In-situ evaluation of geosynthetic-reinforced pavement on variable subgrade conditions

A 225 m-long instrumented pavement was constructed on a local road in Australia to assess the performance of flexible pavements reinforced with polymeric geogrid, polymeric geocomposite, and fibreglass geocomposite over a soft subgrade. The lane was divided into 15 sections with variations in base thickness, reinforcement type, and placement. In-situ tests, including the Dynamic Cone Penetrometer (DCP) and Falling Weight Deflectometer (FWD), were conducted during and immediately after construction in December 2019. Long-term performance data, including static Plate Load Tests (PLTs) and a second round of FWD tests in June 2022, were incorporated to evaluate reinforcement effectiveness over time. Performance was assessed using vertical surface displacement from PLTs and normalized maximum deflection from FWD tests, while accounting for subgrade spatial variability. Results show that sections reinforced with two geosynthetic layers exhibited up to 29.5% lower deflections compared with unreinforced sections. Although Sections S7 and S8 had similar reinforcement configurations, S8, constructed over a weaker subgrade, mobilized reinforcement more effectively and showed greater reductions in deflection. Overall, the results demonstrate that PLTs and FWD tests are effective for revealing subgrade spatial variability and for assessing and comparing the performance of reinforced and unreinforced pavement sections, highlighting the importance of long-term monitoring.