Skip navigation

Lohberg Tunnel

The B426 runs from the Rhine to the Main thus linking the Odenwald to the motorway network. The bypass for the community of Nieder-Ramstadt with the Lohberg Tunnel and 2 valley bridges together with already existing bypasses and sections of road constitutes a continuous stretch of highway that relieves a number of town centres and serves to improve the B426's linking function as well as to increase traffic safety. The Lohberg Tunnel was driven by mining means over a length of 903 m. 112 m in the north and 65 m in the south were excavated by cut-and-cover. For safety technical reasons, a 790 m long escapeway extends from the south portal. It is linked to the main tunnels by 3 cross-passages. Emergency lay-bys are set up at both sides roughly in the middle of the tunnel, which are also connected up with the escape tunnel. The pressure-water retaining cross-section is more or less circular to translate the clearance profile for the standard cross-section RG 10.5 T into practice, which caters for an overall carriageway width of 7.5 m and two 1.0 m wide emergency footpaths. The clear height of the carriageway amounts to 4.50 m. Over a length of725 m, an intermediate ceiling with exhaust flaps is foreseen at 75 m intervals for smoke removal purposes in the event of fire. A ventilation centre is to be set up at level 2 above the tunnel at the south portal. For standard mode, an additional longitudinal ventilation system provided by 2 jet fans located in the tunnel will be installed. The excavation carried out by mining means took place along the entire tunnel route in diorite, a grey to dark green coloured plutonic rock. The rock line as the border between weathered and largely unweathered ground, by and large, followed the terrain's morphology, with the weathering front extending into the drive depending on the local tectonic conditions. Strongly weathered diorite covered by loess loam prevailed in the trenchless section in the south so that advance supporting measures in the form of pipe umbrellas had to be introduced. ln the north, the shallow overburden of the excavation with loess loam in addition to the low rock strength necessitated pipe umbrellas to be set up. The drive was executed using the NATM with drill+blast and the excavated cross-section split up into crown, bench and floor. Practically all of the mined part of the tunnel is located below the groundwater table with water pressures of up to 3 bar and is hydraulically separated by a filter from the northern area that is not water bearing. The lining with base invert will be capable of retaining water.

 

  • Country: Germany
  • Region: Hesse
  • Tunnel utilization: Traffic
  • Type of utilization: Road tunnel
  • Client: Federal Republic of Germany- Land of Hessen
  • Consulting Engineer: Bung Beratende Ingenieure
  • Construction monitoring: Bung Beratende Ingenieure, BGS Ingenieursozietät
  • Contractor: Max Bögl Bauunternehmung GmbH & Co. KG, Swietelsky Bau Gesellschaft mbH
  • Main construction method: Trenchless
  • Type of excavation: Drill-and-blast
  • Lining: Concrete formwork / Shotcrete
  • No. of tubes: 2
  • Tunnel total length: 1,080 m, 903 m of which driven by mining means, 790 m escape tunnel
  • Cross-section: 99 m², 170 m² (lay-bys), 14/22 m² (escape tunnel accessible/drivable)
  • Contract Volume: approx. € 35 million
  • Construction start/end: September 2003 to November 2006
  • Opening: 2007