Experimental and FDM study on the effect of geogrid tensile strength on pullout resistance

This paper presents the effect of geogrid tensile strength by calculating pullout resistance and geogrid-soil interaction mechanism. In order to investigate this interface, a series of pullout tests have been conducted by large scale reformed direct shear test apparatus in both cohesive and granular soils. In numerical, 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 interface behavior. Effect of soil type also is discussed. The obtained results show that geogrids with low tensile strength have higher pullout resistance in 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 high normal stress. Obviously, in high normal stresses soils, compacted and passive resistance in front of transverse elements increases. Results also indicate that the failure mechanism of gear pullout is same as foundation bearing capacity, in clays punching shear failure occur on geogrid-soil interaction resistance and sands show hardening behavior. Furthermore, the effective particle size of soil is found to be a little more than the thickness of gear by comparing two sands with different grain size.