The banks in the middle and lower reaches of the Tarim River in China are weak in erosion resistance and prone to collapse. Vegetation, as a natural reinforcement material, can effectively improve slope stability and curb soil erosion. In March and July 2023, a field survey was conducted on the types and distribution characteristics of vegetation along both banks of a certain section in the lower reaches of the Tarim River. Taking COMSOL Multiphysics as the finite element numerical simulation platform, we investigated the variation law of bank slope stability in the middle and lower reaches of the Tarim River under different root morphologies, considering changes in transpiration time, rainfall, and water level under the action of hydro-mechanical reinforcement. The findings showed that vegetation transpiration has a significant effect on soil pore water pressure. Given the same transpiration rate, shorter root systems produced greater pore water pressure. For equal root lengths, the pore water pressures generated by roots in exponential and triangular morphologies were significantly greater than those generated by roots in uniformly distributed and parabolic morphologies. The water absorption capacity of the root system increased with transpiration rate. After 7 d of transpiration, the maximum safety factor of the bank slope reinforced by exponential roots was 1.568, which was a 9.88% improvement over that of the bare slope. After 24 h of rainfall, the effect of vegetation transpiration on soil pore water pressure weakened rapidly; the pore water pressure of the surface soil generated by transpiration from vegetation with different root morphologies was concentrated near –10.00 kPa. After rainfall, the displacement of the exponential root reinforced slope was minimized to 0.137 m. The effect of transpiration-induced changes in substrate suction on slope stability was negligible during the rainfall period. Compared with that of the bare slope, the displacements of bank slopes reinforced by root systems significantly increased. The maximum displacement occurred when the water level changed by 1.5 m/d; the displacement of the bare slope was 0.554 m, whereas the displacements of bank slopes reinforced by roots in different morphologies were 0.260–0.273 m. The impact of vegetation transpiration on the safety factor of riverbanks under sudden water level drops was relatively minor, but it can enhance the stability of riverbanks to a certain extent. Among these, riverbanks reinforced by roots in triangular and exponential morphologies exhibited superior stability compared with those reinforced by uniformly distributed or parabolic root systems. The findings offer a theoretical basis and practical guidance for designing vegetation slope protection in the middle and lower reaches of the Tarim River.
Nianfeng et al. (Sun,) studied this question.