Motorway by-pass A5
Structural planning for the construction of the Buettenberg tunnel and Laengholz tunnel
The motorway by-pass of Biel closes the last gap in the Swiss national road network: the connection from Solothurn to Neuenburg. At the same time, the new segment around the Biel connects the A5 with the A16 Transjurane and the T6 in the direction of Bern.
The roughly 4,9 km long eastern branch reaches from the forking Brueggmoos up to the forking Boezingenfeld. Thereby, the partial project consists of the production of two 2-tubed street tunnels, the Buettenberg tunnel with a length of approx. 1.470 m and the Längholz tunnel with a length of approx. 2.500 m.
Both tunnels are driven against by utilising a ground pressure shield with a diameter of 12,60 m. Hereby, the most different of construction ground conditions, meaning solid and loose rock, as well as strongly differentiating ridge overburden and the under passing of constructional help measures with low overburden in the approach area have to be overcome. As it turned out, especially critical points included the transitions from loose rock to solid rock, respectively the other way around, as well as the gravel-sandy grounds with a permeability of 10-4 m/s and above.
For the execution, a technical consulting by the executive ARGE was carried out. The provision of the support pressure and crimp pressure calculation followed.