Abstract: The freeze-thaw cycle tests are carried out under different compacted degrees and initial moisture contents to explore the mechanism and the influence of the long-term strength of improved silt under freeze-thaw cycle effect. And then, unconfined compressive strength tests after different freeze-thaw cycles are conducted. The influence law of the long-term strength of improved silt subjected to freeze-thaw cycle effect is discussed. It is found that the unconfined compressive strength decreases with the number of freeze-thaw cycles increasing. Finally, it reaches a stable stage after 6 freeze-thaw cycles. The higher initial moisture is, the more attenuation amplitude of the compressive strength is after the same number of the freeze-thaw cycles. In order to find out the influence law of the microscopic structure under the effect of freeze-thaw cycles, the microscopic tests of improved silt are carried out. And then the damage mechanism of the microscopic structure under the effect of freeze-thaw cycles is found out. It shows that different numbers of freeze-thaw cycles and initial moisture contents have less effect on the small pores ( 10 nm). Freeze-thaw cycles have main influence on the large pores (0.01～100 μm) between the soil aggregates, so it makes the strength of improved silt decreased.

Key words: improved silt, freeze-thaw cycles, long-term strength, pore distribution