The initiation and motion characteristics of the “10·5” loess landslide in the Heifangtai platform, Gansu Province

Long-time diversion irrigation has led to the continuous rise of the groundwater level in the Heifangtai platform,Gansu Province. So far, more than 200 loess landslides have occurred, causing more catastrophic threats to local people and property. The loess landslides on the Heifangtai Platform were charactered by rapid initiation,fast speed and wide accumulation area. A loess landslide occurred near Dangchuan village in the Heifangtai Platform on October 5, 2019. The characteristics and topographic data of the landslide were obtained by field investigation and UAV technology. We used the Massflow software to simulate the motion process of the landslide, and the deposits thickness and motion speed of the landslide are obtained. The result show that: (1) The “10·5 ” landslide has a volume of about 2.7×10⁴ m³ and a maximum sliding distance of 355 m. It is a small kind of loess landslide; (2) The motion time is about 45 s, the maximum movement speed is 26 m/s, and the inversion result is consistent with the actual situation. The landslide movement process is divided into three stages: start acceleration→steady acceleration→deceleration accumulation; (3) It found that the average thickness and maximum accumlation thickness of the landslide in the main sliding direction were respectively 0.59 m and 1.35 m. The accumulation thickness shows a trend of increasing momently and then decreasing. The largest accumulation thickness is 0.82 m. The research results can provide related technical support for the risk prevention of the loess landslide occurred in the Heifangtai Platform.