## 4 Results
### Particle Transport Results of 3D Dam Model  
The particle transport process within the Conaxue Co landslide dam under seepage conditions is presented in Figure 11. During the initial stage of fluid loading, a portion of fine particles within the dam's fine-grained layer was eroded and transported downstream (Figure 11A). As fluid loading continued, finer particles within the dam's coarse-grained materials began to migrate towards the downstream side (Figure 11B). Ultimately, a significant quantity of fine particles was transported downstream under the influence of the seepage field (Figure 11C). Although partial particles were transported to the downstream side of the dam due to flow drag force, the entire dam remained in a stable state. This observation indicates that the migration of small amounts of fine particles does not compromise the overall stability of the dam. Figure 11: The results of particle transport within the 3D dam model under seepage conditions. (**A**)—initial phase; (**B**)—intermediate phase; (**C**)—final phase. A\({}_{2}\) and A\({}_{3}\); B\({}_{2}\) and B\({}_{3}\); C\({}_{2}\) and C\({}_{3}\) are zoomed-in views of Figures A, B, and C, respectively. Figure 10: Particle grading distribution of the Conaxue Co landslide dam. zones of high hydraulic head gradually expanded downstream (Figure 12A1-D1). The analysis of hydraulic head distribution among dam particles revealed that the hydraulic head gradient formed by internal particles creates differential force distributions within the dam, leading to the development of seepage fields (Figure 12A2-D2). The seepage field distribution confirmed that the seepage field in the dam's coarse-grained layer is markedly more pronounced than in the fine-grained layer (Figure 13). This observation demonstrated that the dam's coarse-grained layer experiences more intense hydrodynamic forces, thereby mitigating severe fluvial erosion on the underlying fine-grained sediments. As shown in Figure 14, particle displacements within the dam body at different time intervals reveal significant downstream slope movement due to water impact. The maximum displacement (0.36 m) occurred at the toe of the downstream slope. Nevertheless, the dam maintained overall stability. The interior of the landslide dam consists of numerous particles. Contact forces formed between the particles, and the network of these contact forces constituted the contact force chain distribution map (Figure 15). During the initial stage of seepage, the Conaxue Co landslide dam remained in an overall stable state (Figure 15A). Due to the differing particle size distributions and porosities between the dam's coarse-grained and fine-grained layers, the resulting contact force chain distributions exhibited distinct characteristics. The contact force chain distribution in the coarse-grained layer was relatively sparse, which indicates larger porosity among the coarse particles. Conversely, the distribution in the fine-grained layer was more uniform and denser, corresponding to smaller porosity and greater compaction degree (Figure 15B,C). Under sustained seepage effects, both the coarse-grained and fine-grained layers were subjected to seepage-induced forces that influence the dam's stability. However, the dam maintained overall stability (Figure 15D). Porosity variations at different locations within the dam were monitored using measuring circles (Figure 16). As shown in Figure 16A, the porosity at Measuring Circle 1 was higher and exhibited greater variation. This is because Measuring Circle 1 is located in the coarse-grained layer, which naturally possesses higher porosity and greater particle size variation. The larger interstitial spaces between coarse particles facilitated the migration of finer particles. In contrast, the fine-grained layer has a higher compaction degree and limited particle movement. Figure 16B demonstrates the degree of porosity variation at different locations.