Delivered by experienced international Civil Engineer Erik Neun, you will partake in an evening of discussion on the learnings from the Oberau Bypass Tunnel: A 3km-long project that underpasses various buildings, and traverses alpine rock formations and grainy soil in Gießenbach Valley.

Due to the possibility of a sudden rise of groundwater levels above the tunnel alignment in cases of heavy rainfall during tunnel excavation, the installation of a groundwater lowering well gallery has been called for.

Consideration has also been given to the impact of surface settlements caused by the tunnelling in the builtup area of Oberau. Based on an initial assessment of expected settlements, compensation grouting has been foreseen for three buildings (two workshops with individual foundations and a residential building with a raft foundation).

The paper being discussed focuses on various aspects of the design and construction of the tunnel, and the experience with and lessons learned from the project, including limitations of FE modelling concerning the influence of specific tunnelling technics, the compensation grouting, and the optimisation of forward spiling.