Variations in strength and deformation of compacted loess exposed to wetting-drying and freeze-thaw cycles

Abstract

Densely compacted loess on which many man-made infrastructures are built are often exposed to strong weathering processes such as repeated wetting-drying (WD) and freeze-thaw (FT) cycles. These weathering processes in arid and seasonally frozen ground regions result in loose structure and strength deterioration of loess soils, and they cause serious engineering problems and expensive maintenance costs of infrastructures built on densely compacted loess. In this study, specimens of densely compacted loess were exposed to different intensities of weathering processes under controlled laboratory environment to quantitatively assess their deterioration effects on geotechnical properties. According to the laboratory results, the wetting-drying weathering has a stronger impact on the geotechnical properties of densely compacted loess than the freezing-thawing weathering. The unconfined compressive strength, elastic modulus, and cohesion of the loess specimens decrease with increasing number of WD and FT cycles while the vertical compression strain and collapse deformation increase. The densely compacted and non-collapsible loess specimens exhibited collapsible again (secondary collapse) after 5 WD cycles. The deterioration mechanisms of densely compacted loess induced by wetting-drying and freezing-thawing weathering processes have been presented and were strongly recommended to be taken into account for the prediction of long-term stability and serviceability of man-made infrastructures built on densely compacted loess.