Mechanism and causal analysis on the Yahuokou landslide reactivation and causes (Zhouqu County, Gansu, China)

The report described a recent landslide happened in Zhouqu Country, China. At 18: 00 pm Beijing time, on July 19, 2019, the Yahuokou landslide was reactivated, about 3.92 × 10⁶ m³ of debris slumped from the slope caused Minjiang River channel blockage, water level rise, and road interruption. Fortunately, nobody was injured. In order to seek the geomorphologic and stratigraphic characteristics, the reactivated causes and the dynamics mechanism of the landslide, field survey, remote sensing image, drilling prospecting, landslide monitoring and rainfall data analysis were conducted. The outlook of the landslide event was given. Evidences of the sliding zone indicated the landslide is a flow-slide deformation pattern. The landslide mechanism is summarized as: firstly, slow plastic flow-slide occurred in the upper sliding body. Then the platform in the middle gentle slope was preloaded by the post upper part failure deposits, resulting in the “cutting and filling” effect. The failure form is creep-tension cracks-debris flow-slide. At last, the block on the lower part slumped. Specifically, the upper, middle and lower parts of the landslide all transferred stress in this mode, being activated step by step, and slowly slumped into the river.