Abstract: The mechanism governing the transition from creep to rapid movement is a central challenge in understanding the instability of reservoir landslides. This study focuses on the Muyubao landslide, a giant bedding landslide in the Three Gorges Reservoir Area that exhibits persistent creep. This study focuses on the Muyubao landslide, a giant bedding landslide exhibiting persistent creep in the Three Gorges Reservoir Area. A series of ring-shear tests were conducted on the slip zone soil, revealing that its residual friction coefficient depends on both normal stress and displacement rate. Specifically, friction weakening, characterized by exponential decay, occurred at low displacement rates, whereas slight friction strengthening, characterized by logarithmic increase, emerged when the displacement rate exceeded a critical threshold (v = 3.33 × 10−4 m/s). The research indicate that friction weakening is the dominant mechanism driving the transition from slow creep to catastrophic failure by promoting accelerated creep through a positive feedback loop of “rate increase–friction weakening–further rate increase.” Based on the experimental results, a 3D slice-based dynamic calculation model was established that incorporates normal stress, rate-dependent frictional behavior, and variations in pore water pressure. This study reveals the potential deformation and instability mechanisms of the MYB landslide and provides essential theoretical support for predicting instability velocity and evaluating the movement tendency of creep-type landslides in reservoir areas.

Key words: Muyubao landslide, slip zone soil, ring-shear test, creep-to-fast movement transition mechanism, dynamic model