Numerical Modeling of Deformation Response of Embankment Subjected to Rainfall Infiltration Considering the Hydro-Mechanical Coupled Behavior of Unsaturated Soils

Embankments constructed using compacted fill are initially in an unsaturated condition. Deformations of embankments may occur due to softening effects associated with rainfall infiltration. In this study, a hydro-mechanical coupled constitutive model was implemented in the finite difference program FLAC with the two-phase flow option to simulate the hydro-mechanical behavior of unsaturated soil during wetting. The model adopts the Bishop's effective stress, which considers the combined effects of suction and degree of saturation on the stress-strain behavior and the effect of suction on the stiffness and hardening parameters. The implemented constitutive model was calibrated using experimental data from triaxial tests. Numerical simulations were conducted for a 6- m-high unsaturated embankment with a slope inclination of 1:1.5 subjected to rainfall infiltration. As water infiltrates into the embankment, the differential settlement on the embankment top surface increases, and the lateral displacements of slope surface also increases significantly. Even though failure may not occur after the embankment becomes full saturation, a potential failure surface appears to initiate at a shallow depth of approximately 2 m from the slope surface. The implemented hydro-mechanical coupled model enables the prediction of failure surface forming within the embankment slope that could lead to serviceability issues subjected to rainfall infiltration.