Abstract: Most of the existing cyclic triaxial tests on saturated soft clay were conducted under undrained condition because of the very low permeability of soft clay. But as for traffic loading, the actual drainage condition is partially drained because soft clay is subjected to long-term cyclic loading for a series of years. Triaxial tests with large number of cycles (50 000) are conducted under on natural Wenzhou soft clay undrained and partially drained conditions. Influence of drainage condition on dynamic behavior of saturated soft clay is analyzed. Results show that the dynamic behavior of soft clay under partially drained condition is very different from that under undrained condition. With the increasing number of cycles, the pore water pressure firstly increases and then decreases with a peak value. After a large number of cycles, the resilient strain gradually decreases and the stress-strain hysteresis loops under a single cycle shortens with smaller area. It is indispensable to conducting tests under partially drained condition to predict the long-term settlement under traffic loading.

Key words: soft clay, undrained condition, partially drained condition, long-term cyclic loading