Abstract: By using the GDS dynamic triaxial apparatus tests, the effect of freeze-thaw cycles on dynamic stress, dynamic modulus, dynamic modulus ratio and damping ratio of silty sand under different negative temperatures has been investigated in this study. It is found that under the same dynamic strain, the freeze-thaw cycles are negatively correlated with dynamic stress and dynamic modulus, but positively correlated with dynamic modulus ratio and damping ratio. With the increasing of freeze-thaw cyclic numbers, the dynamic stress and dynamic modulus decrease while the dynamic modulus ratio and damping ratio increase. The normalized fitting models for the dynamic modulus ratio versus the shear strain and the damping ratio versus the shear strain have been presented by regression analysis. The freeze-thaw cycles have a significant effect on the initial dynamic modulus and the maximum damping ratio. With the increasing of freeze-thaw cyclic numbers, the initial dynamic modulus decreases and the maximum damping ratio increases. The effects of freeze-thaw cycles on the initial dynamic modulus and the maximum damping ratio under different negative temperatures have also been analyzed, and the calculation formulae of the number of freeze-thaw cycles correlation coefficients have been given. The results indicate that the effect of freeze-thaw cycles on dynamic characteristics of silty sand is obvious with decreasing of the temperature, and the dynamic characteristics after five freeze-thaw cycles are relatively stable. It is suggested that the dynamic parameters after five freeze-thaw cycles can be used as the basic parameters for the dynamic response analysis.

Key words: freeze-thaw cycles, silty sand, dynamic characteristics, dynamic modulus, damping ratio