Shear Band Characterization of Triaxial Sand Specimens Using Computed Tomography

A thorough quantitative analysis of the internal density distribution and strain localization of axisymmetric triaxial sand specimens is presented. Computed tomography technique was used to acquire detailed three-dimensional images of a series of Ottawa sand specimens subjected to Conventional Triaxial Compression (CTC) conditions at very low effective stresses in microgravity and terrestrial laboratories. Analysis tools were developed to quantify the distribution of local void ratio, track the onset, propagation, thickness, and inclination angle of shear bands, and calculate the variation of void ratio within and outside shear bands. It has been found that shear bands initiate in the post-peak strength regime in CTC specimens, where a rather complex pattern of shear bands develops such that behavior is highly influenced by large-scale kinematics of the specimen. Four main deformation patterns were identified and their contribution to the overall volume change of the specimens was quantified.