Abstract: With the increasing distribution of railway lines in the seasonally salinized frozen soil area in Northwest China,more and more railway engineering diseases caused by the freezing and thawing cycle of sulfate saline soil have been caused.To explore the strength and deformation difference of the interface between saline soil and concrete under freeze-thaw cycles,this paper considered the interface of sulfate rich silty clay and concrete as the research object.The concrete and the sodium sulfate saline soil with the salt content of 0,1%,2%,3%,and 4% were tested for 1,3,6,and 10 freeze-thaw cycles at ±20℃,with 12 hours of freezing and thawing as a cycle.After the cycle,the monotonic direct shear and scanning electron microscope tests were carried out on the interface under constant temperature of 20℃.The influence of freeze-thaw cycles and salt content on the characteristics of the interface was analyzed from the aspects of shear strength,deterioration proportion,volume deformation characteristics and microstructure.The results show that the shear strength of the interface between saline soil and concrete decreases with the increase of freeze-thaw cycles.The degree of decline gradually decreases with the increase of cycles.In any damage process,the deterioration effect of salt erosion on the interface between saline soil and concrete is more obvious than that of freeze-thaw.Under the condition of 4% salt content,dilatancy is appeared in the interface,and shear shrinkage is shown in other cases.The larger the number of freeze-thaw cycles,the more obvious the phenomenon of shear shrinkage.The scanning electron microscope test shows that the freeze-thaw cycles reduce the integrity of the soil particles at the interface.The interfacial soil porosity increases under the action of freeze-thaw cycles.After the freeze-thaw cycles for 6 times,the change range of the pore area decreases,the small pores between the particles increase,and the soil particle distribution is more uniform.