Modélisation avancée par eléments discrets du renforcement des sols par les racines végétales

Abstract

This thesis focuses on advanced modeling of soil reinforcement by plant roots using the Discrete Element Method (DEM). The primary objective is to quantify and understand the impact of roots on soil shear strength, a critical parameter for soil reinforcement and slope stability. The work is structured around two main components. First, a numerical model of the direct shear test using the Casagrande shear box was developed. This model was subsequently employed to the shear strength of root-free sands. Particular attention was given to the effect of preloading on the shear strength of sand and its deformation during shearing. The results indicated that preloading influences the internal friction angle and apparent cohesion. Second, soil reinforcement by plant roots was investigated by modeling root-soil interactions in a similar framework. Through 2D simulations, the effect of various parameters, such as root density, distribution, and orientation, on soil shear strength was analyzed. The results demonstrated that roots significantly enhance shear strength, especially at large deformations. Additionally, the presence of roots increases dilatancy during shearing. Visualization of the sample during shearing revealed that roots contribute to the widening of the shear band. Root orientation also affects shear strength, it has been shown that roots are more effective when oriented in the direction in which they are subjected to tension during shearing. Particular attention was paid to the effects of the proximity of roots to the walls of the shear box. It has been shown that this proximity influences force distribution and soil deformation and can therefore have a significant impact on the results of numerical and physical shear tests on rooted samples.