The effects of freeze-thaw cycles at different initial soil water contents on soil erodibility in Chinese Mollisol region

摘要

Freeze-thaw action is a common natural phenomenon in cold regions, which affects soil erodibility by changing soil structure and mechanical properties. However, quantifying the impacts of freeze-thaw cycles (FTCs) at different initial soil water contents (ISWCs) on soil erodibility is challenging due to the complex interactive soil mechanical responses. In this study, direct shear strength and soil disintegration tests were conducted to quantify soil erodibility indices. Seven FTCs (0, 1, 3, 5, 7, 10 and 13) and three ISWCs (16.5, 24.8 and 33.0%) were employed to investigate soil shear behavior and disintegration properties for two Mollisol soils. Results showed that repeated FTCs had cumulative impacts on soil mechanical properties, and the 10th FTCs might be the threshold number for influencing soil erodibility. The soil shear strengths decreased by 1.1-15.1% and 9.2-30.5% under four normal stresses at the first and 13th FTCs, respectively, for these two soils. Soil cohesion generally decreased with the increase of FTCs. Soil internal friction angle showed no trend with FTCs at the 16.5% and 24.8% water contents but a decreasing trend at the 33.0% water content. Soil disintegration rate increased with FTC and reached a maximum value at the 10th cycle but decreased with the increase of ISWC. Soil disintegration of the two Mollisols showed a sharp disintegration of about 60% in 133 s. This study provides a new understanding of the response of erodibility to freeze-thaw conditions for two Mollisols.