Experimental investigation of pull-out resistance of uniaxial geogrids

The pullout performance of a locally manufactured geogrid is investigated by laboratory pullout test, performed with a modified large scale direct shear device which has been designed and constructed at Bogazici University, Due to the lack of a generally accepted standard method, all researchers have developed their own equipment. The differences in the testing procedures and equipment make the comparison of the test results difficult. But mainly the logic and effect of the various parameters on the pull out performance is the same in most of the papers presented so far. The test device presented here is a multi purpose large size direct shear device capable of conducting pull out tests. With 0.3 mX0.3mX0.3m sample box, the testing equipment is very practical. Uniaxial polypropylene geogrid and crushed rock was tested. The effects of displacement rate, confining pressure and specimen width on the pull out response have been investigated. The coefficient of interaction, which is required for the design of reinforced earth structures has been computed under different confining pressures. The results are interpreted and conclusions are presented. Comments for a better test setup are made.