Abstract: The dynamic characteristics of silty clay and the stability of soil structure are directly affected by long-term dynamic loading. The plastic strain and residual pore pressure of silty clay under different loading conditions are examined by controlling consolidation confining pressure, dynamic stress ratio and vibration frequency under 20 000 cyclic vibrations on SDT-10 dynamic triaxial apparatus. Results show that the cumulative plastic strain and residue pore pressure are significantly affected by three load conditions. Cumulative plastic strain accumulates under continuous dynamic loading, and the curve displays S-shape and J-shape. The improved population growth model and the improved exponential model could well fit the changes of cumulative plastic strain against vibration number: cumulative plastic strain changes in a positive relationship with the growth of confining pressure and dynamic stress ratio, but is inversely proportional to the increase of frequency. Residual pore pressure ratio increases continuously under the vibration of sine wave. The improved Seed pore pressure model could, to a certain degree,simulate the change rule of residual pore pressure ratio, which increases with the growth of dynamic stress ratio and frequency, while decreases with the climbing of confining pressure.The research results enriched our understanding on clayey soil deformation under dynamic conditions, and offered reference for predicting the strength decay and deformation of soil under long-term cyclic loading.

Key words: silty clay, dynamic characteristic, dynamic triaxial test, plastic strain, residual pore pressure ratio