Abstract:In order to reveal effects of freeze-thaw cycles on shear strength of brown soil, the undisturbed brown soil from 5 cm and 25 cm depths (H5 and H25, respectively) in Shenyang area were collected. The effects of freeze-thaw cycles and soil water contents on soil shear strength were analyzed through indoor freeze-thaw simulation and direct shear tests in laboratory. The results showed that:(1) The higher soil water content, the stronger damage effect of the first freeze-thaw cycle. After the first freeze-thaw cycle, soil cohesion of H5 and H25 samples with 25% soil water content decreased by 50.00% and 25.87%, respectively; and the soil cohesion with 35% soil water content decreased by 75.61% and 50.77%, respectively. After 15 freeze-thaw cycles, the cohesion of H5 and H25 samples with 10% soil water content increased by 74.36% and 60.08%, respectively; the cohesion of H5 and H25 samples with 35% soil water content increased by 14.63% and 26.15%, respectively. However, the mechanisms of cohesion increasing under two different soil water contents were different. (2) The internal friction angle of H5 and H25 samples with 15%, 20%, and 25% soil water contents fluctuated during the multiple freeze-thaw cycles, indicating that the effects of freeze-thaw cycles on the internal friction angle were complicated and uncertain in the soil water contents. The internal friction of H5 and H25 samples with the soil water content of 35% were hardly affected by freeze-thaw cycles and varied between (18.57°±0.88°) and (12.86°±1.14°), respectively. (3) The average shear strength mainly decreased exponentially with the increasing of soil water contents. Clay content might play important role in average shear strength at different water contents. When the soil water contents were below 25%, the average shear strength of H25 soil samples were higher than that of H5; while soil water contents were above 25%, the average shear strength of H25 were lower.