## 5 Discussion  
Under the principle of the minimum safety factor, a pseudo-dynamic method for evaluating bedding slope stability is proposed in this study. Although this approach is relatively simple and efficient compared with the pseudo-static approach and finite element technique, it also has some underlying problems worth discussing.  
It is widely known that the structural plane of the bedding slope may be a potential slip surface, but this type of slope usually contains a group of structural planes. In a rigid body mechanics framework, the uniqueness of the slip surface can be determined by the principle of the minimum safety factor based on the limit equilibrium theory. However, the slip block and structural plane is an interaction relationship, and such interaction or mutual influence is going on in a synergetic and coupled manner considering that the slope is a deformable body during the dynamic action. In light of this, multi-slip surface failure may occur in bedding slopes under seismic load, and the pseudo-dynamic method in existence cannot yet be used to solve this question perfectly. [PERSON] et al. developed an extended Newmark sliding block model to investigate multi-slip seismic displacements of bedding rock slopes, and this method is considered as a supplement for the pseudo-dynamic method [2]. Therefore, the combined finite element technique with the pseudo-dynamic model should be developed and employed to analyze the seismic response and failure mode of bedding slopes, which will be key points for further research.  
Moreover, the basis for determining the safety factor still needs to be carefully explored. Seed opened that a slope may also be stable even if the safety factor is less than 1, if the slope only produces a certain amount of cumulative displacement and deformation, which is not enough to cause slope failure [36]. The permanent displacement is another crucial parameter for seismic slope stability, but better links with the safety factor need to be built. Several researchers who have attempted to correlate the safety factor with displacement to overcome the shortcomings of the traditional limit equilibrium theory have not advanced very far and the results also need to be subjected to practical testing. [PERSON] et al. and [PERSON] et al. established a relationship between the safety factor and displacement based on the soil shear constitutive model and Morgenstern-Price assumption of interslice forces, and this has provided a foundation for the combination of the two evaluation parameters of slope  
Figure 15: Transient safety factor for different methods.  
stability [37; 38]. Compared with the traditional safety method, the significant advantage of this technique is that it considers the influence of permanent displacement. In this study, the results of the pseudo-dynamic method show that the minimum safety factor converges to the result of the pseudo-static approach without considering the effect of the rock mass amplification factor, which may amplify the risk of slope instability. In order to better explain failure and assess the mechanisms of a slope, combining the safety factor and permanent displacement to evaluate the seismic stability of the slope will be a great point of exploration. The pseudo-dynamic approach is an effective analytic method offering a theoretical basis and feasible measurement for a dual-parameter stability evaluation.