Impact of Depth Distributed Plant Water Uptake on Slope Safety

Thousands of cut slopes in the UK, support the country's infrastructure. Pore Water Pressure (pwp) and suction can affect the stability of geotechnical infrastructures. Rainfall reduces suction and increases pwp, decreasing soil shear strength and stability. Near surface pwps are significantly influenced by environmental conditions and vegetation. High water demand from trees with extensive root zones can generate suctions at great depths through plant water uptake. It is expected that with climate change, average rainfall and intense rainfall events will increase. It is important to predict how suctions and pwps will respond to climate conditions and how vegetation will respond to these changes.Vegetation also causes serviceability issues by cyclic shrinking and swelling of high plasticity clays. It plays a significant role in both safety and serviceability of infrastructures, rendering detailed numerical analysis important. This study shows the importance of soil-plant-atmosphere interaction and its effect on slope safety. By implementing boundary conditions (BC) that account for climate and vegetation changesand its physiological responses, the infrastructure's performance can be studied. For this purpose, a typical cut slope in UK has been chosen. It is assumed that the slope is covered with a deciduous tree forest with 2 m deep roots. In this paper, the placement of BCs and its effect on the infrastructure's safety is discussed. Plant water uptake was considered using the ecohydrological model T&C and is used in a fully coupled flow-deformation analysis in PLAXIS 2D.

Keywords: Soil-plant-atmosphere interaction, Numerical analysis, Vegetation, Boundary conditions, Safety, Transpiration.