ROCK REINFORCEMENT FOR TUNNELS

THE RESULTS OF EXPERIMENTS CONDUCTED IN HARD ROCK USING VARIOUS TYPES OF ROCK STUD ASSEMBLIES AND DIFFERENT METHODS OF INSTALLATION HAVE SHOWN THAT ALMOST ALL THE EXPANSION SHELLS USED IN SOUTH AFRICA ARE RELIABLE AT TENSIONS OF UP TO EIGHT TONS. FOR ECONOMIC REASONS, IN HARD ROCK, STUD LENGTHS SHOULD BE KEPT TO A MINIMUM AND PLASTICALLY DEFORMABLE WASHERS ARE THE MOST RELIABLE IN MAINTAINING TENSION. HYDRAULIC TENSIONING IS THE ONLY RELIABLE MEANS FOR APPLYING TENSION TO A ROCK STUD ASSEMBLY AND PRE-STRESSING OF THE BOLT BY UP TO 20 PERCENT ABOVE THE FINAL TENSION 'BEDS DOWN' THE ASSEMBLY, PROVIDING SUPERIOR ROCK REINFORCEMENT. ONCE TENSIONED, THE NUT ON THE STUD SHOULD BE TORQUED TO REDUCE THE PULL ON THE HYDRAULIC TENSIONER BY 20 PERCENT FOR THE ASSEMBLY TO MAINTAIN THE TENSION ONCE THE TENSIONER IS REMOVED ANY INSTALLATION IN HARD ROCK WHICH WAS TEN FEET OR MORE FROM THE BLASTING AREA WAS FOUND TO LOSE VERY LITTLE TENSION DUE TO THE BLAST, PROVIDED IT WAS INSTALLED CORRECTLY AND WAS MADE OF WELL DESIGNED COMPONENTS. /RRL(A)/

  • Supplemental Notes:
    • pp 141-145, 1 FIG, 4 TAB, 4 PHOT, 2 REF
  • Corporate Authors:

    South African Tunnelling Conf

    ,    
  • Authors:
    • Smith, W M
    • Thiel, P S
  • Publication Date: 1970-6

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00235159
  • Record Type: Publication
  • Source Agency: Road Research Laboratory /UK
  • Report/Paper Numbers: pp 81-84
  • Files: TRIS
  • Created Date: Aug 29 1971 12:00AM