Abstract: The effect of drainage conditions on the accumulated axial strain and pore pressure of the soft clay under traffic load are investigated by using the GCTS true triaxial system. A series of cyclic triaxial tests are conducted on the undisturbed Ningbo soft clay under the undrained and partially-drained conditions with different cyclic stress ratio. The results show that accumulated axial strain of the clay increases with cycles during loading. Regardless of the drainage conditions, axial strain gradually grows with vibration times and tends to be stable under a particular cyclic stress ratio that is the critical cyclic stress ratio and equals 0.25~0.30. Under different drainage conditions, the pore pressure has different development patterns. With the increasing number of cycles, the pore pressure firstly increases and then decreases with a peak under the partially drainage condition, however, the pore pressure increases gradually with cycles and tends to be stable under undrained condition. Based on the test results, the empirical equation between accumulated axial strain and vibration times is obtained. No matter how drainage conditions, the variation of fitting parameter with the cyclic stress ratio match the linear functions.

Key words: Clay, Traffic Load, Partially Drainage, Undrained, Dynamic Characteristics