Experimental studies on geogrid efficiency against moderate to highly expansive subgrades

Moisture infiltration into expansive subgrades induces differential swell pressures, leading to surface heave, cracking, and deterioration of pavement serviceability. To replicate this behavior, extensive large-scale model experiments were conducted in a 1.5 m × 1.5 m × 1.1 m test tank, where differential heave was induced using a 250 mm diameter circular plate embedded within the existing subgrade. The model pavement section was comprised of an existing subgrade, overlain by a prepared subgrade made up of a 250 mm-thick compacted clayey sand (with CBR = 10% and 15%) and a 400 mm-thick base layer. Differential swell pressures corresponding to potential vertical rises (PVR) of subgrade equal to 12.5 mm and 25 mm were evaluated in unreinforced sections. To maximize performance, geosynthetic reinforcements—two polypropylene geogrids (PP 30 and PP 40) and two polyester geogrids (PET 100 and PET 200)—were placed at the interface between existing and prepared subgrades. A comparative analysis of unreinforced and reinforced pavements demonstrated that high-stiffness geogrids, PET 200 and PP 40, significantly enhanced performance. For instance, for the case of prepared subgrade with CBR = 10%, PET 200 and PP 40 reduced surface heave by up to 83% and 95%, vertical stress by over 61% and 77%, and increased swell pressure resilience by 50% and 54%, respectively.