  It is recalled that stress-strain incremental modelling is a common feature
of most theoretical description of the mechanical behaviour of granular
material. An other commonly accepted characteristics of the mechanical
behaviour of granular material is the Rowe's relation which links the dilatancy
K to the ratio B of vertical-to-lateral stress during a test at constant
lateral stress, i.e. B =(1+M)(1+K). Using an incremental modelling, this law
shall be interpreted as a pseudo-Poisson coefficient. We combine these two
features to solve the problem of an axial compression under undrained
condition. We demonstrate that the sample is submitted to a bifurcation of the
transcritical type when it reaches the q=Mp line. This allows extending the
notion of the characteristic state introduced by Luong to other situations and
to anisotropic systems. We show also that these undrained tests are quite
appropriate to study the characteristic-state behaviour.
