Quantifying localized deformation in Malan loess under shearing using X-ray micro-CT

Loess tends to exhibit localized deformation in narrower bands when the material is subjected to shear stress exceeding its strength. This deformation is often a precursor to larger-scale failure, as it can significantly reduce the bearing capacity of the material. Quantifying localized deformation in loess could provide valuable insights for risk forecasting and assessment in loess regions. This study aims to characterize localized deformation in loess under triaxial loading by tracking the movement of internal high-density minerals using X-ray micro-computed tomography (micro-CT). High-resolution scans were performed to capture detailed images of a Malan loess sample before and after the triaxial test, enabling tracking of the motions of high-density minerals within the sample and measuring internal displacement fields with good precision. The displacement fields depicted the statistical and spatial distributions of localization areas within the sample, which were well correlated with observed physical changes (shear fracture formation) in the post-failure tomographic slices. The sample examined failed in a clearly localized shear mode with an obliquely distributed main shear band, and displacement profile measurements show that the main shear band thickness slightly varied across the sample. Smaller-scale localization occurring in other areas was also captured as a record of complex strain history. The application of micro-CT and tracking high-density minerals within Malan loess has proven to be an effective technique for visualizing internal deformations and linking microstructure changes with the macroscopic behaviour of materials.