Mitigating washboard effect: A study on geocells as soil reinforcement for unpaved roads

Washboard or corrugation is characterised by undulating patterns that emerge on unpaved roads as vehicles pass over. Soil properties, vehicle velocity, and mass influence these undulations. This study investigates the use of a cellular confinement system (geocells) placed at the road surface as a method to increase soil shear resistance. This approach aims to mitigate the formation of washboard undulations. A multi-pass experimental setup was employed to evaluate the reinforcement effect on the washboard phenomenon. The setup consists of a rotating wheel that traverses a sandy path, both with and without geocell reinforcement. Reinforced and non-reinforced results were compared under various scenarios, including wheel velocities and masses. Additionally, the effect of geocell confinement was compared with the effect of apparent cohesion using the theoretical model proposed by Ibagón et al. (2025). Findings showed that ripple formations are significantly reduced due to the geocell reinforcement. This suggests that geocells placed at the road surface may improve the durability and stability of unpaved roads under repeated vehicular loads.