Dynamic triaxial tests for different cycle loading modes were carried out on the④2 layer silty clay of Ningbo rail transit

and the pore pressure

cumulative shaping strain and dynamics of the clay under one-way load vibration mode and two-way load vibration modes were obtained.Also an exponential function of pore pressure and vibration frequency

and cumulative plastic strain and vibration frequency was established.The results show that the difference of static deviator stress is the essential difference between the two vibration modes;the number of vibrations required for the stability of pore pressure under unidirectional tension and pressure vibration is greater than that of one-way pure pressure

and the cumulative plastic strain ratio is more than one-way pure pressure.The vibration is an order of magnitude smaller;the elastic strain generated by the unidirectional tension and compression vibration is greater than the unidirectional pure pressure vibration

and the dynamic elastic modulus is the reverse;the exponential function established to describe the relationship between the pore pressure

cumulative plastic strain and the number of vibrations revealed greatly the variation of pore pressure and cumulative plastic strain slope with the number of vibrations.The research results can provide a theoretical basis for rail transit design and construction.