Evolution Process and Failure Mechanism of a Multi‐Factor Coupled Loess Landslide: A Case Study in Xiangning County, China

Abstract

Loess landslides are major geohazards on the Chinese Loess Plateau, where rainfall and engineering activities commonly trigger slope failures that also drive slope‐to‐gully evolution. This study investigates the ZQ landslide (23 April 2023) in Xiangning County, Shanxi Province, using field surveys, UAV photogrammetry, SBAS‐InSAR, dynamic triaxial tests and finite‐element simulations to clarify deformation, material behaviour, geomorphic evolution and failure mechanisms. The landslide (200 m long, 308 m wide; 6.0 × 10 4  m 2 ) developed in a Quaternary loess–palaeosol sequence and showed episodic retrogression, producing three rear scarps. The sliding mass moved from one side of the gully toward the valley bottom, where the deposit partially occupied the gully and induced frontal bulging, showing local adjustment of the gully. SBAS‐InSAR revealed central displacement accumulation with peak line‐of‐sight displacement of −43.3 mm and a mean rate of −41 mm/year; deformation acceleration coincided with rainfall, especially the 71.6 mm total in April 2023. Dynamic triaxial tests show that saturated loess is sensitive to cyclic loading. Higher CSR and loading frequency accelerated plastic‐strain accumulation and dynamic strength degradation, providing laboratory evidence for cyclic‐load–induced weakening. Scenario‐based finite‐element modelling indicated progressive weakening under sustained rainfall. Under the coupled rainfall–vibration scenario, deformation became more toe‐controlled, with a maximum horizontal displacement of 4.28 m, toe uplift of 4.10 m and a factor of safety of 0.773. The development of a connected plastic zone indicates progressive failure and potential reactivation. The results suggest that rainfall‐driven infiltration softening within the loess–palaeosol stratigraphic structure was the main hydrological trigger, whereas mining‐related disturbance may have contributed to failure by promoting crack development, deformation accumulation and cyclic weakening of saturated loess. The landslide evolved through creep and cracking, crack propagation, shear localization, retrogressive sliding, frontal bulging, partial gully blockage and postfailure creep, linking slope failure with local gully evolution.