Influence of freeze-thaw cycles on dynamic characteristics of subgrade soils with different plasticity indices

The specimens with the maximum degree of compaction are prepared. Dynamic triaxial tests are carried out on the specimens under different confining pressures after 0 to 7-time complete freeze-thaw cycles. The test results show that at the initial stage, the dynamic moduli of the soils (including dynamic elastic modulus and dynamic shear modulus) exhibit a downward trend with the increase of the loading cycles. As the number of dynamic loads continues to increase, the dynamic modulus is stable. By taking the average dynamic moduli of 5000 to 6000 loading cycles as the soil dynamic properties in this state, the laws are summarized as follows: the dynamic moduli of the compacted soils in seasonally frozen region increase with the increase of the confining pressure, decrease with the increase of the number of the freeze-thaw cycles, and increase with the increase of the plasticity index. The damping ratio has no obvious rules to follow with the freeze-thaw cycles, confining pressure and plasticity index. The relationship among the dynamic moduli, confining pressure, plasticity index and number of freeze-thaw cycles is obtained though data analysis. It may provide a reference for the embankment design and construction in the seasonally frozen region.