In this paper, we propose a mechanical model for calculating the failure along the sliding surface based on the kinematic method of rigid solids (Limit analysis).
The statistical-probabilistic concept of safety is a very useful tool for comparison because it reflects the dispersion of random parameters (geometry, intrinsic characteristics of the soil load, etc. ...) will be applied to this model, the reliability of the system will expressed using the reliability index.
The introduction of the concept of reliability index Geotechnical is a valuable tool capable of giving the engineer a greater objectivity in the design of slopes.
We determine the critical slopes and the corresponding costs from the state equation R-S = 0 limit of the present mechanism. Finally recommendations will be given for modeling the failure along the sliding surface .