Effectiveness of Vetiver Grass on Stabilizing Hill Slopes: A Numerical Approach
Md. Azijul Islam, Mohammad Shariful Islam, Tausif E Elahi
Abstract
Vetiver grass (Vetiveria zizanioides) is easily available in Bangladesh and widely known for its long fibrous roots which significantly increases shear strength of soil. This paper aims to numerically analyze the stability of hill slopes and effectiveness of vetiver for protection of slopes using PLAXIS 2D software. Soil samples were collected from four different hill slopes in Chittagong Hill Tracts (CHT) which were prone to landslides. Three soil samples were classified as sandy soil (SM, SC, and SM-SC) and another one was lean clay (CL). Results from numerical analysis showed that the factor of safety (FS) decreases with the increase in slope angle and for soft clay soil, slope fails at different slope angles. However, presence of vetiver grass on hill slopes increases FS by 2%–15% for sandy soils but for clay the increase in FS is insignificant because of deep seated base failure. Although vetiver alone cannot stabilize a hill slope but can protect the slopes from rain cut erosion which leads to failure. Additionally, analysis has been performed for different root zone depth considering the age of the plantation. Therefore, for sandy mild hill slopes, vegetation can be an effective and green solution for slope protection.