The mechanical behavior of soft rocks is quite complex as it may involve a variety of deformation mechanisms. When loaded under compressive stresses at intermediate temperature, such rocks often show a semi-brittle response controlled by dislocations motion and microcracking. Because these two types of physical processes are acting simultaneously, the constitutive equations should involve a coupled approach. In this paper, the authors extend an existing unified model with internal state variables, developed for the ductile regime, to accommodate semi-brittle behavior of low porosity rocks. To do so, a damage variable Dv is introduced into the model. This requires a modification of the kinetic law and the addition of an evolution law for Dv . After presenting some of the main features of soft rocks behavior, the main equations are introduced together with a few attributes of this new model.