Abstract: Interface seepage under freeze-thaw environments is a critical factor influencing the structural stability of hydraulic engineering in seasonally frozen soil regions. To reveal the seepage characteristics and microstructural evolution of the silty clay–concrete interface under freeze-thaw cycles, fluorescein tracer and scanning electron microscope tests were carried out under different freeze-thaw cycles. The results show that at the microscopic level, cracks develop between soil and concrete under the action of freeze-thaw cycle. With an increasing number of freeze-thaw cycles, the soil porosity initially decreases and then increases, reaching a minimum of 17.00% at the 25th cycle, and the soil at the interface disintegrates into platy minerals after seepage. At the macro level, the moisture content of soil and concrete within the region from 20 mm below to 10 mm above the interface increases, and the moisture content decreases first and then increases with the increase of the number of freeze-thaw cycles, and the soil wetting front migration velocity is positively correlated with the number of freeze-thaw cycles.

Key words: freeze-thaw cycle, silty clay-concrete interface, seepage, microstructure