Effects of strain rates on the undrained shear strength of kaolin

In recent times, for deep sea construction, interest in dynamically installed foundation systems has increased. These foundation systems are still under development and need quantification of various soil parameters with different perspective. For the design of dynamically installed foundations it is essential to assess the effect of strain rate on very soft soils. The T-bar has been widely used to characterise soft offshore sediments such as silt and clay and there is extensive existing literature on the interpretation of test results. Strain-rate dependence has not previously been fully examined for T-bar tests for very soft clay at very high rates of penetration. This paper examines this aspect using a physical model test. A 65 cm thick kaolin clay bed was formed using vacuum consolidation. A T-bar was penetrated into the clay bed at rates which varied from 0.1 cm/s to 60 cm/s. The tests revealed that the bearing capacity factor increased by 9 % for every 10 fold increase in penetration rate for the material tested in this research.