Abstract: The varying cyclic confined pressures will aggravate the pore water pressure and the accumulated plastic strain of soil and even lead to the catastrophic accident. The triaxial tests with cyclic confining pressure were carried out to study the pore pressure, the axial cumulative plastic strain and the volumetric strain of saturated silty clay under different stress paths and cyclic dynamic stress ratios by using GDS triaxial apparatus under partial drained conditions. A mathematical model of accumulated strain for silty clay under cyclic confining pressure and cyclic dynamic stress was established under partial drainage conditions. The experimental results show that the pore water pressure, axial cumulative plastic strain and volumetric strain of the saturated silty clay increase as the cyclic dynamic stress ratio and the stress path slope increases. The dynamic pore pressure ratio versus vibration number curves divided into three stages: rapid increase stage, rapid decline stage and sustained stability stage, respectively. The axial cumulative plastic strain and volumetric strain increase as the vibration number increases. The pore pressure of silty clay tends to be stable, while the deformation rate decreases slightly, but the deformation increases continuously when the number of loading is more than 2 500 times. The supplementary experimental results show that the established model is in good agreement with the experimental results. The results will provide a theoretical basis for the foundation disaster control technology caused by traffic cycle load.

Key words: soil mechanics, variable confining pressure, saturated silty clay, axial cumulative plastic strain, stress path ratio, cyclic dynamic stress ratio