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Evolution of shear zones in granular materials B. Szabo1*, J. Torok2, E. Somfai1, S. Wegner3, R. Stannarius3 and T. Borzsonyi1 (1) Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary (2) Institute of Physics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary (3) Otto-von-Guericke-University, D-39106 Magdeburg, Germany * Corresponding author: [email protected] The evolution of wide shear zones (or shear bands) was investigated experimentally and numerically for quasistatic dry granular flows in split bottom shear cells. We compare the behavior of materials consisting of beads, irregular grains (e.g. sand) and elongated particles. Shearing an initially random sample, the zone width was found to significantly decrease in the first stage of the process (see the figure below). The characteristic strain associated with this decrease is about unity and it is systematically increasing with shape anisotropy, i.e. when the grain shape changes from spherical to irregular (e.g. sand) and becomes elongated (pegs). The strongly decreasing tendency of the zone width is followed by a slight increase which is more pronounced for rod like particles than for grains with smaller shape anisotropy (spheres or irregular particles). The evolution of the zone width is connected to shear induced density change and for nonspherical particles it also involves grain reorientation effects. The final zone width is significantly smaller for irregular grains than for spherical beads. The width of the shear zone as a function of strain, normalized by the width in the stationary state.
