Abstract ID: 3.5325 | Pending | Talk/Oral | TBA | TBA

The conventional methods employed to understand the potential failure mechanism associated with rainfall-induced landslides are based on the assumptions of soil-saturated characteristics. Generally, these types of analyses are semi-coupled, where active pore pressures are split in a steady-state part, generated prior to the deformation analysis based on either phreatic levels or a steady-state groundwater flow analysis, and an excess part that results from undrained loading in the deformation analysis. However, the analysis of rainfall-induced landslides is a transient flow problem, and most of the hill slopes, especially in tropical regions, are usually established in an unsaturated state. Therefore, the coupled modeling of seepage and deformation is crucial as the pore water pressures generated due to the flow of a fluid result in deformations in soil, but these deformations, in turn, cause variation in the fluid pressure. To consider both the deformation and seepage flow, the Couple Flow Deformation (CFD) module can be implemented via the available commercial Finite Element (FE) based computer program PLAXIS 2D/3D. The CFD analysis is based on Biot’s three-dimensional consolidation theory, which integrates the equilibrium and continuity equations of the soil-water matrix. This enables the simultaneous computation of seepage and deformation under steady-state and transient flow conditions in unsaturated soil. The Hardening Soil (HS) model can be used to describe soil as a non-linear elastic-plastic material with a hyperbolic stress-strain relation in the CFD finite element analysis. The key benefit to using the HS model over the Mohr-Coulomb model is that the HS model can better simulate soil displacement at large strain conditions. The flow model is also required in the CFD FE modeling to generate the soil water characteristic curve (SWCC), which relates the suction in the unsaturated zone to the degree of saturation. To describe the transient flow behavior, the van Genuchten hydraulic model is one of the best available flow models that can be implemented. Using the CFD analysis, the spatiotemporal variation of slip surface, safety factor, internal stresses, deformation, and parameters responsible for failures can be captured, which may be used to develop site-specific early landslide warning systems, evacuation plans, etc.