Full-scale evaluation of multi-axial geogrids in road applications

Abstract

The U.S. Army Engineer Research and Development Center (ERDC) constructed a full-scale unsurfaced test section to evaluate the performance of two prototype geogrids, referred to as NX950 and NX750, in road applications. The test section consisted of a 10-in.-thick crushed aggregate surface layer placed over a very weak 2 California Bearing Ratio (CBR) clay subgrade. Simulated truck traffic was applied using one of ERDC’s specially designed load carts outfitted with a single-axle dual wheel truck gear. Rutting performance and instrumentation response data were monitored at multiple traffic intervals. It was found that the prototype geogrids improved rutting performance when compared to the unstabilized test item, and that the test item containing NX950 had the best rutting performance. Further, instrumentation response data indicated that the geogrids reduced measured pressure and deflection near the surface of the subgrade layer. Pressure response data in the aggregate layer suggested that the geogrids redistributed applied pressure higher in the aggregate layer, effectively changing the measured stress profile with an increase in pavement depth.