Numerical Studies of Shear Banding in Interface Shear Tests using a New Strain Calculation Method

Strain localization is closely associated with the stress-strain behavior of an interphase system subject to quasi-static direct interface shear, especially after peak state is reached. This behavior is important because it is closely related to deformations experienced by geotechnical composite structures. This paper presents a study using two dimensional DEM simulations on the strain localization of an idealized interphase system composed of densely-packed spherical particles in contact with rough manufactured surfaces. The manufactured surface is made up of regular or irregular triangular asperities with varying slopes. A new simple method of strain calculation is used in this study to generate strain field inside a simulated direct interface shear box. This method accounts for particle rotation and captures strain localization features at high resolution. Results show that strain localization begins with the onset of nonlinear stress-strain behavior. A distinct but discontinuous shear band emerges above the surface around peak state, which becomes more expansive and coherent with post peak strain softening. It is found that the shear bands developed by surfaces with smaller roughness are much thinner than those developed by surfaces with greater roughness. The maximum thickness of the intense shear zone is observed to be about 8 to10 median particle diameters above the surface. Theoretical orientations of shear bands are also presented, with Roscoe solution making the best predictions for the major shear band which is aligned with the direction of boundary movement.