Accumulated permanent strain and critical dynamic stress of frozen silty clay under cyclic loading

A series of dynamic triaxial experiments have been conducted to study the dynamic properties of the frozen soil from the subgrade along the Qinghai-Tibet Railway. Under long term cyclic loading, the effects of initial stress state and stress level on cumulative permanent strain and critical dynamic stress were studied in the paper. The results indicate that the influence of dynamic amplitude on the curve of cumulative permanent strain versus cyclic loading number is significant. Besides, based on the shakedown concept, curves of cumulative permanent strain versus cyclic loading number under different initial mean stress and deviatoric stress can be separated to three possible categories of plastic shakedown, plastic creep and incremental collapse. In addition, the critical dynamic stress of frozen soil under specific condition is obtained, and the analysis on critical dynamic stress at different stress state is presented. Therefore, this study could provide an innovative approach for permanent deformation behavior analysis. Furthermore, it is important for practical design and evaluation on stability of frozen soil in the subgrade.