Volume change behavior of compacted loess under drying/wetting and freezing/thawing cycles

Abstract

The long-term drying/wetting (D/W) and freezing/thawing (F/T) cycles damage the structure of the roadbed soil in loess areas, leading to a series of engineering geological disasters, such as roadbed collapse and cracking. In this study, a series of field monitoring was carried out on the Jihe Expressway, which was built on the Loess Plateau in China. It shows that drying/wetting (D/W) and freezing/thawing (F/T) cycles are important factors leading to periodic settlement and heave of loess roadbeds. A new temperature-controlled unsaturated soil triaxial apparatus was developed to explore the deformation mechanism of compacted loess under D/W and F/T cycles. The results of laboratory tests indicate that, in the isotropic stress state, both D/W and F/T cycles can reduce the void ratio and increase the volume deformation of compacted loess. In the D/W cycle, the soil samples show the collapse behavior, but the deformation of heavily over-consolidated samples is relatively less compared with lightly over-consolidated samples. On the other hand, repeated F/T cycles lead to fluctuating changes in the volume of compacted loess. Increasing the dry density can effectively reduce the deformation caused by F/T cycles. Moreover, the combination of the D/W and F/T cycles may further enhance the volume changes of the compacted loess. As the number of D/W and F/T cycles increases, the compressibility and irrecoverable deformation of the compacted loess increases, leading to a deterioration of its engineering properties.