Castasegna Open Tunnel

Starting situation and idea

A bypass was to be built in the border town to relieve it from transit traffic which ran on a single-lane village road. The heart of the bypass is a roughly 300m-long open tunnel.


With a total length of 382m, the tunnel is designed in the form of an asymmetric monolithic frame. The supports inclined at 5:1 hold up the delicate roof in white concrete. 22m and 33m-long walls are built to contour the terrain at either end as naturally as possible.


Due to the proximity to the village, the bypass was to be aligned in such a way that the gardens of the lowermost houses appear as natural as possible without walls or embankments. Due care was to go into the design so that the visual appeal of the village was not compromised.


Developer: Tiefbauamt Graubünden
Completion: 1999
Project type: New structure
Project author: Fanzun AG
Construction costs: CHF 9,1 Mil
Scope of services: Project Management, Civil Engineering

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