International Research Journal of Education and Technology

The durability and economic efficiency of flexible pavement structures are critically challenged by the prevalence of weak subgrade soils in many regions of India, leading to frequent failures such as rutting, potholes, and excessive maintenance burdens. This research systematically investigates the incorporation of biaxial geogrids as reinforcement in flexible pavement systems, aiming to both strengthen subgrade soils and optimize construction costs. The methodology encompasses a series of laboratory tests performed on locally available subgrade soils, including grain size distribution, Atterberg limits, Proctor compaction, and California Bearing Ratio (CBR) evaluations—with and without geogrid layers placed at variable depths. A large-scale test tank was developed to simulate pavement sections, enabling cyclic loading and direct measurement of settlements. The study also employs the Layer Coefficient Ratio (LCR), Modulus Improvement Factor (MIF), and Traffic Benefit Ratio (TBR) to quantify the impact of geogrid inclusion. Results indicate marked increases in subgrade CBR (from ~8 up to >13) with geogrid presence, particularly when installed at optimal positions, and a TBR of 2.7, representing a 170% improvement in load cycle endurance at 10mm design settlement. Subsequent mechanistic empirical design using IRC:37-2018 and supplementary IITPAVE analyses demonstrate the ability to safely reduce base and sub-base layer thicknesses while meeting rutting and fatigue criteria. Economic analysis confirms significant material savings, reduced maintenance interventions, environmental benefits, and overall life cycle cost reductions estimated at 10–25%. The findings establish geogrid-reinforced flexible pavements as an effective technical and economic strategy for sustainable, high-performance road infrastructure, particularly in regions with problematic subgrades. Recommendations for practice and further research conclude the paper.

Keywords

Biaxial geogrid, flexible pavement, geosynthetics, soil reinforcement, CBR, layer coefficient ratio, modulus improvement factor, traffic benefit ratio, cost reduction, sustainable pavements, IRC:37-2018, subgrade improvement.