The theoretical and experimental investigation in this paper shows that it is practically impossible to create a uniform stress within the samples in the uniaxial compressive (as well as tensile) test for the strength of rock materials: small uncontrollable eccentricities in the loading result in considerable bending stresses compared to the constant axial stress that the test is supposed to create. Strain gauge measurements show that the force at which the samples are broken is practically independent of the eccentricity within the interval in which the latter is found to vary at random, although this interval corresponds to stress variations of about plus or minus 30% of the average stress. Previously reported experimental results for Bohus granite, Ekeberg marble and Lemunda sandstone showed no statistically significant decrease of the uniaxial tensile strength with increasing sample volume. The same result is obtained for these rocks in the uniaxial compressive strength test in which rock cores, the length of which was twice the diameter, were tested. These statistically very well established results are in contradiction to the currently accepted knowledge within the field regarding the effects of sample size on strength values for rock materials. (TRRL)

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  • Corporate Authors:

    Stiftelsen Svensk Detonikforskning

    P.O. Box 32058
    Stockholm,   Sweden 
  • Authors:
    • Wijk, G
  • Publication Date: 1979

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Filing Info

  • Accession Number: 00323162
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • Report/Paper Numbers: Report DS 1979 13 Monograph
  • Files: ITRD, TRIS
  • Created Date: May 21 1981 12:00AM