Objective Under the combined disaster-inducing effects of accumulated disturbance from historical strong earthquakes, human engineering activities, and heavy rainfall, the Caoping Village landslide in Wudu District, Gansu Province, has shown obvious deformation. This landslide is a typical engineering-disturbed landslide in a mountainous area, but systematic studies of this type of landslide remain insufficient.

Methods This study integrates SBAS-InSAR deformation monitoring, borehole exploration, and GeoStudio numerical simulation to predict landslide stability under natural, rainstorm, and earthquake conditions and to reveal the instability mechanism of this type of landslide.

Results The results show that long-term disturbance from historical strong earthquakes promoted extensive fracture connectivity and significant weakening of the mechanical strength of the rock and soil mass, providing the material basis for landslide instability. Engineering activities such as slope cutting for housing construction and road building removed the natural support at the slope toe and induced stress unloading and redistribution. Under natural conditions, the stability coefficient is 1.042, indicating that the slope is in an under-stable state. Under heavy rainfall, the phreatic line fully penetrates the sliding zone after 5 h of infiltration, pore water pressure continues to rise, and the stability coefficient decreases to 0.983, indicating a transition from an under-stable to an unstable state. Under earthquake conditions, the vertical effective stress in the sliding zone decreases sharply during the peak seismic-wave period, and the stability coefficient drops instantaneously to 0.921, showing that dynamic deterioration is more severe than rainfall-induced deterioration.

Conclusions These findings provide a theoretical reference for investigating the instability mechanisms of similar engineering-disturbed landslides in mountainous areas and have practical significance for mountain engineering planning, landslide monitoring and early warning, and disaster prevention and mitigation.