Three-dimensional drained behavior of normally consolidated anisotropic kaolin clay

A series of consolidated-drained true triaxial tests with a constant mean effective stress and constant Lode angles during shear is performed on cross-anisotropic kaolin clay. All tests are performed in a fully automated true triaxial testing apparatus. The relative magnitude of the intermediate principal stress, expressed in terms of the b-value, and initial cross-anisotropy show significant influence on the stress–strain, strength, and shear band formation characteristics of the clay. Shear bands form and appear to cause failure in all true triaxial tests performed, except in triaxial compression. The initiation and development of shear bands is observed to take place, when the clay undergoes volumetric contraction. The lower strength exhibited in the shear bands is caused by alignment of the clay particles. This shear band mechanism is different from that observed in granular materials, in which the lower shear strength is reached due to dilation in the shear bands.