Shearing of a narrow granular layer with polar quantities

The paper deals with numerical investigations of the behaviour of granular bodies during shearing. Shearing of a narrow layer of sand between two very rough boundaries under constant vertical pressure is numerically modelled with a finite element method using a hypoplastic constitutive relation with in a polar (Cosserat) continuum. The constitutive relation was obtained thr ough an extension of a non-polar one by polar quantities, viz. rotations, c urvatures, couple stresses using the mean grain diameter as a characteristi c length. This relation can reproduce the essential features of granular bo dies during shear localization. The material constants can be easily determ ined from element test results and can be estimated from granulometric prop erties. The attention is laid on the influence of the initial void ratio, p ressure level, mean grain diameter and grain roughness on the thickness of shear zones. The results of shearing are also compared to solutions without the polar extensions. The FE-calculations demonstrate that polar effects m anifested by the appearance of grain rotations and couple stresses are sign ificant in the shear zone, and its thickness is sensitive to the initial vo id ratio, mean grain diameter and layer height. The effect of the pressure level is rather low within the considered range. Copyright (C) 2001 John Wh ey & Sons, Ltd.