The Impact of Vegetation Roots on Shallow Stability of Expansive Soil Slope under Rainfall Conditions  
[PERSON]  
Key Laboratory of Health Intelligent Perception and Ecological Restoration of River and Lake, Ministry of Education, Hubei University of Technology, Wuhan 430068, China  
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[PERSON]  
Key Laboratory of Health Intelligent Perception and Ecological Restoration of River and Lake, Ministry of Education, Hubei University of Technology, Wuhan 430068, China  
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[PERSON]  
Key Laboratory of Health Intelligent Perception and Ecological Restoration of River and Lake, Ministry of Education, Hubei University of Technology, Wuhan 430068, China  
2  
[PERSON]  
Key Laboratory of Health Intelligent Perception and Ecological Restoration of River and Lake, Ministry of Education, Hubei University of Technology, Wuhan 430068, China  
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Footnote 2: email: {202  
Vegetation slope stabilization relies on the combined action of the above-ground stems and leaves of plants and their underground root systems to reinforce, anchor, and support the soil, thereby achieving the goal of soil reinforcement and slope stability [8; 9; 10]. Currently, research on vegetation for slope stabilization mainly focuses on investigating the influence of plant root systems on the shear strength of soil from a mechanical perspective. [PERSON] et al. [11] conducted experiments and found that during landslide processes, the uphill-growing root systems tend to fracture and fail first, while the downhill-growing root systems experience compression before being subjected to shear forces. [PERSON] et al. [12] experimentally verified that when the angle between the root system and the shear plane is acute, it increases the shear strength of the soil, with the maximum reinforcing effect achieved at an angle of 60\({}^{\circ}\). Conversely, when the angle is obtuse, it reduces the shear strength of the soil, with the minimum shear strength observed at an angle of 120\({}^{\circ}\), which may even result in a negative reinforcing effect, where the shear strength of the soil is lower than that of unreinforced soil. The axial force generated by plant root systems in the shear zone of a slope depends on the angle between the roots and the shear plane, as well as the position of the roots relative to the shear plane. The shear strength of the slope soil also needs to consider the influence of root diameter and depth [13; 14; 15]. [PERSON] et al. [16] conducted experiments to determine the relationship between root depth and additional cohesion, and used the strength reduction method to analyze the soil reinforcement effect of different vegetation root systems on common soils. [PERSON], [PERSON] et al. [17], considering both the intrinsic cohesion of the soil and the additional cohesion generated by the roots, conducted numerical simulations to study the slope stability in the presence of grass, shrubs, and trees. [PERSON], [PERSON] et al. [18] studied the impact of different rainfall intensities on the stability of slopes with various grass and shrub vegetation. [PERSON], [PERSON] et al. [19] conducted laboratory hydraulic erosion tests to investigate the characteristics of runoff, sediment yield, and sheet flow velocity on tailings dam slopes under four different plant conditions: goosegrass, vetiver, clover, and bare soil. They found that vetiver had the most significant reinforcing effect on the slope. [PERSON] et al. [20] quantified the impact of herbaceous plant root systems on slope stability from the perspective of safety factors, and found that there is an optimal angle at which root systems contribute to improved slope stability.  
Totally speaking, previous studies have rarely considered the influence of vegetation root reinforcement on slope stability of expansive soil under rainfall and moisture-induced swelling conditions. Then, this study focuses on investigating the effect of vegetation root reinforcement on the stability of expansive soil slopes under the conditions of moisture absorption and swelling.