Characteristics, mobility and dynamic of the Yahuokou flow-like landslide in Zhouqu, Gansu, China

At 18:00 on July 19, 2019, the ancient Yahuokou flow-like landslide in Dongshan Town, Zhouqu County, Gansu Province, China, was revived. The landslide mass of about 3.92 × 10 6 m 3 was revived step by step, slid down the slope, and finally slipped into the Minjiang river, causing the Minjiang river to become a semi-blocked state, the water level of the river rose, and the riverside road was interrupted. The landslide is 1920 m long, with a height difference of 550 m and an apparent friction coefficient of 0.286. It is a typical push-type large-scale long-striped fault-fractured zone accumulation landslide, which is controlled by the Pingding-Huama fault zone. Under the action of long-term rainfall, the trailing edge of the upper section of the landslide first undergoes slow creep deformation, which eventually leads to the overall instability and decline of the upper section of the landslide, and then loads the upper part of the middle section of the sliding mass, which promotes the instability and decline of the middle section of the sliding mass. Finally, the sliding mass in the middle section exerts a load on the upper part of the sliding mass in the lower section, which revives the sliding mass in the lower section and gradually slides into the Minjiang river. Through field investigation, remote sensing interpretation, and borehole investigation, the basic characteristics and information of landslide deformation and movement are obtained. The limit equilibrium method is used to analyze the revival mechanism and the spring model is proposed to analyze the movement mechanism of the landslide. With the help of DNA-W numerical simulation software, the sliding process of the upper sliding mass is simulated by a frictional rheological model to verify the spring model. The analysis of the dynamic mechanism of the Yahuokou flow-like landslide will help provide a reference for the research on the instability and movement mechanism of the landslide in the Pingding-Huama fault zone, and provide the necessary scientific basis for the prevention and mitigation of landslide disasters.