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S-Bahn Rhein-Main, Baulos 15, Mainquerung

Construction Lot 15 - crossing under the Main - intersects the Main at river-km 36.4 and comprises a two-track tunnel section beneath the river. The thin overburden between the tunnel roof and the bed of the river of only barely 4 m resulting from the prescribed choice of gradient and route as well as the pronouncedly water-bearing, fissured tertiary horizon led to a decision in favour of the float-in and submerse method. The method for the construction of two tunnel elements - 61.50 and 62.00 m long - in the form of floating bodies in docks on the northern and southern banks of the Main and after flooding the docks to float them into position to a previously excavated channel set crosswise to the Main, submerge and connect them. The construction docks were then sealed off against the river, drained and deepened to act as construction pits for the embankment structures and the weir chambers. The submersed sections in the river were backfilled and covered with material; the bed of the Main was restored to its original state. The subsurface around the construction pits comprised recent fill, quaternary aggradation deposits, Young Tertiary marine deposits and Old Tertiary fresh and briny water deposits (mica sands). On this occasion there was no evidence at all of the tertiary clays and limestone banks (Hydrobien layers and Frankfurt Clay) known from the centre of Frankfurt. The entire tunnel passes through Cerithien layers comprising highly fissured lime layers with silt, which contain pressurised groundwater.

 

  • Country: Germany
  • Region: Hessen
  • Tunnel utilization: Traffic
  • Type of utilization: Underground, urban and rapid transit
  • Client: Deutsche Bahn AG
  • Main construction method: Open
  • Type of excavation: Immersion/Sinking
  • Tunnel total length: 265 m
  • Construction start/end: Nov. 1980 till Sept. 1983