Modeling Vegetation Growth and Decay Effects on Unsaturated Slope Stability Under Three Soil Cover Systems

ABSTRACT Soil cover systems with vegetation can be a potential green alternative for slope stabilization. This study aims to numerically investigate slope stability with three cover systems (one‐layer, two‐layer capillary barrier, and three‐layer with low permeability base) under different rainfall patterns, considering vegetation growth stages and slope angles. The rainfall event with a 100‐year return period (597 mm for 24 h) in wet regions is selected, with particular attention to advanced, delayed, and bimodal rainfall distributions. The results show that for bare soil slopes, the three‐layer cover system outperforms both one‐layer and two‐layer covers. The advanced rainfall pattern leads to the fastest decrease in the factor of safety (FOS), reaching a critical state 4.3 h earlier on average compared to other patterns. When a vegetated three‐layer cover is present on the slope, young vegetation (3 months) increases the FOS by 146%, while aged vegetation (19 months) maintains a 65% enhancement in FOS and prevents the potential shallow landslide through additional cohesion. For three‐layer cover slopes, when the slope angle increases from 30° to 40°, the FOS decreases by an average of 21%. However, the vegetated cover helps maintain the FOS consistently above 1.0. Among all the scenarios considered, the slope with a vegetated three‐layer cover demonstrates superior performance in preventing rainfall infiltration and improving slope stability. This study demonstrates that adopting a three‐layer cover in slope protection, especially with vegetation, provides an effective solution for rainfall‐induced slope failure mitigation.