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Abstract Freeze-thaw has a great influence on strength characteristics of soil. In this paper，a series of freeze-thaw test on silty clay from the Tibetan Plateau are carried out. Then the soil samples after different runs of freeze-thaw test are used to conduct uniaxial compressive strength tests，scanning electron microscope (SEM) test and mercury intrusion porosimetry(MIP) tests. Results indicated that the uniaxial compressive strength decrease with the increase of freeze-thaw cycles and then keep stable until 30 times of freeze-thaw cycles. Microscopic pore structure parameters including plane porosity，the proportion of four kinds of pore and fractal dimension of pore experience fluctuant adjustment stage and dynamic balance stage during the freeze-thaw cycles. There is a negative correlation between the uniaxial compressive strength and plane porosity. The pore size distribution has changed after few freeze-thaw cycles，and both the pore size and pore density increase during the cycles. During the freeze-thaw cycles，some connected pores and cracks develop in the soil samples. These pore and crack changed the grain skeleton and particle characteristics of the soil，leading to changes in the soil structure and mechanical system. And consequently，the strength of the soil sample decreases. Comparison and combination between SEM tests and MIP tests make the study of soil micro-structure more accurate and effective.
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2015, Vol. 34 
