A new method for direct shear tests was devised to measure easily the flow properties of a powder and a granular material. This method is based on the stress resulted from expansion in volume of the specimen during a shear test.
Expansion is caused by the movements of each particle in shearing zone. Such a stress increses with increased shear strain while expansion occurs. A yield locus is therefore obtained from a single shear test recording simultaneously the normal and the shear components of the stress by a X-Y recorder.
The yield locus of the granular material is a straight line through the origin. The slope of this line, that is, the apparent coefficient of internal friction is depend on the height of the specimen. Therefore the true coefficient of internal friction is determined by extrapolating the height of the specimen toward zero. Furthermore, the cohesion and the unconfined yield strength of the powder are determined very easily from a single shear test in the region of low stress. The reproducibility of the results in the present method is satisfactory.