Numerical modeling of the vegetation and atmosphere effect on the behaviour of civil infrastructure embankments

Abstract

The soil-vegetation-atmosphere interaction is a dynamic process, which governs the continuous change of soil hydrological conditions. These changes directly affect the seasonal and long-term performance of infrastructure cut and embankment slopes. It has been established that the combined effect of vegetation and precipitation induces seasonal cycles of shrinkage and swelling, which give rise to serviceability issues and consequential high maintenance costs. Numerous researchers attempted to incorporate the effect of the soil-vegetation-atmosphere system interaction in the analysis of boundary value problems. The goal was to improve the understanding of the effects of this complex interaction on the hydro-mechanical response of infrastructure embankments. However, the proposed approaches were unable to quantitatively reproduce the observed hydraulic behaviour. Within the framework of the present thesis, a different approach is proposed. It is based on the fully coupled flow-deformation analysis, combined with unsaturated soil mechanics theory and sophisticated climatic boundary conditions, implemented within the ICFEP numerical code. Two types of unsaturated constitutive models were applied, elasto-plastic unsaturated Mohr-Coulomb type model and advanced BBM model. The instrumented railway embankment located in the UK, suffering from poor track ride quality related to the presence of vegetation on the slopes, is used for validation purposes. The comparative analysis suggests that proposed models are plausible representative of reality. Subsequently, a comprehensive parametric analysis is conducted. The results indicate that unsaturated hydraulic properties of clay fill represent the key factors governing the embankment response to seasonal wetting-drying patterns.