Response of anisotropy modeled compacted embankment during infiltration

Abstract

During rainfall, collapse compression predominates due to the slippage of particles, resulting in the rearrangement of soil fabric toward a configuration dependent on the fabric of the initial stress state. Consequently, these alterations in soil fabric induce anisotropic mechanical behavior in unsaturated soils. In this study, an anisotropic model, denoted as ABBM and based on the Barcelona Basic Model (BBM), was implemented into FLAC to analyze the wetting behavior of a typical compacted embankment during infiltration. The research findings indicate that prolonged rainfall durations result in the evolution of the yield surface, consequently amplifying vertical surface displacement. Moreover, as the anisotropic evolution parameter surpasses a defined threshold, the degree of anisotropy diminishes, ultimately resembling the isotropic behavior observed in the Barcelona Basic Model (BBM) due to changes in preconsolidation pressure. The study presents an innovative approach to evaluate embankment performance under rainfall-induced conditions by considering changes in fabric anisotropy relative to the degree of saturation. The results demonstrate that alterations in the degree of saturation lead to rotation of the yield surface, nearly erasing anisotropy upon reaching full saturation. To account for parameter variability, a reliability analysis was performed using the Monte Carlo method, assessing the performance of embankment using different constitutive models, viz, the Mohr–Coulomb model, BBM, and ABBM. Notably, the analysis revealed that embankment failure probabilities simulated using the ABBM exceed those obtained using the Mohr–Coulomb criterion or BBM, suggesting a greater susceptibility to failure in terms of deformations. This observation has practical significance in a sense that use of appropriate constitutive models in embankments is required.