# Prediction of the Dangerous Range of Dumps Based on a Dynamic Process
## 6 Discussion  
The numerical simulation method shows potential that cannot be ignored in the risk assessment of abandoned slag slopes.  
The research on the stability evaluation of waste slag slopes is mainly studied from both qualitative and quantitative aspects. The qualitative methods mainly include the natural history analysis method and the engineering geological analogy method. The results are subjective and empirical. The quantitative methods include the physical model test method, field monitoring, and numerical simulation method. Among them, the physical model test method is limited by various factors, and it is difficult to make the physical model and the real model fully meet the similarity, which has great limitations in use. On-site monitoring is required to clarify the main sliding direction and landslide mode of the deformation zone through displacement monitoring data and to analyze the changes in the seepage field of the dump from the inside to understand the internal factors that cause the landslide of the dump. However, due to the limited operability of the monitoring range, the cost is high, and the data accuracy is low and limited.  
The numerical simulation method can effectively avoid the size effect of the model and simulate complex geological problems. It is more practical than the traditional laboratory or expensive, time-consuming, and even dangerous test methods. The influence of topography on landslides is very complex. The numerical simulation method has the advantage of considering the influence of actual terrain.  
By simulating the instability process of the spoil slope, the 3D-MPM and 3D-SPH methods were compared.  
Traditional Euler grid algorithms, such as the finite element method (FEM), are limited by the grid distortion and are more suitable for solving small deformation problems. The finite difference and finite volume methods based on depth averaging can better reflect the control effect of the actual terrain and have higher computational efficiency. However, these methods are essentially two-dimensional methods, which mainly focus on the base friction and need to preset the sliding surface, which is not conducive to the solution of the instability process of the spoil slope.  
In this context, some meshless numerical methods, such as the smoothed particle hydrodynamics method and material point method, are applied to the calculation of the slope dynamic process. In this study, these two methods were used to reflect the similar instability movement process of the spoil slope. From the point of view of the instability process and the final movement distance, the results are similar. Under ordinary working conditions (static and dry conditions), the dump is in a stable state, and only local shallow surface damage or shallow surface damage occurs at some steps. Under the condition of heavy rainfall, it is assumed that the waste is close to saturation, the fluidity is strong, the movement is triggered due to excessive water content, and a large-scale instability failure occurs. The disadvantage is that there is no earthquake condition involved in this  
Figure 16: The plane displacement: (**a**) the original spatial position and (**b**) the final dangerous area.  
paper. Although there has been no earthquake above 7 magnitude in the project area and its vicinity, the probability of a super strong earthquake is very low, but this possibility cannot be completely ruled out. Two cases can be considered, only seismic load, and seismic load and extreme rainfall conditions. This is a problem that needs to be further discussed in the future. Through the two methods of MPM and SPH, the maximum horizontal displacements of the waste were 352.4 m and 394 m, respectively. The two methods verified each other and increased the reliability of the simulation.