Acoustic Emission Technology to Investigate Internal Micro-Structure Behaviour of Shear Banding in Sands

Current experimental techniques used to understand the shear banding process in sands provide little insight into the internal micro-structure evolution. To this end, Acoustic Emission (AE), as a non-destructive testing technique, was proposed in this paper with great interest in characterizing the internal micro-structure response leading to the evolution of shear bands formed in laboratory triaxial compression. Silica sand was used to conduct consolidated-drained triaxial compression tests at a constant axial strain rate under an effective confining pressure of 100 kPa. AE events were collected and analyzed. Insights regarding relations of the deviatoric stress, source rates and dissipated energy rates of AE events with the increasing global axial strain are offered. The result indicated that with the increase of relative densities, the evolution envelope of AE source rates transits from a steep shape to a flat shape, and total amount of AE source events decreases gradually. According to the evolution of AE energy rate, shear banding process can be divided into four stages in terms of O-A, A-B, B-C and C-D, corresponding to the strain hardening regime, incipient strain softening regime, highest rate of strain softening regime and residual stress regime. From which point A could be considered as an omen of the initiation of strain localization, point B as the initiation of visible shear band and point C as the completion of shear banding. AE technologies can be provided as an alternative means to clarify and indicate the initiation and evolution of shear banding in sand.