Britain's longest rock tunnel has just been completed using only fullface tunnelling machines. Although the contract is a year behind schedule, ground conditions were unpredictable and a longer time would have been needed for drill and blast methods. The fullface method was also considered safer, there was less disturbance to the rock and very little overbreak, permitting substantial savings in the cost of concrete linings. The contractor decided what support to install, this did not always correspond to the type and frequency estimated in the tender which was priced on every metre of the route before tunnelling started. Of the two machines used in the contract, the American Robbins had a better performance than the demag. However, it was found that the penetration rate of the demag could be increased by 25 per cent by reducing 13 of the cutters to double discs and the remainder to single discs. The Robbins Machine had an additional advantage in that support could be installed 2 M behind the head compared with 12 M for the demag cutter. (TRRL)

Media Info

  • Features: Figures; Photos;
  • Pagination: p. 14
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00316915
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Oct 27 1980 12:00AM