Model Test Study on Stability Factors of Expansive Soil Slopes with Different Initial Slope Ratios under Freeze-Thaw Conditions

Abstract

Expansive soil is widely distributed in seasonally frozen areas worldwide. Due to the special expansion and shrinkage characteristics of expansive soil related to water content, there are potential engineering disasters in the subgrade and slope engineering. To investigate the physical and mechanical changes within the expansive soil slope, four freeze-thaw cycles tests were performed on expansive soil slope models in an environmental chamber with slope ratios 1:1.5, 1:1 and 1:0.5. Nuclear magnetic resonance (NMR) technology is used to explain the pore changes in expansive soil during freezing and thawing. Model tests were carried out to monitor the changes in cracks, moisture content, temperature, displacement and soil pressure of the slope model. The results show an increase in the slope ratio may give rise to more intense temperature changes, promote the development of cracks in the model, and increase the temperature gradient and moisture migration rate during freezing and thawing. Following freeze-thaw cycling, the soil structure is destroyed and reassembled, and the soil pressure decreases as the slope ratio increases. Combined with the displacement of slope model and NMR test results, the slope can maintain a stable state after multiple freezing–thawing cycles under a specific moisture content ωs.