To analyze the formation and evolution mechanism of shear bands and clarify the macroscopic and microscopic relationship of the interface parameters of the soil in the pull test

by employing particle flow code (PFC 2D)

geogrid-reinforced glass sand numerical pull-out tests were conducted on the basis of discrete element numerical simulation

whose results were compared with those of laboratory tests. In the numerical test

the nonlinear stress-strain relationship of the geogrid was reconstructed by using the piecewise function. According to the sand particle displacement

the average thickness of shear bands was determined. Factors such as contact force chain

particle displacement

and particle rotation as well as relations between the major principal stress direction and parameters of fabric anisotropy were analyzed. Results show that DEM could better analyze the mechanical behavior between the interface of the glass sand particles and the geogrid under small geogrid displacement

and volume dilatancy of the sample was mainly controlled by the motion of particles in shear zone. The program for Particle Rotation Color Displaying

developed by FISH language

showed that particles in the upper and lower interfaces of geogrid had different rotation modes and displacement and rotation of the particles formed shear zone with serrated distribution

which revealed that particle displacement and rotation were important characteristics of the evolution of shear band. The distribution of contact force and the evolution of fabric anisotropic determined the macroscopic mechanical properties and the basic shape of the shear band. During the shearing

the deflection of the direction of the major principal stress was similar to the orientation of contact force anisotropy in the shear band.