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DONATILI TOPRAK ŞEV VE INTERACTION OF MARGINAL FILLS AND GEOGRIDS FOR REINFORCED SOIL WALLS AND SLOPES

In design of geosynthetic reinforced soil walls and slopes, most of the design guidelines require use of granular material as backfill soil. There is lack of clarity in the design and analysis for the reinforcement of predominantly granular material which has high fines content (marginal material). In this study, large direct shear tests (width 300 mm x length 300 mm x height 300 mm) will be conducted to investigate soil – geogrid interaction mechanism in direct shear mode for granular soils having different fines contents (0 to 40%). Clean granular soil samples (GW,GP; 0% fines content) and clayey gravel (GC) samples having 12%, 20%, 30% and 40% fines contents; plasticity indexes of 5% and 15% will be tested. Tests will be conducted under normal stress values of 20 kPa to 150 kPa. Three different types of geogrids will be used in experiments. Two of them will be biaxial geogrids, ParagridR and ParadrainR (having inplace drainage channels through its straps), third one will be extruded uniaxial geogrid having different mechanical properties than the other two. Consequently, geogrid characteristics such as the effect of strength properties, aperture size and pattern, production method, ability to provide in-place drainage will be evaluated. Bond coefficients and interface shear properties of geogrid reinforced marginal backfills will be determined for different samples which is necessary for numerical simulation. Recommendations to be used in design will bedeveloped.