Geogrid and Soil Displacement Observations During Pullout Using a Transparent Granular Soil

Current practice to quantify the load transfer capacity between soil and geosynthetic reinforcement materials in the anchorage zone of a wall, slope, or embankment is to carryout laboratory pullout tests. In a recent paper, the authors described a novel large pullout box with a transparent bottom. Geogrid specimens up to 2000 mm in length were embedded in a transparent fused quartz soil and the specimens subjected to constant rate-of-displacement in-air testing and in-soil pullout testing under a range of normal stress. Displacement–time histories over the entire area of each reinforcement specimen were measured using the digital image correlation (DIC) technique applied to sequential images captured by a row of cameras located directly below the test apparatus. Opaque particles were also mixed with the transparent soil particles so that horizontal displacement of the soil in the planes immediately above and below the geogrid specimens could be tracked. The difference in horizontal displacement response corresponds to the relative shear displacement between the soil and geogrid that is responsible for load transfer during pullout. These results demonstrate the utility of the experimental methodology using the transparent fused quartz material as a successful analog to a natural sand soil for the investigation of granular soil–geogrid interaction. The example data is a necessary precursor to the development of interface shear models for load transfer in the anchorage zone of geogrid reinforced soil structures.