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Tunnel Gruibingen, A8, 6-lane extension

In the course of the 6-lane extension of the federal motorway A8 Karlsruhe - Munich in the Gruibingen - Mühlhausen section, the gradient of the downhill lanes (directional lanes Karlsruhe - Munich) was lowered compared to the uphill lanes (directional lanes Munich - Karlsruhe) and laid in a tunnel structure for noise protection reasons. In this area, the federal motorway is closely embedded between the municipality of Gruibingen and the steep slope of the Rufstein, which should not be interfered with for geotechnical and ecological reasons.

The difference in height of the gradients on the mountain and valley sides is up to approx. 6 m. The gradients are located on the upper and lower sides of the Rufstein. The roadways on the uphill side were equipped with a noise barrier on the Gruibingen side. The retaining walls at the foot of the Rufstein on the mountain side were preserved and not changed. Before and after the tunnel construction, the residents of Gruibingen are now protected by noise barriers.

The tunnel structure integrates at different depths in the terrain. Over large areas, the tunnel does not lie entirely below the top edge of the terrain, but the walls on the mountain or valley side protrude from the existing terrain. The tunnel ceiling was covered over its entire length with an overburden with a maximum height of 2 m, which rises from the valley side to the mountain side. A reinforced concrete wall directly on the tunnel forms the mountain-side end of the overburden, and on the valley side the overburden either runs against a cap, which is designed as a planting trough, or it merges into the existing terrain.

The tunnel was constructed using the open method of construction. Since the tunnel cross-section is always above the groundwater table and large quantities of seepage water are not to be expected, an open cross-section at the bottom could be used. Depending on the subsoil situation, it is either flat in the rock, flat on a soil exchange or founded on piles in the rock. The foundation varies blockwise in both longitudinal and transverse directions.

The tunnel and the retaining walls were constructed over the entire length of the structure as a rigid frame construction wall (d=1.00m)/ slab (d=1.20m), WUB-KO in block construction. The unicellular tunnel blocks are separated by space joints and have a standard length of 12 m. The tunnel blocks are constructed in a block construction. 

 

  • Region: Gruibingen, Baden-Württemberg 
  • Tunnel use: Road 
  • Client: Land Baden-Württemberg on behalf of Regierungspräsidium Stuttgart 
  • Planner: Leonhard, Andrä und Partner Beratende Ingenieure GmbH, Stuttgart/ Ing.-Büro für Elektrotechnik Adam, Stuttgart/ GBI Gackstatter Beratende Ingenieure GmbH; Stuttgart
  • Contractor: ARGE Ed. Züblin AG, Stuttgart/ F. Kirchhoff Straßenbau GmbH & Co.KG, Leinfelden/ Siemens AG, Stuttgart 
  • Construction method(s): open cut. (w/s)
  • Tunnel length: 540 m
  • Cross section: SQ: Lw 16,50 m (0,75 m/ 2*3,50 m + 3,75 m/ 0,50 m/ 2,50 m side-strip 
    zzgl. 2*1,0 m emergency walkway)
  • Costs: Construction cost incl. technical equipment 24.0 Mio. € 
  • Construction time: 10/2010 to 11/2012
  • Start of operation: 06/2012 (4+0 traffic)