The weak mechanical properties of weak interlayers are crucial for controlling landslide deformation and failure under water level fluctuation. The instability and failure of landslides in reservoirs can lead to unpredictable consequences. In this study, the reservoir bank landslide with a weak interlayer was selected as the research subject. The material composition, structural characteristics, mechanical properties, and permeability of the landslide were determined through field investigations and tests. Additionally, a physical model test was conducted to explore the groundwater variation rules and deformation failure modes of landslides with weak interlayers under different water level fluctuation rates. The results indicate that due to the low permeability of the interlayer, there was a significant lag in monitoring data such as pore water pressure within the interlayer under the same water level fluctuation rate. At the same point, the faster the water level fluctuation rate, the greater the degree of lag. The deformation and failure mode of landslide with weak interlayer under reservoir water level fluctuation can be summarized as the following five stages: slope toe erosion stage, cracks on slope surface and interlayer stage, micro-collapse of slope toes and crack expansion of slope surface and interlayer stage, local micro-collapse of slope toe and crack penetration of slope body stage, crack development leads to landslide of slope body stage. This study provides theoretical support for prevention and control of landslides with weak interlayers in the gravel soils of reservoirs.

The construction of the Three Gorges Reservoir dam in China has led to an increase in reservoir landslide events. To mitigate these geohazards, multiple rows of stabilizing piles (MRSP) have been employed to stabilize massive reservoir landslides. This study utilizes centrifuge and numerical modeling to investigate the behavior of unreinforced landslides and MRSP-reinforced landslides in reservoir areas. The failure mechanisms of unreinforced landslides, as well as the mechanical behavior and stabilizing mechanisms of MRSP under reservoir water level (RWL) fluctuations, are examined. The results indicate that elevated downward seepage forces contribute to prefailure sliding, but are not the sole cause of catastrophic failure. Instead, rapid pre-failure sliding leads to soil particle compression and crushing in the saturated sliding zone, resulting in excess pore water pressure and accelerated overall failure. This excess pore water pressure-dependent mechanism explains the observed steplike deformation pattern and rapid failure pattern in reservoir landslides. Furthermore, the study reveals the formation of soil arches between adjacent MRSP groups, causing stress concentration on boundary columns and necessitating reinforcement. The finding challenges traditional one-dimensional load transfer ratios, advocating for a two-dimensional approach that accounts for variations across rows and columns. Notably, the study also highlights significant variations in load transfer laws within MRSP under different RWL operations, emphasizing the need for a more nuanced understanding of MRSP behavior.