In practice the state of equilibrium of a slope is in general calculated by means of Limit Equilibrium Methods. However, varying stress states, hydraulic conditions and failure mechanisms along a potential shear zone affect the development of shear stress during slope movement. For stiff soil e.g. while shearing a decrease of the shear strength after having reached a peak value can be observed. Due to the named effects, the mobilization of shear strength in the shear zone is not homogeneous and slope stability can be underestimated. The contribution presents an algorithm which couples the evolution of mobilized shear stress with shear displacement or shear strain, respectively, in the shear zone when slope movement is assumed. To illustrate the proposed algorithm a slope with a rigid body failure mechanism on a planar slip surface is considered. For the assumed slope model slope stability is calculated considering soil with and without softening behavior.