Wattkopftunnel, bypass of Ettlingen
The ground can be divided up into two zones with rock mechanically essentially different features. The Rheingraben fault at the western foot of the Wattkopf forms the divide. Zone I: quaternary, tertiary and the Graben fault zone Starting from the western portal, Pleistocene, clayey sandy shifting soils with coarse variegated sandstone debris are to be found over a distance of approx. 250 m. This is followed by a roughly 250 m long zone with Oligocene, over consolidated, fine sandy clay and sandstone lentils, an interim zone between solid and loose rock. The Rheingraben is completely disintegrated bed rock which has been fractured into small fragments as well as densely bedded, slippery, cohesive rock. Zone II: variegated sandstone To the east of the Rheingraben fault, there is an homogeneous, fine layered to coarsely bedded sandstone horizon from the Middle Variegated Sandstone period. The western and eastern portals were built as 2-storey reinforced concrete frame constructions with watertight reinforced slab concrete, in which the central control rooms are integrated. The execution of the mined tunnel took place in 2 working phases. Excavation according to the NATM in order to react flexibly to changing ground conditions. The manner in which the rock was excavated as well as the supporting agents required were varied. The excavation of the overall cross-section took place in two part excavations, crown (upper cross-sectional part) and the bench (lower cross-sectional part). A further part-excavation - the base, was carried out for the static requirement of a base invert. Starting from the western portal, at some points tunnelling of the side walls was undertaken. In the geologically more unfavourable zone I (loose rock), a cross-section with base invert was necessary, the excavation was accomplished using a hydraulic excavator. In the adjoining zone II (solid rock) the rock was removed via bore and blasting, with the crown being driven from the west until the breakthrough before the bench was tackled. The vault was sealed by a nonwoven textile layer and a 2 mm thick plastic membrane to keep out underground water. The 40 cm thick, reinforced tunnel inner vault was placed against this seal.
- Country: Germany
- Region: Baden-Württemberg
- Tunnel utilization: Traffic
- Type of utilization: Road tunnel
- Client: Regierungspräsidium Karlsruhe
- Main construction method: Trenchless
- Type of excavation: Excavator/Drill-and-blast
- No. of tubes: 1
- Tunnel total length: 1950 m, incl. 160 m cut-and-cover
- Cross-section: 86 m²
- Contract Volume: 121 mill. DM
- Construction start/end: 1988-1994 (6 years)
- Opening: 9.12.1994