The acceptance testing of production anchors is discussed, and comments are are made on the long-term monitoring of selected production anchors. It is stressed that the testing procedure must yield a measured safety factor as determined by overloading for a short period. To check the measured performance against that predicted by calculation, it is essential that a load-extension graph be plotted for each anchor. Also, an attempt must be made to obtain an indication of fixed anchor movement, since this will enable the assessment of the component of permanent displacement of the anchor with time. It is noted that while load- extension boundary lines are favored in practice, care and attention is required in interpretation. To alleviate problems in interpretation, it is recommended that all production anchors should be subjected to at least one stage of cyclic preloading. Attention should then be focussed on the load- extension plots of the second and any subsequent load cycles from which most of the initial non-recoverable movements have been removed. For economic as well as operational reasons, the time involved for the stressing and control of anchors on a construction site should be minimized. Field experience indicates that prestress losses may be significant in heavily weathered rock or fractured rock with clay infill. It is noted that only when creep losses are monitored over long periods for a variety of anchor loads and geometries and for a wide range of classified rock types, will an accurate predictive capacity be available.

  • Availability:
  • Supplemental Notes:
    • This is the second section of this article; the first appeared in the March 1976 issue, pp. 20-29, and the third is published in the May 1976 issue.
  • Corporate Authors:

    Foundation Publications Limited

    7 Ongar Road
    Brentwood CM15 9AU, Essex,   England 
  • Authors:
    • Littlejohn, G S
    • Bruce, D A
  • Publication Date: 1976-4

Media Info

  • Features: Figures; Tables;
  • Pagination: 4 p.
  • Serial:
    • Volume: 9
    • Issue Number: 3
    • ISSN: 0017-4653

Subject/Index Terms

Filing Info

  • Accession Number: 00141862
  • Record Type: Publication
  • Report/Paper Numbers: Analytic
  • Files: TRIS
  • Created Date: Jan 16 1977 12:00AM