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Issues in Determining the Crack Initiation (CI) Threshold Under Confined Conditions



Details

  • Personal Author:
  • Description:
    It is important to accurately identify the stress at which micro-fractures initiate in rocks under compression when studying phenomena like excavation damage zone (EDZ) formation around deep underground structures, rock burst dynamics, stability of rock slopes, etc. This stress threshold, popularly termed as the point of Crack Initiation (CI), can be determined from strain measurements or acoustic emissions monitored during laboratory compression tests. In terms of strain-based approaches, the reversal of crack volumetric strain and the point of non-linearity in the axial stress-lateral strain curve are commonly used to identify CI. There is, however, a lack of understanding as to whether these approaches are applicable/effective for CI determination under higher confinements. To shed some light on this topic, this study utilizes the two aforementioned strain-based approaches to determine CI over a wide range of confinements in context of a granitic rock, a limestone and a coal. We discuss difficulties associated with using the two approaches for cases when the lateral strain curve is non-linear from the start of the tests. Ultimately, it was found that both approaches yield similar CI estimates at low confinements, but the discrepancy between the results obtained using these approaches increases as a function of confinement. In particular, the stress at the point of axial stress-lateral strain nonlinearity can be 1.5 times higher than the stress at the point of crack volumetric strain reversal. [Description provided by NIOSH]
  • Subjects:
  • Keywords:
  • Series:
    Mining Publications
  • Publisher:
    American Rock Mechanics Association (ARMA)
  • Document Type:
    Text
  • Funding:
    Contract
  • Genre:
    Proceedings
  • Place as Subject:
  • CIO:
    National Institute for Occupational Safety and Health (NIOSH)
  • Division:
    SMRD - Spokane Mining Research Division
  • Topic:
    Workplace Safety & Health
  • Location:
    North America
  • NIOSHTIC Number:
    nn:20061729
  • Citation:
    54th US Rock Mechanics/Geomechanics Symposium, June 28 - July 1, 2020, Golden, Colorado. Alexandria, VA: American Rock Mechanics Association (ARMA), 2020 Jun; :ARMA 20-1074
  • Federal Fiscal Year:
    2020
  • NORA Priority Area:
    Mining
  • Performing Organization:
    Colorado School of Mines, Golden
  • Peer Reviewed:
    False
  • Start Date:
    20160915
  • Source Full Name:
    54th US Rock Mechanics/Geomechanics Symposium, June 28 - July 1, 2020, Golden, Colorado
  • End Date:
    20210914
  • Collection(s):
  • Main Document Checksum:
    urn:sha-512:adb76435bf998f2981a3ca79b862023a187ec6f395271317e2128cdadf3055b1517a61aec101fed6d7f8db804575dcaa5b655de217ff65541382261379a7b525
  • Download URL:
  • File Type:
    Filetype[PDF - 1.06 MB ]
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