Loess landslides represent significant geohazards occurring on the Loess Plateau, China, yet their failure mechanisms remain poorly understood due to complex hydro-mechanical interactions at soil-rock interfaces. This study investigates the Zhangjiawan ancient landslides (ZJWALs) with a loess-mudstone sequence. The multidisciplinary approaches integrating field surveys, Interferometric Synthetic Aperture Radar (InSAR) deformation monitoring, and numerical simulation were employed to unravel their basic characteristics, deformation process, and failure mechanisms. Key findings reveal that loess-mudstone slope structures exert fundamental control on landslide initiation, with frontal anthropogenic activities and rainfall identified as primary triggers for current erosion and reactivation. The ZJWALs are classified as a thrust-type landslide with a total area of 2.85 × 105 m2 and a reactivated volume of 3.33 × 106 m3, accounting for 38.9% of the original landslide mass. Kinematic analysis identifies four deformation zones that are spatially correlated with existing geological structures, and field evidence confirms pervasive creep deformation across the landslides. Further simulations using a depth-averaged model indicate that the landslide would compromise roughly 55% of the cement plant's footprint and its associated infrastructure through extensive burial. These insights advance our understanding of ancient landslide reactivation mechanisms in loess-mudstone terrains and inform disaster mitigation strategies.
