(1. Key Laboratory for Health Monitoring and Control of Large Structures in Hebei Province，Shijiazhuang Tiedao University，Shijiazhuang，Hebei 050043，China；2. Collaborative Innovation Center for Performance and Safety of Large-scale Infrastructure，Shijiazhuang Tiedao University，Shijiazhuang，Hebei 050043，China；3. State Key Laboratory for Geomechanics and Deep Underground Engineering，China University of Mining and Technology，Xuzhou，Jiangsu 221008，China；4. School of Civil Engineering，Shijiazhuang Tiedao University，Shijiazhuang，Hebei 050043，China)
Abstract：During the process of freezing and thawing，temperature-induced changes in the content of unfrozen water and ice affect the dynamic properties of the soil. Based on this，taking into account the actual operation conditions of trains，this study employed unsaturated silt，a fine-grained filler commonly used in the subgrade of the Shuozhou-Huanghua Port Heavy-Haul Railway，and conducted nuclear magnetic resonance (NMR) and temperature-controlled dynamic triaxial tests on samples with different initial water contents (10%，14%，and 18%) during both freezing and thawing processes. The aim was to analyze the relationships of the unfrozen water content and ice content with dynamic elastic modulus of unsaturated silt during freezing and thawing，thus to explore the impact of phase changes between ice and water on macro-dynamic properties. The main conclusions are as follows. (1) During the freezing process，from the freezing temperature to the supercooling temperature，the unfrozen water content decreases significantly，while the ice content and dynamic elastic modulus increase rapidly. Subsequently，as the temperature continue to drop，the unfrozen water content decrease slowly，and the ice content and dynamic elastic modulus increase gradually. Limited water phase changes occur during the subsequent freezing to －15 ℃，and approximately 1% of liquid water remains in all samples. (2) When the soil is in a thawed state，due to the lubricating effect of free water，the dynamic elastic modulus decrease as the initial water content increases. In the frozen state，the dynamic elastic modulus of the sample with an initial water content of 14% is the highest due to the ice cementation effect and the different modes of ice distribution within the sample. The dynamic elastic modulus of the sample with an initial moisture content of 10% is slightly lower，while the sample with an initial water content of 18% exhibit the lowest dynamic elastic modulus. (3) All three groups of samples exhibit an inverse relationship between the dynamic elastic modulus and the unfrozen water content，and a direct relationship with the ice content during the freezing and thawing processes.
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2024, Vol. 43 
