A dynamic model for rainfall-induced landslides on natural slopes

Abstract

Assessment of landslide hazard often requires a good knowledge of the landslide characteristics and runout mechanics. In this paper, a quasi-three-dimensional model using Lagrangian finite element method (LFEM) is formulated to reproduce the dynamic runout process caused by landslides. A case study of rainfall-induced landslide on a natural slope in 1993 in Lantau Island, Hong Kong, is presented. Voellmy rheology is adopted to characterize the multi-dimensional runout behaviour. For engineering applications, the selection of appropriate rheology and the determination of relevant key parameters associated with the failure mechanisms and runout mechanics are highlighted. Details of the mathematical formulation, particularly with respect to the stability of the numerical scheme and quality control of the mesh, are provided. The close correlation between the calculation results and the field observations shows that, if an appropriate rheological relationship is selected for the simulation, a reasonable description of the runout behaviour can be obtained using the present model. Implications of the potential hazard from natural terrain landslides to downslope development are also discussed. Used in conjunction with Geographical Information System (GIS) database, the model can also be applied to the preliminary hazard zoning of terrain and land-use management in mountainous areas.