Measurements of the failure properties of granular materials and cohesive powders

A direct shear tester equipped with a press loading system has been employed to measure the failure properties of granular materials and cohesive powders. An advantage of this tester is that a yield locus for such materials can be obtained from one shear test by a continuous line.The yield locus for granular materials has been directly drawn as a straight line on an X-Y recorder chart having the normal stress as the abscissa and the shear stress as the ordinate.Yield loci for cohesive powders have also been drawn as convex curves on the recorder chart, having reduced shear and reduced normal stress axes. They are therefore reduced yield loci.The shapes of the loci obtained for a range of initial consolidation stresses of 10 to 350 g/cm² are satisfactorily described by the Warren Spring equation. When this equation is rewritten with reduced stresses, it can be expressed in terms of three dimensionless parameters. The values of these parameters, which are determined from the measured loci, seem to depend on the bulk density of the sample.