Plant roots mechanically enhance the strength of soil and improve slope stability through anchoring.Given the popularization of ecological slope-protection technology,a quantitative study of how roots help to anchor soil is highly pertinent.The object of the present study is thus to investigate how roots and soil combine to affect the mechanical properties of the root-soil interface.Toward this end,pullout experiments of cedar roots of different diameters in soils of different density were conducted.The experimental results show that the maximum pullout force increases significantly with increasing root diameter,but only slightly increases with increasing soil density,which indicates that the root diameter has a greater impact on the maximum pullout force than soil density.Next,based on studies of fiber-reinforced composites,a root-soil pull-out model was proposed to study the evolution of shear stress on root-soil interface.This approach ensures that the model accurately reflects the dynamic stress distribution evolution at the root-soil interface and can calculate the pullout process of embedded root from soil.The accuracy of the model is verified by comparing the calculated results with experimental results.Finally,how soil density and root diameter affect the anchoring force was analyzed.The results indicate that the maximum anchoring force increases linearly with increasing root diameter,but nonlinearly with increasing soil density until reaching a fixed value.These results show that the root soil pull-out model has significant practical value in slope protection.