Finite Element-Based Design and Analysis of Unpaved Roads over Difficult Subsoil: Sustainable Application of Geotextile Reinforcement to Attain Long-Term Performance

The performance and durability of an unpaved road depend on the strength of its individual components, i.e. aggregate layer and soil subgrade. For unpaved roads built over weak soil subgrades, the action of repetitive vehicular loading leads to permanent deformation in the form of rutting that gradually deteriorates the serviceability. In this study, initially, based on a coupled stress-deformation approach, a step-by-step design methodology of unreinforced unpaved road is developed by incorporating operational failure conditions. In order to avert the operational failures, geotextile layer introduced at the aggregate–subgrade interface is found to successfully reduce the stresses transferred to the subgrade. The usage of geotextile reinforcement is also found effective in reducing the required thickness of aggregate layer, as much as 50% in comparison to that required for unreinforced condition. Furthermore, finite element analysis of unpaved road under repetitive loading condition for different numbers of vehicle passes is conducted. When subjected to higher axle loads, rutting in unreinforced condition is observed to substantially increase with vehicle passes and even exceeding the serviceability criteria beyond certain cycles of loading. Geotextile layer at the aggregate–subgrade interface is found to successfully counteract the surface rutting. With the application of geotextiles of higher axial stiffness, not only rutting is conveniently controlled within the serviceability limit, the accumulation of rutting is also significantly arrested even for larger number of repetitive vehicular passes. Thus, through this FE-based analysis, the sustainable application of geotextile in unpaved road design and enhancing its performance under repetitive loading is successfully highlighted.