Cyclic swell–shrink behavior of geosynthetic-reinforced expansive subgrades

Expansive soils cause significant pavement distress due to seasonal swell–shrink behavior induced by moisture fluctuations. Unlike previous studies that focused on monotonic swelling, the present work evaluates long-term pavement response under repeated swell–shrink cycles simulating seasonal wetting–drying conditions. Accordingly, mitigation of swell–shrink deformation through modifications in pavement thickness and the use of geosynthetic reinforcement is investigated. Two pavement configurations with prepared subgrades of 250 mm and 500 mm thickness, placed above the existing subgrade, were evaluated under repeated uplift loading–unloading cycles applied through a circular plate over nine cycles to simulate differential swelling and shrinkage, inducing a maximum subgrade heave of 12.5 mm. A woven polyester geotextile (200 kN/m) and a biaxial polyester geogrid (200 kN/m) were installed at the interface between the existing subgrade and prepared subgrade layer. The results demonstrate that geosynthetic reinforcement enhances swell pressure resilience by restricting upward soil movement and redistributing swelling-induced stresses within the pavement system. The improvement was most pronounced in the thinner pavement section, where resilience increased by about 17%–18% during the first cycle and up to 20%–28% after repeated swell–shrink cycles.