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Abstract The present contribution is concerned with theoretical and numerical issues in finite element slope stability analysis. In the theoretical part，instability phenomena of slope material are studied within the framework of bifurcation theory. It is proved that strain localization not only is a ubiquitous feature of elastoplastic geomaterials，but also is the unique instability mode of the elastic-perfectly plastic material with an associative flow rule under plane strain and plane stress conditions. The shear band coalescence criterion is proposed，which argues that slope failure occurs when smaller size shear bands coalesce into a dominant shear band which completely divides the slope into two parts. In the numerical implementation part，a strategy for tracking the localization band path is presented. By tracking the initiation，growth and coalescence of localization zones in terms of the localized state of all soil elements at each time step，the limit equilibrium state can be directly judged；and the critical slip surface can be simultaneously determined. Finally，the feasibility and reliability of the proposed criterion are validated by strength reduction and over-loading examples.
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2012, Vol. 31 
