Numerical analysis of stress–deformation response in reinforced unpaved road sections

Aggregate base course (ABC) layers of unpaved structures show significant plastic behavior under traffic load, including stress-dependent modulus and structural degradation. Geosynthetic reinforcement is commonly placed between the ABC and the subgrade to improve the performance of unpaved structures. Numerical analyses using the finite element program ABAQUS were conducted to investigate the performance of geogrid-reinforced aggregate over soft subgrade. Elasto-plastic constitutive models were used to model aggregate, subgrade and geogrid layer. Interaction between geogrid and aggregate was simulated as a shear-resistance interface. The reinforcement effects were seen in reducing surface deformation and improving vertical stress distribution on the subgrade layer. A parametric study indicated that ABC thickness and ABC/ subgrade modulus ratio greatly affect the contribution of the reinforcement. As the ABC thickness decreases, or as the ABC/subgrade modulus ratio decreases owing to deterioration or degradation of the ABC layer, the modeled sections show larger deformation, and the benefit due to geogrid inclusion becomes more apparent. Reinforcement with higher tensile modulus and better interface friction coefficient yielded better section performance in terms of less stress on the subgrade and surface deformation.