The Shear Strength of Root-Soil Composites in Different Growth Periods and Their Effects on Slope Stability

Vegetation slope protection plays an important role in improving the slope stability and protecting the environment. In this study, the mechanical properties of root-soil composites in different growth periods and their effects on slope stability were investigated. First, the shear strength of undisturbed root-soil composites associated with Cynodon dactylon (C.d), Magnolia multiflora (M.m) and grass and shrub mixture (G.s) were measured by large direct shear tests. Then, the effects of plant reinforcement in different growth periods on slope stability were analyzed using ABAQUS. The results show that the shear strength of the root-soil composites were significantly higher than that of the unreinforced soil. The root-soil composites met the Mohr-Coulomb criterion. The shear strength of the three root-soil composites increased first and then decreased during the vegetation growth period. The calculation results show that the factor of safety (FS) of the bare slope was 1.482. The FS values of the C.d, M.m, and G.s slopes were 1.601, 1.658 and 1.715, which increased by 8%, 11.9% and 15.7% compared to the bare soil slopes. Therefore, vegetation could significantly improve slope stability, especially the grass-shrub mixture model. This could provide a rational basis for designing and constructing plant slope protection.