Propagation and Evolution of Strain Localization in Clay

This research focuses on propagation and evolution of strain localization in clay. To this end, an undrained plane strain compression test program was performed to investigate the effects of the past stress history and strain rates on the strain localization response of kaolin clay. Results of a single test (T3) are presented herein. They include the overall global stress/pore pressure versus axial strain response, as well as indicators of propagation and evolution of strain localization. The results indicate that the response consisted of the three distinct phases: (1) a homogenous deformation, (2) an inception and propagation of strain localization, and (3) an evolution of strain localization within the shear band. The Lagrange strain tensor was used to obtain local volumetric and shear strains developed within the shear band during the evolution stage. It was found that local volumetric and shear strains reached 80% and 200% respectively, which corresponds to a global axial strain increment of only 1.7%. Furthermore, the shear band exhibited a decreasing tendency to compress, thus resulting in its incremental dilatancy angle varying from initially −24° to a final value of −6°.