Experimental and FDM Study on Geogrid-Soil Interaction by Reformed Direct Shear Test Apparatus

This paper presents the effect of geogrid tensile strength by calculating the pullout resistance and the geogrid-soil interaction mechanism. In order to investigate this interface, a series of pullout tests have been conducted by a large scale reformed direct shear test apparatus in the both cohesive and granular soils. In numerical, the finite difference software FLAC3D has been carried out on experimental tests and the results are compared with findings from laboratory tests and to complete investigation results. The results show tensile strength of geogrids has an important role in the interface behavior. The effect of the soil type also is discussed. The obtained results show that the geogrids with low tensile strength have higher pullout resistance in the low normal stress on the surface, this effect reversed as the normal applied stress is increased. Numerical analysis only estimates the pullout strength with good agreement in the high normal stresses. Furthermore, it is found that the effective particle size of soil is close to the geogrid thickness by comparing two sands with different grain size.