STP745: Precursors of Laboratory Rock Failure

    Rowell, GA
    Mechancial engineer, physicists, and mining engineer, U.S. Department of the Interior, Bureau of Mines, Denver Research Center, Denver, Col.

    Brady, BT
    Mechancial engineer, physicists, and mining engineer, U.S. Department of the Interior, Bureau of Mines, Denver Research Center, Denver, Col.

    Yoder, LP
    Mechancial engineer, physicists, and mining engineer, U.S. Department of the Interior, Bureau of Mines, Denver Research Center, Denver, Col.

    Hanson, DR
    Mechancial engineer, physicists, and mining engineer, U.S. Department of the Interior, Bureau of Mines, Denver Research Center, Denver, Col.

    Pages: 25    Published: Jan 1981


    Abstract

    A series of laboratory tests was initiated at the Bureau of Mines to investigate the relevance of brittle rock failure in the laboratory to large-scale failures, such as rock bursts and roof falls in mines. Various parameters that could exhibit anomalous behavior prior to failure were monitored during uniaxial and triaxial compression tests. These parameters included load, moments (corresponding to tilt measurements), seismicity, electromagnetic (EM) radiation, surface charge differential, and confining pressure (during triaxial tests). These variables were recorded for only a few milli-seconds prior to and during failure.

    Our results indicate that laboratory failure of brittle rocks, such as granites and quartzites, must be studied in the microsecond time scale prior to failure; otherwise, laboratory failure appears to be a single catastrophic failure with little or no relevance to large-scale failures. Studied on the microsecond time scale, anomalous activity was observed in the last 10 ms prior to failure. During triaxial compression tests, a large pressure drop was observed just prior to failure, indicating that a criterion for failure may be the violation of the law of mechanical stability.

    Keywords:

    fracture, rock bursts, roof falls, precursors, compression tests, seismicity, earthquakes, composite materials, crack propagation


    Paper ID: STP28307S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP28307S


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