Characterization of damage processes in Montney siltstone under triaxial compression using acoustic emission and diagnostic imaging

SUMMARY 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, thin-section imaging. The sample displays weak-to-moderate inherent seismic anisotropy noticeable stress-induced prior to failure. No AE event was detected until the applied axial stress reached 95 per cent of peak value. signal-to-noise ratio is relatively low, however, detectable events more diffuse than those observed highly brittle rocks. locations correlate with shear fracture zone imaged by CT scanning. moment-tensor analysis reveals that larger relative magnitudes characterized high volumetric (tensile or compressive) components, initiation dominated shear-tensile (ST) Stress inversion tensile components good agreement known stress. Microscopic imaging thin sections from failed shows an en echelon structure consisting major branching micro minor cracks. This mechanism consistent ST source interpreted be associated fine granular mineral composition Montney siltstone.