NUMERICAL INVESTIGATION ON IMPACT OF BED ENTRAINMENT TO THE MOBILITY OF RAPID FLOW-LIKE LANDSLIDES

Rapid flow-like landslides are characterized by their high mobility and catastrophic consequences. These landslides tend to entrain a great amount of loose materials along their travelling paths, resulting in the enlargement of landslide volume and covering area. This phenomenon is called bed entrainment/scouring in literatures. Although previous studies showed that bed entrainment was a significant factor influencing the mobility of rapid flow-like landslides, few of them considered its impact on the rheology of the sliding mass, and needless to say quantifying this impact in numerical modeling. Therefore, this paper proposes an improved finite difference model based on momentum conservations of both the landslide and erodible mass. In this model, the influence of bed entrainment on the rheology of a landslide is quantified by modifying the rheological parameters of the landslide according to the calculated entrainment depth. Then the Ximiaodian landslide, a typical rapid flow-like landslide located at the south bank of the Jinghe River in Shaanxi Province, is simulated by the new model. It shows that the run-out process of this landslide can be divided into the rapid acceleration stage(0~5 s) and the slow deceleration stage(5~14 s). During the acceleration stage, the extent of entrainment is small, so its impact on the motion of this landslide is slight. However, the entrainment obviously promotes the mobility of this landslide at the deceleration stage by reducing the basal resistance. In addition, the modeling results of considering and not considering bed entrainment show totally different patterns. The simulated covering area and final deposit agree well with the measured data when adopting the improved model, while those neglecting the impact of bed entrainment-induced rheology change are obviously smaller than that of the fact. It turns out that the new model proposed here is more suitable for simulating those rapid flow-like landslides with similar bed entrainment phenomenon.