The fill-cut transition section subgrade (FCTSS) is a weak point in subgrade damage. Indoor experiments were conducted to clarify the deformation damage mechanism. It was found that repeated dynamic load leads to upward migration of moisture along the fill-tangent interface and the formation of moisture migration channels. The overall moisture of the soil samples increased under the condition of continuous moisture migration and aggregation. The increase in moisture weakened the strength of the soil, resulting in an increase in moisture accumulation in the region corresponding to the location of greater compressive deformation, which is also the location where damage occurred. Therefore, in order to prevent the effect of dynamic load on the deformation damage of the subgrade, the external recharge of FCTSS should be controlled. This study can provide a valuable reference for the construction and protection of subgrade in the fill-cut transition section in loess areas.
