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Rennsteig Tunnel

The Rennsteig Tunnel with a length of 7,900 m is Germany's longest motorway tunnel. It forms the core of the "German Unity" transport projects in the Thuringian Forest. It is a part of the A 71 motorway, due to link up Erfurt with Schweinfurt 2 tubes are being driven, with a distance between axes of roughly 25 m, maximum overburden approx. 200 m. The Rennsteig Tunnel was originally planned as a chain of 3 tunnels. 2 of the valleys crossing the route were to be spanned by means of bridges. However, traffic safety reasons (change-over from light to dark, fog, black ice formation on bridges) and avoiding zones close to the surface with corresponding geotechnical difficulties resulted in the decision to build a deep-lying continuous tunnel. Further reasons for renouncing the tunnel/bridge solution were crossing the Brandleite Tunnel, a more than 100 year old 2-track railway tunnel and the 2 valleys with approx. 20 m overburden. The Brandleite Tunnel was passed under at a distance of 7 m. Apart from the main tubes, the structure comprises 13 crosscuts, 12 emergency bays as well as 2 caverns, which function as air interchange centres (cross-section 200 m², length 150 m), 2 waste air shafts (diameter 6.2 m, length 20 m) and an access tunnel (cross-section 30 m², length 300 m). In geological terms, the Rennsteig Tunnel passes through the Oberhafer and Beerberg fault-block in the central Thuringian Forest. The Permian rocks largely belong to the Oberhafer porphyry plate; sediments (tuffs, conglomerates, sandstones and clay stones) are embedded in the various porphyric effusions and intrusions. The ground is moderately hard to hard (compressive strength up to 200 MN/m² and in some cases, there is a high share of quartz present. The tunnel is to be largely driven by blasting, with ultra-modern equipment such as computer-controlled drilling rigs employed. Supporting is undertaken in accordance with the principles of the shotcreting method. In mainly stable ground, an unreinforced inner shell with umbrella seal (single-layer made of plastic membrane) is largely applied. The ventilating of the 2 two-lane tubes is undertaken via the air interchange centres: the tunnel air polluted by vehicles is suctioned off and expelled by means of a chimney while the fresh air is sucked in via ducts from the outside and blown into the running tubes by means of fans. In ventilation technical terms, there are 3 tunnels, each shorter than 3 km, to be dealt with. To the south of the Rennsteig Tunnel, the 2,750 m long Berg Bock Tunnel and the 1,058 m long Hochwald Tunnel are being built.

 

  • Country: Germany
  • Region: Thuringia
  • Tunnel utilization: Traffic
  • Type of utilization: Road tunnel
  • Client: DEGES Deutsche Einheit Fernstraßenplanungs- und -bau GmbH
  • Consulting Engineer: ILF
  • Contractor: Ed. Züblin AG, Wayss & Freytag AG
  • Main construction method: Trenchless
  • Type of excavation: Drill-and-blast
  • Lining: In-situ concrete
  • No. of tubes: 2
  • Tunnel total length: 7916 + 7878 m
  • Contract Volume: 331 Mio. DM
  • Construction start/end: August 1998 till approximately 2003
  • Opening: 2003