The study incorporates the hydro-mechanical behavior and stability of unsaturated Himalayan debris slope which subjected to rainfall infiltration by using numerical modelling techniques. It also includes the laboratory tests to determine Soil Water Characteristic Curve (SWCC) which defines the relationship between soil suction and volumetric water content. The parameters of SWCC are critical to governing unsaturated soil behavior. The SWCC is evaluated from filter paper method and the results are compared with the SWCCs obtained from empirical methods and literature. The column test using tensiometer was also attempted to compare with the SWCCs. The experimental SWCC data provides essential input parameters for numerical models which enables accurate representation of transient seepage and moister migration within slope profile.  |
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Two-dimensional numerical analysis was performed using PLAXIS 2025 and GeoStudio 2025 to simulate the rainfall infiltration and assess slope stability under the rainfall infiltration. The models incorporated uncoupled flow deformation analysis to capture progressive development of pore water pressures, change in soil suction and corresponding reactions in shear strength during rainfall. The effect of initial maximum suction and permeability were studied for rainfall infiltration of year 2020. The back analysis was done to evaluate the slope properties. The numerical analysis was also done in PLAXIS 2D using coupled flow deformation approach. The changes in pore water pressure profiles were studied from CFD analysis. The results were compared for uncoupled as well as coupled analysis.
Result demonstrated significant influence of rainfall intensity and duration on the transient pore pressure response, critical slip surface development and factor of safety evaluation in unsaturated soil slope. The integration of laboratory-derived SWCC parameters with numerical modelling proved essential for reliable prediction of rainfall-induced slope instability mechanism.
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