Fracturing Behavior of Fine-Grained Soil Mixtures under Uniaxial Compression Studied Using X-Ray Microtomography

The micromechanical behavior of two fine-grained soil mixtures, i.e., RS-C containing river sand grains and GB-C containing glass beads, was investigated using X-ray microtomography (µCT). The specimens were uniaxially compressed within a miniature loading apparatus with in situ X-ray µCT scanning, from which full-field high spatial-resolution CT images of the specimens were acquired for analysis. Both specimens experienced an initial increase of axial stress accompanied by the generation of small-sized isolated cracks and a subsequent decrease of axial stress associated with the gradual formation of a major inclined crack as the loading progressed. The crack connectivity for both specimens exhibited a gradual reduction, followed by an increase. The generated isolated cracks displayed a higher likelihood of orienting along the vertical direction rather than the horizontal direction. This was found to be associated with the lateral dilation of the specimens during the early loading stage. Both specimens displayed a significant increase in crack volume, correlating exponentially with axial strain. RS-C demonstrated higher initial stiffness and peak strength, attributed to a superior interlocking effect at the fine–coarse grain interface compared to GB-C.