Project Description

The bypass Lungern is a roundabout 4.25 km long road project of the Canton Obwalden in the Centre of Switzerland. Main building is the 3’570 m long, two-lane traffic tunnel. An essential element to ensure the national safety regulation is the parallel emergency tunnel, which is subsequently incorporated into the project, linked with the main tunnel by cross passages of every 250 m. Additional niches for services, SOS and fire hydrants are also elements of the main tunnel.

Project Requirements and Solutions

Drainage and Waterproofing:

The tunnel is built as a drained system including a plastic element (Sikplan® WP Drainage Angle) and a filter bed of pure gravel at the edges of the floor. The key element of using this PVC-U drainage profile is the elimination of filter concrete and/or cement fixation of the gravel package to reduce silting and blocking of the drainage pipes.

The waterproofing system, consisting of a multi-task Sikplan® WT TUNDRAIN and a 2 mm thick PVC-P membrane installed by mechanized operation scaffolding. The multi-task (drainage and protection) layer is based on foamed low-density polyethylene (PE-LD) with high water flow capacity (>= 0.48E-3 m2/s tested at 200 kPa), installed direct on the shotcrete surface with a surface evenness of 10:1. The key characteristics of the waterproofing membrane- according to SIA V 280 are:

  • Raw Material: Soft PVC-P with a total thickness of 2 mm including signal layer
  • Module of elasticity (Flexibility/ Workability): lower than 20 N/mm2 acc. EN ISO 527
  • Impact resistance (500g)/Dynamic perforation test: no leak at 900 mm acc. EN 12691
  • Burst strength (bi-axial behaviour) acc. EN 14151 (Ø1.0 m): >= 50 %
  • Long term compression strength acc. SIA V 280-14: >= 7N/mm2 (48h / watertight)
  • Fire resistance with low smoke behaviour: class V.2 acc. SIA V 280 (self extinguishing)

Shotcrete Application:

To avoid cost intensive tailor made concrete forms in the location of the service niches, shotcrete is applied direct onto the waterproofing membrane, which is  protected by a 4 mm thick PVC-P protection sheet. To reduce the rebound of the shotcrete, one layer of wire mesh is also installed.

Sika Products

In addition the following Sika products were used in the project

  • Sikaplan® WP 2110-20 HL
  • Sikaplan® WP Protection Sheet 40 HE
  • Sikplan® WP Drainage Angle
  • Sikaplan® WT Tundrain
  • Sikaplan® WP Disc 80/10mm yellow
  • Sikaplan® WP Trumpets
  • Sikaflex® 11 FC
  • Sika AnchorFix®-3+
  • Sikaplan® WP Injection Flange 10/12

Check out more information about Sika construction products in the Swiss market

Project Participants

Client: Kanton Obwalden
Project Engineering: Bundesamt für Strassen ASTRA / Hoch- und Tiefbauamt Obwalden
Design: Ingenieurgemeinschaft A8 Umfahrung Lungern
Construction Company: Consortium AUL (Implenia Bau AG,
Gasser Felstechnik AG, Bürgi AG)
Membrane Applicator: Sika Bau AG
Construction period/ main tunnel: 2006 -2011