Comparing the Flow Properties of Bulk Solids by Tri-axial Shear Tests, Unconfined Yield Tests and Direct Shear Tests

In order to examine the confidence in experimental results of the flow properties of a bulk solid, this paper discusses a comparison of the experimental data obtained by using different shear tests methods. The angle of internal friction of dry granular materials, which has been measured by both the tri-axial shear tester and the fixed volume direct shear tester, increases with a decrease in the voidage of the specimen. Except for the extremely dense and loosely packed states, the experimental results of the angle of internal friction agree within about 3 degrees. For a material in which the particle shape is deflective, there is however a difference of 3 to 5 degrees. The flowability index for cohesive powders and wet materials is expressed by a ratio of the unconfined yield strength to the bulk density. The experimental results of the flowability index are independent of the two methods of the unconfined yield test and the direct shear test.