Dynamic shear modulus and damping ratio of frozen compacted sand subjected to freeze–thaw cycle under multi-stage cyclic loading

• Cryogenic cyclic triaxial performed on frozen compacted sand subjected to freeze–thaw cycles.
• The modified Hardin hyperbolic model was proposed to describe backbone curve.
• Effects of freeze–thaw cycle on dynamic shear modulus and damping ratio were studied.
• Another four key influence factors on dynamic shear modulus and damping ratio were also studied.
• Empirical expressions to estimate dynamic shear modulus and damping ratio were proposed based on experimental observation.

Frozen soil plays an important role on the stability of railway and highway subgrade in cold regions. However, the dynamic properties of frozen soil subjected to the freeze–thaw cycles have rarely been investigated. In this study, cryogenic cyclic triaxial tests were conducted on frozen compacted sand from Nehe, Heilongjiang Province in China which was subjected to the closed-system freeze–thaw cycles. A modified Hardin hyperbolic model was suggested to describe the backbone curves. Then, dynamic shear modulus and damping ratio versus cyclic shear strain were analyzed under the different freeze–thaw cycles, temperatures, initial water contents, loading frequencies and confining pressures. The results indicate that the freeze–thaw process plays a significant effect on the dynamic shear modulus and damping ratio, which slightly change after one freeze–thaw cycle. Dynamic shear modulus increases with increasing initial water content, temperature, loading frequency and confining pressure. Damping ratio increases with increasing initial water content, while decreases with increasing temperature and loading frequency. The effect of confining pressure on the damping ratio was found not significant. Furthermore, the empirical expressions were formulated to estimate dynamic shear modulus and damping ratio of the frozen compacted sand. The results provide guidelines for evaluating the infrastructures in cold regions.