Numerical study on the evolution process of a geohazards chain resulting from the Yigong landslide

Geohazard chain processes in mountainous areas generally entail a landslide, followed by a dammed lake, a dam breach, and then outburst flooding. These chains have greater destructive power and a larger area of coverage than a single process, of which a representative event is the April 2000 Yigong landslide in Tibet, China. In this study, a two-part, numerical back-analysis of the entire chain process is carried out. Enhanced one-layer Savage-Hutter models, which incorporate a multiscale, empirical friction model (velocity-weakening) and appropriate erosion mechanics, are solved using a non-staggered central differencing scheme. A reasonable reproduction of the geohazard event chain was obtained. Results show that the use of the multiscale friction law is able to reproduce the dynamic process of the landslide with acceptable accuracy. In addition, the variation of soil shear resistance along the dam depth (against the water flow above) during the dam breach is considered in the study, in which the outburst flooding process is better modeled. The numerical results, validated by field measurements, provide reliable assessment and interpretation of the actual event.