Numerical simulation of the Rongcharong paleolandslide river-blocking event: implication for the longevity of the landslide dam

Numerous paleolandslide dams are distributed along the upper reaches of the Jinsha River under the special geological setting of the Tibetan Plateau. A field investigation revealed that the Rongcharong paleoriver-blocking event formed one such dam. Optically stimulated luminescence results show that the paleolandslide occurred in 2.2 ± 0.1 Ka BP and blocked the Jinsha River for approximately 800 years. The failure mechanism of the paleolandslide is the steeply inclined antidip rock topple under self-gravity. A distinct element method-based numerical landslide model is constructed using the topography restoration method. The parameter sensitivity results show that microparameters have important effects on the peak particle velocity and morphology of landslide dams. The optimal microparameters are determined by adopting back analysis based on the geomorphic parameters of the landslide dam. The numerical simulation results show that the sliding process lasts for 65 s; the corresponding peak velocity and runout distance are 28.2 m/s and 742.5 m, respectively; and the landslide forms a dam 1129 m long, 967 m wide, and 105 m high. The genetic mechanism of the paleolandslide is reflected in the calibration process of the microparameters and load type of the numerical simulation. Finally, the implications of microparameters for the longevity of the landslide dam are presented.