LAUSR

Abstract The transportation infrastructure built in cold regions is mostly above frozen soil, whose stability is of concern, and which has been studied as a subgrade for highways and railways. Based on cryogenic cyclic dynamic triaxial tests, the subgrade frozen silt from the Qinghai-Tibet Plateau is taken as a research object. The dynamical characteristics of frozen silt are analyzed under different freezing temperatures, initial moisture contents, compaction degrees, and confining pressures. The results show that a hyperbolic constitutive model can well express the dynamic stress-strain response relationship of frozen silt under external dynamic loading. The dynamic shear modulus increased with decreasing freezing temperature, increasing moisture content, compaction degree, and confining pressure; the damping ratio had exactly the opposite relationship; and frozen silt energy consumption was gradually weakened. However, when the moisture content exceeded a certain threshold (11.4%), the damping ratio tended to increase instead. The unfrozen moisture content of frozen silt under different water contents was measured, which proved that the dynamic shear modulus increased due to the increase of ice crystals. In addition, variance analysis was introduced to analyze the significant influences of mechanical parameters. Four experimental conditions were compared for the influence volatility of the maximum dynamic shear modulus, final shear strain amplitude, and maximum damping ratio. Obviously, the dynamic properties of frozen silt were influenced by the freezing temperature and moisture content, followed by the compaction degree and confining pressure. Finally, the empirical formulas of the dynamic shear modulus and damping ratio were established by verifying the reliability and analyzing the experimental results.