Freezing and thawing process

as a weathering process

is very common in the Northwest China. It repeatedly changes the microstructure and physical properties of the soil

and strongly affects the interaction between soil and structure. In view of the influence of freezing and thawing on the mechanical properties of salinized soil-structure contact surface

the shear tests under unconsolidated and undrained conditions were applied

considering the effects of freezing and thawing cycles

salt content

matrix suction and other factors on the mechanical properties of unsaturated chloride salinized soil-steel interfaces. The results showed that when the salt was not contained in the soil

the mechanical parameters (e.g. cohesion and internal friction angle) of the interface increased at first and then they decreased with the increase in the number of freezing-thawing cycles. When the salt was contained in the soil

the cohesion of the interface between the salinized soil and steel decreased

but the internal friction angle slightly increased with the increase in the number of freezing-thawing cycles. Before and after freezing and thawing

the mechanical parameters of the interface decreased at first and then increased with the increase in salt content

including threshold values of salt contents. Before the freezing-thawing process

the mechanical parameters of the interface have a salt threshold value of 8%. When the number of the freezing-thawing cycles increases

the threshold changes. The suction force of the matrix at the interface generally decreased with the increase in cycles of freezing-thawing process and it eventually stabilized. It firstly decreased and then increased with the increase in the salt content. The salt threshold of matrix suction is approximately 10%. The shear stress-shear displacement of the interface presented two stages including the linear elastic deformation and strengthening stages. When the vertical load is small

the shear stress-displacement curves show weak hardening characteristics

and no obvious strain-softening phenomenon occurs.Therefore the applicability of the shear stress-shear displacement modes at the interface were evaluated and it is found that the Gongpaz model can be well matched with the experimental results. Thus the mechanical model of chlorine salinized soil-steel block interface was established and its reliability was also verified by the experimental data.