The mathematical model for porous elasto-plastic media saturated by an incompressible viscous liquid is presented. It is based on the concept of the a second-grade character of general heterogeneous media and on an incompressible binary model. The mixture of a liquid and solid is assumed to be governed by a single temperature function. The plastic part of the solid deformation gradients is treated as internal state variables. The above constitutive model can be utilized to describe ductile matrices as well as brittle and granular materials.