Tunnel utilization: Traffic
  • Type of utilization: Road Tunnel
  • Client: Regional Capital of Stuttgart, Foundation Engineering Office
  • Consulting Engineer: Ingenieurbüro Dipl.-Ing. Vössing GmbH
  • Test engineer: Dr.-Ing. Bornscheuer, Dipl.-Ing. Münzner
  • Construction monitoring: Ingenieurgemeinschaft IGBB (BGS Ingenieursozietät/Ing.-Büro Prof. Dr.-Ing. Bechert+ Partner)
  • Contractor: JV Ed. Züblin AG/Gebr. Fahrion KG Bauunternehmung GmbH/RMS Richard Mayer Straßen- und Tiefbau GmbH/ Züblin Spezialtiefbau GmbH
  • Main construction method: Open
  • Type of excavation: Cut-and-cover/Top cover construction method
  • No. of tubes: 2
  • Tunnel total length: 720 m (2 tubes), 660 m (cut-and-cover), 60 m (top cover method)
  • Contract Volume: 40 miII. Euro
  • Construction start/end: 2002 till 2006
  • Opening: 2006