Study on mesoscopic structural evolution of aeolian loess driven by loading and water saturation using 3D micro-CT

Aeolian deposition and subsequent consolidation processes play a fundamental role in shaping the initial structure of loess. Loading and saturating directly determine the special properties of undisturbed loess, but the understanding of the differences in their effects on the loess structure remains limited. This study conducted consolidation and collapse tests, followed by CT scanning to analyze the microscopic evolution of the initial aeolian loess structure under the effects of water and force. The results show that the orientation angle of the long axis (PHI) of large soil particles tends to concentrate at 45° under loading, whereas the PHI of large particles generally tends to tilt horizontally under saturation. Both consolidation loading and water saturation increase the fraction of pores in the specimen that have a larger shape factor (SF), indicating an increase in irregular pores. Results also illustrate that variations in the rotational behavior of skeletal particles under loading and saturation significantly influence the final microstructure. In dry soil conditions, the sequence of first saturating and then loading generates new structural voids, resulting in a final void ratio that is higher than the case of loading followed by saturation. Finally, this study provides a microscopic explanation for the shift in loess consolidation behavior caused by variations in loading and water saturation. This research enhances the understanding of the evolution of powder under external action.