SPRAYED CONCRETE: TUNNEL SUPPORT REQUIREMENTS AND THE DRY MIX PROCESS

The particular structural requirements of sprayed concrete acting as an arch or a ring to support a Carboniferous shale in the Kielder Water Scheme Experiment Tunnel are described in the light of detailed performance studies of several support systems over a period of two years. The rate at which the concrete stiffens needs to be optimized for economy and safety in relation to the timing and position of constructional operations and their influence on the dilation of the rock particularly in small tunnels. The inherent characteristics of the dry-mix spraying process, all of which affect the quality of the concrete, are presented from the results of laboratory and field trials. The concrete can be improved and the demands on the spraying operator reduced by the simple procedures of injecting the water earlier to give better mixing and by pre-setting the water dosage. The use of an accelerating admixture, correctly dosed and of predictable compatibility with the cement, has considerable practical advantages. The effects of admixtures on long-term strength and on early time-dependent properties, considered to be important in support requirements, have yet to be studied. /TRRL/

  • Corporate Authors:

    Building Research Establishment

    Building Research Station, Garston
    Watford WD2 7JR, Hertsford,   England 
  • Authors:
    • Ward, W H
    • Hills, D L
  • Publication Date: 1977

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 23 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00172558
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: BRE CP 18/77
  • Files: ITRD, TRIS
  • Created Date: Jun 28 1978 12:00AM