Evolutionary and dynamic processes of the Zhongzhai landslide reactivated on October 5, 2021, in Niangniangba, Gansu Province, China

On October 5, 2021, a small-scale catastrophic loess landslide occurred in Niangniangba town, Tianshui City, Gansu Province in China. The landslide with a volume of approximately 15,360 m 3 buried 2 houses and damaged another 2 houses. On the basis of field investigation, unmanned aerial vehicle photography, and numerical simulation, the characteristics and dynamic processes of the Zhongzhai landslide are analyzed, and the potential destructive zone of the unstable loess mass is preliminarily assessed. The Zhongzhai landslide is a typical rainfall–reactivated flow-type loess landslide, and its failure mode is creep-tensile type. The upper sliding mass is the typical retrogressive failure, and the lower sliding mass shows thrust load caused failure. The runout simulation results show that the entire sliding process of Zhongzhai landslide lasted for approximately 35 s, with a maximum velocity of 12 m/s. The maximum travel distance of the sliding mass is 130 m. In addition, the presence of masonry buildings has a great influence on the sliding distance. Simulation results of potential destructive zone of the unstable loess mass show that the travel distance of the unstable loess mass is approximately 250–295 m, the thickness of the deposited mass is approximately 2.7–3.3 m in the potential destructive zone, and the maximum velocity is 28 m/s. This work contributes to improving the understanding of evolution law, dynamic processes, and risk prevention of this kind of landslide in loess plateau areas.