For the sake of investigating the accumulative plastic deformation and its influencing factors of silt with different compaction degrees

moisture contents and stress levels under the repeated loading

a series of dynamic triaxial tests is carried out. According to the relation curves between accumulative plastic strain and loading number，the critical dynamic stresses of silt are obtained. The experimental results demonstrate that the critical dynamic stress values of silt rise with the increase of compaction degree

and in reverse of moisture content.In order to avoid damage of the pavement structure

the stress state of subgrade should be controlled within the boundaries of the critical dynamic stress. In view of this

the test data within the critical dynamic stress is analyzed; and a new accumulative plastic deformation prediction model of subgrade soil is put forward. The model takes into account the influencing factors of stress and loading number. Through regression analysis

a consistency between the predictive results and the experimental data is obtained. It is shown that the model is accurate and credible. The proposed mode can provide parameters for the subgrade accumulative plastic deformation calculation based on mechanics empirical method. For typical cement concrete pavement structure

the accumulative plastic deformation of silty subgrade under different axial loads and axle configurations are obtained; and it can provide ideas for further evaluation of the effect of accumulative plastic deformation on pavement structure.