Effects of vegetation on hydraulic responses and slope deformation under wetting–drying cycles

Large flume model tests were conducted to investigate the effects of vegetation on water infiltration and slope deformation under wetting–drying cycles. In total, two flume model tests were carried out, one was planted with Schefflera heptaphylla, and the other bare slope severed as a reference. Plant characteristics, volumetric water content, matric suction, and surface runoff were well documented. Simultaneously, slope deformation during rainfall was analyzed by Particle Image Velocimetry (PIV) technology. The experimental results showed that the growth rate of plant height increased as light intensity increased. At the initial stages, suctions in the shallow soil layers (i.e. 50 mm) of the vegetated slope were smaller than that of the bare slope. However, the suction in the vegetated slope increased as light intensity increased, particularly in the shallow layer (i.e. 150 mm), where it was about 10 kPa larger than that of the bare slope. In addition, vegetation improved the rainfall infiltration rate, which increased with the number of wetting–drying cycles. Under the same condition, the cumulative rainfall infiltration rate of the vegetated slope was approximately twice that of the bare slope. While, the horizontal and vertical deformation rates of the vegetated slope were lower than those of bare slope, respectively. This indicates that vegetation effectively mitigates slope deformation during extreme rainfall and enhances slope stability.