ABSTRACT
This study examines what measuring devices can best be used to measure the undrained shear strength of very soft, clay-rich sediments that are in between solid and fluid states. Although in recent years interest in these sediments for construction purposes has been growing, little information is currently available on what laboratory testing devices can be used for this purpose. In this study, kaolinite-based clay samples are prepared at different liquidity index values (in the range of 0.4 to 1.9) and tested using a Fall Cone, Lab Vane, and Direct Simple Shear device. The results show that the measured shear strength (in the transitional range of 1-10 kPa) strongly depends on the applied test conditions. The Fall Cone and Lab Vane tests provide shear strength values in the same order of magnitude. The measured strength values from Direct Simple Shear testing depend on the applied consolidation stress level but are typically lower compared to the Fall Cone and Lab Vane tests. The findings of this research indicate that the results of different devices converge when the testing conditions are moved closer together. A full overlap of the results is not likely possible as it would require the test conditions to be pushed outside the validated range of operations or simply because some test conditions are inherent to the type of test.
