Effect of Freeze-Thaw Cycles on Slope Stability in Cold Climates

Freeze-thaw cycles are closely related to the slope instability in the seasonally frozen areas. During winter, soil moisture content decreases forming ice segregates, which increase the stability of the slope. The slopes are the strongest in the winter when ice forms. However, when the ice melting starts in the spring season, formation of stagnant water lubrication between the melting soil and freezing soil interface constitutes the weak interface of landslide hazard. As temperature starts increasing, the ice melts and the soil moisture content increases dramatically. The excessive moisture content generates porewater pressure and reduces soil strength, which contributes to slope failure. In this study, a numerical model using GeoStudio has been developed to simulate freeze and thaw condition in a shallow slope. TEMP/W and SEEP/W modules are used to perform coupled conductive thermal analysis, which generates both heat and water mass transfer inside a slope. Later using the generated pore water condition, slope stability analysis is conducted using SLOPE/W. After that, a transient seepage model was developed incorporating rainfall intrusion in the slope with the thawing process for the same duration. The model showed that slope stability increases with the decreasing pore water pressure during cold weather. The slope stability decreases from 1.7 to 1.2 during the thawing. This phenomenon is due to the absorption of heat followed by rapid rising in soil temperature. This research will be helpful for the decision makers as a guide for highway slope construction and act as an early warning tool in the snow melting period.