## 4 Results and Discussion  
In order to study the influence of different-sized elements' sliding friction coefficient on the numerical simulation results based on the experimental method [28], we applied the sliding friction coefficient algorithm to [PERSON]'s slope example [45]. To verify the correctness of the DEM model established according to [PERSON]'s FEM model [45], the sliding surfaces of the FEM model and the DEM model were calculated under the same  
Figure 5: DEM slope model generation: (**a**) generation of elements; (**b**) formation of slope. Figure 6: The DEM slope model. Figure 7: The measuring points. material parameters. The sliding surface corresponding to the minimum FOS (factor of safety) value is considered the most critical or dangerous sliding surface in FEM. The sliding surface generated by the calculation of the original DEM model is shown in Figure 8, which illustrates the displacement changes; the most dangerous sliding surface calculated by the FEM model is shown in Figure 9. By comparing these figures, it can be found that the sliding surfaces of the two models are the same, which verifies the correctness of the DEM model. To verify the applicability of embedding the experimental method-based sliding friction coefficient algorithm into the DEM slope model, we can compare each measuring point's horizontal and vertical displacements before and after the sliding friction coefficient algorithm was incorporated into the model (Table 4). This comparison shows that the sliding friction coefficient algorithm has an impact on the calculation of the DEM slope model. A comparative analysis of the two models will be described later. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Measuring Point** & **Original Model (mm)** & **Modified Model (mm)** \\ \hline Horizontal displacement of point 1 & \(-1.4\) & \(-2.7\) \\ Vertical displacement of point 1 & \(-3.7\) & \(-4.6\) \\ Horizontal displacement of point 2 & \(-0.1\) & \(-0.1\) \\ Vertical displacement of point 2 & \(-0.1\) & \(0.2\) \\ Horizontal displacement of point 3 & \(-3.0\) & \(-3.0\) \\ Vertical displacement of point 3 & \(-4.8\) & \(-5.4\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of displacement value of each measuring point. Figure 8: The sliding surface of the DEM model. Figure 9: The sliding surface of the FEM model. The FEM and DEM are commonly used for analysis in geotechnical engineering. These two analysis methods are based on different assumptions and theoretical backgrounds. The accuracy of the calculation results of the DEM model is related to factors such as contact discovery, element shape, time step, and spatial dimension. The slope model described in this paper is two-dimensional and composed of circular elements. The total number of elements is 8000, each with a particle size of 0.1-0.3 in the DEM model. Compared with the FEM model, the number of elements in the DEM, as well as the size of these elements, is enlarged to a certain extent. However, if the number of elements is increased, the calculation time will be greatly increased and the accuracy will remain the same, and sometimes the accuracy of stress and strain results will not be substantially improved. In addition, the modeling methods of the two simulations are very different, so the calculated displacement-time curves are slightly different. Therefore, in this paper, we only compare and analyze the change trend in each measuring point of the DEM models before and after adding the sliding friction coefficient algorithm. The positions of each measuring point are shown in Figure 7.  
The displacement-time curves of each measuring point from before and after embedding the sliding friction coefficient algorithm into the DEM model for the different-sized elements are drawn according to the position of each measuring point (Figure 7). The horizontal and vertical displacement of each measuring point is shown in Figures 10-15. Based on the diagram of each measuring point, the following conclusions can be drawn:  
1.