STRESS CONCENTRATION FACTORS FOR THE INTERPRETATION OF DOORSTOPPER STRESS MEASUREMENTS IN ANISOTROPIC ROCKS

One of the most frequently used in situ stress measuring techniques in rock mechanics is the borehole stress relief technique known as the "doorstopper" method. It is well known that difficulties can arise with the interpretation of stresses calculated from in situ strain measurements (e.g. broadly scattered results or even negative values of the in situ stresses at the test location). This may be due to the usual assumption that rock exhibits isotropic elastic material behaviour rather than considering its actual anisotropy behaviour at the test site. In addition, the variation of the stress concentration factors at the end of the borehole as a function of the rock anisotropy is generally neglected. In this paper, the concept of stress concentration factors related to the doorstopper technique is briefly reviewed with respect to transversely anisotropic rocks. Stress concentration factors for various degrees of anisotropy were numerically calculated using the finite element method and have been tabulated for different parameter configurations. The relation between stress concentration factors and elastic parameters of the rock are discussed. The most important formulae for calculating in situ stresses from doorstopper measurements in anisotropic rock are subsequently explained. Finally an example is given of the potential errors which can be caused by interpreting in situ stress measurements without regard to rock anisotropy. (TRRL)

  • Availability:
  • Corporate Authors:

    Pergamon Press, Incorporated

    Headington Hill Hall
    Oxford OX30BW,    
  • Authors:
    • Rahn, W
  • Publication Date: 1984-12

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Filing Info

  • Accession Number: 00394622
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Jul 31 1985 12:00AM