Deformation monitoring and landslide blockage-outburst flood simulations of an unstable slope in the Yigong river valley, southeastern Tibetan Plateau
摘要
The eastern margin of Tibetan Plateau is the area of the most active and intense internal and external dynamic action in Chinese mainland, where large unstable slopes are well developed. This type of slope instability is prone to form a complex landslide disaster chain. Through field investigations, SBAS-InSAR, and numerical simulations, failure characteristics, deformation monitoring and landslide-barrier lake-outburst flood disaster chain initiated by slope failure were studied. The results show that the steep topography of the slope provides favorable free-face condition for slope possible instability. Under the influence of faults, freeze-thaw cycles, the deformation and failure phenomena of the slope are obvious. During the monitoring period, the most intense deformation areas are located at the leading edge of the slope. The maximum annual mean deformation rate and maximum cumulative deformation value were 60 mm/yr and 320 mm, respectively. Landslides are most likely in the upper and middle slope areas. Landslide will take approximately 70 s from start-up to the formation of the barrier dam. A barrier lake with a maximum dam height of 110 m and a storage capacity of 1.16 × 109 m3 can be formed. After the dam-break flood occurred, the maximum depth of the outburst floods at the site of the downstream Yigong Zangbu Bridge could reach 18 m. In light of these findings, strengthening multi-source collaborative monitoring (satellite, aerial, ground, and subsurface) in the study area and formulating targeted “four precaution” measures are recommended.