Location: Rabka (Poland)
Year: 2016 – ongoing
The Maly Lubon Tunnel is the longest tunnel in Poland, as part of the expressway S7 Krakow-Rabka Zdroj investment. It is twin tube tunnel 2 km long with sections 220 m2 large, excavated through the Maly Lubon mountain by Astaldi.
The tunnel excavated in the Carpathians, consists of alternative layers of sandstone and shale with high variable degree of weathering. Due to the extreme variability of the rock mass behaviour, it was decided to change the excavation technology from the NATM to the Convergence- Confinement method. The big challenge of this change required a new design for the South portal, in the most weathered and heavily tectonized Flysch, already subject to large displacements during its geological history. Soil-structure interaction analysis with 3D FEM modelling were also carried out for a wider tunnel section which included emergency lanes and a vehicular cross passage intersecting with an additional technological tunnel.
Finally, siginificant works have been carried out also for the the tunnel excavation portals, including piling, retaining walls, slope stability improvement, earthworks.