Abstract: Graded macadam fillings, the core filling of heavy haul railway subgrade bed is most affected by the train loading. Therefore, it is particularly important to study the dynamic behavior and accumulative plastic strain evolution characteristics of graded macadam filling under cyclic loadings. Firstly, graded macadam fillings with different fine particle contents were prepared, and a series of large-scale dynamic triaxial tests was conducted to explore the coupling influence mechanism of fine particle content, confining pressure, and dynamic stress amplitude on the specimen accumulative plastic strain under cyclic loadings. Additionally, based on the plastic stability theory, the dynamic behavior of specimens under different stress levels was determined, and the calculation model of critical dynamic stress in the plastic creep state was obtained considering the parameters of confining pressure and fine particle content. Finally, in combination with the experimental data, an accumulative plastic strain prediction model was established considering the stress level and fine particle content parameters for the dynamic behavior of plastic creep, and the physical meaning of each parameter was clarified. The research results can provide a reference for the health status assessment of existing heavy haul railway subgrades and the subgrade structure design considering the comprehensive control of strength and deformation.

Key words: heavy haul railway subgrade bed, graded macadam, accumulative plastic strain, critical dynamic stress, prediction model