The Effect of Freeze-Thaw on Shear Strength of Roadbed Soil in Different States of Water Content and Soil Density

There are many phenomenon of freeze-thaw instability on the cutting slope in seasonal frozen regions. The main reason is the change of water content and soil density in the roadbed during the process of freezing and thawing, which affect the soil shear strength. Based on this reason, using the method of laboratory test and making detailed test program, the law of soil shear strength vary with water content, soil density and freeze-thaw cycle times was analyzed and summed up. The study results showed that: no matter the state of the water content and soil compaction was, the soil cohesion basically decreased with times freeze-thaw cycle increased, the biggest loss mainly took place in former two freeze-thaw cycle, soil internal friction angle increased after the first freeze-thaw cycle, and then decreased with the times of freeze-thaw cycle increased slightly. Using scanning electron microscopy, the soil micro-structure after the freeze-thaw cycles was studied, which is used to analyze the reason of the change of test results. The conclusions could provide an important reference for slope design and studies of slope freeze-thaw instability in seasonal frozen regions.