Slope collapse and the slide body come into moving state from stable static state simultaneously

and are accompanied by a dramatic increase in displacement of slide body. Furthermore

the displacement is not a definite value

but an infinite increase. This is the definition of overall collapse of a slope. In finite element model

the slope reaches instability with the strength reduction

value of the nodal displacement just after slope failure has a sudden change compared to the one before failure. This actually means that no stress distribution can be achieved to satisfy both the yield criterion and global equilibrium. Slope failure and numerical non-convergence take place at the same time. An element stress reaching the yield criterion state not always means that infinite “plastic flow” occurred. It is determined by boundary condition. The plastic zone developed from slope toe to top not means the overall collapse occurred. On the other hand

the distribution of plastic zone was influenced by many factors such as Poisson's ratio

flow rule

etc. So non-convergence in finite element program can be taken as a suitable evaluating criterion of slope failure. Through a series of case studies

the applicability of the proposed method was clearly exhibited.