Performance of Enhanced Problematic Soils in Roads Pavement Structure: Numerical Simulation and Laboratory Study

The deficiency of high-quality soils in Saudi Arabia’s southern and northern regions, as well as along the Arabian Gulf coasts, is regarded as one of the most common issues with the construction of roads. High compressibility, low shear strength, substantial volume change (particularly in Sabkha), and low bearing capacity are the most typical issues with these problematic soils. In this study, finite element simulations were performed using the Plaxis 3D software v20 to simulate the performance and study the critical responses (fatigue, rutting strains, and damage ratio) of an enhanced pavement structure with a geogrid reinforcement resting on the naturally problematic Sabkha subgrade. A normal asphalt concrete layer, a base layer of Sabkha soil stabilized with Foamed Sulfur Asphalt (FSA), and a sand dune subbase layer comprised the pavement structure. For each layer, the model’s input parameters were a mix of laboratory and literature data. The simulation was performed on a pavement structure without reinforcement and on another section enhanced with a geogrid positioned at various locations to determine the ideal placement for lowering the important responses such as fatigue, rutting stresses, and damage ratio. The nonlinear behavior of an FSA–Sabkha base, sand subbase layer, and Sabkha subgrade was simulated using the hardening soil model, whereas the asphaltic concrete layer and geogrid material were simulated using the linear elastic model. The findings of the simulations demonstrated that placing geogrid reinforcement at the top of the subgrade layer resulted in the greatest reduction in horizontal tensile (fatigue) and vertical compressive (rutting) strains, as well as vertical displacement (32.71%, 13.2%, and 14.2%, respectively). In addition, geogrid reinforcement greatly reduced the fatigue damage ratio (33% to 55%), although the reduction in the rutting damage ratio was slightly lower (14% to 30%). The simulation results were validated using a wheel tracking machine and it was clear that there is a reasonable agreement between the results.