Experimental study on the dynamic behavior of expansive soil in slopes under freeze-thaw cycles

To study the dynamic shear modulus and damping ratio of expansive soil in high railway embankment slope engineering structures after freeze-thaw cycles, temperature-controlled dynamic triaxial testing of expansive soil under freeze-thaw cycles was carried out under confining pressures of σ₃ = 10 and 50 kPa and an anisotropic consolidation ratio. The results show that the dynamic characteristics of expansive soil in slopes under freeze-thaw cycles vary significantly with the stress state. Freeze-thaw cycles cause the consolidation of expansive soil under confining pressure, increasing the dynamic shear modulus G_d and decreasing the damping ratio λ. In a single freeze-thaw cycle, G_dmax increases by a maximum of 27.6%, and λ_max decreases by 7.6%. This result is different from the traditional understanding of frost heave and thaw soil structure damage theory. Under the action of deviatoric stress, the freeze-thaw cycle causes additional shear deformation of the expansive soil, thereby increasing the dynamic shear modulus of the soil.