An approach to calibrate the unsaturated hydraulic properties of a soil through numerical modelling of a small-scale slope model exposed to rainfall.

Numerous studies have looked at rainfall infiltration as a triggering factor for rainfall-induced landslides. In addition to rainfall characteristics, soil hydraulic properties are recognized to play a crucial role in instability mechanisms. This study proposes a methodology for assessing the soil-water characteristic curve and hydraulic conductivity function through finite-element seepage modelling of physical model tests. The approach is applied to an instrumented, small-scale slope model built with uniformly graded sand with a 30 degree inclination, exposed to homogeneous rainfall until the occurrence of failure. In a first stage, a sensitivity analysis is carried out to assess the influence of the Mualem–van Genuchten model parameters on the slope response. For this purpose, six physically based indicators are utilized to compare the numerical modelling results with the experimentally obtained data regarding the hydraulic response of the slope model. In the subsequent stage, a trial-and-error calibration stage is conducted to determine the set of parameters for which the difference between the numerically and experimentally acquired data is minimized. Ultimately, the suggested methodology facilitates the assessment of the optimal set of hydraulic parameters, to which both the sensitivity analysis and the trial-and-error calibration phase are anchored. The approach has demonstrated its effectiveness in calibrating the unsaturated hydraulic properties of the considered soil, as it properly addresses the physical mechanisms associated with rainfall infiltration in a slope. [ABSTRACT FROM AUTHOR]