A laboratory study of normally consolidated kaolin clay

In recent years many researchers have attempted to address the need for a comprehensive understanding of the three-dimensional mechanical behavior of frictional materials. Advances in testing methods have added the capability of studying various aspects of generalized stress-strain behavior in a controlled environment. Strain-controlled true triaxial undrained tests on normally consolidated kaolin clay are performed in this study using a fully automated flexible boundary experimental setup with a real-time feedback control system. The influence of the intermediate principal stress and principal stress rotation on the stress-strain-strength and pore pressure behavior is investigated considering the occurrence of strain localization within the specimen. The strength behavior observed in this study of kaolin clay is used to evaluate existing failure criteria for cohesive soil. Comparative laboratory tests, such as the lubricated end triaxial test on a solid cylindrical kaolin specimen and combined axial-torsional tests on a hollow cylindrical kaolin specimen, were also performed to evaluate the corresponding mechanical behavior in different loading systems. Despite using identical techniques for specimen preparation and a similar consolidation stress state, the soil behavior obtained from the three types of tests showed observable variations, demonstrating the importance of specimen shape and loading-boundary conditions.