The correlation of macro deformation and micro kinematics for dense granular material subjected to shearing

In the study, biaxial shearing tests were carried out through the numerical simulations based on the discrete element method to examine the correlation of macro deformation and micro kinematics characterization in contact scale. The contact motions were decomposed into three independent types, i.e., contact deformation, contact rolling and rigid-body motion. The simulated dense sample can qualitatively reproduce the experimental outcomes for the stress–strain and volumetric relationship. From the micro to macro scale, it is found that the particle nonaffine displacement and particle rotation have strong spatial correlations with development of the shear band and the different contact motions have different influences on the sample deformation. That is, the contact deformation dominates the whole sample deformation, while the contact rolling and the rigid-body rotation have relatively small contributions to the volume change during the whole shearing process. The external loading is mostly supported by the strong contact forces in the sample, but the dilation deformation is more obvious in the weak contact force network. In strong contact force network, the contact deformation mainly induces contraction for the sample; the rigid-body rotation and contact rolling also contribute to contraction slightly; hence, the overall deformation in the strong contact force network is contraction. In the weak contact force network, the contact deformation creates dilation; the contact rolling has a small contribution to contraction, and the rigid-body rotation has no contribution to the volume change; thus, the overall dilation for the sample in the weak contact force network is observed. © 2021 Elsevier Ltd