Analysis on characteristics and reactivation mechanism of secondary landslides in the front part of the Xijitan giant landslide, Guide Basin

The upper reaches of the Yellow River, located on the northeastern edge of the tectonically active Qinghai Tibet Plateau, are characterized by complex geological conditions that have led to a high incidence of geological disasters such as landslides and collapses. This study focuses on the secondary landslide at the front part of the Xijitan landslide on the north side in Jiangla Village, Garang Township, Guide County, Qinghai Province. Using methods including unmanned aerial vehicle surveying, InSAR surface displacement monitoring, and on-site investigation methods, a detailed analysis of the geological environmental conditions, development characteristics, and reactivation mechanism of the landslide are conducted. On-site investigation results indicate that the rock mass structure in the landslide area is fragmented, with concentrated rainfall. The main exposed strata are Neogene mudstone and Holocene slope deposits. Multiple large cracks and tension bands are developed at the rear edge of the landslide, and the surface deformation is obvious, in the stage of creep deformation. Analysis of the mechanism of landslide reactivation reveals that densely developed structures play a controlling role in the reactivation of secondary landslides, and the softening of mudstone caused by concentrated rainfall is a key factor in inducing landslide reactivation. The interaction between two factors continuously reduce the integrity and strength of the rock mass, leading to the deformation and reactivation of secondary landslides. The research results aim to provide a theoretical basis for disaster prevention and reduction work in the upper reaches of the Yellow River.