GEOLAB - Transnational Access project SHEAR-GRID - Anisotropic Behaviour Geosynthetic Reinforcement

The main goal of the project is to obtain experimental data describing the anisotropic behaviour of the geosynthetic reinforcement (GR) in the environment of typical geosynthetic-reinforced pile-supported (GRPS) embankments conditions. Specific data are needed for the representative stress and strain conditions, taking the interaction of granular fill and GR into consideration. Data set were used to calibrate the numerical model. According to the available published literature, shear tests of geosynthetics interacting with the fill soil under the specific deviator stress conditions of an GRPS embankment have not been performed elsewhere so far. Shear tests in the plane of the GR itself and the GR interacting with the fill soil were planned to be performed by using the Large-scale Triaxial Apparatus at the Slovenian National Building and Civil Engineering Institute (ZAG). Some modifications of the apparatus were needed, therefore. Preparations for conducting the experimental tests start earlier and has been carried out remotely. During the two weeks of testing, three experiments were conducted to measure the force and displacements of the geogrid - (1) empty device for calibration, (2) specimen with only GR installed, and (3) specimen with GR and fill soil installed. Some variations of the latter two tests were performed according to different types of GR fixation. In all cases, loading was performed in simple shear mode in the GR plane. The results of the shear in-plane tests and the image of the deformed GR was used to calibrate the numerical model. This enables the determination of the required characteristics. Properties such as the shear modulus in the plane of the geosynthetic as well as of the compound material will later be used to analyse the behaviour of the GRPS embankment, using constitutive models of anisotropic elasticity, considering the actual characteristics of the GR. Project aims to determine the GR’s anisotropic shear strength characteristics while considering the interaction with soil. For this purpose, complex shear tests were conducted that are unique on a global scale. The aim of the project is to better understand the behaviour of the geosynthetic reinforcement within the GRPS structure and its interaction with fill material. The obtained results, combined with numerical analyses, will allow the determination of characteristics needed to calibrate advanced constitutive models. This would enable including anisotropic GR properties in numerical analysis of the behaviour of the GR above rigid inclusions. Models of anisotropic hyper-elasticity in the modelling of geosynthetic reinforcement and their verification require not only the results of uniaxial tensile tests in the principal directions of geosynthetics but also shear tests in plane. The necessary characteristics have not been determined for polymer GRs so far, which proves the innovative character of the proposed experiment.