Experimental and Numerical Study on the Frost-Heaving Characteristics of Subgrade Soil in the Qinghai-Tibet Plateau

Regarding the serious problem of subgrade frost-heaving in season-frozen soil highway engineering in the Qinghai-Tibet Plateau (QTP) region, this paper studied the frost-heaving characteristics (FHC) of subgrade soil with different initial water content (IWC) and fine particle content (FPC) under unidirectional freezing (UDF) and surrounding freezing (SDF) conditions through laboratory tests, and further based on thermo-hydro-mechanical (THM) coupling effect, the variation characteristics of temperature, moisture and stress fields in the subgrade soil were analyzed by numerical method, aiming to provide a reference for the research of prevention and control measures of subgrade frost-heaving. The results show that the frost-heaving deformation (FHD) of subgrade soil can be divided into four stages, and its frost-heaving deformation rate (FHDR) is generally positively correlated with the IWC and FPC, while the freezing condition affects the significance of IWC and FPC on the FHDR. In the gradation design of subgrade soil, the IWC and FPC should be controlled at about 8% and 9% respectively. Compared to the SDF condition, the temperature distribution gradient in the subgrade soil under the UDF condition is significant and there is an obvious freezing front, but there are stress concentration points in the subgrade soil under both freezing conditions.