Movement Process Simulation and Failure Mechanism Investigation of the Yuqiong Landslide Deposit Based on Massflow

The Yarlung Zangbo River region is characterized by complex geological structures and distinctive physiographic environments, where landslide deposits are susceptible to deformation and instability under internal and external forces. Therefore, determining their potential movement processes, kinematic characteristics, and failure modes is crucial for landslide hazard prevention and mitigation. Taking the Yuqiong landslide deposit as a case study, this paper employed field investigation, laboratory testing, and numerical simulation to model its instability and failure process, as well as analyze its movement characteristics and the failure mechanism. The main results are as follows: (1) The entire sliding process of landslide instability and failure lasts approximately 100 s. The deformation and instability process can be divided into four stages: initiation and sliding, deformation propagation, deformation accumulation, and cessation. The velocity evolution comprises three stages: start-up acceleration (accounting for 10%), rapid deceleration and slow deformation (together accounting for 90%). The initiation of the crown exhibits a certain degree of suddenness. (2) The energy distribution during landslide instability is controlled by topographic slope, sliding mass thickness, and travel distance. At the crown, where the slope is steep, the thickness is large, and the travel distance is short, frictional energy dissipation is low, resulting in concentrated energy. In contrast, at the toe and the middle part, where the slopes are gentle and the travel distances are long, energy dissipation is high, leading to lower energy distribution. (3) The deformation and failure mechanism of the landslide is characterized as follows: active thrusting at the crown drives the movement; the toe, owing to the gentle slope and thick layer that provide high sliding resistance, undergoes slow retrogressive buffering; the middle part is subjected to both pushing and pulling, resulting in settlement and stress transfer. Overall, the landslide exhibits a composite progressive failure mode combining crown thrusting and toe retrogressive action.