Water retention behaviours of intact loess exposed to freeze-thaw cycles

Freeze-thaw acting is an important factor that can’t be ignored in engineering disasters such as loess slope slump and roadbed subsidence. Water retention behaviour is the key physical property for analyzing the hydraulic-mechanical properties of unsaturated loess, and it needs to be further studied that how freeze-thaw cycle affects water retention behaviours of loess. This test took intact loess after freeze-thaw cycles as research objects and studied how both the number of freeze-thaw cycles and the water content before freeze-thaw affect the soil-water retention curve (SWRC) and its characteristic parameters. The results show that the effect of freeze-thaw cycles on SWRC is fluctuating, and the degree of influence is controlled by the number of cycles and the initial water content before freeze-thaw. The relationship between saturation and ratio of suction (ratio between suction and air-entry value) can be normalized under different freeze-thaw conditions. By establishing quantitative relationship between the air-entry value and the structure index, a modified water-retention model was proposed to consider the effect of freeze-thaw cycles uniformly. The effect of freeze-thaw cycle conditions on the SWRC of intact loess is preliminarily confirmed, which can be reflected by the change of air-entry value caused by the change of soil structure index.