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Arnsberg Altstadt Tunnel

The surrounding ground comprises alternating beds of solid to hard limestones and chalky clay shales and marl shales. The ground only permits little water to pass through it, the water ingresses during the heading were accordingly slight. The Ing.Gesellschaft Prof Dr.-Ing. B. MaidI + DipI.-lng. R. MaidI was responsible for the design, planning and supervision of construction. The tunnel's standard profile for the two-lane area possesses a clear width of 9.50 m, with a horseshoe-shaped cross-section and a flat base. The excavated cross-section amounts to approx. 85 m². The cross-section in the portal zones for the 4-lane area has a final width of 14.50 m (up to 17 m in excavated state) and a base invert. The excavated cross-section in these areas amount to as much as 165 m². The transition zone from the 2-lane to the 4-lane cross-section runs continuously. The longitudinal down gradient of the tunnel amounts to 2.2 %. The tunnel's maximum overburden amounts to 37 m and drops to as little as 7 m in the portal zone. The tunnel was driven on the rise from the western portal. A combined drill+blast/ cutterdrive was selected. The contract called for a division of the cross-section with advance crown and subsequent bench and base excavation. The heading operations were undertaken by Messrs, Beton und Monierbau in accordance with the shotcreting method. Securing was accomplished with shotcrete, support arches, structural steel mesh and rock bolts in accordance with the excavation classes. The thickness of the shotcrete was between 15 and 30 cm, the bolt length 4 to 6 m and the length of advance 1.0 to 2.5 m. A sealing system comprising protective non-woven fabric and a plastic membrane was installed in the tunnel. Continuous joint strips provided the connection with the base invert and the concrete abutment at the side. A sealing layer of 3 cm of shotcrete was placed to smooth the shotcrete surfaces. The underground water that was present was disposed of via drains located at the sides, which are passed into the collector channel independent of the carriageway drainage. A minimum reinforcement comprising matting was installed in the tunnel shell. This meant approx. 6 t of reinforcing per block. The demands on the concrete for the inner shell corresponded to a strength class B 25 concrete. The stripping deadline for the inner shell amounted to 12 h. The individual concreting sections were 10 m in length. The steel formwork which was used with a total weight of approx. 120 t was mobile and fully hydraulic. Through inserting certain elements, the formwork car could be expanded which enabled the 4-lane section to be completed.


  • Country: Germany
  • Region: Nordrhein-Westfalen
  • Tunnel utilization: Traffic
  • Type of utilization: Road tunnel
  • Client: Stadt Arnsberg
  • Consulting Engineer: Ing.-Gesellschaft B. Maidl + R. Maidl
  • Contractor: Beton- und Monierbau GmbH
  • Main construction method: Trenchless
  • Type of excavation: Drill-and-blast
  • Lining: In-situ concrete
  • No. of tubes: 1
  • Tunnel total length: 355 m
  • Cross-section: 85 m²-165 m²
  • Contract Volume: 31.6 mill. DM
  • Construction start/end: November 1992 till June 1995
  • Opening: September 1995