Investigation of the Soil-Geosynthetic Interaction Using Direct Shear Testing and FEM Method

Abstract

Verification of the design of the reinforced earth retaining structures is usually based on the global and internal stability check. Beside the analytical solutions, numerical modelling can simulate the real behaviour of the structure including mutual interaction of the particular elements. Additionally, stress-strain relation is involved in the final verification together with the required stability of the system. Parameters such as reinforcement stiffness or interaction ability with the soil allow to calculate more realistic axial forces acting in the reinforcing elements. Analytical solutions don’t take into account the influence of the deformation of the soil mass on the overall and internal stability. Finite Element Method can describe both of these mechanisms which take place simultaneously. Estimation of the interaction parameters is crucial to determine the forces with sufficient accuracy, especially when 2nd limit state is critical for the structure design. The paper is aimed at the laboratory testing and numerical modelling of the interaction of the geosynthetic reinforcement and the soil during the sliding described by the interaction coefficient. A direct shear test was adopted to investigate the actual value of the interaction coefficient which is related to the certain displacement of the reinforcement in the soil. There is a recommendation not to use the interface element at the soil-reinforcement contact when the grid shaped reinforcing elements such as geogrids are used for the numerical simulations. This approach was approved by the study presented in this paper. Reinforcement with the grid structure and rigid joints provides higher level of interaction with the soil environment so reduction of the shear strength at this contact is unrealistic.