PLANE STRAIN COMPRESSION BEHAVIOUR OF GEOGRID-REINFORCED SAND AND ITS NUMERICAL ANALYSIS

 FANG-LE PENG , NOZOMU KOTAKE , FUMIO TATSUOKA , DAIKI HIRAKAWA and TADATSUGU TANAKA

 ABSTRACT: Plane strain compression tests were performed on large specimens that were either unreinforced or reinforced with 6 or 11 layers of geogrid, both 57.0 cm in height and 24.4 cm x 21 .4 cm in cross-section. It is shown that the effects of covering ratio for each grid layer is much more important than the total tensile stiffness of grid within the limits of the test conditions in this study. Numerical analysis of the test results by a plane strain non-linear elasto-plastic FEM was performed considering strain localisation as well as anisotropic stress-strain behaviour of sand and interface properties. The geogrid was modelled as a planar reinforcement. Not only the pre-peak stress-strain behaviour of the unreinforced and reinforced specimens, but also the peak strength, post-peak behaviour and dilatancy characteristics from the FEM analysis all compared well with those from the physical tests. The effects of reinforcement rigidity and covering ratio were also well simulated. The relationship between the reinforcement covering ratio in the physical tests and the equivalent interface friction angle for the FEM analysis that provides the same reinforcing effects is presented. The mechanism of tensile-reinforcing is analysed based on local stress paths within the reinforced sand obtained from the FEM analysis.

Key words: covering ratio, finite element method, geogrid, grid rigidity, interface friction angle, plane strain compression test, reinforced sand (IGC: D6/E13)