Dynamic mechanical characteristics of frozen subgrade soil subjected to freeze-thaw cycles

As a widely-applied engineering material in cold regions, the frozen subgrade soils are usually subjected to seismic loading, which are also dramatically influenced by the freeze-thaw (F-T) cycles due to the varying temperature. A series of dynamic cyclic triaxial experiments were conducted through a cryogenic triaxial apparatus for exploring the influences of F-T cycles on the dynamic mechanical properties of frozen subgrade clay. According to the experimental results of frozen clay at the temperature of -10℃, the dynamic responses and microstructure variation at different times of F-T cycles (0, 1, 5, and 20 cycles) were explored in detail. It is experimentally demonstrated that the dynamic stress-strain curves and dynamic volumetric strain curves of frozen clay are significantly sparse after 20 F-T cycles. Meanwhile, the cyclic number at failure (N_f) of the frozen specimen reduces by 89% after 20 freeze-thaw cycles at a low ratio of the dynamic stress amplitude. In addition, with the increasing F-T cycles, the axial accumulative strain, residual deformation, and the value of damage variable of frozen clay increase, while the dynamic resilient modulus and dynamic strength decrease. Finally, the influence of the F-T cycles on the failure mechanisms of frozen clay was discussed in terms of the microstructure variation. These studies contribute to a better understanding of the fundamental changes in the dynamic mechanical of frozen soils exposed to F-T cycles in cold and seismic regions.