title: Evolution of shear zones in granular materials.
abstract: 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, such as sand, and elongated particles. Shearing an initially random sample, the zone width was found to significantly decrease in the first stage of the process. The characteristic shear 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 rodlike particles than for grains with smaller shape anisotropy (beads or irregular particles). The evolution of the zone width is connected to shear-induced packing 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.
authors.affiliation: Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
authors.forename: Balázs
authors.initials: B
authors.lastname: Szabó
authors.affiliation: Institute of Physics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary.
authors.forename: János
authors.initials: J
authors.lastname: Török
authors.affiliation: Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
authors.forename: Ellák
authors.initials: E
authors.lastname: Somfai
authors.affiliation: Otto-von-Guericke University, D-39106 Magdeburg, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Wegner
authors.affiliation: Otto-von-Guericke University, D-39106 Magdeburg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Stannarius
authors.affiliation: Otto-von-Guericke University, D-39106 Magdeburg, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Böse
authors.affiliation: Otto-von-Guericke University, D-39106 Magdeburg, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Rose
authors.affiliation: Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Angenstein
authors.affiliation: Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Börzsönyi
mesh_terms: D055595:Mechanical Phenomena; D008962:Models, Theoretical; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors