Abstract: The independent application of slip line field theory in slope stability analysis has not been reported yet. On the basis of slip line field theory, we propose a limit curve method of assessing the stability of layered soil slope according to the slope deformation situation. This method is the inverse process for the ultimate load of heavy slope and the dual process of strength reduction method. Considering the intersection of slope surface curve under limit state and the original slope surface as failure criterion, we define two assessment indicators: Degree of Safety (DOS) and Degree of Failure (DOF). Then we extend the characteristic line equation of homogeneous soil to the layered soil condition, with the original equation as its special case, and soil interface as the special surface of discontinuity. On this basis, we obtained the condition and formula of slip line refraction in soil interface. Compared with traditional methods, this method needs not assume and search critical slip surface. Seven calculation examples verified the correctness of the deformation failure criterion. The stability evaluations of DOS/DOF with different theoretical methods are consistent, indicating this method is applicable to analyse the stability of layered soil slope.

Key words: layered soil slope, limit curve method, deformation failure criterion, equations of characteristic line for layered soil, slip line refraction