An Apparatus for Direct Shear, Pullout, and Uniaxial Testing of Geogrids

In this paper, design and calibration procedures for a new large-scale testing apparatus for testing geosynthetic-soil systems are described. The multiple functionalities of the apparatus are implemented through the use of a single loading frame, driving mechanism, instrumentation, and data acquisition system for 3 distinct modes of loading: pullout, direct shear, and uniaxial loading. The design is similar to a conventional pullout device, but also includes key modifications and additional modules to adapt it for additional types of experiments. A series of pullout experiments were performed to validate the functionality of the apparatus and to examine the relationship between the geometry of the geogrid opening and its pullout resistance.