Failure mechanism and river-damming risk analysis on "11·29" Baige Landslide on Jinsha River

After two consecutive river-blocking events at the Baige Landslide site on the Jinsha River in October and November 2018, three large remnant landslide masses (K1, K2, K3) remain in the source area, which still pose a potential threat of renewed failure and river damming. A partial reactivation occurred from November 29 to 30, 2022, which did not cause another river blockage but highlighted ongoing stability issues. In response to this renewed hazard, this study conducted engineering geological surveys, geophysical exploration, and surface displacement monitoring on the residual masses, focusing on K1-2 and K1-3. The investigation clarified their historical deformation patterns and potential failure volumes. Using the discrete element method (DEM) with PFC3D, a ball-wall model was developed to simulate the post-failure motion and depositional morphology of potential instability scenarios. The river-damming risk was evaluated quantitatively by applying a "truncated pyramid volume" calculation method. The results show that the K1-3 mass is currently in a creeping stage with significant deformation and a trend towards overall failure, while the adjacent K1-2 mass exhibits minor deformation and a lower likelihood of large-scale failure. However, in an extreme scenario in which the overall failure of K1-3 triggers the instability of K1-2, the combined slide could form a landslide dam approximately 46.19 m high in the Jinsha River, indicating a significant risk of landslide blocking the river.