Discussion of "The asymmetry of stress in granular media": [J.P. Bardet and I. Vardoulakis, Int. J. Solids Struct. 2001, Vol. 38, No. 2, pp. 353–367]

The discussion concerns a recently proposed definition of average stress for granular materials, one which can manifest asymmetry in the absence of surface couples, body couples, and contact couples. The average stress was derived from a new postulate that employs virtual work terminology. The discussion shows that the postulate leads to a non-unique average stress and to a non-unique stress asymmetry.