Experimental Investigation of Geosynthetic-Stabilized Unpaved Road Performance under Varying Swelling Distribution Areas

Abstract

Moisture infiltration into expansive subgrades results in differential heave that varies in spatial extent, adversely impacting pavement surface integrity and riding quality. To investigate this phenomenon, a large-scale experimental setup (1.5 m × 1.5 m test tank) was developed to simulate differential subgrade heave by applying uplift force at the subgrade level through a circular diameter steel plate. While previous studies utilized 250-mm-diameter plate to simulate localized swelling, the present study incorporates a 300-mm-diameter plate to better capture the effects of different swelling extents, as can be influenced by moisture fluctuations at the subgrade level. The pavement model consisted of an existing subgrade overlain by a 250 mm-thick prepared subgrade layer with a California Bearing Ratio (CBR) of 5%, followed by a 400 mm-thick unbound granular base layer. To improve the pavement performance, biaxial geosynthetic reinforcements with tensile strengths of 100 kN/m (PET 100) and 200 kN/m (PET 200) were placed at the interface between the existing and prepared subgrades. The results indicate that, for the 250 mm plate, PET 100 and PET 200 reduced surface heave by 73% and 77%, respectively, under a swell pressure of 225 kPa. In the case of the 300 mm plate, the corresponding reductions increased to 80% and 85% at a swell pressure of 185 kPa. These findings demonstrate that the spatial extent of subgrade swelling plays a critical role in governing pavement deformation and confirm the effectiveness of geogrid reinforcement in mitigating surface heave.