Characteristics of failure area and failure mechanism of a landslide in Yingjiang County, Yunnan, China

Due to excavations and continuous rainfall, two landslides occurred on February 9, 2018, and July 28, 2019, respectively, in the quarry of the Changdifang Reservoir engineering area, in Yingjiang County, Yunnan Province, China. The volume of the second landslide was approximately 2.4 x 10(5) m(3), threatening the safety of construction workers and the hydropower station project construction severely. In order to explore the causes of these two landslides, the geological and hydrological conditions and the current excavation status of the landslide area were investigated, the relationship between rainfall and the displacement of the landslide body was compared and analyzed, and the landslide process and failure characteristics were described in detail. The failure mechanism of these two landslides were distinguished: (1) the poor rock mass properties, due to the strong weathering and tectonic joint of the rock mass; (2) the steep slope (of 63 degrees in largest dip angle) induced by the slope excavation, as well as (3) the continuous heavy rainfall. The unfavorable geological condition was a determinant factor, and the combined effects of excavation and continuous rainfall were triggering factors that induced the landslide. The research results show that the displacement of the landslide body has significant seasonal characteristics. In the rainy season, there is a significant acceleration of displacement, and the slow displacement will remain for a long time after the rainy season. Consequently, it is very necessary to take reasonable slope treatment measures and continue to monitor the slope.