Abstract: Baotou city of Inner Mongolia is a typical region with seasonal frozen soil where frost heaving and thawing is the main cause of frozen soil damage. The influence of cyclic freezing and thawing on the shear strength of silty soil was investigated by establishing the quantitative relationship of cohesion and internal friction angle against freeze-thaw cycle parameters. Moisture content, dry density, and number of freeze-thaw cycle were controlled in the test. Results showed that cohesion decreased steadily as cyclic freezing and thawing proceeds regardless of dry density and moisture content of soil specimen; internal friction angle stabilized with the proceeding of cyclic freezing and thawing, fluctuating within a range of 5°; shear strength of silty soil was mostly affected by cohesion. In addition, finite element analysis was carried out with geotechnical software, and the safety factor of slope was calculated by the reduction coefficient method. The research is expected to offer better theoretical basis for researching the seasonal frozen soil in Baotou.

Key words: frozen soil, slope stability, cyclic freezing and thawing, cohesion, internal friction angle, shear strength, reduction coefficient method