Assessing Benefits of Using Geogrids in Pavements Founded on Problematic Soils

Abstract

Geogrids are becoming a popular alternative for soil reinforcement in highway pavement construction to achieve improved performance in regions with soft problematic soils or with a reduction in aggregate layer thickness to reduce construction costs. To examine the potential benefits of geogrids for soil improvement, measurement of permanent deformation using triaxial tests is used in practice. However, soil subgrade improvement in a reinforced pavement system is achieved by lateral distribution of vertical stresses at the reinforcing layer, through the tensile properties of the geogrid material. Therefore, it is desirable to conduct large-scale testing to more accurately monitor the behavior of soil when geogrid is present. The current study seeks to verify the behavior of geogrid reinforced pavement systems through large-scale wheel tests performed with problematic subgrade soils found in North Georgia. The large scale specimen was prepared in a 6 feet long × 6 feet wide × 2 feet deep metal box and consisted of 12 in. of aggregate base overlying 12 in. of subgrade soil. Pressure sensors were installed near the bottom of the aggregate base layer and near the top and bottom of the subgrade layer to monitor stress distributions within the pavement system. This paper presents preliminary results showing vertical stress variations obtained experimentally in aggregate base and subgrade soils under large-scale simulated traffic tire loading. The development of a bench scale system to complement the large scale loading system and allow for microstructure evolution studies is also described.