In-Aggregate Testing of Unitized and Woven Geogrids for Base Reinforcement Applications

This paper presents the results of a preliminary study that examined and compared the in-aggregate performance of unitized and woven geogrids using laboratory tests. The geogrids had comparable rib tensile strength and aperture sizes. However, their other mechanical properties including junction strength, out-of-plane flexural stiffness and rib bending stiffness were significantly different. Geogrids junction and rib strengths were determined using in-isolation tests. Pullout and plate load tests were subsequently performed to examine their response in a drainable (open-graded) aggregate material. Results of the study indicated that significantly different junction strength values between the geogrids did not result in significantly different pullout or load-settlement response under serviceability conditions. In addition, the difference in junction strength was unlikely the cause of the observed difference in their plate load performance. However, unitized geogrids exhibited greater in-aggregate strength properties at higher strains that would represent construction stage conditions. Further study is underway to develop a better understanding of the implications of these laboratory results in the selection of geogrids for base reinforcement applications.