This article describes a new method for creating tunnel roof support which uses Sandvik's simultaneous drilling and casing system Tubex. This system was pioneered in difficult tunnelling conditions through the glacial moraine in the Italian Alps. The method developed, using Tubex 90 and 115, used a modified Crawler drilling to install 12 m casing tubes around the profile of the top heading. Spacings between the tubes were varied between virtual zero and 300 mm depending on ground conditions. In order to give the tubes added strength, and to provide an interlinking concrete medium between each tube, each tube was drilled with a number of holes. Each hole was then fitted with a simple valve mechanism, designed to burst when the grout pressure reached 300 kN/square metre. This enabled the pressurized grout to escape through the perforations and into the surrounding moraine. This provides some interlinking between individual tubes, and the result is a steel and concrete curtain, with superior bearing capacity. Further roof security was obtained by installing the tubes so that one series of tubes overlaps the next by up to 3 m. The cost of the Tubex method compared favourably with a jet grouting method and had the added advantages of: (a) being much less sensitive to water intrusion; and (b) enabling excavation to be started up after 12 hours of installation rather than 50.

  • Availability:
  • Corporate Authors:

    Thomas Telford Limited

    London,   United Kingdom 
  • Authors:
    • -
  • Publication Date: 1990-3


  • English

Media Info

  • Pagination: p. 14-15
  • Serial:
    • Volume: 23
    • Issue Number: 2
    • ISSN: 0017-4653

Subject/Index Terms

Filing Info

  • Accession Number: 00606957
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Mar 31 1991 12:00AM