Investigation on the shear properties of soil reinforced by vegetation roots

Abstract

This study presents the brief result of direct shear tests on the soils reinforced by vegetations. In this study, two series of direct shear tests are conducted in the field to investigate the effects of vegetation roots on the soil shear properties. The results show that the presence of vegetation roots contributes to the shear strength of soils resulting in increases mainly in cohesion and less in friction angle for increasing the stability of slope. The increase proportion of cohesion (Ic) in the soils with different roots is 40-90%, meanwhile the increase proportion of friction angle (iΦ) is only 10-30% that give an impact to the soil shear strength increasing up to 36-74%. Particularly, the influence of root tensile on the increase proportion of shear properties of the soils is confirmed in this study. The soil with Vetiver has a root area ratio (RAR) greater 5 times than the Lemongrass soil, but the increase proportion is not much and even smaller than the Mombasa and Guinea soils. Moreover, the comparison of the increase proportion in soil shear properties is also discussed for other vegetation roots.