A COMPARATIVE FIELD STUDY OF ROCK STRESS DETERMINATION TECHNIQUES

RESEARCH WAS CONDUCTED TO DESIGN EXPERIMENTS TO PERMIT A COMPARISON OF THE DETERMINATION OF IN-SITU STRESSES IN ROCKS. A FOUR FOOT SQUARE ON THE QUARRY FLOOR WAS FIRST INSTRUMENTED AND THEN RELIEVED FROM ANY REGIONAL STRESSES BY DRILLING FOUR SLOTS AT RIGHT ANGLES AROUND THE INSTRUMENTED REGION. THE PIECE OF ROCK ISOLATED BY THIS MEANS WAS THEN RESTRESSED BY MEANS OF FLAT JACKS INSERTED IN THE SLOTS. THIS MADE IT POSSIBLE TO COMPARE THE VARIOUS TECHNIQUES OF ROCK STRESS DETERMINATION IN EITHER UNIAXIAL OR BIAXIAL STRESSFIELDS GENERATED BY PRESSURIZING THE OPPOSITE PAIRS OF FLAT JACKS. THE FOLLOWING TECHNIQUES WERE TESTED: (1) DIRECT CURRENT DIFFERENTIAL TRANSFORMERS TYPE DISPLACEMENT TRANSDUCERS, (2) LONG BONDED RESISTANCE STRAIN GAGE, (3) BOREHOLE DEFORMATION GAGE, (4) A DOORSTOPPER BOREHOLE STRAIN GAGE DEVICE, (5) PHOTOELASTIC DISK, STRAIN-LINE COMPASS, (6) PHOTOELASTIC STRESSMETER, AND (7) FLATJACKS FREYSSINET TYPE. THE GAGES WERE PLACED ON OR IN THE ROCK SURFACE IN THE GRANITE QUARRY. THE INSTALLATION IS DESCRIBED OF EACH OF THE DIFFERENT GAGES AND METHOD OF TAKING MEASUREMENTS. THE SCATTER OF THE TEST RESULTS IS HIGH IN SPITE OF WHAT WAS CONSIDERED GOOD WORKING CONDITIONS. IT IS CONCLUDED THAT RESULTS OBTAINED FROM CURRENT TECHNIQUES OF STRESS DETERMINATION SHOULD NOT BE RELIED UPON WITHIN PLUS OR MINUS 20 OR 30% OF THE MEAN VALUES, EVEN UNDER IDEAL CONDITIONS.

  • Supplemental Notes:
    • Tech Rept NO 1-69, 71 PP, 28 FIG, 4 TAB, 9 REF
  • Corporate Authors:

    University of Minnesota, Minneapolis

    Minneapolis, MN  United States  55455
  • Authors:
    • Bonnechere, F
  • Publication Date: 1969-4

Subject/Index Terms

Filing Info

  • Accession Number: 00235468
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 2 1994 12:00AM