Bioengineering for Slope Stabilisation Using Plants: Hydrological and Mechanical Effects

Abstract

The negative impact of climate change calls for more sustainable and environmentally friendly techniques to be developed to improve the engineering performance of our civil infrastructures such as slopes in urban built environments. Soil bioengineering using plants and microorganisms is considered a low-cost and aesthetically pleasant solution for shallow slope stabilisation. Although extensive research has been conducted on the mechanical effects of root reinforcement in past decades, the hydrological effects of plants on shear strength and water permeability of vegetated soil slopes are not clear. This extended abstract presents an all-round, cross-disciplinary research programme consisting of indoor and field experiments, centrifuge testing and theoretical analysis to examine the plant hydrological effects on slope stability. It was revealed that some plant species native to southern China and Europe could preserve a credible amount of suction after heavy rainfall, which is positively correlated with the leaf area index (LAI), the root area index (RAI) and the ratio of root to shoot biomass. The total amount of water infiltration were found to be considerable higher in bare than those in soil covered by grass and tree. Plant-fungus interaction caused a significant increase in root tensile strength, hence potentially the mechanical reinforcement to soil. By developing novel artificial root systems in the centrifuge and deriving new theoretical closed-form stability equations, it was discovered that heart-shaped roots produced stronger stabilisation effects than either tap- or plate-shaped roots. This root architecture preserved higher suction (hence higher soil shear strength) and provided greater mechanical reinforcement effects due to multiple branching. These findings advance the fundamental understanding of plant-soil interaction and its influence on slope bioengineering applications.