In this study, a pioneer work on characterizing rainfall-induced shallowlandslides in layered soils using unsaturated flow equation is proposed.Several models using different mathematical approximations fordescribing the nonlinear physical relationships of the soil-watercharacteristic curve were introduced. The Gardner exponential modelwas adopted to derive analytical solutions of unsaturated flow problems.To model the rainfall-induced shallow landslides, the slope stabilityanalysis coupled with the hydrological model with the consideration ofthe fluctuation of pore water pressure for soil water characteristic curvewas developed. The results obtained from this study demonstrate thatthe slope stability of landslides is strongly dependent on the hydraulicconductivity. It is found that the variation of pore water pressure inunsaturated layered influences the stability of a slope. Besides, thepressure head at the interface increases quickly and the lowest safetyfactor may occur at the interface between two consecutive soil layersduring a rainfall event.
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