Circular Causality in Rainfall-Induced Landslides: Bidirectional Feedback Between Shear Displacement and Pore-Water Pressure

Rainfall-induced landslides present significant hazards worldwide, particularly in regions experiencing intermittent storms. This study investigates the complex interactions between shear displacement (SD) and pore-water pressure (PWP) within a steep slate slope subjected to controlled rainfall conditions. Through a series of large-scale field experiments, we characterize the response of the slope across three distinct stages of deformation. Our findings reveal a bidirectional feedback mechanism, termed circular causality, wherein increases in PWP drive concurrent changes in SD, and vice versa, demonstrating that traditional linear models of slope failure are insufficient. Specifically, we identify four mesoscopic interaction modes between SD and PWP, highlighting how variations in soil moisture serve as reliable precursors for predicting abrupt slope deformations. These insights indicate that monitoring soil water content changes offers a more effective strategy for early warning systems in landslide-prone areas. Consequently, this study contributes to a deeper understanding of slope stability dynamics and provides essential guidance for the development of improved forecasting models and mitigation strategies in the context of climate variability.