Freudensteintunnel

The Freudenstein Tunnel is to be found in a part of the so-called Stromberg Syncline, a large area of subsidence with particularly thick layers of gypsum keuper (approx. 160 m), synclinal structures, layer warping and occasionally minor faults with only low filling heights. West: This part-section is entirely located in layers of gypsum keuper. Middle: This part-section of the mined tunnel is located in a zone of Middle Keuper (gypsum keuper). Typical for this formation are the two different groundwater floors in the schilf sandstone (km 2) and in the Green Estherian layers (km 1), the hydraulic separation of which in zones where Upper Colonred Estherian layers are missing, is, however, only incompletely formed. There is a concentrated inflow of water, wherever the active elution zone meets up with the cross-section. East: The subsurface encountered here comprises creek deposits and coloured marls. Layers comprising slightly weathered schilf sandstone were present in the base. Over a distance of 4,800 m, the Freudenstein Tunnel passes through anhydrite-bearing clay stone of the gypsum keuper, which swells or heaves when water is present. Apart from providing for stability under great pressure, impermissible lifts of the tunnel base as a result of swelling or heaving pressure must be prevented in order to ensure that the DB's high-speed train services are in no way jeopardised. In order to exclude the risk that an under-dimensioned tunnel lining might be destroyed after only a few decades, a structure based on the "yielding base support" was chosen. A compressible layer (crusher zone) is installed in the base between the lining and rock, which allows swelling lifts to a minor degree and by doing so, delays the accumulation of swelling pressure and reduces the final value. Execution: West: The Freudenstein Tunnel west sub-section was executed by mining means with three main points of attack worked parallel to one another in order to ensure that the relatively short tunnelling time of 16 months could be adhered to. Central: The Freudenstein central sub-section was also driven by mining means. In this connection, driving the benches was badly affected by pronounced inflows of underground water. East: The slight overburden heights of up to 15 m made it possible to create the roughly 400 m long tunnel section via cut-and-cover with a connecting 255 m long groundwater trough.

• Country: Germany
• Region: Baden-Württemberg
• Tunnel utilization: Traffic
• Type of utilization: Main-line rail
• Client: Deutsche Bahn AG
• Main construction method: Trenchless
• Type of excavation: Drill-and-blast
• Lining: Ortbeton (Stahlbeton)
• No. of tubes: 1
• Tunnel total length: 6756 m, including 655 m cut-and-cover
• Cross-section: 153-191 m²
• Contract Volume: 540 mill. DM
• Construction start/end: 1986-1990 (4 years)
• Opening: December 1990