Evaluation of plant growth and spacing effects on bioengineered slopes subjected to rainfall

Shallow landslides can be mitigated through the hydro-mechanical reinforcement provided by vegetation. Several critical parameters, such as plant spacing and plant age, play a significant role in influencing bioengineered slope stability facilitated by vegetation, the coupling of these effects on the stability of vegetated slope has been ignored. The objective of this study is to investigate the hydro-mechanical impact of vegetation growth and spacing on the stability of bioengineered slopes based on the predictions of a calibrated numerical model against field measurements. The impact of vegetation is investigated, with specific attention given to different plant spacing and growth stages, utilizing Schefflera arboricola. In the context of rainfall, it was observed that younger vegetation demonstrated more effective matric suction retention and recovery up to 25 kPa compared to the aged vegetation. Vegetation was revealed to substantially enhance the factor of safety up to 0.3 compared to the bare slope. Plant growth and reducing plant spacing increased the impact of root systems on both hydraulic and mechanical stability, primarily attributable to the influence of root cohesion rather than transpiration rates. The results revealed that the mechanical contribution to the factor of safety enhancement was raised from one-third to two-thirds because of the vegetation-induced cohesion within the growing rooted zone.