Incremental propagation of discrete compaction bands: Acoustic emission and microstructural observations on circumferentially notched samples of Bentheim

[1] To simulate how compaction localization may develop from structural and stress heterogeneity, we studied in the laboratory the influence of a stress concentration due to a V-shaped circumferential notch in a cylindrical sample of Bentheim sandstone. Conventional triaxial experiments at confining pressure of 300 MPa were conducted. Acoustic emission activity was recorded, and each sample was deformed to a different stage and subsequently retrieved for microstructural observations. Our data indicate that compaction bands initiated from the notch tips and propagated by sequential increments as anti-cracks''. The transverse propagation of a compaction band was inferred to be faster than the axial displacement rate by 2 orders of magnitude. Energy dissipated for compaction band formation was estimated to be comparable to the shear fracture energy for shear band propagation.