Stability analysis of unsaturated loess slopes subjected to extreme rainfall incorporating creep effects

Abstract

Rainfall-induced landslides are common natural hazards, particularly in cases involving unsaturated soils. Slope instability issues may arise due to extreme climate events, while, creep effects can also contribute to landslide problems. In this study, a modified ViscoElastic-ViscoPlastic constitutive model is developed to more accurately characterise the mechanical properties of unsaturated loess, considering stress-level dependency of stiffness and creep properties. In addition, to better characterise the collapsibility of loess, the relationship between strengths and matric suction has been introduced. The infiltration process of an unsaturated porous medium is illustrated by the Van Genuchten model and the generalized Darcy’s law. Additionally, the atmospheric boundary condition is incorporated in the numerical simulations, considering factors such as runoff generation and various climate events.In the context of slope stability analysis, a numerical approach has been developed to determine the safety factor of the slopes, by using displacement changes as the key assessment criterion. A good agreement between numerical and analytical results has been observed, verifying the proposed approach to determining safety factor. Finally, in parametric analyses, the effects of creep and matric suction on safety factor have been identified. Slope stability of unsaturated loess slopes subjected to different rainfall intensities and rainfall durations has been studied. The maximum depth of the sliding part increases obviously when considering the contribution of creep deformations, which is crucial in analysing slope stability.