Behaviour Of Dry Sand Research Articles

FE-Simulations of a Direct Wall Shear Box Test

Paper deals with numerical simulations of a direct wall shear box test in conditions of plane strain. The behaviour of dry sand during shearing along a very rough wall is numerically modelled with a finite element method using a hypoplastic constitutive relation within a polar (Cosserat) continuum. The constitutive relation is obtained through extension by polar quantities, viz. rotations, curvatures and couple stresses, using the mean grain diameter as a characteristic length. It is characterised by simplicity and a very wide range of applications. The material constants can be found by means of standard element tests and simple index tests. They are correlated with grain properties. The FE-calculations investigate the influence of the initial void ratio, layer height and mean grain diameter on the shear resistance. The attention is laid on the effect of boundary conditions on the shear zone thickness. The FE-results are compared both with corresponding experimental results of laboratory model tests carried out with a parallel-guided direct shear box.

Patterns of shear zones in granular bodies within a polar hypoplastic continuum

The paper deals with numerical investigations on the patterning of shear zones in granular bodies. The behavior of dry sand during plane strain compression tests was numerically modelled with a finite element method using a hypoplastic constitutive relation within a polar (Cosserat) continuum. The constitutive relation was obtained through an extension of a non-polar one by polar quantities, viz. rotations, curvatures, couple stresses using the mean grain diameter as a characteristic length. This relation can reproduce the essential features of granular bodies during shear localisation. During FE-calculations, the attention was laid on the influence of boundary conditions and the distribution of imperfections in the granular specimen on the formation of patterns of shear zones.