Ali Johari - Assistant Professor, Department of Civil and Environmental Engineering, Shiraz University of Technology, Shiraz, Iran
Masoud Sahebkar - Ms Candidate of Geotechnical Engineering, Department of Civil and Environmental Engineering, Shiraz University of Technology, Shiraz, Iran

The use of limit equilibrium methods are the common approaches for determining of soil slope stability ingeotechnical engineering project. In these methods many researchers tend to find a circular criticalfailure surface for homogeneous soils, but failure surfaces can be non-circular especially for layeredslopes. Finding of critical failure surface of a general soil slope is a difficult problem as the non-convexand multiple minima exist of the safety factor objective function. In this paper simple genetic algorithmand particle swarm optimization methods are employed to find the critical non-circular failure surface.For this purpose the Morgenstern–Price method is used to find the factor of safety. A computer programwas coded by MATLAB for searching the minimum factor of safety. The result of a example is comparedwith stress-deformation method using PLAXIS software for one example. It shows the determined safetyfactors are very close to each other for two methods

Critical failure surface, Factor of safety, Slope stability, Particle swarm optimization, Genetic algorithm