  Classical soil mechanics results are used to propose the equation of the
jamming transition surface in the (stress, specific volume) space. Taking
axis-ymmetric conditions, labelling q the deviatoric stress and p' the mean
pressure applied on the granular skeleton, and considering normal range of
pressure (10 kPa-10MPa) the equation of the surface of jamming transition is v
= vo-m ln(p'/p'o)+ md ln(1+q q/(M' M' p' p')); M' is related to the friction
angle, m and md are two constants which depend on soil characteristics; p'o is
a "unit" pressure.
