Investigating the evolution of shear zones through ring shear tests on quartz sand
The macroscopic mechanical properties of landslides are often influenced by the microstructure of the shear zone.Therefore,it is important to study the microstructural evolution of the shear zone to better understand the nature and occurrence of landslides.In this study,we simulated the formation and evolution of shear zones by using the ring shear test on coarse quartz sand.We used X-ray computed tomography scanning and image analysis to quantitatively analyze the internal structural characteristics of the shear zone.The results showed that with increasing shear displacement,particle fragmentation led to a gradual increase in the number of fine particles within the shear zone.A three-layer structure was observed after shearing:upper and lower layers,and a core layer.The upper and lower layers had fewer fine particles than the core layer,which had a high concentration of them.After a shear displacement of 25 m,the accumulation of fine particles led to the formation of fine particle layers along the boundaries of the core layer.Furthermore,there was an increasing ratio of fine particles in the core layer and a corresponding enhancement in particle roundness when approaching the boundary.When the shear displacement was 100 m,shear surfaces were observed within the fine particle layers,indicating that the shear behavior of the particles of quartz sand was primarily concentrated on these surfaces.These findings had significant implications for our understanding of the formation and internal structural evolution of shear zones.