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    Volume 40, Issue 1 (January 2017)

    Laboratory Determination of Rock Fracture Shear Stiffness Using Seismic Wave Propagation and Digital Image Correlation

    (Received 12 February 2016; accepted 28 September 2016)

    Published Online: 2017

    CODEN: GTJODJ

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    Abstract

    Seismic wave propagation and digital image correlation were used during direct shear experiments on Indiana limestone specimens to investigate the stiffness of rock discontinuities (fractures) approaching shear failure. An instrumented direct shear apparatus was used to apply shear stress to the discontinuity. Compressional and shear wave pulses were transmitted through and reflected from the discontinuity, whereas digital images of the specimen surface were acquired during the test. To measure the dynamic shear stiffness of the rock discontinuities, the displacement discontinuity theory was used and the stiffness was calculated based on the ratio of transmitted to reflected wave amplitudes. The static shear stiffness was calculated based on the ratio of an increment in the applied shear stress to the corresponding increment of relative shear displacement (slip) along the discontinuity. The dynamic shear stiffness measured by seismic wave propagation showed roughly five to ten times greater magnitude than the static values measured by digital image correlation technique. This observation is found to be in agreement with available studies indicating that the frequency-dependent fracture stiffness arises from probabilistic and spatial distributions of stiffness and that dynamic moduli are typically greater than the static values.


    Author Information:

    Hedayat, A.
    Dept. of Civil and Environmental Engineering, Colorado School of Mines, Reza Hedayat Colorado School of Mines, Golden, CO

    Walton, G.
    Department of Geology and Geological Engineering, Colorado School of Mines, Colorado School of Mines, Golden, CO


    Stock #: GTJ20160035

    ISSN:0149-6115

    DOI: 10.1520/GTJ20160035

    Author
    Title Laboratory Determination of Rock Fracture Shear Stiffness Using Seismic Wave Propagation and Digital Image Correlation
    Symposium ,
    Committee D18