Abstract: A series of undrained cyclic triaxial tests under coupling effects of cyclic deviator stress and cyclic confining pressure is conducted on Ningbo remoulded saturated soft clay by using GDS cyclic triaxial system. The coupling effects of cyclic deviatoric stress and cyclic confining pressure on undrained dynamic behaviors are studied. The influences of cyclic confining pressure and vibration frequency on permanent axial strain and pore pressure are further analysed. The experimental results show that under undrained condition, coupling of cyclic deviator stress and cyclic confining pressure limits the development of the cumulative plastic strain of saturated soft clay to some extent. With the increasing of the slope of loading paths ? and vibration frequency f, the permanent axial strain decreases. The relationships between permanent axial strain rate and cyclic time are identical under different stress paths and frequencies. The relationship between strain rate and cyclic time are more obviously affected by the slope of loading paths ? comparing with the loading frequency, and the strain rate decreases with the increase of ?. However, the curves of strain rate under different vibration frequencies almost coincide with each other. On the other hand, the maximum pore water pressure increases with the increase of cyclic confining pressure and decreases with the increase of vibration frequency. Based on the test results, a linear relationship between the permanent strain rate and cyclic time is established in log-log scale coordinates system.

Key words: Ningbo clay, cyclic confining pressure, vibration frequency, cumulative axial strain, strain rate, pore pressure