Coupling between finite and discrete element methods for the modelling of earth structures reinforced by geosynthetic

Due to the use of new technologies and innovative materials in civil engineering (reinforcement, recycled or natural materials), the design of geotechnical earth structures has become more complex, involving improvements to existing numerical models in order to consider the specific mechanical behaviours of each component in the structure. In this article, we focus on a new numerical model dedicated to earth structures reinforced with geosynthetic sheets, based on coupling the finite element method (FEM) and the discrete element method (DEM). The numerical model proposed takes the tensile and membrane behaviours of the geosynthetic into account by the FEM, and the interface friction between soil and geosynthetic and granular soil behaviour under large displacements by the DEM. The model used to describe the membrane and the tensile behaviours of the geosynthetic sheet is presented, and the basic assumptions of the discrete element method are then set out. Particular attention was paid to the description of the geometrical and micro-mechanical parameters of the discrete particle assemblies needed to reproduce realistic behaviour of granular soils. The aim of this article is to model the interaction between the geosynthetic sheet and the particles of soil, so the numerical coupling of FEM–DEM is described in detail; in particular, a specific contact law relating to the friction behaviour of the composite soil–geosynthetic is proposed. To show the interest of the numerical developments in modelling reinforced earth structures, an application is provided for embankments, reinforced at their base by a geosynthetic and built on areas subject to potential sinkholes. The numerical results of the FEM–DEM coupling are compared to those of true-scale instrumented experiments and of an analytical design method. The qualitative and quantitative comparisons of strains and tensile forces acting on the geosynthetic sheet make it possible to validate the numerical model suggested.