Modeling root reinforcement using a root-failure Weibull survival function

摘要

Root networks contribute to slope stability through complex interactions withsoil that include mechanical compression and tension. Due to the spatialheterogeneity of root distribution and the dynamics of root turnover, thequantification of root reinforcement on steep slopes is challenging andconsequently the calculation of slope stability also. Although considerableprogress has been made, some important aspects of root mechanics remainneglected. In this study we address specifically the role of root-strengthvariability on the mechanical behavior of a root bundle. Many factorscontribute to the variability of root mechanical properties even within asingle class of diameter. This work presents a new approach for quantifyingroot reinforcement that considers the variability of mechanical properties ofeach root diameter class. Using the data of laboratory tensile tests andfield pullout tests, we calibrate the parameters of the Weibull survivalfunction to implement the variability of root strength in a numerical modelfor the calculation of root reinforcement (RBMw). The results show that, forboth laboratory and field data sets, the parameters of the Weibulldistribution may be considered constant with the exponent equal to 2 and thenormalized failure displacement equal to 1. Moreover, the results show thatthe variability of root strength in each root diameter class has a majorinfluence on the behavior of a root bundle with important implications whenconsidering different approaches in slope stability calculation. Sensitivityanalysis shows that the calibration of the equations of the tensile force,the elasticity of the roots, and the root distribution are the most importantsteps. The new model allows the characterization of root reinforcement interms of maximum pullout force, stiffness, and energy. Moreover, itsimplifies the implementation of root reinforcement in slope stabilitymodels. The realistic quantification of root reinforcement for tensile, shearand compression behavior allows for the consideration of the stabilizationeffects of root networks on steep slopes and the influence that this has onthe triggering of shallow landslides.