Security gallery for Ligerz tunnel

Highway N5 - Security gallery for Ligerz tunnel

Client / Owner

Office federal des routes - OFROU-F1

Execution

2013 - 2018

Total costs

36.9 million EUR

Project description

The Ligerz tunnel was commissioned in 1991. Consisting of a single bi-directional tube, it is no longer meeting the current security requirements. The main security default is the absence of fire exits.

The project for securing the Lugerz tunnel include:

  • construction of a security gallery, parallel to the main tunnel, with connection every 300 m.
  • construction of 4 new technical rooms underground.
  • construction of an underground central technical office new the western portal.

Geology

  • good quality limestones and marls (Cretaceous & Malm)
  • important risk of karstic water inflows up to 1500 l/s.

Excavation on the western portal

  • earthworks of 20'000 m³, mainly in rock;
  • proximity of the tunnel, under operation, with geomonitoring;
  • drilling of a water discharge (micro boring machine, under the N5 highway and railways (D 1100 mm / L 45 m).

Security gallery

  • lengths: 2170 m;
  • excavation with hard rock boring machine, diameter 4.75 m.

Connection / underground technical rooms

  • 9 connections from the main tunnel to the security gallery (longueur 18 m à 40 m);
  • 4 technical rooms;
  • excavation with rock splitter and explosives;
  • final connections to the main tunnel only during night closures of the tunnel. 

Central technical office on the western portal

  • underground centre (6000 m³ on 2 floors).

Services

  • Detailed design
  • Tenders
  • Construction design
  • Works supervision

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