Landslide-terrace interaction mechanisms of two rapid loess landslide cases: insights from MPM modeling
摘要
Loess landslides are major hazards in Northwest China and often result in severe casualties and property losses. The southern Jingyang loess tableland in Xianyang City, Shaanxi Province, China, is one of the most active areas for loess landslides. Rapid long-runout flowslides and relatively short-runout slides are the two representative landslide types in this region. Both of them exhibit clear landslide-terrace interaction, yet their entrainment characteristics differ, and the governing mechanisms remain poorly understood. Therefore, this study investigates two well-documented landslides that are representative of these two types, respectively, the Dongfeng landslide (rapid long-runout flowslide) and the Shutangwang landslide (relatively short-runout slide), using a material point method (MPM) model that incorporates entrainment effects. The results indicate that the entrainment mode of the Dongfeng landslide involves shearing of terrace materials by the loess sliding mass, whereas the entrainment mode of the Shutangwang landslide is characterized by thrusting of terrace materials. These distinct entrainment patterns should be primarily attributed to differences in the liquefaction susceptibility of the terrace materials, which are controlled by pre‑landslide topographic and hydrogeological conditions. Prior to failure, the Dongfeng landslide site featured a longer terrace with poor drainage and a relatively shallow groundwater level. As a result, the sand and gravel in the terrace are prone to liquefaction under the impact of the loess slide, which reduces sliding resistance and promotes a longer runout distance. In contrast, the Shutangwang landslide site has a shorter terrace with better drainage and a deeper groundwater level. Consequently, the liquefaction potential of the sand and gravel in the terrace is relatively low, leading to a shorter sliding distance.