Experimental Investigation of Root Tensile Strength for Slope Stabilization

Bioengineering approaches provide cost-effective ways to protect slopes against surface erosion and shallow mass movements. Indeed, vegetation is an excellent way to control slope erosion and instability of slopes. Plants play an active role both on the surface, protecting and holding soil particles, and at deeper layers, reducing pore pressure and increasing soil shear strength. The use of vegetation is particularly appropriate where soil conservation measures are needed. In the paper, a series of laboratory tests are described, together with the equipment used, to better understand plant root effects on soil shear strength and slope stability. Two species of Mediterranean plants, such as Asparagus acutifolius and Spartium junceum, were tested in the laboratory. More than 170 tensile tests have been performed on dry and saturated samples. In order to evaluate the effect of soil moisture, most several roots were also tested at different saturation ratios. Laboratory tests also included direct shear tests on root-reinforced and unreinforced samples. Comparison between reinforced and non-reinforced samples confirms the contribution of roots to improve the soil strength.