N8 Lungern Bypass

The Lungern bypass is 4.25 km long. The 3,570 m long Lungern Tunnel with two-way traffic is the main structure and passes through limestone, marly rock formations and approximately 100m of loose rock. To clarify the geological uncertainties an exploratory shaft was bored beforehand with a Ф 4.75 m TBM. Due to the geological problems which were encountered the alignment of the main tunnel had to be optimised and moved further uphill. The work resulted in around 600,000m3 of excavated rock, of which 500,000m3 could be deposited again. The rest can be reused for construction. To ensure optimal tunnel safety a safety tunnel was subsequently added to the project. Every 250-300m there will be a cross-link. In the main tunnel there are two-sided exit bays and SOS and hydrant points are located at 150m intervals.

The tunnel has longitudinal ventilation with smoke extraction. Ventilation stations and operation rooms are located at the portals.

Main Data

  • Length of bypass: 4.25 km
  • Length of tunnel: 3,570 m
  • Distance between main tunnel and safety tunnel: Approx. 20 m
  • 2-sided exit bays: 4 Pcs.

Client

Obwalden Canton, Department of Con-struction and Spatial Development, Civil Engineering Agency, Sarnen

Consultant

IUB Engineering Ltd in consortium

Construction period

1999-2012

Construction costs

CHF 268 million

Scope of services

  • Construction planning
  • Tendering
  • Site supervision