Improvement of Long-Term Performance of Unpaved Road Constructed Over Marginalized Subsoil Using Geotextile Reinforcement

Conventional design of unpaved road is based on a two-dimensional plane strain approach with no residual deformation along the length of the road. However, in reality, the nature of vehicular load distribution is three dimensional. In this study, firstly, by considering the shape and dimension of equivalent wheel contact, analytical formulations are developed based on a limit equilibrium approach to determine the thickness of unpaved road resting on a generalized marginal subgrade. Further, to overcome the basic assumption of limit equilibrium approach that considers the unpaved road system to be rigid while neglecting any deformations, a Finite Element based study is conducted to incorporate the influence of deformations in improving the design of unpaved road. Based on a coupled stress-deformation approach, a step-by-step design methodology of unreinforced unpaved road is developed by duly incorporating the operational failure conditions under quasi-static loading condition. In order to avert the operational failures, application of geotextile layer at the aggregate-subgrade interface is found to successfully reduce the stresses transferred to the subgrade, thereby exhibiting its benefit in enhancing the long-term performance of unpaved roads. Furthermore, the influence of quasi-dynamic repetitive loading condition for different numbers of vehicle passes is also exhibited for both unreinforced and reinforced unpaved roads. It is observed that with increase of vehicle passes, substantial rutting is exhibited in the unreinforced condition that surpasses the serviceability criteria beyond certain cycles of loading. Inclusion of geotextile layer at the aggregate-subgrade interface is found to successfully counteract the surface rutting and vertical displacements. Through the FE-based analysis reported in the present study, the sustainable application of geotextile in unpaved road design and enhancing its long-term performance under repetitive loading is successfully highlighted.