DEVELOPMENT CHARACTERISTICS AND FORMATION MECHANISM OF LUANSHIBAO LANDSLIDE PONDS IN EASTERN MARGIN OF TIBETAN PLATEAU

The morphological elements and development characteristics of landslides are important contents of the field investigation and remote sensing image identification of ancient landslides, and the engineering geology analysis of infrastructure route/site selection in mountainous areas. Due to the complex geological environment, there are a lot of ancient landslides in the eastern margin of the Tibetan Plateau under the internal and external dynamic geological actions. This paper takes Luanshibao Landslide, a large ancient landslide in Maoyaba Basin in the eastern margin of Tibetan Plateau, as an example to study the morphological elements of landslide ponds. It uses the UAV photogrammetry technology, hydrogeological survey, spontaneous potential geophysical exploration and seepage numerical simulation. It explores the geometric characteristics and seepage development characteristics of the Luanshibao Landslide ponds. It further reveals the development characteristics and formation mechanism of the Luanshibao Landslide pords. The results show that low-lying terrain is formed on the platform and main scarp of the landslide after the occurrence of Luanshibao Landslide. The groundwater along the Litang-Dewu fault produces spring water and surface runoff. The continuous recharge of groundwater eventually forms a large landslide pond with a volume of 5505 m³. The maximum water depth is 2 m on the west side of the landslide pond. In the process of landslide movement, the secondary scarp is formed under the platform at the back edge of landslide. The long-term action of the high waterhead of the upper landslide pond leads to the internal seepage in the loose and broken material structure of the slope body on the west side of the back edge of the landslide. A spring appears in the middle of the steep secondary scarp, and then forms a small landslide pond with the volume of 35 m³ at the low-lying terrain. Under the action of long-term seepage, there is a potential seepage erosion risk in the accumulation body. It is suggested to carry out a long-term observation research on seepage potential erosion rate of spring point at secondary sliding wall in the later stage, which provides an important basis for the evolution of Luanshibao Landslide ponds.