Abstract: Shear band and crack evolution are very important for landslides. Crack is the weakest area in soil, and there is a lack of effective methods to analyze the meso-structure damage in shear bands quantitatively. To reveal the influence of cracks in granite residual soil on shear deformation and failure, CT scanning was used to obtain volume images of the sample at different loading stages during triaxial loading. Based on the digital volume correlation (DVC) method, a crack classification method is established according to the connectivity characteristics of cracks before and after loading. The cracks can be divided into eight kinds: obsolete, brand-new, isolated, split, combined, compound-brand-new, compound-isolated, and compound-mixed cracks. The results show that the brand-new cracks and compound-type cracks are closely related to the shear band evolution. With the increase of axial strain, the brand-new cracks and compound-brand-new cracks are in an increasing trend. When axial strain is 12%, the volume content of the brand-new cracks is more than 50%, the compound-isolated cracks exhibit rapid attenuation, and the compound-mixed cracks tend to increase first and then decrease. At the early stage of shear band initiation, a few new cracks are formed in the shear band, which accelerates the development of the shear band as the cracks are the weakest area. With the development of the shear band, a large number of new cracks cause more serious damage to the meso-structure in the shear band. Finally, the coupling effect of shear bands and cracks destroys the soil strength.

Key words: granite residual soil, CT, shear band, crack classification, damage