Numerical Modelling Techniques for Stability Analysis of Slopes Reinforced with Shallow Roots

It is well recognised that plant vegetation and roots are capable of improving the shear strength of hillslopes by reinforcing soil shear resistance. Several key factors influencing the level of slope reinforcement include root geometry, orientation and strength. To assess the mechanical performance of vegetated slopes using numerical methods, root structures can be represented by beam and pile elements to mirror root behaviour. In contrast, root reinforcement can be modelled indirectly through a root cohesion factor, supplying additional strength to the soil surrounding the root zone. In this paper, correlations between these two numerical methods are presented, highlighting the applicability of each technique based on various root characteristics. Three types of root geometries are presented, consisting of a primary tap root, a secondary cohesion zone surrounding the main root and a root branching process. The results of the finite element analysis demonstrate the variation in the slope factor of safety for both methods, with a set of correlations between the two modelling approaches. A series of stability charts are presented for each method, quantifying the effects of root characteristics on slope reinforcement.