Research on model and test of reinforcing shear strength by vegetation roots in the Loess Plateau of northern China

In order to study the mechanism of root reinforcing soil in the Loess Plateau of northern China, the increasing effects of four dominant vegetation species, Pinus tabuliformis, Robinia pseudoacacia, Vitex negundo var. heterophylla and Syringa oblate, on soil shear strength were determined by WWM model and FBM model. In-situ shear tests were used to validate the theory models. Finally, root reinforcement was input to slope stability model, which was implemented using ABAQUS finite element numerical simulation software. Compared with in-situ direct tests, both of the considered models (WWM and FBM) overestimated the field results. Slope stability analysis based on in-situ direct tests showed that slope stability of four species was higher than the bare slope. Compared with the bare slope, safety factor of four species slopes increased by 4.38%, the maximum equivalent plastic strain of four species slopes decreased by 50.08%, the maximum horizontal displacement of four species slopes decreased by 40.83%, and the maximum vertical displacement of four species slopes decreased by 14.84% in average. Also, Vitex negundo var. heterophylla played the maximum role in stabilizing shallow soil layers in four species.The finding of present study provides useful information for estimating slope stability and quantifying root reinforcement by vegetation measures in the Loess Plateau of northern China.