The mechanism and dynamics of rock fracture upon mechanical impact and electric discharge

The mechanism and dynamics of the deformation and fracture of quartz, granite, and marble samples under the striker blow on their surface and electric discharge inside them are studied by the fractoluminescence (FL), electromagnetic (EME), and acoustic emission (AE) methods with 10-ns resolution. Th...

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Bibliographic Details
Published in:Izvestiya. Physics of the solid earth 2016-09, Vol.52 (5), p.754-769
Main Authors: Vettegren, V. I., Kuksenko, V. S., Shcherbakov, I. P.
Format: Article
Language:English
Subjects:
Acoustic emission
Chemical bonds
Deformation
Earth and Environmental Science
Earth Sciences
Electric discharges
Emergence
Fractures
Geophysics
Geophysics/Geodesy
Granite
Ions
Microcracks
Minerals
Rock
Rocks
Shock waves
Velocity
Wave velocity
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Summary:The mechanism and dynamics of the deformation and fracture of quartz, granite, and marble samples under the striker blow on their surface and electric discharge inside them are studied by the fractoluminescence (FL), electromagnetic (EME), and acoustic emission (AE) methods with 10-ns resolution. The impact excites a forced deformation wave with a velocity within 0.8 to 2 km/s depending on the mineral. The atomic bonds rupture and microcracks are formed at the nodes of the wave, which leads to the emergence of the FL flashes and disruption of the time dependences of EME. Based on the intensity of the flashes, the dimensions of microcracks are estimated to vary from 2 to 70 µm depending on the mineral. In turn, the emergence of microcracks initiates additional deformation waves.The discharge inside the studied samples excites a pressure shock wave which transforms into the tension wave after reflection from the surface. According to the analysis of FL spectra, this leads to the breakdown of the rocks into positively charged ions and electrons. The shock wave velocity in granites is measured at 4.8 km/s, which is close to the velocity of the longitudinal acoustic vibrations ~5 km/s. The microcracks in the rock have not enough time to form with this loading velocity. It is supposed that the shock wave stretches the deformed interatomic bonds at the dislocation nuclei in the crystal lattices of the minerals up to their breakdown into positively charged ions.
ISSN:1069-3513
1555-6506
DOI:10.1134/S106935131604011X