## 5 Discussion  
It is worth pointing out that in Figure 9a,b, the displacement development of the landslide is very slow, and the deformation is small, which is consistent with the field (Figure 8). Because the integrity of the landslide rock mass is gradually destroyed. However, this motion characteristic is difficult to achieve with depth-averaged models that are based on fluid or particle dynamics [32]. The convection terms have been included in these depth-averaged models, which makes them have obvious diffusivity. Excessive lateral spreading will be observed when the depth-averaged model is applied alone.  
The evolution characteristics of landslide total kinetic energy in these three simulations are different, which can be seen in Figure 13.  
In simulation (II) (\(t_{s}=2\) s), the total kinetic energy of the landslide increases slowly in the first 2 s but rapidly after 2 s, corresponding to a steep kinetic energy segment. In simulation (I) (\(t_{s}=4\) s), about the first 3 s, the total kinetic energy increases slowly; after that, the total kinetic energy decreases until about 4 s, which is mainly due to the interaction between the landslide and the road surface. After 4 s, in the depth-averaged model stage, the total kinetic energy began to increase rapidly. The total kinetic energy of simulation (III) also has evolution characteristics similar to those of simulation (I). In simulation (III), the multi-block model has the longest execution time, and the landslide is affected by the road surface for the longest time, resulting in the largest drop in total kinetic energy in the early  
Figure 12: Comparison of flow heights of three simulations.  
Figure 13: Evolutionary characteristics of total kinetic energy in simulations.  
stage. Within a few seconds of the triggering stage, if the occurrence of disintegration is advanced by 2 s, the maximum kinetic energy will increase by more than 20%.  
Landslides with initial high integrity often gradually disintegrate into fluid-like flows after maintaining a rigid or semi-rigid state for a certain period of time. When using the DAN3D model to simulate a landslide initiated by rainfall, [PERSON] et al. used two different rheological models, namely Coulomb friction and Voellmy, respectively, in the initiation area and accumulation area [33]. Different rheological models only lead to differences in friction terms. The model is still an equivalent fluid based on the depth-averaged principle, so it is suitable for analyzing landslides with high initial water content and obvious flow characteristics. [PERSON] et al. integrated the flexible block model with the depth average model of DAN3D and realized the continuation of the two models in time order with the help of liquefaction time parameters [27]. Their simulation results indicate that for landslides with high integrity and internal cohesion strength, the accurate analysis must consider the initial slow movement stage. Because the z-coordinate is vertically upward in the flexible block model but perpendicular to the terrain in DAN3D, a coordinate transformation is needed before the numerical modeling, which may lead to a reduction in calculation accuracy.