Contribution of Vegetation to Slope Stability: an Overview of Experimental Studies Carried Out on Different Types of Plants

Abstract

Vegetation has a great importance in erosion control and slope stabilisation, protecting and restraining the soil (at the surface) and increasing the strength and competence of the soil mass (at depth). To evaluate the effect of plant roots on soil shear strength, it is necessary to quantify the bio-technical and mechanical properties of the roots. This paper presents an overview of experimental and analytical studies developed by CESI S.p.A. in Italy and particularly focuses on the evaluation of root tensile strength related to four kinds of plants, commonly used for slope stabilisation in different Italian regions, and five kinds of perennial "gramineae" plants, imported from abroad. To evaluate the mechanical properties of the soil and then estimate the contribution of root tensile strength to slope stabilisation, some geotechnical tests were executed; the results were the inputs for a theoretical model that calculated the increase in shear strength (and therefore the increase in the factor of safety) due to plant roots.