*7.1. Sensitivity Analysis*

The DAN-W dynamic model was preferably used to predict the dynamic characteristics of the landslide accumulation area in the Loess Plateau. However, based on a field survey and laboratory tests, some parameters, e.g., the friction coefficient, were obtained by trial and error and the existing research results [23,49–51]. There are many factors affecting the friction coefficient, including the rate of water content, terrain, and ground temperature, with the water content the primary factor. Therefore, it is difficult to provide the friction coefficient in a more efficient way. When using the DAN-W dynamic model to predict the risk assessment, the variability range of the parameters should be considered. In this paper, the influence of friction on the landslide is simulated using multiple sets of working conditions. According to the numerical values recommended by the kinematic model software and existing research results, the friction coefficient is divided into three groups. The first group has a low friction coefficient (i.e., 0.05, 0.1, and 0.2) which means high water content, the second group a moderate friction coefficient (i.e., 0.2, 0.3, and 0.4) which means moderate water content, and the third group a high friction coefficient (i.e., 0.5, 0.55, and 0.6) which means low water content. The calculation results are as follows (Figure 10).

**Figure 10.** Variation trend of the moving speed versus the sliding rage of the sliding body under the action of different friction coefficients.

According to the numerical simulation results, it can be seen from Figure 10 that, if different friction coefficients are selected, the calculated moving distances are significantly different. For example, when a low friction coefficient (0.05–0.2) is selected, the moving distance of the sliding body is 350–375 m. When the moderate friction coefficient (0.2–0.4) is selected, the moving distance of the sliding body is 320–350 m. When the high friction coefficient (0.4–0.6) is selected, the moving distance of the sliding body is 280–300 m. According to the current geological survey in the field and the aerial view of the drone, the moving distance of the landslide reached a maximum of 366–375 m, which is in line with the calculation results based on the low friction coefficient. The low friction coefficient appears to be due to the saturation degree of its material, and there was sufficient groundwater in the slope area that promoted the sliding of the landslide.
