Experimental investigation of shear band patterns in granular material

This paper presents three series of sandbox experiments of extensional deformation in granular material. The dependence of the developing shear band system on different boundary conditions and material properties is investigated: (1) granulometric properties of the material, (2) initial geometry of the specimen, and (3) dynamic material parameters. Particular attention is paid to the controlling of the basal boundary conditions. X-ray technique and particle image velocimetry (PIV) are used to study the changes in the granular structure and in the formation of shear band patterns. The results show that boundary conditions are an elaborate factor to explain differences in the shear band pattern. It is shown that neither the average grain size diameter d50 nor the rate of loading influences the shear band spacing. The spacing of the bands seems to be linearly dependent on the initial height of the specimen.