Switzerland

Küblis Bypass: Tunnelling starts

Extensive preliminary work on the 3,350 m long Küblis bypass tunnel in the Canton of Grisons, including the Dalvazza pilot cut (2009/2010) for the portal zone, preparations for actual tunnelling and preparatory work for the cut-and-cover tunnel, has been under way for the past two years. The construction of ventilation and electrical switching centres is planned for a later phase of the project. The pilot cut of the Küblis Tunnel itself, the central element of the project, which includes not only the 2,255 m tunnel with two contraflow lanes and an escape tunnel, but also the Dalvazza connecting structure and the new Saaserstutz road system, was made in late September, 2010. Total investment for this project amounts to 210 million CHF (155 million EUR). The opening of the Küblis Bypass is scheduled for 2016.

The Küblis Tunnel starts, in the west, a short distance from Dalvazza, passes below the trackbed of the „Rhaetian Railway“ (Rhätische Bahn, RhB), the Parsaura ridge and the base of the Schanielatobel, and opens near Prada into the road system leading to the town of Klosters. The tunnel has a length, including the Prada gallery, of 2,255 m, with a maximum overburden of 170 m. The tunnel section is of horse-shoe configuration, and has been conceived for drilling and blasting (D&B) excavation.

A 2,070 m long downward-sloping escape tunnel with a 2.80/2.80 m cross-section is to be constructed at a distance of 30 m from the main tunnel; this will be linked to the tunnel every 300 m by transverse galleries. The tunnel is to be driven through the rock, and completed using cut-and-cover in the non-cohesive rock sections at Dalvazza and Prada. ⇥G.B

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