Abstract Red bed slopes, owing to their inherent water sensitivity and strong tendency to disintegrate, are highly susceptible to instability under rainfall conditions and pose severe threats to human life, property, and major engineering infrastructure in red bed regions. However, existing studies on red bed slopes have focused mainly on landslide failure mechanisms triggered by single extreme rainfall events, whereas the cumulative deformation induced by antecedent rainfall has received far less attention. Through detailed field investigations, rock mechanical experiments, and numerical simulations, this study investigates the Sanxicun (SXC) landslide that occurred in 2013 in Dujiangyan City, Sichuan Province. The results reveal that the mudstone layers and wide tensile cracks that developed at the rear of the slope strongly influence the instability of the SXC slope. The time‐dependent evolution of the mechanical properties of red bed mudstone with respect to rainfall duration was examined. Numerical simulations indicate that under intermittent rainfall conditions, slope deformation increases in a stepwise manner: The deformation rate accelerates at the onset of rainfall and decreases markedly after rainfall ceases. On the basis of the deformation curves, the deformation process can be divided into three stages: rapid growth, slow growth and stable. In addition, rainfall sequences have a significant effect on slope deformation: The cumulative deformation caused by successive events of increasing rainfall intensity is greater than that induced by successive events of decreasing rainfall intensity. Moreover, greater cumulative deformation resulting from intermittent rainfall significantly accelerates the gravitational deformation of the slope during rainfall interval periods. These results demonstrate that cumulative deformation induced by historical rainfall plays a critical role in the stability of red bed slopes.
Zhu et al. (Sun,) studied this question.