Expansion bolts are preferably used for temporary rock bolting. This bolt type is quickly installed and may be recovered. Rock bolts made from reinforcing bars may be grouted with an expanding concrete mortar. In order to prestress the rock bolts they must be anchored with synthetic resins or a wedge before grouting. A suitable washer for rock bolts is concave and circular. When the rock is very fractured, rock straps and netting may be installed together with the bolts. The parts of the rock bolt which are not grouted, must be protected against corrosion if they are to be permanently installed. By sporadic bolting, one or more rock bolts are installed at dangerous rock fractures. The number of bolts may be calculated in a simplified way by neglecting friction and cohesion forces on the fissures. Another dimensioning method, which takes into account the friction forces is also presented. The friction force on fissures may be increased by prestressed rock bolts. Rock bolts should usually be installed in a direction which causes a minimum of shearing stress. /Author/

  • Corporate Authors:

    Norwegian Road Research Laboratory

    Postboks 8109, Gaustadalleen 25
    Oslo,   Norway 
  • Authors:
    • Brenna, E
  • Publication Date: 1975-9


  • Norwegian

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00131559
  • Record Type: Publication
  • Report/Paper Numbers: No. 48
  • Files: TRIS
  • Created Date: May 14 1976 12:00AM