Characterization of Vetiver Root Cohesion for Improvement in Stability of Tropical Hill Slopes

In this paper, bioengineering techniques like planting vegetation are presented to address issues related to soil erosion and rainfall- induced hill slope failures. Consolidated drained (CD) direct shear strength tests were performed on soil-root samples with different geometry and root area ratios (RAR) of vetiver roots. Results showed many-fold increases in peak shear strength of the root-soil matrix when compared with control soil samples. The friction angle changed minimally, while the apparent cohesion increased significantly with increasing root density. In addition, two simple mathematical models were developed to predict the increase in shear strength from rooted samples with respect to root area ratio as well as mobilized tensile strength per unit area of soil. In general, the shear strength of rooted soil increased with increasing RAR and mobilized tensile strength of roots. Current studies have endorsed the potential of vetiver grass in stabilizing tropical hill slopes.