Localization in elastic-plastic saturated porous media is investigated here
using a linear perturbation approach. The adopted localization criterion c
orresponds to unbounded growth of perturbations. The critical conditions ar
e compared with those obtained by a classical band analysis. While for one
phase materials these conditions coincide, in the present context the linea
r perturbation approach leads in the limit of unbounded growth to the singu
larity of the undrained acoustic tensor, while the band analysis leads to t
he singularity of the drained acoustic tensor. Some general results clarify
ing the hierarchy of these two conditions are established for a guile gener
al set of constitutive equations. (C) 2000 Academie des sciences/Editions s
cientifiques et medicales Elsevier SAS.