Abstract: The aim of this research is to explore the impact of rainfall on the stability of vegetated slope. The calculation formula for the wetting front depth of vegetated slope under rainfall infiltration was deduced using the improved Green-Ampt model with the hydraulic effect of vegetation and the runoff in saturated zone into consideration. The factor of safety of different potential sliding surfaces was calculated by using the limit equilibrium analysis method; thereafter, the stability of multi-layer vegetated unsaturated soil slope was analyzed and evaluated. Results indicate that the present infiltration model of multi-layer vegetated unsaturated soil slope which considers the hydraulic effect of vegetation and the runoff in saturated zone is practical, and could accurately evaluate the stability of vegetated slope under rainfall. The depth of wetting front increased with the expansion of rainfall duration, and the wetting front changed suddenly when the wetting front passed the boundary of soil layer. The increment of wetting front depth in root-silty sandy soil layer was smaller than that in silty sandy soil layer by 1.5%-11.8%. The anti-slip safety factor of the four potential sliding surfaces decreased with the increase of rainfall duration in the early stage of rainfall. The safety factor of vegetation-silty sand layer increased by 12.3%-35.5% compared with that of silty sand layer. Instability and damage were not easy to occur at the interface between root-soil layer and soil layer; but were prone to happen at the interface between soil layer and soil layer as the safety factor changed sharply.

Key words: vegetated slope, rainfall infiltration, unsaturated soil, wetting front, slope stability