Characterization of damage processes in Montney siltstone under triaxial compression using acoustic emission and diagnostic imaging
Date
2021-11-04
Authors
Journal Title
Journal ISSN
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Publisher
Oxford University Press
Abstract
Crack nucleation and rock failure processes in a fine-grained siltstone (Montney Formation) under triaxial compression are investigated using combined diagnostic techniques, including ultrasonic-wave measurement, acoustic-emission (AE) monitoring, computed tomography (CT) scanning, and thin-section imaging. The sample displays a weak-to-moderate inherent seismic anisotropy and noticeable stress-induced anisotropy prior to failure. No AE event was detected until the applied axial stress reached 95% of the peak value. The signal-to-noise ratio is relatively low, however, and detectable AE events are more diffuse than those observed in highly brittle rocks. The AE locations correlate with a shear fracture zone imaged by CT scanning. AE moment-tensor analysis reveals that events with larger relative magnitudes are characterized by high volumetric (tensile or compressive) components, and the initiation of the failure zone is dominated by combined shear-tensile failure. Stress inversion of the AE events with high tensile components is in good agreement with the known applied stress. Microscopic imaging of thin sections from the failed sample shows that the failure zone is an en echelon structure consisting of a major fracture with branching micro and minor cracks. This failure mechanism is consistent with a shear-tensile source mechanism and is interpreted to be associated with the fine granular structure and mineral composition of Montney siltstone.
Description
Article accepted for publication by Geophysical Journal International
Keywords
acoustic emissions, geomechanics, geophysics, Montney Formation
Citation
Jia, S. Q., Wong, R. C. K., and Eaton, D. W. (2021). Characterization of damage processes in Montney siltstone under triaxial compression using acoustic emission and diagnostic imaging. Geophysical Journal International, ggab455. https://doi.org/10.1093/gji/ggab455