Fracture Toughness Measurements and Acoustic Emission Activity in Brittle Rocks |
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Authors: | M H B Nasseri B Mohanty R P Young |
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Institution: | (1) Lassonde Institute, Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4, Canada |
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Abstract: | Fracture toughness measurements under static loading conditions have been carried out in Barre and Lac du Bonnet granites.
An advanced AE technique has been adopted to monitor real-time crack initiation and propagation around the principal crack
in these tests to understand the processes of brittle failure under tension and related characteristics of the resulting fracture
process zone. The anisotropy of Mode I fracture toughness has been investigated along specific directions. Microcrack density
and orientation analysis from thin section studies have shown these characteristics to be the primary cause of the observed
variation in fracture toughness, which is seen to vary between 1.14 MPa.(m)1/2 and 1.89 MPa.(m)1/2 in Barre granite. The latter value represents the case in which the crack is propagated at right angles to the main set of
microcracks. The creation of a significant fracture process zone surrounding the propagating main crack has been confirmed.
Real-time imaging of the fracture process and formation of fracture process zone by AE techniques yielded results in very
good agreement with those obtained by direct optical analysis. |
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Keywords: | Mode I fracture toughness anisotropy acoustic emission fracture process zone microcrack density microcrack orientation |
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