The Microstructure Characteristics of Sliding-Zone Soil After Landslide Failure

The expansive soil shows adverse engineering properties when encountered water, thus analyzing the microstructure is significant to identify its failure mechanism. In order to study the microstructure of expansive soil, five undisturbed samples were obtained from Xinyan landslide zone in Yanbian, Jilin, China. Initially, large indoor experiments were done including physicochemical experiments and swelling tests. A scanning electron microscope was employed to investigate the microstructure. In addition, the quantitative analysis was conducted by WD-5 image processing system. Two specimens from each sample, representing the horizontal and vertical planes, were tested. In view of the difficulty of describing the exact complexity of particle morphology, box counting dimension was extracted to represent the feature of particle structure. The results show that montmorillonite and illite mixed layer content is 59.8% in the soils; soil with a complex microstructure has a large expansion force; the cation exchange capacity can reflect the expansion property; and the porosity is negatively correlated with the structural parameters (circularity and average shape coefficient of structure element included). Research on the microstructure provides a theoretical basis for further understanding the stress-strain process in expansive soil.