# A 3D Two-Phase Landslide Dynamical Model on GIS Platform
## 4 Results
The maximum deposit thickness for both profiles is situated in the central part of the  
Figure 5: Yigong landslide simulation using our three-dimensional model: (**A**) at 20 s using the three-dimensional model; (**B**) at 40 s using the three-dimensional model; (**C**) at 60 s using the three-dimensional model. channel, approximately 70 m. Along profile AB, the thickness of landslide deposits exhibits a variation along the frontal region. Commencing from 72 m at the central channel, it decreases to 16 m, subsequently increases to 27 m, and eventually decreases to 10 m. Similarly, along the rear edge of the landslide, the deposit thickness decreases from 72 m to 16 m, then increases to 22 m before finally decreasing to 0 m. At profile CD, the thickness of landslide deposits decreases from 72 m at the central channel to 0 m on both sides. Compared to the depth-averaged model, the landslide deposit thickness in the three-dimensional model is obtained by cumulatively summing the volumes of individual landslide cells within the three-dimensional grid. In contrast, the depth-averaged model calculates the landslide thickness by solving the governing equations. This implies that our three-dimensional model can attain a more detailed distribution of landslide deposit thickness, taking into account the influence of topographical factors. Figure 7 illustrates the velocity distribution of landslides and air at profile AB. The lower portion represents the motion of landslides and air, while the upper portion represents the motion of air. During the deposition phase of the landslide, the lower part of the fluid exhibits laminar flow as its primary mode of motion, while the upper part of the fluid, primarily composed of air, experiences turbulent flow. The landslide moves along the channel direction, with the velocity being minimal at the bottom and maximal at the top. Above the landslide, the air fluid generates a series of vortices through turbulent motion, with some being small and concentrated and others being large and dispersed. The interaction between these vortices contributes to the complexity of the air motion in this region. In the direction perpendicular to the channel, specifically along the CD profile, the fluid moves from the left side of the channel to the right side, i.e., from a relatively higher altitude to a lower one. In the central part of the channel, where the landslide deposits have the maximum thickness, the air exhibits turbulent flow, while laminar flow predominates in the remaining areas. The movement of the landslide is primarily characterized by laminar flow, with the velocity decreasing closer to the bottom (Figure 8). The pressure distribution along the AB profile from 20 s to 60 s is illustrated in Figure 9. Throughout the landslide motion, the pressure distribution corresponds to the extent of the landslide, with the bottom being consistently the area of maximum pressure and the top being the area of minimum pressure. Simultaneously, the three-dimensional model can capture more details during the landslide motion, such as fluid surges. Figure 6: Changes in Yigong landslide deposit thickness: (**A**) schematic diagram of profile AB and profile CD; (**B**) changes in accumulation thickness along profile AB; (**C**) changes in accumulation thickness along profile CD. Figure 8: Velocity at Profile CD(Arrows indicate the direction of fluid flow). Figure 7: Velocity at Profile AB (Arrows indicate the direction of fluid flow). Figure 9: Pressure at Profile CD: (**A**) pressure distribution of profile AB at 20 s; (**B**) pressure distribution of profile AB at 40 s; (**C**) pressure distribution of profile AB at 60 s.  
Our model effortlessly captures these details in the landslide motion process, indicating its capability for three-dimensional simulation of the intricate dynamics of landslides on the GIS platform.