A Simple Model for Estimating Shear Strength of Root-Soil Composite

The shear strength of soils is an important index to evaluate the stability of slopes reinforced with roots. This paper based on the common direct shear test results gives a quantitative analysis of the effect of roots on the stability of the slope. A simple model for the shear strength of root-soil composite was proposed based on the strength data for both the root and soil material. The influence of the root system was investigated with a new soil strength enhancement factor of β to represent the strengthening of shear strength. The influence of root diameter and root density on the shear strength of root-soil composite was discussed. Results show that within a certain range of root reinforced soils, the shear strength of the root-soil composite gradually increased at higher root densities. After reaching the peak value, the root density in the root soil had no significant effect on the shear strength. The small and densely distributed roots exhibit larger effect on the shear strength of root-soil system than that of the large and sparse roots. The results may provide guidance for stability estimating and engineering design of slopes.