Laboratory cyclic plate load tests are commonly used in the assessment of geosynthetic performance in pavement applications due to the repeatability of testing results and the smaller required testing areas than traditional Accelerated Pavement Testing facilities. While the objective of traditional plate load testing procedure is to closely replicate traffic conditions, the reality is that rolling wheel loads produce different stresses in pavement layers than traditional cyclic plate load tests. This two-fold study investigates the differences between the stress response of subgrade soil from a rolling wheel load (replicating rolling traffic conditions) and a unidirectional dynamic load (replicating traditional plate load test procedures) in order to obtain a more realistic stress response of pavement layers from rolling wheel traffic. Ultimately, results show that the testing specimens that experienced rolling wheel loading had an average of 17% higher pressure measurements in the top of the subgrade than vertically loaded (unidirectional dynamic load) specimens. The second segment of this study is used in conjunction with the first to analyze aggregate base material behavior when using a geosynthetic for reinforcement. The study aimed to determine the difference in the post-trafficked strength and stiffness of pavement foundation. A Dynamic Cone Penetrometer and Light Weight Deflectometer were utilized to determine material changes from this trafficking and revealed that all specimens that included a geosynthetic had a higher base stiffness and strength while the specimen with geotextile and geogrid in combination created the highest stiffness and strength after large-scale rolling wheel trafficking.

In a geosynthetic-reinforced pavement system, the load-bearing capacity of subgrade soil is improved by the lateral distribution of vertical stresses at the reinforcing layer. Under small-scale triaxial testing, the tensile properties of the geosynthetic are difficult to measure. Therefore, it is desirable to conduct large-scale testing to accurately monitor the behavior of geosynthetic-reinforced pavement foundations when subjected to rolling-wheel loadings. This study investigates the behavior of geosynthetic-reinforced pavement foundation systems through large-scale rolling-wheel tests performed with problematic subgrade soils found in north Georgia. Sixteen large-scale specimens were constructed of which twelve were reinforced with geosynthetic. Subgrade soils were compacted either at their optimum moisture content or at a higher than optimum moisture content to produce different California Bearing Ratios during specimen preparation. Both an extruded biaxial geogrid and woven geotextile were placed at various locations to investigate the optimal placement locations for different subgrade conditions. Pressure sensors were installed near the bottom of the aggregate base layer and near the top of the subgrade layer to monitor the variations in vertical stress within the pavement system under rolling-wheel load. Further, light weight deflectometer measurements were collected post-test to determine the effect of the geosynthetic on pavement foundation stiffness. The vertical pressure at the bottom of the aggregate base and top of subgrade decreased on average approximately 15.3% and 18.8%, respectively. The results indicate which type of geosynthetic and placement location provides the greatest reduction of pressure for each of the given subgrade conditions.

Geogrid reinforcement is an economically viable alternative to achieve improved performance in highway pavement construction in regions with soft problematic subgrade soils. To examine the potential benefits of using geogrids in pavement foundations, measurement of permanent deformation using laboratory triaxial tests is typical practice. However, since the performance improvement of pavement foundation systems is achieved by distribution of vertical stresses at the reinforcing layer through the tensile properties of the geogrid material, it is desirable to conduct large-scale testing to more accurately monitor the behavior of the geogrid-reinforced aggregate and soil system. This article describes the development of laboratory large-scale and bench-scale pavement testing systems to evaluate the behavior of geogrid-reinforced pavement systems through wheel tests performed with problematic subgrade soils found in North Georgia. The large-scale test specimens are prepared in a 1.8 (6 ft) by 1.8 (6 ft) by 0.6 m (2 ft) metal box and consist of 305 mm (12 in.) of unbound aggregate base (UAB) overlying 305 mm (12 in.) of subgrade soil. Geogrid is placed at the interface between the subgrade soil and UAB layer. Pressure sensors are installed near the bottom of the UAB layer and near the top and bottom of the subgrade layer to monitor stress distributions within the pavement foundation system. The bench-scale system, which measures 914 (36 in.) by 203 (8 in.) by 152 mm (6 in.) is also described. This system is advantageous because not only does it expedite rapid testing but also allows for relative micro- and macroscale comparisons of aggregate-geogrid behavior. This article presents test results showing vertical stress variations obtained experimentally in the UAB and subgrade soils under simulated traffic tire loading. The two systems are shown to be effective in establishing the influence of geogrid reinforcement in pavement systems.

Geosynthetics are becoming a popular alternative for soil improvement in highway construction to achieve enhanced performance in regions with soft problematic soils or to reduce aggregate base layer thickness to decrease construction costs. Subgrade soil improvement in a geosynthetic-reinforced pavement system is achieved by lateral distribution of vertical stresses at the reinforcing layer, through the tensile properties of the geosynthetic material, which is hard to measure with small-scale triaxial tests. Therefore, it is desirable to conduct large-scale testing to more accurately monitor the behavior of aggregate and soils under rolling wheel loadings when geosynthetic is present. The current study seeks to verify the behavior of geosynthetic-reinforced pavement systems through large-scale and bench-scale rolling wheel tests performed with problematic subgrade soils found in North Georgia. Large-scale and bench-scale specimens that mimic an aggregate base–geosynthetics–subgrade system were constructed at different subgrade soil conditions. Subgrades were constructed at a moisture content to produce a low California bearing ratio (CBR) or at optimum moisture content (OMC) during specimen preparation. Both an extruded biaxial geogrid and woven geotextile were placed at various locations in the aggregate base layer to investigate the optimal placement location for the different subgrade conditions. Pressure sensors were installed near the bottom of the aggregate base layer and near the top of the subgrade layer to monitor the vertical stress variations within the pavement system during trafficking. For large-scale testing, light …

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.