Mathematical and computational modelling of vegetated soil incorporating hydraulically-driven finite strain deformation

In this paper a new model for the hydro-mechanical behaviour of rooted soils is developed. It is a physically-based model that couples finite strain soil deformation with unsaturated water and air flow, while improving on existing cohesion-based approaches to mechanical root reinforcement and empirical soil water-uptake approaches typically used to deal with rooted slopes. The model is used to show that the dynamics of soil-water pressure and soil deformation depend strongly on the physics of the root-water uptake and the elasto-plastic soil mechanics. Root water uptake can cause suctions and corresponding soil shrinkage sufficiently large to necessitate a finite-strain approach. Although this deformation can change the intrinsic permeability, hydraulic conductivity remains dominated by the water content. The model incorporates simultaneous air-flow, but this is shown to be unimportant for soil-water dynamics under the conditions assumed in example simulations. The mechanical action of roots is incorporated via a root stress tensor and a simulation is used to show how root tension is mobilised within a swelling soil. The developed model may be used to simulate both laboratory experiments and full-scale vegetated slopes.