As part of the Swiss government "railway 2000" plan to upgrade their rail network, a twin track 6.3 km tunnel, the granholz tunnel, is to be bored through the pre-alps between schonbuhl and bern. This article describes the world's biggest mixed face tunnel bored (tbm) the herrenknecht machine, which will be used to drive the tunnel through water charged glacial tills and hard dry sandstone bedrock. The tbm will use its slurry mode to repulse groundwater in the fine glacial tills, and it is fitted with a rock breaker which can process boulders up to 1.2 m. The start of the project was delayed 8 months by the complex dewatering necessary in the drive pit area, where high groundwater and artesian heads necessitated the installation of 45 deep pumping wells and gave a water abstraction flow rate of 1500 litres/minute. A diaphragm and shotcrete wall tied back with 80 ground anchors tensioned to 40 t placed along 8 levels has been built to reinforce the drive pit area. The tunnel will be lined by single skin, 400 mm thick, 1.8 M long concrete rings of 6 arc sections completed by a keystone piece and made watertight with rubber seals between the rings. The onsite production process for the sealing rings is briefly described. Minimum allowable concrete strength is 50 kn/mm2.

  • Availability:
  • Corporate Authors:

    Thomas Telford Limited

    London,   United Kingdom 
  • Publication Date: 1989-10


  • English

Media Info

  • Pagination: p. 21-23
  • Serial:
    • Volume: 22
    • Issue Number: 7
    • ISSN: 0017-4653

Subject/Index Terms

Filing Info

  • Accession Number: 00498879
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Sep 30 1990 12:00AM