Abstract: Analysis method of slope stability can be classified into local and global kinds. These different points have their historical rationality and limit. Taking limit equilibrium method and strength reduction method for examples, the difference of typical local and global one such as slip surface, equilibrium condition, definition of safety factor, material parameters and un-stability is studied and summarized. Using a PFC slope fail case presents that real slope un-stability has observably spatiotamporal series and progressive features. Practical slope failure is a process of terrain reconstruction and stabilization and a process of potential and kinetic energy transition and dissipation. Aiming at these, the theoretical framework and technical route of slope stability vector sum method considering generalized softening are established. The relative program is implemented too. Whose reduction has material degradation back-ground. Its safety factor only relates to stress state of the slope. There are few assumed conditions in the method, which can realize dialectical unity of local and global stability and reflects progressive characteristics and spatiotamporal effect of slope un-stability. The safety factor and slip surface obtained by the method proposed compared with results of LEM and SRM, show that slip surface of local one is more stable, safety factor is whole life cycle and is larger than that of global one by 5%. The difference between local and global slope stability analysis method is caused by their assumed conditions.

Key words: slope, local stability evaluation method, global stability evaluation method, slip surface, safety factor, generalized softening, vector sum method