Modelling the effects of vegetation on stability of slopes

Abstract

It is well understood that vegetation influences slope stability in two ways: through hydrological effects and mechanical effects. Hydrological effects involve the removal of soil water by evapotranspiration through vegetation, which lead to an increase in soil suction or a reduction in pore-water pressure, hence, an increase in the soil shear strength. The shear strength of the soil is also increased through the mechanical effects of the plant root matrix system. The density of the roots within the soil mass and the root tensile strength contribute to the ability of the soils to resist shear stress. The effects of soil suction and root reinforcement has been quantified as an increase in apparent soil cohesion. This paper investigates the effects of vegetation on the stability of slopes using the finite element method. Two key vegetation-dependent parameters have been incorporated in the finite element slope stability analysis, namely, apparent root cohesion (cR) and depth of root zone (hR). Parametric studies were performed to assess the sensitivity of the stability of a slope to the variation in the key vegetation and soil parameters. Results show that vegetation plays an important role in stabilising shallow-seated failure of slopes, and significantly affects stability.