The stiffness anisotropy of soil is a critical factor that influences the deformation characteristics of soil in landform evolution, geological disaster mitigation and engineering applications. However, the effects of freeze-thaw cycles on the stiffness anisotropy of soil have not been clearly understood. In this study, a new thermal boundary-controlled triaxial testing system equipped with bender elements is developed to investigate the effects of cyclic freeze-thaw on the stiffness of a sandy silt under both unidirectional and all-round freezing modes. It is revealed that under all-round freeze-thaw cycles, the shear wave velocity in the horizontal and vertical planes undergoes a continuous increase of 14% and 8%, respectively. In contrast, unidirectional freeze-thaw leads to a non-monotonic evolution of shear wave velocity, eventually resulting in a 3% reduction in the horizontal plane and a 16% reduction in the vertical plane after 10 freeze-thaw cycles. The increase in shear stiffness anisotropy of the sandy silt after freeze-thaw cycles is more significant in the unidirectional freeze-thaw condition (from 1.11 to 1.49) compared with the all-round freeze-thaw condition (from 1.13 to 1.19). This study illustrates the significance of unidirectional freeze-thaw in the evolution of mechanical anisotropy of soils in cold regions.

来源平台：CATENA