Influence of Medium to Stiff Subgrades on the Performance of Geogrid-Reinforced Granular Layers

Abstract

Flexible pavement consists of subgrade, granular, and asphalt layers, and its performance depends on the quality of these layers. The present study investigates the influence of medium to stiff subgrade conditions on the geogrid-reinforced granular layers through a series of large-scale laboratory experiments. The pavement sections are built in a test tank of the size 1.5 m (length) × 1.5 m (width) × 1 m (height). The pavement sections consist of control and geogrid-reinforced sections having a 400 mm-thick granular layer overlaying a prepared medium to stiff subgrade conditions by varying the subgrade CBR from 5% to 12%. A biaxial polypropylene (PP) geogrid having an ultimate tensile strength of 30 kN/m in the machine and cross-machine directions was provided at the middle of the granular layers, i.e., at the interface of base and subbase layers. Further, the reinforcement effect was evaluated in terms of modulus improvement factor (MIF) for medium to stiff subgrade conditions. The MIF value ranges from 1.55 to 1.74 for stiff to medium subgrade conditions, respectively. Using these MIF values, an as-built pavement section was analyzed to demonstrate the reduction in granular and/or dense bituminous layer thicknesses and economic benefits.