Abstract: The development of cracks is important to the damage and failure of soil. In order to study the evolution of meso-cracks in granite residual soil with complex geotechnical engineering properties, a series of reconstructed volume images was obtained by using CT to scan the process of the triaxial compression test. The crack volume overlap rate is introduced to improve the crack classification method proposed by the author, and the accuracy of judging the connectivity of the two cracks before and after deformation is improved. The results reveal that the change of crack volume overlap rate has a slight effect on the obsolete and brand-new cracks, while the greater sample deformation leads to the greater influence on other types of cracks, and the optimal crack volume overlap rate is 0.05. The volume content of obsolete and brand-new cracks increases with the increase of axial strain, and the volume content of brand-new cracks increases faster, while the volume content of compound cracks decreases, and the volume content of the other cracks is small. The change of fractal dimension of cracks is similar to that of volume content. Among them, obsolete, brand-new, and combined cracks show an increasing trend, and the fractal dimension of brand-new cracks increases the fastest, indicating that brand-new cracks can better reflect the shear failure process of samples. The results will provide theoretical and technical support for the fracture damage analysis of geomaterial.

Key words: classification of soil crack, CT, crack fractal, digital volume correlation