Abstract:Plants are sophisticated and intelligent natural construction materials

which can be used for enhancing the stability of shallow soil slopes and minimizing surface erosion.It is evident that the use of plants can be low-cost

sustainable (almost maintenance free) and environmentally friendly.Vegetation used in shallow slope protection has a wide application prospect in southwest China

so it is important to understand the mechanism of vegetation in slope engineering stabilization.The stabilized mechanism is influenced by a lots of factors

in which the synergistic effect of root-soil mass is the focus of current research.Due to the different inclination of roots

the shear strength of root-soil system becomes complicated.Direct and triaxial shear test were performed on soil sample with different inclinations of artificial roots to investigate the reinforcement effect.Test results indicated that the peak shear strength and the residual shear strength of roots reinforced soil were obviously larger than soil without roots

and followed the laws of τp pure<τp90°<τp45°<τp135°.In the direct shear test

the largest shear strength was detected and strain hardening was observed when the inclination of roots was 135°

and strain softening tendency of soil samples with roots was controlled at different levels.When the inclination of roots was 135°

the root reinforcement effect was the most obvious and the residual strength was also the largest.It was indicated that proper inclination of roots may enhance the synergistic effect between roots and soil

then the strength of root-soil mass could be improved.The ductile deformation characteristics of root soil system could help improve the safety of the slope.This research results is valuable for vegetated slope engineering practice.