Characterization of Clay Sedimentation Using Piezoelectric Bender Elements

Sedimentation is one of the most basic processes in the formation of a soil structure in nature. Many studies have been performed to describe the characteristics of clay sedimentation, based on settlement and water content measurement. In addition, there have been some attempts in numerical modeling to describe soil structure formation as a whole. However, these effects still fall short in explaining the overall process of soil structure formation because some relevant properties are measured after a self-weight consolidation is completed. Furthermore some measurement techniques significantly alter soil structure. Thus, a non-destructive evaluation is necessary for the effective description of soil characteristics during the sedimentation process. In this study, a testing device is designed that continuously monitors the self-weight consolidation process of sedimentation with shear waves. Piezoelectric bender elements are installed into a testing cell to generate and receive shear waves in a small strain regime. Slurries are prepared with kaolinite-type clay and placed in the cell. Shear wave velocities are continuously measured as a function of time during the whole process of the self weight consolidation. The experimental results suggest that as clay sediment is subjected to a certain loading, the shear wave velocity increases as time increases, showing an abrupt change in log time. This abrupt change is relevant to the formation of a stable soil skeleton. It is concluded that the time-dependent variations in shear wave velocity reflect sedimentation and self weight consolidation behavior and the evolution of the effective stress increment.