Mechanical Behavior of the Soil-Root System

The reinforcement of soil by vegetation depends on the biomechanics, length, and morphology of roots. Often, morphology and length are simplified in root reinforcement models by assuming symmetry above and below the shear plane. For many root systems, however, the presence of root collars and lateral rootlets could be greater beneath the shear plane. This is not taken into account in current models, so the current study derives a set of analytical equations to account for these effects and thereby provide a more realistic model of root reinforcement. To gain a better understanding of the mechanical behavior of the soil-root system, the resulting simulation was also compared with that of the data produced by the existing model in the literature (Waldron and Dakessian, 1981). This comparison shows that as root morphology and length are taken into account, the shear strength increment obtained with the new equations could reach values 1.4 times greater than that of previous models when the shear bond strength is small. In contrast, if the shear bond strength is greater, an increase in the root embedment length only produces a minor effect on the shear strength increment. In addition, we note that if the root system has the same constituents, the influence of roots on the shear strength increment decreases with an increase in the depth of the shear plane. The influence of rooted soils with smaller shear bond strength is found to be more significant than that of rooted soils with greater shear bond strength.