<p>Tailings lenticles structures commonly arise in upstream tailings dams due to hydraulic deposition processes, and their layered anisotropy poses significant challenges to long-term dam stability. In particular, the deformation and failure behavior of such layered soil composites is closely associated with strain localization phenomena. This study presents a comprehensive experimental investigation into the mechanical behavior of tailings specimens incorporating fine-grained interlayers with varying dip angles. A digital image processing technique triaxial testing system was employed to capture whole-field strain evolution and deformation modes throughout the loading process. The results reveal that the presence and orientation of the interlayer significantly reduce the overall shear strength of the composite when compared to homogeneous silty sand specimens. Two distinct deformation patterns were observed: specimens with shallow-dip interlayers exhibited bulging (drum-shaped) deformation, while those with steeply inclined interlayers developed well-defined shear bands. For interlayer angles approaching 60°, failure was governed primarily by slip along the weak interface, with localization initiating at a discrete point and progressively propagating through the entire interlayer zone. This transition in failure mechanism reflects the critical influence of interlayer inclination on strength degradation and strain evolution. The findings of this study provide new insights into the progressive failure behavior of anisotropic tailings materials and highlight the necessity of incorporating interlayer geometry into the stability assessment and design of tailings dams and other layered geotechnical systems.</p>