Experimental Investigation of Root Tensile Strength for Slope Stabilization

  • P. P. CapilleriEmail author
  • M. Cuomo
  • E. Motta
  • M. Todaro
Original Paper


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.


Soil stabilization Strength and testing of materials Slope erosion control 

List of Symbols


Angle between the root and the normal to the sliding surface


Roots area


Considered area for stability analysis


Root area in the class i


Angle of the sliding surface to the horizontal




Root diameter into the stable soil


Increment in strength due to the root


Friction angle


Safety factor with root contribution


Safety factor without root contribution


Soil unit weight


Height of the water table


Height of the sliding slope


Horizontal seismic coefficient


Vertical seismic coefficient


Average length of the root apparatus into the stable zone


Number of classes of roots having a same diameter


Number of roots with a same diameter


Value of distributed load


Tensile strength of the root

σR i

Average root tensile strength in the class i


Strength increment due to roots


Soil shear strength


Average value of the ultimate shear stress at the interface along the root into the stable zone



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Copyright information

© Indian Geotechnical Society 2019

Authors and Affiliations

  1. 1.Department of Civil and Industrial EngineeringUniversity of PisaPisaItaly
  2. 2.Department of Civil Engineering and ArchitectureUniversity of CataniaCataniaItaly

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