The climatic changes induce now more and more serious environmental problems such as landslides, especially in arid and semi-arid countries where rainfalls happen with high and short duration intensity. This paper aims to study the influence of unsaturated mechanical properties on the slope instability. The research was conducted based on the combination of a physical model and numerical simulations with the aim to analyze rainfall-induced slope failure. The benefits of the proposed method are: 1) increase of monitoring efficiency by considering several parameters in large ranges of variation; 2) cost reduction by a combination of minimal laboratory physical model data and numerical modeling. In this study, the effect of rainfall intensity and duration as a hydraulic loading was investigated. The used model is an elastoplastic one based on effective stresses and a non-associative flow rule. A function of a reduction of mechanical parameters with suction was implemented in CODE_BRIGHT software. The results are presented in terms of: 1) displacement values; 2) evolution of pore water pressure (PWP); 3) plastic deviatory strains and saturation zones.