Study on the mesostructural evolution mechanism of compacted loess subjected to various weathering actions

摘要

Strong weathering can lead to a weakening of soil structure; such an effect will have a considerable impact on the long-term stability of compacted loess foundations or subgrade engineering. This study used a computed tomography (CT) technique to track the evolution of compacted loess under wetting-drying (WD) cycling, freezing-thawing (FT) cycling and coupled cycling. The evolution of the mesostructure of compacted Lanzhou loess under the different types of weathering processes was studied by analyzing density distribution curves of CT images. Based on the CT results, the damage increment and the structural potentials of the WD, FT and coupled cycles were used to quantitatively describe the changes in the mesostructure of the compacted soil. In addition, the evolution behavior of the mesostructure and the mechanisms responsible for changes in the pore structures were quantitatively assessed under the actions of the different types and numbers of cycles. The results provided the order of the resultant degree of soil damage from these weathering processes, from high to low: coupled cycling, WD cycling, and FT cycling. The rate of deterioration of the soil structure due to the WD cycles and FT cycles peaked after 3 cycles and then decreased slowly; however, under the coupled cycling, the soil structure continued to deteriorate, resulting in significant deterioration.