Erosion Control and Slope Stabilization for Loose Sandy Soil by Using Vetiver Grass

Abstract

The root of vetiver grass has been proven to be effective to decrease erosion and increase slope stability for soil slope. The important role of vetiver grass roots in preventing water erosion and mass movement has been well recognized. However, quantitative researches that present the contribution of vetiver grass to erosion control and slope stability are limited, especially in the field study. This article presents the use of vetiver grass to slope erosion control and the role of vetiver root strength on slope stabilization for loose sandy soil slope which is located at north eastern part of Thailand. The erosion was measured in the field and then compared with the prediction from the Universal Soil Loss Equation (USLE) proposed by the USDA Agricultural Research Service. The soil layer and properties were investigated by borehole drilling and Kunzelstab penetration test, which shown the slope was built with loose sandy soil. The root tensile strength of vetivers was tested in the laboratory by using direct tension test. As the diameter of root increase, the shear strength of roots decreases as a function of exponential. The slope stability of slope stabilized with vetiver and without vetiver was analyzed using Infinite slope method. Slope with vetiver has significantly higher factor of safety when compared to slope in bare soil.