Deformation mechanisms and evolution of a pile-reinforced landslide under long-term reservoir operation

Stabilizing piles are widely used for reinforcing landslides in the Three Gorges Reservoir area, China. Due to reservoir operations, long-term water-level fluctuations (WLFs) may cause instability or failure of the reservoir landslide and piles system (RLPS). This study experimentally investigated the deformation characteristics and mechanisms of the RLPS under long-term WLFs. The results showed that long-term WLFs led to loading and unloading cycles and consequently a weakening of the slope stability, where retrogressive failure and system instability were observed. Retrogressive failure at the slope toe was caused by topographical variation and physical and mechanical deterioration, which may be a result of the long-term WLFs. System instability was accompanied by a stress-release process above the new slip surface and was determined to be dependent on the geological structure of the RLPS. Based on this investigation, the evolution model of the pile-reinforced landslide under long-term WLFs was proposed. Even though the RLPS was adversely affected by the long-term WLFs, it maintained a relatively steady state due to the reinforcement of the piles. Effective pile installation changed the development of the reservoir landslides and prevented the entire slip surface from reaching a critical state. Thus, a catastrophic consequence was avoided, except for the local failure. Through physical modeling, this study experimentally provided a deeper understanding of the deformation mechanisms and evolution of the RLPS influenced by the long-term WLFs.